Yelich J V, Wettemann R P, Dolezal H G, Lusby K S, Bishop D K, Spicer L J
Animal Science Department, Oklahoma Agricultural Experiment Station, Stillwater 74078-0425, USA.
J Anim Sci. 1995 Aug;73(8):2390-405. doi: 10.2527/1995.7382390x.
The effect of three rates of gain on carcass composition, lipid partitioning, age and BW at puberty, and concentrations of growth hormone (GH), IGF-I, insulin, glucose, and NEFA in plasma were evaluated in 38 Angus x Hereford heifers. Heifers were allotted by BW and age to three treatments with a replication in each of 2 yr: full-fed (n = 13; FF) to gain 1.36 kg/d; limit-fed (n = 12; LF) to gain .68 kg/d; maintenance-full-fed (n = 13; MFF) to gain .23 kg/d for 16 wk, then full-fed to gain 1.36 kg/d. Heifers were slaughtered within 10 d after the onset of puberty. At slaughter, kidney, pelvic, and heart fat (KPH) and udder (UDDER) were separated from carcass, as was fat surrounding viscera (OM). After 48 h at 4 degrees C a carcass side was dissected into subcutaneous fat (SC), intermuscular fat (SEAM), soft tissue (SFT = inseparable lean and fat), LEAN, and BONE. In yr 1, LF heifers (431 d) were older (P < .05) than MFF heifers (371 d) at puberty, but age of FF heifers (389 d) did not differ (P > .10) from that of LF and MFF heifers. In yr 2, FF heifers (351 d) were younger (P < .05) than LF and MFF heifers (398 and 434 d, respectively). The FF heifers had greater (P < .05) BW and a greater (P < .01) percentage of lipid in the carcass at puberty than LF and MFF heifers. During the first 16 wk of treatment, concentrations of NEFA were greater in heifers with slower daily gains (MFF > LF > FF; P < .01). Concentrations of NEFA were lesser and concentrations of IGF-I and insulin were greater in plasma of FF than in that of MFF heifers during the 10 wk before puberty. Treatment significantly altered age, BW, carcass composition, and lipid partitioning at puberty in beef heifers. We conclude that the percentage of body fat is not the sole regulator of puberty, and age may be an important modulator in determining the onset of puberty in beef heifers.
在38头安格斯×海福特小母牛中评估了三种增重速度对胴体组成、脂肪分布、青春期年龄和体重，以及血浆中生长激素（GH）、胰岛素样生长因子-I（IGF-I）、胰岛素、葡萄糖和非酯化脂肪酸（NEFA）浓度的影响。根据体重和年龄将小母牛分为三种处理，每种处理在2年中各重复一次：全饲（n = 13；FF），日增重1.36 kg；限饲（n = 12；LF），日增重0.68 kg；维持-全饲（n = 13；MFF），前16周日增重0.23 kg，然后全饲，日增重1.36 kg。小母牛在青春期开始后10天内屠宰。屠宰时，将肾周、盆腔和心脏脂肪（KPH）、乳房（UDDER）以及内脏周围脂肪（OM）从胴体上分离下来。在4℃下放置48小时后，将半片胴体解剖为皮下脂肪（SC）、肌间脂肪（SEAM）、软组织（SFT = 不可分割的瘦肉和脂肪）、瘦肉（LEAN）和骨骼（BONE）。在第1年，LF小母牛（431天）在青春期时比MFF小母牛（371天）年龄大（P < 0.05），但FF小母牛（389天）的年龄与LF和MFF小母牛无差异（P > 0.10）。在第2年，FF小母牛（351天）比LF和MFF小母牛（分别为398天和434天）年龄小（P < 0.05）。FF小母牛在青春期时体重更大（P < 0.05），胴体中脂肪百分比更高（P < 0.01），高于LF和MFF小母牛。在处理的前16周，日增重较慢的小母牛（MFF > LF > FF；P < 0.01）血浆中NEFA浓度更高。在青春期前10周，FF小母牛血浆中NEFA浓度较低，IGF-I和胰岛素浓度较高。处理显著改变了肉牛小母牛青春期的年龄、体重、胴体组成和脂肪分布。我们得出结论，体脂百分比不是青春期的唯一调节因素，年龄可能是决定肉牛小母牛青春期开始的重要调节因素。
