奶牛日粮添加豆油和胡麻油对有机物和纤维物质消化率的影响

选用4头装有永久性瘤胃瘘管的初产奶牛采用4×4拉丁方设计，研究不添加油脂（CK）、添加4％豆油（LOC1）、4％胡麻油（LOC2）以及2％豆油+2％胡麻油（LOC3）对DM、OM、NDF、ADF瘤胃表观消化率及全肠道消化率的影响。结果表明：在60%高粗料日粮基础上添加4%豆油、亚麻油或二者的混合物，对奶牛干物质采食量没有影响。与对照组相比,添加油组DM、OM、NDF、ADF的瘤胃表观消化率和全肠道消化率都有降低的趋势，但差异不显著（P＞0.05），3个添加油组之间差异也不显著（P＞0.05）。     

Use of a computer-aided design to develop a stress simulation model for lactating dairy sheep

A mechanistic model of the mammary gland able to simulate the milk production process in dairy sheep was constructed by using a computer-aided simulation via object-oriented modelling. Such an approach, rather innovative in animal science, allows the construction of complex models avoiding the use of non-linear differential equations. The model was structured into three sub units: alveolar, energy and milk sub-models. It was used to mimic the milk production process of dairy sheep. Moreover, the model was used to simulate the effects on milk production of external stresses represented by the variation in milking frequency and a reduction in the energy supplied to the animal with the diet.     

Stochastic simulation of Manchega sheep breed selection scheme. Impact of artificial insemination, progeny testing system and nucleus size on genetic progress and inbreeding

Manchega is a local Spanish sheep breed located in the region of Castilla la Mancha, Actually there are 0.8 million of milked ewes. The selection scheme of Manchega breed (ESROM) started in 1988, involving a selection nucleus composed by 103,887 ewes distributed in 106 flocks. Results obtained from the ESROM has been moderate in comparison with other similar European schemes. By this and other reasons, to develop a specific tool to study the ESROM system seems to be necessary.

The objectives of this work were to develop a genetic simulation model based on the ESROM real system and to study the effects on genetic progress and inbreeding level achieved from different rates of AI used, the progeny test system and the selection nucleus size.

An additive infinitesimal model was assumed for the trait 120 days Total Milk Yield (TMY). Five alternatives selection criteria (two per each group of animals to be selected), differentiated on their selection intensities, were associated to the selection of lambs for future artificial insemination rams, natural mating rams and ewes. All selection decisions were based on periodical genetic evaluations (BLUP), using an animal model with repeated measures. 60 specific cases were studied, each one with 20 replicates.

An average true genetic progress per year ranging from 1.04% to 2.10% in AI rams and 0.59% to 2.11% in ewes were observed. Results of phenotypic progress varied from 0.44% to 1.83% per year. True inbreeding levels of ewes at year 17 were between 0.218% and 1.879%.

The model used had the expected behavior. In general, the studied selection scheme had its better results (maximum genetic progress), when AI rate was equal or greater than 50%, a greater number of new rams were tested per year (75 and 44) and a selection nucleus size equal or greater than 9000 ewes (30 flocks). Selection intensity of natural mating rams had a great impact on the genetic progress, especially when the use of AI was low. The greater the nucleus size, the higher the genetic progress, but an operative scheme from around 9000 initial ewes could be established.

Results observed demonstrate the existence of some critical areas, which could be verified on the real system in order to improve their effectiveness. In this framework, the ESROM could develop two complementary strategies: to improve the selection system of Natural Mating Rams (selecting only sons of AI rams) and/or to increase the levels of AI until 50%.     

Isolation,Drug Sensitivity Test and Construction of Prokaryotic Expression Vector of Virulence Genes of Enterococcus from Dairy Cow with Mastitis in Gansu Province

