Sarko T A, Bishop M D, Davis M E
Animal Science Department, Ohio State University, Columbus 43210-1095.
Domest Anim Endocrinol. 1994 Jul;11(3):281-90. doi: 10.1016/0739-7240(94)90019-1.
Eight paternal half-sib Angus calves born in late April and early May, 1988 were used to investigate the potential relationship of serum IGF-I concentration with photoperiod and various weather variables including minimum, maximum and average air temperatures, relative humidity, precipitation, wind speed and solar radiation. To determine IGF-I concentration, blood samples were obtained at birth and then weekly until the calves reached 1 mo of age and bi-weekly thereafter. Blood sampling continued until the calves reached puberty as determined by progesterone and testosterone assays. Photoperiod and each weather variable were averaged over the 3 d prior to and including the day of blood sampling (4-d average). Data were divided into two periods: (1) birth through the end of the postweaning period and (2) postweaning period only. Serum IGF-I concentrations were analyzed using a model which included the fixed effects of sex and sample number, the random effect of calf nested within sex and the fixed interaction of sex x sample number, in addition to covariates for weight, photoperiod and weather variables. From birth through the end of the postweaning test, none of the weather variables or photoperiod had significant effects on serum IGF-I concentrations when each was fitted separately. For the postweaning period only, cubic regression coefficients for minimum and average temperatures were .0962 +/- .0325 ng/ml/degrees C3 and .0976 +/- .0272 ng/ml/degrees C3, respectively (P < .01). The quadratic regression coefficient for relative humidity during the postweaning period was -.2991 +/- .1142 ng/ml/%2 (P < .05). The quartic regression coefficient for wind speed during the postweaning period was -36.435 +/- 13.00 ng/ml/(km/hr)4 (P < .01). Maximum temperature, precipitation, solar radiation and photoperiod did not have significant effects on postweaning serum IGF-I concentrations. Based on these data, we conclude that temperature, humidity and wind speed were contributing factors to variation in serum IGF-I concentrations in postweaned beef calves.
1988年4月下旬至5月初出生的8头同父异母的安格斯犊牛用于研究血清胰岛素样生长因子-I（IGF-I）浓度与光照周期以及各种天气变量之间的潜在关系，这些天气变量包括最低、最高和平均气温、相对湿度、降水量、风速和太阳辐射。为了测定IGF-I浓度，在犊牛出生时采集血样，之后每周采集一次，直至犊牛达到1月龄，此后每两周采集一次。血样采集一直持续到通过孕酮和睾酮检测确定犊牛达到青春期。光照周期和每个天气变量在采血当天及之前3天进行平均（4天平均值）。数据分为两个时期：（1）出生至断奶后期结束；（2）仅断奶后期。血清IGF-I浓度采用一个模型进行分析，该模型除了包括体重、光照周期和天气变量的协变量外，还包括性别和样本数量的固定效应、性别内犊牛的随机效应以及性别×样本数量的固定交互作用。从出生到断奶后期测试结束，当分别拟合每个天气变量或光照周期时，它们对血清IGF-I浓度均无显著影响。仅对于断奶后期，最低气温和平均气温的三次回归系数分别为0.0962±0.0325 ng/ml/℃³和0.0976±0.0272 ng/ml/℃³（P<0.01）。断奶后期相对湿度的二次回归系数为-0.2991±0.1142 ng/ml/%²（P<0.05）。断奶后期风速的四次回归系数为-36.435±13.00 ng/ml/（km/hr）⁴（P<0.01）。最高气温、降水量、太阳辐射和光照周期对断奶后血清IGF-I浓度无显著影响。基于这些数据，我们得出结论，温度、湿度和风速是断奶后肉牛犊血清IGF-I浓度变化的影响因素。
