Pre-weaning management of calves on commercial dairy farms and its influence on calf welfare and mortality

Welfare and management of calves is of increasing interest and also influences performance of these animals in later life. The aim of this study was to assess management and environmental conditions under which pre-weaned dairy calves are reared on commercial Irish dairy farms. We included 47 spring-calving, pasture-based herds in this study. Herd and animal-specific data, such as mortality rate, age and breed, were gathered from all participants via the HerdPlus® database. Information pertaining to management practices was collected by conducting an interview with the principal calf rearer, while an assessment of calf housing facilities was conducted to identify conditions calves were reared in. The environmental assessment included measurements of space allowance per calf, as well as feeding equipment hygiene. To assess calf behaviour video observations were used, while accounting for the number of calves present in a group and the space available per calf. Faecal samples were also collected to determine the presence of enteric pathogens among calves. To compare calf space allowance, group size and presence of enteric pathogens early and late in the calving season each farm was visited twice. Calf mortality was not associated with either herd size, space allowance per calf or post-colostrum feeding practices. Higher calf mortality was identified among herds which reported experiencing an on-set of calf pneumonia during weeks 8 to 10 of the calving season. This study demonstrates that factors associated with calf welfare on commercial Irish dairy farms (e.g. space allowance, mortality rate) are independent of herd size. Some management practices however, such as methods used for treating health issues can affect rates of calf mortality experienced. Calf mortality, for example, was lower in herds which treated diarrhoea cases by administering electrolytes, while continuing to offer milk. Behavioural observations indicate that smaller group sizes could promote expression of positive behaviours, potentially resulting from an overall improvement in welfare. Space allowance per calf was not associated with observed behaviour frequencies. We also identified that similar rates of calf mortality are experienced across herds of different sizes.     

Insemination factors affecting the conception rate in seasonal calving Holstein-Friesian cows

Differences in conception rate to first service between artificial inseminations (AI) carried out by commercial AI operators (CAI) or do-it-yourself operators (DIY), between natural service (NAT) and AI, between different AI sires, and between fresh and frozen-thawed semen, on Irish commercial dairy farms, were studied using logistic regression. The study comprised 12,933 potential first inseminations from 77 spring-calving dairy herds. The data were recorded during 1999 and 2000. Amongst the total, 4,394 cows had repeated records across the two years. Adjustment variables included: herd, year, parity, calving period, calving to service interval, herd size, proportion of North American Holstein-Friesian genes, peak milk yield, semen fresh or frozen-thawed status, AI sire and a cow history variable to account for the correlation structure that may exist between performance records of cows present in both years of the study. Interactions of interest were tested but were non-significant. No significant association was observed between the category of AI operator and the likelihood of conception rate to first service (PREG1). The variation in PREG1 observed within the category of operator (CAI and DIY) was investigated using the Levene test for homogeneity of variance. There was no difference between the level of variation observed within CAI and DIY operators. There were significant differences in the likelihood of PREG1 between different AI sires. Amongst the 40 most commonly used AI sires, 3 sires had a lower likelihood of PREG1 (P < 0.05) when compared to the reference AI sire (sire with PREG1 similar to the mean of the group). There was a tendency for a reduced likelihood of PREG1 with the use of fresh semen compared to frozen-thawed semen (OR = 0.80, P = 0.067). Amongst the adjustment variables in the model, those significantly associated with the likelihood of PREG1 included the herd, calving period, calving to first service interval and peak milk yield. No significant difference in the likelihood of PREG1 was observed between AI and NAT.     

