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Is the rate of milk yield increase in early lactation associated with milking frequency, rumination, and activity in dairy cows?

M. Peiter

Events

06-22-2020

Abstract:

137
Is the rate of milk yield increase in early lactation associated with milking frequency, rumination, and activity in dairy cows?
M. Peiter*, H. N. Phillips, M. I. Endres. Department of Animal Science, University of Minnesota Saint Paul, MN.

Peak milk yield (PMY) has been shown to be positively associated with whole lactation milk yield. Cows that peak early with high PMY and are able to maintain a high overall milk yield during their lactation are desirable. Therefore, the objectives of this study were: 1) to investigate the association between milk yield increase rate (MIR) and 250-d milk yield (250MY), and 2) to investigate the association between MIR and early lactation change in rumination time (RT), activity, and number of successful milkings. Daily cow data were collected from 34 free-flow AMS farms in MN and WI. Milk yield increase rate was calculated by dividing PMY by days at peak for each cow. A simple linear regression line of best fit was estimated for RT over the first 7 DIM for each cow to find the change in RT. Activity and milkings were averaged over the first 7 DIM. A nonparametric regression test using Huh-Jhun methods while controlling for parity group was performed to measure the association between MIR and 250MY. A multivariate linear mixed model was performed with MIR as the outcome variable (n = 3,117). The model included main effects of change in RT, activity, milkings, and parity (1, 2, 3+) as fixed effects. Farm and cow within farm were included as random effects. The Wald statistic indicated that the 250MY increased by 455 kg per each kg increase in MIR (n = 859; P = 0.0002). The inclusion of all the predictors improved the multivariate linear mixed model fit. However, milkings had the greatest association with MIR (0.067 � 0.007 kg/d per 1-unit increase in milkings; P < 0.0001). The mean [95% CI] MIR was 0.76 [0.72, 0.81], 1.33 [1.3, 1.4], and 1.38 [1.3, 1.4] kg/d for parity 1, 2, and 3+, respectively. Parities 2 and 3+ had greater MIR than parity 1 (P < 0.0001). Due to the association found between the rate of increase in milk yield until peak and 250MY yield, this study suggests that increasing the number of milkings during the first 7 DIM may increase the MIR and subsequent whole lactation milk yield.

Keywords: early lactation, milking frequency, milk yield.