The Effect of a Direct Fed Microbial on Liveweight and Milk Production in Dairy Cattle

This longitudinal study aimed to quantify the effects of dietary supplementation of a direct-fed microbial (DFM) consisting of three lactobacilli isolates on milk yield, milk fat and protein yields, somatic cell count (SCC), and liveweight in a single dairy herd in Australia. A total of 150 dairy cows were randomly selected based on parity and days in milk and divided into two groups: control (n = 75) and DFM treatment (n = 75). Throughout the study, the two groups of cows were housed separately in a dry lot yard, and each group had their own feeding area. For the DFM treatment group, selected cows in mid-lactation were supplemented with 10 mL/cow/day of the DFM via top dressing of the feed for the remainder of the lactation and through the dry period, extending into subsequent lactation. The control group had no supplementation. The milk yield and liveweight were recorded daily. Milk samples were collected every two months for milk component analysis (fat, protein, and somatic cell count [SCC]). The DFM-treated cows gained more liveweight across the study (19.40 kg, 95% CI 0.44 kg; 38.30 kg, p = 0.05) compared to the control cows. In the second production year, the DFM-treated cows mobilized more liveweight (-6.06 kg, 95% CI -10.49 kg; -1.61 kg, p = 0.01) and produced more milk (0.39 L/d 95% CI 0.10; 0.89, p = 0.05). Over a full lactation, DFM cows yielded at least 258 L (95% CI 252 L; 265 L) more milk than controls. No significant differences were found in fat and protein yield or SCC. This study suggests that consistent and ongoing supplementation with a Lacticaseibacillus- and Lentilactobacillus-based DFM could have a positive effect on milk production, but further research is needed to understand the underlying mechanism.

Animal- and herd-level factors associated with onset of puberty in grazing dairy heifers

AIMS

To explore animal- and herd-level risk factors influencing age at puberty in predominantly Holstein-Friesian dairy heifers managed in seasonal, pasture-based systems.

METHODS

Heifers born in spring 2018 (n = 5,010) from 54 commercial dairy herds in New Zealand were visited on three occasions when the mean heifer age, within herd, was 10 (visit 1; V1), 11 (V2) and 12 (V3) months old. Blood samples were collected on each visit and liveweight, stature and anogenital distance (AGD) were measured at V2. Heifers were defined as having reached puberty at the first visit where blood progesterone was elevated (≥ 1 ng/mL). Animal-level response variables included pubertal status by V1, V2 and V3, and age at puberty (or age at V3 plus 31 days for those that had not attained puberty by V3). To explore herd-level management factors, farmers answered a questionnaire relating to animal location, land type, health, feeding, and management between weaning and mating. A partial least squares regression was undertaken to identify herd-level factors associated with the greatest influence on puberty rate within herd.

RESULTS

The mean age at puberty was 352 (SD 34.9) days. Heavier animals at a greater proportion of expected mature liveweight based on their breeding value for liveweight, or animals with a higher breed proportion of Jersey and lower breed proportion of Holstein, were associated with earlier puberty. Herd puberty rates varied widely among enrolled herds, and averaged 20%, 39% and 56% by V1, V2 and V3, respectively. Liveweight, followed by breed and land type, had the greatest influence on the herd puberty rate. Heifer herds with a greater mean liveweight (absolute and proportion of expected mature weight) or greater Jersey proportion had more animals that reached puberty at any visit, whereas herds located on steep land or with greater Holstein breed proportions had lower puberty rates. Management-related factors such as vaccinations, provision of feed supplements, and weighing frequency were also herd-level risk factors of puberty but had less influence.

CONCLUSIONS AND CLINICAL RELEVANCE

This study highlights the importance of having well-grown heifers for increasing the chances of earlier puberty onset and the effect of breed and youngstock management to achieve growth targets. These outcomes have important implications for the optimal management of heifers to achieve puberty before their maiden breeding and for the timing of measurements to potentially incorporate a puberty trait in genetic evaluations.

