ARS | Publication request: Effect of milking frequency (1 vs. 4x) on milk yield, composition and numbers of gene transcripts for alpha-lactalbumin and beta casein in milk

Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: July 12, 2009
Publication Date: July 12, 2009
Citation: Alex, A.P., Collier, J.L., Hadsell, D.L., Collier, R.J. 2009. Effect of milking frequency (1 vs. 4x) on milk yield, composition and numbers of gene transcripts for alpha-lactalbumin and beta casein in milk [abstract]. Journal of Animal Science. 87(E-Suppl.2):49.

Technical Abstract: Recently published information indicates cytoplasm associated with milk fat globule membranes contains messenger RNA for the milk proteins casein and alpha-lactalbumin. Furthermore, differences in the concentration of these transcripts in mammary epithelial cells are reflected in differences in the concentration of these transcript in milk. Our objective was to evaluate the effect of 1 vs 4x milking frequency on milk yield and composition as well as concentration of messenger RNA transcripts for beta casein and alpha lactalbumin. Mean milk yield (kg/d) on d15, d60, d120 and d230 was 19.0, 18.2, 15.9 and 9.1 from the 4x half and 6.8, 7.2, 5 and 2.7 from the 1x half. Milk fat percent was on average slightly lower (3.34) in milk from 4x halves versus 1x halves (3.7) while protein percent was slightly higher (2.83 vs. 2.68). Lactose and solids not fat (SNF) percentages were higher in milk from 4x halves than 1x halves. Beta-casein expression in 4x milk at d15, 60, 120 and 230 was 3.2, 2.2, 4.8 and 2.4 fold higher than 1x milk. Alphalactalbumin gene expression in milk from 4x halves was 2.9, 3.6, 8.8 and 2.1 fold higher than 1x at d15, 60,120 and 230. Thus transcript numbers were higher in milk from udder halves milked 4x despite slightly lower fat concentrations in milk from these halves versus milk from 1x milked halves. We conclude that transcript concentration for the milk proteins alpha-lactalbumin and beta-casein reflected differences in milk yield associated with differences in milking frequency.