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Rumination time in early lactation is associated with peak milk yield.

M. Peiter




Rumination time in early lactation is associated with peak milk yield.
M. Peiter*, H. N. Phillips, M. I. Endres. Department of Animal Science, University of Minnesota Saint Paul, MN.

Automatic milking systems (AMS) may include individual cow sensors that measure daily rumination time (RT) and activity. Total daily RT is normally reduced during the peripartum period and stabilizes to normal after the first week of lactation. Rumination time has been shown to be associated with health and milk yield. Peak milk yield (PMY) has a positive relationship with overall 305-d milk yield. Therefore, the objective of this study was to investigate the association between change in RT and average daily RT during the first 7 DIM and PMY. Daily cow data were collected from 34 free-flow AMS farms (n = 3,227 cows) in MN and WI. A simple linear regression line of best fit was estimated for RT over the first 7 DIM for each cow to calculate the change in RT (slope coefficient). Two separate linear mixed models were used with PMY as the outcome variable. Change in RT, parity (1, 2, and 3+), and the interaction term were included as fixed effects in the first model (M1). The other model (M2) used average RT during the first 7 DIM, parity, and the interaction term as fixed effects. Farm and cow within farm were included as random effects in both models. Statistical analyses were performed using R. Least squares means (�SE) for PMY were 42.3 � 0.78, 56.3 � 0.76, and 60.3 � 0.76, and average RT was 365, 401, and 393 min/d for parity 1, 2, and 3+, respectively. For M1 no interactions were found. For each 10-unit increase in change in RT, PMY increased by (coefficient [95% CI]) 5.9 [2.0, 9.8], 10.3 [7.5, 13.1], and 11.9 [9.0, 14.7] kg for parity 1, 2, and 3+, respectively. In M2, for each 10-unit increase in average RT, PMY increased by 1.3 [0.5, 2.0] and 1.4 [0.6, 2.2] kg for parity 2 and 3+, respectively; however, average RT was not associated with PMY for parity 1 (0.2 [-0.9, 1.3] kg). Change in RT was a better predictor of PMY compared with average RT for all parity groups, and especially for cows of parity ≥2. Results show that cows that increase RT at a faster rate after calving will peak higher, which most likely lead to higher overall milk yield.

Keywords: rumination, peak milk yield, automatic milking system.