牛性别鉴定后IVP胚胎冷冻技术研究

本实验对牛性别鉴定后IVP胚胎的冷冻方法及相关技术进行研究,目的是改善其冷冻效果,提高牛性别鉴定后IVP胚胎的移植妊娠率.实验结果如下1、性别鉴定后IVP胚胎不能用常规冷冻方法冷冻.用1.5M EG冷冻剂冷冻的胚胎,解冻培养24小时后全部死亡;用美国A、B公司特制的体内半胚胎的次冻保存.2、性别鉴定IVP胚胎用OPS玻璃化冷冻,实验表明,OPS玻璃化冷冻与鲜胚对照组体外培养没有显著差异(P＞0.05).说明OPS玻璃化冷冻牛IVP性别鉴定胚胎是可行的.     

Contract modifications and the basis behavior of live cattle futures

The purpose of this study was to assess the basis behavior of the Live Cattle Futures contract at the Chicago Mercantile Exchange (CME) before and after the 1995 contract changes. Additionally, an alternative method of basis calculation utilizing weighted mean futures prices versus settlement futures prices was compared to determine which method provides a better representation of the basis level. Within a regression model with heteroskedascity error framework, we found that the level of nearby basis in the period after June 1995 has shifted lower and the average monthly open interest of net commercial long positions has substantially increased after the contract modifications. These empirical results are consistent with the notion that more long activity entered the market in response to the contract modifications. Additionally, an alternative (new) measure of basis calculation (cash price minus weighted mean futures price) produced similar results to two other commonly used measures. In conclusion, the 1995 contract changes have neither increased nor decreased the volatility of live cattle basis. © 2004 Wiley Periodicals, Inc. Jrl Fut Mark 24:557–590, 2004     

繁殖母牛及幼牛的饲养管理

过去几年随着育种加快,牧场牛群单产水平呈大幅提高,但母牛的繁殖力也随着发生变化.尤其是高产奶牛,在产后的泌乳高峰期由于受到各种应激,表现出发情症状不明显.不发情.受胎率低及怀胎死亡等,从而导致繁殖率下降.     

繁殖母牛及幼牛的饲养管理

过去几年随着育种加快,牧场牛群单产水平呈大幅提高,但母牛的繁殖力也随着发生变化.尤其是高产奶牛,在产后的泌乳高峰期由于受到各种应激,表现出发情症状不明显.不发情.受胎率低及怀胎死亡等,从而导致繁殖率下降.