奶牛性控冻精低剂量人工授精技术规范

奶牛性别控制繁育技术是继常规人工授精和胚胎移植之后,家畜繁育改良技术的第三次革命.由于性控冻精自身特点,在人工授精操作上与常规冻精输精略有不同,为了提高奶牛性控冻精受胎率和利用效率,节省成本,本规程对奶牛性控冻精低剂量深部人工授精技术环节进行了规范和要求.     

奶牛小区实施同期发情后应用性控冻精人工授精的效果观察

为观察奶牛养殖小区应用同期发情后,实施性控冻精人工授精的效果进行试验。结果表明：发情率为87．5％,而且92．9％的发情牛集中在20h之内,并获得了58．％的情期受胎率;≥17月龄的参配育成牛的妊娠率（83．3％）明显高于〈17月龄的参配牛的妊娠率（33．3％）,差异显著（P〈0．05）;输精到排卵侧子宫角的妊娠率（62．5％）高于输精到子宫体的妊娠率（50．0％）,但差异不显著（P〉0．05）;发情后长时间（超20h）不排卵,可以肌肉注射促排卵素3号25μg／头,然后输精,可提高妊娠率。     

重庆市奶牛性控冻精应用效果观察

本文通过总结重庆市2006～2009年期间,在三个奶牛场使用1 300剂性控精液配种效果观察,分析并总结了奶牛性控精液在生产中的配种效果及经济效益,为奶牛性控精液能否在生产中大面积的推广应用提供了依据。从重庆市几年的应用情况看,用奶牛性控冻精给母牛配种,一次情期受胎率平均为54.23%,比普通精液一次情期受胎率低3.2个百分点;性控冻精配种产母犊率为92.5%,显著高于普通精液配种的49.5%。性控冻精配种母牛受胎率虽低于普通冻精配种,但产母犊率显著高于普通冻精,产犊收益既高于普通精液,又能达到快速扩群和选育的目的,值得推广应用。性控冻精精子含量少,对配种技术要求高,可在有配种技术高的人工授精人员的大中型奶牛场推广应用,不宜在小规模场和散养户中使用。     

大通县应用奶牛性控冻精人工授精对比试验

本试验对荷斯坦奶牛性控精液和常规精液人工授精效果以及性控精液对青年牛和经产牛配种的效果进行了比较分析。结果表明,采用性控精液(200万个/0.25mL)人工授精的受胎率为63.9%,第一情期受胎率58.2%;采用常规精液(1000万个/0.25mL)人工授精的受胎率为81.5%,第一情期受胎率67.1%,性控精液和常规精液差异不显著(P0.05),用性控精液人工授精,青年牛受胎率74.4%,经产牛受胎率55.6%,差异不显著(P0.05)。     

性控精液人工授精在奶牛生产中的应用

通过流式细胞仪分离XY精子进行人工授精，是目前最准确、有效、简易的控制奶牛性别的方法。本文介绍了性控精液技术的发展简史，XY精子分离的理论基础和方法，奶牛性控精液人工授精的应用效果，提高性控精液应用效率的措施以及推广性控精液人工授精的意义、技术障碍和发展前景。     

性控精液人工授精在奶牛生产中的应用

通过流式细胞仪分离XY精子进行人工授精,是目前最准确、有效、简易的控制奶牛性别的方法。本文介绍了性控精液技术的发展简史,XY精子分离的理论基础和方法,奶牛性控精液人工授精的应用效果,提高性控精液应用效率的措施以及推广性控精液人工授精的意义、技术障碍和发展前景。     

性控精液人工授精在奶牛生产中的应用

通过流式细胞仪分离XY精子进行人工授精,是目前最准确、有效、简易的控制奶牛性别的方法。本文介绍了性控精液技术的发展简史,XY精子分离的理论基础和方法,奶牛性控精液人工授精的应用效果,提高性控精液应用效率的措施以及推广性控精液人工授精的意义、技术障碍和发展前景。     

奶牛性控冻精人工授精技术要点

1受配牛的选择参配牛必须是营养均衡、体况适宜、无生殖系统等疾病的健康牛。最好选择青年牛,健康经产牛亦可。2发情鉴定奶牛的发情可分为发情前、中、后期。发情周期平均21 d,发情持续时间2～4 d。     

奶牛性控冻精及改进型输精枪人工授精对比试验

试验通过比较荷斯坦奶牛常规精液和性控精液人工授精效果、性控精液对青年牛和经产牛人工授精的效果以及改进型输精枪与通用输精枪输精效果,分析了第一情期受胎率。结果表明：采用性控精液受胎率62．2％,采用常规精液人工授精受胎率80％,性控精液和常规精液差异显著（P〈0．05）;同用性控精液人工授精,青年牛（受胎率75％）与经产牛（受胎率57．6％）差异显著（P〈0．05）;用改进型输精枪第一情期受胎率70％,通用输精枪第一情期受胎率55％,差异显著（P〈0．05）。     

