Pregnancy loss in dairy cattle in the Waikato region of New Zealand

AIM: To define the incidence rate of pregnancy loss and risk factors for those losses in pasture-fed dairy cattle in the Waikato region of New Zealand. METHODS: Cows (n=2,004) from 10 pasture-fed, spring-calving dairy herds in the Waikato were enrolled following confirmation of pregnancy 29-45 days after insemination, for inseminations that occurred within the first 16 days of the seasonal breeding period. Transrectal ultrasonographic examinations for pregnancy were conducted at approximately 6, 8, 10, 14 and 22 weeks gestation, and subsequent calving data were recovered. Pregnancy loss was defined as having occurred when a confirmed pregnancy was not re-diagnosed, when gross abortion was detected, or when a cow calved <265 days after the confirmed conception date. Data were analysed using reverse stepwise logistic regression and Cox's proportional hazards analysis. RESULTS: A total of 128 (6.4%) pregnancy losses were detected. The incidence rate was higher in early compared to late gestation (10.9 vs 2.8 losses/10,000 cow-days between Weeks 6-10 vs Weeks 10-14, respectively; p<0.001). Higher rates of loss were associated with the occurrence of clinical mastitis (Hazards ratio (HR)=1.57; p=0.071), being treated for anoestrus (HR=1.69; p=0.007), and in cows that had calving-to-conception intervals < or =63 days compared with those that had calving-to-conception intervals >92 days (HR=2.49; p=0.06). In addition, the rate of pregnancy loss differed between herds (p=0.05). CONCLUSIONS: The highest rate of pregnancy loss occurred in early gestation. Clinical mastitis, anoestrus and calving late in the calving season were risk factors for pregnancy loss. CLINICAL RELEVANCE: Pregnancy diagnosis using ultrasonography can be undertaken from 28 days post-insemination. However, due to the high rate of pregnancy loss at this stage of gestation, herdowners need to be warned of possible losses, and cows should be re-examined to confirm pregnancy before certification of pregnancy status is given.     

Effects of periparturient diseases and conditions on the reproductive performance of New Zealand dairy cows

AIM: To determine the effect of retained foetal membranes (RFM), periparturient recumbency, calf mortality, dystocia, twin births and induction of parturition on submission and pregnancy rates of pasture-fed, seasonally-calving dairy cows in New Zealand. METHODS: Data were retrospectively collected for 2652 cows from 11 herds on the occurrence of periparturient diseases and condition, calving date, age and treatment for anoestrus prior to the planned start of mating (PSM). The effects of each disease or condition on submission and pregnancy rate by 28 days after PSM, final pregnancy rate, and the proportion of cows that conceived more than 50 days after PSM were examined using separate logistic regression models. Results are expressed as odds ratios (OR). Additionally, the effect of each disease or condition on the interval from PSM to conception was examined using survival analysis. Age, herd and late calving (i.e. cows calved < or =40 days before PSM) were included as factors in the models examined. RESULTS: Induction of parturition increased the risk of RFM (OR=3.3, p<0.01). The 28-day submission rate was affected by age and herd but not by any of the periparturient conditions examined. The 28-day pregnancy rate was reduced by RFM (OR=0.04, p<0.05), induction of parturition (OR=0.67, p<0.01), assisted calving (OR=0.61, p<0.01), late calving (OR=0.55, p<0.05) and anoestrus (OR=0.27, p<0.05). The final pregnancy rate was reduced by RFM (OR=0.013, p<0.01), induction (OR=0.25, p<0.05), assisted calving (OR=0.30, p<0.005) and anoestrus (OR=0.32, p<0.05), and was increased if the cow was submitted for mating within 28 days after PSM (OR=2.72, p<0.05). Effects of recumbency and twinning were not significant in any of the models. CONCLUSIONS: Cows that had had RFM or were assisted, induced or late to calve, had significantly lower pregnancy rates or took longer to conceive than unaffected herd-mates. CLINICAL RELEVANCE: Intervention programs aimed at the examination and treatment of cows with periparturient conditions may improve the reproductive performance of New Zealand dairy herds. Investigations of poor reproductive performance of a herd should include analysis of the prevalence and effects of periparturient diseases and conditions.     

