Effects of Cubing Alfalfa Hay on Development of Yearling Beef Heifers and In Situ Rate and Extent of Disappearance

Abstract

The objective of this study was to evaluate the effects of cubing alfalfa on heifer development and in situ ruminai NDF and CP disappearance. One hundred ninety-two prepuberal crossbred heifers were allotted to 16 pens with each pen randomly allotted to treatment; 1) cubed alfalfa (CA) or 2) long alfalfa (LA). Diets were consumed ad libitum. Heifers were weighed every 28 d throughout the 96-d trial. Following synchronization, heifers were bred by AI 12h after observed estrus. Hay intake by CA heifers was lower (P<.05) than LA heifers (11.6 vs 13.5kg per head per d), but ADG was faster (P<.05) for CA heifers than those fed LA (1.35 vs 1.03kg per head per d). Feed per kilogram of gain was lower (P<.05) for heifers fed CA than for heifers fed LA (8.6 vs 13.2kg:kg). No differences were observed in number of heifers bred AI (P>.25)or in total pregnancy (P>.25). Six mature beef cows fitted with ruminal cannula were used in a switchback design to determine influence of cubing on in situruminal CP and NDF disappearance. During each period animals consumed their respective diets ad libitum for 14 d of adaptation and 5 d of data collection. Nylon bags containing 5-g samples of either CA or LA were ruminally incubated for 12,24,36,48,72, and 96h. Bag residues were analyzed for DM, CP, and NDF content. The DM and NDF disappearance rate constants and extent of DM disappearance for CA (.27, .11, and 79.6%, respectively) were higher (P<.04) than LA(.16, .08, and 68.1%, respectively). Crude protein rate constants were similar (P>.05) forCA (.33) and LA (.28). Results from the heifer development trial suggest that heifers fed CA gained faster and were more efficient than heifers fed LA. No differences were detected in reproductive performance, possibly because all heifers reached the recommended weight for puberty at the beginning of the breeding season regardless of treatment (average, 409kg). Results from the in situ trial indicate ruminal DM and NDF disappearance were enhanced by cubing alfalfa, but not rate of CP disappearance.