Combs N R, Kornegay E T, Lindemann M D, Notter D R, Wilson J H, Mason J P
Dept. of Anim. Sci., Virginia Polytechnic Institute and State University, Blacksburg 24061.
J Anim Sci. 1991 Feb;69(2):682-93. doi: 10.2527/1991.692682x.
Three trials involving 251 crossbred pigs were conducted to establish response surfaces for effects of Ca/P levels (70, 85, 100, 115 and 130% of NRC [1979] estimated requirements) and time (weaning to market) on bone criteria and to compare bending and shear bone testing. Nine replicates, each consisting of five pigs, were used over the three trials. One pig per replicate was slaughtered every 4 wk following the start of the trials. Third metacarpals and metatarsals (3M) and fourth metacarpals and metatarsals (4M) were collected at slaughter; the bone length, bending or shear stress, and dry, fat-free ash percentage (DFF%) were determined. Most bone criteria increased (P less than .01) at a decreasing rate (P less than .05) in response to increasing dietary Ca/P intake and increased linearly (P less than .01) with time on test, although bone length and stress increased at a decreasing rate with time on test. Asymptotic models relating continuous effects of total Ca + P intake ratio (CAP; expressed as a percentage of NRC) and number of days on test before slaughter to bone measurements were fit to least squares slaughter time by diet means. Bone length and DFF% reached 98% maximum at or near 100% the NRC estimated CAP level; however, to reach 98% of maximum bone shear and breaking stress higher CAP levels were required. Shear testing of bones was more desirable than bend testing as a method of determining bone strength due to reduced variability, better discrimination of Ca/P and time effects and ease of calculation.
进行了三项涉及251头杂交猪的试验，以建立钙磷水平（分别为美国国家研究委员会[1979]估计需求量的70%、85%、100%、115%和130%）和时间（断奶至上市）对骨骼指标影响的响应面，并比较骨骼弯曲和剪切测试。在这三项试验中，共使用了9个重复，每个重复包含5头猪。试验开始后，每4周宰杀每个重复中的1头猪。在宰杀时采集第三掌骨和跖骨（3M）以及第四掌骨和跖骨（4M）；测定骨长度、弯曲或剪切应力以及干物质、无脂灰分百分比（DFF%）。随着日粮钙磷摄入量的增加，大多数骨骼指标以递减速率（P<0.05）增加（P<0.01），并且随着测试时间呈线性增加（P<0.01），尽管骨长度和应力随测试时间以递减速率增加。将总钙+磷摄入量比例（CAP；以占NRC的百分比表示）和宰杀前测试天数的连续效应对骨骼测量值的渐近模型拟合到按日粮均值计算的最小二乘宰杀时间。骨长度和DFF%在NRC估计的CAP水平达到或接近100%时达到最大值的98%；然而，要达到最大骨剪切和断裂应力的98%，则需要更高的CAP水平。作为一种确定骨骼强度的方法，骨骼剪切测试比弯曲测试更可取，因为其变异性更小、对钙磷和时间效应的区分更好且计算简便。