Economic analysis of the use of in vitro produced embryos transferred during heat stress under dairy herd constraints

The use of embryo transfer helps to improve reproductive performance during periods of heat stress. In vitro produced embryo transfer (IVP-ET) is more expensive than artificial insemination. We hypothesized that the value IVP-ET in seasonal herds depends on herd constraints, such as the maximum number of milking cows and the maximum number of calvings that can be accommodated throughout the year. Therefore, the objective of this study was to estimate how profitability in dairy herds exposed to summer heat stress is affected by the number of months in which IVP-ET is used, the use of IVP-ET in repeat-breeder cows, IVP-ET cost, and herd constraints. We built and used a nonlinear programming model of a dairy herd with young stock and cows with monthly Markov Chain transitions. The model varied the number of heifers calving in each calendar month to maximize herd profitability. We varied IVP-ET cost ($100 or $200), duration of the IVP-ET program (2 or 4 months), and the breeding number in which IVP-ET started (1st or 3rd). In total, 20 scenarios were simulated. Maximum profitability was obtained when IVP-ET was not used, regardless of herd constraints. The 16 scenarios in which IVP-ET was used showed increased seasonality in milk yield, numbers of milking cows, total cows, total calvings, and heifer calvings because the program tried to limit the number of IVP-ET breedings in the summer. The addition of the calving constraint increased the value of IVP-ET. The breakeven cost per IVP-ET ranged from −$6.79 to $24.38 compared with conventional semen cost of $20. In conclusion, the current market costs of IVP-ET did not warrant application with the objective to increase reproductive performance during heat stress. Herd constraints on the maximum allowable seasonality in the monthly number of milking cows and calvings affected the value of IVP-ET during heat stress.     

Questionnaire identifying management practices surrounding calving on spring-calving dairy farms and their associations with herd size and herd expansion

Healthy calves are fundamental to any profitable dairy enterprise. Research to-date, has focused on year-round calving systems which experience many different challenges compared to spring-calving systems. The objective of the present study was to determine the on-farm dry cow, calving, and colostrum management practices of spring-calving dairy production systems, and quantify their associations with herd size and herd expansion status (i.e. expanding or not expanding). Information on these management practices was available from a survey of 262 Irish spring-calving dairy farmers, representative of the Irish national population. Herd expansion in the 2 years before, and the year that the survey was conducted was not associated with any of the management practices investigated. Fifty-three percent of respondents had an average calving season length of 10 to14 weeks with 35% of herds having a longer calving season. Previous research in cattle has documented that both colostrum source and feeding management are associated with the transmission of infectious disease from cow to calf. In the present study 60% of respondents fed calves colostrum from their own dam; however, 66% of those respondents allowed the calf to suckle the dam, 23% of survey respondents fed calves pooled colostrum. Larger herds were more likely (P<0.01) to use pooled colostrum supplies, while smaller herds were more likely (P<0.05) to allow the calf to suckle the dam. The majority (86%) of respondents had stored supplies of colostrum; average-sized herds had the greatest likelihood of storing colostrum (P<0.05), compared to other herd sizes; larger sized herds had a lesser likelihood (P<0.05) of storing colostrum in a freezer, compared to other herd sizes. Although freezing colostrum was the most common method used to store colostrum (54% of respondents), 17% of respondents stored colostrum at room temperature, 29% of which stored it at room temperature for greater than 4 days. The results from the present study indicate that a particular focus needs to be placed on calving and colostrum management because this study has highlighted a number of areas which are below international standards, and may have repercussions for calf health. Furthermore, management practices on larger farms could be improved and, as these represent the future of dairy farming, a focus needs to be placed on them. Expanding herds are not a particular concern as herd expansion, independent of herd size, does not seem to be associated with calving and colostrum management practices on Irish spring-calving dairy herds.     

Associations between herd size, rate of expansion and production, breeding policy and reproduction in spring-calving dairy herds

