Comparative evaluation of chelated and inorganic mineral supplements on milk production and quality in lactating Sahiwal cattle

Introduction

Mineral nutrition plays a vital role in maintaining the productivity, reproductive efficiency, and overall health of dairy cattle. Minerals function as cofactors for numerous enzymatic reactions involved in metabolism, immunity, and hormone synthesis (Suttle, 2010) [16] . In lactating cows, an adequate and balanced supply of macro-and micro-minerals is essential to sustain high milk yield and quality, prevent metabolic disorders, and ensure long-term reproductive performance (McDowell, 2003; NRC, 2001) [10,11] . Traditionally, minerals are supplied in the form of inorganic salts such as sulfates, oxides, or carbonates. However, their bioavailability is often limited due to interactions with dietary antagonists like phytates, oxalates, and fiber components that form insoluble complexes in the rumen, reducing absorption efficiency (Spears, 2003; Kincaid, 2000) [14,7] . To overcome these limitations, organic or chelated mineral sources-in which the mineral ion is bound to an organic ligand such as amino acids or peptides-have been developed. These chelated forms are more stable in the digestive tract and less susceptible to antagonistic interactions, thereby improving absorption and metabolic utilization (Ashmead, 1993; Spears & Weiss, 2008) [1,15] . Several studies have demonstrated improved milk yield, composition, and reproductive performance in dairy cattle supplemented with chelated trace minerals compared with inorganic sources. For instance, Kellogg et al. (2004) [6] and Cope et al. (2009) [5] reported enhanced milk production and somatic cell count reduction with organic Zn and Cu supplementation. Similarly, organic Zn-Mn complexes have been shown to improve udder health and milk fat synthesis (Miller et al., 2019) [11] . In Indian dairy systems, where feed resources are often deficient in trace minerals and the bioavailability of inorganic forms is variable, the use of chelated mineral mixtures offers a promising approach for improving animal performance under practical farm conditions (Bhanderi et al., 2013) [2] . The Sahiwal breed, a prominent indigenous dairy cattle of India, is known for its adaptability and disease resistance, but productivity can be constrained by nutritional imbalances, particularly mineral deficiencies (Bhosale et al., 2021) [4] . Evaluating mineral supplementation strategies in such native breeds is therefore important for sustainable productivity improvement. Hence, the present study was conducted at University Dairy Farm to evaluate the effect of chelated mineral supplementation on milk yield and milk constituents in lactating Sahiwal cows. It was hypothesized that feeding chelated minerals would enhance milk yield and composition compared to inorganic and unsupplemented control groups through improved mineral absorption and metabolic efficiency.

Materials and Methods

Selection of Experimental Animals

A total of 18 healthy lactating Sahiwal cows in their 4th and 5th lactations were selected based on uniformity in body weight, stage of lactation, and previous milk yield records. The cows were randomly allocated into three groups of six animals each (n = 6), ensuring comparable physiological and production status across treatments.

Experimental Design and Treatments

The trial was conducted for a period of 30 days following a completely randomized design (CRD). The animals were maintained under identical feeding and management conditions throughout the experimental period. The mineral mixture and chelated mineral mixture were procured from a reputed private manufacturer through local supply channels. These proximate values were within the range reported by Radotra (2003) [13] , Malik (2006) [9] , and Mahants (2008) [8] .

Housing and Health Management

All cows were maintained under uniform hygienic and managemental conditions. Proper ventilation, sanitation, and drainage were ensured. Routine prophylactic measures including vaccination (CBPP, LSD, Anthrax, FMD, Pasteurellosis) and deworming were carried out as per standard veterinary protocols. Sick animals, if any, were isolated and treated promptly under veterinary supervision.

Lactation Trial and Milk Recording

Milking was performed twice daily by hand milking at 6:00 AM and 6:00 PM. Individual milk yield was recorded at each milking using a spring balance (capacity 10 kg, accuracy ±0.1 kg). Daily milk yields were averaged for weekly and overall period means.

Parameters Estimated

Milk Fat (%): Determined by the Gerber's method as per IS:1224 (1977).

Milk Protein (%): Estimated by the Kjeldahl method (AOAC, 1995); total nitrogen × 6.38.

Specific Gravity (Sp. Gr.): Measured by Lactometer at 60°F using the formula Sp. Gr.=1+CLR

where CLR = Corrected Lactometer Reading.

Computed by Richmond's formula:

where F = Fat (%), G = Corrected Lactometer Reading.

Solid Not Fat (SNF,%): Calculated as SNF = TS -Fat (%).

Milk Density (DEN%): Determined using an Eko Milk Analyzer.

