Relationships between dairy cow mastitis and fertility management and farm performance

A field study was carried out on 38 dairy farms in the Netherlands to determine the relationship between mastitis and fertility management with 305-day milk production and gross margin. Questionnaires were used to get insight into the farmers' management. Out of 150 variables related to mastitis and fertility management, and technical and economic results, 44 variables were selected based on correlation of ≥0.25 or ≤−0.25 with milk production and/or gross margin. These variables were used in two separate partial least-squares (PLS) analyses. PLS has the advantage that it can handle a large number of variables in relation to the number of cases. The PLS-model of 305-day milk production had R² = 0.54 and showed a positive relation between 305-day milk production and awareness of the farmer regarding bulk somatic-cell count (BSCC), the goal level of the farmer for BSCC, and hygiene of the milking parlour. Fertility was negatively related to 305-day milk production, in spite of a relatively good fertility management on high-producing farms. R² = 0.46 for gross margin. The aspiration level of fertility did not seem to affect gross margin, but awareness of BSCC and calving interval (CI) had positive effects. Such awareness seemed a general parameter for good economic results, because it was correlated with different aspects of gross margin.     

The economic margins of activities of a bovine practitioner on dairy farms

Because of lower margins and market liberalisation veterinarians and farmers are increasingly negotiating rates. Therefore, the margins of veterinarians are under pressure. In addition, the sales if drugs, performance of operations or giving of advice are more and more separated. These developments give veterinarians uncertainty about the profitability of their activities for dairy farmers. Not much is known about margins on veterinary activities on dairy farms. Moreover, it is interesting to see how much margins of the bovine practitioner differ between veterinary practises and dairy farms. In this study, invoices for bovine activities of 14 veterinary practises were combined with milk production registration data of the dairy farms of these practices. This way, the gross margin per bovine practitioner could be studied for the different veterinary practise. Moreover the relation between gross margin and specification of the veterinary practise could be studied. Finally, the gross margin per dairy farm and the factors that influenced this gross margin were studied. The most important result was the observation that the gross margin per bovine practitioner was dependent on the number of dairy farms per practitioner, the margin on drugs and the region of the veterinary practise. The size of the veterinary practise, the share of the dairy farming within the practise and the source of the gross margin (drugs, time or operations) did not influence the gross margin. Variables that explained the gross margin per dairy farm were, amongst others, the number of dairy cows, the milk production level of the farms and participation in PIR-DAP (a system to support the veterinarians herd health and management program). There is no relation of gross margin per dairy farm and the veterinary practise or region.     

Evolution of farm management, nitrogen efficiency and economic performance on Dutch dairy farms reducing external inputs

The implementation of the statutory Mineral Accounting System (MINAS) in the Netherlands in the period 1998–2003 required large reductions in nutrient inputs of dairy farms. Patterns in farm management adjustments throughout 6 years and their effectiveness in terms of nitrogen use efficiency (NUE) and economic performance were evaluated for 45 commercial farms participating in a regional nutrient management project.

Six groups of farms were identified that differed in initial NUE and the change therein. Three groups of farms that were able to rapidly reduce fertilizer N input and establish a consistent farm management strategy were most successful in improving NUE. These farms had a higher gross margin per 100 kg milk than farms without a consistent strategy. The three effective strategies were primarily characterized by (i) continuous, gradual adjustment of the integrated farm management combined with a slight reduction in milk production per ha (re-balancing) versus increasing productivity per animal, thereby reducing maintenance N requirements, while (ii) maintaining or (iii) increasing the production intensity per ha. It was concluded that different approaches to improve NUE can be successful, also in economic terms, although a direct relationship between NUE and gross margin was not observed. The probably implicit choice for adoption of a strategy may be governed by farm endowment and the farmer's skills and objectives.     

Influence of genetic merit and environment on somatic cell counts of Holstein-Friesian cows

Financially, mastitis is one of the most important diseases affecting dairy cattle in the United Kingdom. Seven commercial farms were monitored over a 2.5 year period and data from 1040 cows were included in a study that examined both straw yard and cubicle housing systems. The influence of genetic merit for milk production (PIN(95) and PTA(f+p)) on somatic cell counts (SCC) as an indicator of mastitis under commercial farm conditions was assessed. The mean genetic potential ( poundPIN(95)) was 39.0 (+/-0.80) and the mean 305-day milk yield (kg) was 7980 (+/-54.2). In all, 5618 monthly records of SCC and 1040 records of 305-day SCC were included in the analysis. A multiple regression model was used to assess the influence of genetic merit and the level of concentrate intake on SCC (the log(10) transformation was used) under the two housing systems. Significant interactions between genetic merit and housing system, and concentrate intake and housing system were found. Log(10) SCC increased with genetic merit when cows were housed in straw yard accommodation, but decreased when cows were housed in cubicle accommodation. The increase in SCC with concentrate feeding was higher for straw yards. For parity 2 animals, there was a significant positive correlation between PIN(95) and SCC (r(p)=0.184, P=0.003) but the correlations between 305-day milk production and SCC were negative for animals greater than parity 2.     

