Productive performance of large white Yorkshire sows managed on diet containing fermented soybean meal

Introduction

The livestock sector is a major contributor to India's economy, with pig farming emerging as one of the most profitable enterprises due to its rapid turnover, suitability for small and marginal farmers. It also has significant potential to generate sustainable income and economic opportunities for new entrepreneurs and individuals from less privileged backgrounds. According to the 20th Livestock Census (2019) [35] , India possesses a pig population of 9.06 million, accounting for about 1.69% of the total livestock population. In contrast to the national decline in pig numbers, the North-Eastern region (NER) of India recorded a notable increase in pig population, reflecting the socio-cultural and economic importance of pig rearing in the region. Pork is widely consumed in the NER, particularly among tribal communities, where pig farming forms an integral part of their culture and lifestyle for ages. (Kumaresan et al., (Cottrell et al., 2015; Li et al., 2021) [13] . Fermented soybean meal (FSBM) has gained Significant attention in recent years for its potential benefits in animal nutrition. Historically, soybean meal had been a vital source of plant-based protein in livestock feed, especially for pigs, however, its utilization is limited by anti-nutritional factors such as trypsin inhibitors and lectins, which reduce nutrient digestibility and growth performance. (Lambo et al., 2023: Grant, 1989) [20] . Fermentation of soybean meal through microbial processes has been shown to reduce anti-nutritional factors while enhancing nutrient digestibility and feed efficiency in pigs (Czech et al., 2021; Yuan et al., 2017) [14,66] . Overall, microbial fermentation is an effective approach for reducing anti-nutritional components in feed ingredients (Chi et al., 2016) [9] . In view of the above findings, the current experiment was conducted to study the productive performance of Large White Yorkshire Sows managed on diet containing fermented soybean meal.

Materials and methods

Location and period of study The study was carried out in the Piggery Unit of the Instructional Livestock Farm Complex, Department of Livestock Production and Management, College of Veterinary Sciences & Animal Husbandry, Central Agricultural University, Selesih, Aizawl, Mizoram, India. The study was conducted for six months from December, 2023 to May, 2024.

Experimental design and dietary treatment groups

For the purpose of the study, a total of 18 gestating Large White Yorkshire Sows (1st to 4th parity) were utilized. All the sows were identified individually and divided into three groups of 6 sows in each group, viz., Group 1 (Control), Group 2 (T1) and Group 3 (T2), in such a way that the effect of sire and parity is nullified. All the experimental animals were fed with standard rations prepared as per NRC (2012) [41] specification by using conventional feed ingredients. Sows of Group1 were fed the basal diet containing unfermented soybean meal (conventional SBM) and served as the control group. Feed containing fermented soybean meal (FSBM) @ 50% and 100% were fed to the sows of Group 2 (T1) and Group 3 (T2), respectively. All the sow were fed at the restricted feed (3.25 kg/sow/day) required during the gestation period (day 80 of gestation till Farrowing) and the 1st week of the lactation (0-7 days). Adlibitum feed was fed from the 2nd week of lactation till weaning (8-28 days) and thereafter, 4-5 kg of feed per day per sow depending upon the body condition from weaning till the next heat, with free access to water throughout the study period. Gestating sows were housed in individual concrete stalls (0.55 × 2.25 m) and shifted to farrowing pens 1 week before parturition, where they remained in farrowing crates (1.8 × 2.25 m) with slatted flooring, guard rails, and heated creep areas until weaning at 28 days, after which they were shifted to dry and pregnant sow pen. Routine management practices, including teeth clipping, navel cord cutting, iron injections and deworming were carried out as per standard procedure, and sick animals were treated promptly. The experimental study was conducted for a period of approximately 70days.

Preparations of fermented soybean meal

Fermentation of soybean meal was done as per standard procedure described by Lambo et al. (2024) [30] with some modifications. For fermentation, distilled water was added to the grounded soybean (SBM) at a rate of 700 ml/kg and cooked at 65-121 ˚C for 30 minutes by using a pressure cooker. The cooked SBM was naturally cooled down to room temperature. After that, cooked soybean meal was simultaneously inoculated with Saccharomyces cerevisiae (Sacye® forte, Brihas Animal Health, 1x1020 CFU/gm) with the dose rate of 1gm per kg of soybean meal and Aspergillus oryzae MTCC 3107 (HiMedia) (3 x 107 CFU/gm) in the proportion of 1 gm per kg of soybean meal. Thereafter, SBM was kept in an incubator at 37 ˚C for 24 hours for fermentation. After being incubated for 24 hours, fermented soybean meal (FSBM) was mixed with Lactobacillus acidophilus (Inlife group, 5x109 CFU/capsule) with the dose rate of 1 capsule per kg of soybean meal which was again incubated at 37 ˚C for 96 hours in a tightly packed container to maintain the anaerobic condition. After the completion of fermentation, fermented soybean meal was dried in a hot air oven at 50˚C-60˚C for 72 hours, up to 10% moisture content. After cooling, the pH of fermented soybean was measured (4.5 pH was achieved) with a pH meter by following a procedure described by Abdel et al. (2023) [1] . Finally, fermented soybean meal was packed and stored in the fridge for further use. The nutrient composition of SBM and FSBM used in the experiment are shown in Procurement of feed ingredients and preparation of compounded feed for experimental animals The feed ingredients such as maize, soyabean meal, groundnut cake (GNC), wheat bran, Di-calcium phosphate (DCP), soya oil, DL methionine, L-lysine, mineral mixture and salt were procured from Aizawl, Mizoram. They were then estimated for proximate principle analysis by following standard procedure (AOAC, 2000) [6] in the Department of Animal Nutrition, C.V.SC & A.H, CAU, Selesih, Aizawl. Standard rations for the animals were then prepared as per NRC (2012) [41] Parameter recorded were as follows Average Daily Feed Intake (ADFI) of sow Feed consumption of sows was recorded on a daily basis during the entire study period. ADFI was determined by subtracting the residual feed from the feed provided after making corrections for the dry matter content of the feed. Body Condition Score (BCS) of sow Body Condition Score (BCS) of the sow was assessed with finger and hand pressure on the sow's body, particularly areas where the only tissue between the skin and bones is fat tissue, which include the ribs, backbone, H" bone and pin bones on the 80 days of gestation, day of farrowing, and day of weaning. A condition score from 1 to 5 was assigned to each sow based on the ease or difficulty of detecting bones at various pressure points as per the BCS system by Coffey et al. (1999) [12] . Assessment of Sow Body Condition as mentioned by Coffey et al. (1999) [12] is presented table 4.