Dairy herd size is expected to increase in many European countries, given the recent policy changes within the European Union. Managing more cows may have implications for herd performance in the post-quota era. The objective of this study was to characterise spring-calving herds according to size and rate of expansion, and to determine trends in breeding policy, reproduction and production performance, which will inform industry of the likely implications of herd expansion. Performance data from milk recording herds comprising 775,795 lactations from 2,555 herds for the years 2004 to 2008 inclusive were available from the Irish Cattle Breeding Federation. Herds were classified into Small (average of 37 cows), Medium (average of 54 cows) and Large (average of 87 cows) and separately into herds that were not expanding (Nil expansion), herds expanding on average by three cows per year (Slow expansion) and herds expanding on average by eight cows per year (Rapid expansion). There was no association between rate of expansion and 305-day fat and protein yield. However, 305-day milk yield decreased and milk protein and fat percentage increased with increasing rate of expansion. There were no associations between herd size and milk production except for protein and fat percentage, which increased with increasing herd size. Average parity number of the cows decreased as rate of expansion increased and tended to decrease as herd size increased. In rapidly expanding herds, cow numbers were increased by purchasing more cattle. The proportion of dairy sires relative to beef sires used in the breeding programme of expanding herds increased and there was more dairy crossbreeding, albeit at a low rate. Similarly, large herds were using more dairy sires and fewer beef sires. Expanding herds and large herds had superior reproductive performance relative to non-expanding and small herds. Animals in expanding herds calved for the first time at a younger age, had a shorter calving interval and were submitted for breeding by artificial insemination at a higher rate. The results give confidence to dairy producers likely to undergo significant expansion post-quota such that, despite managing more cows, production and reproductive performance need not decline. The management skills required to achieve these performance levels need investigation.     

Comparison of reproductive performance in Belgian dairy and beef cattle

A computerized program was written to collect, evaluate and compare reproductive performance data of 2004 beef (Belgian Blue breed) and 1649 dairy (Friesian Holstein and German Red) cattle in 35 Belgian herds (6 suckler beef herds, 9 milked beef herds and 20 dairy herds). Reproduction data were collected at monthly herd health visits. No difference in age at first calving was observed. Significant differences were observed among the 3 kinds of herds, and the best results were obtained in dairy herds for the calving interval, interval from calving to the first estrus, interval from calving to the first service and average number of days open. Concerning these parameters, first calvers had lower results than multiparous cows, mainly in suckler and milked beef herds. Significant differences were noted in the number of services per pregnancy. Heifers that had never calved presented the highest fertility. Primiparous beef cows had higher fertility than pluriparous cows. In dairy herds, pluriparous cows had higher fertility than primiparous cows. Estrus detection was better in milked beef herds than in suckled beef and dairy herds. Suckled beef herds had the lowest incidence of metritis and ovarian cysts of the three types of herds. Rates of abortion, overall culling and retained fetal membranes were similar in all the herds. The percentage of animals removed for infertility was highest in milked beef herds and lowest in dairy herds. Because 90% of the 1159 calvings recorded in the beef herds required a caesarean section, the reproductive performance of beef cattle represent results after caesarean section.     

Management of Calving in Norwegian Cubicle-Housed Dairy Herds

Sixty of the 65 dairy farms with cubicle houses in the Norwegian county of Oppland were included in a field study of the management of calving in 1990. The farmers recorded the location of the cow when giving birth, farmer presence and whether assistance was given during calving, occurrence of suckling, and time after birth when cow and calf were separated. Such data were recorded for a total of 1125 calvings. About 10% occurred on pasture, while 78% of the remaining calvings took place in the cubicle-equipped section. Thirteen percent calved in a calving pen, the remaining cows being tethered at the time of calving. Thirty-two percent of the calvings took place in houses lacking a calving pen altogether. Farmers were present during 41% of the calvings. Suckling most frequently occurred after pasture calvings, and was least frequent after calvings within the cubicle-equipped section of the cowhouse. Injuries to the calf caused by trampling or contact with fittings etc. were rare, and no more common in association with calving in the cubicle-equipped section than with calving taking place with the cow isolated from the rest of the herd. All calves were removed from their dams within 24 h after birth.     

