Reproductive loss in high-producing dairy cattle: where will it end?

The dairy industry in the United States has changed dramatically in the last decade. Milk production per cow has increased steadily because of a combination of improved management, better nutrition, and intense genetic selection. Dairy farms are larger, and nearly 30% of the dairy cows in the United States are on farms with 500 or more cows. The shift toward more productive cows and larger herds is associated with a decrease in reproductive efficiency. Cows with the greatest milk production have the highest incidence of infertility, but epidemiological studies suggest that, in addition to milk production, other factors are probably decreasing reproductive efficiency in our dairy herds. The reproductive physiology of dairy cows has changed over the past 50 yr, and physiological adaptations to high milk production may explain part of the reproductive decline. Critical areas for new research include control of the estrous cycle, metabolic effects of lactation on reproduction, mechanisms linking disease to reproduction, and early embryonic mortality. Solving reproductive loss in dairy cows will not be easy because only a small number of research groups study reproduction in postpartum dairy cows. Therefore, the present research base will need to be expanded. For this to occur, research funding must be increased above its current level and a renewed emphasis must be placed on solving the emerging crisis of infertility in dairy cows.     

Factors affecting reproductive performance of dairy cows

We conducted two studies to determine how herd management practices and traits of individual cows affect performance of the herd and of the cow within a herd. Management practices, reproductive performance of the herd, and relationships between management and reproductive performance were characterized on 83 dairy farms with 7596 cows. Data included 21 management variables (e.g., facilities, herd health program, estrous detection program) and 8 performance variables obtained from Dairy Herd Improvement or unofficial records (e.g., size of herd, production, days open). Although varying among herds, annual average herd incidences of reproductive disorders and reproductive performance were similar to those reported. Managerial practices influenced incidences of retained placenta and uterine infection, days open of cows not bred and of all cows, services per conception, and percentages of herd open more than 100 days and culled for low production. Veterinarian was the most consistent variable influencing herd reproductive performance. Data also were collected from production and lifetime records of 2532 cows in 19 herds. Reproductive performance was affected by season of calving, production, maturity, and reproductive disorders. Several cows with extremely poor reproductive records were maintained.     

Can we identify key characteristics associated with grazing-management dairy systems from survey data?

Discriminant analysis was used to identify farms using confinement and grazing-production systems from mail survey data of 2074 dairy farmers in Pennsylvania, Vermont, Virginia, and North Carolina. Survey respondents included 45.1% of the farms using confinement management; 13.5% of farms practicing intensive grazing, defined as moving cows to new pasture at least every 3 d; and 41.4% of farms using nonintensive grazing. Farmers using confinement management had significantly more cows, higher milk production, more crop acreage, higher debt, used automatic takeoff milking units (ATO), fed total mixed rations (TMR), and were more satisfied. In general, dairy farmers who grazed their milking cows had smaller herds, fewer acres, but had more acres per cow and made less use of technology. However, farmers practicing intensive grazing were significantly younger, more educated, less experienced, more likely to use computers, and farmed less acreage than other graziers or farmers on confinement farms. The discriminant function correctly classified 70% of the total sample when divided into confinement and overall grazing categories. However, the discriminant function correctly classified only 36% of intensive-grazing farms in comparison to confinement farms. Significant variables identified using ordinary least squares as being related to confinement management were milk per cow, acres of corn, use of ATO and TMR, debt greater than 40%, and residence in North Carolina. Significant variables associated with grazing management were acres of pasture, future use of pasture, education, and residence in Vermont. The analysis indicated that the discriminant function could correctly classify confinement and nonintensive-grazing management but was unable to reliably differentiate between confinement and intensive-grazing farms.     

Determinants of antimicrobial treatment for udder health in Danish dairy cattle herds

