绵羊第6号染色体微卫星标记的研究进展

微卫星标记是目前应用广泛的分子遗传标记技术,其在绵羊遗传育种中有着十分重要的作用。通过国内外对绵羊第6号染色体微卫星标记的研究结果进行分析,发现绵羊的多胎性状、体重性状、产毛性状密切相关,微卫星标记主要分布在第6号染色体上,而且第6号染色体上丰富的微卫星标记有利于评定绵羊的亲缘关系及遗传多样性,对于指导绵羊品种选育及遗传多样性评价具有重要的指导意义。     

鸡4号染色体微卫星标记的研究进展

鸡4号染色体上主要存在着影响体重、冠型、蛋清重、蛋重和一些屠体分割性状的QTL.本文重点介绍在鸡4号染色体上进行遗传图谱的构建和重要性状的定位情况.     

鸡4号染色体微卫星标记的研究进展

鸡4号染色体上主要存在着影响体重、冠型、蛋清重、蛋重和一些屠体分割性状的QTL。本文重点介绍在鸡4号染色体上进行遗传图谱的构建和重要性状的定位情况。     

绒山羊11号染色体7个微卫星标记的连锁图谱的构建

本试验利用内蒙古白绒山羊5个家系中的632个个体,用11号染色体上的7个微卫星标记,构建绒山羊11号染色体遗传连锁图。结果表明,7个标记的等位基因数变化范围为8~14,杂合度在0.5886~0.9348之间,平均杂合度为0.8612,各标记的多态信息含量在0.7712~0.8990之间,平均多态信息含量为0.8472。构建的遗传连锁图总长度127.7 cM,其中标记ILSTS028与INRA108间距最大,为41.2 cM;ILSTS049和INRA131间距最小,为5.1 cM。     

猪8号染色体影响产仔数性状的QTL精细定位

实验旨在基于前期从二花脸猪群体鉴别到的猪8号染色体上影响产仔数性状的数量性状基因座(Quantitative trait loci,QTL),通过增加群体的数量(二花脸猪和梅山猪)以及分子标记的密度(1个SNP/14.5 kb),利用单标记关联分析和合并群体的荟萃分析精细定位猪8号染色体影响产仔数的QTL,并挖掘QTL...     

小尾寒羊产羔性状的微卫星标记研究

选用位于绵羊第6号染色体上与多胎基因(FecB)紧密连锁的微卫星OarAE101、BM1329、BM143和OarHH55以及位于第4号染色体上的OarHH35对小尾寒羊的产羔性状进行标记研究,结果发现5个微卫星基因座在小尾寒羊的PIC都达到了高度多态(PIC>0 5)水平。5个微卫星基因座标记小尾寒羊的产羔性状,以OarAE101效果最好,找到了6个显著标记;其次为BM1329,找到了4个显著标记;BM143和OarHH35分别找到了2个和3个显著标记;在OarHH55基因座上没有找到显著标记。以上所产生的15个显著标记中,与产羔数有极显著正相关(P<0 01)的标记有5个,其相关大小顺序依次为OarAE101的等位基因113bp、BM143的基因型118bp/106bp、OarHH35的等位基因139bp、OarAE101的等位基因103bp和OarAE101的基因型113bp/103bp;与产羔数呈显著正相关(P<0 05)的标记有2个,其相关大小顺序依次为OarHH35的基因型139bp/127bp、BM1329等位基因170bp;与产羔数呈极显著负相关(P<0 01)的标记有4个,其负相关强弱顺序依次为OarAE101基因型111bp/101bp、OarAE101的等位基因111bp、BM1329的等位基因168bp、OarAE101的等位基因101bp;与产羔数呈显著负相关(P<0 05)的标记有4个,其负相关强弱顺序依次为BM143等位基因116bp、BM1329的等位基因186bp、BM1329基因型186bp/168bp、Oa     

