中国荷斯坦牛运动评分的遗传参数估计

本研究利用2007年间武汉惠尔康扬子江乳业有限公司武湖牧场887头母牛运动评分的鉴定记录,配合单性状动物模型,利用MTDFREML软件,采用REML方法估计了相关的参数。结果表明,运动评分受泌乳期和饲养方式的影响,运动评分随泌乳期的增加有增加的趋势,栓系式饲养奶牛相对于散栏式饲养奶牛有更高的运动评分。运动评分的遗传力为0.09,为低遗传力性状。     

Polymorphisms in genes of the somatotrophic axis are independently associated with milk production, udder health, survival and animal size in Holstein-Friesian dairy cattle

The somatotrophic axis consisting of pituitary-derived growth hormone and circulating insulin-like growth factor 1 has been well established as key regulators of animal health, metabolism, lactation, fertility, body composition and growth rate. The aim of this study was to simultaneously quantify the associations between SNPs in candidate genes of the somatotrophic axis (i.e., IGF-1, GH1 and GHR) with performance traits in Holstein-Friesian (HF) dairy cattle. Both novel SNPs identified previously by this group alongside other published SNPs within these genes were analysed for associations with performance in dairy cattle. Multiple regression analyses regressing genetic merit of up to 848 HF sires on novel SNPs (n = 76) and published SNPs (n = 33) were undertaken using weighted animal mixed linear models. Twenty-three SNPs were significantly associated with at least one of 18 traits analysed and involved in milk production, udder health, fertility and growth. Eight traits including milk fat composition, carcass conformation, stature, chest width, body depth, rump width, carcass and cull cow weight were independently associated with SNPs in two genes. Furthermore, for several traits including milk fat yield, somatic cell count, survival and carcass fat, SNPs in all three genes were independently associated with performance. Milk fat yield and carcass fat showed the highest number of independent associations across all three genes with five SNPs associated with both traits. The cumulative effects of the favourable alleles of all five SNPs across GH1, GHR and IGF-1 result in an increase of 5.9 kg and 28.6 units of milk fat and carcass fat, respectively. Cow survival was associated with a single SNP in each of the three genes with a cumulative allele effect of 1.5%. Independent effects of polymorphisms in GH1, GHR and IGF-1 reinforce the central role of the somatotrophic axis on animal development and performance.     

The polymorphism in the β4-defensin gene and its association with production and somatic cell count in Holstein-Friesian cows

The aim of this study was to find a polymorphism of the bovine β4‐defensin gene and search for its association with milk yield and composition and with the somatic cell count in milk. The data were from the years 1999 to 2004 on 212 Holstein‐Friesian (HF) dairy cows, descended from 70 sires. Based on the sequence of the bovine β4‐defensin gene (GenBank no. AF008307 ) the primers were designed for the amplification of the 924‐bp or 393‐bp long fragments. The 924‐bp long fragment was sequenced and the sequence was compared with that available in the GenBank. Ten putative nucleotide sequence polymorphisms were found in the intron of the bovine β4‐defensin gene. One of them, a C→T transition at position 2239, that creates a new NlaIII (Hin1II) restriction site, was genotyped with polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) in a cohort of 212 HF cows. The CC genotype was the most common (72%). The heterozygous CT genotype was found in 26% of the genotyped cows and four cows (2%) were TT homozygotes. In order to determine the relationship between the polymorphism of the β4‐defensin gene and milk production traits a multi‐trait repeatability test‐day animal model was used. The Derivative‐free Multivariate analysis program was used for computation. The differences between estimates for genotypes were checked using Student's t‐test. The model included the animal genotype, year‐season of calving and parity as fixed effects and the animal additive genetic effect and permanent environmental effect of individual cows as well as dates of the tests as random effects. Significant associations were found between the RFLP‐NlaIII and milk fat, protein and lactose contents. Also, a significant effect was shown of the defensin genotype on the somatic cell count in the milk.     

牛肌肉生长抑制素基因单核苷酸多态性分析

应用PCR-SSCP分析方法,对94头肉牛(公牛45头:西门塔尔34头,夏洛来11头;母牛49头:西门塔尔24头,夏洛来25头)的肌肉生长抑制素(MSTN)3个外显子进行了多态性分析.结果显示,第1外显子存在2种基因型,分别为AA型和AB型.经测序发现,第1外显子4 bp处存在C→G的碱基突变,导致编码的氨基酸由谷氨酰胺(Gln)→谷氨酸(Glu).统计结果表明,等位基因B的含量低,而且只在西门塔尔品种内含0.026 6.利用SPSS软件作最小二乘分析,结果表明,B等位基因与西门塔尔牛的成年体质量和犊牛出生体质量呈显著正相关.     