Management practices as risk factors for the presence of bulk milk antibodies to Salmonella,Neospora caninum and Leptospira interrogans serovar hardjo in Irish dairy herds

A survey of management practices in 309 Irish dairy herds was used to identify risk factors for the presence of antibodies to Salmonella, Neospora caninum and Leptospira interrogans serovar hardjo in extensively managed unvaccinated dairy herds. A previous study documented a herd-level seroprevalence in bulk milk of 49%, 19% and 86% for Salmonella, Neospora caninum and leptospira interrogans serovar hardjo, respectively in the unvaccinated proportion of these 309 herds in 2009. Association analyses in the present study were carried out using multiple logistic regression models. Herds where cattle were purchased or introduced had a greater likelihood of being positive to leptospira interrogans serovar hardjo (P<0.01) and Salmonella (P<0.01). Larger herds had a greater likelihood of recording a positive bulk milk antibody result to leptospira interrogans serovar hardjo (P<0.05). Herds that practiced year round calving were more likely to be positive to Neospora caninum (P<0.05) compared to herds with a spring-calving season, with no difference in risk between herds that practiced split calving compared to herds that practiced spring calving. No association was found between presence of dogs on farms and prevalence of Neospora caninum possibly due to limited access of dogs to infected materials including afterbirths. The information from this study will assist in the design of suitable control programmes for the diseases under investigation in pasture-based livestock systems.     

Risk factors for post partum ovarian dysfunction in high producing dairy cows in Belgium: a field study

An epidemiological study of risk factors for postpartal ovarian disturbances was carried out on 334 high-yielding dairy cows in 6 well-managed Belgian herds. Ovarian activity was closely monitored using progesterone profiles, based on twice weekly RIA-analysis for progesterone in milk fat, starting at 10 d after calving and continuing until the confirmation of a new pregnancy. Attention was focused on abnormal cyclicity during the preservice, postpartum period; cows were divided into 6 different categories. Three of these categories (normal profile, delayed cyclicity, and prolonged luteal phase) were of major importance and were analyzed using a multiple variable logistic regression model. Season of calving (stable vs pasture, odds ratio (OR)=5.7), an extended length of the previous dry period (> 77 vs < or = 63 d, OR=2.9), problem calvings (OR=3.6), abnormal vaginal discharge (OR=4.5), health problems during the first month of lactation (clinical disease, OR=5.4; ketosis, OR=11.3), and clinical parameters illustrating the appearance of a severe negative energy balance significantly increased the risk for delayed cyclicity before service. Parity (> or = 4 vs 1, OR=2.5), problem calvings (OR=2.9), occurrence of puerperal disturbances (OR ranged from 3.5 to 11.0), health problems during the first month of lactation (OR=3.1), and an early resumption of ovarian cyclicity after calving (< 19 d vs > 32 d, OR=2.8) increased the risk for prolonged luteal cycles before service.     

Risk factors associated with detailed reproductive phenotypes in dairy and beef cows

The objective of this study was to identify detailed fertility traits in dairy and beef cattle from transrectal ultrasonography records and quantify the associated risk factors. Data were available on 148 947 ultrasound observations of the reproductive tract from 75 949 cows in 843 Irish dairy and beef herds between March 2008 and October 2012. Traits generated included (1) cycling at time of examination, (2) cystic structures, (3) early ovulation, (4) embryo death and (5) uterine score; the latter was measured on a scale of 1 (good) to 4 (poor) characterising the tone of the uterine wall and fluid present in the uterus. After editing, 72 773 records from 44 415 dairy and beef cows in 643 herds remained. Factors associated with the logit of the probability of a positive outcome for each of the binary fertility traits were determined using generalised estimating equations; linear mixed model analysis was used for the analysis of uterine score. The prevalence of cycling, cystic structures, early ovulation and embryo death was 84.75%, 3.87%, 7.47% and 3.84%, respectively. The occurrence of the uterine heath score of 1, 2, 3 and 4 was 70.63%, 19.75%, 8.36% and 1.26%, respectively. Cows in beef herds had a 0.51 odds (95% CI=0.41 to 0.63, P<0.001) of cycling at the time of examination compared with cows in dairy herds; stage of lactation at the time of examination was the same in both herd types. Furthermore, cows in dairy herds had an inferior uterine score (indicating poorer tone and a greater quantity of uterine fluid present) compared with cows in beef herds. The likelihood of cycling at the time of examination increased with parity and stage of lactation, but was reduced in cows that had experienced dystocia in the previous calving. The presence of cystic structures on the ovaries increased with parity and stage of lactation. The likelihood of embryo/foetal death increased with parity and stage of lactation. Dystocia was not associated with the presence of cystic structures or embryo death. Uterine score improved with parity and stage of lactation, while cows that experienced dystocia in the previous calving had an inferior uterine score. Heterosis was the only factor associated with increased likelihood of early ovulation. The fertility traits identified, and the associated risk factors, provide useful information on the reproductive status of dairy and beef cows.     