Societal pressure to limit the use of antibiotics in livestock production systems, including dairy cattle systems, is consistently increasing. To motivate farmers to reduce antibiotic usage, it is important to understand the factors that determine whether a cow will be treated with antibiotics or not. If farmers' usual practices regarding antibiotic treatments are taken into account, they may be motivated to adopt control measures that can facilitate prudent use of antibiotics and are at the same time cost-effective. In this study, we analyzed database recordings of milk yield and somatic cell count from the routine milk recording scheme, clinical registrations of mastitis and PCR results, and cow factors such as days in milk and parity in relation to antibiotic treatments for 518 dairy herds in Denmark. Farm-wise logistic regressions were used to predict antimicrobial treatment based on these factors. The resulting regression coefficients of 422 herds were further analyzed by principal component analysis and clustering to determine the driving predictors for treatment in different groups of farms. The results showed that determinants that were most important for predicting antibiotic treatments vary from one farm to another. Health indicators such as PCR or somatic cell count were most indicative for treatment on some farms, whereas other groups seemed to depend more on production factors (milk yield) or later culling of the cows. This shows that farmers behave differently and differences can be identified in register data. This information can be considered when developing cost-effective herd-specific control measures of mastitis to promote prudent use of antibiotics in Danish dairy cattle farms.     

Survey of nutritional management practices and metabolic disorders in West Virginia dairy herds

Sixteen farmers, representing three major dairy counties in West Virginia, were interviewed to determine current dairy management practices. Herd health records were used to determine the incidence of metabolic and digestive disorders. All feedstuffs used on these farms were sampled for chemical analyses. The total number of cows on the 16 farms surveyed was 1870 with an average herd size of 117 and 6387 kg milk produced per cow per year. Fourteen of the 16 farmers used forage testing services, obtained professional advice on feeding and nutrition, and attempted to feed according to production. Eleven of sixteen farmers increased grain 2 weeks prior to calving and all gradually adjusted the intake of grain to cows recently freshened. Ration imbalance problems included both excesses and deficiencies of energy, protein, phosphorus, and calcium. Excess calcium, phosphorous, and crude protein were correlated (P less than .01, r2 = .74) with the incidence of fat cows. The incidence of metabolic disorders in these herds was low to average and the most prevalent management problem encountered was low butter fat.     

Evaluation of milk yield losses associated with Salmonella antibodies in bulk tank milk in bovine dairy herds

The effect of Salmonella on milk production is not well established in cattle. The objective of this study was to investigate whether introduction of Salmonella into dairy cattle herds was associated with reduced milk yield and determine the duration of any such effect. Longitudinal data from 2005 through 2009 were used, with data from 12 mo before until 18 mo after the estimated date of infection. Twenty-eight case herds were selected based on an increase in the level of Salmonella-specific antibodies in bulk-tank milk from <10 corrected optical density percentage (ODC%) to ≥70 ODC% between 2 consecutive three-monthly measurements in the Danish Salmonella surveillance program. All selected case herds were conventional Danish Holstein herds. Control herds (n=40) were selected randomly from Danish Holstein herds with Salmonella antibody levels consistently <10 ODC%. A date of herd infection was randomly allocated to the control herds. Hierarchical mixed effect models with the outcome test-day yield of energy-corrected milk (ECM)/cow were used to investigate daily milk yield before and after the estimated herd infection date for cows in parities 1, 2, and 3+. Control herds were used to evaluate whether the effects in the case herds could be reproduced in herds without Salmonella infection. Herd size, days in milk, somatic cell count, season, and year were included in the models. Yield in first-parity cows was reduced by a mean of 1.4kg (95% confidence interval: 0.5 to 2.3) of ECM/cow per day from 7 to 15 mo after the estimated herd infection date, compared with that of first-parity cows in the same herds in the 12 mo before the estimated herd infection date. Yield for parity 3+ cows was reduced by a mean of 3.0 kg (95% confidence interval: 1.3 to 4.8) of ECM/cow per day from 7 to 15 mo after herd infection compared with that of parity 3+ cows in the 12 mo before the estimated herd infection. We observed minor differences in yield in second-parity cows before and after herd infection and observed no difference between cows in control herds before and after the simulated infection date. Milk yield decreased significantly in affected herds and the reduction was detectable several months after the increase in bulk tank milk Salmonella antibodies. It took more than 1 yr for milk yield to return to preinfection levels.     

