Adsa Logo White Adsa Title White

β-Casein A2 genetics of organic Holstein dairy cows across the Midwest and Northeast.

B. J. Heins

Events

06-24-2020

Abstract:

327
β-Casein A2 genetics of organic Holstein dairy cows across the Midwest and Northeast.
B. J. Heins*1, G. M. Pereira1, L. C. Hardie2, C. D. Dechow2. 1University of Minnesota Morris, MN, 2Pennsylvania State University State College, PA.

The objective of the study was to determine milk, fat, protein production and SCS for β casein A2 genotypes of organic Holstein cows. Holstein cows (n = 382) from 5 dairy herds across the Midwest and Northeast were genomic tested with CLARIFIDE Plus for A2 status. Twenty-eight cows were A1A1 (7%), 165 cows were A1A2 (43%) and 189 cows were A2A2 (49%). In total, 637 lactation records were used with 375 from first parity, 211 from second parity, and 51 from third parity. Daily milk, fat, and protein production and SCS from milk recording were calculated with Best Prediction. Best prediction was used to calculate actual production (milk, fat, and protein) for 305-d lactations. Adjustment was made for age at calving and milking frequency, and records less than 305 d were projected to 305 d. Independent variables for statistical analysis with PROC MIXED included the fixed effects of parity, herd and milk β casein genotype (A1A1, A1A2, A2A2). Cow and birth date were random effects in the statistical model. Milk production was not different (P > 0.12) for A1A1 (7,970 kg), A1A2 (7,910 kg), and A2A2 (7,728 kg) cows. Fat plus protein production was not different (P > 0.14) for A1A1 (600 kg), A1A2 (591 kg), and A2A2 (581 kg) cows. Furthermore, SCS was not different (P > 0.44) for A1A1 (2.68), A1A2 (2.53), and A2A2 (2.61 kg) cows. Results indicate no difference in production and SCS with regard to A1 or A2 genotype in organic dairy herds.

Keywords: genetic selection, organic, A2 milk.