Hall J B, Staigmiller R B, Bellows R A, Short R E, Moseley W M, Bellows S E
Fort Keogh Livestock and Range Research Laboratory, ARS, USDA, Miles City, MT 59301, USA.
J Anim Sci. 1995 Nov;73(11):3409-20. doi: 10.2527/1995.73113409x.
Rapid growth large frame (RL, n = 61) or average growth medium frame (AM, n = 71) biotype heifers fed to achieve either moderate (MOD, .6 kg/d) or high ADG (HI, 1.0 kg/d) were used to determine whether puberty occurs at similar body composition or metabolic status. A heifer was considered pubertal after being detected in estrus and then forming a functional corpus luteum. Live animal estimates of body composition and blood samples for assessment of metabolic status were taken at 13 +/- .2 d after estrus for all heifers. Body composition and metabolic status were assessed every 56 d from 7 mo of age until puberty in a subset of 80 heifers representing all biotype-diet combinations. At puberty, 32 of these 80 heifers were slaughtered and physical and chemical composition of the empty body were determined. High-gain diet heifers were younger, heavier, taller, and more muscular (all P < .01) at puberty than MOD heifers. Slaughter measurements paralleled live animal estimates; bodies of HI and RL heifers contained more (P < .01) carcass and noncarcass components than those of MOD and AM heifers, respectively. Carcasses of RL and HI heifers were more (P < .05) muscular and fatter than AM and MOD heifers. At puberty, HI heifers had a greater (P < .01) mass of moisture, fat, and fat-free organic matter (FFOM) than MOD, whereas RL heifers had more moisture, ash, and FFOM than AM. Percentage of fat was greater (22.1 +/- 1.0 vs 1.0 vs 19.1 +/- 1.0; P < .05) and percentage of moisture was less (55.4 +/- .6 vs 58.1 +/- .6; P < .01) in bodies of HI than in those of MOD heifers. Concentrations of blood urea nitrogen and insulin were greater (P < .05) in HI than in MOD heifers. Diet did not influence concentration of IGF-I or glucose, and metabolic markers were unaffected by biotype. No dramatic changes in body composition or metabolic signals were detected before puberty. Puberty did not occur at similar body composition or metabolic status in all heifers.
选取快速生长大体型（RL，n = 61）或平均生长中等体型（AM，n = 71）的生物型小母牛，分别饲喂以达到中等日增重（MOD，0.6千克/天）或高日增重（HI，1.0千克/天），用于确定青春期是否在相似的身体组成或代谢状态下发生。在小母牛发情被检测到并形成功能性黄体后，判定其进入青春期。所有小母牛在发情后13±0.2天进行活体动物身体组成评估和采集血样以评估代谢状态。从7月龄到青春期，对代表所有生物型 - 日粮组合的80头小母牛的一个子集每56天评估一次身体组成和代谢状态。在青春期时，这80头小母牛中的32头被屠宰，并测定空体的物理和化学组成。高增重日粮组的小母牛在青春期时比中等日增重组的小母牛更年轻、更重、更高且肌肉更发达（所有P < 0.01）。屠宰测量结果与活体动物估计值相似；HI和RL小母牛的身体分别比MOD和AM小母牛含有更多（P < 0.01）的胴体和非胴体成分。RL和HI小母牛的胴体比AM和MOD小母牛肌肉更发达且更肥（P < 0.05）。在青春期时，HI小母牛的水分、脂肪和无脂有机物质（FFOM）质量比MOD小母牛更大（P < 0.01），而RL小母牛的水分、灰分和FFOM比AM小母牛更多。HI小母牛身体中的脂肪百分比更高（22.1±1.0对19.1±1.0；P < 0.05），水分百分比更低（55.4±0.6对58.1±0.6；P < 0.01）。HI小母牛的血尿素氮和胰岛素浓度比MOD小母牛更高（P < 0.05）。日粮不影响IGF - I或葡萄糖的浓度，代谢标志物不受生物型影响。在青春期前未检测到身体组成或代谢信号的显著变化。并非所有小母牛都在相似的身体组成或代谢状态下进入青春期。
