Comparison of cephalonium alone and in combination with an internal teat sealant for dry cow therapy in seasonally calving dairy cows

AIM: To assess the effect of combining an internal teat sealant (ITS) and a long-acting cephalonium-based dry cow therapy (DCT) on the prevalence of cows with a somatic cell count (SCC) >150,000 cells/mL 60–80 days after calving, and the incidence of clinical mastitis diagnosed by farm staff in the first 100 days after calving.

METHODS: Cows from a spring-calving, pasture-based, dairy farm in the South Canterbury region of New Zealand were randomly allocated to receive cephalonium DCT (n=289) or cephalonium and internal teat sealant (n=304) at the end of lactation. Cows were inspected twice daily by farm staff during the dry period and following calving for signs of mastitis. Individual SCC were determined from herd tests conducted in the previous lactation and following calving. Logistic regression models were used to determine relationships with the prevalence of cows with a SCC >150,000 cells/mL after calving, and survival analysis was used to model time to the first case of clinical mastitis following calving at the cow and quarter level.

RESULTS: The OR for a cow with a SCC >150,000 cells/mL after calving, including age and individual SCC in the preceding lactation in the model, was 0.53 (95% CI=0.32–0.89) for cows treated with combination therapy compared to cows receiving cephalonium (p=0.017). At the cow level, including age and preceding SCC in the model, the hazard ratio for diagnosis of clinical mastitis by farm staff in the first 100 days of lactation was 0.60 (95% CI=0.39–0.98) for cows treated with combination therapy compared to cows receiving cephalonium (p=0.04). At the quarter level, the hazard ratio for diagnosis of clinical mastitis, with age included in the model, was 0.41 (95% CI=0.23–0.74) for the combination therapy compared to cephalonium alone (p<0.001).

CONCLUSIONS: The combination of internal teat sealant and cephalonium DCT was more effective than cephalonium alone at reducing clinical mastitis diagnosed by farm staff in the 100 days after calving, and the prevalence of cows with a SCC >150,000 cells/mL 60–80 days after calving.

CLINICAL RELEVANCE: This study adds to the evidence that the prevention of intra mammary infections throughout the dry period and up to calving by using combination therapy is important in reducing the incidence of farmer-diagnosed clinical mastitis and prevalence of cows with a SCC >150,000 cells/mL 60–80 days after calving.     

Investigation of the association between the interval from internal teat sealant administration to calving and early lactation clinical mastitis in New Zealand dairy heifers

AIMS: To examine the association between the interval from internal teat sealant (ITS) administration to calving and the incidence of farmer-recorded clinical mastitis in the first 30 days of lactation in pasture-based dairy heifers.

METHODS: Heifers that were administered an ITS by a single veterinary business in the South Island of New Zealand over the winter of 2014 were enrolled in a cross-sectional observational study. ITS was administered to all heifers on each participating farm on a single calendar day. The dates of calving and farmer-diagnosed clinical mastitis were recorded by farm staff. The interval from ITS administration to calving was categorised into four approximately evenly sized groups: <35, 35–48, 49–69 and >69 days. The quartile of the farm’s calving period in which each heifer calved was also investigated as a potential confounding variable. A hierarchical logistic regression model was constructed to determine the association between the interval from ITS administration to calving with the odds of clinical mastitis in the first 30 days of lactation.

RESULTS: Analysis was performed on 7,126 eligible heifers from 31 farms, with ITS administered between 9 May and 11 July 2014. The mean interval from ITS administration to calving was 52.9 (SD 24.4, min 1, max 137) days. Clinical mastitis was diagnosed in 420/7,126 (5.9 (95% CI=5.4–6.5)%) heifers between calving and day 30 of lactation. In the final multivariable model, which included calving period quartile, interval from ITS administration to calving was not associated with the odds of clinical mastitis (p=0.516). Compared to an interval from ITS administration to calving of <35 days, the adjusted OR of clinical mastitis for intervals of 35–48, 49–69 and >69 days were 0.83 (95% CI=0.59–1.17), 0.71 (95% CI=0.45–1.11) and 0.68 (95% CI=0.36–1.29), respectively.

CONCLUSIONS AND CLINICAL RELEVANCE: Within the range of intervals from ITS administration to calving observed in this study, there was no association with the odds of clinical mastitis in the first 30 days of lactation in dairy heifers. This study suggests that veterinary clinics may be able to extend their ITS administration service and treat dairy heifers earlier than the current recommendation of approximately 4 weeks before the planned start of calving.     