Relationship between dairy cow genetic merit and profit on commercial spring calving dairy farms

Because not all animal factors influencing profitability can be included in total merit breeding indices for profitability, the association between animal total merit index and true profitability, taking cognisance of all factors associated with costs and revenues, is generally not known. One method to estimate such associations is at the herd level, associating herd average genetic merit with herd profitability. The objective of this study was to primarily relate herd average genetic merit for a range of traits, including the Irish total merit index, with indicators of performance, including profitability, using correlation and multiple regression analyses. Physical, genetic and financial performance data from 1131 Irish seasonal calving pasture-based dairy farms were available following edits; data on some herds were available for more than 1 year of the 3-year study period (2007 to 2009). Herd average economic breeding index (EBI) was associated with reduced herd average phenotypic milk yield but with greater milk composition, resulting in higher milk prices. Moderate positive correlations (0.26 to 0.61) existed between genetic merit for an individual trait and average herd performance for that trait (e.g. genetic merit for milk yield and average per cow milk yield). Following adjustment for year, stocking rate, herd size and quantity of purchased feed in the multiple regression analysis, average herd EBI was positively and linearly associated with net margin per cow and per litre as well as gross revenue output per cow and per litre. The change in net margin per cow per unit change in the total merit index was €1.94 (s.e. = 0.42), which was not different from the expectation of €2. This study, based on a large data set of commercial herds with accurate information on profitability and genetic merit, confirms that, after accounting for confounding factors, the change in herd profitability per unit change in herd genetic merit for the total merit index is within expectations.     

The effect of feeding and management practices on calving rate in dairy herds

The objective of this study was to examine the effects of nutrition and management practices on reproductive performance in 31 Irish dairy herds participating in the Moorepark Dairy Management Information System (DairyMIS) during the period 1991-1998. Fifty variables relating to herd reproductive indices, calving events, stocking rate, disease, concentrate feeding, fertiliser usage, milk production and economic performance were studied using factor analysis. A factor analysis, followed by varimax rotation, identified 13 factors, which accounted for 83% of the total variance of the original variables. A regression model was used to predict calving rate from the orthogonal factor scores identified by factor analysis. Calving rate was defined as the proportion of services, for which an outcome was known, which resulted in a subsequent calving. Year, farm code and factor 3 (labelled herd size) together accounted for 40% of the observed variation in calving rate. The factor scores for factor 3 (herd size) were plotted against calving rate and because the plot was not linear, it was decided that dividing the factor scores into quartiles would produce a better fitting model. The factor scores for herd size were sorted and assigned to four equal categories (n = 47 per category), from lowest to highest. The ranges in herd size according to category were as follows: category 1 (34-96), category 2 (47-103), category 3 (66-152) and category 4 (108-359). The calving rate (%), (+/-S.E.) was 67.0 +/- 2.5 for category 1, 61.8 +/- 1.8 for category 2, 56.9 +/- 1.5 for category 3 and 53.2 +/- 2.85 for category 4. Using pair-wise comparisons, calving rates differed significantly (P < 0.05) between all categories except between categories 3 and 4 (P > 0.05). Herd-level milk production was not associated with calving rate indicating that good management may overcome any adverse effects of high milk production on reproductive performance. Larger herds, in combination with other associated herd characteristics, are likely to have poorer calving rates than medium or small herds.     