Statistical Analysis

Data were analyzed using Two-Factorial Completely Randomized Design (CRD) with the help of OPSTAT software (CCS HAU, Hisar). The model included the effects of treatment, period, and their interaction. Differences among means were tested using ANOVA, and significance was declared at P < 0.05. Simple mean values were also calculated using the formula:

Results and Discussion

Milk Yield

The average daily milk yield of cows in different treatment groups during the experimental period is presented in Table 3.

The mean milk yield at the start of the experiment (0th day) was 9.57 ± 0.95 L in the control group (T₁), 8.76 ± 0.49 L in the mineral mixture group (T₂), and 7.84 ± 0.54 L in the chelated mineral mixture group (T₃). After 30 days of feeding, average milk yield increased to 10.89 ± 0.86 L, 9.16 ± 0.46 L, and 10.30 ± 0.44 L in groups T₁, T₂, and T₃, respectively. The overall group effect was found to be significant (P < 0.05), indicating that mineral supplementation influenced milk yield. Period effect was also significant (P < 0.05), while interaction (Group × Period) was non-significant (P > 0.05). The relative increase in milk yield from day 0 to day 30 was highest in the chelated mineral mixture group (T₃, +31.4%), followed by the control (T₁, +13.8%) and mineral mixture groups (T₂, +4.6%). This clearly indicates that chelated minerals enhanced milk production efficiency compared with inorganic mineral supplementation and control diets. [3] and who observed significant improvement in milk yield of dairy cattle supplemented with chelated trace minerals compared to inorganic mineral mixtures. Spears (2003) [14] and Ashmead (1993) [1] suggested that the higher bioavailability of organic minerals results in improved metabolic activity and better utilization of nutrients, thereby enhancing milk production performance. Chelated minerals are less reactive in the rumen and more efficiently absorbed in the small intestine due to their stable organic bonding with amino acids or peptides (Spears & Weiss, 2008) [15] . Consequently, they can better support enzymatic and hormonal functions related to lactogenesis, explaining the higher milk yield in group T₃.

Milk Fat

The average milk fat percentage at the start of the trial was 3.77 ± 0.31, 3.53 ± 0.14, and 3.75 ± 0.42% in T₁, T₂, and T₃ groups, respectively (Table 4). After 30 days of supplementation, the mean fat percentage increased to 4.28 ± 0.35%, 3.82 ± 0.18%, and 4.17 ± 0.41%, respectively. Although differences among groups were not statistically significant (P > 0.05), the chelated mineral mixture group (T₃) showed a consistent improvement in milk fat content compared with the other groups. (a,b) within a row differ significantly (P < 0.05). NS = non-significant (P > 0.05). SE = Standard error; G = Group; P = Period; G×P = Interaction effect. These results agree with Kellogg et al. (2004) [6] and Cope et al. (2009) [5] , who reported that feeding organic Zn and Cu sources improved milk fat yield and composition. Trace elements such as Zn, Cu, and Mn are cofactors in several enzymes involved in lipid metabolism and mammary gland function (Suttle, 2010) [16] . Therefore, improved mineral availability from chelates could have contributed to higher fat synthesis.

Solid-Not-Fat (SNF)

The mean SNF percentage during the study increased across all treatment groups (Table 5), with the highest average recorded in the chelated mineral mixture group (T₃) (8.94 ± 0.12%) followed by T₂ (8.70 ± 0.14%) and T₁ (8.58 ± 0.13%). Although the group effect was non-significant (P > 0.05), period effect was significant (P < 0.05), suggesting that SNF content improved over time irrespective of treatment. a,b) within a row differ significantly (P < 0.05). NS = non-significant (P > 0.05). SE = Standard error; G = Group; P = Period; G×P = Interaction effect.

The improvement in SNF observed in T₃ may be attributed to better rumen fermentation and nutrient utilization associated with organic mineral supplementation, consistent with reports by McDowell (2003) [10] and NRC (2001) [11] , which emphasize the role of trace elements in carbohydrate and protein metabolism influencing milk solids.

Milk Protein

Protein content increased gradually in all groups over the course of the study (Table 6). The average protein percentages were 3.37 ± 0.05, 3.55 ± 0.05, and 3.45 ± 0.06% for T₁, T₂, and T₃, respectively, showing a significant group effect (P < 0.05). The highest protein content was recorded in the mineral mixture group (T₂), followed by chelated mineral (T₃) and control (T₁). Improved protein synthesis in mineral-supplemented groups could be related to the involvement of trace minerals like Zn, Mn, and Cu in enzymatic systems responsible for amino acid metabolism and casein formation (Spears, 2003; Suttle, 2010) [14, 16] . Although T₂ showed slightly higher mean protein content, the chelated mineral group (T₃) showed a greater proportional increase from baseline, highlighting enhanced nutrient utilization efficiency. These findings are in line with Miller et al. (2019) [11] , who observed improvement in milk protein and total solids upon feeding organic trace minerals to lactating cows.

