PROFILING OF MAJOR MILK PROTEINS FROM SELECTED BREEDS OF INDIGENOUS CATTLE
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Date
2022
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ICAR-NDRI, KARNAL
Abstract
The present study was aimed at the profiling of major milk proteins from indigenous breeds of cattle. The indigenous breeds of Tharparkar, Gir and Sahiwal and the cross-bred Karan Fries were studied. The milk samples collected from these animals were screened for mastitis and were grouped separately for further studies. The effect of mastitis on composition was also studied. Fat, SNF, Protein, lactose and ash content were higher in Tharparkar and lowest in Sahiwal among the indigenous breeds. Tharparkar was found to have the lowest milk yield among the breeds studied. Within the breeds, SNF, protein and lactose and total solids were lower in mastitic samples. Mastitis was also found to significantly lower (p<0.05) the milk yield in all the breeds. Tharparkar and Gir respectively had the highest and lowest crude protein %. A decline in crude protein, true protein, casein contents as well as casein to total protein ratio was observed in mastitic animals. Based on the protein profiling by RP-HPLC, the retention times of various casein fractions were as follows: κ-CN A (7.5-8.5 min), κ-CN b (9.5-10.5 min), αS2-CN (12-13 min), a peak of αS1-CN (18.5-19.5 min), αS1-CN B (20-20.5 min), β-CN A1 (23-24 min), β-CN A2 (24-25 min). Also, the amount of different fractions of milk proteins were found to be: αS1-CN (32-38%), αS2-CN (8-9.5%), β-CN (22.5-33.5%), κ-CN (10.5-14%) and whey proteins (15-21%).RP-HPLC results based on chromatograms of bovine milk casein standards were used for the identification of various casein fractions in milk and their corresponding genetic variants were identified based on literature. κ-CN AB variant was predominant in Tharparkar and Sahiwal breeds studied (77%), followed by κ-CN A, while the opposite was observed in Gir breed (72% κ-CN A and 28% κ-CN AB. αS1-CN B was dominant in indigenous breeds with a small population having an additional variant. The β-CN-A1A2 variant dominated in the studied population of Karan Fries (60%), while 40% of the herd still retained the A2 variant of its parent indigenous breed. Protein and Calcium content decreased significantly (p<0.05) with incidence of mastitis, accompanied by an increase in Rennet Coagulation Time (RCT). Protein, Calcium content and milk yield were significantly higher and RCT lower in milk samples having κ-CN AB variant in comparison to κ-CN A. Animals with β-CN A2 variant of cross-bred Karan Fries had significantly higher milk yield but longer RCT when compared with the β-CN A2 of Tharparkar. No significant differences were observed between compositional parameters in β-CN A1A2 and A2 population of Karan Fries. No significant effect of the variants of αS1-CN was found on the compositional parameters of indigenous breeds. The indigenous breeds were characterized for the genetic variants of different casein fractions. κ-CN AB was found to predominate in animals of Tharparkar and Sahiwal breeds in comparison to κ-CN A, which could possibly be related to better milk yield and rennetability.