藏猪新品系的选育初报

在藏猪中心产区建立藏猪选育基础群,对其外貌特征、繁殖性能和生长发育进行个体测定。采用综合育种值对基础群藏猪按照高繁殖力和快生长高瘦肉率2个方向进行选种。经过3个世代的选育,2个品系藏猪外貌体型更典型;高繁殖力品系总产仔数、产活仔数、初生窝重、断奶仔数和断奶窝重分别达到了7.65头、7.16头、5.42 kg、6.46头和31.05 kg;快生长高瘦肉率品系初生重、断奶重、25 kg日龄、屠宰率、腿臀率、瘦肉率和眼肌面积分别达到了0.78kg、7.87 kg、260.5 d、61.65%、31.44%、63.49%和9.13 cm2,背膘厚减小至8.19 mm,肉质性状变化不大,保持了藏猪良好的特性。     

藏猪繁殖性状遗传参数分析

藏猪是中国特有的高原型地方猪种,本研究采用非求导约束最大似然（MTDFREML）方法对藏猪繁殖性状进行遗传分析。结果估算出藏猪乳头数、总产仔数、产活仔数、初生窝重、断奶仔数、断奶窝重的遗传力分别为0.36、0.12、0.10、0.13、0.09和0.12,乳头数与断奶窝重、初生窝重和断奶仔数存在明显的遗传力相关。     

山西白猪高产仔母系繁殖性能测定

以马身猪、太湖猪（二花脸类群）和长白猪为育种素材,采用标记辅助选择技术结合群体继代选育法,经7年6个世代育成山西白猪高产仔母系。对7个世代母猪繁殖性能分析结果表明,4世代母猪的繁殖性能最好,母猪初产窝产仔10.64头,产活仔数9.85头,断奶头数9.36头,哺育率达95.03%,初生个体均重1.42 kg,28日龄断奶窝重62.36 kg。除产活仔数外,均极显著高于0世代（P<0.01）。初生和断奶时仔猪均匀度随选育逐代提高,一致性增强。该品系已具有良好的繁殖性能,是一个优良的母本品系。     

巴克夏母猪繁殖性能测定及相关分析

该研究通过测定39头巴克夏母猪的8个主要繁殖性状(产仔数、产活仔数、初生重、初生窝重、21日龄窝重、断奶仔猪头数、断奶个体重、断奶窝重),用SAS软件进行了相关及通径分析。研究结果表明巴克夏母猪的平均产仔数为7.97头,仔猪初生重为1.29 kg。经通径分析可知,在所分析的8个性状中,初生个体重的通径系数最高。因此,要提高巴克夏母猪繁殖性能,除了通过选育提高母猪的繁殖力外,还要采取措施改善巴克夏猪的饲养管理条件,以提高仔猪初生个体重。     

PIC母猪窝产活仔数与初生重、断奶重、断奶成活率的相关性研究

以262窝PIC母猪所产的2 396头仔猪为研究对象,探讨窝产活仔数对仔猪初生重、28日龄断奶重及断奶成活率的影响。结果表明,随着窝产活仔数的增加,仔猪初生窝重、28日龄断奶窝重增加,断奶成活率降低。不同窝产活仔数间的初生窝重差异极显著(P0.01),窝产活仔数9~11头间的断奶窝重差异不显著,但极显著大于窝产活仔数6、7头(P0.01),断奶成活率以窝产活仔数6~11头较好(90%以上);不同窝产活仔数间的初生个体重差异不显著(P0.05),窝产活仔数6~10头间的断奶个体重差异不显著(P0.05),极显著大于窝产活仔数11头和12头(P0.01)。窝产活仔数与初生窝重、28日龄断奶窝重呈极显著正相关,相关系数分别为0.917和0.589;与初生个体重呈负相关,相关系数为-0.105;与28日龄断奶个体重及28日龄断奶成活率呈极显著负相关,相关系数分别为-0.417和-0.581。本试验条件下,窝产活仔数在10~11头之间可以取得较好的经济效益。     

榆林猪繁殖性状研究

本文通过研究母猪乳头数、总产仔数、产活仔数、初生个体重、初生窝重、母猪泌乳力、断奶活仔数、断奶个体重和断奶窝重等繁殖性状的特点,发现榆林猪的繁殖性状主要表现在母猪有效乳头较多,7～8对乳头的母猪占61％以上。初生个体整齐度高,总产仔数、产活仔数、初生窝重、母猪泌乳力、断奶窝重等主要繁殖力性状个体间变异较大．有充分选择改良提升的空间。繁殖力性状的遗传力值较低,在0．11-0．20之间。     

