Luteal phase decrease in packed cell volume in healthy non-pregnant and pregnant bitches.

OBJECTIVES: To establish packed cell volume (PCV) ranges for non-pregnant, pregnant and post-partum bitches from day 10 of proestrus, investigating any relationship with parity and litter size. METHODS: This prospective cohort study used 37 healthy breeding bitches to examine PCV counts from routine blood samples collected every 4 weeks, from day 10 of proestrus, as part of routine PCV monitoring. RESULTS: For pregnant (n = 19) and non-pregnant (n = 18) bitches, PCV decreased until week 8 (corresponding to 8.5 ± 1.1 days before whelping for pregnant bitches) and recovered by 16-20 weeks after the initial sample; bitches that whelped average and large litters showed greater declines. PCV began to recover sooner for bitches that had previously whelped one or two litters compared to bitches that had previously whelped three or more litters. There was a significant three-way interaction between time after the onset of proestrus, litter size and the number of previous litters which demonstrated that the large decrease in PCV for bitches that had previously whelped three or more litters only occurred in bitches that were expecting an average or large sized litter. CLINICAL SIGNIFICANCE: Chronological variation in PCV for pregnant and non-pregnant bitches was established during the reproductive cycle. There was no evidence to suggest that routine PCV measurement for normal, healthy bitches would be beneficial. However, knowledge from this study may be useful when deciding whether to prospectively monitor a bitch where there is a history of previous pregnancy-related anaemia, when performing a caesarean section due to the anticipated blood loss during surgery, or when examining blood profiles for post-litter bitches.

A Prospective Cohort Study Investigating the Impact of Neutering Bitches Prepubertally or Post-Pubertally on Physical Development.

No previous large prospective cohort studies have been identified that have investigated the impact of the surgical neutering of bitches before or after known puberty on their growth and physical development. This study was designed to examine the data on physical development, vulval size, and conformation for bitches neutered by ovariohysterectomy before puberty (PPN, n = 155) or after puberty (control, n = 151) using a prospective cohort study design. Data were gathered at six- and 17-months of age using bespoke physical assessment forms and digital images of the vulva. PPN bitches had greater changes in height measurements (mean difference = 2.039, SEM = 0.334, 91% CI = 1.471 to 2.608, p < 0.001) and smaller changes in the measurements of vulval length (mean difference = -0.377, SEM = 0.079, 91% CI = -0.511 to -0.243, p < 0.001) and width (mean difference = -0.221, SEM = 0.063, 91% CI = -0.328 to -0.113, p < 0.001) between six- and 17-months of age than for the control bitches. Although not significant, the PPN bitches were taller (mean 58.5 vs. 56.6 cm) and heavier (mean 28.3 vs. 27.3 kg) with smaller vulval size measurements (mean vulval length 2.8 vs. 3.2 cm, mean vulval width 1.7 vs. 2.1 cm) at 17-months of age. At 17-months of age, significantly more PPN bitches had vulvas that appeared juvenile (Yates' Chi-square = 14.834, D.F. = 1, p < 0.001) and recessed (Yates' Chi-square = 7.792, D.F. = 1, p = 0.005) at the physical assessment, and significantly more PPN bitches had vulvas that appeared 'recessed/inverted' on the examination of digital images (Chi-square = 9.902, D.F. = 1, p = 0.002). The results from this study suggest no contraindications to prepubertal ovariohysterectomy for large breed bitches. However, any longer-term health implications of these differences in physical development need to be investigated and better understood prior to recommendations being made.

Effect of neutering timing in relation to puberty on female dog behaviour-A scoping review.

BACKGROUND: There are contradictory findings in the literature relating to the effects of timing of neutering on bitch behaviour that make decision making regarding neutering timing difficult. METHODS: A scoping review was designed to identify and chart the evidence on the effect of neutering timing in relation to puberty on the behaviour of female domesticated dogs. A protocol was registered, and literature searches were conducted in CAB Abstracts, Medline and Web of Science. Studies were reviewed against the inclusion criteria. Data on study and population characteristics and behavioural outcomes were extracted for the final included studies. RESULTS: A total of 1048 publications were reviewed; 13 were retained for inclusion and charting. Only one of the two studies that classified bitches as pre- or postpubertal presented results for the analysis of behaviours. The remaining 11 studies classified bitches by age at neutering. LIMITATIONS: Since the scoping review searches were conducted, further relevant studies may have become available. The search strategy may not have identified all available literature; however, databases were used that provide high levels of coverage of veterinary literature. CONCLUSION: This scoping review identified a lack of evidence to document the impact of neutering bitches before or after puberty on behaviour.

