Williams S N, Lawrence L A, McDowell L R, Wilkinson N S, Ferguson P W, Warnick A C
Anim. Sci. Dept., University of Florida, Gainesville 32611-0691.
J Anim Sci. 1991 Mar;69(3):1232-42. doi: 10.2527/1991.6931232x.
Fourteen Angus heifers (210 +/- 6 kg initial BW) were allotted randomly to either a low P (LP: .12% P, DM basis) or an adequate P (AP: .20% P, DM basis) diet fed for 14 to 16 mo under drylot conditions on concrete floors to determine the influence of dietary P on chemical, physical, and mechanical properties of bone. Three weeks postpartum, after 14 to 16 mo on their diets, heifers were slaughtered and the right and left third metacarpals (McIII) were excised; soft tissue was removed and metacarpals were frozen in .9% saline. Metacarpals were subjected to a three-point flexure test using an Instron Testing Machine with a crossload speed of 50 mm/min to determine mechanical properties. Broken McIII were reassembled and a 2-cm section was removed at point of loading for determination of chemical and physical properties. Breaking load (BL) was greater (P less than .05) for McIII from the AP than for those from LP heifers (1,348 vs 1,179 kg). Breaking strength (BS) was greater (P less than .05) for AP than for LP heifers (202.5 vs 189.2 MPa). Animals receiving AP diets had greater (P less than .01) bone mineral content (12.6 vs 11.2 g/2-cm slice) and percentage of bone ash (68.0 vs 67.2%) than did LP animals. No differences (P greater than .10) were observed between treatment groups in Ca, P, or Mg percentage in bone ash. Circular, elliptical, radiographic, and planimeter area indices all were greater (P less than .05) in AP than in LP animals (1,048, 729, 1,069, and 570 vs 932, 660, 957, and 523 mm2, respectively). These data indicate that mechanical properties of bovine third metacarpals are sensitive to dietary P and reflect P status in the bovine. Mineral content of bone was highly correlated with its mechanical and physical properties.
14头安格斯小母牛（初始体重210±6千克）被随机分配到低磷（LP：以干物质计，磷含量0.12%）或适宜磷（AP：以干物质计，磷含量0.20%）日粮组，在水泥地面的干栏式畜舍条件下饲养14至16个月，以确定日粮磷对骨骼化学、物理和机械性能的影响。产后三周，在按日粮饲养14至16个月后，宰杀小母牛，切除左右第三掌骨（McIII）；去除软组织，将掌骨冷冻于0.9%的盐水中。使用英斯特朗试验机以50毫米/分钟的横梁加载速度对掌骨进行三点弯曲试验，以测定机械性能。将折断的McIII重新组装，在加载点处截取2厘米长的一段用于测定化学和物理性能。AP组小母牛的McIII的断裂载荷（BL）高于LP组（1348千克对1179千克，P<0.05）。AP组的断裂强度（BS）高于LP组（202.5兆帕对189.2兆帕，P<0.05）。采食AP日粮的动物的骨矿物质含量（12.6克/2厘米切片对11.2克/2厘米切片）和骨灰百分比（68.0%对67.2%）高于LP组动物（P<0.01）。在骨灰中的钙、磷或镁百分比方面，各处理组之间未观察到差异（P>0.10）。圆形、椭圆形、射线照相和求积仪面积指数在AP组均高于LP组（分别为1048、729、1069和570平方毫米对932、660、957和523平方毫米，P<0.05）。这些数据表明，牛第三掌骨的机械性能对日粮磷敏感，并反映了牛的磷状况。骨骼的矿物质含量与其机械和物理性能高度相关。
