猪生产性能性状的遗传（续二）

断奶后期生产性能的选择:对繁殖性能的影响在用于商业繁育体系的父系和母系选择目标中,为了确定瘦肉增重和效率的最适宜选择重点,必须了解瘦肉组织生长率和瘦肉组织饲料转化率性状组分(如:平均日增重,躯体结构和饲料转化率)与繁殖性能性状之间的遗传相关。可以根据有关性状间的遗传相关参数和它们的遗传力得到商品猪生产性能选择中繁殖性能选择反应的预期值。然而,如前所述,当遗传相关是从试验猪群亲属间或者从商品猪群较小样本的协方差得到时,则这一估测的精确性水很少是能为人接受的。在对断奶后生产性能的选择试验中,繁殖性能性状的相关…     

SLA与繁殖性能的研究新进展

猪的繁殖性能包括若干方面,有限的QTL分析表明在染色体4、6、7、13和15上有与繁殖性能有关的QTL,这将为开发新的选择计划作好基础,将猪7号染色体已知的SLA(猪的主要组织相容性复合体)信息应用于育种选择以改善重要的繁殖性状,将具有非常重要的意义。1对排卵数的影响 Conley(1988)、Rothschild(1984、1990)对NIH微型猪的研究表明:SLA单倍型与排卵数存在着     

微卫星标记在猪主要经济性状选育中的应用

随着遗传学理论的发展,猪的选种由表型选择发展到育种值选择,再到基因型选择（即标记辅助选择）。微卫星标记用来研究种内及品种间遗传变异是一种较好的遗传标记。由于其具有较高的突变率。较高的多态性和杂合度及检测快速方便等优点而备受青睐。近年来,随着国内外学者对其结构、遗传特性、发生机理等研究的不断深入。它在构建连锁图谱、评估遗传多样性、绘制系统发生树、疾病诊断及血缘关系鉴定等方面愈来愈显示出重大的优势。     

标记辅助选择改良猪经济性状的研究进展

标记辅助选择是近些年随着分子标记技术的发展而出现的一种新型选种方法，被认为是提高育种选择效率的一种有效方法。此文系统地综述了近年来猪重要经济性状的主效基因或数量性状座位(QTL)定位及猪标记辅助选择的应用概况、实施方法和策略等方面的研究进展，并在此基础上就当前应用分子标记辅助选择进行猪经济性状遗传改良的相关问题进行了讨论。     

猪生产性能性状的遗传

导　言在猪肉生产体系中与市场密切相关的生产性能是由产出可售产品的效率来界定的。这一效率主要决定于所耗饲料和所耗时间的成本，也决定于优质瘦肉组织的生产量。商品猪生产性能遗传性状的改善通过进行生产性能测定和选择而首先在在种猪群中得以实现。为了能成功地生产...     

猪肉品质与其它经济性状的遗传关系

猪的经济性状一般分为繁殖、生长、胴体和肉质等四类性状。以前的育种计划,繁殖、生长和胴体性状是人们的改良重点,但随着猪生长和胴体性能的不断提高,肉质有变劣的趋势,尤其在瘦肉率(量)特别高的品种上,这种现象更为突出(季海峰,2000)。综观世界养猪业的发展趋势,人们对肉质提     

猪繁殖性状的遗传改良策略

猪繁殖性能的提高将为养殖业带来巨大的经济效益，目前多数育种者将提高猪的繁殖力作为主要有种目标，并用数学遗传学方法和分子育种技术对繁殖性状进行改良。     

超细型细毛羊生化遗传标记与经济性状相关性研究

采用双垂直板高pH不连续性聚丙烯酰胺凝胶电泳系统,对中国美利奴高山型超细型细毛羊群体的4个血液蛋白位点多态性进行检测发现:血红蛋白(Hb)、转铁蛋白(Tf)、血清酯酶(Es)存在多态性,血浆白蛋白(Alb)呈单态性。对存在多态性的位点与细毛羊经济性状的相关分析表明:中国美利奴高山型超细型细毛羊群体血红蛋白、血浆酯酶位点的不同表现型与体侧毛长、羊毛伸度、羊毛细度及剪毛量等存在显著相关。部分位点可为中国美利奴高山型超细品系培育的早期选种提供辅助依据。     