Resynchronising returns to service in anoestrous dairy cows in the South Island of New Zealand

AIMS: To investigate the effect of targeted resynchronisation of cows treated for non-observed oestrus before the planned start of mating (PSM), that were not detected in oestrus or pregnant 23 days after treatment (phantom cows), on the proportion pregnant at 42 days after PSM and the end of mating.

METHODS: Farm staff from eight herds in two regions of the South Island of New Zealand identified 1,819 cows not showing oestrus by 10 days before PSM. These cows were treated with intravaginal progesterone for 7 days, and I/M gonadorelin 10 days and 1 day before PSM. Three days before PSM they were injected with cloprostenol and equine chorionic gonadotrophin, with fixed time artificial insemination (FTAI) at PSM. By 23 days after PSM, 1,218 cows had not returned to oestrus. Of these, 161 cows confirmed not pregnant by transrectal ultrasonography were randomly assigned to no treatment (control group; n=74) or were resynchronised 25 days after PSM using the same treatment programme as above, with FTAI 35 days after PSM (n=87). All cows that returned to oestrus were artificially inseminated until 42 days after PSM, when natural mating was used. All cows were examined using transrectal ultrasonography 80 to 90 days after PSM to confirm conception dates.

RESULTS: Of the 1,819 anoestrous cows treated before PSM, 526 (29 (95% CI=23.1–34.0)%) had not been observed in oestrus by 23 days after PSM and had not conceived, so were diagnosed as phantoms cows. For resynchronised cows, 42/87 (48 (95% CI=37.8–58.8)%) were pregnant by 42 days after PSM compared to 21/74 (28 (95% CI=18.1–38.7)%) control cows (p=0.009). At the end of mating 58/87 (67 (95% CI=56.6–76.7)%) cows in the resynchronised group were pregnant and 46/74 (62 (95% CI=50.9–73.2)%) in the control group (p=0.554). The hazard of conception from 21 to 42 days after PSM was 1.9 (95% CI=1.07–3.12) times greater for resynchronised than control cows (p=0.026).

CONCLUSION: In cows not observed in oestrus and treated before PSM, resynchronisation increased the proportion pregnant by 42 days after PSM.

CLINICAL RELEVANCE: The benefit of resynchronisation depends on the number of anoestrous cows before PSM and the number of phantom cows after PSM. However at the herd-level it is likely that providing advice to reduce the known risk factors for cows not being observed in oestrus before the PSM may well be more cost effective than identifying and treating a sub-population of phantom cows.     

Effect of diets containing sulfate or chloride-based anionic salts,fed to grazing prepartum dairy cows,on concentrations of Ca in plasma,disease incidence and milk yield

AIMS: To compare the effect of two partial mixed ration diets containing either sulfate or chloride-based anionic salts, fed to grazing prepartum dairy cows, on concentrations of Ca, Mg, P and beta-hydroxybutyrate (BHB) in plasma, disease incidence and milk yield during the early postpartum period.

METHODS: The study was conducted on a seasonal-calving grazing dairy farm located in Benton (MO, USA). In August 2016, two groups of 200 cows were randomly assigned at 30 days before expected parturition to receive either a sulfate or chloride-based anionic diet, to achieve a dietary cation–anion difference (DCAD) of ?25?mEq/kg DM. Cows were fed partial mixed rations to provide 50% of their DM intake, with 50% provided by grazing fescue pasture. Urine samples were collected from 20 cows from each group once a week for 5 weeks until calving for pH assessment. At parturition, 42 cows per group were selected at random and blood samples collected on Days 1, 2, 3 and 7 postpartum. The study continued until 100 cows per group calved. Health events and cumulative milk yield until 30 days postpartum were recorded. Concentrations of Ca, P, and Mg in plasma at Days 1, 2, 3, and 7, and BHB in plasma at Day 7 postpartum were assessed.

RESULTS: Mean urine pH was lower in cows in the chloride than sulfate group (p≤0.06) on four of five sampling occasions. Mean concentrations of Ca in plasma on Day 1 were 2.00 (95% CI=1.94–2.05) and 1.91 (95% CI=1.88–1.97) mmol/L for the chloride and sulfate groups, respectively (p=0.15), and on Day 3 were 2.03 (95% CI=1.97–2.08) and 1.90 (95% CI=1.84–1.96) mmol/L, respectively (p=0.038). Concentrations of Mg, P and BHB in plasma and incidence of diseases postpartum were similar in both groups (p>0.05). There were no cases of clinical hypocalcaemia in either group.

