[Objective] The objective of this study was to investigate the effects of FADS2 c.908 C＞T mutation on milk production traits and fatty acids compositions in milk of Chinese Holstein.[Method] A total of 865 Chinese Holstein cows were genotyped using Sequenom MassARRAY (Sequenom Inc.,San Diego,CA) for the SNP mutation of FADS2 c.908 C＞T,and the associations between SNPs and milk production traits,fatty acids composition,and unsaturated indexes of fatty acids in milk were analyzed by the least squares method.[Result] There were three genotypes (CC,CT and TT) of FADS2 c.908 C＞T.CT was the dominant genotype,and allele C was dominant allele with the frequency of 0.592.The FADS2 c.908 C＞T showed significant association with daily milk yield,fat percentage,protein percentage,total solid content,and SCS (P＜0.05).The individuals with genotype CC had lower daily milk yield,lactose content,and total solid content than genotypes TT (P＜0.05),but higher SCS than genotypes CT and TT.The FADS2 c.908 C＞ T also showed very significant associations with percentages of C14∶ 1,C16∶ 0,C16∶1,C18∶0,C18:3 and unsaturated indexes of C14,C16 and C18 (P＜0.01).The individuals with genotype TT had higher content of C16∶1,and unsaturated indexes of C16 and C18 than genotypes CC and CT (P＜0.01).[Conclusion] The FADS2 c.908 C＞T mutation had significant genetic effects on milk production traits and fatty acids composition in milk.The individuals with genotype CC had higher daily milk yield,total solid,content of C16∶1,and unsaturated indexes of C16 and C18.

The meteorological chromatography was used to determine the fatty acid composition of a whole lactation period of 64 Chinese Holstein cows in a large ranch of Yangzhou region. The results showed that in a lactation period, according to the length of carbon chain, fatty acids could be divided into two categories, under 16 carbon chain fatty acid and more than 16 carbon chain fatty acids. The under 16 carbon chain length fatty acid increased synthesis in milk had a certain contact with the milk production increasing. And more than 16 carbon chain length fatty acid with lactation month and its percentage increase in milk have certain contact with milk yield decreasing. In addition, the trend towards two types of fatty acid composition ratio in the entire lactation period coincided contrary. That proportion of under 16 carbon chain length fatty acid and more than 16 carbon chain fatty acids had a deifnite link with breast milk fat synthesis metabolism in different lactation stage control. Also, cows in different stages of lactation fatty acids may be involved in regulating the genes expression of breast cells and networks control of that may inlfuence each other between them.

[目的]FADS2是多不饱和脂肪酸合成中关键的限速酶之一,可催化食物中亚油酸(LNA,C18∶2n6)合成γ-亚麻酸(GLA,C18∶3n6)、二十碳五烯酸(EPA,C20∶5n3)、二十二碳六烯酸(DHA,C22∶ 6n3)等长链脂肪酸.试验旨在探讨中国荷斯坦牛FADS2基因3'端非编码区SNP突变对乳中脂肪酸含量的影响.[方法]随机选择20头无亲关系的中国荷斯坦牛样本,用直接测序列法检测FADS2基因3'端非编码区SNP突变位点.再以江苏某大型奶牛场5 51头中国荷斯坦牛为材料,用飞行时间质谱法对前期发现的2个SNP位点进行检测,同时利用最小二乘模型分析了SNP突变及其单倍型对乳中脂肪酸含量及其不饱和指数的影响.[结果]中国荷斯坦牛FADS2基因3'端非编码区存在3个SNP突变位点:c.1571 A＞G、c.2743 A＞G、c.2776 A＞G.c.1571 A＞G位点GG型为优势基因型,基因型频率为0.800,G为优势等位基因,基因频率为0.887.c.2776 A＞G位点AA为优势基因型,基因型频率为0.673,A为优势等位基因,基因频率为0.819.x2检验表明:c.2776 A＞G位点基因型分布均符合Hardy-Weinberg平衡(P＞0.05),而c.1571 A＞G位点基因型分布均偏离Hardy-Weinberg平衡(P＜0.05).FADS2基因c.1571A＞G位点与c.2776 A＞G位点间连锁不平衡系数r2为0.028,未达到显著水平(P＞0.05).c.1571A＞G位点与c.2776 A＞G位点有3种单倍型,GA、GG和AA频率分别为0.705、0.181和0.114.多因素方差分析表明:FADS2-1571对C14∶1含量、C14和C18不饱和指数的影响达到极显著水平(P＜ 0.01),对C18∶0、SFA和MUFA含量的影响达到显著水平(P＜0.05).GG型个体乳中C14∶1含量、C14和C18不饱和指数显著高于AG型(P＜0.05).FADS2-2776位点对C16∶1含量、C16和C20不饱和指数的影响达到极显著水平(P＜0.01),对C14∶1含量的影响达到显著水平(P＜ 0.05),GG型个体乳中C16∶1含量、C16和C20不饱和指数显著高于AG型和AA型(P＜ 0.05).同时,FDAS2-1571-2776单倍型对C16∶1含量和C20不饱和指数的影响达到显著水平(P＜0.05),单倍型GG型个体乳中C16∶1含量和C20不饱和指数显著高于GA型和AA型(P＜0.05).[结论]FADS2基因3 '端非编码区SNP突变对中国荷斯坦牛乳中脂肪酸组成有重要影响.在进一步验证其功能情况下,可作为影响中国荷斯坦奶牛乳脂肪酸组成的主效基因加以利用.

