Effect of high milk feeding on blood biochemical parameters of early weaned crossbred (HF × K) calves

Introduction

The dairy calves are the future replacement stock (Fischer et al. 2019) [8] at the dairy farm. The suboptimal milk feeding to calves during the initial 90 days results in high mortality, reduced feed intake, and delayed puberty, which adversely affect the economics. The calves are monogastric during their initial life, as the abomasum is the only functional compartment, with 65% of the total stomach capacity, while the rest 25% is the rumen. At age of 3 to 4 months, the rumen contributes 65%, and the abomasum contributes 20% of the total stomach capacity. Therefore, during their early life, the calves require more milk as the primary source of nutrients. The volume of milk feeding to dairy calves could affect physiological, immunological, behavioral and economic traits. The quantity of milk given to dairy calves during the preweaning stage affects their growth, health, and consumption of dry feed (Appleby et al. 2001) [3] . Enhanced nutrient intake stimulates the somatotropic axis-mainly GH, IGF-1, and IGFBPs-which supports body and organ development (Breier et al. 2000) [5] , including the immune system and mammary gland. Higher levels of glucose, insulin, and IGF-1 are seen in well-fed calves, promoting better rumen development. Thus, optimizing nutrition is key to improving calf performance and growth. Based on the aforementioned considerations, the study aims to assess the comparative performance of early-weaned dairy crossbred calves (HFxKankrej) under various milk feeding regimes.

Materials and Methods

The study was conducted at Livestock Research Station, Veterinary and Animal Science Research & Extension Unit, Kamdhenu University, Anand, Gujarat, after IAEC approval (No. 362/LRS/2022) for 182 days (26 weeks). The total of 25 newborn crossbred calves (75% Holstein Friesian × 25% Kankrej) were grouped into five treatments, comprising two male and three female calves in each. All calves were offered colostrum and milk as per Table 1 in step up and step-down manner. The calves were fed a total mixed ration-TMR1 (75% Concentrate, 15% green Hybrid Napier, and 10% dry Jowar hay) and TMR-2 (65% Concentrate, 15% green Hybrid Napier, and 20% dry Jowar hay) ad lib. during 15-90 days and 91-182 days.

Results and Discussion

Blood biochemical parameters

The blood biochemical parameters of experimental crossbred calves are summarized in Table 2. The serum glucose levels (mg/dL) were lower (P<0.01) in T5 than in T2 and T3, groups. The significantly lower glucose level in T5 indicates a less favourable energy status compared to other groups. The serum glucose (mg/dL) level in crossbred calves was within physiological range (Hussein et al. 2020) [10] . A decreasing trend was observed with age, from 15 days to 182 days (Fig 1), attributed to the physiological shift from glucose to VFA as the primary energy source with rumen development and increased solid feed intake. These findings align with Babitha et al. (2011) [4] and Mirzaei et al. (2015) [15] , who noted elevated early-life glucose due to glucagondriven gluconeogenesis from colostrum and milk lactose intake. The serum levels of total protein (g/dL), albumin (g/dL), and globulin (g/dL) were not influenced (p>0.05) by various milk feeding protocols. The albumin-to-globulin (A: G) ratio was lower (p<0.01) in T2 and T3 groups compared to other protocols. A progressive increase in serum total protein and albumin levels was noted over time from 15 days to 182 days (Fig 2 and Fig 3, respectively), likely due to increased starter intake and better health in foragesupplemented calves (Daneshvar et al. 2015) [7] and hepatic tissue maturation and increased solid feed intake, as reported by Souza et al. (2019) [21] respectively. These findings align with those of Alimirzaei et al. (2020) [2] , and Jafari et al. (2021) [11] , who observed that total protein and albumin concentration remained unaffected by milk feeding methods or quantities. The average value of the serum A: G ratio remained within the normal physiological range (Hussein et al. 2020) [10] . A fluctuating trend was noted over time, suggesting dynamic changes in albumin and globulin synthesis during calf development. These findings are supported by the research outcome of Patel (2022) [17] as a 1.26 A: G ratio value under varying feeding methods. The serum creatinine (mg/dL) level increased (p<0.01) from T1 to T4 and were within physiological range (Klinkon and Jezek, 2017) [14] , indicating it is safe on kidney functions to feed higher quantity of milk. These findings are consistent with Shukla (2016) [19] and Khan et al. (2007a) [13] , who observed declining trends with age, whereas Patel (2022) [17] reported a slightly higher mean value (1.44 mg/dL), possibly due to variations in milk feeding strategies. The liver function as indicated by value of Serum Glutamic Pyruvic Transaminase (SGPT; U/L) and Serum Glutamic Oxaloacetic Transaminase (SGOT; U/L) was without influence of milk feeding protocols and also were within physiological range (Teneva et al. 2021) [22] . This indicates it is safe to feed various quantities of milk from T1 to T5 to crossbred calves. The SGPT levels were raised after preweaning phase, indicating increased liver enzyme activity in the post-weaning phase. This rise is likely linked to higher dry matter and DCP intake post-weaning. The present findings align with those of Alimirzaei et al. (2020) [2] , Patel (2022) [17] , and Sharma (2023) [18] , supporting the trend of increasing SGPT with age and feeding intensity with normal liver function. The serum level of Insulin Growth factor (IGF-1; ng/ml) was higher (p<0.01) in T3 and T4 compared to T1, T2 and T5 groups. The serum level of β-hydroxybutyrate (BHBA; nmol/ml) was also higher in (p<0.01) T3 and T4 groups, indicating better growth rate and better fat turnover in higher milk-fed protocols. The IGF-1 levels, a key growth marker, are associated with higher milk intake, likely due to improved nutrient availability and growth. These findings align with Hammon et al. (2002) [9] , who highlighted the role of nutrition in regulating IGF-1, as well as Kerr et al. (1991) [12] and Patel (2022) [17] , who also reported increasing IGF-1 levels with calf age and milk intake. The overall mean BHBA level was increased with age, with a notable rise after weaning. BHBA levels, reflective of rumen fermentation and VFA utilization, were also significantly (p<0.01) higher in T3, T1, and T4, suggesting more active energy metabolism. This increase reflects a physiological shift from liquid to solid diets, enhancing rumen development (Nemati et al. 2015) [16] . These results align with Cheema et al. (2016) [6] and Abbasa et al. (2017) [1] . In summary, T3 and T4 consistently showed favourable biochemical indicators, suggesting better metabolic and growth performance under this milk feeding regime.

Conversely, T5 generally exhibited lower values in energyrelated and growth-related parameters, reflecting comparatively poorer metabolic status.

References

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