Gestation period of sow

Gestation period of each sow was recorded during the study period.

Number of born dead piglets and mummified fetuses

Number of born-dead and mummified were observed and recorded at the time of farrowing.

Litter size and litter weight at birth and weaning

Litter size and litter weight at birth and weaning were observed and recorded at the time of farrowing and weaning.

Body weights of piglets at weekly interval

The body weight of the piglets was taken in the morning by using an electronic platform weighing balance (capacity 30 kg) from birth to the date of weaning (day 28) at a weekly interval (at day 0, 7, 14, 21, and 28).

Average daily gain (adg) of the piglets till weaning

The average daily gain (ADG in grams) was calculated by subtracting the initial body weight from the final body weight of a particular period. The average daily gain was calculated by using the following formula: -----------------------------------X [11] . This procedure was done on a weekly basis during lactation to estimate the week-wise milk yield of sow. Body weight of dead piglets during the experiment period was taken into account to determine the milk yield of sow.

Weaning to Service Interval (WSI) of Sow

After weaning of the piglets, sows were observed for onset of post weaning estrus with the help of a boar observing behavioral signs of estrus, standing heat and weaning to estrus intervals (WSI) were recorded accordingly.

Mortality of the piglets was recorded from day of farrowing till 4th week postpartum. Animals that died during the experiment were sent for postmortem examination in the Department of Veterinary Pathology, College of Veterinary Sciences & Animal Husbandry, Central Agricultural University, Selesih, Aizawl, Mizoram, and causes of mortality were recorded.

Mortality rates were calculated by using the following formula

Data collected from the study were subjected to statistical analysis using IBM SPSS version-27.0 software and Chi-square test (X2) for meaningful and accurate comparison and interpretation (Snedecor and Cochran, 1994) [50] .

Result and discussion

The mean (± SE) Average daily feed intake (ADFI) (in kg) of LWY sow during gestation (from 80 days of gestation to day of farrowing) at weekly interval are presented in Table 5. Statistical analysis of the data revealed non-significant (p>0.05) difference in ADFI during different weeks of late gestation among the groups. The feed intake of sows during gestation is essential for maintaining their health and ensuring proper fetal development. Sow should neither be too fatty nor too lean during gestation. Restricted feeding of sows is helpful to prevent excessive weight gain during gestation, which reduces complications during farrowing and lactation including occurrence of mastitis, metritis and agalactia syndrome (Whittemore and Kyriazakis, 2006) [62] . This approach helps in maintaining an optimal body condition score (BCS), improves fertility, and supports better milk production, Ampode et al., (2023) [3] , all of which contribute to the sow's overall health and reproductive performance. As 2/3 of the fetal development takes place during last trimester of gestation; higher level of feed intake during last month of pregnancy resulted in high birth weight of piglets (Reddy D.V., 2001) [44] . Gestating sow feeding schedule of 2.25-2.50 kg during day 0 to 27, 2.50-2.75 kg during day 28 to 83, 3.00-3.35 kg during day 84 to112, 2kg during day 113 to last day of gestation and Nil or 1kg feed on the day of farrowing is proven to be beneficial (Anon, 2005) [4] .The overall feed intake of sows (on restricted feed) in the present study is in line with the study of Shang et al. (2024) [48] , who reported that sows (Large White × Landrace) in both the fermented Soybean hulls (FSH) treatment and control group had a feed intake (restricted) of 3.0 kg/day during late gestation. During the present study, sows were managed on restricted diet as per the feeding schedule of Anon, (2005) [4] with minor variation depending upon the body conditions of the sows. The overall ADFI from the 1st to the 4th week (weaning) of lactation for Control, Treatment 1 (T1) and Treatment 2 (T2) were 5.03±0.45, 5.19±0.17 and 5.34±0.29, respectively. Statistical analysis revealed no significant differences in ADFI during the 1st, 2nd, 3rd and 4th weeks of lactation, as well as in the overall ADFI from the 1st to 4th week of lactation among the groups. However, numerical increase in ADFI during the 2nd, 3rd and 4th weeks was observed in sows reared under the T1 and T2 groups (fed diets containing FSBM) compared to those in the control group. During lactation, sows' feed intake is gradually increased to meet their rising nutritional needs, which Enhances milk yield and the weight of piglets at weaning. It is often suggested that sows should be fed based on the size of their litter. Sow with an average litter size of 11 at birth should be provided with 1-2 kg of feed on the first day of lactation and the amount should be gradually increased by 0.5 kg daily until the target feed of 7kg (Target feed: 1.5 + (0.5 x litter size). Thereafter, 7kg per day during the rest of lactation (Anon, 2005) [4] . Whittemore and Kyriazakis, (2006) [62] state that sows have a reduced appetite on the first day after farrowing due to the stress of delivery and the physiological changes associated with lactation. At this stage, they usually consume 1-2 kg of feed, but feed intake can increase by approximately 1 kg per day, reaching 6-7 kg by the end of the first week, as sows require more energy for milk production and recovery. To help sows gradually adjust to the increasing nutritional demands of lactation, it is recommended to raise feed intake by 0.5 kg daily. A reduction in feed intake may occur after 21 days of lactation as milk yield decreases. This gradual adjustment ensures optimal energy and nutrient supply for milk production and the sow's recovery from the physiological stress associated with pregnancy, farrowing, and early lactation. The lack of significant differences in ADFI observed in the present among the groups during the 1st, 2nd, 3rd, and 4th weeks of lactation in LWY sows was consistent with the findings of Huang et al. (2020) [22] , who observed no significant difference (p=0.98) in ADFI of sows (Landrace × Yorkshire) throughout lactation between the treatment groups (fed a diet containing 5% fermented soybean fiber (FSF diet)) and the control group (fed a diet without supplementation of FSF). Similar findings were observed by Jurgens et al. (1997) [24] , where supplementation with dry yeast (Saccharomyces cerevisiae) during gestation and lactation did not improve sows' feed intake. Lambo et al. (2024) [30] mentioned that feeding FSBM helps to maintain the gut health in sows. However, the numerical increase in sows' ADFI observed in the present study during the 2nd, 3rd and 4th weeks aligns with the observations of Tan et al.