四个微卫星标记在苏钟猪中的多态性分析

微卫星标记是近年来发展起来的一种检测基因DNA多态性的新型DNA标记，因其数量多、分布广、多态性丰富及检测方便等优点而倍受推崇。本文利用四个微卫星标记分析其在苏钟猪中的遗传多样性。结果表明，四个微卫星座位在苏钟猪中均存在较高的遗传多样性，基因杂合度为0.5962-0.8823；多态信息含量为0.5146-0.8709；有效等位基因数为2．4768-8．4935。以上结果表明，本研究采用的四个微卫星标记可以作为苏钟猪的遗传多样性的标记辅助选择。     

使用促排卵素3号提高长白母猪产仔数试验

通过４８头经产长白母猪（胎次４．１９±０．７３）试验结果表明，在第一次配种同时注射ＬＲＨ—Ａ３１００微克，间隔１２小时再复配一次，胎均产仔１２．０２头，胎均产活仔１１．２９头；对照组４８头（胎次４．１０±０．６３），胎均产仔１０．０８头，胎均产活仔９．９８头。试验组胎均产活仔增加１．３１头，提高１３．１３％，差异显著（Ｐ＜０．０５）。     

四个微卫星标记在苏钟猪中的多态性分析

微卫星标记是近年来发展起来的一种检测基因DNA多态性的新型DNA标记,因其数量多、分布广、多态性丰富及检测方便等优点而倍受推崇。本文利用四个微卫星标记分析其在苏钟猪中的遗传多样性。结果表明,四个微卫星座位在苏钟猪中均存在较高的遗传多样性,基因杂合度为0.5962～0.8823;多态信息含量为0.5146～0.8709;有效等位基因数为2.4768～8.4935。以上结果表明,本研究采用的四个微卫星标记可以作为苏钟猪的遗传多样性的标记辅助选择。     

叶酸对母猪产仔数的影响

叶酸即维生素 B11,它参与多种酶的活动 ,更重要的是与氨基酸和核苷酸的合成有关。多数研究结果表明 ,猪常用饲料的叶酸供给量 ,再加上肠道微生物合成的叶酸都可以满足各种猪的需求。但对于母猪补饲叶酸的效果尚存在争议。为了探讨叶酸对母猪繁殖力的影响 ,在漳州某猪场 ,用补饲的方法在断奶母猪的日粮中添加叶酸进行以下实验。1　材料与方法1 .1　实验猪　在本场选择长大二元杂交断奶母猪3 6头 ,按胎次品种随机分成对照组与实验组 ,每组1 8头。1 .2　日粮配制　含能量 70 5 k J,粗蛋白 1 5 .2 1 %,钙 0 .6 3 %,磷 0 .5 6 %,试验组在日粮中…     

安格斯牛体尺性状微卫星DNA标记的研究

在BoVMap的Internet数据库选用4个微卫星DNA标记,初步研究了安格斯牛不同位点基因与体尺性状之间的相关关系。结果表明:这4个微卫星标记在安格斯牛中的等位基因数分别为10,8,10和8,这些等位基因分别与不同体尺性状间构成紧密相关;其多态信息含量值(PIC)分别为0.8398,0.8418,0.8649,0.7358,是高度多态座位。     

Effect of exogenous progesterone and oestrone on litter size in swine

Three hundred sows and gilts on a large commercial unit were divided into four groups according to parity and either injected with corn oil on days 16 and 17 after service, injected with 25 mg progesterone and 12.5 micrograms oestrone on days 16 and 17 after service, or injected with these two hormones on either day 16 or day 17 after service. Animals injected with progesterone and oestrone on both the 16th and 17th days after mating had significantly (P less than 0.05) bigger litters at farrowing. Animals injected on the 17th day or on both the 16th and 17th days after mating had significantly shorter gestation periods (P less than 0.05). The treatments had no effect on the weaning to service interval or on the size of the subsequent litter.     