CONCLUSIONS AND CLINICAL RELEVANCE: Prepartum cows fed a partial mixed ration with a negative DCAD containing chloride-based anionic salts and free access to a fescue pasture had lower prepartum urine pH, and higher concentrations of total Ca in plasma during the first week postpartum, than cows receiving a partial mixed ration containing sulfate-based anionic salts.     

Antimicrobial usage and risk of retreatment for mild to moderate clinical mastitis cases on dairy farms following on-farm bacterial culture and selective therapy

AIMS: To assess antimicrobial usage for treatment of mild to moderate clinical mastitis, and risk of retreatment, following implementation of an on-farm bacterial culture system and selective therapy based on culture results, and to assess compliance with treatment decision tree protocols and the level of agreement between results from on-farm culture and laboratory-based microbiology methods.

MATERIALS AND METHODS: Herdowners from seven dairy herds were asked to collect milk samples from cases of mild to moderate clinical mastitis between July 2015 and May 2016. All samples were cultured on-farm using a commercially available selective media and were also submitted for laboratory-based culture. Within sequential pairs of cows with mastitis, half were assigned to be treated without regard to culture results (Blanket group), and half were treated based on the on-farm culture results (Selective group) according to decision tree diagrams provided to the farmers. Culture results, treatments, and retreatments for clinical mastitis were recorded. The sum of the daily doses of antimicrobials used per cow, the number of retreatments and interval to first retreatment were compared between treatment groups.

RESULTS: The geometric mean sum of daily doses for quarters assigned to the Selective (1.72 (95% CI=1.55–1.90)) group was lower than for the Blanket (2.38 (95% CI=2.17–2.60)) group (p=0.005). The percentage of cows retreated for clinical mastitis did not differ between the Selective (21.7 (95% CI=10.5–25.9)%) and Blanket (26.1 (95% CI=20.9–31.3)%) groups (p=0.13), and there was no difference between groups in the hazard that cows would be retreated within 60 days of enrolment (hazard ratio=0.82 (95% CI=0.39–1.69); p=0.59). Compliance with the treatment protocols was higher amongst quarters assigned to the Selective (199/233; 85.4%) compared with the Blanket (171/249; 68.7%) group (p<0.001), and varied between farms from 64–94%. The overall agreement between results from on-farm and laboratory culture was 188/331 (56.9%; kappa=0.31; p<0.001), but varied between farms from 44.7–88.2% (p<0.001).

CONCLUSIONS: Use of on-farm culture with selective antimicrobial therapy resulted in approximately 25% lower antimicrobial usage, but was not associated with an increase in the proportion of cows retreated for clinical mastitis.

CLINICAL RELEVANCE: This study has demonstrated that on-farm culture and selective therapy based on culture results can be implemented on-farm. However, farms varied in their implementation of both the treatment protocols and microbiology procedures. Where such systems are to be used on-farm, specific training and on-going monitoring is required.     

Effect of treatment with an internal teat sealant at drying-off in cows wintered on forage crops in New Zealand on clinical mastitis and somatic cell counts

AIMS: To determine the impact of treatment with internal teat sealant (ITS) compared to no treatment at drying-off on the incidence of clinical mastitis (CM) during the dry period and 84 days after calving, and the prevalence of cows with somatic cell counts (SCC) ≥200,000?cells/mL at the first lactation herd test, for cows wintered on forage crops.

METHODS: In four dairy herds in the South Island of New Zealand, cows with no history of CM or individual SCC >100,000?cells/mL during the 2015–16 season were randomly assigned to treatment with ITS in each quarter (ITS group) at drying-off or no treatment (Control group). Cows were otherwise treated similarly, wintered on forage crops and transferred to pasture for calving and lactation. Cows were monitored over the dry period and for 84 days after calving, and any case of CM recorded. Individual SCC were recorded at the first herd test after calving.

RESULTS: Between drying-off and 84 days after calving 36/470 (7.7%) cows in the ITS groups and 73/442 (16.5%) cows in the Control group were diagnosed with CM (RR=0.46; 95% CI=0.26–0.73). The final multivariable logistic regression model included an interaction between treatment group and length of dry period. For a Friesian/Jersey cow, aged 4–8 years, with a dry period of 30–80 days, dried off without ITS, the probability of CM in the study period was 0.12 (95% CI=0.09–0.16), and for such a cow treated with ITS the probability was 0.07 (95% CI=0.05–0.10). For an equivalent cow, with a dry period of 81–140 days, which was untreated, the probability was 0.21 (95% CI=0.14–0.29), and for such a cow treated with ITS it was 0.05 (95% CI=0.02–0.11). At the first herd test after calving 77/383 (20.1%) cows in the Control group and 57/425 (13.4%) cows in the ITS group had SCC ≥200,000?cells/mL (RR=1.51; 95% CI=1.10–2.06).