非遗传因素对荷斯坦牛305天产奶量的影响

为了探讨非遗传因素对荷斯坦牛305 d产奶量的影响,笔者收集了新疆呼图壁种牛场牧一场1996-2005年度荷斯坦奶牛生产性能记录资料,通过采用SAS 8.1软件的最小二乘方差分析,分析了年度、季节、产犊间隔和胎次对荷斯坦牛305 d产奶量的影响。结果表明,年度、产犊间隔和胎次对产奶量的影响差异极显著（P<0.01）;季节对产奶量的影响差异不显著（P>0.05）。本研究结果为进一步对遗传参数估计提供效应值划分的依据。     

Impact of feeding pattern and feed purchase on area- and cow-related dairy performance of organic farms

Livestock production and ruminants in particular are an integral part of the organic mixed farming concept. In this paper, the feeding patterns of 26 organic dairy farms in two different regions in Germany are analysed, with particular emphasis on the amount and proportion of concentrates and purchased feed related to the dairy performance expressed per cow and hectare. Calculated on an energy basis (MJ NEL), the annual average milk yield of 6737 kg cow^− 1 is derived from roughage (74%), concentrates and cobs (23%), and commercial processing by-products (e.g., spent grains) (3%). Per cow and year, 937 kg dry matter (DM) (range: 0–2724 kg) of concentrates are fed with an intensity of 135 g kg^− 1 milk (range: 0–378 g kg^− 1). Approximately 65% of the concentrates and commercial processing by-products are purchased. The area-related milk yield is almost 7000 kg ha^− 1. For fodder production, 0.96 ha per cow is needed, of which 0.85 ha is farm land. The equivalent production area for purchased fodder is 0.11 ha. In the analysed region in northwestern Germany, most correlations between milk yield and analysed feeding parameters are close and significant. This is in contrast to the region in the south, where the variability of amount and proportion of the different feed types is predominantly independent of the milk yield. Intensification of dairy production to increase milk performance using a higher proportion of concentrates and purchased feed at some of the analysed farms needs to be carefully assessed according to the organic farming profile.     

Milk production and lactation length in Ankole cattle and Ankole crossbreds in Rwanda

This study assessed daily milk yield (DMY), 100-day (MY100), and 305-day (MY305) milk yield, and lactation length (LL) in purebred Ankole cattle and Ankole crossbreds, and the influence of environmental factors on these traits. Milk yield data were obtained for 865 cows and 1234 lactations and analyzed using a mixed linear model. The overall least squares mean of DMY, MY100, and MY305 across breed groups was 2.7 L (N = 1234, SD = 1.7), 262 L (N = 959, SD = 176), and 759 L (N = 448, SD = 439), respectively, while the average lactation length was 256 days (N = 960, SD = 122). All factors included (breed group, season and year of calving, and parity) were significant for yield traits, except season of calving for MY305. First-parity cows had the lowest milk production, and fourth-parity cows the highest. For all traits, pure Ankole cows had the lowest milk yield. Among the crossbreds, there was no significant difference between Ankole × Friesian, Ankole-Jersey mother × Sahiwal sire, and Ankole-Sahiwal mother × Jersey sire, or between Ankole × Sahiwal and Ankole-Sahiwal mother × Sahiwal sire. It was concluded that Ankole crosses with Friesian or Jersey can be beneficial, even under a management system of limited nutrition as in Rwanda.