The aim of this study was to isolate Enterococcus in clinical dairy cow mastitis,detect its drug resistance and virulence genes,a total of 93 milk samples were collected from 41 dairy cosw with clinical mastitis in eastern,central and western regions of Gansu province,and then construct a prokaryotic expression vector for virulence genes.This experiment used selective medium to isolate and purify bacteria.16S rRNA and biochemical experiments combined method to identify the isolated strains.16 antibiotics were selected for drug sensitivity test,and conventional PCR method was used to detect the carrying of 11 virulence genes.Finally,the detected virulence genes with immunogenicity were selected for the construction of prokaryotic expression vectors.The separation and identification results showed that 18 strains of Enterococcus were isolated and identified from the 93 milk samples,which were divided into 9 species.Drug susceptibility results showed that most of the isolates were multiple resistant to bacteria,accounting for 88.89%.No vancomycin-resistant Enterococcus was found,vancomycin sensitivity rate was 94.12%,and all isolates were resistant to at least one antibiotic.Virulence gene test results demonstrated that 11 virulence genes were detected,the detection rate of cob gene (44.44%) was the highest,the detection rates of efaA,hyl,ccf and esp genes were 33.33%,27.78%,27.78% and 22.22% respectively,the detection rates of Asa1,cylA,EF3314 and gelE genes were all 16.67%,while Ace and cylM genes had the lowest detection rate (11.11%).The virulence genes combination was different due to different strains.Ace and gelE genes with immunogenicity were selected and the prokaryotic expression vector pET32a-Ace and pET32a-gelE were successfully constructed.The results provided basic data and biological materials for subsequent mapping of regional epidemiology of cow mastitis in three regions and preparation of corresponding antibodies and subunit vaccines.     

A comparison of the effects of parenteral and oral administration of supplementary vitamin E on plasma vitamin E concentrations in dairy cows at different stages of lactation

As a result of research conducted in the US, recommendations for dry cow vitamin E intakes have increased seven fold there, however there has been no change to recommendations in the UK. As part of a larger study comparing the impact of existing UK and new US recommended vitamin E intakes on the health and fertility of commercial dairy cows in the UK, a study was set up to investigate the effect of route of supplementation and stage of lactation, over a 21 day period, on the response to mega-supplementation of cattle receiving supposedly adequate vitamin E. The study assessed the response of dry, peak lactation and mid lactation cows to in-feed or parenteral vitamin E supplementation (7 animals per treatment/lactation stage group) by measuring plasma and milk vitamin E concentrations, blood glutathione peroxidase (GSH-Px) activity and milk yields over a 21 day period. Plasma vitamin E concentrations were significantly influenced by a time, stage and treatment interaction (P = 0.046). Both dry and lactating animals had significantly higher plasma vitamin E concentrations at some time points in the parenteral supplemented cows compared to the in-feed supplementated animals (P ≤ 0.011 and P < 0.01, respectively). Milk vitamin E concentrations did not significantly differ between lactation stages but treatment had a significant effect on concentrations (P < 0.008) when lactation stage was removed from the model. There was no significant difference in milk yield between treatment groups. A significant relationship between plasma and milk vitamin E concentrations was only found in the parenterally supplemented cows (r = 0.435, P < 0.001). In cattle with intakes greater than the ARC recommendations, measurement of plasma vitamin E concentration may be of limited value in determining whether there has been a response to supplementation. The relationship between plasma and milk vitamin E concentrations is too poor for milk vitamin E concentrations to be used as a proxy for plasma vitamin E.     

Heat stress decreases plasma vitamin C concentration in lactating cows

Heat stress causes oxidative stress, which decreases plasma levels of vitamin C, an antioxidative vitamin in pigs and poultry. We investigated the plasma vitamin C concentration in lactating cows exposed to a hot environment temperature. In the first experiment, plasma vitamin C concentrations of 8 lactating cows were measured in summer and autumn. The concentration was found to be significantly lower in summer. The second experiment was performed using 4 lactating cows in a crossover design. The ambient temperature was set at 18 °C in the control treatment and at 28 °C in the heat-stressing treatment. Milk yields and feed intake tended to be lower in the stressing than control treatment. Rectal temperature and respiration rate were significantly (P < 0.05) higher in the heat-stressing treatment. The plasma vitamin C concentration was significantly (P < 0.05) lower in the heat-stressing period. These results indicate that heat stress decreases the plasma vitamin C concentration. Dietary supplementation with vitamin C may be beneficial for lactating cows in hot weather.     

