秦川牛部分体量性状的遗传参数估测

本研究选用陕西秦川牛原种场饲养的33头公牛及其603头女儿1978年至2005年的记录资料,采用父系半同胞相关法对秦川牛初生、断奶、周岁及18月龄体重、体高、体长、胸围及体重体高比(BPI)的遗传力进行了统计分析,同时分析了各年龄段体重与体尺的相关性。结果表明,秦川牛初生重、断奶重、周岁重及18月龄体重的遗传力分别为0．4150、0．6136、0．2008和0．6371。同期体重体高比(BPI)的遗传力值为0．6225、0．6464、0．1632和0．4839。各年龄段体重与其它体尺性状均呈较强的正相关。     

羊近交衰退的研究进展

近交衰退是动物育种中必须考虑的因素之一。文章介绍了近交衰退产生的机制,以及近交对羊繁殖性状、生长性状和绒毛性状影响的研究进展。分析发现,除了绒毛品质(长度和细度)外,近交对所有分析性状均产生不利影响。近交显著降低母羊繁殖力和羔羊存活率,同时随着近交的增加,母羊产羔性能也略有下降,羔羊初生重、断奶重、2月龄体重、3月龄体重、6月龄体重、9月龄体重及周岁重均表现出不同程度的衰退。近交增加到一定程度后,对产绒量有不利效应,但对绒毛长度和细度无显著影响。     

秦川牛保种群的群体分析

<正> 1 材料与方法1.1 群体及饲养管理以陕西省秦川牛场秦川牛保种群作分析对象。该场秦川牛保种群组建于60年代,已有30多年的保种历史。群体规模在年度间有一定波动,从1965～1990年期间母牛群平均每年在群61.1±17.8头。后备母牛主要靠自繁,迁入量甚小,后备公牛及繁殖公牛有相当部分由群外迁入(防止近交)。虽然该牛群为指定保仲群,但仍进行选育,选择性状主要是初生重、断奶重及毛色等。母牛的淘汰有多种原因,主要是空怀、不孕及疾病。另有部分母牛因生产性能低或缩群需要而被出售。1.2 种群统计分析     

利木赞牛改良秦川牛效果初报

陕西岐山农村开展利木赞牛杂交改良秦川牛,已配母牛２２３０头,已产犊１０００多头。犊牛初生重公犊平均３１．３ｋｇ,母犊平均为３０．４ｋｇ,分别比当地秦川牛犊高出２６．７％和２５．１％;６月龄体重公犊１７２．６ｋｇ,母犊１５８．９ｋｇ,分别比当地秦川牛高出２２．７％和２５．９％。说明用利木赞牛改良秦川牛效果明显。     

圩猪近交的探讨

本文着重阐述圩猪近交选育的可能性。先后观察了109头220窝近交系数分别为0.0625～0.40625等七个不同水平的近交效果,在产活仔数、断奶窝重等主要繁殖性状方面,一般没有衰退,既或混群饲养,45窝近交经产的平均产活仔数及断奶窝重比86窝非近交的分别提高8.86%及11.25%,近交后未出现严重遗传疾患,生活力亦未见衰退,与非近交相比死胎率微微上升(+0.09%P>0.05),哺乳期仔猪死亡率略有下降(-1.38%P>0.05),2～6月龄后备阶段的生长发育,未受影响。     

蓝塘猪高度近交研究

蓝塘猪属典型的华南型猪种，具有十分优良的遗传稳定性。通过本场试验，在近变系数这26．70％的情况下，对本品种特征、母猪的繁殖力、仔猪的初生重以及成活率无不良反应，不会因为近交而出现品种衰退现象，具有高度耐近交的特性。     

近交对黑白花奶牛生长发育及繁殖性能影响的研究

据78头黑白花奶牛资料计算各个体近交系数,并分为12.50、6.25、3.125、1.5625和0%五个水平组,分别统计各组牛的初配日龄、1—5胎产后空怀期、产犊间隔、妊娠配种次数、分娩正产率、初生及一胎的体重体尺。各水平组均与0%组作方差分析比较。试验结果表明:12.5%组牛的初生体重、体高、胸围、管围均显著较低,分别比非近交     