     

中国荷斯坦奶牛不同地区、泌乳天数及胎次的产奶量校正系数研究

本研究通过对规模化牧场测定日数据进行分析,旨在估计不同地区305 d校正产奶量对应泌乳天数(DIM)的校正系数与胎次校正系数。利用Wood(不完全伽玛)模型对来自不同温度带9个参考群11 749头荷斯坦奶牛2010－2020年间的683 160条测定日产奶量拟合泌乳曲线,估计泌乳曲线参数,计算头胎牛和经产牛1~305 d泌乳天数对应的校正系数,分别分析参考群和验证群305 d校正产奶量和305 d实际累积奶量的差异;利用SAS 9.2中混合线性模型对1~6胎至少有前5个胎记录的牛估计305 d奶量的胎次效应值,并计算1~6胎各胎次的乘法校正系数;比较传统系数和新系数校正结果的差异。结果表明:①参考群头胎牛和经产牛中,泌乳曲线方程的拟合度R²范围分别为0.4593~0.4913和0.5796~0.6341,泌乳高峰日分别为79~85和53 d,泌乳高峰奶量分别为33.1~34.4和46.0~48.6 kg;②对于参考群,头胎牛和经产牛校正系数分别在泌乳≥90 d和泌乳≥30 d基本趋于一致,头胎牛和经产牛泌乳≥60 d的305 d校正产奶量均趋近于305 d实际累积奶量,奶量差值分别在100和200 kg以内;③对于验证群的305 d校正产奶量,头胎牛泌乳≥150 d和经产牛泌乳≥180 d的泌乳天数校正系数适用性更佳,305 d校正产奶量与305 d实际累积奶量比值高于79%;④1~6胎的胎次校正系数分别为1.2121、1.0380、1.0063、1.0000、1.0220和1.0290;⑤与传统系数相比,新泌乳天数校正系数校正效果更好,头胎牛和经产牛新系数校正的305 d奶量较305 d实际累积奶量相差分别在900和700 kg以内;利用新胎次校正系数,2~4胎产奶量可较为准确地校正到5胎成年当量。本研究结果表明,定期更新305 d校正产奶量的泌乳天数与胎次校正系数,便于准确地将不同泌乳天数、不同胎次状态下泌乳牛的产奶量调整到同一基准上,从而更好地比较奶牛个体泌乳性能的高低,为牧场管理提供参考依据。     

Risk of removal and effects on milk production associated with paratuberculosis status in dairy cows

OBJECTIVE: To determine effects on production and risk of removal related to Mycobacterium avium subsp paratuberculosis (MAP) infection at the individual animal level in dairy cattle. DESIGN: Longitudinal study. ANIMALS: 7,879 dairy cows from 38 herds in 16 states. PROCEDURE: A subset of dairy cattle operations that participated in the National Animal Health Monitoring System Dairy 2002 study was evaluated via a serum ELISA for antibodies against MAP and categorized according to ELISA score. Dairy Herd Improvement Association records were obtained to collect current and historical lactation data and removal (ie, culling) information. Production variables were evaluated on the basis of serum ELISA category. RESULTS: Cows with strong positive results had mature equivalent (ME) 305-day milk production, ME 305-day maximum milk production, and total lifetime milk production that were significantly lower than cows in other categories. No differences were observed for ME 305-day fat and protein percentages, age, lactation, and lactation mean linear somatic cell count score between cows with strong positive results and those with negative results. After accounting for lactation number and relative herd-level milk production, cows with strong positive results were significantly more likely to have been removed by 1 year after testing. CONCLUSIONS AND CLINICAL RELEVANCE: Without management changes designed to reduce the farm-level prevalence of MAP infection, paratuberculosis will continue to reduce farm income by decreasing milk production and potentially increasing premature removal from the herd.     

Changes in productivity and profitability of wool-growing farms that follow recommendations from agricultural and veterinary studies

Objective To estimate the changes in productivity and profitability in a group of wool-growing farms as they adopted major recommendations from agricultural and veterinary studies.
Farms Four wool-growing farms in south western Victoria were selected from the clients of the Mackinnon Project, a farm consultancy service run from the University of Melbourne. Each farm had closely followed recommended procedures, kept comprehensive financial and physical records and had been clients for at least 5 years. The comparison group was the South Western Victoria Monitor Farm Project (SWVMFP), about 45 farms in the same region as the study farms that were monitored annually by Agriculture Victoria.
Procedure For a 7-year period, the financial and physical performance of both groups of farms was estimated. Stocking rate, wool production, gross farm income, farm operating costs, net farm income and return on assets were compared.
Results Mean gross farm income of the four study farms steadily rose from 86% of the average SWVMFP farm before the adoption of recommendations to an average of 155%. During the same period, net farm income rose from 70% to 207% of the average of the SWVMFP. Return on asset of the four farms rose irregularly from 26% to 145% of the average of the SWVMFP. Farm operating costs on the four farms were higher than for the SWVMFP group, but the ratio of costs remained relatively constant.
Conclusion The adoption of proven research results was associated with large increases in net farm income. An increase in gross income, rather than a reduction in costs was the main reason for this. Research results offer a way to increase the financial viability of wool-growing farmers, many of whom are currently unable to maintain their lifestyle, resources and infrastructure.     