Risk factors for and reproductive outcomes of phantom cows on New Zealand dairy farms

AIMS: To determine some of the risk factors for cows not observed in oestrus within 35–42 days of an unsuccessful artificial insemination (AI; phantom cows), and the reproductive outcomes and effect of treatment of phantom cows.

MATERIALS AND METHODS: Over 2 years, in dairy herds from the Waikato (n=10) and Canterbury (n=4) regions of New Zealand, pregnancy diagnosis was carried out 35–42 days after AI on cows that had been inseminated in the first 3 weeks after the start of mating (PSM) but had not been seen returning to oestrus. Risk factors for phantom cows were analysed using a generalised linear mixed effect model.

In Year 1, all phantom cows were left untreated. In Year 2, phantom cows were categorised as having a corpus luteum (CL) (CL+ n=120), or having ovarian follicles ≥10 (n=101) or <10 (n=40)?mm in diameter. Cows with a CL were treated with cloprostenol or untreated and placed with bulls. Cows with no CL received intravaginal progesterone (P4) for 7 days, with injection of gonadotrophin-releasing hormone (GnRH) on Days 0 and 9, and cloprostenol on Day 7 followed by AI. Pregnancy diagnosis of all cows took place 100–120 days after PSM and interval to conception and final pregnancy rate determined.

RESULTS: Overall, of cows inseminated in the first 3 weeks after PSM that did not return to oestrus, 610/6,734 (9.1%) were phantom cows. From the final multivariable analysis, treatment for anoestrus, BCS ≤4.0 at mating, being 2 or >6 years of age, and pure-bred, and decreasing interval between calving and mating, until 98 days post calving, were associated with increased odds of being a phantom cow. Compared to all other groups of cows, phantom cows had a longer interval to conception (p<0.001) and a lower final pregnancy rate (p<0.001).

Treatment of CL+ cows or cows with follicles ≥10?mm did not affect reproductive outcomes (p>0.3). For cows with follicles <10?mm treatment decreased the final percentage not pregnant (3/27; 11%; p=0.01) and interval to conception (21 days; p=0.02) compared with controls (7/13; 54% and 37 days, respectively).

CONCLUSIONS AND CLINICAL RELEVANCE: Risk factors for phantom cows were identified that could be manipulated to reduce the number of phantom cows in a herd, in particular increasing BCS. Treatment of the majority of phantom cows did not improve reproductive performance.     

Efficacy of controlled-release capsules containing monensin for the prevention of subclinical ketosis in pasture-fed dairy cows

AIMS: To determine the effectiveness of intra-rumenal controlled release capsules (CRC) containing 32?g of monensin administered pre-calving to reduce the cumulative incidence of subclinical ketosis (SCK) in mainly pasture-fed dairy cows.

METHODS: Cows (n=837) due to calve in the first 6 weeks of the spring calving period were enrolled from four commercial herds in the Waikato region of New Zealand in a blinded, randomised, negative-controlled field trial. Three weeks before the start of the calving period cows were randomly allocated to receive either no treatment (control) or a single CRC containing monensin and then blood sampled on two occasions, 7 days apart within 12 days following calving for measurement of concentrations of beta hydroxybutyrate (BHBA) in blood. Cows were diagnosed with SCK if the concentration of BHBA in blood in either of these samples was ≥1.2?mmol/L.

RESULTS: Fewer treated cows were diagnosed with SCK within 12 days post-calving than control cows (144/340 (42.4%) vs. 192/336 (57.1%); p<0.001). There was no interaction between treatment group and age, breed or herd of origin. From the final multivariable model it was estimated that treatment with CRC containing monensin reduced the absolute cumulative incidence of SCK by 17.9 (95% CI=9.2–25.8)% compared to no treatment.

CONCLUSIONS: Treatment with a CRC containing monensin >10 days prior to calving reduced the cumulative incidence of SCK of pasture-based dairy cows in commercial dairy herds within 12 days post-calving.