Animal safety of a tall fescue endophyte (Epichloë sp.) in a perennial ryegrass (Lolium perenne) host

AIMS

To assess animal health and production in sheep grazing perennial ryegrass (Lolium perenne) infected with a tall fescue endophyte (Epichloë sp.).

METHODS

Three replicates of pure perennial ryegrass pastures infected with AR501 tall fescue endophyte (AR501 HE), AR1, AR37 or standard endophyte (STD) (all >85% infection) and a low endophyte control (AR501 LE) were grazed by 10 lambs for 7 weeks during late summer/early autumn, 2017. AR501 HE and AR501 LE were in the same tetraploid cultivar and the remaining treatments were in the same diploid cultivar. Lambs were weighed on Days 0, 19, 37 and 48 and assessed for ryegrass staggers on a 0-4 tremor scale nine times from Day 13. On Days 14 and 20, rectal temperatures and respiration rates were measured in lambs grazing AR501 HE, AR501 LE and STD under heat load. Pasture samples from each treatment were taken regularly (8 times) for analysis of known endophyte secondary metabolites.

RESULTS

Peak mean ryegrass staggers scores for lambs grazing STD and AR37 treatments were 3.9 and 2.7, respectively, indicating environmental conditions were conducive to toxicity. Lambs grazing AR501 HE showed no ryegrass staggers at any date. The liveweight of STD lambs was up to 6.6 kg less than some or all other treatments on Days 19, 34 and 48 but there was no evidence of a difference between the liveweight of AR501 HE lambs and AR501 LE, AR37 or AR1 lambs on any date. Rectal temperatures and respiration rates of STD lambs were higher than AR501 HE lambs by 0.2°C and 26 breaths/minute, respectively. Apart from lower rectal temperature of AR501 HE lambs on Day 14, there was no evidence of differences between the AR501 HE and AR501 LE lambs.N-Formylloline was the only loline present in AR501 HE herbage (350-860 mg/kg). Peramine in AR501 HE herbage (42-77 mg/kg) was greater than that in STD and AR1 herbage on five and seven of the eight sampling dates, respectively.

CONCLUSION

Lambs grazing AR501 HE showed no ryegrass staggers, exacerbated heat stress or suppressed liveweight gain compared with lambs grazing AR501 LE in a season when endophyte-induced toxicity was evident in STD and AR37 pastures. This suggests AR501 tall fescue endophyte does not produce toxic concentrations of secondary metabolites.

CLINICAL RELEVANCE

This study suggests that there are no secondary metabolites produced by the tall fescue AR501 endophyte-perennial ryegrass association which affect animal health or production.

Predicting ewe body condition score using adjusted liveweight for conceptus and fleece weight, height at withers, and previous body condition score record

The relationship between ewe body condition score (BCS) and liveweight (LW) has been exploited previously to predict the former from LW, LW-change, and previous BCS records. It was hypothesized that if fleece weight and conceptus-free liveweight and LW-change, and in addition, height at withers were used, the accuracy of current approaches to predicting BCS would be enhanced. Ewes born in 2017 (n = 429) were followed from 8 mo to approximately 42 mo of age in New Zealand. Individual ewe data were collected on LW and BCS at different stages of the annual production cycle (i.e., prebreeding, at pregnancy diagnosis, prelambing, and weaning). Additionally, individual lambing dates, ewe fleece weight, and height at withers data were collected. Linear regression models were fitted to predict current BCS at each ewe age and stage of the annual production cycle using two LW-based models, namely, unadjusted for conceptus weight and fleece weight (LW alone1) and adjusted (LW alone2) models. Furthermore, another two models based on a combination of LW, LW-change, previous BCS, and height at withers (combined models), namely, unadjusted (combined1) and adjusted for conceptus and fleece weight (combined2), were fitted. Combined models gave more accurate (with lower root mean square error: RMSE) BCS predictions than models based on LW records alone. However, applying adjusted models did not improve BCS prediction accuracy (or reduce RMSE) or improve model goodness of fit (R²) (P > 0.05). Furthermore, in all models, both LW-alone and combined models, a great proportion of variability in BCS, could not be accounted for (0.25 ≥ R² ≥ 0.83) and there was substantial prediction error (0.33 BCS ≥ RMSE ≥ 0.49 BCS) across age groups and stages of the annual production cycle and over time (years). Therefore, using additional ewe data which allowed for the correction of LW for fleece and conceptus weight and using height at withers as an additional predictor did not improve model accuracy. In fact, the findings suggest that adjusting LW data for conceptus and fleece weight offer no additional value to the BCS prediction models based on LW. Therefore, additional research to identify alternative methodologies to account for individual animal variability is still needed.