Milk yield and component content of Holstein cows under intensive feeding in south China were detected, and the effect of different lactation stages, parity and milk yield on conventional milk composition was analyzed in this study, which was aimed to study the change law of conventional milk composition and related index.The results showed that: the southern Holstein cattle in different lactation stages throughout the lactation period and different levels of milk production of milk composition and acidity in milk had a significant effect, and the changes in each component content in milk was closely related to the stage of lactation.

This study aimed to analyze the impact of different pasteurization temperatures and storage periods on fatty acid composition of pasteurized milk.Raw milk was pasteurized at 65 ℃ for 30 min or at 85 ℃ for 15 s,sealed and then stored at 4 ℃.The fatty acid composition of raw milk and pasteurized milk during storage was analyzed by gas chromatography.The results indicated no significant difference in fatty acid composition was present among pasteurized milks treated at different temperature(P 0.05).In addition,the fatty acid composition of pasteurized milk was quite stable during storage.However,the content of fatty acid C4:0 in pasteurized milk treated at 65 ℃ for 30 min and stored for 8 d was significantly higher than in raw milk.This might be due to the bacterial proliferation.The content of CLA declined following temperature processing and storage whereas no significant difference was found(P 0.05).This study indicated that pasteurization had no effect on the contents of characteristic fatty acids in the milk.Therefore pasteurization could be used as an effective way to produce milk rich in CLA.

This study was aimed to detect the single nucleotide polymorphism(SNPs) of Holstein cows diacylglycerol acyltransferase 1(DGAT1) gene in exon 8,and to predict the protein structure and function caused by the mutations and discuss the evolution relationship of DGAT1.PCR-SSCP combined with sequencing was used to detect the SNPs in exon 8 of DGAT1 gene.Bioinformatics approach was used to predict the physicochemical properties and structures of DGAT1 protein.The approach was also used to analyze the amino acid homology of DGAT1 between different species,and to build the evolutionary tree.The PCR-SSCP analysis results showed that a double mutations existed in exon 8 of DGAT1 gene,namely M694 and M695.The prediction of protein structure and function displayed that the double mutation had no influence on the physicochemical properties and structures of the protein,but led to the changes in the component of its protein function domain.The evolution analysis results indicated that amino acid sequence homology of DGAT1 between Holstein cows and sheep was the highest(99.1%),and the homology between Holstein cows and chimpanzees was the lowest(65.3%).

IL-8 gene in cattle was investigated.By means of bioinformatics method,mainly focused on analyzing its encoding protein including its structure,physical and chemical properties,signal peptide,transmembrane structure,subcellular localization,secondary structure,higher structure and its evolution relationship with other species.The results indicated that cattle IL-8 protein was a stable hydrophilic transmembrane protein,located at cellular exterior.The secondary structure was primarily composed of α-helix and random coil.It had two serines and two threonines,which might become phosphorylation sites of the protein kinase.Besides,it had twelve glycosylation sites.The analysis of conservative structure domain showed that cattle IL-8 protein had a SCY zinc finger conservative structure domain.The amino acid adjacency phylogenetic tree analysis showed that cattle IL-8 gene had the closest genetic relationship and high homology with ovines.