CLINICAL RELEVANCE: Administration pre-calving of an intra-rumenal bolus containing monensin can be considered as one of a range of management options for the control of SCK in early lactation.     

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.     

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.     

Feline T-Lymphotropic Virus (FTLV) (Feline Immunodeficiency Virus Infection) in cats in New Zealand

AIM: To identify and enumerate colony forming units (cfu) of mastitis pathogens in bulk tank milk (BTM) from pasture-fed New Zealand dairy cows in the Waikato region.

METHODS: BTM samples from seven seasonal-calving dairy herds in the Waikato region were collected monthly from August to December 2004 (cows calved during July-September). Milk samples were cultured on blood aesculin and MacConkey agar plates for 24 h, and the number of mastitis pathogens identified and counted.

RESULTS: Colonies identified in BTM included aesculinpositive streptococci, Staphylococcus aureus, coagulase-negative staphylococci (CNS), and coliforms; counts ranged from zero to >1,000 cfu/ml. Counts >1,000 cfu/ml for total aesculin-positive streptococci, CNS and coliforms were present in 48%, 51% and 11% of BTM samples, respectively. Counts of Staph. aureus ranged from zero to 1,000 cfu/ml, but first appeared in BTM samples only in October. Staphylococcus aureus was repeatedly isolated in BTM from 4/7 farms during the testing period.

CONCLUSIONS: Counts of mastitis pathogens in this study appeared high relative to interpretive criteria set by other workers, which may indicate a high prevalence of mastitis risk factors on these farms. Interpretation of results is difficult as aesculinpositive streptococci, CNS and coliforms can be isolated from the environment as well as from cows with clinical or subclinical mastitis. Furthermore, Staph. aureus is inconsistently excreted from infected bovine mammary glands. More extensive study of this method is required in New Zealand to attempt to further validate the interpretation of results of bacterial culture of BTM.

CLINICAL RELEVANCE: This method may be used to monitor challenge from mastitis pathogens over time as part of milk quality control programmes. The technique may be of use as a screening test to provide information to veterinarians, affording them the opportunity to have an input into mastitis control on dairy farms in New Zealand.     

Management of dairy heifers and its relationships with the incidence of clinical mastitis

AIM: To describe aspects of management of dairy heifers before calving and determine risk factors for clinical mastitis postpartum in heifers, at the herd level, under pasture-based management systems in the Waikato and Taranaki regions of New Zealand. METHODS: Dairy herdowners (n=578) provided information via a prospective survey about their practices for rearing heifers and management of mastitis. A proportion of herdowners (n=250) subsequently provided data on the cases of clinical mastitis in their herds, including the date, cow identification, age and quarter affected from cases occurring in the 4 months after the planned start of calving (PSC) in the subsequent lactation. The relationship between management factors and the proportion of heifers diagnosed with clinical mastitis within a herd was examined using bivariate and multivariate analyses. RESULTS: The herd average percentage of heifers with clinical mastitis was 13.6 (95% confidence interval (CI)=12.3-14.9)%, and multiparous cows with clinical mastitis was 9.0 (95% CI=8.2-9.8)% in the first 4 months of lactation. There were positive relationships between the proportion of heifers with clinical mastitis and average milk production per cow (kg milksolids/ lactation; p<0.001), number of cows milked per labour unit (p=0.003), stocking rate (<> 3.30 cows/ha; p=0.002), and incidence of clinical mastitis in multiparous cows (%/120 days; p<0.04), in the final multivariate model. The proportion of heifers with clinical mastitis per herd was lower in herds that milked their lactating cows in multiple groups (p=0.02). CONCLUSIONS: The risk of clinical mastitis in heifers was significantly associated with management practices. It may be possible to reduce the incidence of clinical mastitis in heifers by modification of management practices at the herd level, and further studies are required to investigate this.     