Efficiency in milk production on Reunion Island: Dealing with land scarcity

This paper aims to analyze efficiency on dairy farms in Reunion Island, a French overseas district located in the Indian Ocean. On this island, dairy farming is promoted with financial and technical support from the European Union, with the French and local governments aiming at reducing dependency on imports of milk powder and dairy products and creating employment. A critical factor for increasing the local milk production is the limited availability of arable land because of the small size and the volcanic nature of the island. In this paper, we study the efficiency levels of dairy production on 34 farms by using a data envelopment analysis approach. The average technical efficiency score of farms, assuming constant returns to scale, was 0.927, with 19 out of 34 farms not being efficient. The technical efficiency with a variable returns to scale specification was 0.951. The efficiency with which farmers used their land (subvector efficiencies) was estimated in a second model. The average subvector efficiencies calculated with constant returns to scale and variable returns to scale models were lower than the technical efficiencies. The farmers on the efficiency frontier had a relatively higher milk production, milk production per cow, and land surface than those who were less efficient. A policy promoting better use of the land on inefficient farms should increase the milk production-to-land ratio. Possible on-farm strategies are improved feeding systems, farms having their own heifer breeding, and improved genetics.     

Management practices and reported antimicrobial usage on conventional and organic dairy farms

The primary objective was to compare reported antimicrobial usage between conventional and organic dairy farms. A secondary objective was to contrast selected management characteristics of conventional and organic dairy herds. A questionnaire was administered on site to selected dairy farmers located in Michigan, Minnesota, New York, and Wisconsin. Organic herds (n = 32) were smaller and produced less milk than conventional herds (n = 99). Lactating cows in organic dairies were more likely to be housed in tie stalls, whereas most conventional dairies housed cows in free stalls and milked in a parlor. Total mixed rations and purchased feeds were used on more conventional dairy farms compared with organic dairy farms. Conventional dairy producers were more likely to use advice from veterinarians for recommendations of treatment, and organic dairy producers were more likely to rely on advice from other farmers. Based on recall of antibiotic usage in the previous 60 d, 5.1, 84.9, 9.1, and 0.9% of farmers with conventional herds reported treatment of none, 1 to 10%, 11 to 25%, and >25% of milk cows, respectively. Most organic farmers (90.6%) reported no antibiotic treatments of milk cows, whereas 9.4% reported treating 1 to 10% of milk cows. Ceftiofur was the most commonly reported antibiotic for both farm types. Milk replacer containing antibiotics was reportedly used on 49.5% of conventional herds but only on one organic herd (3.1%). Antibiotics were used in heifer calves on 74.7% of conventional herds versus 21.9% of organic herds. Antibiotics to treat mastitis were used on 79.8% of conventional herds but on none of the organic herds. Most organic farms were in compliance with standards in advance of implementation of regulations.     

Association of paratuberculosis sero-status with milk production and somatic cell counts across 5 lactations,using multilevel mixed models,in dairy cows

The aim of this work was to investigate associations between individual cow Mycobacterium avium ssp. paratuberculosis (MAP) seropositivity, 305-d corrected milk production, and somatic cell count during 5 lactations lifespan in Portuguese dairy herds using multilevel mixed models. We used MAP serum ELISA (Idexx MAP Ac, Idexx Laboratories Inc., Westbrook, ME) results (n = 23,960) from all the 20,221 adult cows present in 329 farms and corresponding 47,586 lactation records from the National Dairy Improvement Association. Cows and farms were classified as positive or negative. Multilevel mixed models were used to investigate the association of cow MAP status with variation in milk production and somatic cell count. Cow MAP status, farm status, and lactation number were considered as independent variables. A quadratic function of lactation number was used to mimic the effect of lactation order on milk production. The models considered 3 levels: measurement occasion (level 1) within cow (level 2) and cow within farm (level 3). Four final models were produced, including all herds and cows, to address the effect of farm status (models 1 and 2) or the effect of cow status (models 3 and 4) on the outcome variables. Our results show that MAP status affects milk production. Losses are detectable from third lactation onward. During the first 5 lactations, positive cows accumulated an average loss of 1,284.8 kg of milk when compared with the negative cows. We also observed that somatic cell counts were higher in positive cows and a positive interaction occurs between cow status and lactation number, suggesting a positive association between MAP infection and increased somatic cell counts. Our results are in line with previous studies, suggesting a possible positive relation between cow milk production and susceptibility to MAP infection.     

Checking into China's cow hotels: Have policies following the milk scandal changed the structure of the dairy sector?