Milk Density:

Average milk density values were 32.38 ± 0.21, 32.41 ± 0.48, and 30.41 ± 0.79% in groups T₁, T₂, and T₃, respectively (Table 7). Statistical analysis revealed significant differences among groups (P < 0.05). Density increased in all groups over time, with the control and mineral mixture groups showing higher values than the chelated mineral group. Density is a function of total solids content; hence variations can result from changes in fat or SNF proportions. Similar observations were reported by Bhanderi et al. (2013) [3] , where milk density and SNF improved marginally with mineral supplementation, although differences were not always statistically significant.

Milk Lactose

Lactose percentage ranged from 4.65 ± 0.20% at the beginning to 5.28 ± 0.19% at the end of the experiment (Table 8). Although there was no significant group effect (P > 0.05), all treatment groups showed a numerical increase in lactose content over time, indicating improved carbohydrate metabolism and mammary gland activity. The chelated mineral group recorded slightly higher improvement than the control. According to Bhosale et al. (2021) [4] , organic mineral supplementation enhances nutrient digestibility and metabolic activity, indirectly supporting lactose synthesis.

Conclusion

The study demonstrated that supplementation of chelated mineral mixture improved milk yield and enhanced milk composition parameters compared with inorganic mineral supplementation and the control diet. The effect was most pronounced in milk yield and fat content, suggesting better utilization of nutrients and improved lactation performance. Thus, chelated minerals can serve as a superior alternative to inorganic mineral mixtures for optimizing productivity and milk quality in lactating crossbred cows, particularly under conditions of suboptimal mineral nutrition.

References

1. Ashmead HD. The Roles of Amino Acid Chelates in Animal Nutrition. Park Ridge (NJ): Noyes Publications; 1993.
2. Bhanderi BM, Garg MR, Sherasia PL. Effect of supplementing chelated trace minerals and coated vitamins on the incidences of sub-clinical and clinical mastitis in dairy cows. Livest Res Rural Dev. 2013;25(4):1-8.
3. Bhanderi BM, Goswami S, Pandya PR, Patel AM. Mineral status of dairy animals in the coastal zones of South Gujarat, India. Indian J Anim Nutr. 2013;30(3):300-305.
4. Bhosale TR, Antre GR, Kumar D, Pandey RK. Effect of chelated minerals supplement on milk yield and composition of Sahiwal and Hariana cows. Asian J Dairy Food Res. 2021;40(2):189-192.
5. Cope CM, Mackenzie AM, Wilde D, Sinclair LA. Effects of level and form of dietary zinc on dairy cow performance and health. J Dairy Sci. 2009;92(5):21282135.
6. Kellogg DW, Tomlinson DJ, Socha MT, Johnson AB. Effects of zinc methionine complex on milk production and somatic cell count of dairy cows: twelve-trial summary. Prof Anim Sci. 2004;20(4):295-301.
7. Kincaid RL. Assessment of trace mineral status of ruminants: a review. J Anim Sci. 2000;77(1):1-10.
8. Mahants R. Effect of Mineral Supplementation on Production Performance of Dairy Cattle. Hisar (India): CCS Haryana Agricultural University; 2008.
9. Malik R. Nutritional Evaluation of Locally Available Feed Resources for Dairy Animals. Hisar (India): CCS Haryana Agricultural University; 2006.
10. McDowell LR. Minerals in Animal and Human Nutrition. 2nd ed. Amsterdam (Netherlands): Elsevier Science; 2003.
11. Miller JK, Miller WJ, Weaver GW. Roles of trace elements in animal production. J Anim Sci. 2019;97(7):2931-2947. doi:10.1093/jas/skz168
12. National Research Council (US) Committee on Animal Nutrition; Subcommittee on Dairy Cattle Nutrition. Nutrient Requirements of Dairy Cattle: 2001. 7th rev ed. Washington (DC): National Academies Press; 2001. 13. Radotra R. Comparative Study of Mineral Supplementation on the Performance of Crossbred Dairy Cattle. Hisar (India): CCS Haryana Agricultural University; 2003.
13. Spears JW. Trace mineral bioavailability in ruminants. J Nutr. 2003;133(5 Suppl 1):1506S-1509S. doi:10.1093/jn/133.5.1506S
14. Spears JW, Weiss WP. Role of mineral and vitamin supplements in dairy cattle nutrition. Vet Clin North Am Food Anim Pract. 2008;24(2):401-418. doi:10.1016/j.cvfa.2008.02.007
15. Suttle NF. Mineral Nutrition of Livestock. 4th ed. Wallingford (UK): CABI Publishing; 2010.