Periparturient use of parenteral micronised procaine penicillin to reduce the risk of clinical mastitis in heifers after calving

Mastitis in primiparous heifers immediately postpartum can be both a significant welfare concern and a heavy economic loss. Interventions successfully researched include intramammary therapies. This study considered the clinical and practical effects of a parenteral approach to controlling clinical mastitis in heifers immediately postpartum. The objective of this field trial was to determine whether preventative treatment of heifers with a single parenteral treatment of 15 million iu micronised procaine penicillin within 12h after calving would reduce the incidence of clinical mastitis in early lactation as detected by farmers. All heifers (n=609) calving on three commercial dairy farms in New Zealand during the spring of 2006 were randomly allocated to either treatment or no treatment. Treatment (15 million iu micronised procaine penicillin) was given at the first milking following calving. All clinical mastitis was recorded. Treatment reduced the odds of having clinical mastitis within the first 7 days in milk by over half (Mantel-Haenszel adjusted OR=0.456; p=0.044); and reduced the odds of having mastitis within the first 100 days in milk by just under half (Mantel-Haenszel adjusted OR=0.518; p=0.027). Treatment had a significant effect on increasing the median days to clinical mastitis (p=0.019; beta=1.961, LCI 1.117, UCI 3.445). Preventative treatment of heifers immediately following calving with 15 million iu micronised procaine penicillin parenterally could be of benefit as part of a control programme aimed at reducing the incidence of clinical mastitis in heifers in their first lactation.     

Prolonged service intervals in cattle

A trial based on progesterone radioimmunoassay of milk samples is described. Samples from 2274 cows in 14 herds were collected on the day of insemination and 7, 23 and 30 days later, unless a return to service occurred before the designated sample date. Two additional samples were collected from cows which returned to service more than 35 days after the first service, one on the day of the return and another seven days later. All six samples from these cows were assayed for progesterone concentration.

Late returns, defined as returns to oestrus 36 or more days after mating, occurred in 8.6% of the cows. Milk progesterone assay results indicate that of these apparently late-returning cows, 55.9% suffered a loss of the conceptus, 22.1% had not been detected in oestrus around 21 days after first insemination, 11.8% were in anoestrus at insemination, 5.6% conceived to the insemination and were pregnant when thought to have had a late return, 2.6% were in prooestrus or dioestrus at insemination and 2.1% went into anoestrus after an oestrus insemination.

The average prevalence of late returns after the 35th day (8.6%) and the estimated incidence of losses of concepta (4.8%) are lower than those reported in comparable studies elsewhere. Although many of the late-return cows were mated again and conceived, this syndrome nevertheless contributes significantly to the wastage rate, at least in New Zealand dairy herds with their strictly seasonal calving pattern. The implications of these findings are discussed and recommendations for their prevention are made where appropriate.     

Skin sensitivity to tuberculins in cattle vaccinated against Johne's disease

Aim: To evaluate the efficacy of a dry-cow antibiotic preparation containing cloxacillin plus ampicillin in a formulation that gives a 10-week duration of action, in comparison to products containing cephalonium (10-week action) or cloxacillin alone (7-week action).

Methods: A total of 493 cows were selected from 6 spring-calving dairy herds in the Manawatu region of New Zealand, according to the criteria of the SAMM plan, to receive intramammary antibiotic therapy at the end of lactation (drying off). Cows were randomly allocated to receive 1 of the 3 dry-cow antibiotic products under investigation. Cows were examined twice during the dry period and twice daily during the first 10 days of their subsequent lactation for the presence of mastitis. Milk samples were collected from individual quarters at the time of drying off and at 7 and 28-35 days after calving, for determination of milk somatic cell counts (SCC). Bacteriology was carried out on milk samples taken from cows that developed mastitis during the first 10 days after calving.

Results: No cows developed mastitis during the dry period. Sixteen cows developed clinical mastitis within 10 days of calving; there was no difference in incidence between treatments. Streptococcus uberis was the most commonly isolated organism. Mean SCC on Day 7 were lower (p = 0.019) in cephalonium-treated quarters (189.9 ± 28.4 × 10³ cells/ml) than in cloxacillin-treated quarters (388.7 ± 71.2 x 10³ cells/ml); values in quarters receiving cloxacillin plus ampicillin were intermediate (252.0 ± 47.0 × 10³ cells/ml). SCC were similar between treatment groups on Day 28–35.