母猪个体综合繁殖力相关指标的固定效应分析

对16 367头大白、长白、杜洛克母猪,共33 084个胎次的繁殖记录进行调查分析,建立固定效应模型对胎均窝产总仔数LS1、胎均窝产活仔数LSBA1、胎均出生窝重LW1、胎均窝断奶活仔数WLS1、胎均窝断奶窝重WLW1、周期均窝产总仔数LS2、周期均窝产活仔数LSBA2、周期均出生窝重LW2、周期均断奶活仔数WLS2、周期均断奶窝重WLW2进行最小二乘分析,着重讨论场效应、品种效应、品种内品系效应对母猪繁殖能力的影响,分析母猪个体综合繁殖力相关指标的优势。结果表明,场效应、品种效应、品种内品系效应对母猪个体综合繁殖力所有性状的影响均达到极显著水平(P0.01)。     

淮南猪新品系繁殖性能的选育及分析

经过多次杂交筛选 ,在淮南猪中引入一定比例的杜洛克猪外血组建基础群 ,开展群体继代选育工作。对五个世代母猪繁殖性能的分析表明 ,培育的新品系基本保持了淮南猪繁殖力高的特性 ,母猪初生窝重增大 ,仔猪哺乳期生长速度加快 ,主选性状进展显著。与零世代相比 ,五世代总产仔数增加 2 .92头 (P <0 .0 1) ,产活仔数增加 2 .83头 (P <0 .0 1) ,初生窝重增加 5 .72kg(P <0 .0 1) ,2 0日龄头数增加 2 .31头 (P <0 .0 5 ) ,2 0日龄窝重增加 19.73kg(P <0 .0 1) ,断奶头数增加 1.2 6头 (P >0 .0 5 ) ,断奶窝重增加 18.2 7kg(P <0 .0 5 )     

瘦肉型猪母本品系选育

本研究用长白猪与枫泾猪杂交,产生长×（长×枫）杂交猪,组建品系选育基础群。横交固定,形成育种核心群。经过４个世代的选育,品系主要性能指标：产仔数１３．７１头,产活仔数１２．８７头,平均日增重６１５克,料重比３．１８,体重达９０千克日龄１７８．９天,背膘厚１７．０９毫米,胴体瘦肉率５９．６５％,肉质优良,无ＰＳＥ和ＤＦＤ肉。经配合力测定,筛选出大×中组合,窝产瘦肉量４７６千克。研究结果表明,选育中的母系具有产仔多、生长快、瘦肉率高、肉质好等优良特性     

丹系长白猪在华南地区生长性能与繁殖性能的初步观察

研究对2013年8月从惠州市广丰农牧有限公司引进的60头丹系长白母猪进行扩群选育,并持续开展生长性能与繁殖性能测定。生长性能测定结果表明,丹系长白公猪达100 kg体重日龄为168.37 d,达100 kg体重背膘为11.20 mm,30~100 kg料重比为2.51;母猪达100 kg体重日龄为171.71 d,达100 kg体重背膘为12.23 mm,30~100 kg料重比为2.60。繁殖性能测定结果表明,丹系长白母猪受胎率为94.02%,配种分娩率为88.79%,窝产仔数14.27头,窝产活仔数12.23头,初生窝重17.71 kg,断奶窝重70.09 kg。屠宰和肉质测定结果表明,丹系长白猪屠宰率为72.57%,瘦肉率为61.44%,肉色3.75,大理石纹2.25,失水率为6.21%。试验结果可为丹系长白猪在华南地区的选育和饲养管理提供必要的基础技术参数。     

湖北白猪优质系选育进展报告

为充分利用地方猪种资源,培育优质、高效的专门化母本新品系,以长白猪、梅山猪、通城猪和湖北白猪为遗传资源,进行了湖北白猪新品系的选育。经过6个世代持续选育,各品种在品系的血统比例分别为45.15%、23.39%、7.08%和24.38%。湖北白猪优质系初产母猪产仔数达12.13头/窝,经产母猪达13.52头/窝,经产母猪产活仔数12.74头/窝;肥育期平均日增重达到621.39 g,达90 kg体重日龄为179.26 d,料重比3.15。90 kg体重阶段屠宰率为74.96%,屠体背膘厚为2.64cm,瘦肉率为58.69%,眼肌面积为38.02 cm2,肌内脂肪含量3.05%。     