CONCLUSIONS AND CLINICAL RELEVANCE: For these farms, treatment of cows with no history of elevated SCC or CM with ITS at drying-off halved the incidence of CM between drying-off and 84 days after calving, and reduced by 33% the proportion of cows with SCC≥200,000 at the first herd test after calving, compared with untreated cows. Treatment with ITS reduced the risk of CM proportionally more for cows with a dry period of 81–140 days than for cows with a shorter dry period.     

In situ provision of drinking water to grazing dairy cows improves milk production

AIMS: To determine the effect of providing water within the area grazed by dairy cows on milk yield and quality, compared to requiring cows to walk to a distant water trough, on a dairy farm in the Pampa region of Argentina during summer.

METHODS: Holstein dairy cows were allocated to two herds with similar parity, days in milk and milk production. They were grazed in one paddock that was divided in two, with a fixed water trough at one end. Cows were moved twice daily to grazing plots within the paddock. Control cows (n=66) could only access water from the fixed trough, whereas supplemented cows (n=67) also received water from a mobile trough within the grazing plot. Milk production of each cow, and water consumption of the two herds were measured daily over 62 days. Milk composition for each herd was determined weekly from Days 18 to 60 of the study, and grazing behaviour was observed between 08:00 and 16:00 hours on Days 11–15, 19–22 and 39–43.

RESULTS: Over the 62 days of the study, supplemented cows produced 1.39 (SE 0.11) L/cow/day more milk than Control cows (p=0.027). Estimated mean daily water intake was 50.4 (SE 2.1) L/cow/day for supplemented cows and 58.2 (SE 2.7) L/cow/day for Control cows (p=0.004). Percentage total solids in milk was higher for supplemented (12.5 (SE 0.06)%) than Control (12.4 (SE 0.04)%) cows (p=0.047). During the periods of behavioural observation, a higher percentage of cows in the water supplemented than the Control herd were observed in the grazing area (p=0.012).

CONCLUSIONS AND CLINICAL RELEVANCE: This preliminary study demonstrated that provision of water to dairy cows within the grazing plot was beneficial for milk production and composition, and may be associated with longer periods spent within the grazing area, during hot weather in the Pampa region of Argentina.     

Assessment of the accuracy of estimation of gestational age in cattle from placentome size using inverse regression

AIMS: To assess, in dairy cows between 60–160 days of gestation, whether the agreement between actual gestational age and that predicted by placentome size could be improved by using individual placentome measurements rather than a single average, and to identify how increasing the number of placentomes measured improved the prediction.

METHODS: Data were obtained from 58 cows examined using transrectal ultrasonography every 10 days between 60–130 days, and every 15 days between 130–160 days of gestation. For each cow, four to six placentomes in each of the pregnant and non-pregnant horns were examined from the region of the uterus near to the cervix. A mixed-effects model, which included cow as a random effect, and a simple linear regression which ignored within-cow correlation, were fitted to the data. Inverse regression was used to compare the 95% prediction bands obtained for estimating gestational age using the means of three, five or eight placentome measurements.

RESULTS: The fit of the mixed effects model was better than a simple linear regression (p<0.001) but the fitted lines from the two models were very similar. Using the simple regression model, for a mean placentome length of 15?mm estimated gestational age was 100 days, with 95% CI of 68–131 days for measurement of three placentomes, and 80–120 days for eight placentomes.

CONCLUSIONS: The agreement between placentome size and gestational age was improved by increasing the number of placentomes measured. Direct comparison of these CI with those for other published fetal measures was not possible as similar prediction bands have not previously been calculated for fetal measures; however one study reported a residual SD which had been calculated using size measurements as the predictor variable and age as the response variable. Using these data 95% CI were calculated to be ±9 days for crown-rump length and ±25 days for uterine diameter. These are likely to be an underestimate of the true CI and do not take account of the increase in variance of the difference between predicted and actual gestational age as gestational age increases.

CLINICAL RELEVANCE: Placentome measurement may be useful for estimating fetal age in late gestation. Further research is required to better establish the agreement between gestational age and the fetal measurements which are currently used to estimate fetal age.     

An epidemiological investigation of an idiopathic myopathy in hunting dogs in New Zealand

AIM: To conduct an epidemiological investigation of an idiopathic myopathy, known as “Go Slow” (GSM), which was initially recognised in dogs used for pig hunting. A secondary aim was to describe the hunting activities, diet and health of dogs used for pig hunting in New Zealand.