中俄猪16个遗传标记基因位点的多态与繁殖性状的相关研究

检测了俄罗斯大白猪及萍乡华中二头乌猪１６个遗传标记基因位点的多态性,分析了二个猪种群体间在上述１６个基因位点上的遗传变异,探讨了所测遗传标记基因位点与种猪繁殖性状的相关性。同时,对两个猪种母猪体内抗红细胞抗原“天然抗体”的存在种类及效价与其繁殖性状的相关性进行了研究;     

Genetic correlations between reproduction and production traits in swine

Genetic correlations between reproduction and production traits were estimated in swine. Reproduction traits investigated were age at first service (AFS), number of live-born piglets in the first litter (NBA1), interval from weaning to first service after first litter (WTS1), number of live-born piglets in the second litter (NBA2), and interval from weaning to first service after the second litter (WTS2). Females generating the data were Norwegian Landrace born in nucleus herds between 1990 and 2000, and the number of records ranged from 13,792 to 56,932. Genetic correlations were estimated among the main production traits in the breeding goal: adjusted age at 100 kg live weight (A100), percentage of lean meat content (LMC), individual feed consumption from 25 to 100 kg (FC), and bacon side quality (BSQ). Average adjusted backfat thickness (BF) was included as a production trait. The A100 and BF traits were recorded on gilts on-farm with 190,454 records, whereas LMC, BSQ, and FC were recorded on-station with the number of records ranging from 12,487 to 12,992. Analyses were carried out with a multivariate animal model using average information restricted maximum likelihood procedures by first running each reproduction trait with A100 and BF, followed by each reproduction trait with LMC, BSQ, and FC. Average heritabilities for reproduction traits were as follows: AFS (0.38), NBA1 (0.11), WTS1 (0.06), NBA2 (0.12), and WTS2 (0.03); and for production traits: A100 (0.30), BF (0.44), FC (0.22), LMC (0.58), and BSQ (0.23). The highest genetic correlation was estimated between A100 and AFS (r(g)= 0.68), also resulting in a positive genetic correlation between FC and AFS. Growth (A100) was negatively (i.e., unfavorably) genetically correlated to NBA1 and NBA2 (r(g) = 0.60 and rg = 0.42 respectively), and so the genetic correlation to FC also became unfavorable (r(g)= 0.23 and r(g) = 0.20). Single-trait selection for enhanced LMC would also affect NBA1 and NBA2 unfavorably (r(g)= -0.12 and r(g)= -0.24). Correlations between BF at 100 kg live weight and reproduction traits were close to zero; however, a low genetic correlation between BF and WTS1 was obtained (r(g)= -0.12), indicating that selection toward reduced BF at 100 kg live weight may have an unfavorable impact on WTS1.     

Relationship between profitability and type traits and derivation of economic values for reproduction and survival traits in Chianina beef cows

The objectives of this study were 1) to propose a profit function for Italian Chianina beef cattle; 2) to derive economic values for some biological variables in beef cows, specifically, production expressed as the number of calves born alive per year (NACY), age at the insemination that resulted in the birth of the first calf (FI), and length of productive life (LPL); and 3) to investigate the relationship between the phenotypic profit function and type traits as early predictors of profitability in the Chianina beef cattle population. The average profit was 196 Euros/(cow.yr) for the length of productive life (LPL) and was obtained as the difference between the average income of 1,375 Euros/(cow.yr) for LPL and costs of 1,178 Euros/(cow.yr) of LPL. The mean LPL was equal to 5.97 yr, so the average total phenotypic profit per cow on a lifetime basis was 1,175 Euros. A normative approach was used to derive the economic weights for the biological variables. The most important trait was the number of calves born alive (+4.03.cow(-1).yr(-1) and +24.06 Euros/cow). An increase of 1 d in LPL was associated with an increase of +0.19 Euros/(cow.yr) and +1.65 Euros/cow on a lifetime basis. Increasing FI by 1 d decreased profit by 0.42 Euros/(cow.yr) and 2.51 Euros/cow. Phenotypic profit per cow had a heritability of 0.29. Heritabilities for eight muscularity traits ranged from 0.16 to 0.23, and for the seven body size traits between 0.21 and 0.30. The conformation trait final score can be used as an early predictor of profitability. The sale price of the animal and differences in the revenue and costs of offspring due to muscularity should be included in a future profit function.     

Relationship between genes at the pea and single comb locus and economic traits in broiler chicken

Six hatches of pedigreed broilers, comprising a total of 7593 birds from 223 Cornish‐type sires, 112 homozygous and 111 heterozygous for pea comb, were used to study the effect of comb type on final weight, frequency of breast blisters and carcass yield.