Effect of prepartum intramammary treatment with pirlimycin hydrochloride on prevalence of early first-lactation mastitis in dairy heifers

OBJECTIVE: To determine whether prepartum intramammary treatment of dairy heifers with pirlimycin hydrochloride would reduce the prevalence of intramammary infection (IMI) and lower the somatic cell count (SCC) during early lactation or improve 305-day mature equivalent milk production. DESIGN: Prospective clinical trial. ANIMALS: 183 Holstein-Friesian heifers (663 quarters) from 2 dairy farms. PROCEDURE: Heifers were assigned to treatment and control groups. Treated heifers received a single 50-mg dose of pirlimycin in each mammary quarter approximately 10 to 14 days prior to parturition. Prepartum mammary gland secretions and postpartum milk samples were collected for bacterial culture. Postpartum milk samples were also collected for determination of SCC or California mastitis testing and were tested for pirlimycin residues. Mature equivalent 305-day milk production data were recorded. RESULTS: Treated heifers in herd A had a higher overall cure rate, higher cure rates for IMI caused by coagulase-negative staphylococci (CNS) and Staphylococcus aureus, lower SCC, and lower prevalence of chronic IMI, compared with control heifers. Treated heifers in herd B had a higher overall cure rate and cure rate for IMI caused by CNS, compared with control heifers, but postpartum California mastitis test scores and prevalence of chronic IMI did not differ between groups. Mature equivalent 305-day milk production did not differ between herds or treatment groups. No pirlimycin residues were detected in postpartum milk samples. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that prepartum treatment of dairy heifers with pirlimycin may reduce the prevalence of early lactation IMI, particularly IMI caused by CNS, without causing pirlimycin residues in milk.     

The economics of dairy production.

The structure of the dairy farm industry has been changing rapidly in recent years. Milk production has increased, with dramatic increases in milk produced per cow and with a steep decline in number of milk cows and fewer farms with larger herds. The change in dairy farm size has not been uniform across regions. The growth in farm size has occurred much more rapidly in the Pacific and South regions than in the traditional dairy-producing regions (Upper Midwest, Northeast, and Corn Belt). Using USDA data to examine costs and returns over time reveals that the incentives to produce milk have been much greater in the Pacific and South regions in recent years. Although the cash costs are similar across regions, accounting for all costs including unpaid factors such as labor and capital replacement yields a clear advantage for the Pacific region. Dairy farm size and cost of production are jointly determined. The incentive to increase farm size is derived from the economies of size that may be achieved by spreading the capital, labor, and managerial costs across more units of milk production. Empiric evidence from previous studies indicates a declining cost of production over a large range of herd sizes. Even in the presence of a flat average cost curve, the incentive to maximize farm income provides incentive to increase production. Adjustment costs may fix dairy production facilities in their current use. Those firms facing higher adjustment costs because of individual or regional characteristics or because of different timing of growth will be smaller or grow more slowly than if they faced smaller adjustment costs. This situation may explain the continued lag of farm size and technology adoption in the traditional dairy producing regions relative to the Pacific and South regions where the more recent population growth coincided with the presence of modern, large-scale production technologies. Finally, dairy marketing policies almost certainly have affected the structure and regional pattern of dairy farm size and production. For the most part, however, the policy effects have been of indirect nature. The Pacific region has grown (despite having the lowest average price) by taking advantage of economies of size by specializing in milking cows. The United States dairy industry is a technologically advanced, well-managed, and economically important sector of United States agriculture. Future challenges include the ability to remain viable economically while dealing with environmental and social sustainability issues in the form of new constraints from formal policies and from consumer perceptions.     