METHODS: A retrospective cohort study was conducted between June 2014–June 2017. Cases of GSM in dogs were diagnosed by veterinarians using a combination of clinical history, physical examination findings, serum biochemistry and/or skeletal muscle histology. A telephone interview was conducted with the owner or primary veterinarian to provide information regarding the dog’s diet and exercise over the 7 days preceding the onset of clinical signs. In August 2015, a separate online survey of owners of dogs used for pig hunting was conducted to characterise the normal hunting activities, diet and health of these dogs.

RESULTS: A total of 86 cases of GSM were recruited, of which 58 (67%) were pig hunting dogs, 16 (19%) pet dogs and 12 (14%) working farm dogs. Cases were most commonly reported in the upper North Island, and 65 (76 (95% CI=67–85)%) were from the Northland region. Processed commercial dog food had been fed to 93 (95% CI=88–98)% of affected dogs. Ingestion of raw, frozen or cooked wild pig in the preceding week was reported for 76 (88 (95% CI=82–95)%) dogs with the myopathy. In the survey of owners of healthy pig hunting dogs, 203 eligible responses were received; pig hunting was reported to most commonly occur in Northland (20.2%), Waikato (22.3%) and Bay of Plenty (23.2%) regions. Commercial dog food was fed to 172 (85 (95% CI=80–90)%) of the dogs included in this survey, and 55 (27 (95% CI=20–33)%) had eaten wild pig in the preceding week. The most common reported health problem in pig hunting dogs was traumatic wounds.

CONCLUSIONS: Cases of GSM were most commonly recognised in dogs used for pig hunting, but also occurred in pet and working farm dogs. The disease was most frequently reported in the upper North Island of New Zealand and ingestion of wild pig was a consistent feature in cases of this myopathy.

CLINICAL RELEVANCE: To minimise the risk of dogs developing this myopathy, it would seem prudent to avoid feeding any tissues from wild pigs to dogs in areas where the disease is known to occur.     

Prevalence of and risk factors for Campylobacter colonisation in broiler flocks at the end of the rearing period in France

1. A study was conducted to estimate the prevalence and quantification by species of Campylobacter infection in broiler flocks at the end of the rearing period and to identify associated risk factors.

2. A questionnaire about the rearing period was completed and caecal samples were collected from 121 broiler flocks in Brittany, France, during 2008.

3. Campylobacter was isolated in 87 out of 121 flocks – a prevalence of 71.9% (95% CI, 63.7–80.1%), including 40.5% of Campylobacter jejuni and 29.8% of Campylobacter coli.

4. The average concentration, in positive flocks, was 7.96 log₁₀ cfu/g and ranged from 3.15 to 10.32 log₁₀ cfu/g.

5. The average concentration by species was: 7.57 log₁₀ cfu/g for C. jejuni and 8.44 log₁₀ cfu/g for C. coli.

6. There was a seasonal effect, with increased risk of Campylobacter colonisation in June, July and August (odds ratio (OR) = 9.59, 95% CI 1.15–79.75).

7. The other factors, associated with lower risk of Campylobacter colonisation, were the acidification of drinking water (OR = 0.33, 95% CI 0.13–0.86), antibiotic treatment at the beginning of the rearing period (OR = 0.20, 95% CI 0.07–0.55) and rodent control around the house (OR = 0.18, 95% CI 0.03–0.95).

8. The results show that hygiene practices and biosecurity measures could lead to a reduction in Campylobacter colonisation.     

Production responses and cost-benefit of long-acting pre-lambing anthelmintic treatment of yearling ewes in two commercial flocks in New Zealand

AIMS: To investigate the production responses and cost-benefit of administering a controlled-release anthelmintic capsule (CRC) to pregnant yearling ewes prior to lambing.

METHODS: Yearling ewes from two commercial sheep flocks (A, n=489; B, n=248) in the North Island of New Zealand were enrolled in the study. Prior to lambing, CRC containing albendazole and abamectin were administered to half the ewes while the other half remained untreated. Ewe liveweights and body condition scores were measured prior to lambing, at weaning and, for Flock B, prior to subsequent mating. Lambs were matched to dams shortly after birth and the weight and number of lamb weaned per ewe were determined. A cost-benefit analysis was undertaken for Flock B considering the increased weight of lamb weaned per ewe, and the weight of ewes at the next mating and the benefit in terms of lambs born.

