Abstract #T10

# T10
Feeding behavior of lactating dairy cows with genomic predisposition for residual feed intake fed at two levels of dietary neutral detergent fiber.
F. Sun*1, M. Aguerre2, J. Powell3,5, K. Weigel1, A. Pelletier3,5, P. Crump4, M. Wattiaux1, 1Department of Dairy Science, University of Wisconsin-Madison, Madison, WI, 2Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC, 3US Dairy Forage Research Center, Madison, WI, 4Department of Computing and Biometry, University of Wisconsin-Madison, Madison, WI, 5Department of Soil Science, University of Wisconsin-Madison, Madison, WI.

Our objective was to determine if genomic predisposition for residual feed intake (RFI) influenced the expected change in feeding behavior associated with increasing neutral detergent fiber (NDF) concentration in diet. Multiparous Holstein cows (n = 24) in mid-lactation were used in a randomized complete block design. Genomic and phenotypic data from previous trials were used to group cows as low RFI (L-RFI, −0.42 ± 0.01 kg/d) or high RFI (H-RFI, 0.34 ± 0.03kg/d). Following a 2-week covariate period during which cows were fed a diet with 31.7% NDF (dry matter basis), half of the cows in each RFI group were assigned to a diet with either 30.8 (L-NDF) or 34.0% (H-NDF) NDF for 4 weeks. Cows’ feeding behavior during the last 24 h of the experimental period was recorded with video camera. Videos were visually analyzed every 2.5 min and activity was assumed to persist the whole 2.5 min. Daily dry matter intake (DMI) and milk production were recorded individually for each cow. Covariate and experimental data were analyzed separately with SAS mixed procedure. During the covariate period L-RFI cows had lower DMI and higher feed efficiency (FE, milk-and-fat-corrected milk/DMI) than H-RFI cows (25.6 vs. 26.6kg/d, and 1.61 vs. 1.46, P ≤ 0 0.05). After 4 weeks of dietary changes, L-RFI cows tended to maintain greater FE than the H-RFI cows (1.64 vs. 1.47, P = 0.08), there was no dietary NDF by cow RFI interactions, and no RFI effects (P > 0.11) on any feeding behavior responses. Dietary NDF did not influence daily time spent eating or ruminating (181 ± 16.4, P = 0.20, and 396 ± 42.0min/d, P = 0.12). However, cows fed H-NDF had lower DMI (25.4 vs. 23.6 kg/d, P = 0.03), tended to spend more time chewing (539 vs. 601 min/d, P = 0.08) and drinking (25 vs. 40 min/d, P = 0.07), had smaller meal size (2.34 vs. 1.81kg DM/meal, P = 0.02) and spent more time eating, ruminating, and chewing per DMI (7.31 vs. 8.5, 15.2 vs.18.3, and 22.5 vs. 26.8min/kg DMI, P ≤ 0.05) than cows fed L-NDF. In this study, L-RFI cows maintained higher FE than H-RFI cows regardless of dietary NDF. Furthermore, most measured feeding behavior responses were influenced by dietary NDF but none of them were influenced by cow RFI or the dietary NDF by cow RFI interaction.

Key Words: chewing