Estimated Breeding Values of Beef Sires Can Predict Performance of Beef-Cross-Dairy Progeny

On average, half of the animal's estimated breeding value (EBV) is passed on to their progeny. However, it is not known how the performance of beef-cross-dairy cattle relates to the EBV of their beef sire. Such information is required to determine the genetic potential of beef sires selected based on existing EBV to be used on dairy cows in New Zealand. This study evaluated the relationship between the EBV of 30 Angus and 34 Hereford sires and the performance of their progeny for birth, growth, and carcass traits, via progeny testing of 975 beef-cross-dairy offspring born to dairy cows and grown on hill country pasture. Overall, BREEDPLAN EBV did predict progeny performance of the beef-cross-dairy cattle from this study. Gestation length and birthweight increased with increasing sire EBV (mean 0.37-0.62days and 0.52-0.64kg, respectively, p<0.05). Age at weaning decreased with increasing sire EBV for liveweight at 200days (0.17-0.21days per extra kilo of sire EBV, p<0.05) but sire EBV for liveweight at 200days had no effect on the liveweight of the progeny at 200days for either breed (p>0.05). Liveweight increased with sire EBV for liveweight at 400, 600, and 800days, by a similar amount for both breeds (between 0.23 and 0.42kg increase in progeny liveweight per extra kilo of sire EBV, p<0.05). The relationships were more inconsistent for carcass traits. For Hereford, carcass weight and eye muscle area increased with increasing sire EBV (0.27kg and 0.70cm², respectively, p<0.05). For Angus, marble score increased by 0.10 with 1% extra in sire EBV for intramuscular fat (p<0.05). Rib fat depth tended to increase with sire EBV for both breeds (p<0.1). EBV derived from beef-breed data work in dairy-beef systems but maybe slightly less than the expected 0.5units of performance per unit of EBV. New Zealand farmers should consider BREEDPLAN EBV when selecting sires to mate dairy cows or when buying beef-cross-dairy calves for beef production, to ensure the resulting calves are born safely and on time and then grow well to produce carcasses of suitable meat and fat composition.

Growth Performance and Plasma Metabolites of Grazing Beef Cattle Backgrounded on Buffel or Buffel-Desmanthus Mixed Pastures

Simple Summary

Pasture quality and digestibility decline during the dry season resulting in weight loss or marginal weight gains of grazing cattle in the seasonally dry subtropics of northern Australia. Oversowing grass with legume pastures has shown potential to improve pasture quality and cattle weight gain. This study aimed to evaluate the change in steers’ weight gain and plasma metabolites in response to grazing buffel grass pastures oversown with Desmanthus spp. (Desmanthus), a tropical legume adapted to cracking clay soils, compared to buffel-grass-only pastures. Results showed that Desmanthus at a low botanical composition had no effect on weight gain and plasma metabolites, although pasture yield and stocking rate were 443 kg/ha and 9.5% higher, respectively. Since the productivity of grazing systems depends on cattle annual weight gain and stocking rate, the practical implication of this study is that Desmanthus may improve the profitability of beef production in the dry tropics of northern Australia by improving pasture-carrying capacity with no adverse effect on cattle health status and growth performance.