新疆褐牛近交群体的鉴定研究

试验旨在检测新疆褐牛近交群体的遗传相似性和群体的纯合度。利用13对微卫星引物对由2头新疆褐牛经40年完全封闭繁育出的55头新疆褐牛近交群体和25头对照组新疆褐牛的遗传结构特征进行了比对分析,以期开展对近交群体的鉴定研究。结果发现,新疆褐牛近交群体的纯合度为0.9064,多态信息含量为0.0873,可知该群体具有低多态性;对照组新疆褐牛的纯合度为0.4647,多态信息含量为0.4882。将该近交群体按毛色分为4个亚群:A、B、C和D,各亚群的遗传纯合度分别为0.9029、0.9632、0.9208和0.9551。结果表明受检测的新疆褐牛近交群体有较高的纯合度和很低的杂合性,已成为遗传纯度很高的近交群体。该封闭的近交新疆褐牛群体是中国牛品种中难得、宝贵的遗传资源。     

奶牛公犊与秦川牛公犊饲喂比较试验

[目的]相同饲养条件下,比较奶牛公犊与秦川牛公犊增重效果.[方法]将20头荷斯坦公犊牛与20头秦川牛公犊分为试验组和对照组,进行饲养试验,日粮组成和饲喂方法相同,青贮饲料和干草自由采食.[结果]奶牛公犊比秦川牛公犊生长速度快,饲料报酬高,奶牛公牛的初生重、6月龄平均体重、12月龄平均体重、18月龄平均体重、24月龄平均体重比秦川牛公牛高.[结论]饲养奶牛公犊比饲养秦川牛公犊的经济效益更好.     

窝产活仔数和初生重与仔猪早期断奶重及成活率的相关性研究

为研究猪窝产活仔数与初生仔猪个体重对21日龄早期断奶仔猪个体重及成活率的相关性,特选择一大型规模猪场2~6胎母猪在1个月内所产的118窝计1350头仔猪作为试验对象,要求所有初生仔猪均由亲本母猪带仔哺乳,且按窝产活仔数不同(6~17头)分组测定仔猪初生个体重和21日龄早期断奶仔猪窝个体均重,并观察断奶成活率,同时对其相关性状作方差及回归分析。结果表明,不同组间初生仔猪窝个体均重和21日龄早期断奶仔猪窝个体均重及断奶成活率差异显著(P0.05);窝产活仔数对初生仔猪窝个体均重和21日龄早期断奶仔猪窝个体均重及断奶成活率呈极显著的负相关(R=-0.802、-0.851、-0.698,P0.01);初生仔猪窝个体均重对21日龄早期断奶仔猪窝个体均重及断奶成活率呈极显著的正相关(R=0.837、0.741,P0.01)。试验结果表明,窝产活仔数越多,初生仔猪个体就越小,早期断奶也越轻,成活率也低;初生仔猪个体越大,早期断奶就越重,成活率也越高。只要通过科学合理的方法,适当控制猪窝产活仔数并提高初生仔猪个体重,能有效提高早期断奶仔猪的生长速度,并可获得更好的经济效益。     

Simulated efficiency of range beef production. I. Growth and milk production

A revised version of the Texas A&M University Beef Cattle Production Model was used to simulate the effects of growth, milk production and management system on biological and economic efficiency of beef production in a northern plains, range environment. Animals varying in genetic potential for birth weight (BWA), yearling weight (YW), mature weight (WMA) and milk production (PMA) were simulated under both a weanling system of management (weaned calves custom-fed in the feedlot) and a yearling system (calves wintered on the ranch, then custom-fed after their second summer). The yearling system of management was biologically less efficient, but economically more efficient than the weanling system due primarily to heavier slaughter weights of fed animals. The advantage of the yearling system was most apparent for smaller genotypes. Herd efficiency improved with decreased BWA and increased YW, but changed little when WMA was varied while other growth traits were held constant. Increased PMA was favored for production of live weight at weaning and for production of slaughter product when feedlot costs were high. Increased PMA was not favored when feed costs for the cow herd were high. Economic weights generated from the simulation indicated the importance of selection for rapid early growth followed by selection for lighter birth weight. While larger genotypes were generally favored in this study, optimal cow size depended on economic conditions. Larger types were more biologically efficient and more economically efficient using standard costs, but medium- and small-size cattle were more efficient when feedlot costs were high. Small cattle were least efficient when feed costs for the cow herd were high.     

