0~12月龄纯血马驹体重、体尺增长的变化分析

【目的】 研究自繁纯血马马驹0~12月各月龄段马驹体重、体尺生长情况,测定、分析体重、体尺生长和增长的变化,为自繁纯血马马驹科学饲养及科学日粮配方提供数据依据。【方法】 选择2019年3月出生,平均体重(51.00±6.27) kg的纯血马马驹40匹,公母各20匹,按照性别分为公驹组和母驹组,进行为期12个月的饲养监测试验。所有试验马驹在相同的饲养条件下进行,日粮组成及营养水平一致,按期测定马驹体重和体尺指标,并利用Logistic非线性生长曲线模型对0~12月龄纯血马驹体尺、体重数据进行拟合和分析。【结果】 (1)随着月龄的增长,马驹的体重、体尺均呈极显著性增加。公驹体重、体斜长和胸围极显著高于母驹,分别比母驹提高了6.59%(P<0.01)、2.62%(P<0.01)和2.28%(P<0.01),体高和管围显著高于母驹,分别比母驹提高了1.05%(P<0.05)和1.22%(P<0.05);(2)体重、体高、胸围及管围各阶段总增长和平均日增长公驹与母驹之间差异不显著(P>0.05),体斜长0~6月龄阶段公驹总增长和平均日增长极显著高于母驹,分别比母驹提高了29.02%(P<0.01)和27.78%(P<0.01),在整个试验期间,公驹体斜长总增长和平均日增长均要高于母驹;(3)马驹的体重、体尺生长曲线拟合度均在0.93以上,尤其是体重、体高和胸围的拟合度,公驹和母驹分别达到了0.973 3、0.982 4,0.970 2和0.963 3、0.970 1、0.981 6,生长曲线模型拟合度较好。【结论】 马驹随着月龄的增加在增长,公驹的体重、体尺较母驹生长快,且在断奶前增长更明显。Logistic模型能较好的拟合0~12月龄纯血马驹体重、体尺的生长曲线。     

Estimation of heritability and genetic correlation for behavioural responses by Gibbs sampling in the Thoroughbred racehorse

Genetic variation of the behaviour of racehorses is one of the major concerns for racehorse breeders. In this study, the heritabilities of behavioural responses to the inspections of conjunctiva, auscultation and blood sampling and the genetic correlations among them were estimated in the Thoroughbred racehorse. The estimation was done with Bayesian analysis with Gibbs sampling based on the univariate or bivariate threshold animal models. The behavioural responses were scored with four categories at the first entrance quarantine in Miho Training Center of Japan Racing Association from 1993 to 1995. The behavioural responses were treated as categorical or binary traits, with both showing similar results. The estimated heritabilities were in the range of 0.23–0.28, suggesting a genetic component in the variation on these traits. The estimated genetic correlations among the traits were very high (approximately 0.9), suggesting that these behavioural responses may be measures of the same trait. Because of the high genetic correlations, repeatability threshold model was applied assuming the responses to be a genetically identical trait measured with three different tests. The estimated heritabilities (approximately 0.23) were at the lower bound of the former estimates. The revealed high repeatabilities (0.97–0.98) suggest a strong contribution of the individual temperament on the behaviour of racehorses.     

Estimation of dietary lysine requirement using plasma amino acid concentrations in mature thoroughbreds

Four experiments were conducted to estimate dietary lysine (Lys) requirements using plasma amino acid concentrations as a criterion in mature thoroughbreds. In each experiment four adult thoroughbreds were used. The changes in plasma Lys concentration after feeding were observed in Experiment 1. Blood samples were taken from the cervix vein 0.5 h before, and 1, 3, 5.5, and 10 h after feeding. The plasma Lys concentration increased and remained constant until 3 h after feeding, decreased until 5.5 h and remained constant after then. Therefore, the bleed was done at 3 h after feeding in all later experiments. To make sure of the response speed of the plasma Lys to changes of dietary Lys levels, dietary Lys levels were changed from high to low, and low to high levels in Experiment 2. Blood samples were taken just on the changing day and 1, 2 and 3 days after changing diets. The plasma Lys concentration decreased until 2 days after changing the diet, and then remained constant with advancing days after changing the diet from high Lys to low Lys. On the other hand, the plasma Lys increased until one day after changing the diet, and then remained constant with advancing days after changing dietary Lys levels. Thus, blood samples were taken 3 days after feeding in the next experiments. The possibility of estimating the Lys requirement for maintenance using plasma Lys concentration was elucidated by two methods in Experiments 3 and 4. In Experiment 3, the horses were fed a diet containing 0.33 percent Lys for 3 days. After this the diet was changed to diets containing higher levels of Lys to 0.40, 0.47, 0.54, and 0.61 percent every third day. The Lys requirement was estimated to be 0.46 percent of diet from the response of plasma Lys concentration of five Lys levels. In Experiment 4, a 4 × 4 Latin square design was used for four dietary Lys levels. The Lys requirement was estimated to be 0.47 percent of the diet with a plasma Lys concentration of four Lys levels.