奶牛性控冻精应用研究

应用奶牛性控冻精进行人工授精,探讨其情期受胎率、母犊率与常规冻精的差别,以及其不同年龄与配母牛、不同输精时间、不同输精部位与情期受胎率之间的关系,为大规模推广应用提供科学依据.结果:1、奶牛性控冻精人工授精的情期受胎率为56.6%(3020/5335),与普通冻精的情期受胎率59.1%(1328/2246)相比差异不显著(P>0.05),奶牛性控冻精的母犊率为93%(1922/2067),极显著高于普通冻精48.8%(63/129)的母犊率(P<0.001);2、应用性控冻精,青年牛的情期受胎率为69.0%(2333/3382),显著高于经产牛49.2%(961/1953)的情期受胎率(P<0.05);与配母牛 发情开始后18～24h输精,其情期受胎率为56.8%(2255/3970),显著高于发情开始后8～12h输精46.1%(629/1365)的情期受胎率(P<0.01):单侧子宫角深部输精,情期受胎率为56.6%(2886/5099),显著高于双侧子宫角输精45.3%(107/236)的情期受胎率(P<0.05).结果表明:1、性控冻精与普通冻精的情期受胎率无差异,可以规模化推广;2、性控冻精输精母牛情期受胎率的高低与母牛的经产与否、输精时间和输精部位有直接相关性.     

Genetic gain in dairy cattle populations is increased using sexed semen in commercial herds

Using stochastic simulation, the effect of using sexed semen to cow dams (CD) in a dairy cattle breeding scheme, with or without use of multiple ovulation and embryo transfer (MOET) to bull dams (BD), on annual genetic gain at the population level was examined. Three levels of sexed semen were combined with three levels of MOET: no sexed semen, sexed semen to the best CD and sexed semen to all heifers, combined with no MOET, MOET on all BD and MOET randomly on 20% of the BD. In total, nine scenarios were compared. The simulated population was monitored for 30 years and included 450 herds with 100 cows each. Each year 50 young bulls (YB), 10 active sires and 215 BD were selected on best linear unbiased prediction estimated breeding values by truncation selection across the simulated population, and the YB were tested within the population. Use of sexed semen alone gave a positive increase in the annual genetic gain of 2.1% when used on the best CD and 2.7% when used on all heifers, but only the latter was statistically significant. The increased annual genetic gain was caused by a larger contribution from the CD to the BD. Use of sexed semen together with MOET on BD increased the annual genetic gain by 1.8-2.5% compared with schemes without sexed semen and MOET on all BD. Performing MOET on all BD enables selection of offspring with high Mendelian deviations, which increase the annual genetic gain. Use of sexed semen decreased the genetic lag between the sires and the CD by 12-14% when used on the best CD and by 6% when used to all heifers. The decrease in the genetic lag is caused by the increased selection intensity of the cow dams.     

Genomic selection strategies in dairy cattle breeding programmes: Sexed semen cannot replace multiple ovulation and embryo transfer as superior reproductive technology

The aim of this study was to test whether the use of X-semen in a dairy cattle population using genomic selection (GS) and multiple ovulation and embryo transfer (MOET) increases the selection intensity on cow dams and thereby the genetic gain in the entire population. Also, the dynamics of using different types of sexed semen (X, Y or conventional) in the nucleus were investigated. The stochastic simulation study partly supported the hypothesis as the genetic gain in the entire population was elevated when X-semen was used in the production population as GS exploited the higher selection intensity among heifers with great accuracy. However, when MOET was applied, the effect was considerably diminished as was the exchange of females between the nucleus and the production population, thus causing modest genetic profit from using X-sorted semen in the production population. In addition, the effect of using sexed semen on the genetic gain was very small compared with the effect of MOET and highly dependent on whether cow dams or bull dams were inseminated with sexed semen and on what type of semen that was used for the bull dams. The rate of inbreeding was seldom affected by the use of sexed semen. However, when all young bull candidates were born following MOET, the results showed that the use of Y-semen in the breeding nucleus tended to decrease the rate of inbreeding as it enabled GS to increase within-family selection. This implies that the benefit from using sexed semen in a modern dairy cattle breeding scheme applying both GS and MOET may be found in its beneficial effect on the rate of inbreeding.     