中国瘦肉型猪育种目标性状经济权重的测算

为了加快我国瘦肉型猪育种的研究进展,制定出符合我国瘦肉型猪育种现状的经济权重。本研究依据中国杜长大三元杂交猪育种现状,选择了适合中国当前杜长大三元杂交体系的目标性状;以生物经济模型为基础模拟猪的生产流程,计算生产周期各阶段成本和收入;先采用差额法计算目标性状的边际效益,再通过各性状的遗传标准差校正得到各育种目标性状的经济权重。结果表明,目前中国瘦肉型猪育种的繁殖、生长和胴体品质性状主要包括窝产活仔数、母猪断配间隔、饲料转化率、达100 kg体重日龄、达100 kg体重背膘厚。在我国现有生产水平和市场条件下,上述各性状的边际效益分别为：19.52、-1.07、-286.95、-8.41、-13.20元。通过计算不同品种的经济权重,得到杜洛克的饲料转化率、达100 kg体重日龄、达100 kg体重背膘厚相对经济权重分别为：50.42%、34.50%、15.08%;长白和大白群体窝产活仔数、母猪断配间隔、饲料转化率、达100 kg体重日龄、达100 kg体重背膘厚的相对经济权重分别为：16.82%、0.22%、39.56%、31.42%、11.98%和32.77%、0.41%、33.22%、24.43%、9.17%。结果显示,目前,在中国瘦肉型猪育种过程中,饲料利用效率应作为育种的主要目标性状,对于不同品种应选择最适合的性状进行育种。     

山西白猪高产仔母系育肥性能与胴体品质测定

以马身猪、太湖猪(二花脸类群)和长白猪为育种素材,采用标记辅助选择技术结合群体继代选育法,经7年6个世代育成山西白猪高产仔母系。结果发现,该品系6世代个体186.48日龄体重达100 kg,30~100 kg阶段日增重708.35 g,每千克增重耗料3.14 kg;体重100 kg屠宰,屠宰率为77.00%,胴体瘦肉率为57.93%,眼肌面积为32.20 cm²。山西白猪高产仔母系生长发育快,胴体品质好,是一个优良的专门化品系。     

Reallocation of body resources in lactating mice highly selected for litter size

The present study investigated differences in the allocation patterns of body stores in lactating female mice from a line selected for high litter size at birth (S-line, average litter size of 20) and dams from a nonselected control line (C-line, average litter size of 10). Body weight, litter size, litter weight, and absolute and relative lipid and protein mass were measured at peak lactation (2 wk in lactation) and at weaning (3 wk in lactation). Body size in S-line females has been increased as a correlated effect of selection for high litter size at birth, allowing for larger litters and higher absolute milk production. However, these dams produce larger litters relative to their own body weight. At peak lactation, lipid and protein percentage did not differ between lines. At weaning, S-line females had a higher protein percentage (P < 0.001) and lower lipid percentage (P < 0.05) than C-line females. Apparently, S-line females produce more offspring but at a greater cost to their own metabolism. This process was insufficient to supply the offspring with adequate resources, resulting in reduced (P < 0.0001) pup development and increased (P < 0.0001) preweaning mortality rates.     

Economic weights for sow productivity traits in nucleus pig populations

Economic values or weights measure the net economic gain per unit genetic increase of a given trait. These were derived for sow productivity traits for use as weighting factors in a dam line selection index used by purebred or nucleus dam line breeders. The profit function approach was used in order to provide flexibility to alternative production systems, market requirements or population trait levels. The approach accounted for constraints on perinatal survival rate imposed by larger birth litter sizes. The effect of accounting for these constraints was to reduce the economic value of birth litter size as the population average increased; without this, the economic weight for litter size was constant. Weights for the other traits were not affected. Economic weights were calculated for both the 100 kg finished pig and the 25 kg feeder pig market, and for a range of average birth litter sizes, with constant values for all other traits, using average market conditions, prices and costs in Canada as an example. The relative importance of litter size for the finished pig market decreased from 64% of the total breeding value when average litter size was 8 pigs to 29% when average litter size was 20 pigs, whereas that of perinatal survival increased from 17% to 42%, and that of survival to weaning increased from 7% to 18%. The relative importance of litter size for the feeder pig market also decreased from 45% to 15% as average litter size increased from 8 to 20 pigs, whereas that of piglet weaning weight increased from 22% to 41%, that of perinatal survival increased from 12% to 22% and that of survival to weaning increased from 5% to 9%. The relative importance of age at puberty and weaning to conception interval were both less than 8% of the total in both markets at all litter sizes. These results show that economic weights for litter size designed for populations with relatively small litter sizes should be reduced when the average litter size becomes large and more emphasis should be placed on other traits, particularly perinatal survival.     