(2020) [53] and Wu et al. (2021) [63] . Tan et al. (2020) [53] found that adding 10 g/kg yeast extract to LWY sows' diets increased their feed intake during lactation. Wu et al. (2021) [63] noted that the average daily feed intake of lactating (Yorkshire × Landrace) sows fed diets containing 100 and 200 mg/kg SI (Soybean Isoflavone) and APS (Astragalus Polysaccharide Mixture) in the form of powder (GC100 and GC200, respectively) was significantly higher (p<0.05) than that of the control group (GC). Although no significant differences in ADFI were observed among the groups during the 1st to 4th weeks of lactation, the inclusion of FSBM might have increased feed palatability, digestibility, improve nutrient utilization and absorption due to enhanced gut morphology, alleviation of gut disorders, and overall improvement in sow health which might have helped in higher milk production in sows, as reflected in improved growth rate of suckling piglets. [65] stated that BCS serves as an essential management tool for producers to improve production efficiency, monitor pig health, and assess their nutritional status and is measured by subjective (manual body scoring) and objective methods (Sow caliper, Flank to flank & Renco Lean Meater). Anupam et al. (2019) reported that BCS scores range from 1 to 5, with BCS 1 indicating extreme emaciation and BCS 5 representing severe obesity. A BCS of 3 reflects optimal body condition, where reproductive performance in sows is maximized. According to their study, the BCS at farrowing should range from 3.0 to 4.0 for optimal reproductive performance and decrease to 2.5 to 3.5 at weaning as sows mobilize energy reserves, leading to weight loss during lactation. This weight loss may also be influenced by litter size, with larger litters requiring greater energy expenditure. Furthermore, BCS in sows is directly influenced by body weight gain and loss, as it reflects the sow's nutritional status and overall health. During pregnancy, the weight gain of sow is closely related to feed intake. It is generally recommended that sows should gain between 25.0 and 30.0 kg during gestation (Lavery et al., 2018) [31] , receiving 3.25 kg/day of feed from the 86th to the 112th day of gestation and 2 kg/day from the 113th to the 114th day of gestation (NRC, 2012) [41] to support maternal and conceptus growth. Whittemore and Kyriazakis, (2006) [62] reported that under ad libitum conditions, the daily feed intakes of lactating sows may range from 3 to 12 kg, but most sows rarely exceed 6.5 kg during lactation, and a lower feed intake can lead to a loss of up to 20 kg (i.e., approximately 10% of their BW) of maternal body weight. Excessive weight loss leads to a body condition score below the optimal 2.5 at weaning, which results in reduced conception rates, longer weaning-tooestrus intervals, and a higher risk of shoulder lesions during nursing. The BCS of sows at day 80of gestation recorded the present study is in agreement with the findings of Maes et al.

(2004) [37] , who reported that sows in three herds (A: 400 sows, B: 300 sows, and C: 250 sows) had different body condition scores (BCS) at 80 days of gestation: 2.96, 3.36, and 3.32, respectively. Herds A and C were fed the same commercial meal twice a day, while herd B was fed pellets once a day. Present observation of the body condition score (BCS) at the day of farrowing and weaning were also in accordance with the observation of Shen et al. (2011) [49] and Huang et al. (2020) [22] . Shen et al. (2011) [49] observed that supplementation of sows with Saccharomyces cerevisiae fermentation products throughout the whole gestation period did not affect gestational back-fat thickness change. They mentioned that body weight and back-fat thickness (BFT) of sows during gestation and lactation were similar between two treatments (sows fed a basal diet with 12.0 g of fermentation product [(SCFP-Saccharomyces cerevisiae fermentation product) /day for 5 days before breeding through gestation and 15.0 g of fermentation product /day through lactation) and control sows fed a corn-soybean meal basal diet without supplementation)]. Huang et al. (2020) [22] reported that inclusion of fermented soybean fiber (FSF) in gestation and lactation diet of sow (Landrace × Yorkshire) had no effect on body weight or back-fat thickness gain on day 109 of gestation and at the day of farrowing and at weaning (p>0.05).In contrast to the present findings, Wang et al.

(2018) [60] reported that the back-fat loss of sows (Yorkshire × Landrace) fed 15% Fermented Mixed Feed (FMF-40% corn, 40% soybean meal, and 20% wheat bran) was significantly lower (p<0.05) than that of sows fed the control diet. The back-fat was measured on the days of parturition and weaning. The present findings showed that feeding fermented soybean meal (FSBM) to sows minimized the significant loss of body condition at farrowing and weaning.

