Reproductive performance of Thoroughbred mares in the Waikato region of New Zealand: 2. Multivariable analyses and sources of variation at the mare,stallion and stud farm level

Abstract

AIM: The objective of this study was to utilise multivariable statistical methods appropriate for clustered data to identify mare-related explanatory variables that significantly affected the reproductive performance of Thoroughbred mares in the Waikato region of New Zealand. In addition, we aimed to determine the relative contribution of the mare, stallion and stud farm to reproductive performance.

METHODS: A prospective cohort study was performed involving five stud farms in the Waikato region of New Zealand during three consecutive breeding seasons (2006–2008). A total of 1,482 individual mares contributed 2007 mare years and 3,402 oestrous cycles over the three breeding seasons. Reproductive performance was measured using three parameters; (a) first-cycle pregnancy rate (FCPR), (b) end-of-season pregnancy rate (SPR), and (c) the start-of-mating to conception interval.

RESULTS: When controlled for the effects of serving stallion, stud farm and year of study the only significant mare-related variables included in the final models of FCPR, SPR and conception interval were the age of the mare and her reproductive status (classified as dry or foaling). Advancing mare age significantly reduced reproductive performance regardless of reproductive status and foaling mares had significantly poorer reproductive outcomes compared with dry mares when controlled for age. For each additional increase in year of age, the FCPR was reduced by a factor of 0.94 (95% CI=0.92–0.96) and the SPR was reduced by a factor of 0.91 (95% CI=0.88–0.93). Mares older than 14 years of age took longer to conceive after the start-of-mating compared with younger mares. The daily hazard of conception for mares 14 years and older was 0.64 (95% CI=0.47–0.83) times less than mares younger than 9 years of age. Determining the relative contribution of the mare, stallion and stud farm to the FCPR indicated that 95.9% of the variation was at the mare level, 4.1% was at the stallion level and 0% was at the stud farm level. For the SPR the variance components indicated that 92.5% of the variation was at the mare level, 6.7% was at the stallion level and 0.8% was at the stud farm level.

CONCLUSIONS: The reproductive performance of Thoroughbred mares in the Waikato region of New Zealand is influenced by two main mare-related factors; the age of the mare and her reproductive status (dry or foaling). The majority of variation in reproductive performance was associated with mare-level factors and the contribution of the stallion and stud farm was relatively minor.     

Viruses associated with outbreaks of equine respiratory disease in New Zealand

AIM: To identify viruses associated with respiratory disease in young horses in New Zealand.

METHODS: Nasal swabs and blood samples were collected from 45 foals or horses from five separate outbreaks of respiratory disease that occurred in New Zealand in 1996, and from 37 yearlings at the time of the annual yearling sales in January that same year. Virus isolation from nasal swabs and peripheral blood leukocytes (PBL) was undertaken and serum samples were tested for antibodies against equine herpesviruses (EHV-1, EHV-2, EHV-4 and EHV-5), equine rhinitis-A virus (ERAV), equine rhinitis-B virus (ERBV), equine adenovirus 1 (EAdV-1), equine arteritis virus (EAV), reovirus 3 and parainfluenza virus type 3 (PIV3).

RESULTS: Viruses were isolated from 24/94 (26%) nasal swab samples and from 77/80 (96%) PBL samples collected from both healthy horses and horses showing clinical signs of respiratory disease. All isolates were identified as EHV-2, EHV-4, EHV-5 or untyped EHV. Of the horses and foals tested, 59/82 (72%) were positive for EHV-1 and/or EHV-4 serum neutralising (SN) antibody on at least one sampling occasion, 52/82 (63%) for EHV-1-specific antibody tested by enzyme-linked immunosorbent assay (ELISA), 10/80 (13%) for ERAV SN antibody, 60/80 (75%) for ERBV SN antibody, and 42/80 (53%) for haemagglutination inhibition (HI) antibody to EAdV-1. None of the 64 serum samples tested were positive for antibodies to EAV, reovirus 3 or PIV3. Evidence of infection with all viruses tested was detected in both healthy horses and in horses showing clinical signs of respiratory disease. Recent EHV-2 infection was associated with the development of signs of respiratory disease among yearlings [relative risk (RR)=2.67, 95% CI=1.59-4.47, p=0.017].

CONCLUSIONS: Of the equine respiratory viruses detected in horses in New Zealand during this study, EHV-2 was most likely to be associated with respiratory disease. However, factors other than viral infection are probably important in the development of clinical signs of disease.     

Mandibular and sublingual sialocoeles in the dog: A retrospective evaluation of 41 cases,using the ventral approach for treatment

AIMS: To review results of the ventral approach for mandibular and sublingual sialoadenectomy for the treatment of sialocoeles associated with the mandibular and sublingual salivary glands in the dog, and to determine rates of recurrence and complication following this procedure.

METHODS: Thirty-nine dogs with 41 sialocoeles that underwent surgical intervention were retrospectively evaluated with respect to signalment, aetiology, location of sialocoeles, duration of clinical signs, treatment prior to referral, post-operative use of antibiotics and drains, complications, and recurrence.

RESULTS: The mean age at the time of surgery was 5.1 (SD 3.8) years, and duration of clinical signs 6.6 (SD 10.6) months. Long-term follow-up was available for 31 dogs; the minimum was 8 months and mean 47.7 (SD 25.8) months post-surgery. There was no recurrence of sialocoeles following the ventral approach for mandibular and sublingual sialoadenectomy. Post- operatively, 6/35 (17%) cases developed a seroma at the surgical site. No breed or sex predisposition was determined. The cause of the sialocoele was unknown in 36/41 (88%) cases.