Conclusions: The use of a combination of cloxacillin plus ampicillin was effective for the prevention of mastitis during the dry- and peri-calving-periods in pastured dairy cattle.     

Prevalence and incidence of intramammary infections in lactating dairy goats

AIM: To determine the prevalence of intramammary infection (IMI) of lactating dairy goats between 0 and 4 days postpartum, the prevalence and incidence rate of new IMI at Weeks 2, 14 and 27 of lactation, and the relationship between herd-level prevalence of IMI and bulk tank somatic cell count (BTSCC).

METHODS: Milk samples were collected from 8% of a herd (total 624 does) from 18 dairy goat herds in the Waikato region of New Zealand, for bacteriology and somatic cell count (SCC) determination, from both glands within 4 days of kidding (Week 0) and again at Weeks 2, 14 and 27. Prevalence of IMI was determined at each time point and incidence rate calculated for Weeks 0–2, 2–14, and 14–27. Greenwood and Reed-Frost models were compared for estimation of the transmission parameter for all pathogens, and for Staphylococcus aureus, coagulase negative staphylococci (CNS) and Corynebacterium spp. separately.

RESULTS: Bacteria were isolated from 1,122/4,814 (23.3%) glands, with CNS (13.4%) and Corynebacterium spp. (7.3%) being the most common isolates. Prevalence of any IMI increased with stage of lactation, varied among herds, and increased with age (all p<0.05). Incidence rate was 80, 24 and 7 new IMI/10,000 gland days for Weeks 0–2, 2–14 and 14–27, respectively. Incidence rate for any IMI increased with age and with the presence of an IMI in the contralateral gland, and varied among herds (p<0.001). The transmission of each pathogen was better modelled assuming contagiousness (Reed-Frost models), than not (Greenwood models).

At gland level, IMI increased SCC at all stages of lactation (p<0.001). The gland prevalence of IMI within herds was positively associated with ln BTSCC at Week 2 (p=0.02), but not Weeks 14 or 27 (p>0.05).

CONCLUSIONS: Prevalence of IMI increased with stage of lactation, but the highest incidence rate of new IMI occurred in early lactation. Models accounting for the contagious nature of infection fitted better than those not accounting for contagiousness. BTSCC was only associated with prevalence of IMI in early lactation.

CLINICAL RELEVANCE: Reduction of BTSCC in dairy goats may be best achieved by minimising the prevalence and incidence of new IMI in early lactation. Further studies are required to define management factors associated with the between herd, and stage of lactation, effects on prevalence and incidence rate in order to reduce BTSCC throughout lactation.     

Factors associated with early and mid-to-late fetal loss in lactating and nonlactating Holstein cattle in a hot climate

The purpose of this study was to evaluate associations of lactation, somatic cell count score (SCCS) at breeding, milk yield, lactation number, interval from calving to breeding (days open), number of times inseminated, and season of breeding on fetal loss for lactating Holstein females (both first-parity and multiparous cows) and nonlactating Holstein heifers in a hot climate. Females were palpated between d 40 and 50 of gestation and again at d 70 to 80 to determine pregnancy status. Early fetal loss was defined as a loss that occurred after d 40 to 50 but before d 70 to 80. Mid-to-late fetal loss represented losses after d 70 to 80 but before expected calving. Lactating females had higher early (P = 0.055) and mid-to-late fetal loss (P < 0.05) than nonlactating heifers. Those lactating females with increased days open experienced greater early (P < 0.05) and mid-to-late fetal loss (P = 0.055), whereas lactating females with an elevated SCCS encountered greater mid-to-late fetal loss (P < 0.01). Milk yield, lactation number, number of times inseminated, and season were not associated with early or mid-to-late fetal loss. For nonlactating heifers, there were no associations between number of times inseminated, season, or age at breeding on early or mid-to-late fetal loss. In conclusion, lactating females were more likely to suffer early and mid-to-late fetal loss than nonlactating heifers. Also, days open and SCCS at breeding were related to ability of lactating females to maintain pregnancy, but there were no relationships between fetal loss and milk yield, lactation number, number of times inseminated, or season.     

