Abstract
The objective of this study was to examine the behavioral and growth responses of dairy heifers when a low-nutritive feedstuff was provided with (either within or alongside) a limit-fed ration. Twenty-four Holstein dairy heifers (187±11.3 d of age, 231.1±12.0kg), divided in groups of 4, were exposed to each of 3 treatments in a replicated Latin square design with 28-d periods. The treatment rations were (1) total mixed ration (TMR) in a limited amount (TMR-L), (2) TMR in a limited amount with straw (1.8kg of DM/d per heifer) offered as a choice (TMR-SC), and (3) TMR in a limited amount with straw (1.8kg of DM/d per heifer) mixed in (TMR-SM). The TMR was fed, once daily, at a restricted level (2.02% of body weight) and contained (on a DM basis) 19.0% alfalfa/grass haylage, 21% corn silage, 45% high moisture corn, and 15% protein supplement. Feeding behavior and unrewarded time at the feed bunk were recorded for the last 14 d of each period. Standing time was recorded for the last 7 d of each period. Rumination behavior was recorded twice weekly (during the fifth hour after feed delivery) in the last 14 d of each period. Body weight was recorded weekly and group DMI was recorded daily. Dry matter intake was lowest for the TMR treatment compared with the treatments with straw (5.7 vs. 7.3kg/d). Heifer average daily gain tended to be lower on the TMR-SM treatment compared with the TMR-L and TMR-SC treatments (0.78 vs. 0.94kg/d). Feed efficiency (DMI/ADG) was improved on the TMR-L (6.3) compared with TMR-SC (7.8) and TMR-SM (9.9) treatments. Daily feeding time differed between the TMR-L (76.1min/d), TMR-SC (206.9min/d), and TMR-SM (279.2min/d) treatments. Unrewarded feeding time at the feed bunk differed between the TMR-L (38min/d) compared with the TMR-SC (10.9min/d) and TMR-SM (1.7min/d) treatments. Inactive standing time differed among treatments, with TMR-L being the highest compared with TMR-SC and TMR-SM (556.4 vs. 409.9 vs. 340.1min/d). There tended to be fewer heifers ruminating on the TMR-L compared with TMR-SM (14.0 vs. 21.9%). The results suggest that provision of straw as a choice alongside a limit-fed ration will allow heifer growth rates to be met, as well as provide a suitable foraging source that heifers can use to satisfy their natural feeding behavior patterns.
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