生物抗氧化剂对原料奶体细胞数的影响

原料奶中体细胞是间接反应奶牛乳房是否健康的一个有力数据。同时过高的体细胞也将直接影响到原料奶的质量和价格。因此,本试验选择年龄、胎次、产奶量、泌乳天数相近的中国荷斯坦奶牛80头,探讨日粮添加34g生物抗氧化剂对原料奶中体细胞的影响。结果表明,生物抗氧化剂对奶牛产奶量及乳成分无显著影响。但与对照组相比,试验组原料奶中体细胞数呈显著低于对照组（P〈0.05）。因此,本研究表明,生物抗氧化剂能够有效降低原料奶中体细胞数,提高原料奶质量。     

BRCA1基因多态性及其与奶牛乳房炎抗性的相关性研究

为了研究BRCA1基因突变与荷斯坦奶牛体细胞数和体细胞评分的关系,试验通过对BRCA1基因外显子13、14进行克隆、序列比对和挖掘已有突变的方法确定该基因的多态位点,采用SNaPshot技术检测了BRCA1基因25025 T>A和46126 G>T突变位点在北京郊区荷斯坦奶牛群体中的分布,并对突变位点与体细胞数和体细胞评分进行了关联分析。结果表明,荷斯坦奶牛BRCA1基因2个位点均检测到3种基因型,其中25025 bp位点TT基因型为优势基因型,46126 bp位点GT基因型为优势基因型。25025 bp位点AA基因型个体体细胞数(P<0.05)和体细胞评分(P<0.01)都显著低于TT和TA基因型;46126 bp位点TT基因型个体体细胞数显著低于GG和GT基因型个体(P<0.05),但3种基因型个体体细胞评分无显著差异(P>0.05)。本研究结果初步表明,BRCA1基因25025和46126 bp位点可作为中国荷斯坦牛乳房炎抗性的标记辅助选择。     

Comparison of casein haplotypes between two geographically distant European dairy goat breeds.

The aim of this paper was to characterize the diversity among haplotypes based on 22 single nucleotide polymorphisms (SNPs) and one deletion within four casein genes in two geographically distant goat populations, the Sicilian Girgentana breed and the Norwegian goat breed. Forty Girgentana goats were genotyped for the aforementioned polymorphisms and the resulting data set was compared with 436 goats from the Norwegian population previously genotyped for these markers. Several casein gene polymorphisms were not in Hardy-Weinberg equilibrium either in Girgentana, or in the Norwegian breed. The SNP haplotype frequencies for the four casein genes were calculated and despite the large geographical distance and phenotypic divergence between these breeds, a proportion of casein loci haplotypes were found to be identical between both Norwegian and Girgentana goats. However, for the CSN2 gene there were no common haplotypes between the two populations. The level of linkage disequilibrium between the casein genes was less in the Girgentana population than in the Norwegian population.     

Genetic diversity and structure in Bos taurus and Bos indicus populations analyzed by SNP markers

The purpose of this study was to assess genetic diversity, phylogenetic relationship and population structure among nine Eurasian cattle populations using 58 single nucleotide polymorphism (SNP) markers. The calculated distribution of minor allele frequencies and heterozygosities suggested that the genetic diversity of Bos indicus populations was lower than that of Bos taurus populations. Phylogenetic analyses revealed the main divergence between the Bos taurus and Bos indicus populations, and subsequently between Asian and European populations. By principal components analysis, the Bos taurus and Bos indicus populations were clearly distinguished with PC1 (61.1%); however, six Bos taurus populations clustered loosely and the partial separation between European and Asian groups was observed by PC2 (12.5%). The structure analysis was performed using the STRUCTURE program. Distinct separation between Bos taurus and Bos indicus was shown at K = 2, and that between European and Asian populations at K = 3. At K = 4, 5 and 6, Mongolian population showed an admixture pattern with different ancestry of Asian and European cattle. At K = 7, all Bos taurus populations showed each cluster with little proportion of admixture. In conclusion, 58 SNP markers in this study could sufficiently estimate the genetic diversity, relationship and structure for nine Eurasian cattle populations, especially by analyses of principal components and STRUCTURE.     

Novel variants within the coding regions of the Slc11A1 gene identified in Bos taurus and Bos indicus breeds

Although in the cow the genetic resistance to brucellosis has been previously attributed to the Slc11A1 gene encoding Nramp1 protein, none of the mutations described to date seems to be the cause. To be able to associate another polymorphism of the gene to brucellosis resistance, we characterized the gene and identified in different breeds of Bos taurus and Bos indicus, six new variants among a total of 11 single nucleotide mutations, of which five occurred in the coding sequence (three are missense mutations), one in the promoter region and five in introns. The allelic and genotypic frequencies calculated revealed differences (p < 0.05) among the breeds studied.     