China's milk scandal is well known for causing the nation's largest food safety crisis and for its effect on thousands of children. Less, however, is known about the effect on the other victim: China's small dairy farmers. Although small backyard producers were not the ones that added melamine to the milk supply, the incomes of dairy farmers fell sharply after the crisis. In response, one of the actions taken by the government was to encourage small dairy producers to check into production complexes that were supposed to supply services, new technologies, and provide for easy/bulk procurement of the milk produced by the cows of the farmers. Because both farmers and their cows were living (and working) away from home, in the rest of the paper we call these complexes cow hotels. In this paper we examine the dynamics of China's dairy production structure before and after the milk scandal. In particular, we seek to gain a better understanding about how China's policies have been successful in encouraging farmers to move from the backyard into cow hotels. We also seek to find if larger or smaller farmers respond differently to these policy measures. Using data from a sample of farmers from dairy-producing villages in Greater Beijing, our empirical analysis finds that 1 yr after the milk scandal, the dairy production structure changed substantially. Approximately one quarter (26%) of the sample checked into cow hotels after the milk scandal, increasing from 2% before the crisis. Our results also demonstrate that the increase in cow hotel production can largely be attributed to China's dairy policies. Finally, our results suggest that the effects of government policy differ across farm sizes; China's dairy policies are more likely to persuade larger farms to join cow hotels. Apparently, larger farms benefit more when they join cow hotels. Overall, these results suggest that during the first year after the crisis, the government policies were effective in moving some of the backyard farmers into cow hotels (although 60% farmers remained backyard producing).     

Evaluation of factors associated with increased dairy cow mortality on United States dairy operations

Dairy cow mortality is an increasingly severe problem for the US dairy industry. The objective of this study was to examine a variety of herd management practices and herd characteristics to identify factors associated with increased cow mortality in US dairy herds. The National Animal Health Monitoring System's Dairy 2002 study surveyed dairy operations in 21 major dairy states. The complete data set included results from 953 dairy farms with a minimum of 30 dairy cows per farm. Associations between dairy cow mortality and 119 a priori-selected management practices or characteristics of 953 operations were evaluated. Eighty of the 119 risk factors explored in a univariate analysis met initial inclusion criteria for further evaluation of association with dairy cow mortality. A multivariable analysis was conducted to explore more complex relationships. The final multivariable model included 7 representative variables: herd levels of respiratory disease, lameness, and antibiotic use for treating sick cows, the percentage of culled cows less than 50 d in milk, the average calving interval, the use of a total mixed ration, and the region of the country. Increased odds of a greater level of mortality on farms was associated with greater percentages of lameness, respiratory disease, and sick cows treated with antibiotics, demonstrating the influence of physical derangements and disease on dairy cow mortality. Increased odds of a greater level of mortality was also associated with feeding a total mixed ration, culling fewer cows in early lactation, and herds located in western, midwestern, and southeastern regions relative to the northeastern United States, pointing to the importance of management decisions and operation characteristics on mortality outcomes. Further, an important interplay between facets of health and management on dairy cow mortality was suggested through the inclusion of the calving interval, with a longer calving interval leading to increased odds of a greater level of mortality on farms. Analysis of a variety of herd characteristics and practices with nationally representative data suggests that several health problems in tandem with aspects of operational construct and management are associated with increasing mortality.     

Analysis of reproductive performance of lactating cows on large dairy farms using machine learning algorithms

The fertility of lactating dairy cows is economically important, but the mean reproductive performance of Holstein cows has declined during the past 3 decades. Traits such as first-service conception rate and pregnancy status at 150 d in milk (DIM) are influenced by numerous explanatory factors common to specific farms or individual cows on these farms. Machine learning algorithms offer great flexibility with regard to problems of multicollinearity, missing values, or complex interactions among variables. The objective of this study was to use machine learning algorithms to identify factors affecting the reproductive performance of lactating Holstein cows on large dairy farms. This study used data from farms in the Alta Genetics Advantage progeny-testing program. Production and reproductive records from 153 farms were obtained from on-farm DHI-Plus, Dairy Comp 305, or PCDART herd management software. A survey regarding management, facilities, labor, nutrition, reproduction, genetic selection, climate, and milk production was completed by managers of 103 farms; body condition scores were measured by a single evaluator on 63 farms; and temperature data were obtained from nearby weather stations. The edited data consisted of 31,076 lactation records, 14,804 cows, and 317 explanatory variables for first-service conception rate and 17,587 lactation records, 9,516 cows, and 341 explanatory variables for pregnancy status at 150 DIM. An alternating decision tree algorithm for first-service conception rate classified 75.6% of records correctly and identified the frequency of hoof trimming maintenance, type of bedding in the dry cow pen, type of cow restraint system, and duration of the voluntary waiting period as key explanatory variables. An alternating decision tree algorithm for pregnancy status at 150 DIM classified 71.4% of records correctly and identified bunk space per cow, temperature for thawing semen, percentage of cows with low body condition scores, number of cows in the maternity pen, strategy for using a clean-up bull, and milk yield at first service as key factors.     