The fertility of autumn calving suckler beef cows is increased by the addition of prostaglandin to progesterone and eCG estrus synchronization treatment

The objective of this study was to determine the efficacy of PGF2 alpha treatment on pregnancy and calving rates in autumn-calving suckler beef cows synchronized with progesterone and eCG. The population studied consisted of 124 Charolais and 130 Limousin cows in 13 and 12 beef herds, respectively. In each herd, pairs of cows were formed according to parity, body condition score and calving difficulty. Group 1 received a progesterone releasing intravaginal device (PRID) for 12 d with a capsule containing 10 mg estradiol benzoate at implant insertion and 500 IU eCG at PRID removal (Day 0). Group 2 received the same treatment plus 25 mg i.m. dinoprost at Day -2. Each cow was artificially inseminated 56 h after PRID removal (Day 3). Plasma progesterone concentrations were measured to determine cyclicity prior to treatment in samples take on Days -22 and -12, to confirm the occurrence of ovulation (Day 13) and to determine the early pregnancy rate (Day 26). Serum pregnancy-specific protein B (PSPB) concentrations were determined to assess pregnancy rate at Day 39. The effects of variation factors on pregnancy and calving rates after treatment were studied using logistic mixed models and a Cox model, respectively. There were no significant differences between groups or breeds for the rate of cyclicity before treatment nor for ovulation rate (means, 74.1 and 95.7%, respectively). Cyclicity was, however, influenced by individual factors such as body condition score (OR = 3.36, P = 0.001), parity (OR = 5.4, P = 0.001) and herd factors such as stocking rate (OR = 5.62, P = 0.001). The use of a prostaglandin injection increased pregnancy rate at Day 26 (71.7 vs 56.7%, P = 0.01) and at 39 d (67.7 vs 54.3%, P = 0.02) and the calving rate at induced estrus (64.5 vs 48.5%, P = 0.01). We observed 9 twin calvings (5.6%) which occurred in cyclic cows only before treatment. Cows in Group 2 had a 1.5 greater chance of calving before 300 d following the first AI than cows in Group 1 (P = 0.03). In conclusion, the addition of PGF2 alpha injection, 48 h before PRID removal, increased reproductive efficiency in autumn-calving Charolais and Limousin suckler beef cows compared to a classical estrus synchronization treatment using a PRID + eCG.     

The use of crossbreeding with beef bulls in dairy herds: effects on calving difficulty and gestation length

This study was designed to analyse the evolution in the use of beef bull semen for dairy cattle insemination and, mainly, to assess calving difficulty, gestation length and proportion of stillbirths after breeding pure Holsteins or crossbreeding. Data were collected during 2004 to 2011 for 552 571 Holstein calvings (457 070 Holstein × Holstein, 43 384 Holstein × Limousine, 32 174 Holstein × Belgian Blue and 19 943 Holstein × Galician Blonde). The highest calving difficulty, compared with pure Holsteins was for crosses with Belgian Blue followed by Limousine and Galician Blonde. The Holstein × Limousine and Holstein × Galician Blonde crossbred calves had significantly longer gestation lengths than Holstein × Holstein and Holstein × Belgian Blue calves. Between the latter two, pure Holstein had the shortest gestation length. Calving difficulty and gestation length decreased as the age of the dam advanced. The most difficult calvings were observed in twin calvings, followed by the calvings of male calves and female calves. The gestations leading to the birth of male calves were longer than those leading to female calves and twin calves. Stillbirths were not related to the breed used for mating. Through examining these parameters, sire breed should be considered when selecting a beef breed for the insemination of milk-producing dams.     

Twinning in dairy cattle: A study of risk factors and effects

Twin calvings on Dutch dairy farms were studied using data collected through a routine herd health and production management program. Over a period of 6.5 yr, 381 twin calvings (762 calves) of a total of 11,951 calvings were recorded on 33 farms. The 381 twin calvings were compared with a referent group of 1,536 calvings that was randomly selected from the orginal 11,951 calvings. Risk factors for twin calvings were parity, season, herd and previous twinning. High cumulative milk production was associated with cows conceiving twins. Treatment for infertility in the preceding lactation was an equivocal risk factor. Twin calvings increased the risk of abortion, retained placenta, fertility-related treatment, as well as the number of days open and the number of inseminations per conception. Although twin calvings resulted in more calves born per dam, the number of available replacement heifers did not increase. After twin calving, cows produced slightly less milk and were culled more often than single calving cows. To adapt appropriate management practices for cows carrying twins, an early and reliable method for detecting twin pregnancies is needed.     