A prospective cohort study investigating the peri- and postoperative outcomes following ovariohysterectomy in bitches neutered prepubertally or post-pubertally.

The aim of this prospective cohort study was to investigate perioperative and postoperative outcomes for bitches that were neutered at different times in relation to puberty (rather than age). Three hundred and six Labrador and Golden Retriever crossbreed bitches were neutered before (prepubertal neuter [PPN], n = 155) or after puberty (Control, n = 151) by experienced veterinarians at one of four veterinary practices (VP1-4). Data were gathered from veterinarians at the time of neutering and from bitch caregivers for the 14-day period after neutering using purpose-designed questionnaires. PPN bitches had shorter surgery durations than Control bitches (OR = 0.877, 91% CI = 0.800 to 0.961, P = 0.015). Longer surgery durations were reported for bitches that had intraoperative complications (OR = 1.620, 91% CI = 1.397 to 1.879, P < 0.001). Shorter surgery durations were reported for VP1 compared to all other veterinary practices (OR = 1.189 to 1.534, P < 0.001). There was no difference in the number of PPN or Control bitches that had perioperative complications (PPN: 3.9%, n = 6; Control: 7.7%, n = 11) and no bitch had more than one perioperative complication reported. For the 14-day postoperative period, fewer PPN (1.3%, n = 2) compared to Control bitches (8.9%, n = 13) had wound discharge (Chi-square = 11.151, D.F = 1, P = 0.001) or showed inappetence (PPN: 2.9%, n = 4; Control: 17.3%, n = 19, Chi-square = 14.884, D.F. = 1, P < 0.001). There was no difference in the number of PPN and Control bitches that had redness or swelling of the wound (52 PPN, 48 Control), showed attention to the wound (6 PPN, 6 Control), required veterinary attention (25 PPN, 23 Control), or that showed any other unusual behaviours: discomfort (27 PPN, 16 Control), uncharacteristic irritability (2 PPN, 4 Control), or uncharacteristic licking or chewing of parts of the body (15 PPN, 6 Control). Bitches neutered at VP2-4 were more likely to have wound redness or swelling reported than those neutered at VP1 (OR = 3.109 to 4.076, P = 0.003). Future studies should consider the impact of veterinary practice on results. These results for peri and postoperative complications could suggest that prepubertal ovariohysterectomy may be a suitable option for neutering bitches. However, it is recommended that they be interpreted together with evidence relating to the impacts on other factors including behaviour and longer-term health in order to make fully informed decisions.

A Prospective Cohort Study Investigating the Behavioural Development of Bitches in a Guide Dog Training Programme Neutered Prepubertally or Post-Pubertally.

There are few studies that investigate the effect of neutering bitches before or after puberty. The majority of current literature examining the impact of the timing of neutering on health and behaviour has used age rather than the onset of puberty as the key variable. The aim of this prospective cohort study was to investigate the effects of timing of neutering in relation to puberty on behaviour in female dogs reared and trained in an assistance dog programme. The study examined data for bitches neutered before or after puberty to compare scores for six behavioural factors (training and obedience, aggression, fear and anxiety, excitability, attachment and attention-seeking, and social behaviour) measured at 1 and 3 years of age. Labrador and Golden Retriever crossbreed bitches were neutered before (n = 155) or after (n = 151) puberty. Neutering before or after puberty had no impact on mean scores for the six behavioural factors at 1 or 3 years of age. When examining the change in behavioural factor scores between 1 and 3 years of age, only aggression behavioural factor scores were influenced by neutering before or after puberty. Bitches neutered after puberty were less likely to have aggression factor scores that increased between 1 and 3 years of age (OR = 0.959, 90% CI = 0.924 to 0.995, p = 0.06). However, the majority of bitches scored "0" for aggression at both time points (indicating no aggression behaviours were observed), and the number of bitches for which scores increased between 1 and 3 years of age was low (before puberty = 20, after puberty = 9). This is consistent with very mild aggressive behaviours being observed in a small number of animals and is, therefore, of questionable concern. The results suggest that, for Labrador and Golden Retriever crossbreed bitches, neutering before or after puberty has little to no effect on future behaviour. It is recommended that decisions about the timing of neutering are not informed solely by impacts on behaviour, but that they also consider evidence relating to the impacts on bitch health and well-being.