RESULTS: The mean weight at weaning of treated ewes was greater for treated than untreated ewes by 2.76 (95% CI 0.64–4.88)?kg in Flock A (p<0.001) and 2.35 (95% CI ?0.41–5.12)?kg in Flock B (p=0.003); the weight of lamb weaned per ewe was greater for treated than untreated ewes by 1.43 (95% CI ?0.71 to –3.49)?kg in Flock A (p=0.041) and 3.97 (95% CI 1.59–6.37)?kg in Flock B (p<0.001), and ewe liveweight prior to subsequent mating was greater for treated than untreated ewes in Flock B by 4.60 (95% CI 3.6–5.6)?kg (p<0.001). There was no difference in the percentage of lambs reared to weaning between treated and untreated ewes in either flock (p>0.8). The overall cost-benefit of treatment for Flock B was NZ$9.44 per treated ewe.

CONCLUSIONS AND CLINICAL RELEVANCE: Pre-lambing CRC administration to yearling ewes resulted in increased ewe weaning weights and weight of lamb weaned in both the flocks studied. There was an economic benefit in the one flock where this was assessed.     

Inter-observer agreement between two observers for bovine digital dermatitis identification in New Zealand using digital photographs

Aims: To assess the inter-observer agreement for detecting bovine digital dermatitis (BDD) lesions in digital colour photographs of the hind feet of cows, which had been taken while the animals were standing to be milked, between two trained observers.

Methods: Thirty-six photographs were selected from a total of 184 photographs held by the first author (R1), who had classified them as negative (n=11) or positive (n=25) for BDD. They were delivered to a technician (R2) who had previously visually inspected cattle for BDD lesions, and who then recorded the photographs as being either BDD-positive or BDD-negative. The percentage agreement between R1 and R2, and two other inter-observer agreement statistics, Cohen’s κ and Gwet’s first-order chance correction agreement coefficient (AC1), were calculated. The cumulative membership probabilities of Cohen’s κ and Gwet’s AC1 were then calculated for different benchmark ranges of κ.

Results: The percentage agreement between R1 and R2 was 33/36 (92%), Cohen’s κ was 0.80 (95% CI=0.57–1.0) and Gwet’s AC1 was 0.86 (95% CI=0.69–1.0). Based on the cumulative membership probabilities for Gwet’s AC1, there was 75% probability that the two observers had almost perfect agreement (κ≥0.81). For both Cohen’s κ and Gwet’s AC1, there was >95% probability that the two observers had at least substantial agreement (κ≥0.61).

Conclusions: The two trained observers had at least substantial agreement in identifying from a digital photograph as to whether BDD lesions were present or absent. Therefore results from the two could be used interchangeably.

Clinical Relevance: Visual assessment for BDD lesions in the milking parlour can be subjective. However a high agreement between these two trained BDD inspectors means BDD prevalence reported from different regions in New Zealand by these two can be directly compared.     

Effects of male body weight,strain and dietary protein content on fertility and musculo‐skeletal disease in naturally mated broiler breeder males

1. The effects of male body weight at mating and different rates of gain on overall fertility were studied in two strains of broiler breeder males fed on a diet containing 160 or 120 g crude protein/kg. Sexual activity, musculo‐skeletal disease and culling were also assessed.

2. There were no differences in early fertility between males weighing 3–0 or 3–5 kg at the start of the mating period, or between males gaining 1.0 or 1.5 kg body weight from mating to 60 weeks of age.

3. There were no differences in fertility between males fed on the two diets differing in crude protein content.

4. One strain of male had lower fertility than the other and this was associated with a greater weight of breast muscle, lower frequency of observed copulations and a higher number of incompleted matings.

5. Sexual activity declined and the number of spermatozoa trapped on the perivitelline membrane increased with age.

6. There were no differences among the treatments in the prevalence of musculo‐skeletal lesions (destructive cartilage loss). As a proportion destructive cartilage loss occurred in 0^‐67 of the males at 66 weeks of age. Degeneration of the antitrochanter was present in 3 of 50 females examined and a cartilage flap in the medial condyle of the tibiotarsus occurred in 15 of these birds.

7. Beak lesions were the most important cause of male culling which averaged 0–24 as a proportion of the males at the start of the experiment.     

Protein and energy metabolism in two lines of chickens selected for growth on high or low protein diets

1. Genetic adaptation was investigated in broilers selected for seven generations on a normal (A) or a low (B) protein diet.

2. Protein and energy metabolism were studied in males from these selected lines fed on a diet of intermediate protein content.

3. All selected birds retained more nitrogen than those studied 10 years previously.

4. There was no difference in nitrogen retention between groups, although relative growth rate of group B birds was higher.

5. Heat productions relative to gross energy intake were 0.38 (group B) and 045 (group A). Energy retentions relative to gross energy intake were 0.39 (group B) and 0.35 (group A); the difference being primarily due to higher fat retention in group B.