Economic effect of short (35-d) compared with conventional (60-d) dry period management in commercial Canadian Holstein herds

The Canadian dairy industry operates under a supply management system with production quotas (expressed in kilograms of butterfat per day) owned by dairy producers. Any management strategy influencing production responses must, therefore, be evaluated to estimate its effects on quota needed to sell the milk produced. In the present study, half of the cows from 13 commercial herds (850 cows, average of 70 cows per herd) were assigned to be managed for a short dry period (SDP; 35 d dry) and the other half was managed for a conventional dry period (CDP; 60 d dry) to evaluate the economic impact of a steady state involving either CDP or SDP. Economic variables included in the partial budget were: variations in revenues from milk and components as well as animals sold; costs related to feeding, reproduction, replacement, housing, and treatments. All variables were first estimated on a cow basis for each herd individually, and average results were used to calculate the partial budget for an average herd. Yearly milk and component yields per cow increased, which implies that fewer cows are required to produce the same amount of quota. Accordingly, 2 scenarios were investigated: in the first one, available quota was kept constant, and herd size was adjusted to avoid over-quota production. Consequently, the partial budget was calculated considering that 5 fewer cows were present in the herd. In this situation, switching to an SDP management increased net annual income for the farm by $2,677 (Can$), which represents $41.38 per cow. In the second scenario, the number of cows was kept constant, but additional quota (5.5 kg/d, $25,000/kg) was bought to allow selling all of the milk produced. In this case, net farm income was increased by $17,132 annually with SDP, which represents $245.18 per cow. This budget includes interest on the purchase of quota. A comparison of partial budgets for individual herds involved in the study revealed considerable variation among herds. Switching from a CDP to a SDP management would be beneficial for average dairy herds in eastern Canada.     

Drying-off practices on Swiss dairy farms: Status quo and adoption potential of integrating incomplete milking

Drying-off practices to reduce milk production before dry-off are gaining attention because high milk yields at dry-off are becoming more common and increase the risk to cow health and welfare during the dry period. Incomplete milking for the last days before dry-off is one approach for reducing milk production. We conducted an online survey to determine the currently used drying-off practices on Swiss dairy farms and to identify the adoption potential of integrating incomplete milking before dry-off. In March 2021, the online survey was sent to a representative sample of 1,974 Swiss dairy farmers. A total of 518 completed questionnaires were analyzed. The mean number of dairy cows per farm was 39 (range: 11–140 cows). Thirty-five percent of cows produced considerable quantities of milk (>15 kg/d) at dry-off, and milk yield at dry-off increased with increasing annual milk yield. Abrupt dry-off was applied on 45% of the farms. The participants reported observing behavioral changes of cows such as increased vocalizations and decreased lying time associated with dry-off. Selective dry cow therapy was applied on 74% of the farms, and 44% of the participants indicated the use of antibiotics at dry-off as being “rather often,” “often,” or “always.” Correlation analysis revealed that with increasing annual milk yields, the frequency of observed behavioral changes and antibiotic use at dry-off increased as well. Therefore, drying-off approaches that reduce milk production while supporting cow welfare are needed. We found that farmers showed an interest in testing the presented drying-off approach of incomplete milking. In addition, the farmers indicated that they would be more willing to test incomplete milking before dry-off if it became available for automated use in milking parlors or robots. Uncertainties regarding udder health appeared to be the main barrier for the adoption potential of this approach.     