种猪不同交配组合的产仔数分析

用杭州市种猪试验场2003—2008年的大白猪、长白猪两个品种的母猪分娩记录,以公猪为单位,取与配母猪分娩记录有20窝以上的公猪245头,进行不同交配组合的产仔数分析。在单位公猪内,仅生一窝的与配母猪合并为一组作为对照组;两窝或以上者,一头母猪作为一组,进行对比分析。用方差分析法选出产仔数有显著差异的交配组合。结果表明,有20％左右的公猪出现这种产仔数差异显著的特殊交配组合,最多的平均窝产总仔数14-33头,最少的平均窝产活仔数只有5．67头,这种现象在生产中有实际应用的价值。     

Responses in ovulation rate, embryonal survival, and litter traits in swine to 14 generations of selection to increase litter size

Eleven generations of selection for increased index of ovulation rate and embryonal survival rate, followed by three generations of selection for litter size, were practiced. Laparotomy was used to count corpora lutea and fetuses at 50 d of gestation. High-indexing gilts, approximately 30%, were farrowed. Sons of dams in the upper 10% of the distribution were selected. Selection from Generations 12 to 14 was for increased number of fully formed pigs; replacements were from the largest 25% of the litters. A randomly selected control line was maintained. Responses at Generation 11 were approximately 7.4 ova and 3.8 fetuses at 50 d of gestation (P < .01) and 2.3 fully formed pigs (P < .01) and 1.1 live pigs at birth (P < .05). Responses at Generation 14 were three fully formed pigs (P < .01) and 1.4 live pigs (P < .05) per litter. Number of pigs weaned declined (P < .05) in the index line. Total litter weight weaned did not change significantly. Ovulation rate and number of fetuses had positive genetic correlations with number of stillborn pigs per litter. Significantly greater rate of inbreeding and increased litter size at 50 d of gestation in the select line may have contributed to greater fetal losses in late gestation, greater number of stillborn pigs, and lighter pigs at birth, leading to lower preweaning viability. Heritabilities of traits were between 8 and 25%. Genetic improvement programs should emphasize live-born pigs and perhaps weight of live-born pigs because of undesirable genetic relationships of ovulation rate and number of fetuses with numbers of stillborn and mummified pigs and because birth weight decreased as litter size increased.     

Estimation of variances for gametic effects on litter size in Yorkshire and Landrace swine

The objective of this study was to test for effects of gametic imprinting on litter size in swine by estimating variances for parent-specific gametic effects. Data were 64,047 and 137,009 multiparous records of number born alive for the U.S. Landrace and Yorkshire breeds, respectively. The statistical model included fixed effects of parity number and herd, and random effects of herd-year-season, mate, permanent environment, animal (additive genetic), and either maternal or paternal gametes. A Bayesian approach that used Gibbs sampling to obtain posterior distributions was employed. To aid in the interpretation of results, the Landrace data structure was used to simulate data with and without effects of imprinting. Analyses of the simulated records indicated that the model applied was capable of detecting effects of imprinting when such effects were present. Small, but non-zero, estimates of gametic variances were obtained when no imprinting was simulated. Estimates of the proportion of total variance accounted for by paternally transmitted gametes were 0.8 and 0.9% for Landrace and Yorkshires, respectively. These estimates were different from zero, but were similar to the results observed for data simulated without an imprinting effect. Corresponding results for maternally transmitted gametes were 1.6% for Landrace and 0.8% for Yorkshires. The estimate for Landrace was significantly greater than that observed for Yorkshires and for the simulations without a true effect and suggested the presence of a non-Mendelian genetic influence on litter size. Paternally imprinted genes are a plausible reason for the observed results. Assuming that the effect observed was due to paternal imprinting at a single biallelic locus, the substitution effect of the superior allele could be greater than 0.7 piglets per litter. Identification of a genetic marker for such an allele would be useful in marker-assisted selection of females. Other possible explanations exist for the increased gametic variance in the Landrace breed, but these explanations (such as maternal or cytoplasmic effects) may be less likely than paternal imprinting.     