Mortality in Holstein-Friesian calves and replacement heifers, in relation to body weight and IGF-I concentration, on 19 farms in England

The incidence of mortality and culling in Holstein-Friesian heifers from birth through first calving was determined on 19 dairy farms selected from across southern England. The outcome of 1097 calvings was determined. Size (BW, heart girth, crown-rump length and height at withers) and insulin-like growth factor-I concentration of live heifer calves were measured at a mean age of 26 ± 0.7 days (n = 506). Associations between the heifer-level variables and mortality were determined using clustered binary logistic regression. Perinatal mortality (stillbirths and mortality within the first 24 h of birth) of male and female calves was 7.9%. This figure was significantly higher in cases where calving assistance was required (19.1% v. 5.6%, P < 0.001) and in twin births (18.5% v. 7.0%, P < 0.05), and was lower in pluriparous v. primiparous dams (5.6% v. 12.1%, P < 0.01). On average, 6.8% of heifers died or were culled between 1 day and 6 months of age. Low BW at 1 month was associated with reduced subsequent survival up to 6 months. Between 6 months and first calving, a further 7.7% of heifers either died (42%) or were culled (58%); accidents and infectious disease accounted for the majority of calf deaths between 6 and 15 months, whereas infertility (16/450 animals served, 3.5%) was the main reason for culling following the start of the first breeding period. In total, 11 heifers (2.2%) were culled as freemartins; eight at birth and three around service. Overall, 14.5% of liveborn potential replacement heifers died or were culled before first calving.     

Reproductive performance in Ohio dairy herds in the 1990s

The objective of this study was to evaluate trends in reproductive performance in Ohio dairy herds during the 1990s. Stringent criteria for herd inclusion were applied to DHI records to ensure high quality and reliability of the data. The final data set contained 44,425 monthly herd summary records from 1772 herds from years 1992, 1994, 1996 and 1998. Outcomes of interest were calving interval length, calving-to-conception interval, days to first breeding, services per conception and first service conception rate. PROC MIXED in SAS (version 8.1) was used and the monthly records were treated as repeated measures nested within years and herds. First-order autoregressive covariance structure was used to model the covariance between the repeated measures within herds. The data were analyzed for the entire herd as well as for the first lactation cows separately. During the 1990s reproductive performance declined in Ohio dairy herds. Herd average calving interval lengthened from 13.6 to 14.1 months and calving-to-conception interval increased from 136 to 150 days between 1992 and 1998, respectively. Days to first service and number of services increased while first service conception rate declined on a herd level. The reproductive performance of first lactation cows, however, remained constant during this same period. Overall herd reproductive performance was associated with herd size and fat-corrected rolling herd average milk production (FCM). As milk yield increased, first service conception rate decreased and services per conception increased. Larger herds had lower first service conception rate and needed more services per conception, but they started breeding their cows earlier resulting in a slightly shorter calving interval and calving-to-conception interval compared to smaller herds.     

Farm characteristics related to on-farm cow mortality in dairy herds: a questionnaire study

Dairy cow mortality is an important animal welfare issue that also causes financial losses. The objective of this study was to identify farm characteristics and herd management practices associated with high on-farm cow mortality in Swedish dairy herds. A postal questionnaire was sent to farmers that had either high or low mortality rates for 3 consecutive years. The questionnaire consisted of five sections: ‘About the farm’, ‘Milking and housing’, ‘Feeding’, ‘Routines’ and ‘Lame and sick cows’. A total of 145 questionnaires were returned (response rate=33%). Ten of the 77 characteristics investigated met the inclusion criteria for multivariable analysis. The final logistic regression model included: herd size, breed, use of natural service bull, bedding improvement frequency and pasture system. Herds with Swedish Holstein as the predominant breed (odds ratio (OR) 22.9, 95% confidence interval (CI) 5.2 to 101.8) or with mixed breeds (OR 5.5, 95% CI 1.7 to 17.5) had a greater risk of being high mortality herds than herds that were predominantly Swedish Red (OR 1). Herds larger than 100 cows (OR 19.6, 95% CI 3.5 to 110.4) and herds with 50 to 99 cows (OR 13.8, 95% CI 3.2 to 60.6) had greater risk of mortality than herds numbering 35 to 50 cows (OR 1). Being a high mortality herd was also associated with having cows on exercise lots during the summer season (OR 3.6, 95% CI 1.3 to 9.9) compared with on pasture. A missing answer on the question of bedding improvement frequency was associated with high mortality herds. Overall, this study suggests that characteristics that are related to intensification of the dairy industry are also associated with high on-farm mortality of dairy cows.     