Strategies used by dairy family farmers in the south of Brazil to comply with organic regulations

The aims of this study were to investigate the environmental, feeding, and health management of organic (ORG) family dairy farms in the south of Brazil in comparison with conventional (CONV) farms, and to assess their degree of compliance with Brazilian organic legislation and the strategies they adopt to accomplish this (n = 17 per group). During 2 visits to each farm in March and September, 2010, observations were made on the environment, feed, and health management, followed by bulk milk testing, clinical evaluation, and breed assessment of each individual cow, and an evaluation of diseases and treatments reported within the period. Additional data were collected directly from the farmers through direct interviews. The number of lactating cows was, on average, 11 (range 5 to 19) in the ORG and 16 (range 7 to 42) in the CONV herds. The ORG herds presented a lower percentage of the Holstein breed; whereas CONV herds were predominantly Holstein, in the ORG herds, only 2 herds were 100% Holstein and the remaining herds were crosses of Holstein, Jersey, and Gir (Bos indicus) cattle. Milk production per cow was lower (10.2 vs. 15.1 ± 1.22 L/cow, respectively) in ORG than in the CONV farms. The ORG farms offered less concentrate feed than CONV farms and had better pasture management. Organic farmers reported using phytotherapic and homeopathic products, and pasture management as a strategy to keep infection levels of endo- and ectoparasites low, whereas CONV farmers regularly used anthelmintics and acaricides. Milk production was lower in ORG than in CONV farms, but cow health and condition scores were broadly similar, indicating that the with these strategies ORG farms were able to secure levels of animal welfare comparable with CONV farms while complying with organic regulation, although at the cost of lower cow productivity.     

The effect of bovine viral diarrhea virus introduction on milk production of Dutch dairy herds

Dairy cows are negatively affected by the introduction of bovine viral diarrhea virus (BVDV), and consequently, produce less milk. Existing literature on potential milk production losses is based on relatively outdated data and hardly evaluates milk production loss in relation to a new BVDV infection in a surveillance system. This study determined the annual and quarterly loss in milk production of BVDV introduction in 3,126 dairy herds participating in the Dutch BVDV-free program between 2007 and 2017. Among these herds, 640 were “breakdown-herds” that obtained and subsequently lost their BVDV-free status during the study period, and 2,486 herds obtained and retained their BVDV-free status during the study period. Milk yields before and after BVDV introduction were compared through annual and quarterly linear mixed models. The fixed variables for both models included herd type (breakdown-herd or free-herd), bovine viral diarrhea status (on an annual and quarterly basis), year, season, and a random herd effect. The dependent variable was the average daily milk yield on the test day. To define the possible BVDV-introduction dates, 4 scenarios were developed. In the default scenario, the date of breakdown (i.e., loss of the BVDV-free status) was assumed as the BVDV-introduction date. For the other 3 scenarios, the BVDV-introduction dates were set at 4, 6, and 9 mo before the date of breakdown, based on the estimated birth date of a persistently infected calf. In the default scenario, the loss in milk yield due to BVDV introduction occurred mainly in the first year after breakdown, with a reduction in yield of 0.08 kg/cow per day compared with the last year before breakdown. For the other 3 scenarios, the greatest yield reduction occurred in the second year after BVDV introduction, with a loss of 0.09, 0.09, and 0.1 kg/cow per day, respectively. For the first 4 quarters after BVDV introduction in the default scenario, milk yield loss was 0.14, 0.09, 0.02, and 0.08 kg/cow per day, respectively. These quarterly results indicated that milk yield loss was greatest in the first quarter after BVDV introduction. Overall, BVDV introduction had a negative, but on average a relatively small, effect on milk yield for herds participating in the BVDV-free program. This study will enable dairy farmers and policymakers to have a clearer understanding of the quantitative milk production effect of BVDV on dairy farms in a control program.     

Dairy farm cost efficiency

A stochastic cost equation was estimated for US dairy farms using national data from the production year 2000 to determine how farmers might reduce their cost of production. Cost of producing a unit of milk was estimated into separate frontier (efficient) and inefficiency components, with both components estimated as a function of management and causation variables. Variables were entered as impacting the frontier component as well as the efficiency component of the stochastic curve because a priori both components could be impacted. A factor that has an impact on the cost frontier was the number of hours per day the milking facility is used. Using the milking facility for more hours per day decreased frontier costs; however, inefficiency increased with increased hours of milking facility use. Thus, farmers can decrease costs with increased utilization of the milking facility, but only if they are efficient in this strategy. Parlors compared with stanchions used for milking did not decrease frontier costs, but decreased costs because of increased efficiency, as did the use of a nutritionist. Use of rotational grazing decreased frontier costs but also increased inefficiency. Older farmers were less efficient.     

