【Objective】This study was to explore the relationship of calving months with incidence of subclinical mastitis and milk production.【Method】DHI records from 2,564 first lactation cows were collected in an intensive dairy farms in Yancheng,Jiangsu,and the incidence of subclinical mastitis of these dairy cows were detected using mastitis testing kit.The data were statistically processed using SPSS software.【Result】The results showed that:Calving month in June related with the lowest 305-day milk yield,while August related with the highest milk yield.For other calving months,there existed significant difference almost between each month and the other month.When the Calving month was in June and July,the highest incidence of latent mastitis was observed and the lowest incidence was observed in April and May.Calving month was also significantly correlated with subclinical mastitis degree,and subclinical mastitis degree was significantly correlated with 305-day milk yield.【Conclusion】These results recommended that a better calving month would be in September or October,and thus a higher milk yield,lower subclinical incidence and lesser degree would be expected.

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.

【Objective】The influence of different calving seasons and parity on test day lactation performance was analyzed for the adjustment of guidance of diet,increasing milk production and the scientific basis to enhance the quality of raw milk.【Method】The lactation performance contains 3012 test day milk yield,fat and protein,fat-to-protein ratio,SCS,and 305-day milk yield from 408 calving cows' DHI records.【Result Objective】The results showed that different calving seasons had significant effect on test day milk yield and 305-day milk yield(P0.01),but no significant effect on fat,protein,and FPR(fat-to-protein ratio).Parity also had significant effect on all the other lactation performance(P0.01) of cows except fat(P0.05).【Conclusion】The 305-day milk yield of calving cows in Ssummer and autumn were better.The lactation performance of the second to the third calving cows increased with parity,but reduced in different degree with the increasing of parity,especially after the 5th parity.

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.

对我国南方地区某新建大型奶牛场2010年10月至2012年7月间头胎及二胎共2 006头荷斯坦牛临床乳房炎发病情况进行调查,结合病原菌感染类型结果,用x2检验分析不同胎次临床乳房炎发病次数和发病率及不同致病菌导致的临床乳房炎在不同季节和泌乳阶段发病率的差异.结果表明,该牛场一胎和二胎奶牛临床乳房炎发病率分别为11.81％和9.02％(按头数算),但二胎牛多次发生临床乳房炎的比例较大.一胎奶牛仅发现大肠杆菌和葡萄球菌单独感染及葡萄球菌-大肠杆菌混合感染3种病原菌组成类型,二胎奶牛比头胎牛增加了金黄色葡萄球菌、链球菌、酵母菌和链球菌-葡萄球菌混合感染4种类型.致病菌类型以大肠杆菌和葡萄球菌单独感染为主,一、二胎奶牛均占总发病数85％以上;季节和泌乳阶段对一、二胎奶牛临床乳房炎发病率具有显著影响(P＜0.05),一胎牛秋季发病率最高,而春季发病率最低,而二胎牛冬季发病率最高(33.33％),秋季最低(16.88％);2个胎次奶牛泌乳早期临床乳房炎发病率明显高于其他阶段.大肠杆菌和葡萄球菌在整个泌乳期均可发生,酵母菌主要出现在二胎牛泌乳中期,平均感染时间分别为(148.75±69.60)d,而金黄色葡萄球菌和链球菌主要发生在二胎牛泌乳后期,平均感染时间分别为(213.60±55.88)和(234.43±42.35)d.结果对该地区同类型奶牛场临床乳房炎防控有重要的参考价值.

The teaching process of the course Livestock Environmental Hygiene has some defects like excessive daily practical content and lack of profound,mysterious and novel stories compared to other courses of animal science,resulting in a lack of learning interest without the activation of thirst for knowledge.The characteristics of the course Livestock Environmental Hygiene and the hot issues of the field were examined carefully together with the addition of most advanced information in the field of animal science,and some ideas were proposed for research teaching for Livestock Environmental Hygiene,which would pave a sound foundation for the course research teaching.

【Objective】The effect of SCD1 different genotypes on gene expression and milk fatty acid composition was studied.【Method】Three hundred and three Chinese Holstein cows of a dairy farm were used to detect the polymorphism of the exon 5 of SCD1 gene using PCR-SSCP,and the relative gene expression was assayed by quantitative FQ-PCR,the milk fatty acid composition was assayed using the method of gas chromatography.【Result】One SNP,C878T,was detected,defining three genotypes,CC,CT and TT,with frequencies of 0.617,0.339 and 0.044,respectively.The allele frequencies of C and T were,respectively,0.787 and 0.213.Only the expression of CT genotype was significantly higher than TT genotype(P<0.05).Total saturated fatty acids of TT was significantly higher than CC or CT(P<0.05).There were highly significant differences in the fatty acid C6:0,C8:0,C14:0,C15:0 and c9t11CLA(P<0.01),and significant differences in the fatty acid C4:0,C12:0,C17:0 among these three genotypes(P< 0.05)【.Conclusion】The SNP C878T of SCD1 has a great genetic effect on the gene expression of SCD1 and the content of fatty acid in milk,it could be a useful genetic marker for milking trait in Chinese Holstein breeding.

The objective of this study was to reveal the variation for milk fat percentage for Chinese Holstein.The curve of milk fat percentage was fitted by the Wood’s incomplete gamma function model based on 33 194 test day DHI records from first lactation to third lactation for 5 dairy farms of Chinese Holstein form 2008 to 2010 in south of China.The results showed that the curve for milk fat percentage for Chinese Holstein was the typical inverted para-curve.By the fitness of curve,the first lactation was largest at 0.9820,and the third lactation was least at 0.9789.The week in lowest milk fat percentage for second lactation was most early(in the week of 16),and most late for third lactation(in the week of 19).In terms of lowest milk fat percentage,the second lactation was the largest at 3.54%,and the third lactation was the smallest at 3.45%.The Wood’s incomplete gamma function model was appropriate to fit the variation for milk fat percentage for Chinese Holstein based on all information in this study.

[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.

This study aimed to reveal the variations of daily milk yield,milk fat percentage,milk protein percentage and somatic cell score(SCS),and to establish the prediction models for these parameters in the lactation period for Chinese Holstein in southern China.A 33194-test-day dairy herd complete data from 5 Chinese Holstein dairy farms were collected in the southern China from first lactation to third lactation between 2008 to 2010 and fitted to nonlinear curve of test-day milk yield,milk fat percentage,milk protein percentage and SCS with the Wood's incomplete gamma function model.The curve of test-day milk yield for Chinese Holstein was the standard lactation curve,and the curves of milk fat percentage,milk protein percentage and SCS were the reversed standard lactation curve.The best fitness of the Wood's model occurred for milk protein percentage and daily milk yield with the lowest residual mean square,then following for milk fat percentage.The poor model fitness(R2≤0.7) was observed for SCS which residual mean square was highest.Daily milk yield peak day was accompanied with occurrences of minimal milk protein and SCS in the estimated lactation model.The minimal milk fat percentage came at the latest time of 18th week to 21th week in lactation curve.The peak milk yield was 30.4 kg·d-1 for first-parity cows,but the persistence for maintaining high milk yield and low SCS were greater than those of second-and third-parity cows in the latter lactation period,and the maximal milk yields for second-and third-parity dairy cows were 35.9 and 36.2 kg·d-1,respectively.The persistence for keeping high milk fat percentage and milk protein percentage was greater for second-parity cows than those of first-and third-parity cows in the latter lactation period.The Wood's incomplete gamma function model was appropriate to predict the variation for test-day milk yield,milk fat percentage,milk protein percentage,and was not appropriate for SCS for Chinese Holstein dairy cows in southern China.