Although no significant differences were found between the treatment and control groups, sows from T1 and T2 had a higher numerical body condition score compared to those from Control. This improvement might be due to the beneficial effects of FSBM, which might reduce antinutritional factors in the diet, provides Beneficial bioactive peptides and digestive enzymes, probiotics and antioxidants, leading to higher feed intake of sows during lactation, promoting a positive energy balance, thereby, reducing body condition loss and contributes to improved milk production. The difference in sow body condition particularly body weight and back-fat thickness, observed by the earlier studies compared to the present findings may be due to the variations in breed, parity, lactation feed intake and the management practices. [47] , who reported that the average gestation length of sows (Large White Yorkshire × Landrace) on commercial farm was approximately 115 days, with individual lengths ranging from 105 to 125 days. They noted that about 70% of farrowing events occurred between 114 and 116 days, indicating minimal variability in gestation length among sows. Although gestation length varied among individual sows, it did not change with parity. Sows were more likely to have a gestation length similar to that of their previous gestation at any parity. They also stated that the high repeatability of gestation length also indication of sow-to-sow variation had a considerable influence on the total gestation length variation. The similarity in gestation periods observed in the present study might be associated with the comparable litter sizes, as no significant variations (p>0.05) in litter size were found between the treatment and control groups. According to Imboonta et al. (2012) [23] , sows with a lower total number of piglets born had longer gestation periods compared to those with larger litters. They mentioned that sows with smaller litters gestated 0.24 days longer (p<0.05) than those with larger litters. They further noted that sows with litters of 12 or more had a shorter gestation length compared to sows with smaller litters. This could be attributed to the larger placentas of sows with larger litters producing higher levels of estrogen, which initiates parturition, contributes to shorter gestation lengths when present in greater quantities (Dziuk, 1991) [17] . [62] reported that embryo and fetal death are often associated to irregular returns to estrus, and is usually related to disease invasions. Infective agents, such as mycotoxins, reproductive tract infections, parvovirus, Aujeszky's disease, and Leptospira can cause uterine infections, vulval discharges resulting in embryo Loss, giving irregular return to estrus (often between 23 and 40 days), fetal death, mummified fetuses, reduced litter size, stillbirths, and abortions. Furthermore, Pasteurella, E. coli, and Corynebacterium may enter through the vagina and disrupt the reproductive tract, causing painful urination, cystitis, and abortion. Lefebvre, (2015) [32] observed that fetal mummification may occur after 35-40 days of pregnancy, once the skeleton has formed, with 70% of cases linked to management, nutrition, and environmental factors and 30% caused by infections. Factors like parity, litter size, uterine capacity, environmental temperature, mycotoxins are associated with mummification (Van de et al., 2003) [58] . Borges et al. (2005) [8] found that larger litters (over 12 piglets) had a 14.5-fold higher chance of mummification compared to smaller litters (p<0.05). This finding may be Associated with a failure of the uterus to maintain a favorable environment for fetal growth and survival. According to Wu et al. (1998) [64] , uterine length in sows with and without mummified fetuses is equivalent. However, sows with mummified fetuses tend to have larger litters (more fetuses), suggesting that uterine space is more likely to influence fetal death and eventually mummification, particularly in the last trimester of gestation, when the fetal growth rate increases significantly. Present findings of number of born dead and mummified fetus were in accordance with the observation of Huang et al. (2020) [22] , who reported that inclusion of a fermented soybean fiber diet (FSF diet) in the pregnant sows (Landrace × Yorkshire) diet had no significant effect in the number of stillbirths for the FSF group versus the control (stillbirth; 1.8 for FSF vs. 2.0 for control). Similar results were reported by Tan et al. (2020) [53] in dietary supplementation with different amounts of yeast extract (0, 2.5, 5, and 10 g/kg YE treatments) in multiparous LWY sows from day 85 of gestation to day 21 of lactation, observing no significant difference (p>0.05) in the number of stillborn and mummified piglets. In contrast to the present results, Song et al. (2017) [51] mentioned that supplementation of sows (LWY × Landrace) with 4% SSDDGS (Saccharomyces cerevisiae refermented sorghum dried distiller's grains with solubles) significantly reduced the litter stillbirth rate (p<0.05) as compared to the control. Fermented soybean enhances reproductive performance in sows through improved nutrient availability, phytoestrogenic activity and support for uterine health (Ren et al., 2001) [46] . The link between estrogen, uterine glycogen, and reproductive success is well established, supporting the role of FSBM in reducing stillbirths and improving outcomes. However, the absence of a significant difference in the number of stillborn or mummified fetuses between the fermented soybean treatment group and the control group observed in the present study could be due to several influencing factors. These might include the treatment duration, the quantity of fermented soybean used, or other environmental and genetic variables that affect fetal development. To ascertain the present findings, further study on inclusion of fermented soybean in sow diet with more number of sows might be helpful. [45] , Wang et al. (2016) [61] , Wang et al.

(2018) [60] and Luo et al. (2021) [36] . Rehfeldt et al. (2007) [45] found that supplementation of soybean flavonoid to the sow's (Landrace) diet had no effect on the litter size, litter birth weight, and piglet birth weight. Wang et al. (2016) [61] reported that the inclusion of fermented soybean meal (FSBM) in the gestation diet of sows (Landrace × Yorkshire) had no effect (p>0.05) on litter size, litter weight, average piglet weight at birth. Wang et al. (2018) [60] , reported that supplementation of 7.5% fermented mixed feed [(FMFfermentation of 40% corn, 40% soybean meal (SBM), and 20% wheat bran with B. subtilis (3 × 108 cfu/g), E. faecium (108 cfu/g)] in sow (Landrace × Yorkshire) diet does not show any tendency to improve the performance of sows and their progeny. Luo et al. (2021) [36] reported that replacing SM with FSBM (fermented with Aspergillus oryzae and Lactobacillus reuteri) in the sow (Landrace) diet had no effect on the litter size, alive litter size, litter weight at birth and the birth weight of piglet (p>0.05). In contrary to the present findings, Ren et al. (2001) [46] reported that the feeding soy isoflavones daidzein to late pregnant sows could enhance the birth weight of male piglets. They mentioned that ingestion of daidzein by the sow could alter the expression of estrogen receptor beta (ERβ) in the newborn piglets which influences fetal growth associated with higher Type 1 insulin-like growth factor receptor (IGF-1R) gene expression in skeletal muscle. Cho et al. (2011) [10] reported that fermentation of soybean increased the content of soybean isoflavones (SIFs) as the form of aglycones, which comprises different form such as genistein and daidzein. Shen et al. (2011) [49] mentioned that sows treated with Saccharomyces cerevisiae fermentation product (SCFP) throughout gestation and lactation period tended to have increased litter weaning weight compared with sows in the control group. Zhang et al.

(2020) [67] , also observed that the litter size (total born) and numbers of piglets born alive were significantly (p<0.01) greater in the sows (Landrace x Yorkshire) fed diet supplemented with B. subtilis PB6 (BS) group than those in the control (without B. subtilis PB6) group. Wang et al.

(2018) [60] observed that feeding 15% FMF to sows increased (p<0.05) the weaning weight and weight gain of litters. Luo et al. (2021) [36] observed heavier litter weight on the 14th day after birth in 4% FSBM and 6% FSBM (fermented with Aspergillus oryzae and Lactobacillus reuteri) supplemented in Landrace sows than that of the control (p<0.05). Furthermore, the weight of litter was heavier in the 4% FSBM group than that in the control (p<0.05) on the 21st day after birth. Their findings suggest that FSBM supplementation can improve litter weight at different stages of growth. Nonsignificant differences in litter size and litter weight at birth (0 day), 1st week, 2nd week, 3rd week and 4th week observed in the present study between treatment (T1 and T2) and Control group could be due to difference in quality of soybean, percent of FSBM in diet, environmental conditions or the duration of the supplementation.