Udder health and risk factors for subclinical mastitis in organic dairy farms in Switzerland

A study was performed in 1997 to estimate the prevalence and to investigate the etiology of subclinical mastitis in Swiss dairy herds managed under guidelines of controlled organic farming. It was planned as a longitudinal study over a period of 1 year and included a stratified random sample of 152 certified organic farms and 1907 cows. Two farm visits (the first from June to October when cows were on pasture, the second from January to March when cows were confined to barns) were performed on each farm. At each visit, farm management and individual-cow data (with emphasis on milking procedures and udder sanitation) were recorded. California mastitis tests (CMTs) were performed on each udder quarter of all cows in lactation. Milk samples with CMT >1+ were submitted for somatic cell counting (SCC), bacteriological examination and to test for antibiotic susceptibility. The SCC and germ-cell counts of monthly bulk-tank milk samples were available through Dairy Inspection and Advisory Services and milk production data of 567 herd-book cows were available from breeding associations. Possible individual and environmental predictors of subclinical mastitis were identified using logistic models adjusted for clustering of the data at herd and cow levels. Data were analyzed separately for cows from 7 to 100 and from 101 to 305 days post partum. Prevalences of subclinical mastitis at the quarter level were 21.2% for lactation period 7–100 days and 34.5% for 101–305 days post partum. The geometric mean SCC in bulk-tank milk samples was 85.6×10³ cells/ml. Samples at 7–100 and 101–305 days post partum were positive for Staphylococcus aureus in 16.0 and 7.4%, for coagulase-negative Staphylococci in 51.5 and 50.6%, for Streptococcus agalactiae in 0.0 and 0.8%, for other Streptococci in 19.4 and 15.6%, for E. coli in 1.0 and 0.4%, and for Corynebacterium bovis in 25.7 and 45.1%, respectively. Risks of subclinical mastitis increased significantly with increasing days post partum and advancing age of cow. Cows that were sampled when staying in alpine dairies had considerably higher risks of subclinical mastitis than cows staying in home barns. Significantly lower risks of subclinical mastitis were observed in farms where CMT was performed regularly as a control measure. Bacteria in milk from cows with mastitis exhibited antibiotic resistance at a comparable frequency as found previously in conventional farms.     

Losses of adult sheep due to ovine Johne's disease in 12 infected flocks over a 3-year period

OBJECTIVE: To measure the biological and financial impact of ovine Johne's disease (OJD) mortalities on 12 infected flocks within the endemic area of southern New South Wales over a 3-year period. DESIGN AND POPULATION: An observational study was conducted over a 3-year period from 2002 to 2004 on sheep from 12 OJD-infected flocks from southern NSW. Flocks ranged from between 3,500 and 20,000 sheep. At the start of the study owner estimates of OJD mortality were 5% or greater. METHOD: Annual mortality rates were estimated from farm records provided by owners. The proportion of OJD mortalities was assessed after histological examination of tissues collected from dead and moribund sheep during 5-day necropsy inspections conducted in autumn, winter, spring and summer in 2002. The financial impact was estimated using a gross margin analysis for each of the three study years and by placing a financial value on the necropsied sheep. RESULTS: On the 12 farms, the average OJD mortality rate was 6.2% (range 2.1% to 17.5%) in 2002, 7.8% (range 1.8% to 14.6%) in 2003 and 6.4% (range 2% to 11.9%) in 2004. The average decrease in gross margin due to OJD infection on a farm in 2002 was 6.4% (range 2.2% to 15.4%), 8.5% (range 3.1% to 15.8%) in 2003 and 7.4% (range 1.5% to 15.4%) in 2004. This equates to an average reduction in annual income of $13,715 per farm per year. OJD losses accounted on average for two thirds of the total estimated financial loss associated with sheep deaths. CONCLUSION: This study demonstrates the significant biological and financial impact of OJD on sheep flocks. These findings are of relevance to all Australian sheep flocks infected or at risk of OJD infection.     

中国西门塔尔牛育种效果分析

采用6个国家级种畜场1980～2000年间的数据对中国西门塔尔牛21年来的育种效果进行分析。对主要性状的遗传力、遗传相关进行了估计．并计算出总性能指数。所有性状均采用动物模型并利用MT-DFREML(多性状非求导)软件进行分析。     

Incorporation of observations with different residual error variances into existing complex test-day models

Automated milking systems (AMS) have become popular on dairy farms. Due to a different test-day recording scheme the variation of test-day observations differ from AMS differ from those of conventional milking system (CMS). An approach is presented for upgrading the genetic evaluation model for production traits milk, protein and fat yield by including residual covariance matrices for AMS and CMS test-day observations. Residual variances were found to be 16–37% smaller for milk and protein yields and 42–47% larger for fat yield when recorded under AMS herds compared to CMS herds. Daily heritability was higher for milk and protein yield and lower for fat yield when traits were recorded under AMS compared to recording under CMS. No difference was found between AMS and CMS in 305-day heritability for milk and protein yield except for second lactation milk yield. 305-day heritability for fat was lower for all lactations under AMS.     