6. Using a common maintenance requirement for metabolisable energy, group B utilised metabolisable energy for growth (0.78) better than did group A (0.71).

7. At 53 d of age plasma glucose (10%) and insulin (50%) were higher in group B than in group A.     

Assessing obesity in adult dogs and cats presenting for routine vaccination appointments in the North Island of New Zealand using electronic medical records data

Aims: To assess the prevalence of obesity in adult dogs and cats presented to first-opinion veterinary clinics in the North Island of New Zealand for routine vaccination appointments, using electronic medical records.

Methods: Ten first-opinion veterinary clinics across the North Island of New Zealand provided electronic medical records for all routine vaccination appointments for adult (>1 year old) dogs and cats between 1 January 2011 and 30 June 2016. Animals with a body condition score (BCS) of 6 or 7 on a 9-point scale and 4 on a 5-point scale were classified as overweight; those with a BCS of 8 or 9 on a 9-point scale and 5 on a 5-point scale were classified as obese. A total of 106,144 records were available over the study period, of which 48,041 (45.2%) had both a recorded weight and BCS.

Results: Of the 24,247 records for dogs with both BCS and weight, 6,324 (26.1%) were classified as overweight, and 551 (2.3%) as obese. The prevalence of dogs classified as overweight or obese was highest in dogs aged between 5–13 years. The odds of desexed dogs being classified as overweight or obese was greater than the odds for intact dogs (OR=1.42 (95% CI=1.29–1.57), p<0.001) adjusting for the effects of age. Of the 23,794 records for cats with a recorded weight and BCS, 5,222 (21.9%) were classified as overweight, and 622 (2.6%) as obese. The prevalence of cats classified as overweight or obese was highest in cats aged between 5–11 years. The odds of desexed cats being classified as overweight or obese tended to be greater than the odds for intact cats (OR=1.14 (95% CI=0.98–1.31); p=0.075), adjusting for the effects of age.

Conclusions: Although there are limitations with using electronic medical records to estimate the prevalence of obesity in companion animal populations, the results highlight that a significant number of animals presenting for routine vaccination appointments were classified as overweight or obese.

Clinical Relevance: It is important for veterinarians to record both patient body condition and weight during routine preventative care appointments to allow accurate ongoing monitoring of trends in obesity at both the patient and population levels.

Abbreviations: BCS: Body condition score     

Effects of a dry-ice process on surface and carcase decontamination in the poultry industry

1. The objective of this study was to evaluate the effects of dry-ice decontamination on equipment and carcase surfaces in a poultry slaughterhouse and to present an effective alternative method to the conventional decontamination processes.

2. Appreciable reductions occurred in total aerobic mesophilic bacterial counts of surface swab samples treated with dry ice (maximum difference 3.92 log cfu/100 cm²).

3. After dry-ice treatment, Listeria spp. were detected on surfaces of pluckers and chiller cylinders, whereas Salmonella spp. were totally inhibited.

4. A dry-ice spraying application was more effective than a dry-ice immersing application on total aerobic mesophilic bacteria and yeast and mould counts on poultry carcases.

5. Dry-ice treatment has advantages over conventional processes. Unlike other decontamination techniques, there are no residues, so no need to wash off chemical residues from surfaces as it removes contaminants effortlessly and is environmentally friendly.

6. Dry-ice blasting of production equipment can reduce the microbial load and has potential for use in the poultry industry.     

Effect of probiotic supplementation on serum/yolk cholesterol and on egg shell thickness in layers

1. The effect of probiotic supplementation on egg production, on serum and yolk cholesterol and on egg shell thickness in 24 White Leghorn layers was studied from 28–38 weeks of age.

2. In 3 treatments the diet was supplemented with 0, 100 and 150 mg probiotic/kg food.

3. In the 100 mg probiotic group, egg production improved by 5%, and shell thickness improved slightly, with fewer thin‐shelled eggs than in the control (8.6% compared to 18.6%).

4. The initial serum cholesterol concentration of 170.2 mg/dl in control birds remained similar throughout the 10‐week experimental period, whereas in the 150 mg group the initial value of 176.5 mg/dl decreased to 114.3 mg by week 10.

5. Yolk cholesterol concentration was 14.69 mg in the control group and 11.28 and 11.37 mg/g in the 100 and 150 mg probiotic groups respectively. Overall mean total egg cholesterol was thus reduced by probiotic supplementation.     