Abstract

Dietary crude protein and dry matter digestibility are among the major factors limiting feed intake and weight gain of cattle grazing native and improved pastures in the subtropics of Northern Australia during the dry season. Incorporating a suitable legume into grasses improves pasture quality and cattle weight gain, but only a limited number of legume pastures can establish and persist in cracking clay soils. This study aimed to evaluate the effect of Desmanthus inclusion in buffel grass (Cenchrus ciliaris) pastures on the plasma metabolite profile and growth performance of grazing beef cattle during the dry season. We hypothesised that backgrounding steers on buffel grass-Desmanthus mixed pastures would elicit significant changes in plasma glucose, bilirubin, creatinine, non-esterified fatty acids and β-hydroxybutyrate, resulting in higher liveweight gains than in steers on buffel grass only pastures. Four hundred tropical composite steers were assigned to buffel grass only (n = 200) or buffel grass oversown with Desmanthus (11.5% initial sward dry matter) pastures (n = 200) and grazed for 147 days during the dry season. Desmanthus accounted for 6.2% sward dry matter at the end of grazing period. Plasma metabolites results showed that changes in β-hydroxybutyrate, creatinine, bilirubin, glucose and non-esterified fatty acids were within the expected normal range for all the steers, indicating that with or without Desmanthus inclusion in the diet of grazing steers, animal health status was not compromised. It was also evident that Desmanthus inclusion in buffel grass pastures had no impact on the plasma metabolite profile, liveweight and daily weight gain of grazing steers. Therefore, our tested hypothesis of higher changes in plasma metabolite profile and higher liveweight gains due to backgrounding on low-level buffel grass-Desmanthus mixed pastures does not hold.

Calf Birth Weight Predicted Remotely Using Automated in-Paddock Weighing Technology

The present study aimed to develop predictive models of calf birth weight (CBW) from liveweight (LW) data collected remotely and individually using an automated in-paddock walk-over-weighing scale (WOW). Twenty-eight multiparous Charolais cows were mated with two Brahman bulls. The WOW was installed at the only watering point to capture LW over five months. Calf birth date and weight were manually recorded, and the liveweight change experienced by a dam at calving (ΔLWC) was calculated as pre-LW minus post-LW calving. Cow non-foetal weight loss at calving (NFW) was calculated as ΔLWC minus CBW. Pearson's correlational analysis and simple linear regressions were used to identify associations between all variables measured. No correlations were found between ΔLWC and pre-LW (p = 0.52), or post-LW (p = 0.14). However, positive associations were observed between ΔLWC and CBW (p < 0.001, R2 = 0.56) and NFW (p < 0.001, R2 = 0.90). Thus, the results suggest that 56% of the variation in ΔLWC is attributed to the calf weight, and consequently could be used as an indicator of CBW. Remote, in-paddock weighing systems have the potential to provide timely and accurate LW data of breeding cows to improve calving management and productivity.

The Effect of Age, Stage of the Annual Production Cycle and Pregnancy-Rank on the Relationship between Liveweight and Body Condition Score in Extensively Managed Romney Ewes

Simple Summary

Liveweight and body condition score (BCS)) are related, indicating that it may be possible to predict one from the other. The magnitude of this relationship can be altered by animal and environmental factors. The aim of the present study was to determine the nature of the association between liveweight and BCS over time, and the effect of the interaction between the stage of the annual cycle and the age of the ewe, using individual animal records. The association between liveweight and BCS was found to be linear and was affected by the interaction between ewe age, stage of the annual cycle and pregnancy-rank of the ewe. The results highlight the substantial contribution of BCS to the differences in liveweight of the ewe. The findings suggest that when predicting BCS from the liveweight, consideration of these factors is required, and different prediction equations are needed.