Incidence and risk factors for canine mastitis and metritis in two guide dog populations.

Canine mastitis and metritis can cause severe illness but the incidence and risk factors have not been well-studied. Goals in the present study were: 1) report the incidence of mastitis and metritis in a large population, and 2) identify potential risk factors that predispose females to those diseases. A retrospective cohort study was conducted using data from two guide dog colonies that was collected for 17 and 10 years, respectively, for the two colonies. A total of 3076 whelpings occurred during the respective study periods and data were analyzed. Clinical mastitis was diagnosed in 13.2 % of whelpings (408 cases) with the average day of diagnosis being 16.7 postpartum. Risk factors for mastitis identified were colony, litter size where bitches that had large litter size of ≥9 pups (16.2 %) were 60 % more likely to develop mastitis compared with bitches that had litters of <9 pups (11.3 %). Bitches with congestion of the mammary gland were 4.8 times more likely to develop mastitis compared with bitches without mammary congestion. Case incidence of metritis was small (0.7 % of whelpings) and occurred on average at day-5 postpartum (range 1-16). There were no significant risk factors identified, and this may be due to the small number of metritis cases (22 cases) in the present study. Interpretations regarding metritis, therefore, should be made with caution. The results from this study provide parameters for breeders and veterinarians to identify bitches that may require close monitoring for mastitis and metritis.

Identifying risk factors for canine dystocia and stillbirths.

Canine dystocia is a common problem that increases the risk of mortality to the dam and stillbirths for the pups. Understanding the risk factors for dystocia and stillbirth can help guide decision making to improve outcomes of whelping management. This study aimed to 1) evaluate risk factors for canine dystocia; and 2) assess risk factors for stillbirth in puppies, by examining all whelpings and puppies born in two breeding populations of guide dogs for a defined period of time. Dystocia risk factors were evaluated using a repeated measures model on 2,489 litters with an overall dystocia rate of 23.8%. Risk factors identified for dystocia were colony, litter size, and age of dam. Small litter size (<5 pups) had the highest dystocia rate of 36.5%, large litter size (>9 pups) had an intermediate dystocia rate of 26.9% and medium litter size had the lowest dystocia rate of 22.1%. Dystocia risk increased as the age of dam increased. Stillbirth risk factors were evaluated for 19,577 pups and the overall stillbirth rate was 5.9%. Risk factors identified for stillbirths were dystocia, litter size, cesarean section performed and breed. Pups from litters that had dystocia were 2.35 times more likely to be stillborn compared with normal litters born without dystocia. Stillbirth risk increased as litter size increased. Pups from litters of 11 or more pups were 1.45 times more likely to be stillborn. Specific information was available for a subset of pups and was used to evaluate the association with stillbirth. Low birth weight was associated with increased stillbirth risk but large pups were also at higher risk of stillbirth compared with average size pups. Stillborn pups had longer mean (102 vs 65 min) and median (47 and 32 min) inter-pup intervals compared with live pups. The positive predictive values for stillbirth were 13.5%, 28.4%, 31.8% and 36.5% when inter-pup interval threshold was set at 1, 2, 3 and 4 h respectively. There is a tradeoff between over diagnosing stillbirth and increased positive predictive value for stillbirth when inter-pup interval threshold is extended but the improvements were modest after 2 h. The last pup born in a litter regardless of litter size was significantly more likely to be stillborn. In conclusion, this paper details data driven parameters to use when making the decision to intervene during whelping that optimize survival for dams and puppies.

Seasonality in oestrus and litter size in an assistance dog breeding colony in the United Kingdom.