16, respectively. Statistical analysis revealed nonsignificant differences in average body weight at birth (day 0,) day7, day 14 and day 21 among the groups (P≥0.05). However, significant (P≤0.05)) increased average body weight (ABW) of piglets were found at day 28 in the treatment 2 (T2) group as compared to the control (C) and treatment 1 (T1) groups. The results of the average body weight (ABW) of piglets supplemented with fermented soybean observed in the present study were in accordance with the findings of Luo et al. (2021) [36] , they reported that replacing soybean meal (SM) with fermented soybean meal (FSBM), fermented with Aspergillus oryzae and Lactobacillus reuteri, in the diet of sows (Landrace breed) had no significant (p>0.05) difference in the ABW of piglets at birth (0 day). However, it significantly improved the ABW of piglets on the day of weaning (21 days), compared to the control group (p<0.05). In their research, the average ABW of piglets at birth was recorded as 1.57±0.11, 1.58±0.88, 1.54±0.07, and 1.55±0.11 kg for control, 2%, 4%, and 6% FSBM-supplemented groups, respectively. They recorded ABW at weaning (day 21) as 4.57±0.30, 5.53±0.29, 6.03±0.28, and 5.65±0.34 kg for the same groups, respectively. Wang et al. (2018) [60] reported that supplementing sows (Yorkshire × Landrace) with 7.5% and 15% Fermented Mixed Feed (FMF) consisting of 40% corn, 40% soybean meal (SBM), and 20% wheat bran did not affect body weight gain of suckling piglets in the treatment groups compared to the control, but they recorded significantly increased (p<0.05) individual piglet weight at weaning (day 21). They mentioned the average body weight of piglets at birth 1.27 kg, 1.26 kg, and 1.34 kg, and at weaning (day 21) 5.93 kg, 5.94 kg, and 6.45 kg for the control, 7.5% FMF, and 15% FMF groups, respectively. Data of ABW in the present study under different groups revels that fermentation might have increases the aglycone form of SIFs in FSBM, which in turn reduced oxidative stress during gestation and lactation, thereby enhancing the milk production resulting in better growth of nursing piglets of sows fed FSBM as compared to the control group. In sow, milk production started to decline after 3rd week of lactation (Whittemore and Kyriazakis, 2006) [62] which was also observed in the present study (Table no.13). However, incorporation of FSBM might have helped to sustain the milk production even in 4th week of lactation, which might cause significantly higher body weight in nursing piglet on day 28 (T2) as compared to piglets under control group. The mean (± SE) ADG (g) of LWY piglets from 1st to 4th week of age and for the overall ADG are presented in Table 12. The mean (± SE) ADG (grams) of LWY piglets at 1st week, 2nd week, 3rd week and 4th week for Control, Treatment 1 (T1) and Treatment 2 (T2) in the present study were 134.89± 8. Statistical analysis showed non-significant differences in ADG at different ages among the groups. However, significant (p<0.05) increase in overall ADG from the 1st to the 4th week was observed in the treatment groups (T1 and T2) compared to the control group. The present observation of ADG in LWY piglets from the 1st to the 4th week of lactation resembles the findings of Luo et al. (2021) [36] who reported that supplementing the diet of Landrace sows with 4% FSBM significantly increased the average daily gain of piglets after birth compared to the sows in the control group. However, contradictory results were reported by Demečková et al. (2002) [15] and Wang et al. (2016) [61] . Demečková et al. (2002) [15] reported that feeding sows Lactobacillus spp.fermented liquid feed improved sow ADFI but had no effect on piglet growth performance. Wang et al. (2016) [61] revealed that the daily gain of piglets did not differ significantly (p>0.05) between the group receiving the FSBM (fermented with Bacillus subtilis, Hansenulaanomala and Lactobacillus casei) supplement during gestation and the first 28 days of lactation and the control group. Data of the average daily gain (g) of LWY piglets revealed that FSBM might have enhance nutrient digestibility, increases the bioavailability of amino acids and essential nutrients, supports gut health through the production of short-chain fatty acids and increases the contents of soybean isoflavone aglycones with high efficacy of biotransformation, which in turn helped to reduced oxidative stress in sows and increased feed intake (Table no. 6). Decreased oxidative stress in both gestation and lactating sow and increase feed intake during lactation as observed in the present study (numerically increased) might enhanced the milk production and contribute to improvement in the average daily gain of suckling piglets under the treatment groups as compared to the control group. Statistical analysis revealed non-significant difference in the estimated milk yield (litre) of LWY sow during lactation period among the groups. However, the treatment groups receiving fermented soybean meal exhibited a numerical increase in estimated milk yield compared to the control group. Milk yield in sows is essential for piglet growth and survival, directly influencing weaning weight and litter performance. It is impacted by factors such as litter size, feed intake, and the sow's body condition. According to Whittemore and Kyriazakis, (2006) [62] , larger litters stimulate higher milk yield, while adequate feed intake supports both milk production and the sow's recovery from the physiological stresses of pregnancy, farrowing, and early lactation. They mentioned that a sow nursing six piglets produces 8.5 kg of milk daily, with each piglet consuming 1.4 kg; for eight piglets, the yield is 10.4 kg, with 1.3 kg per piglet; with ten piglets, the yield is 12 kg, and intake per piglet is 1.2 kg; and for twelve piglets, the yield reaches 13.2 kg, with 1.1 kg per piglet. Milk production peaks at around 3 weeks post-partum, with piglets suckling hourly during the first 4 weeks. Afterward, suckling frequency decreases as piglets begin to rely less on milk. Lactation typically ends by 10-12 weeks, as piglets become nutritionally independent. Noblet and Etienne, (1986) [40] reported that milk production increased significantly (p<0.01) as the lactation period was maximum at day 21 in sows fed with high energy diet and at day 17 in the sows fed with low energy diet. Kakati et al.( 2019) [25] reported that the average weekly milk production in LWY sows as 46.51 liters, with peak production occurring at the third week of lactation, a pattern also observed in the present study (Table 13).The numerical increase in estimated milk yield of LWY sows from the 1st to the 4th week, as well as the overall improvement in milk yield observed among the treatment groups, can likely be attributed to the higher average daily feed intake (ADFI) in the groups compared to the control (Table no. 6).This increased feed intake may be a result of the beneficial effects of fermented soybean, which could enhance nutrient availability, improve palatability, and support better metabolic efficiency that contributes to greater milk production of sow during the lactation period. However, the results of the present study contradict the observations made by Wang et al. (2018) [60] , who reported that supplementing the diets of Yorkshire × Landrace sows with 15% Fermented Mixed Feed (FMF), consisting of 40% corn, 40% soybean meal, and 20% wheat bran, significantly (p<0.05) enhanced milk yield and increased the IgA content in the milk compared to the control group. Luo et al. (2021) [36] also observed that replacing soybean meal with fermented soybean meal (FSBM), fermented using Aspergillus oryzae and Lactobacillus reuteri, in Landrace Sow diets reduced oxidative stress, enhanced colostrum composition (protein, fat, lactose, total solids, SNF, and immunoglobulins) and improved offspring performance. They noted a significant (p<0.05) increase in protein and total solids in the colostrum. Wu et al. (2021) [63] also mentioned that that the inclusion of a mixture of soybean isoflavones and astragalus polysaccharide (200 mg/kg) significantly enhanced the lactation yield of sows (LWY × Landrace) compared to the control group. These differences as compared to the present study could be attributed to variations in breeds, environmental factors, or the physiological status of the sows. [57] , and can be used to indicate the fertility in subsequent reproductive cycles (Tubbs and Dyer, 1996) [56] . Whittemore and Kyriazakis, (2006) [62] mentioned that the weaning age of piglet affects both sow subsequent reproductive performance and piglet viability. Weaning before 21 days is associated with increased number of sows that do not show oestrus within 5 days of weaning, fewer ovulations, and lower embryo survival, partly due to incomplete uterine involution. Weaning after 21 days, however, allows the weaned sow for rapid resumption of estrous cyclicity with the rapid initiation of follicular development under follicle-stimulating hormone (FSH) and with subsequent luteinizing hormone (LH) surge driving the sow into estrus and ovulation. Furthermore, the duration of post-partum anoestrus is affected by environmental, genetic, physiological, and metabolic factors, including breed, nutrition, suckling, rate of uterine involution, follicular development, hormone levels and changes in body weight and energy intake. Thaker and Bilkei, (2005) [55] reported that lactation weight losses of sows are inversely related to subsequent reproductive performance of sows. In this regard, Tantasuparuk et al. (2001) [54] reported that sows with a high body loss during lactation had a significantly (p<0.05) longer WSI compared to sows with medium or low weight loss. The results of the present study are comparable to those reported by Kim et al. (2010) and Huang et al. (2020) [22] . Kim et al.