Breeding practices on Illinois Holstein farms

Questionnaires requesting breeding information were mailed to 1,148 Illinois Holstein herds in the Dairy Herd Improvement program. A total of 591 questionnaires (51%) were returned. Dairy producers with herds producing over 7,100 kg of milk returned 64% of their questionnaires whereas 34% of dairy producers with herds producing less than 5,900 kg returned their questionnaires. State average and standard errors were: 23 +/- 1 bulls used per 100 cows, 78 +/- 2% dairy producers select the bulls, 96 +/- 1% herds use artificial insemination, 2.1 +/- .1 artificial insemination organizations per herd, 29 +/- 2% herds participate in young sire testing programs, 87 +/- 1% farmers consider calving ease indicators in mating heifers, and 17 +/- 2% farmers consider calving ease indicators in mating cows. Breeding practices positively associated with increasing rolling herd average milk production were number of bulls per herd and per 100 cows, self as bull selector, use of artificial insemination, number of artificial insemination organizations, and participation in young sire testing programs. Three breeding practices were negatively associated with increasing rolling herd average milk production: artificial-insemination technician as bull selector and consideration of calving ease for mating heifers and cows. Dairy producers also were asked to rate the emphasis placed on traits in bull and cow selection. For bull selection, udder conformation and Predicted Difference milk were most important. In cow selection, milk production, followed by udder conformation, feet and legs, and fat percentage, was the most important trait.     

Economic effects of exposure to bovine viral diarrhea virus on dairy herds in New Zealand

The economic loss to dairy farmers associated with bovine viral diarrhea virus (BVDV) is believed to be high in New Zealand, but no estimates are yet available. The aim was therefore to estimate the economic loss associated with BVDV in dairy herds in New Zealand. Bulk tank milk (BTM) from a random sample of 590 herds from the Northland, Bay of Plenty, and Waikato regions was tested for antibody against BVDV. The inhibition percentage (sample to positive ratio), based on a threshold validated in an earlier study, was used to indicate herd-level infection. Herd reproductive indices, herd lactation-average somatic cell counts, and herd average production of milk solids were regressed on BTM inhibition percentage. Herd averages of the overall annual culling rate, the rate of culling because of failure to conceive, the proportion of physiological inter-service intervals, the first-service conception rate, the pregnancy rate at the end of mating, and somatic cell counts were not associated with BVDV antibody in BTM. Abortion rates, rates of calving induction, the time from calving to conception, and the number of services per conception increased, however, whereas milk production decreased with increasing BVDV antibody in BTM. The results indicated significant reproductive and production loss associated with the amount of BVDV antibody in BTM. Total loss attributable to infection with BVDV was similar to reports from other countries and estimated as NZ$87 per cow and year in affected herds, and NZ$44.5 million per year for the New Zealand dairy industry based on an estimated 14.6% affected herds. The loss estimate excludes added cost and negative consequences with respect to animal welfare attributable to increased induction rates, and a greater incidence of production disease because of BVD-induced immune suppression.     

The association of herd milk production and management with a return-over-feed index in Ontario dairy herds

Associations of herd milk production and management variables to a return-over-feed (ROF) herd profit index were examined among 95 dairy farms. The ROF index is derived from 2 important determinants of profit on dairy farms: milk income and feed cost. All producers were participants in the Dairy Herd Improvement (DHI) ROF program in Ontario, Canada during 2002. Nutrition, housing, health, and other management data were collected through a phone survey of herd managers. Herd milk production, milk component percentages, and somatic cell count data were obtained from the Ontario DHI database. The linear regression model accounting for significant variation in ROF with highest R2 (0.66) included standardized milk production, milk protein percentage, milk fat percentage, and use of monensin in lactating cow rations. A 1-kg increase in standardized milk production (kg/d per cow) or a 0.1 percentage unit increase in milk protein was associated with $0.35/d per cow or $0.26/d per cow increase, respectively, in the ROF of the dairy herd. However, a 0.1 percentage unit increase in milk fat was associated with a $0.10/d per cow decrease in ROF, probably because of a negative association of milk fat with milk yield. Use of monensin in lactating cow rations was associated with a $0.39/d per cow increase in ROF. In a separate model (R2 = 0.27) that examined management factors independent of production variables, herds using 3 times daily milking had a $1.25/d per cow higher ROF vs. herds using twice daily, whereas use of an Escherichia coli mastitis vaccine was associated with $0.59/d per cow higher ROF. Production-related variables accounted for more variation in the ROF index than management variables, and the latter, e.g., use of monensin, only marginally increased R2 of production-based regression models.