Contrary to results reported in the literature there was no evidence of an association between comb type and broiler growth.

Single comb broilers showed a lower incidence of breast blisters than their siblings with pea combs. This difference was highly significant in males and less so in female broilers. It is suggested that this might be another manifestation of the pea comb allele, possibly as a result of structural changes in the skin. For a given weight, females had a significantly lower frequency of breast blisters than males, indicating a direct influence of sex on breast blister formation apart from the immediate effect of body weight.

Broilers with pea comb had a slightly better carcass yield than single comb broilers.     

Relationship between blood iron parameters and trichinellosis in swine

Reduced levels of total iron binding capacity and unsaturated iron binding capacity were observed in the blood of trichinous and iron-injected trichinous pigs. No change was observed in their serum iron and saturation concentration levels. Also, reduced iron concentration levels were observed in the livers of trichinous pigs, while increased iron concentration levels were observed in the spleens of trichinous pigs and the livers and spleens of iron-injected pigs. No difference was found with regard to weight gains, number of larvae per gram of tissues, or histologic characteristics of 'nurse cells'.     

群体分布与大豆农艺性状关系的研究

研究了大豆(Clycine max)群体分布与其生长农艺性状的关系,为构建合理的群体分布提供理论依据。2009年以合丰45、红丰11为材料,设计6个不同的群体分布进行田间试验,采用LSD法比较分析群体分布对农艺性状的影响,计算了单位面积茎数的补偿效应,分析了产量变化趋势及其与农艺性状和群体分布的关系,并对农艺性状进行主成分分析。结果表明:1)群体分布显著影响农艺性状,株距较行距对农艺性状的影响更显著,无品种株型差异。2)株距减小产生的单位面积茎数补偿效应值随行距增大呈二次抛物线变化趋势;行距增大产生的2组单位面积茎数补偿效应值随株距增大变化趋势不一致,且单位面积茎数补偿效应值存在株型差异。3)群体分布显著影响产量,获得产量极值的群体分布存在品种差异;产量与茎粗、行距显著正相关。4)本研究分析得到2个主成分生长性状因子、产量性状因子,其中,生长性状因子具有较强的品种特异性,群体分布对2因子的影响不同。     

Relationship between oocyte maturation and fertilization on zygotic diversity in swine

Two experiments were conducted to examine how oocyte maturation and fertilization influence zygotic diversity in swine. In the first experiment, the distribution of oocyte maturation was compared to that of zygotic development. Oocytes were aspirated from follicles of 31 gilts and classified into stages of meiosis. Zygotes were flushed from oviducts of 19 additional gilts and classified into stages of meiosis and fertilization. The second experiment examined whether the time from ovulation to fertilization was constant among all oocytes. To test this premise, four to six oocytes from follicles of 10 mated gilts were aspirated just before or during ovulation, stained and transferred back into the oviducts of these same gilts. Zygotes were recovered 10 h later to determine whether the first oocytes ovulated were the more developed zygotes and, conversely, whether the last oocytes to be ovulated represented the lesser developed contemporaries. The skewed (P less than .05) distribution of oocyte maturation was similar to that of zygotic development. Regression of the frequency distribution describing early oocyte maturation resulted in a line with a slope (.59) that was similar to the slope (.58) of the regressed distribution of zygotic development. Likewise, the order of ovulation and order of subsequent stages of zygotic development were similar. These data suggest that variation in zygotic development in swine was due to variability in oogenesis; the time from ovulation to fertilization appeared to be constant.     

Examination of the relationship between the estrogen receptor gene and reproductive traits in swine

The relationship between estrogen receptor (ESR) genotype and reproductive traits in a population of Yorkshire, Large White, and crossbred animals was studied. Reproductive tract and litter data were analyzed for associations with ESR genotype, parity, and breed. Forty-six Yorkshire, 31 Large White, and 70 crossbred females from the above population were mated to Hampshire boars and slaughtered at 75 d of gestation. Data collected included ovulation rate, uterine horn length, number of fetuses, fetal weight, uterine weight, number of mummies, fetal sex, fetal placement, fetal survival, and fetal space. Data were analyzed using a model that included the fixed effects of ESR genotype, breed, parity, and all significant two-way interactions. Litter data representing 212 litter records were analyzed in a model that included the fixed effects of ESR genotype of dam, parity, farrowing month, dam breed, sire breed, and all significant two-way interactions. The ESR genotype was significantly associated with the total litter weight of piglets born and total litter weight of piglets born alive. Dams with the AA genotype had significantly (P = 0.04) heavier litters at birth (14.44 +/- 0.36 kg) than dams with the BB genotype (13.43 +/- 0.47 kg). Ovulation rate was significantly (P < 0.05) different between animals of parity 1 (17.22 +/- 0.41) and parity > or = 3 (19.92 +/- 0.85). Significant breed effects were observed for fetal weight, with purebred Large White animals having a greater fetal weight per horn (3,909 +/- 114 g) than purebred Yorkshire animals (3,553 +/- 92 g). Notable, but nonsignificant, trends with respect to ESR genotype were also observed for number of piglets alive at weaning and total litter weight at weaning. The ESR gene is positively associated with several previously uninvestigated reproductive traits.     