(2010) observed no significant difference in the weaning-toestrus interval between sows fed yeast culture, and the control group during gestation and lactation. Huang et al. (2020) [22] reported that inclusion of fermented soybean fiber (FSF) in gestation diet of sows (Landrace × Yorkshire) had no effect on weaning-to-estrus interval of sows. In contrast to the present findings, Zhao et al. (2022) [68] reported that Yeast culture (YC) supplementation improved the weaning-tooestrus interval of YC sows (Landrace) compared to control sows (5.16 d for YC sows, 6.12 d for control sows) (p<0.05). Non-significant differences in the weaning-to-estrus interval (WSI) observed in the present study may be attributed to the lack of variation in body condition score (BCS) during lactation between the treatment and control groups. The mortality rate (%) of LWY young pigs from 1st -4th weeks are presented in table 15a and causes of mortality in table 15b. Out of the 201 numbers of LWY piglets born alive, 23 numbers of piglets died (mortality rate-11.44%) during the experiment period (from birth to 4th week) with mortality rate (%) of 15.91, 10.78 and 9.03 and in Control (C), Treatment (T1) and Treatment (T1), respectively, The highest mortality occurred during the first week of lactation (52.18%), followed by 2nd week (26.08%), 3rd week (17.4%) and 4th week (4.34%). Statistical anylasis revealed non-significant (p>0.05) differences in the mortality rate of piglets among the experimental groups. Higher pre weaning mortality than the present study were recorded by Abraham (2001) [2] in landrace up to 28 days of age, Elmaz et al. (2008) [19] [38] up to 46 days of age, Kielland et al. (2018) [27] in crossbreed (Norwegian Landrace × Swedish Yorkshire) up to 32 days of age. Lower mortality rates compared to present finding were reported by Ramesh et al. (2006) [43] in Large White Yorkshire pigs up to 56 days of age and Stamati et al. (2006) [52] up to 28 days of age. The causes of mortality of LWY young pigs during the period of study were gastroenteritis, pneumonia, emaciated/weak, crushing and sudden death. These observations were comparable with the observations of Kalita et al. (2002) [26] , Hmar (2006) [21] , Edward &Bartex (2014), Muns et al. (2016) [39] and Vanlalpianpuia C. (2021). Although no significance differences were found in the mortality rate (%) among the groups in the present study, the numerically reduced mortality rate (%) of piglets under T1 compared to T2 and the Control group may be attributed to diets enriched with fermented soybean. This could have enhanced the immune function of sows, thereby facilitating the transfer of better immunity to piglets through colostrum and milk. Wang et al. (2016) [61] reported higher growth and lower piglet mortality in sows (Large White Yorkshire x Landrace) fed fermented soybean compared to sows without fermented soybean.

Conclusion

In conclusion, dietary inclusion of fermented soybean meal (FSBM) during late gestation and lactation improved piglet Growth performance and survivability during the nursing period, although no marked improvement was observed in body condition score (BCS) and litter performance of Large White Yorkshire pig sows. The present findings suggest that fermented soybean meal (FSBM) may serve as a promising supplementary feed ingredients for improving sow health during late gestation and lactation. However, further scientific research involving large number of sows might be of great help to better understand and fully exploit the potential benefits of FSBM on performance of sow.

