Feed delivery method affects the learning of feeding and competitive behaviour in dairy heifers.

The objective of this study was to determine how different feeding methods may affect the learning of feeding, sorting, and competitive behavior of growing dairy heifers. We hypothesized that heifers previously fed a total mixed ration (TMR) would distribute their feeding time more evenly throughout the day, sort the new ration less, compete less for feed, maintain a more solid fecal consistency, and continue to grow rapidly compared with heifers previously fed a top-dressed ration (TDR). Thirty-two Holstein heifers (237.2 ± 21.9 d of age) were divided into 8 groups of 4 and exposed to 1 of 2 treatments for 13 wk: 1) TMR or 2) TDR, with each containing 65% grass/alfalfa haylage and 35% textured concentrate on a dry matter (DM) basis. Following this feeding period, all heifers were switched to an unfamiliar TMR containing 56.1% grass/alfalfa haylage, 21.0% corn silage, 21.0% high-moisture corn, and 1.9% mineral supplement (DM basis) for 7 wk. Group DM intakes were recorded daily throughout the experiment. Feeding behavior, recorded using time-lapse video, and sorting behavior were measured for 7 d during wk 1, 4, and 7 after the dietary change. Feeding competition was measured on d 2, 4, and 6 of each recording week. Sorting activity was determined through particle size analysis of the fresh feed and orts. The particle size separator separated feed into 4 fractions (long, medium, short, and fine). Sorting of each fraction was calculated as actual intake expressed as a percentage of predicted intake. Animals were scored for fecal consistency twice weekly, using a scale from 1 (liquid) to 4 (solid). Heifers were weighed every 2 wk. Neither DM intake (9.0 kg/d) nor average daily gain (1.2 kg/d) differed between treatments. Sorting also did not differ between treatments. Heifers tended to spend more time feeding if they had previously been fed a TDR (198.8 vs. 186.8 min/d). As they had done before the dietary change, heifers previously fed the TDR spent more time at the bunk in the 2 h following feed delivery (40.6 vs. 25.9 min/d). Heifers previously fed the TDR were displaced from the feed bunk more frequently than heifers previously fed the TMR (23.0 vs. 13.1 times/d), particularly during the 2-h period following feed delivery. Fecal scores were lower (more fluid in consistency) for heifers originally fed the TDR (3.2 vs. 3.7). The continued difference in feed bunk competition suggests that heifers previously fed the TDR had learned these patterns in the past, retaining them even when switched to an unfamiliar ration. Furthermore, lower fecal scores for heifers previously fed the TDR suggest altered rumen fermentation, possibly because of altered diurnal consumption patterns. These results show that feeding a TMR to replacement dairy heifers from a young age promotes a more even diurnal feeding pattern, minimizes feed bunk competition, and promotes a more solid fecal consistency.