Accuracy of fetal age estimates using transrectal ultrasonography for predicting calving dates in dairy cows in seasonally calving herds in New Zealand

AIM: To describe the accuracy of transrectal ultrasonography for predicting calving dates in dairy cows under typical New Zealand conditions and to assess potential risk factors for differences between predicted and actual calving dates.

METHODS: Data were collected from 116 seasonally calving herds over 2 years in a retrospective single cohort study. Transrectal ultrasonography was undertaken by experienced veterinarians (n=12) to determine if cows were pregnant, and if so to estimate fetal age. Predicted calving date was calculated by adding 282 days to the estimated conception date. Accuracy was assessed using differences between predicted and actual calving dates for each animal. Potential risk factors for animals calving >10 days before or after their predicted calving date were assessed using multinomial logistic regression models.

RESULTS: The study population comprised 83,104 cows over the 2 years of the study; 75,037 (90.3%) cows calved within 10 days of their predicted calving date, 3,683 (4.4%) calved >10 days earlier, and 4,384 (5.3%) >10 days later, than predicted. Risk factors for calving >10 days before or after the predicted calving date included having >1 artificial insemination (AI) before pregnancy diagnosis (p=0.03), where the cow’s most recent AI was <21 days before the end of the herd’s AI period (p<0.01), and where the diagnosis was made at the second or third herd-visit (p<0.01). The probability of calving being >10 days later than predicted also increased when the fetus was ≥13 weeks old at pregnancy diagnosis (p<0.01).

CONCLUSIONS AND CLINICAL RELEVANCE: In this study, >90% of cows diagnosed pregnant by veterinarians using transrectal ultrasonography calved within 10 days of the predicted calving date. In herds where herd reproductive performance is high, it would be expected that more cows would conceive to their first AI, and potentially fewer cows would have AI close to the end of the herd’s AI period, which would increase diagnostic accuracy. Where herd managers rely on accurate predicted calving dates they should be informed about realistic expected accuracy. For greatest accuracy, a complete AI history should be made available to the person performing the pregnancy diagnoses and cows at most risk of having inaccurate predicted calving dates should be identified.     

Heart rate and heart rate variability in the pregnant mare and its foetus

Abortion and preterm birth of foals are major reasons for reproductive losses in the horse. Risk pregnancies require close supervision so that adequate treatment can be initiated in time. The aim of this study was to determine normal values in heart rate (HR) and heart rate variability (HRV) of the pregnant mare compared to her foetus and to detect physiological changes during ongoing gestation. In mares, the RR interval decreased from 1480±29 ms on day 270 of pregnancy to 1190±58 ms on day 330 of pregnancy (p<0.05). In contrast, foetal RR interval increased during the same time period from 611±23 ms on day 270 of gestation to 756±25 ms on day 330 of gestation (p<0.05). Concomitantly, maternal HR increased and foetal HR decreased. No further changes in RR interval occurred during the last 10 days before foaling, neither in the mare nor the foetus. In the last hours preceding parturition, maternal RR interval was lower than at all times earlier in pregnancy (average of 1037±13 ms) but did not change during this time. Maternal HRV did not change during gestation. Marked changes in HRV occurred only during the last minutes of foaling. Then, all HRV variables increased significantly (standard deviation of beat-to-beat interval: p=0.01, root mean square of successive beat-to-beat differences: p<0.01). The cardiovascular system of pregnant mares adapted to the demands of ongoing pregnancy with an increase in HR. We have no evidence that in healthy mares, pregnancy is a major stressor.     

Effect of dry period length on the effect of an intramammary teat sealant on the risk of mastitis in cattle treated with antibiotics at drying off

AIM: The aim of this study was to evaluate, under farm conditions, the use of a teat sealant in addition to whole herd dry cow antibiotic therapy on the risk of clinical mastitis in dairy cattle at pasture, and to evaluate the impact of dry period length on that risk and the impact of the teat sealant on that risk.