The article is intended to study the links between pathogenic bacteria infection and mastitis.Based on the isolation and identification of bacteria and colony count method 636 milk samples were analyzed,including the normal breast,invisible,clinical mastitis mastitis milk.The result shows that: The ranch mastitis was dominated by a single bacterial infection,and with the rising in the proportion of Lactobacillus,the reducing the proportion of Staphylococcus as well as an increase in the aerobic bacterial count,mastitis levels gradually increased.The colonies in normal milk,invisible and clinical mastitis milk had a significant difference compared with the positive(P<0.01).Results suggest that: with the increase of the proportion of Mycobacterium and the total number of bacterial colony the incidence of mastitis also increase there′s a positive correlation between them.

To explore the relationships of the degree of mastitis,total bacteria count,and bacterial infection pattern with milk composition and somatic cell count,the identifying medium and plate counting method were used for identification of bacteria and total bacteria count,and subclinical mastitis and dairy herd improvement(DHI) were also tested in 187 dairy cows with different degree of mastitis in this experiment.The results showed that: 1) Patterns of bacterial infection exerted insignificant effects on somatic cell count,milk protein and fat rate(P>0.05),but had significant impact on the determination of daily milk yields(P<0.05);2) Total bacteria count had no significant effect on protein content(P>0.05),but had extremely significant effect(P<0.01) on daily milk yield,milk fat content and somatic cell count;3) Under the same bacterial infection pattern,total bacteria count had significant impact(P<0.05) on the determination of daily milk yields,somatic cell count,milk protein and fat content;4) the degree of mastitis had significant effect(P<0.05) on somatic cell count,daily milk yield,milk fat and protein content,and the total bacteria count;5)The somatic cell count had extremely significant effect(P<0.01) on daily milk yield milk fat and protein content.These findings demonstrated that pattern of bacterial infection exerted insignificant effects on somatic cell count,and the degree of mastitis and somatic cell count had significant effect on milk component.We could use somatic cell count and the total number of colonies to monitor the mastitis risks and the possible changes in milk composition.

[Objective]This study aimed to analyze the change of fatty acid composition in yogurt pro- cessed with different inoeulum of lactobacillus after maturity and during storage. [Method]The milk was inoculated with2 %,3 % and 4% starter culture, respectively. The matured yogurt was sealed in 4 ℃ refrigerator during storage. The fatty acid composition of the yogurt and raw milk was tested with gas chromatography method. [Result]The result showed that: after the yogurt fermented completely, the content of short chain fatty acid C4 : 0,C6 : 0 and C8 : 0, medium chain fatty acid C12 : 0, C14 : 0, C14 : 1, C16 : 0 and C16 : 1, as well as the long chain fatty acid C18 : 3, C20 : 3, C20 : 4 and C22 : 6 had significant difference (P〈0.05) or highly significant difference (P〈0.01)between the raw milk and the yogurt with 3 different inoculation volume, and the content of conjugated linoleic acid (CLA) was also increased. The yogurt with 3 % inoculation volume had the most obviously change. The yogurt with 3 different inoculation volume had no significant change during storage. [Conclusion]The research suggested that yogurt could reduce the content of C14 : 0 and C16 : 0, which suffering people from cardiovascular diseases, and increase the content of the polyunsaturated fatty acid C22 : 6 (DHA), which was beneficial for people. The yogurt with 3 % inoculation volume was the most effective.

【Objective】The purpose of this study is to find and establish a simple and efficient method used to detect the fatty acid composition and content in the milk.【Method】Gas chromatography(GC-FID) method was used to separate the milk fatty acid composition by using the Agilent HP-88 fatty acid methyl esters capillary column and temperature programmed method,quantitative retention time was used for quantify by qualitative and peak area percentage method.【Result】The results showed that the fatty acid in milk was well separated.The recovery and precision of detection method were 99.588% and 2.600,respectively,with a high accuracy and repeatability.【Result】The experimental method could be used as a milk fatty acid detection technology for promotion and application.

Abstrcat The morphology and ecology characters on some sheep populations in China were studied to construct the principal component, the principal component values were studied with the R-type hierarchical clustering method to analyze the genetic differentiation among populations. This study proved that the result of principal component analysis of morphology and ecology characters on some sheep populations in China was conformed to the result of the known sheep phylogenetic system in China. The ecology factor was also an important character for the breed region classification.