CONCLUSIONS AND CLINICAL RELEVANCE: Excellent clinical results were achieved with a low rate of complications using the ventral approach for mandibular and sublingual siaload- enectomy. The ventral approach is recommended to minimise the risk of recurrence of sialocoeles.     

Influence of the FecXR Allele in Heterozygous Ewes on Follicular Population and Outcomes of IVP and ET using LOPU‐Derived Oocytes

Ewes heterozygous for the FecX^R allele (R+) in the bone morphogenetic protein 15 (BMP15) gene display increased ovulation rate and prolificacy. Besides this phenotypic advantage, the influence of the FecX^R allele on follicle number and size, oocyte competence and in vitro production (IVP) remains undefined. With these aims, 8 R+ and 8 wild‐type (++) ewes were subjected to 2 laparoscopic ovum pick‐up (LOPU) trials (four sessions per trial; two with and two without FSH) and subsequent IVP and fresh embryo transfer. All follicles >3 mm were punctured (n = 1673). Genotype did not significantly affect the number of punctured follicles per ewe and session (10.4 and 10.2 in R+ and ++ untreated ewes, 17.4 and 14.3 in R+ and ++ FSH‐treated ewes, respectively), but follicular diameter of R+ ewes was significantly reduced compared with ++ ewes (?0.2 mm in untreated and ?0.8 mm in FSH‐treated ewes; p < 0.01). R+ ewes showed higher recovery rate and increased numbers of total and suitable cumulus–oocyte complexes for in vitro maturation (IVM). Similar rates of day 8 blastocysts were observed in R+ (36.1%, 147/407) and ++ (32.6%, 100/307) ewes, but the final output of day 8 blastocysts per ewe and session was higher in R+ ewes (+0.75; p < 0.005), without differences in survival rate at birth of the transferred embryos (40.4%, 21/52 vs 36.4%, 16/44, respectively). In conclusion, a higher number of oocytes proven to be competent for in vitro development and embryo survival after transfer are recovered from R+ ewes, despite the lower mean size of their follicles at puncture.     

24-Hour Secretion Patterns of Plasma Oestradiol 17β in Pony Mares in Late Gestation

The mare exhibits nocturnal uterine contractions in the last 6 days of gestation. It is hypothesized that estradiol 17β (O17β) may be associated with the nightly increase in uterine contractions. The 24‐h secretion pattern of plasma O17β was measured in 3 pony mares in late gestation to identify changes in release as the mare neared parturition. Blood was collected weekly at 08:00 hours beginning on day 240 and every third day from day 330 until delivery. Serial blood samples were collected from each mare every 30‐min for 24‐h beginning on gestation day 310 and every sixth day thereafter until parturition. Concentrations of O17β were elevated at night with lowest concentrations occurring directly before sunset (p < 0.01). The natural log of the variance was increased at sunset (p < 0.01) and was decreased during the 6‐h period immediately after sunrise. This pattern was especially evident in the 6 days that preceded parturition. The contrast between nocturnal and daytime concentrations of O17β in the last 6 days of gestation may contribute to night‐time delivery in the mare.     

Chitin utilisation by broilers and its effect on body composition and blood metabolites

1. Little is known about the ability of farmed poultry to digest chitin and derive nutrients from the ingestion of insects. 2. Commercial chitin derived from crustacean shell waste was found to contain 373 g crude protein, 265 g ash, 23.5 g ether extract, 130 g calcium and 16.4 g phosphorus per kg, on an air-dry basis. 3. It was included in diets at 0, 25, 50 and 75 g chitin per kg and fed to 320 1-d-old broiler males, over a 21-d period. There were no statistically significant treatment effects on weight gain or feed efficiency. Apparent digestibility of chitin protein was 0.48, 0.50 and 0.45, at the 25, 50 and 75 g per kg inclusions, respectively. Mean AME and AMEN values of chitin were determined as 8.97 and 8.86 MJ/kg. 4. In a subsequent study, mean TME and TMEN values of chitin were determined to be 8.23 and 8.21 MJ per kg, respectively. Addition of chitinase to the diet increased TME and TMEN of chitin to 8.81 and 8.79 MJ per kg, respectively (P<0.05). True digestibility of chitin protein was determined to be 0.87. 5. Triglyceride concentrations in liver and breast meat were significantly reduced by chitin inclusion. No significant differences in carcase yield at 21 d of age were found. Serum cholesterol and triglycerol concentrations were reduced significantly by dietary chitin, the lowest levels being observed at the 50 g per kg inclusion level. 6. These findings indicate the ability of modern poultry to digest chitin but suggest that the ingestion of insects is not an important source of nutrients, at least from the exoskeleton.     

Intramolecular carbon isotopic composition of monosodium glutamate: biochemical pathways and product source identification

Monosodium glutamate (MSG) obtained as trade samples from several manufacturers was studied to determine the range of its intramolecular 13C/12C composition. Although the carbon isotopic composition of the total MSG molecule did not differ among manufacturers in most instances, significant differences were observed in the isotopic composition of the alpha-carboxyl carbon, suggesting that different proprietary strains of industrial microorganisms or MSG purification methods may impart unique isotopic fingerprints upon their products. The 13C depletion of the alpha-carboxyl carbon relative to the rest of the molecule helps constrain the identity of the potential anapleurotic carboxylating enzymes responsible for its fixation.