Results from nine generations of selection for increased litter size in swine

Direct selection for increased litter size was done for nine generations. The select line consisted of approximately 15 sires and 60 dams per generation, and selection was based on estimated breeding values for number of live pigs. A control line of approximately 10 sires and 30 dams was maintained with stabilizing selection. Heritabilities estimated in the select line using restricted maximal likelihood procedures, daughter-dam regression within sires, and half-sib analysis were 0.01, 0.04, and 0.00 for number of pigs born alive (NBA) and 0.02, 0.16, and 0.00 for total born per litter (TB). Corresponding estimates for the control line were 0.01, 0.06, and 0.23 and 0.02, 0.07, and 0.09 for NBA and TB, respectively. Realized heritabilities for NBA from multiple regression were 0.09 +/- 0.08 in the select line and 0.11 +/- 0.166 in the control line. Heritability estimated from regression of differences in response between lines on differences in cumulative selection differentials was 0.13 +/- 0.07. At Generation 9, litter sizes, estimated breeding values, and cumulative selection differentials were 0.86 (P < 0.05), 0.63 (P < 0.01), and 9.05 (P < 0.01) pigs larger for the select line than for the control line. Phenotypic differences between lines for TB, adjusted backfat (BF), and days to 104 kg (DAYS) were not significant. Genetic trends in the select line were 0.053 +/- 0.002 pigs/yr for NBA, 0.054 +/- 0.013 mm/yr for BF, and 0.398 +/- 0.110 d/yr for DAYS. Corresponding phenotypic trends were 0.145 +/- 0.051 pigs/yr, -0.012 +/- 0.089 mm per yr, and 0.307 +/- 0.278 d/yr, respectively. Genetic trends in the control line were -0.026 +/- 0.004 pigs/yr for NBA, 0.026 +/- 0.022 mm/yr for BF, and -0.532 +/- 0.182 d/yr for DAYS. Corresponding phenotypic trends were 0.001 +/- 0.085 pigs/yr, -0.043 +/- 0.147 mm/yr, and -0.519 +/- 0.462 d/yr, respectively. Litter size can be increased by direct selection using breeding values estimated from an animal model, in conjunction with rearing selected gilts in litters of 10 pigs or less.     

A Delphi exercise used to identify potential causes of variation in litter size of Ontario swine

Forty-eight people, considered to the swine experts, were asked to collaborate in a Delphi exercise to identify the factors which they believed affect litter size in Ontario swine. The panel included 16 animal scientists, 16 pork producers, and 16 veterinarians in swine practice. The ten factors with the highest ratings were parity of the sow, mycotoxins in the feed, infections with porcine parvovirus or Leptospira spp., breeding gilts on their second versus first observed estrus, the timing of breeding with respect to the onset of estrus, purebred versus crossbred sows, boar overuse (bred by a boar that was mated more than six times per week), pen versus hand mating, age of gilt when first bred, and body condition of the sow at the time of conception. The experts did not agree about the effect on litter size of the sow's previous lactation, factors ensuring adequate nutrient intake during lactation, health of the sow and the boar, breed of a purebred sow, or the ease of mating the sow.

Key items in the use of the Delphi technique to arrive at a consensus are discussed.

     

Analysis of litter size and days to lambing in the Ripollesa ewe. II. Estimation of variance components and response to phenotypic selection on litter size

A performance data set from 376 Ripollesa purebred ewes of the experimental flock of the Universitat Autònoma of Barcelona was analyzed using a bivariate Bayesian threshold-linear model. The data set contained 1,598 litter size records and 1,699 days-to-lambing records. The model included the additive genetic effect of each animal and 3 nongenetic sources of variation: ewe age, year of lambing, and the permanent environmental effect characterized by the ewe. The flock was phenotypically selected for litter size since 1986, and replacement ewes and rams were selected from the progeny of the more prolific ewes, which had at least 3 deliveries recorded. The phenotypic trend for litter size was positive, whereas days to lambing followed an unclear pattern. Both traits had low heritabilities; 0.13 for litter size and 0.11 for days to lambing. Response to selection was evaluated through (a) the average breeding value of the ewe lambs chosen annually, and (b) the average breeding value of the overall flock. The first measurement suggested a positive trend for litter size, although it showed important oscillations. On the other hand, the average breeding value for the overall flock showed a stable positive tendency after yr 4 of selection, with estimates clearly different from zero after yr 11 of selection. A significant increase in the incidence of multiple births was observed, with a mode of approximately 10%. The correlated response in days to lambing did not show a significant trend. The effect of year of lambing also positively influenced both litter size and days to lambing, although important oscillations were observed between years. Results indicated that litter size in sheep can be effectively improved through phenotypic selection, even in small flocks; moreover, days to lambing could also be genetically improved, given the estimate obtained for its heritability.