聊城金桥蓝狐育种核心群选育研究

通过组建聊城金桥蓝狐核心群,采用等级选配、品质选配与亲缘选配等综合技术制定选育方案。经连续六个世代选育,成年种公狐体长（78.30±1.74）cm,体重（14.90±0.79）kg;成年母狐体长（65.22±1.24）cm,体重（8.49±0.32）kg。金桥蓝狐背中部被毛密度均在18000根/cm2以上,皮张尺码在000级以上占95.94%,平均产仔7.30±0.54只,断奶成活5.34±0.64只,仔狐断乳成活率70%以上。与F1相比,成年公狐体长提高11.22%（P〈0.01）,体重提高48.70%（P〈0.01）,成年母狐体长提高13.23%（P〈0.01）,体重提高22.16%（P〈0.01）,胎平均产仔降低3.95%,断奶成活降低4.47%。金桥蓝狐群体遗传性能稳定,体型外貌整齐一致,性状的变异较小。F6成年公狐体长、体重变异系数分别为2.0%和5.3%,成年母狐体长、体重变异系数分别为2.0%和3.8%。     

Responses to 19 generations of litter size selection in the Nebraska Index line. I. Reproductive responses estimated in pure line and crossbred litters

Our objective was to estimate responses in reproductive traits in the Nebraska Index line (I) after 19 generations of selection for increased litter size. Responses were estimated in dams producing pure line, F1, and three-way cross litters. A total of 850 litters were produced over six year-seasons, including 224 pure line litters, 393 F1 litters produced from I and C females mated with Danbred NA Landrace (L) or Duroc-Hampshire (T) boars, and 233 litters by F1 L x I and L x C females mated with T boars. Contrasts of means were used to estimate the genetic difference between I and C and interactions of line differences with mating type. Farrowing rates of lines I (u = 91.0%) and C (u = 92.8%) did not differ. Averaged across all genetic groups, mean number born alive per litter was 10.1 pigs, and number and weight of pigs weaned per litter, both adjusted for number nursed and weaning age of 12 d, were 9.7 pigs and 34.4 kg, respectively. Averaged across mating types, direct genetic effects of I were greater than C (P < 0.05) for total born (3.53 pigs), number born alive (2.53 pigs), number of mummified pigs (0.22 pig), and litter birth weight (2.14 kg). The direct genetic effect of line I was less than C (P < 0.05) for litter weaning weight (-1.88 kg). Interactions of line effects with crossing system were significant (P < 0.05) for total number born, number of stillborn pigs, number weaned, and litter weaning weight. In pure line litters, I exceeded C by 4.18 total pigs and 1.76 stillborn pigs per litter, whereas the estimate of I-C in F1 litters was 2.74 total pigs and 0.78 stillborn pig per litter. The contrast between I and C for number weaned and litter weaning weight in pure litters was 0.32 pig and -0.28 kg, respectively, compared with 0.25 pig and -2.14 kg in F1 litters. Crossbreeding is an effective way to use the enhanced reproductive efficiency of the Index line.     

Correlated responses of carcass and reproductive traits to selection for rate of lean growth in swine

Mass selection for an index of increased postweaning average daily gain and decreased backfat thickness was practiced for five generations. Litter size and weight for 221 gilt litters, birth weight and nipple number for 2,242 piglets and weaning weight at 42 d of age for 2,111 pigs were recorded. Carcass measurements were taken on 331 pigs. Differences between means of the lines (select control) were regressed on cumulative selection differential of the index. These regression coefficients were negative (P greater than .10) for total number born, number born alive, number weaned per litter, nipple number and carcass backfat thickness. Coefficients were positive (P greater than .10) for individual pig and litter weights at birth and weaning and for the carcass traits of length, longissimus muscle area and percentage of ham and loin. Absolute values of realized genetic correlations of index with traits evaluated were all .35 or less except the correlation with carcass backfat, which was -.84. None of these was significant; therefore, index selection for lean growth should have little effect on litter size and weight but may have a beneficial effect on carcass backfat.