References

1. Abdel-Raheem SM, Mohammed ESY, Mahmoud RE, El Gamal MF, Nada HS, El-Ghareeb WR, et al. Doublefermented soybean meal totally replaces soybean meal in broiler rations with favorable impact on performance, digestibility, amino acids transporters and meat nutritional value. Animals. 2023;13(6):1030.
2. Izatnagar, Bareilly, Uttar Pradesh: Indian Veterinary Research Institute; 2001.
3. Ampode KMB, Mun HS, Lagua EB, Chem V, Park HR, Kim YH, et al. Bump feeding improves sow reproductive performance, milk yield, piglet birth weight, and farrowing behavior. Animals. 2023;13(19):3148.
4. Anon. Practical manual-feeding schedule of sow. Barneveld, Netherlands: PTC Barneveld; 2005.
5. Soni A, Mishra S, Singh N, Bobade MD, Dubey A, Yadav A, et al. Body condition scoring of swine: A review. Int J Chem Stud. 2019;7(6):749-754.
6. AOAC International. Official methods of analysis of AOAC International. 17th ed. Washington DC: AOAC International; 2000. p.1-2.
7. Berchieri-Ronchi CB, Kim SW, Zhao Y, Correa CR, Yeum KJ, Ferreira AL. Oxidative stress status of highly prolific sows during gestation and lactation. Animal. 2011;5:1774-1779.
8. Borges VF, Bernardi ML, Bortolozzo FP, Wentz I. Risk factors for stillbirth and foetal mummification in four Brazilian swine herds. Prev Vet Med. 2005;70:165-176.
9. Chi CH, Cho SJ. Improvement of bio-activity of soybean meal solid-state fermentation with Bacillus amyloliquefaciens versus Lactobacillus spp. and Saccharomyces cerevisiae. LWT Food Sci Technol. 2016;68:619-625.
10. Cho KM, Jin HL, Han DY, Ahn BY, Kim H, Seo WT. Changes of phytochemical constituents during cheonggukjang soybeans fermentation using potential probiotics Bacillus subtilis CS90. J Food Compos Anal. 2011;24:402-410.
11. Close WH, Cole DJA. Nutrition of sows and boars. 1st ed. Nottingham: Nottingham University Press; 2001. p.377.
12. Coffey RD, Parker GR, Laurent KM. Assessing sow body condition. Kentucky: Cooperative Extension Service, University of Kentucky; 1999. ASC-158.
13. Cottrell JJ, Liu F, Hung AT, Digiacomo K, Chauhan SS, Leury BJ, et al. Nutritional strategies to alleviate heat stress in pigs. Anim Prod Sci. 2015;55:1391-1402.
14. Czech A, Grela ER, Kiesz M. Dietary fermented rapeseed or/and soybean meal additives on performance and intestinal health of piglets. Sci Rep. 2021;11(1):16952.
15. Demečková V, Kelly D, Coutts AG, Brooks PH, Campbell A. The effect of fermented liquid feeding on the faecal microbiology and colostrum quality of farrowing sows. Int J Food Microbiol. 2002;79:85-97.
16. Dima S, Fira S, Nissim S. Acute heat stress brings down milk secretion in dairy cows by up-regulating the activity of the milk-borne negative feedback regulatory system. BMC Physiol. 2009;9:13.
17. Dziuk P. Reproduction in the pig. In: Cupps PT, editor. Reproduction in domestic animals. New York: Academic Press; 1991. p.471-489.
18. Edwards SA, Baxter EM. Piglet mortality: causes and prevention. In: The gestating and lactating sow. 2014. p.253-278.
19. Elmaz O, Akdag F, Kutay C, Keser O. Creep feeding on survival ratio and growth performance of piglets. Indian Vet J. 2008;85(10):1080-1082.
20. Grant G. Anti-nutritional effects of soybean: a review. Prog Food Nutr Sci. 1989;13:317-348.
21. Hmar L. Pre-weaning mortality in Hampshire pigs. Indian Vet J. 2006;83(1):90-91.
22. Huang S, Wei J, Yu H, Hao X, Zuo J, Tan C, et al. Effects of dietary fiber sources during gestation on stress status, abnormal behaviors and reproductive performance of sows. Animals. 2020;10(1):141.
23. Imboonta N, Kuhaaudomlarp P. Genetic associations between stillbirth, total number of piglets born and gestation length in a commercial pig farm. Thai J Vet Med. 2012;42(2):165-172.
24. Jurgens MH, Rikabi RA, Zimmerman DR. The effect of dietary active dry yeast supplement on performance of sows during gestation-lactation and their pigs. J Anim Sci. 1997;75(3):593-597.
25. Kakati LJ, Kalita G, Hmar L, Samanta A, Tolenkhomba T, Das H, et al. Effect of dietary supplementation of Shatavari (Asparagus racemosus) root powder on reproductive performance of Large White Yorkshire sow. Int J Livest Res. 2019;1. doi:10.5455/ijlr.20180801062915.
26. Kalita G, Roychoudhury R, Goswami RN. Causes of preweaning mortality in piglets. Indian Vet J. 2002;79(1):72-73.
27. Kielland C, Wisløff H, Valheim M, Fauske AK, Reksen O, Framstad T. Preweaning mortality in piglets in loosehoused herds: etiology and prevalence. Animal. 2018;12(9):1950-1957.
28. Kim SW, Brandherm M, Newton B, Cook DR, Yoon I, Fitzner G. Effect of supplementing Saccharomyces cerevisiae fermentation product in sow diets on reproductive performance in a commercial environment. Can J Anim Sci. 2010;90(2):229-232.
29. Kumaresan A, Bujarbaruah KM, Pathak KA, Chhetri B, Das SK, Das A, et al. Performance of pigs reared under traditional tribal low input production system and chemical composition of nonconventional tropical plants used as pig feed. Livest Sci. 2007;107:294-298.
30. Lambo MT, Ma H, Zhang H, Song P, Mao H, Cui G, et al. Mechanism of action, benefits, and research gap in fermented soybean meal utilization as a high quality protein source for livestock and poultry. Anim Nutr. 2024;16:130-146.
31. Lavery A, Lawlor PG, Magowan E, Miller HM, O'Driscoll K, Berry DP. An association analysis of sow parity, live-weight and back-fat depth as indicators of sow productivity. Animal. 2018;1-9.
32. Lefebvre RC. Fetal mummification in the major domestic species: current perspectives on causes and management. Vet Med (Auckl). 2015;6:233-244.
33. Li Q, Yang S, Chen F, Guan W, Zhang S. Nutritional strategies to alleviate oxidative stress in sows. Anim Nutr. 2021;9:60-73.
34. Li Y, Johnston L, Hilbrands A. Pre-weaning mortality of piglets in a bedded group-farrowing system. J Swine Health Prod. 2010;18(2):75-80.
35. Livestock Census. The 20th livestock census-2019. New Delhi: Government of India; 2019.
36. Luo W, Yin X, Yao J, Cheng J, Zhang J, Xu W, et al. Fermented soybean meal affects the reproductive performance and oxidative status of sows, and the growth of piglets. Animals. 2021;11(3):597.
