Puoli J R, Jung G A, Reid R L
Div. of Anim. and Vet. Sci., West Virginia University, Morgantown 26506.
J Anim Sci. 1991 Feb;69(2):843-52. doi: 10.2527/1991.692843x.
The influence of N and S on the usage of warm-season grasses was examined in two metabolism trials with cattle and sheep. Effects of N fertilization (75 kg N from urea/ha) on digestibility, intake, and ruminal mineral solubilization of switchgrass (Panicum virgatum L.; SWG) and big bluestem (Andropogon gerardii Vitm.; BB) hays were determined in a 4 x 4 Latin square experiment with mature steers. Effects of N and S applied as urea and sodium sulfate in spray form to SWG hay were estimated in a 2 x 3 factorial experiment using sheep. Dry matter and NDF digestibility was greater (P less than .03) for BB than for SWG, and intake of SWG was 10% greater (P less than .06) than that of BB. Fertilizer N increased DMI (P less than .02) of SWG and BB by cattle by 11.4 and 16.1%, respectively. Fertilization decreased (P less than .04) ruminal turnover times by 9.3 and 18.5% for SWG and BB, respectively. In situ DM degradation rates were faster (P less than .02) for fertilized than for unfertilized forages and were faster (P less than .06) for BB than for SWG. In the sheep trials, levels of CP in SWG diets were 7.2 and 9.5%: levels of S were .12, .20, and .29%, respectively. Urea supplementation increased (P less than .01) hay intake by 9.4% and also increased (P less than .01) digestibility of DM and NDF. Supplemental S had no effect (P greater than .05) on any measurement. There was no effect (P greater than .05) of supplemental N on ruminal retention times, rates of passage, or apparent retention of N and S. The provision of extra N by fertilization or dietary supplementation improved the nutritional quality of the low-protein, warm-season grass hays studied in this experiment, whereas no response to dietary S was detected.
在两项针对牛和羊的代谢试验中，研究了氮（N）和硫（S）对暖季型牧草利用的影响。在一项用成年阉牛进行的4×4拉丁方试验中，测定了施氮肥（75千克尿素氮/公顷）对柳枝稷（Panicum virgatum L.；SWG）和大须芒草（Andropogon gerardii Vitm.；BB）干草消化率、采食量和瘤胃矿物质溶解的影响。在一项用绵羊进行的2×3析因试验中，评估了以喷雾形式施用尿素和硫酸钠中的氮和硫对柳枝稷干草的影响。大须芒草的干物质和中性洗涤纤维消化率高于柳枝稷（P＜0.03），柳枝稷的采食量比大须芒草高10%（P＜0.06）。施肥的氮使牛对柳枝稷和大须芒草的干物质采食量（DMI）分别提高了11.4%和16.1%（P＜0.02）。施肥使柳枝稷和大须芒草的瘤胃周转时间分别缩短了9.3%和18.5%（P＜0.04）。施肥牧草的原位干物质降解率比未施肥牧草快（P＜0.02），大须芒草的降解率比柳枝稷快（P＜0.06）。在绵羊试验中，柳枝稷日粮中的粗蛋白水平分别为7.2%和9.5%；硫水平分别为0.12%、0.20%和0.29%。补充尿素使干草采食量提高了9.4%（P＜0.01），同时也提高了干物质和中性洗涤纤维的消化率（P＜0.01）。补充硫对任何测定指标均无影响（P＞0.05）。补充氮对瘤胃保留时间、通过速率或氮和硫的表观保留率均无影响（P＞0.05）。通过施肥或日粮补充额外的氮提高了本试验中研究的低蛋白暖季型牧草干草的营养质量，而未检测到日粮硫的效应。