Productivity and socio-economic profile of dairy cattle farmers amongst rural smallholder communities in northern Vietnam

The objective of this field questionnaire survey was to describe the productivity and socio-economic profile of dairy cattle farmers in northern Vietnam considering regional differences in rural smallholder farming communities which have been targeted by a governmental dairy development policy. Using two-stage cluster sampling, a total of 99 dairy farming households (11 per commune) were recruited from 9 of 32 communes in Ba Vi District, Ha Tay Province, northern Vietnam. The results from this study indicate that there were regional differences in relation to basic management practices such as effective utilisation of agricultural by-products for feeding and hygiene practices. These can be explained by variation amongst the regions with respect to environmental factors affecting agricultural activities such as constraints on land use and access to water resources. There were also regional differences in the use of governmental support such as agricultural extension services and financial institutions. These can be attributed to proximity of the communities to each of the extension institutions as well as the phased and community-specific approach to the provision of governmental financial support for dairy development.     

Effect of prepartum compensatory nutrition regimen on metabolism and performance of dairy cows

The impact of closely controlled energy management during the dry period upon general peripartum metabolism and the subsequent lactation was evaluated in multiparous dairy cows. Eight lactating, pregnant Holstein cows were paired according to current milk production and body condition score and assigned to either the control or the stair-step compensatory nutrition (SSCN) regimen 16 weeks prior to expected calving date. Control cows were fed according to National Research Council [National Research Council., 2001. Nutrient Requirements of Dairy Cattle. 7th rev. ed. Natl. Acad. Sci., Washington, DC.] recommendations and for ad libitum intake during late lactation and the far-off dry period. The SSCN cows were subjected to dietary energy restriction [80% of net energy for lactation requirements (NE_L)] during late lactation in order to maintain body weight, followed by realimentation (130% of NE_L) during the far-off dry period to induce a compensatory response. A common diet was fed thereafter. The SSCN cows gained less body condition during late lactation and tended to gain more body condition during the far-off dry and transition periods than control cows. There was no difference in dry matter intake during the prepartum transition period and early lactation. Milk yield was not affected by treatment. Serum nonesterified fatty acids (NEFA) were not altered by dietary treatment during late lactation and the dry period; however NEFA were lower in SSCN cows at week 4 of the subsequent lactation. Serum insulin was higher in SSCN cows 8 weeks prior to parturition (end of restriction), tended to be higher at 4 weeks (end of realimentation) before calving, and was also higher at week 12 of early lactation. An SSCN regimen stimulated body condition gain of mature dairy cows during the dry period, did not affect periparturient nutrient metabolism, and led to modest improvements in metabolic parameters later in the subsequent lactation.     

干奶期不同能量摄入对围产期乳牛血液葡萄糖胰高血糖素和胰岛素浓度的影响

将围产期健康乳牛30头随机分为3组，分别于产前第28d开始饲喂标准日粮（能量摄入i00％组）、标准日粮增加20％的日粮（能量摄入120％组）和标准日粮减少20％的日粮（能量摄入80％组），产后备组乳牛均饲喂标准泌乳日粮，至产后第56d结束，观察干奶期不同能量摄入水平对围产期健康乳牛血液葡萄糖、胰高血糖素和胰岛素浓度的影响。结果表明，产前低能饲喂可以增加围产期乳牛血浆葡萄糖浓度，干奶期不同能量摄入水平对围产期健康乳牛血液葡萄糖、胰高血糖素和胰岛素浓度起重要调节作用。     

Cumulative discounted expressions of dairy and beef traits in cattle production systems

Gene-flow methodology was used to calculate the cumulative discounted expressions (CDE) for annual/lactation, replacement heifer, cull cow, birth, yearling, and slaughter traits in alternative cattle production systems. Generic equations were presented and parameters representing dairy-beef production systems in Ireland and Brazil were inputted. Cumulative discounted expressions using input parameters from a hypothetical purebred dairy production system with poor cow longevity were also calculated. Cumulative discounted expressions were calculated assuming either an initial purebred or crossbred mating within each production system. Absolute and relative differences in CDE existed among trait categories across the three alternative production systems investigated. For example, the CDE of beef-related traits accruing from an initial purebred mating ranged from 0.42 to 0.75 CDE of an annual/lactation trait across the three contrasting systems investigated which differed in various input parameters. Such variation may alter the relative emphasis of traits on overall profitability thereby contributing to genotype by environment interactions. The results of this study highlight the necessity to consider auxiliary traits in sire selection over and above those representing the principal intended use of the sire. This was particularly so for integrated dairy-beef cattle production systems.