37. Maes DGD, Janssens GPJ, Delputte P, Lammertyn A, de Kruif A. Back fat measurements in sows from three commercial pig herds: relationship with reproductive efficiency and correlation with visual body condition scores. Livest Prod Sci. 2004;91(1-2):57-67.
38. Mondal SK, De UK, Das GK, Powde AM, Verma AK. Pattern of mortality of crossbred pigs in an organized swine production farm. J Livest Sci. 2012;3:37-44.
39. Muns R, Nuntapaitoon M, Tummaruk P. Non-infectious causes of pre-weaning mortality in piglets. Livest Sci. 2016;184:46-57.
40. Noblet J, Etienne M. Effect of energy level in lactating sows on yield and composition of milk and nutrient balance of piglets. J Anim Sci. 1986;63(6):1888-1896.
41. NRC. Nutrient requirements of swine. 11th revised ed. Washington DC: National Academies Press; 2012.
42. Payeng S, Borgohain A, Bora JR. Economics of pig production in organized and unorganized sectors. Indian Res J Ext Edu. 2013;13(1):101-106.
43. Ramesh V, Sivakumar T, Arunachalam S. Influence of supplementation of antioxidants on the reproductive performance of gilts under intensive system. Indian Vet J. 2006;83(4):456-458.
44. Reddy DV. Applied nutrition (livestock, poultry, human, pet, rabbit and laboratory animal nutrition). New Delhi: Oxford and IBH Publishing Company Pvt Ltd; 2001.
45. Rehfeldt C, Adamovic I, Kuhn G. Effects of dietary daidzein supplementation of pregnant sows on carcass and meat quality and skeletal muscle cellularity of the progeny. Meat Sci. 2007;75:103-111.
46. Ren M, Kuhn G, Wegner J, Nürnberg G, Chen J, Ender K. Feeding daidzein to late pregnant sows influences the estrogen receptor beta and type 1 insulin-like growth factor receptor mRNA expression in newborn piglets. J Endocrinol. 2001;170(1):129-135.
47. Sasaki Y, Koketsu Y. Variability and repeatability in gestation length related to litter performance in female pigs on commercial farms. Theriogenology. 2007;68:126-127.
48. Shang X, Cui Y, Shang C, Gao K, Chen Y, Quan Y. Effects of fermented soybean hulls on reproductive performance, blood physiology and immune parameters along with fecal microbiota in sows. Animals. 2024;14(23):3389.
49. Shen YB, Carroll JA, Yoon I, Mateo RD, Kim SW. Effects of supplementing Saccharomyces cerevisiae fermentation product in sow diets on performance of sows and nursing piglets. J Anim Sci. 2011;89:24622471.
50. Snedecor GW, Cochran WG. Statistical methods. 1st ed. New Delhi: East-West Press; 1994.
51. Song D, Li X, Cheng Y, Wu G, Xiao X, Wang F, et al. Effects of supplementing sow diets with Saccharomyces cerevisiae refermented sorghum dried distiller's grains with solubles from late gestation to weaning on the performance of sows and progeny. J Anim Sci. 2017;95(5):2025-2031.
52. Stamati S, Alexopoulos C, Siochu A, Saoulidis K, Kyriakis SC. Probiosis in sows by administration of Bacillus toyoi spores during late pregnancy and lactation: effect on their health status/performance and on litter characteristics. Int J Probiotics Prebiotics. 2006;1(1):33-40.
53. Tan CQ, Li JY, Ji YC, Yang YY, Zhao XC, Chen MX, et al. Effects of dietary supplementation of different amounts of yeast extract on oxidative stress, milk components, and productive performance of sows. Anim Feed Sci Technol. 2020;274.
54. Tantasuparuk W, Dalin A, Lundeheim N, Kunavongkrit A, Einarsson S. Body weight loss during lactation and its influence on weaning-to-service interval and ovulation rate in Landrace and Yorkshire sows in the tropical environment of Thailand. Anim Reprod Sci. 2001;65(34):273-281.
55. Thaker MYC, Bilkei G. Lactation weight loss influences subsequent reproductive performance of sows. Anim Reprod Sci. 2005;88(3-4):309-318.
56. Tubbs RC, Dyer K. Influence of parity and lactation length on wean-to-service interval and influence of wean-to-service interval on subsequent farrowing rate and litter size in 74,841 matings. In: Proceedings of the 14th IPVS Congress; Bologna, Italy; 1996. p.567.
57. Tummaruk P, Lundeheim N, Einarsson S, Dalin AM. Reproductive performance of purebred Swedish Landrace and Swedish Yorkshire sows: II. Effect of mating type, weaning-to-first-service interval and lactation length. Acta Agric Scand A Anim Sci. 2000;50:217-224.
58. Van de Lande T, Van Rens BT. Critical periods for foetal mortality in gilts identified by analyzing the length distribution of mummified foetuses and frequency of non-fresh stillborn piglets. Anim Reprod Sci. 2003;75:141-150.
59. Vanlalpianpuia C. Effect of dietary supplementation of guava (Psidium guajava) leaves on performance of young pigs pre and post-weaning periods [MVSc thesis]. Imphal, Manipur: Central Agricultural University; 2020.
60. Wang C, Lin C, Su W, Zhang Y, Wang F, Wang Y, et al. Effects of supplementing sow diets with fermented corn and soybean meal mixed feed during lactation on the performance of sows and progeny. J Anim Sci. 2018;96(1):206-214.
61. Wang PW, et al. Study on effects of microbial fermented soyabean meal on production performances of sows and suckling piglets and its acting mechanism. J Anim Feed Sci. 2016;25:12-19.
62. Whittemore CT, Kyriazakis I. Whittemore's science and practice of pig production. 3rd ed. Oxford: Blackwell Publishing; 2006.
63. Wu H, Yang J, Wang S, Zhang X, Hou J, Xu F, et al. Effects of soybean isoflavone and Astragalus polysaccharide mixture on colostrum components, serum antioxidant, immune and hormone levels of lactating sows. Animals. 2021;11:132.
64. Wu MC, Hentzel MD, Dziuk PJ. Effect of stage of gestation, litter size and uterine space on the incidence of mummified fetuses in pigs. J Anim Sci. 1988;66:32023207.
65. Young M, Aherne F. Monitoring and maintaining sow condition. Adv Pork Prod. 2005;16:299-313.
66. Yuan L, Chang J, Yin Q, Lu M, Di Y, Wang P, et al. Fermented soybean meal improves the growth performance, nutrient digestibility, and microbial flora in piglets. Anim Nutr. 2017;3(1):19-24.
67. Zhang Q, Li J, Cao M, Li Y, Zhuo Y, Fang Z, et al. Dietary supplementation of Bacillus subtilis PB6 improves sow reproductive performance and reduces piglet birth intervals. Anim Nutr. 2020;6:278-287.
68. Zhao Y, Wang Q, Zhou P, Li Z, Zhong W, Zhuo Y, et al. Effects of yeast culture supplementation from late gestation to weaning on performance of lactating sows and growth of nursing piglets. Animal. 2022;16(5):100526.