Genetic parameters for testes traits in swine

Data were collected from 1,245 Duroc boars and 527 Yorkshire boars. This represents 128 Duroc and 57 Yorkshire sires. Body weights, testis length and combined testes width at 140 and 168 d were obtained. Of these boars, 432 were castrated at a later age to evaluate relationships between in situ measures and excised testis traits. Heritabilities for testis length, width and volume at 140 d ranged from .16 to .25 in both Duroc and Yorkshire data. Heritabilities for testis measurements at 168 d ranged from .16 to .36 in both data sets. Favorable negative genetic relationships were found between in situ testis measures and age to 104 kg and backfat adjusted to 104 kg. Correlations among in situ measurements were high and positive. All excised testicular traits were highly heritable except for right epididymis weight and excised testis width. Correlation estimates among excised testis traits were generally positive. Phenotypic and genetic correlation estimates between live (in situ testis and growth performance traits) measurements and excised testis traits were generally favorable. This study suggests that in situ testis measurements should be good predictors of sperm production. It also suggests that selection for testis size should not be antagonistic to selection for growth performance traits.     

Relationship between Mycoplasma hyosynoviae infection and front limb weakness in Duroc swine

A relationship between degree of Mycoplasma hyosynoviae infection and front limb soundness was examined in 254 Duroc swine. These pigs represented 3 lines of pigs (structurally sound, control, and unsound) from a population divergently selected for 4 generations for front limb soundness. Analysis of sera collected every 4 weeks between 6 and 26 weeks of age yielded complement-fixing antibody titers that were believed to be indicative of the degree of natural infection with M hyosynoviae. Analysis of several variables defined by using titer values failed to reveal significant differences among the 3 selected lines, but trends indicated higher mean and peak titer values for pigs from the unsound line. Correlations between titer variables and front limb soundness variables within genetic groups were low and not significantly different from zero. Correlations between all titer variables were calculated; the correlation between mean titer and peak titer was 0.81 (P less than 0.01), and between mean titer and age at detection of first titer, was -0.56 (P less than 0.01). Pooled heritability estimates were 0.51 +/- 0.28 for mean titer and 0.28 +/- 0.25 for peak titer.     

Relationship between sperm quality traits and field-fertility of porcine semen

An investigation involving seven boars, active in artificial insemination, and 1,350 multiparous sows was conducted at a private farm and aimed at examining the relationship between sperm quality traits and boar fertility in terms of farrowing rate and litter size. This experiment was done for 6 months. The semen samples were evaluated for subjective sperm motility and concentration. Ejaculates with at least 1 × 10⁸ sperm/mL and 70% sperm progressive motility were extended with a commercial medium to 30 × 10⁶ sperm/mL and used for artificial insemination (AI). AI dose was 100 mL semen containing 3 × 10⁹ spermatozoa. Aliquots of diluted semen were assessed for live morphologically normal spermatozoa (LMNS, eosin-nigrosin stain exclusion assay) and sperm chromatin instability (SCI, acridine orange assay). Farrowing rates according to different boar sperm varied (p < 0.001) from 59.3 to 88.92%. The mean values of LMNS (47.2~76.5%) and SCI (0.16~4.67%) differed significantly among boars. LMNS (r = 0.79, p < 0.05) and SCI (r = -0.90, p < 0.02) accounted for 62.2 and 81.7% of the variability in farrowing rates, respectively. After the combination of sperm traits, the relationship between percentage of LMNS with stable chromatin structure and farrowing rate was significant (r = 0.86, p < 0.05). The number of live piglets per parturition was not significantly correlated with sperm quality attributes. In conclusion, boar fertility after AI with freshly diluted semen can be predicted based on the evaluation of sperm morphology and chromatin integrity.