Animal Welfare Program, University of British Columbia, 2357 Mall, Vancouver, BC, Canada, V6T 1Z4, Canada.
J Dairy Sci. 2012 Jul;95(7):3970-6. doi: 10.3168/jds.2011-5027.
This study assessed the carryover effects of providing forage during the milk-feeding period on postweaning feed intake and growth of heifers. At 11 wk of age, heifers previously (3 to 77 d of age) reared on starter (n=8) or starter plus grass hay (n=8) were switched to a single diet consisting of restricted amounts of concentrate [60% of the starter required to support daily body weight (BW) gain of 800 g] with ad libitum access to coarsely chopped orchardgrass hay. Feed intake and growth were measured from 11 to 18 wk of age. Starter dry matter (DM) intake averaged 2.14 ± 0.15 kg/d for both treatments. Forage consumption and total (starter plus hay) DM, neutral detergent fiber, crude protein, and metabolizable energy intakes were greater in heifers previously fed forage compared with those provided no forage. Initial and final BW were similar for the 2 treatments (108.2 ± 9.1 and 149.6 ± 9.3 kg, respectively). Overall average daily gain in heifers previously fed starter alone (0.92 ± 0.05,kg/d) tended to be greater than those previously fed starter plus hay (0.79 ± 0.06,kg/d). Total DM intake (starter plus hay) was lower in heifers previously fed starter alone than those fed starter plus hay (3.55 ± 0.13 vs. 4.08 ± 0.15 kg/d, respectively). Feed efficiency (BW gain/DM intake) after switching to a common diet was greater in calves previously fed starter alone than in those previously fed starter plus hay (0.26 ± 0.01 vs. 0.19 ± 0.01, respectively). However, heifers provided access to hay had a smaller body barrel (an indicator of gut fill) at 15 wk (127.7 ± 1.7 vs. 134.3 ± 2.7 cm) and 17 wk (132.4 ± 1.9 vs. 141.0 ± 2.2 cm) of age and had greater blood β-hydroxybutyrate (0.22 ± 0.04 vs. 0.32 ± 0.04 mmol/L) compared with heifers that did not have access to hay earlier in life. These results indicate that provision of hay early in life promotes forage intake when heifers are switched to a high forage diet. However, greater feed consumption did not translate into live BW gain. Higher feed efficiency after switching to a common diet in heifers previously fed starter alone compared with those fed starter plus hay must be viewed with caution because intestinal content likely varied between treatment groups.
本研究评估了在哺乳期提供饲料对后备牛断奶后采食量和生长的持续影响。在 11 周龄时，先前（3 至 77 日龄）用起始饲料（n=8）或起始饲料加干草（n=8）饲养的后备牛被转换为单一饮食，其中限制了浓缩物的摄入量[支持每日体重（BW）增加 800 克所需的起始饲料的 60%]，并且可以自由采食粗切的果园草干草。从 11 至 18 周龄测量饲料摄入量和生长情况。两种处理的起始干物质（DM）摄入量平均为 2.14±0.15kg/d。与未提供草料的后备牛相比，先前喂过草料的后备牛消耗的草料和总（起始饲料加干草）DM、中性洗涤剂纤维、粗蛋白和可代谢能摄入量更大。两种处理的初始和最终 BW 相似（分别为 108.2±9.1kg 和 149.6±9.3kg）。仅喂起始饲料的后备牛的平均日增重（0.92±0.05kg/d）总体上高于喂起始饲料加干草的后备牛（0.79±0.06kg/d）。仅喂起始饲料的后备牛的总 DM 摄入量（起始饲料加干草）低于喂起始饲料加干草的后备牛（分别为 3.55±0.13kg/d 和 4.08±0.15kg/d）。在转换为共同饮食后，仅喂起始饲料的小牛的饲料效率（BW 增加/DM 摄入量）高于喂起始饲料加干草的小牛（分别为 0.26±0.01 和 0.19±0.01）。然而，在 15 周（127.7±1.7cm 与 134.3±2.7cm）和 17 周（132.4±1.9cm 与 141.0±2.2cm）时，提供干草的后备牛的体躯桶（指示肠道充盈度）较小，并且血液 β-羟基丁酸（0.22±0.04mmol/L）高于早期未接触干草的后备牛。这些结果表明，在后备牛转为高草料饮食时，早期提供草料可促进草料的摄入。然而，较高的饲料消耗量并没有转化为活体 BW 增加。与喂起始饲料加干草的后备牛相比，仅喂起始饲料的后备牛在转换为共同饮食后的饲料效率更高，这一点必须谨慎看待，因为处理组之间的肠道内容物可能存在差异。