Abstract

This study determined the nature of the relationship between liveweight and body condition score (BCS) and assessed the influence of the stage of the annual cycle and pregnancy-rank on the relationship between liveweight and BCS in Romney ewes. Data were collected from the same ewes at different ages (8–18, 19–30, 31–42, 43–54, 55–66 and ≥67 months), stages of the annual cycle (pre-breeding, at pregnancy diagnosis, pre-lambing and weaning) and pregnancy-rank (non-pregnant, single or twin). Linear regression was determined as being sufficient to accurately describe the relationship between liveweight and BCS. Across all data, a one-unit change in BCS was associated with 6.2 ± 0.05 kg liveweight, however, this differed by stage of the cycle, pregnancy-rank and ewe age (p <0.05). The average liveweight per unit change in body condition score increased with the age of the ewe and was greatest at weaning and lowest pre-lambing. Among pregnancy-ranks, the average liveweight per unit change was also greater during pregnancy diagnosis than pre-lambing and was greatest among single and lowest in non-pregnant ewes. The results support the hypothesis that the relationship between liveweight and BCS is affected by the interaction between stage of the annual cycle, pregnancy-rank and ewe age.

Linear body measurements and productivity of subtropical Holstein-Friesian dairy calves

OBJECTIVE

The study aimed to describe growth parameters and to quantify the association between linear body measurements as predictors of liveweight (LW) of Holstein-Friesian (HF), and HF crossbred dairy calves in Queensland. A secondary objective was to quantify the effect of disease events on LW change.

STUDY DESIGN

Longitudinal study.

METHODS

Fortnightly LW, hip height (HH), hip width (HW) and heart girth (HG) measurements were recorded from 16 male and 28 female HF calves from birth until weaning. The association between linear body measurement and the effect of a disease event on LW change were explored using linear mixed-effects modelling with random intercepts and random slopes.

RESULTS

HG was the best body measure used individually as a predictor of calf LW (R2 = 82%; P < 0.001), while the combined use of HG, HW and HH was the most accurate predictor of calf LW between birth and weaning (R2 = 90%; P < 0.001). HW, average feed intake and total feed intake were significantly affected by disease events (P < 0.05). On average, total average LW loss associated with a single pneumonia event was estimated at 14.6 kg (95% CI = 10.5 to 18.7 kg; P < 0.05).

CONCLUSIONS

Calves of this study performed at a level consistent with the previously published reports. Growth performance was significantly compromised by pneumonia. HW was found to be the least predictive individual measure, and the combined use of HH, HW and HG had the most accurate prediction of calf liveweight from birth to weaning.

Application of In-Paddock Technologies to Monitor Individual Self-Fed Supplement Intake and Liveweight in Beef Cattle

Simple Summary

Individual, daily and simultaneous measures of key variables to manage cattle have been traditionally difficult to achieve in grazing animals. However, nowadays, this could be achieved using technologies which are placed ‘in paddock’ such as automated weighing scales to measure liveweight (LW) and electronic feeders (EF) to measure supplement intake. We used both technologies to study the interplay between the intake of a self-fed supplement (molasses-lick blocks, MLB), growth, and feeding behavior of individual animals fed a sequence of different feed types. We identified a large individual variability in MLB intake with some animals consuming supplement regularly while others not consuming supplement at all. Regular consumers tended to grow more rapidly. Additionally, our results indicate that animals’ MLB intake can be predicted using the number of visits to the EF and their duration. In-paddock technologies could aid to quantify key factors, such as individual variability of supplement intake and LW, that would otherwise remain undetected.

Abstract

The aim of this study was to assess the ability of in-paddock technologies to capture individual variability of self-fed supplement intake (molasses-lick blocks, MLB), feeding behavior, and liveweight (LW) in grazing beef cattle. An electronic feeder (EF) and in-paddock walk-over-weighing system (WOW) were installed to measure, daily and simultaneously, individual MLB intake and LW. Cattle grazed (pastures and oat crops) and were fed (lucerne and oaten hay) during a 220 day trial. Over the entire period, we were able to quantify a large variability in MLB intake between individuals (p < 0.01; ranging from 0 to 194 g/hd per day). Liveweight change (p < 0.05, R = 0.44) and feeding behaviour (e.g., feeding frequency and duration, p < 0.01; R² > 0.86) were positively correlated with MLB intake over the entire period but these correlations seemed to be affected by the type of feed. The intake of MLB seems to be explained by the individual behaviour of animals rather than the entire group. The use of in-paddock technologies enabled remote measurement of variability in supplement intake and cattle growth. The ability to monitor LW and feeding behavior of individual animals in a group could allow automatic individualized feeding of grazing cattle (amount and type of supplement) and managing low-performing animals under grazing conditions.