METHODS: Dairy cows in three herds which used routine whole herd antibiotic therapy were randomly assigned to receive either treatment with an internal teat sealant (n=322) or no additional treatment (n=313) at drying-off between March and May 2010. All clinical mastitis cases during the dry period and to the end of the subsequent lactation were recorded by farm staff; factors affecting risk of clinical mastitis were then analysed using a Cox proportional hazards model.

RESULTS: Median duration of the dry period was 112 days with >25% of cows having a dry period >130 days. The incidence risk of mastitis during lactation for cows treated with teat sealant was 9.9 (95% CI=6.9–13.7) cases per 100 cows compared with 17.9 (95% CI=13.8–22.6) cases per 100 cows for cows treated with antibiotic alone. The addition of a teat sealant to dry cow antibiotic therapy decreased the risk of clinical mastitis only in the first 33 days after calving (Hazard risk 0.24 (95% CI=0.12–0.48)). Length of dry period did not significantly affect the risk of clinical mastitis, or the effect of adding teat sealant to dry cow antibiotic therapy on the risk of clinical mastitis.

CONCLUSIONS: In these herds where, based on the mastitis history, whole herd antibiotic therapy had been recommended, the use of a teat sealant significantly reduced the risk of clinical mastitis. This effect was limited to the first 33 days after calving; subsequently there was no significant effect of treatment. There was no effect of dry period length on risk of clinical mastitis, nor any significant interaction with treatment.

CLINICAL RELEVANCE: Combination therapy with teat sealant and antibiotic was effective under New Zealand conditions in herds using whole herd antibiotic treatment at drying off. Teat sealant reduced risk of clinical mastitis in cattle with dry periods substantially longer than 100 days, and there was no evidence that this effect changed as dry period length increased.     

Factors associated with colostrum quality in individual cows from dairy herds in the Waikato region of New Zealand

AIMS: To examine associations between various cow-level factors and quality of first-milking colostrum (measured as Brix), and to evaluate herd-level associations between vaccination against calf diarrhoea and colostrum quality, in cows from dairy herds in the Waikato region of New Zealand.

METHODS: A single colostrum sample was collected, by complete udder evacuation, from each of 20 cows from 29 dairy herds in the Waikato region of New Zealand during the 2016 spring calving period. Vaccination pre-partum with a calf diarrhoea vaccine was used in 15 herds. Each colostrum sample was tested using a digital Brix refractometer. The body condition score of each cow was recorded at the time of sample collection and farmers provided records of clinical mastitis and facial eczema from the previous 12 months, as well as the age and breed of cows. Associations between cow-level variables in non-vaccinated herds and Brix were examined using a multivariable linear mixed model and estimated marginal means obtained for different categories.

RESULTS: Mean Brix of 281 samples from cows in non-vaccinated herds was 18.7 (SD 0.26)%; 63/281 (22.4%) samples had Brix ≥22% and 152/281 (54.1%) had Brix ≥18%. Mean Brix of colostrum samples from cows aged ≥6 years (20.2 (95% CI=19.1–21.2)%) was higher than for samples from 2-year-old cows (18.6 (95% CI=17.3–19.9)%) (p=0.005). Colostrum that was collected at the first milking on the day of calving had higher Brix (20.0 (95% CI=19.1–20.9)%) than colostrum collected from cows that calved the previous day (17.5 (95% CI=16.5–18.4)%) (p<0.001). Mean Brix of colostrum samples from cows which produced ≥8?L (18.2 (95% CI=17.1–19.2)%) tended to be lower than from cows which produced <8?L first-milking colostrum (19.1 (95% CI=18.3–20.0)%) (p=0.08). Among vaccinating herds, 9/15 (60%) had ≥60% colostrum samples with Brix ≥18% compared with 4/14 (29%) of non-vaccinating herds (p=0.04).