Economic effects of using sexed semen in Japanese dairy herds

Dairy farm agricultural income should increase when sexed semen is used instead of unsexed semen. This study simulated three scenarios: using unsexed semen (N), using X sperm of Holstein and unsexed semen of Japanese Black (H), and using X sperm of Holstein and Y sperm of Japanese Black (HJ). Two management scenarios were considered: conventional management (CONV); and the use of Japanese Black semen with surplus cows to produce F₁s where sufficient replacement female Holstein calves were obtained for maintenance (MAINT). In CONV, the agricultural incomes of H and HJ were 610 000–2 400 000 yen higher than that of N. The agricultural income increased when the difference in the prices between Holstein males and average F₁ male/female calves was 34 000–50 000 yen, that between Holstein male and female calves was 80 000–110 000 yen, and that between F₁ male and female calves was 50 000–90 000 yen. Therefore, the agricultural income can be increased by using sexed semen to select calves of a more valued breed and sex.     

Addition of oxytocin to semen extender improves both sperm transport to the oviduct and conception rates in pigs following AI

Oxytocin (OXT) contained in boar semen is known to produce uterine contraction; therefore, we hypothesized that the co‐injection of OXT with sperm would improve artificial insemination (AI) using liquid or frozen‐thawed boar sperm. We initially examined whether OXT added to semen extender improved sperm transport to the oviduct. Although the addition of OXT did not affect the fresh or frozen‐thawed sperm motility or acrosomal integrity, it significantly increased the number of sperm in the oviduct at 6 h after AI injection with OXT, as compared with the control (P < 0.05). Moreover, some sperm were observed in the sperm reservoir of the isthmus in the OXT treatment group, whereas few sperm were observed in the control. When OXT was added to the semen extender immediately prior to AI, the conception rates were significantly higher in both fresh semen and frozen‐thawed semen than in the control group (P < 0.05: liquid, 87.5% vs. 70.5%; frozen‐thawed, 89.8% vs. 75.0%). From these results, we concluded that the addition of OXT to the semen extender assisted in sperm transportation from the uterus to the oviduct, which resulted in improved reproductive performance.     

Effect of replacement rate,crossbreeding and sexed semen on the efficiency of beef production from dairy herds in Finland

Abstract

In Finland, during the past 10 years, the number of dairy cows has declined considerably leading to decreased domestic beef production which is partly compensated by increased suckler beef production. However, production of meat originating from dairy herds has been shown to be economically more profitable and to produce less greenhouse gas emissions per unit of product than beef production from suckler cow systems. Therefore, when safeguarding beef self-sufficiency, the intensification of beef production from dairy herds is a more promising option to consider. In this study, the possibility of different options for increasing dairy beef production was assessed by using a deterministic simulation. Increasing the use of crossbreeding in dairy herds, especially when combined with the use of Y-sorted semen, appeared to be the most efficient strategy for increasing dairy beef production. The decrease in the replacement rate increased beef production through the potential for enhancing crossbreeding.     

Environmental and maternal factors associated with gross placental morphology in dairy cattle

This article reports on a study of gross placental morphology of 282 expelled placentas from 89 primi‐ and 193 multiparous Holstein dams immediately after calving and examines associations with environmental factors such as typical herd features and season of calving, and maternal factors such as age at calving, level of milk yield at conception and cumulative amount of milk produced during gestation. The highest correlation between calf measurements and placental characteristics was found between the weight of the calf and the total cotyledonary surface (r = .643; p < .001), confirming the high importance of the cotyledonary surface available for nutrient transfer to the developing foetus. Younger age in adolescent and smaller heart girth in multiparous dams were associated with a higher cotyledon number, suggesting placental compensation in dams with lower capacities in terms of dry matter intake. No significant association between milk yield during gestation in multiparous animals and gross placental morphometrics could be detected, indicating that factors such as the amount of milk produced during gestation affect placental development less than foetal weight close to term. Therefore, placental growth may be sustained at the expense of other tissues in an attempt to maintain pregnancy and minimize the adverse consequences for the foetus. This study offers evidence concerning factors affecting the placental surface size for nutrient transfer from dam to calf in dairy cattle based on gross morphometrics, but needs confirmation from studies in which this surface size is more profoundly assessed by measuring the branches present in the cotyledonary villi.     

Studies of gel with immobilized semen by intrauterine endoscopy post-artificial insemination

An extended lifespan of spermatozoa following artificial insemination (AI) can make the timing of insemination less critical, as previously demonstrated with immobilized spermatozoa that are gradually released from an alginate gel. The purpose was to examine the in vivo dissolution of SpermVital (SV) alginate gel over time by endoscopy and secondly to assess spermatozoa quality after incubation of the gel. In vivo endoscopy showed SV gel in the uterus 3, 6, 20 and 24 hr after AI, demonstrating the potential release of spermatozoa to the uterus during this period. In utero ex vivo incubation of the semen demonstrated that high motility and viability of sperm cells was sustained following overnight incubation.