Associations between liveweight, body condition score and previous reproductive outcomes, and the risk of ewes bred at 18-months of age being dry at docking

AIMS Firstly, to investigate associations between liveweight and body condition score (BCS) of two-tooth ewes (18-months-old at breeding) at breeding, pregnancy diagnosis (PD) and pre-lambing and the risk of being dry at docking, on commercial New Zealand sheep farms. Secondly, to investigate the association between previous reproductive outcomes as ewe lambs, and risk of being dry at docking as two-tooth ewes. METHODS Two-tooth ewes (n=9,006) were enrolled in four cohorts from three commercial sheep farms between 2010-14. Ewes were weighed and BCS assessed immediately pre-breeding, at PD (mid-pregnancy) and pre-lambing. At PD, ewes were identified as either non-pregnant, or having single or multiple fetuses. Palpation and examination of udders at docking was used to classify each ewe as either lactating or dry at docking. RESULTS Overall, 437/8,025 (5.4%) of ewes that were diagnosed pregnant at PD were dry at docking. The risk of being dry at docking decreased with increasing pre-lambing conceptus adjusted liveweight (CALW) on all farms (p≤0.002); for 2010-born ewes from Farm A the OR=0.87 (95% CI=0.81-0.92); for Farm B the OR=0.88 (95% CI=0.83-0.92) and for Farm C the OR=0.86 (95% CI=0.79-0.95). The risk of being dry at docking also decreased with increasing CALW gain from PD to pre-lambing for all farms (p≤0.003); for 2010-born ewes from Farm A the OR=0.89 (95% CI=0.84-0.94); for Farm B the OR=0.85 (95% CI=0.81-0.89) and for Farm C the OR=0.88 (95% CI=0.80-0.96). There was no association between BCS at breeding, PD or pre-lambing and the risk of being dry at docking for 2010-born ewes from Farm A, Farm B or Farm C (p>0.05). For 2010-born ewes on Farm A, the risk of being dry at docking was greater for two-tooth ewes that were previously dry at docking as ewe lambs than those that were lactating at docking as ewe lambs (OR=1.7 (95% CI=1.1-2.8); p=0.018), but this difference was not observed for ewes on Farm B or Farm C (p>0.5). CONCLUSIONS There were negative associations between ewe CALW pre-lambing, and CALW gain between PD and pre-lambing, and risk of being dry at docking. For all cohorts, heavier ewes and those that gained CALW were less likely to be dry at docking than lighter ewes or those that lost CALW, however these relationships varied between cohorts.