Economic aspects of reproductive failure in dairy cattle. I. Financial loss at farm level

Some years ago, systematic research was initiated to improve quantitative insight into the economic impact of diseases and disease control in livestock. This paper deals with the financial loss at farm level caused by reproductive failure in dairy cattle. Economic calculations concerning the calving interval of cows which differ in age, relative production level and persistence of milk production during lactation were made. On average, an optimal interval of 1 year or less was established, while the loss per day lengthening of the interval (norm-loss) amounted to 1–2 Dutch guilders (Dfl.). Also, 676 norm-losses due to forced replacement because of reproductive failure were determined, dependent on age and relative production level of the culled cow and average herd life of the farm. On average, this norm-loss was determined to be almost Dfl. 500 per culled cow. Based on 71 farms in an investigation in the province of Overijssel, total loss per farm was determined, using the calving interval data, forced replacement data and norm-loss rate described above. On average, the calculated loss amounted to Dfl. 63 per cow per year, of which Dfl. 35.50 resulted from sub-optimal calving interval and Dfl. 27.50 from forced replacement due to reproductive failure. Costs for veterinary treatment and drugs were not included in these elements. Total loss due to reproductive failure was estimated to average about Dfl. 80 per cow per year, which equals about 2% of the gross production value or 10% of an average farmer's income.Finally, considerable differences in loss between farms have been determined. The difference between the 20% of farms with the highest and the 20% of farms with the lowest calculated loss is even more than the average loss. Thus improvment may be achieved on many farms, e.g., with the help of a herd health programme.     

An overview of fertility statistics and milk production data of 15 dairy operations in southeast Friesland

In 1988 the collection of data on fertility and milk production was initiated by the veterinary practice in Oosterwolde in the context of a veterinary herd health programme. An automated management and production control programme, VAMPP, was used for this purpose. Although it is not possible to give the precise effect of veterinary herd health programmes on technical farm results, because a control group is lacking, it is possible to discern trends in data collected over 10 years. The field data, show that the first insemination pregnancy rate decreased by 10.1%, from 55.5% to 45.4% (p = 0.002). The number of cows showing first heat decreased by 1.3% (p = 0.46) between 0-15 days post partum, 2.6% (p = 0.41) between 15-30 days post partum, by 4.9% (p = 0.07) between 30-50 days post partum and by 11.4% (p = 0.008) between 50-70 days post partum. In the same period, the milk production increased from 7558 kg 4% fat corrected milk in 305 days to 8744 kg (p = 0.0004). These data may be useful for veterinarians working in veterinary herd health on dairy farms. Furthermore, the described trends and especially the discussed differences between farms may be a stimulus for both farmers and veterinarians to continue with herd health programmes.     

Targeted application of anthelmintics to control trichostrongylosis in dairy goats: result from a 2-year survey in farms

The targeted application of anthelmintic treatments represents one of the current available solutions to slow down the development of anthelmintic resistance within worm populations. Within an experimental flock of dairy goats, control of gastrointestinal parasitism by such selective treatments, targeting the most receptive animals within a flock, was previously found to be effective and to have no detrimental consequences on milk production. The objectives of the current study were to verify the validity of this method in farm conditions. Eleven dairy goat farms from three main areas of production in France were surveyed for 2 years. In six farms, the survey was prolonged for a third year. During year 1, systematic treatments were applied during the grazing season whereas in year 2 and or year 3, treatments were given exclusively to the goats in first lactation and to the multiparous ones with the highest potential of milk production. The level of nematode infection was measured four times per year through individual coproscopical examinations and the mean annual production of milk was recorded. No significant changes in egg excretion nor in milk production were noticed in any farm during years 2 or 3 after switching from the systematic to the selective mode of treatments. These results confirmed that targeted application of anthelmintics might represent a way to combine the control of trichostrongyles and the prevention of anthelmintic resistance.     

关于我国奶产业稳定持续发展的几个问题

该文从我国奶的增产速度，影响奶品消费水平的因素，我国农村奶牛饲养户对奶业发展的作用，科学饲养技术与优质青粗饲料生产的推广，加快对现有奶牛品种的改良进展等几个方面论述了我国奶产业的稳定持续发展。