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Association between feed efficiency, milk production, rumen fermentation, and feed sorting behavior of lactating dairy cows.

H. Guan

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06-23-2020

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Abstract:

T6
Association between feed efficiency, milk production, rumen fermentation, and feed sorting behavior of lactating dairy cows.
M. Agarussi, H. Guan*, K. G. Arriola, H. Sultana, I. Fernandez, C. Nino de Guzman, S. Lee, F. X. Amaro, A. Oyebade, L. F. Ferraretto, E. K. Miller-Cushon, D. Vyas. University of Florida Gainesville, FL.

Feed sorting behavior has implications for rumen health and milk production. The objective of this study was to examine the associations between feed efficiency and feed sorting, activity, milk components, and rumen pH and fermentation parameters. Sixteen lactating dairy cows were enrolled at 80 � 15 DIM and data were collected during a 4 d period repeated over 3 consecutive weeks. Feed efficiency was defined as milk production per unit of DMI. Fresh TMR and orts samples were collected daily from individual cows for particle size separation. The 3 screens (19, 8, and 1.18 mm) and a bottom pan resulted in 4 fractions (long, medium, short, and fine). Sorting was calculated as the actual intake of each particle size fraction expressed as a percentage of the predicted intake of that fraction. The pH of rumen contents was measured immediately after fluid collection using stomach tube and rumen samples were analyzed for ammonia-N (NH3-N) concentration. Association between feed efficiency and predictor variables was analyzed with multivariable mixed-effects linear regression models. The model included the random effect of cow and weeks were used as repeated measures. Unconditional associations between feed sorting, resting time, and milk composition were examined and independent variables associated with the outcome variable (P < 0.25) were considered for inclusion in the final model. Feed efficiency was associated with sorting for long ration particles (0.013 � 0.007; P = 0.10), fat percent (−0.12 � 0.04; P < 0.01); protein percent (0.70 � 0.11; P < 0.01), standing time (0.0008 � 0.0003; P < 0.01), and lying duration (0.004 � 0.002; P = 0.10). A weak association of feed efficiency was also observed with rumen pH (P = 0.21) and NH3-N concentration (P = 0.19). Milk fat (P = 0.10) and milk protein yield (P < 0.01) were associated with sorting against long forage particles. In conclusion, sorting for long forage particles is associated with feed efficiency; however, lying behavior is more associated with feed efficiency.

Keywords: activity, efficiency, feed sorting.