Diet selection and performance of horses grazing on different heathland types

The number of horses in northern Spanish mountains has increased in recent decades, but little is known about their grazing behaviour, performance and potential for foal meat production. This research aimed to study the diet selection, liveweight (LW) changes and parasitic status of dry and lactating mares, and foals' LW gains, grazing on heathlands with different botanical composition. The experimental design consisted of three vegetation types: dominated by heather (Ericaceae) species (H), dominated by gorse (Ulex gallii; G) and co-dominated by gorse and heath-grasses (G-G), with four replicates per treatment (12 paddocks of 1.2 ha). The study lasted three grazing seasons (2010-12). Each year, 24 crossbred mature mares (310±52 kg LW) were used, managing one lactating mare with her foal plus one non-lactating mare per paddock from May to late summer or early autumn. In the case of H paddocks, animals had to be removed before (late August to early September) because of apparent loss of body condition. Animals were periodically weighed. Mares' diet composition was estimated using alkane markers, analysing the discrepancies in alkane concentrations between dietary plant components and faeces. Faecal samples were also analysed for gastrointestinal nematodes ova. Chemical composition of the main plant components (i.e. heather, gorse and grasses) revealed a low nutritive value, averaging 79, 115 and 113 g CP/kg dry matter (DM), respectively, that could restrict livestock performance. Mares initially selected gorse and grasses (0.47 and 0.40, respectively, in 2010), increasing heather consumption over time (from 0.13 in 2010 to 0.29 in 2012) as gorse availability decreased. The performance of both mares and foals was lower in H compared with G and G-G paddocks (-216 v. 347 g/day for mares, P<0.01; 278 v. 576 g/day for foals, P<0.05), whereas LW changes were more favourable in dry mares than in lactating ones (241 v. 78 g/day; P<0.05). Small strongyle (Cyathostominae) egg counts in mares' faeces increased across the grazing season with no differences between treatments. These results indicate that grazing by horses on gorse- and grass-gorse-dominated shrublands could be sustainable at least during part of the year (4 to 6 months). However, heather-dominated heathlands are not able to meet the nutritional needs of horses even for a short time (2 to 4 months). Nevertheless, the low nutritive quality of these vegetation communities, especially in autumn, requires animal access to other pastures with a higher nutritive value, or supplementary feeding, to enhance foals' growth and maintain sustainable grazing systems with productive herds.

Factors associated with fetal losses in ewe lambs on a New Zealand sheep farm

CASE HISTORY

As part of a production study of ewe lambs on a large farm in the Waikato region of New Zealand in 2011, pregnancy diagnosis was undertaken twice by trans-abdominal ultrasonography at 68-103 and 97-132 days of gestation. At the second pregnancy diagnosis 257/3,790 (6.8%) ewe lambs had evidence of non-viable fetuses or absence of a pregnancy that was present at the previous pregnancy diagnosis (fetal loss).

LABORATORY FINDINGS

Serum antibody titres for Leptospira interrogans serovar Pomona appeared generally higher in 10 ewe lambs with fetal loss compared with 10 that were still pregnant. Histopathological investigation was not able to confirm that fetal loss was associated with leptospial infection.

EPIDEMIOLOGICAL INVESTIGATION

In the 2012-born cohort of ewe lambs 443 were vaccinated with a bivalent leptospirosis vaccine and 882 unvaccinated. Serum was collected from 124 non-vaccinated ewe lambs between January and December 2013 for measurement of antibodies to Leptospira serovar Pomona and L. borgpetersenii serovar Hardjo-bovis using a microscopic agglutination test (MAT). Less than 5% of these ewe lambs were seropositive until May, but by August 85% and 48% of animals were seropositive to Leptospira serovars Hardjo-bovis and Pomona, respectively. Fetal loss in non-vaccinated ewe lambs was 78/882 (9%) compared with 23/443 (5%) in vaccinated ewe lambs. Combined data from the 2011- and 2012-born ewe lambs (n=5,115) were analysed using a logistic regression model and fetal loss as the dependent variable. In the final model fetal loss was associated with pre-mating bodyweight (p=0.003), weight change from pre-mating to initial pregnancy diagnosis (p<0.001), year born and leptospirosis vaccination status (p=0.013). Amongst the serologically monitored ewe lambs, there were associations between fetal loss and being seropositive to Leptospira serovar Pomona using titre cut-points of 1:48 and 1:768 (p<0.001).

CLINICAL RELEVANCE

Low pre-mating weight and/or low weight gain from mating to pregnancy diagnosis was associated with increased fetal loss, emphasising the importance of ewe lambs achieving target pre-mating weights and liveweight gains during pregnancy. Infection with Leptospira serovar Pomona was associated with fetal loss in the 2012-born cohort and the possibility of infection with this serovar should be considered when investigating cases of fetal loss.