Effects of inbreeding and heterosis in Hereford females on fertility, calf survival and preweaning growth

Effects of inbreeding and heterosis and the difference between them were estimated by comparing linecross (L), topcross (T), inbred (I) and control line (C) Hereford females for reproductive and preweaning growth traits of their progeny. Inbred females (average inbreeding coefficient = 26.5%) originated from four single-sire inbred lines. Control females (average inbreeding coefficient = 6.9%) were produced by a four-sire, 60-cow line. Linecross females were produced from all possible reciprocal crosses of the I lines. Topcross females were produced by mating I bulls to C cows. Differences in pregnancy rate among these lines were not detected. Effects of maternal heterosis were positive for both prenatal and postnatal survival. The weaning rate by L females exceeded the weaning rate by I females as a result. Prenatal survival was reduced in calves from I females relative to those from C females, resulting in corresponding differences in birth and weaning rates. Differences in the magnitudes of maternal heterosis and inbreeding effects were not detected, except for birth weight. For birth weight the effect of maternal inbreeding was of greater magnitude than the effect of maternal heterosis. Within the I and C lines regressions of pregnancy rate, prenatal survival, birth rate, postnatal survival, weaning rate, weaning weight/cow exposed, birth weight and weaning weight on the inbreeding coefficients of the cows indicated significant inbreeding depression on all traits except pregnancy rate and postnatal survival.     

牛胚胎移植试验及其后代生长发育指标测定

为探讨牛胚胎移植受胎率、产犊成活率及后代生长发育情况,互助县先后从新疆呼图壁种牛场胚胎工程中心引进不同品种牛冷冻胚胎93枚,进行了胚胎移植试验.结果表明：平均受胎率为45.16%,产犊成活率为90.48%.黑白花、西门塔尔、利木赞、安格斯犊牛平均初生重为40.77,42.50,47.41,39.13,分别比同龄本地牛提高71.82%,79.10%,99.79%,64.90%;六月龄平均体重分别为116.74,123.36,134.15,120.49,分别比同龄本地牛提高64.80%,74.13%,89.37%,70.09%;12月龄体重分别为253.31,289.91,302.73,271.35,分别比同龄本地牛提高75.18%,100.51%,109.36%,87.66%;1周岁平均日增重分别为582.30g,677.84g,699.50g,636.22g.胚胎移植后代牛的生长发育较本地牛快.     

MIM: an indirect method to assess inbreeding and coancestry in large incomplete pedigrees of selected dairy cattle

In real data, inbreeding is usually underestimated because of missing pedigree information. A method adapted to the dairy cattle situation is presented to approximate inbreeding when the stored population pedigree is incomplete. Missing parents in incomplete pedigrees were given a dummy identification and assigned to groups (up to nine for a given birth date of progeny). These groups were linked to contemporary reference groups with known parents. An explicit model considered that polygenic breeding values in a censored group were centred on a function of the average breeding value in the corresponding reference group and deviated independently. Inbreeding coefficients were obtained progressively over birth dates starting from founders. For each date considered, the parameters pertaining to its groups were computed using the parameters already obtained from groups belonging to the previous dates. The updating algorithms were given in detail. An indirect method was implemented to expedite mass computations of the relationship coefficients involved (MIM). MIM was compared to Van Raden's (VR) method using simulated populations with 20 overlapping generations and different rates of missing sires and dams. In the situation of random matings, the average inbreeding coefficients by date obtained by MIM were close to true values, whereas they were strongly underestimated by VR. In the situation of assortative matings, MIM gave average inbreeding coefficients moderately underestimated, whereas those of VR's method were still strongly underestimated. The main conclusion of this study adapted to the situation of dairy cattle with incomplete pedigrees was that corrections for inbreeding and coancestry coefficients are more efficient with an explicit appropriate genetic model than without.     

关于选种选配中避免近交的几点建议

本文阐述了在种选配计划中，应使交配双方距共同祖先的总代数在六代以上，避免近亲交配，将近交系数严格控制在４％以下，才能有效防止牛群品质退化，提高牛群整体生产水平，获取最佳效益。     

Sahiwal cattle in semi-arid Kenya: genetic aspects of growth and survival traits and their relationship to milk production and fertility

The aim of this study was to estimate genetic and phenotypic parameters for growth and survival traits of Sahiwal cattle in Kenya and determine their relationship to milk production and fertility. Performance records of 5,681 animals were obtained from the National Sahiwal Stud and the traits considered were: birth weight (kilogrammes), weaning weight (kilogrammes), pre-weaning average daily gain (grammes per day), post-weaning average daily gain (grammes per day), yearling weight (kilogrammes), mature weight at 36 months (kilogrammes), pre-weaning survival rate (SR), post-weaning survival rate (PSR), lactation milk yield (kilogrammes), age at first calving (days), and calving interval (days). The data was analysed using univariate and bivariate animal model based on restricted maximum likelihood methods, incorporating all known pedigree relationship among animals. The additive direct effects were more pronounced than maternal genetic effects in early and in post-yearling growth performance. The additive genetic variance and heritabilities were low for SR and PSR. The correlation between direct additive genetic and maternal genetic effect were negative for pre-yearling traits. Genetic and phenotypic correlations among growth traits and between growth and milk yield were positive, whilst those between growth and fertility were weak and negative. Correlations between survival and growth were generally low and positive. The estimates obtained in this study provide the necessary technical parameters for evaluating alternative breeding programmes and selection schemes for sustainable improvement of Sahiwal cattle.     

