Vanzant E S, Cochran R C, Johnson D E
Kansas State University, Manhattan 66506.
J Anim Sci. 1991 Jul;69(7):3027-38. doi: 10.2527/1991.6973027x.
Six ruminally and eight bifistulated (ruminal and esophageal) Hereford x Angus heifers were used to determine effects of pregnancy and early lactation on forage intake and utilization under grazing conditions. Three ruminally and three bifistulated heifers were bred (pregnant/lactating; P/L; average calving date was February 11, 1989); remaining heifers served as controls (C). The experiment consisted of three periods (P1 = average of 55 d before parturition; P2 = average of 12 d before parturition; P3 = average of 26 d after parturition). All heifers grazed the same 24-ha Flint Hills range pasture. Dehydrated alfalfa pellets were supplemented at .5% BW/heifer daily prepartum and at .8% BW/heifer daily postpartum. Treatment x period interactions were noted (P less than .10) for forage OM intake, ruminal capacity, indigestible ADF (IADF) fill, and grazing time but not for OM digestibility or IADF passage rate (P greater than .10). In P1 and P3, P/L heifers had greater (P less than .10) forage OM intake than C heifers, whereas no differences were noted (P greater than .10) in P2. Pregnant/lactating heifers spent less time (P less than .10) grazing than did controls in P2 and more time (P less than .10) than controls in P3. Ruminal IADF fill and ruminal capacity, as measured by water fill, tended (P = .14 and .16, respectively) to differ between the two groups in P2. Digestibility of OM was unaffected (P greater than .10) by physiological status, whereas IADF passage rate was greater (P less than .10) in P/L heifers. Only minor differences were noted for the chemical composition of diets selected by the two groups. Ruminal fermentation patterns shifted only slightly; the largest effects were in P3, when P/L heifers had greater (P less than .10) propionate and less (P less than .10) acetate (mol/100 mol) than C heifers. In summary, during the period just before parturition, differences in forage OM intake between P/L and C heifers disappeared, and ruminal fill and capacity tended to be lower for P/L heifers. Intake was 16% greater for P/L than for C heifers during the early postpartum period. Organic matter digestibility was not influenced by physiological status, even though IADF passage rates were greater for P/L heifers.
选用6头安装了瘤胃瘘管和8头安装了双瘘管（瘤胃和食管）的赫里福德×安格斯小母牛，以确定妊娠和早期泌乳对放牧条件下牧草采食量和利用率的影响。3头安装瘤胃瘘管和3头安装双瘘管的小母牛进行配种（妊娠/泌乳；P/L；平均产犊日期为1989年2月11日）；其余小母牛作为对照（C）。试验包括三个阶段（P1 = 分娩前平均55天；P2 = 分娩前平均12天；P3 = 分娩后平均26天）。所有小母牛在同一24公顷的弗林特山牧场放牧。产前每天按每头小母牛体重的0.5%补充脱水苜蓿颗粒，产后按每头小母牛体重的0.8%补充。在牧草有机物质采食量、瘤胃容量、不可消化酸性洗涤纤维（IADF）填充量和放牧时间方面，观察到处理×阶段的交互作用（P < 0.10），但在有机物质消化率或IADF通过率方面未观察到交互作用（P > 0.10）。在P1和P3阶段，P/L小母牛的牧草有机物质采食量高于C小母牛（P < 0.10），而在P2阶段未观察到差异（P > 0.10）。在P2阶段，妊娠/泌乳小母牛的放牧时间比对照少（P < 0.10），在P3阶段比对照多（P < 0.10）。通过水填充测量的瘤胃IADF填充量和瘤胃容量在P2阶段两组之间有差异的趋势（分别为P = 0.14和0.16）。有机物质消化率不受生理状态的影响（P > 0.10），而P/L小母牛的IADF通过率更高（P < 0.10）。两组选择的日粮化学成分仅存在微小差异。瘤胃发酵模式仅略有变化；最大的影响出现在P3阶段，此时P/L小母牛的丙酸含量高于C小母牛（P < 0.10），乙酸含量低于C小母牛（P < 0.10）（mol/100 mol）。总之，在分娩前阶段，P/L和C小母牛之间的牧草有机物质采食量差异消失，P/L小母牛的瘤胃填充量和容量趋于较低。产后早期，P/L小母牛的采食量比C小母牛高16%。有机物质消化率不受生理状态的影响，尽管P/L小母牛的IADF通过率更高。