The use of electromyography interference pattern analysis to determine muscle force of the deep digital flexor muscle in healthy and laminitic horses

Background: In equine laminitis, the deep digital flexor muscle (DDFM) appears to have increased muscle force, but evidence-based confirmation is lacking.

Objectives: The purpose of this study was to test if the DDFM of laminitic equines has an increased muscle force detectable by needle electromyography interference pattern analysis (IPA).

Animals and Methods: The control group included six Royal Dutch Sport horses, three Shetland ponies and one Welsh pony [10 healthy, sound adults weighing 411 ± 217 kg (mean ± SD) and aged 10 ± 5 years]. The laminitic group included three Royal Dutch Sport horses, one Friesian, one Haflinger, one Icelandic horse, one Welsh pony, one miniature Appaloosa and six Shetland ponies (14 adults, weight 310 ± 178 kg, aged 13 ± 6 years) with acute/chronic laminitis. The electromyography IPA measurements included firing rate, turns/second (T), amplitude/turn (M) and M/T ratio. Statistical analysis used a general linear model with outcomes transformed to geometric means.

Results: The firing rate of the total laminitic group was higher than the total control group. This difference was smaller for the ponies compared to the horses; in the horses, the geometric mean difference of the laminitic group was 1.73 [geometric 95% confidence interval (CI) 1.29–2.32], and in the ponies this value was 1.09 (geometric 95% CI 0.82–1.45).

Conclusion and clinical relevance: In human medicine, an increased firing rate is characteristic of increased muscle force. Thus, the increased firing rate of the DDFM in the context of laminitis suggests an elevated muscle force. However, this seems to be only a partial effect as in this study, the unchanged turns/second and amplitude/turn failed to prove the recruitment of larger motor units with larger amplitude motor unit potentials in laminitic equids.     

Quality characteristics of quail eggs

1. An experiment was carried out with laying Japanese quail to study the influence of age on their egg quality.

2. Egg, yolk, albumen and shell plus membrane weights increased, whereas the egg shape, specific gravity and shell thickness decreased between 49 and 154 days of age.

3. Yolk, albumen and shell plus membrane comprised 32–59%, 53–57% and 7–80%, respectively of the total egg weight.

4. Regression between the quail's age and the characteristics of eggs were derived and correlation coefficients ranged from —0–42 to — 0–86. The albumen weight was more highly correlated with egg weight than yolk weight.

5. Relationships were also derived between egg shape and specific gravity, and egg shape and albumen weight.

6. It was concluded that the eggs’ characteristics were modified as the quails aged, and the best criterion of the shell's strength was the egg shape.     

Scrotal circumference,bodyweight and semen characteristics in growing dairy-breed natural-service bulls in Tasmania,Australia

Aims: To provide herd managers with a set of decision rules allowing them to predict the likelihood that a juvenile bull is ready for Bull Breeding Soundness Evaluation (BBSE), or breeding, if bodyweight and scrotal circumference are known.

Methods: This was a longitudinal study following two groups of young pasture-fed Holstein and Jersey bulls from northwest Tasmania, Australia. Individual scrotal circumference, bodyweight and semen characteristics were recorded at 6–8 weekly intervals, from 6–18 months of age. Classification and regression tree analyses were used to predict the probability that a bull had ≥70% normal sperm morphology based on scrotal circumference and bodyweight measurements.

Results: Overall 1,661 scrotal circumference and bodyweight measurements were obtained, and 518 semen samples from 356 bulls were assessed for sperm morphology, from 16 examination sessions that took place between 29 May 2015 and 17 August 2016. Classification and regression tree analyses generated a decision tree for Holstein bulls with four node endpoints, and for Jersey bulls with three node endpoints. Diagnostic test performance showed that for Holstein bulls, using the node endpoints of scrotal circumference ≥27?cm and bodyweight ≥349?kg, 98% had ≥70% normal sperm (positive likelihood ratio 10.4; 95% CI?=?2.7–41), and using the node endpoints of scrotal circumference ≥27?cm and bodyweight between 282–349?kg, 89% had ≥70% normal sperm (positive likelihood ratio 1.6; 95% CI?=?0.9–2.6). For Jersey bulls, using the node endpoints of bodyweight ≥259?kg and scrotal circumference ≥29?cm, 88% had ≥70% normal sperm (positive likelihood ratio 3.4; 95% CI?=?1.6–7.0).

Conclusions: This study provides a set of relatively simple decision rules based on bodyweight and scrotal circumference measurements that allows herd managers to assess the likelihood that juvenile bulls are ready for BBSE or breeding.

Abbreviations: BBSE: Bull breeding soundness evaluation; BRT: Boosted regression tree