CONCLUSIONS AND CLINICAL RELEVANCE: Colostrum quality, as measured by Brix, was associated with the total volume of first-milking colostrum, interval from calving to colostrum collection and cow age. Vaccination against calf diarrhoea was associated with a higher proportion of colostrum samples with adequate Brix. Careful selection of colostrum donor cows should ensure newborn calves are fed adequate quality colostrum which should be beneficial in preventing failure of passive transfer of IgG. Testing of colostrum from individual cows with a Brix refractometer is advocated for the selection of colostrum for feeding newborn calves.     

Risk factors for post-partum anoestrus in Charolais beef cows in France

Data from 248 Charolais cows from 20 herds of the Puisaye region (Yonne, France) were collected during winter 1991–1992 to investigate risk factors affecting post-partum anoestrus. Blood was collected 60 days after calving; diagnosis of cyclicity was established by progesterone radioimmunoassay. Herd variables were housing type, lighting of herd accomodation, use of nutritional flushing and nutritional variables (protein and energy before and after calving), and individual variables were parity, ease of calving, body-condition score and body weight at calving and at Day 60, exposure to bulls and calving period. Sixty days post-partum, 62.1% of cows were cyclic. Logistic regression was used to calculate odds ratio (OR). A random effects model was used to take into account the two levels of variables (animal and herd). Although it was defined subjectively, lighting was the only significant herd-level risk factor. Odds of anoestrus were higher in dark than in light accomodation (OR = 6.2, CI 1.2–33.3). Primiparous cows had a higher anoestrus risk than multiparous cows (OR = 10.2, CI 2.9–36.5). Compared with light cows, heavy or medium weight cows at calving had a lower anoestrus risk (OR = 0.25, CI 0.07–0.91, and OR = 0.20, CI 0.07–0.61, respectively.     

Effect of puerperal mastitis in primiparous cows on milk production, cell count and culling

A retrospective cohort study was performed to investigate the effect of clinical mastitis in heifers during the first week post partum (p.p.) on subsequent health and productivity. Primiparous cows that had calved between August 15th, 1996 and August 14th, 1997 (n = 1389) were included in the study. Milk samples were collected from each quarter post partum prior to first milking. The predominant group of bacteria found were Staphylococcus spp. (69%) followed by Streptococcus spp.(12%) and E. coli (5%). Intramammary infections at calving increased the risk of clinical mastitis within the first week p.p. The cow incidence of mastitis until day 7 p. p. was 38%. Cows were classified into three groups. Group 1: Animals with clinical mastitis prior to calving (n = 35); Group 2: Animals with clinical mastitis between calving and 7 days p. p. (n = 503); Group 3: Animals without mastitis until 7 days p. p. (n = 851). Mastitis prior to parturition and mastitis within the first week p.p. increased the risk of further cases of mastitis and culling during the first 45 days of lactation. Milk yield of Group 2 was lower and somatic cell counts were higher than in Group 3.     

Effects of clinical mastitis on reproductive and milk performance of Holstein cows in Morocco

The aim of this study was to determine the influence of clinical mastitis and time of first mastitis occurrence on reproductive and milk performance of Holstein cows. Data were collected in a dairy farm from 2008 to 2012 on 1725 cows, among which 464 cows with mastitis. To determine the influence of clinical mastitis on reproductive and milk performance, models included fixed effects of parity, calving season, calving year, and group (cows with and with no mastitis). To determine the effect of time of 1st mastitis occurrence on reproductive performance, the mastitic cows group was further reclassified into three groups: prior to 60 days, between 60 and 90 days and greater than 90 days postpartum. For milk performance, the mastitic cows group was divided into two groups: before and after peak milk yield. Clinical mastitis had significant effects on calving to first AI interval, milk yield, and fat yield, but a non-significant effect on days open, number of inseminations per conception, and milk fat percentage. Mastitic cows had a calving to first AI interval 6.1 days longer and 549.6 kg milk and 20.4 kg fat per 305 days of lactation lower than those with no mastitis. Time of 1st mastitis occurrence did not have any significant effect on reproductive performance. Further, milk and fat yields of cows diseased before peak milk yield were 506 kg and 23.9 kg, respectively, lower than those of cows affected after peak milk yield. Extra attention needs to be paid to mastitis during the early postpartum period.