Characteristics of Line 1 Hereford females resulting from selection by independent culling levels for below-average birth weight and high yearling weight or by mass selection for high yearling weight

Simultaneous selection for low birth weight and high yearling weight has been advocated to improve efficiency of beef production. Two sublines of Line 1 Hereford cattle were established by selection either for below-average birth weight and high yearling weight (YB) or for high yearling weight alone (YW). Direct effects on birth weight and yearling weight diverged between sublines with approximately four generations of selection. The objective of this study was to estimate genetic trends for traits of the cows. A three-parameter growth curve [Wt = A(1 - b0e(-kt))] was fitted to age (t, d)-weight (W, kg) data for cows surviving past 4.5 yr of age (n = 738). The resulting parameter estimates were analyzed simultaneously with birth weight and yearling weight using multiple-trait restricted maximum likelihood methods. To estimate maternal additive effects on calf gain from birth to weaning (MILK) the two-trait model previously used to analyze birth weight and yearling weight was transformed to the equivalent three-trait model with birth weight, gain from birth to weaning, and gain from weaning to yearling as dependent variables. Heritability estimates were 0.32, 0.27, 0.10, and 0.20 for A, b0, k, and MILK, respectively. Genetic correlations with direct effects on birth weight were 0.34, -0.11, and 0.55 and with direct effects on yearling weight were 0.65, -0.17, and 0.11 for A, b0, and k, respectively. Genetic trends for YB and YW, respectively, were as follows: A (kg/generation), 8.0+/-0.2 and 10.1+/-0.2; b0 (x 1,000), -1.34+/-0.07 and -1.16+/-0.07; k (x 1,000), -14.3+/-0.1 and 4.3+/-0.1; and MILK (kg), 1.25+/-0.05 and 1.89+/-0.05. Beef cows resulting from simultaneous selection for below-average birth weight and increased yearling weight had different growth curves and reduced genetic trend in maternal gain from birth to weaning relative to cows resulting from selection for increased yearling weight.     

Estimation of genetic parameters among reproductive and growth traits in yearling heifers

Growth and reproductive data were obtained on 779 beef heifers at the San Juan Basin Research Center, Hesperus, Co. Genetic parameters were estimated for age of puberty (AOP), age of first calving (AOC), julian day of first calving (DOC), julian day of second calving (DOSC), birth weight, weaning weight, yearling weight, and average daily gain from weaning to yearling and to cycling weights. The least squares model included birth year, age of dam and breed as fixed effects, sire/breed as a random variable, and day of birth and percent inbreeding as covariates. Day of birth was not included in the analyses of AOC, DOC or DOSC. Paternal half-sib estimates of heritability were: AOP, .10 +/- .17; AOC, .01 +/- .12; DOC, .09 +/- .13 and DOSC, .36 +/- .18. Genetic and phenotypic correlations were generally favorable, but genetic correlations were variable with large standard errors. Inbreeding had a detrimental effect on reproductive traits, and a seasonal effect was present for AOP.     

Inbreeding depression on production and reproduction traits of buffaloes from Brazil

The objective of this study was to evaluate the influence of inbreeding depression on traits of buffaloes from Brazil. Specifically, the traits studied were body weight at 205 and 365 days of age, average daily gain from birth to 205 days (ADG_205), average daily gain between 205 and 365 days (ADG205_365) in Mediterranean buffaloes, and milk yield, lactation length, age of first calving and calving intervals in Murrah buffaloes. Inbreeding effects on the traits were determined by fitting four regression models (linear, quadratic, exponential and Michaelis‐Menten) about the errors generated by the animal model. The linear model was only significant (P < 0.05) for growth traits (exception of ADG205_365). The exponential and Michaelis‐Menten models were significant (P < 0.01) for all the studied traits while the quadratic model was not significant (P > 0.05) for any of the traits. Weight at 205 and 365 days of age decreased 0.25 kg and 0.39 kg per 1% of increase in inbreeding, respectively. The inbred animals (F = 0.25) produced less milk than non‐inbred individuals: 50.4 kg of milk. Moreover, calving interval increased 0.164 days per 1% of increase in inbreeding. Interestingly, inbreeding had a positive effect on age at first calving and lactation length, decreasing age of first calving and increasing lactation length.