Abstract #M17

# M17
Associations between feed push-up frequency, lying and feeding behavior, and milk composition of dairy cows.
Emily K. Miller-Cushon*1, Trevor J. DeVries2, 1Department of Animal Sciences, University of Florida, Gainesville, FL, 2Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada.

The objectives of this study were to assess the effects of feed push-up frequency on lying behavior and feed sorting of dairy cows, and to determine associations between behavior and milk composition. Lactating Holstein dairy cows (n = 30; parity = 1.9 ± 1.1; mean ± SD) were individually housed in tie stalls, milked 2×/d, and offered ad libitum access to water and TMR (containing on DM basis: 25% corn silage, 25% grass/alfalfa haylage, 30% high-moisture corn, and 20% protein/mineral supplement), provided 1×/d. Cows were divided into 2 groups of 15 (balanced by DIM, milk production, and parity) and individually exposed to 2 treatments in a crossover design with 21-d periods: (1) infrequent feed push up (3×/d), and (2) frequent feed push up (5×/d). During the last 7 d of each period, DMI and milk production were recorded and lying behavior was monitored using electronic data loggers. During the last 2 d of each period, milk samples were collected for analysis of protein and fat content and feed samples were collected for particle size analysis. The particle size separator had 3 screens (19, 8, and 1.18 mm) and a bottom pan, resulting in 4 fractions (long, medium, short, fine). Sorting was calculated as the actual intake of each particle size fraction expressed as a percentage of the predicted intake of that fraction. Data were analyzed in multivariable mixed-effect regression models. Feed push up frequency had no effect (P > 0.3) on lying time (11.4 h/d; SE = 0.37) or feed sorting; cows sorted (P < 0.001) against long particles (78.0 ± 2.2%; mean ± SE) and for short (102.6 ± 0.6%) and fine (108.4 ± 0.9%) particles. Milk fat content increased (P < 0.001) by 0.1% for every 10% increase in sorting for long particles and was not associated with lying behavior or other cow-level factors. Milk protein content increased (P < 0.003) by 0.07% for every 1 h/d increase in lying time and by 0.05% for every 10% increase in sorting in favor of long particles. These results suggest that reduced lying time and sorting against long ration particles negatively affected milk composition. Further, this study did not find that altering feed push-up frequency affected feed sorting.

Key Words: feed sorting, lying behavior, milk