Correlation Study of CARD15 Gene StyⅠPolymorphism and Susceptibility of Tuberculosis in Dairy Cows

The aim of this study was to investigate the association between CARD15 gene StyⅠpolymorphism and susceptibility to tuberculosis (TB) of dairy cows from Yunnan plateau.A total of 201 dairy cows (103 cases and 98 controls) from Kunming,Yuxi and Dali were used in this study.We designed a specific primer pair for PCR-RFLP analysis.By using PCR-RFLP genotyping and PCR sequencing,We analysized allele frequency and correlation between polymorphism of CARD15 gene and susceptibility to bovine tuberculosis in Yunnan province.The results showed that there were three genotypes in Sty Ⅰ enzyme site,AA,AG and GG.In cases,the genotype frequencies of AA,AG and GG were 0.03,0.42 and 0.55,respectively,while in controls were 0.01,0.05 and 0.94,and the allele frequencies of A and G were 0.24 and 0.76 in cases,while were 0.04 and 0.96 in controls.Then analysizing the genetic pattern of polymorphic loci,we found that the best genetic model was dominant and the frequency of AG-AA in cases (44.7%) was apparently higher than that in controls (6.1%) (OR(95% CI)=0.08 (OR< 1)),so extremely significant difference existed between cases and controls (P< 0.0001).The polymorphism of StyⅠenzyme cut site in CARD15 gene was significantly associated with the susceptibility to tuberculosis of Yunnan plateau dairy cows,and AG-AA might be the susceptible genotype to tuberculosis.     

CARD15基因StyⅠ酶切多态性与奶牛结核病易感性的相关性分析

本试验旨在探讨CARD15基因StyⅠ酶切位点多态性与云南高原奶牛结核病易感性的关联.选择云南昆明、玉溪、大理等地结核病阳性奶牛103头,结核病阴性奶牛98头,共201头为研究对象,应用创造酶切位点原理设计引物,通过PCR-RFLP与PCR直接测序法相结合的检测方法,获得CARD15基因StyⅠ酶切位点的基因型及等位基因频率,分析该位点与云南高原奶牛结核病易感性的关系.结果显示,CARD15基因的StyⅠ酶切位点存在AA、AG、GG 3种基因型,在结核病例组中AA、AG、GG基因型频率为0.03、0.42和0.55,A、G等位基因频率为0.24和0.76;在结核对照组中AA、AG、GG基因型频率为0.01、0.05和0.94,A、G等位基因频率为0.04和0.96;对多态性位点的遗传模式进行分析,最佳遗传模式为显性遗传(dominant),在此遗传模式下基因型AG-AA在病例组的频率44.7%,明显高于对照组的频率6.1%,OR(95% CI)=0.08(OR< 1),在病例组与对照组的分布之间有极显著差异(P< 0.0001).结果表明,云南高原奶牛CARD15基因StyⅠ酶切位点多态性与结核病的发生有显著关联性,且基因型AG-AA可能是结核易感型.     

乳房及肢蹄洁净度对荷斯坦奶牛体细胞数的影响

乳房炎是影响奶牛生产经济效益最重要的疾病之一,而体细胞数（SCC）是反映奶牛乳房健康及牛奶品质的重要指标。本研究通过对规模化牧场670头荷斯坦奶牛后腿上部及侧面、乳房、后腿下部进行洁净度评分,探讨乳房及肢蹄洁净度对荷斯坦奶牛乳中体细胞数的影响。试验运用SAS 8.1统计软件进行最小二乘方差分析及多重比较,除了将洁净度评分作为固定效应外,其他固定效应还包括组别效应、泌乳阶段效应及胎次效应。结果表明：①组别与胎次对体细胞评分有显著影响（P<0.05）。②泌乳阶段、后腿下部洁净度评分与乳房洁净度评分对体细胞评分有极显著影响（P<0.01）,其中后腿下部洁净度评分为4分的体细胞评分极显著高于1分和2分的（P<0.01）,后腿下部洁净度评分为3分的体细胞评分显著高于1分和2分的（P<0.05）;乳房洁净度评分为3分的体细胞评分极显著高于1分和2分的（P<0.01）;后腿上部及侧面洁净度评分对体细胞评分影响不显著（P>0.05）。③奶牛乳中体细胞数随着奶牛后腿下部洁净度评分与乳房洁净度评分的增加有上升的趋势。试验结果显示,通过对牛群身体洁净度评分,可以有效了解牛群乳房的健康状况,可为规模化牧场奶牛日常管理提供科学依据。