Seroprevalence of Neospora caninum infection in dairy and beef cattle in Spain

In recent years, neosporosis has been identified as a major cause of abortion in dairy and beef cattle. Although the disease has been described worldwide, there is a Jack of information concerning the prevalence of this infection in different cattle production systems. The aim of this study was to investigate the seroprevalence of Neospora caninum infection in a representative area of beef and dairy cattle production in Spain. A cross-sectional study was undertaken in which herds constituted the initial sampling unit and two strata (dairy and beef herds) were considered. Using a 95% level of confidence and setting 5% (beef) and 5.4% (dairy) error limits, 216 beef and 143 dairy herds were randomly selected and sampled. Nine animals (> 1 year old) were randomly sampled in each herd to detect the presence of the infection. A herd was considered infected when at least one animal was seropositive. In total, serum samples from 1121 dairy and 1712 beef animals were collected and tested for specific anti-N. caninum IgG using an ELISA. Specific antibodies were detected in 55.1% (119/216) beef and 83.2% (119/143) dairy herds. Individual prevalences obtained were 17.9% (306/1712) for beef and 35.9% (402/1121) for dairy animals. Presence of N. caninum infection was higher in dairy than in beef herds and the association between infection and the cattle production system (dairy or beef) was statistically significant [(chi2)Y= 29.21, P < 0.001, OR = 4.04 (2.35-6.99)]. Herd size of dairy cattle did not appear to be associated with N. caninum infection. On the contrary, infection was associated with herd size in beef cattle (chi2 = 12.79, P < 0.01). Finally, no association was found between replacement or pasture management and infection in beef herds.     

Effect of cow replacement strategy on cow and calf performance in the beef herd

Two contrasting replacement strategies are used by Irish beef farmers to select replacement females – animals sourced from within the suckler beef herd and sourced from the dairy herd. The objective of this study was to investigate the effect of replacement strategy (i.e. beef v. beef×dairy (BDX)) on cow and calf performance using data from the national beef database across a range of beef and dairy breeds. The association between replacement strategy and calving difficulty score, calving interval, weaning weight, weaning price and all carcass traits was investigated using a mixed model. The effect of replacement strategy on cow survival, calving dystocia and calf perinatal mortality was quantified using logistic regression. Beef cows were older (10.92 days; P<0.001) at their first calving, but were 1.15 times (P<0.01) more likely to survive to a subsequent lactation compared with BDX cows. Calving interval was 1.53 days shorter (P<0.001) for BDX compared with beef cows. Greater calving difficulty and calving dystocia was associated with beef cows (P<0.001) relative to BDX. However, BDX were 1.36 times (P<0.001) more likely to have a dead calf at birth relative to beef cows. Calves weaned from BDX were heavier (18.49 kg; P<0.001) at weaning, reached slaughter 12.8 days earlier (P<0.001), had 7.99 kg heavier carcass (P<0.001) and a greater fat score (P<0.001) compared with the progeny of beef cows. Beef cow progeny had a superior conformation score (0.5; P<0.001) and achieved a greater price per kilogram (P<0.001) compared with progeny from BDX. Beef cull cows had a heavier carcass (5.58 kg), superior carcass conformation, greater carcass price per kilogram and greater overall carcass value (P<0.001) than BDX. Results from this study show that replacement strategy is of fundamental importance depending on the type of system implemented by farmers and consideration must be given to the traits of importance within the context of the individual production system.