Koivisto M B, Costa M T A, Perri S H V, Vicente W R R
Veterinary Medicine, FOA, São Paulo State University, Araçatuba, SP, Brazil.
Reprod Domest Anim. 2009 Aug;44(4):587-92. doi: 10.1111/j.1439-0531.2008.01023.x. Epub 2008 Dec 15.
The objectives of this study were to evaluate the effects of season in southeast of Brazil comparing genotypes on semen characteristics, freezability and peripheral plasma concentrations of testosterone. Ejaculates of five Bos indicus bulls and six Bos taurus bulls were evaluated over a period of 27 months, which was divided into winter (July, August, September), spring (October, November, December), summer (January, February, March) and autumn (April, May, June). Semen was evaluated according to standard procedures for ejaculate volume, sperm concentration, gross-motility, progressive motility and sperm morphology. After preparing and freezing the ejaculates according to commercial procedures, the straws were stored in liquid N(2) until post-thaw evaluation. Ejaculate volume, sperm concentration, gross-motility, progressive sperm motility, vigor and morphological sperm defects were significantly influenced by season and genotype (p < 0.05). Heat tolerance was better in B. indicus bulls than in B. taurus bulls characterized by lower values of sperm abnormalities throughout the observation period. The highest values were recorded for abnormal heads followed by cytoplasmatic droplets in B. taurus bulls. The proportion of ejaculates which were eliminated before freezing for reasons of bad quality was lower in the B. indicus bulls. Temporal changes in peripheral plasma testosterone concentrations were higher in B. indicus bulls than in B. taurus bulls not revealing seasonal influences. The results of this study show clear genotype differences regarding semen quality. Freezability of B. taurus semen varies considerably throughout the year, leading to a high proportion of eliminated ejaculates. Collecting semen from B. taurus bulls during the summer in an artificial insemination centre may not be profitable.
本研究的目的是评估巴西东南部季节对基因型在精液特征、冷冻保存能力和外周血睾酮浓度方面的影响。对5头印度瘤牛公牛和6头欧洲牛公牛的射精进行了为期27个月的评估，该时间段分为冬季（7月、8月、9月）、春季（10月、11月、12月）、夏季（1月、2月、3月）和秋季（4月、5月、6月）。根据射精量、精子浓度、总活力、前向运动能力和精子形态的标准程序对精液进行评估。按照商业程序制备并冷冻射精后，吸管保存在液氮中直至解冻后评估。射精量、精子浓度、总活力、前向精子运动能力、活力和精子形态缺陷受季节和基因型的显著影响（p<0.05）。在整个观察期内，印度瘤牛公牛的耐热性优于欧洲牛公牛，其精子异常值较低。欧洲牛公牛中头部异常的比例最高，其次是细胞质滴。因质量差在冷冻前被淘汰的射精比例在印度瘤牛公牛中较低。印度瘤牛公牛外周血睾酮浓度的时间变化高于欧洲牛公牛，未显示出季节性影响。本研究结果表明在精液质量方面存在明显的基因型差异。欧洲牛精液的冷冻保存能力全年变化很大，导致大量射精被淘汰。在人工授精中心夏季从欧洲牛公牛采集精液可能无利可图。