Evidence of seasonality in oestrus in bitches within specialist breeding programmes, such as those for assistance dogs, may support colony management through tailoring the distribution of resources required for breeding throughout the year. However, at present there are conflicting data regarding seasonality in oestrus (and litter size) in domestic dogs. The primary objective of this study was to investigate seasonal variations in oestrus and litter size in a large assistance dog breeding colony in the UK in order to optimise colony management. The authors analysed the annual distribution of 3624 observations of oestrus collected from 568 brood bitches from January 2005 to June 2014. The authors also evaluated the relationship between month and litter size for 1609 litters observed during the same period. There was no evidence of regular seasonal variations in oestrus or litter size by meteorological season or month. The lack of seasonality in oestrus may be a function of dogs in the UK, particularly valuable breeding bitches, being exposed to fairly constant environmental conditions throughout the year as a consequence of artificial light and heating during the winter months. The authors' findings suggest that special consideration of the annual distribution of oestrus and litter size is unnecessary for the management of assistance dog breeding colonies similar to those in the UK.

Environmental chemicals impact dog semen quality in vitro and may be associated with a temporal decline in sperm motility and increased cryptorchidism.

Adverse temporal trends in human semen quality and cryptorchidism in infants have been associated with exposure to environmental chemicals (ECs) during development. Here we report that a population of breeding dogs exhibit a 26 year (1988-2014) decline in sperm quality and a concurrent increased incidence of cryptorchidism in male offspring (1995-2014). A decline in the number of males born relative to the number of females was also observed. ECs, including diethylhexyl phthalate (DEHP) and polychlorinated biphenyl 153 (PCB153), were detected in adult dog testes and commercial dog foods at concentrations reported to perturb reproductive function in other species. Testicular concentrations of DEHP and PCB153 perturbed sperm viability, motility and DNA integrity in vitro but did not affect LH stimulated testosterone secretion from adult testis explants. The direct effects of chemicals on sperm may therefore contribute to the decline in canine semen quality that parallels that reported in the human.

Prevalence of ultrasound-determined cystic endometrial hyperplasia and the relationship with age in dogs.

To investigate the potential relationship between age and diagnosis of cystic endometrial hyperplasia (CEH) in the bitches, 348 ultrasound examinations from 240 bitches (Labradors, Golden Retrievers, German Shepherds, Flat Coated Retrievers, or crosses of those breeds aged between 1.6 and 7.2 years at examination) were examined. A subpopulation of 32 bitches that had completed their breeding careers at 6 years or more of age was also identified. Of all, 18.3% of the bitches were diagnosed with CEH; these cases were newly diagnosed when bitches were between 2.5 years and 7.3 years of age. The proportion of ultrasound examinations in which CEH was identified increased from 6.8% of examinations on 2-year-old breeding bitches to 60.0% of examinations on 6-year-old bitches. Logistic regression identified a positive correlation between mean age at the examination and presence of CEH (χ(2) = 30.74, degrees of freedom = 1, P < 0.001). For 32 bitches that had completed their breeding career, the prevalence of CEH was 56.3%, age at the diagnosis ranged from 3.8 to 7.3 years, and the proportion of bitches affected with CEH increased from 6.3% at 3 years of age to 56.3% at 7 years of age. These data support the contention that the prevalence of CEH increases with age.

Digital image analysis of testicular and prostatic ultrasonographic echogencity and heterogeneity in dogs and the relation to semen quality.

A semi-automated ultrasonographic method was developed to measure echogenicity and heterogeneity of the testes and prostate gland and relationships of these measures with semen quality were assessed in 43 fertile dogs. The relationship between animal age and body weight upon the volume of the testes, epididymal tail volume and prostate volume were also established. Mean testicular echogenicity was negatively correlated with the percentage of morphologically normal live spermatozoa (more echogenic testes were associated with fewer normal sperm) but not with any other semen quality measure. Mean testicular heterogeneity was positively correlated with the total spermatozoal output (more heterogenous testes, being those with anechoic parenchyma and prominent echogenic stippling, were associated with greater sperm output) but not with any other semen quality measure. There was no relationship between either mean prostatic echogenicity or mean prostatic heterogeneity and any semen quality measure. There was no relationship between age and any testicular or prostatic parameter; however bodyweight was significantly correlated with total testicular volume, total epididymal tail volume and total prostatic volume. Testicular and prostatic ultrasonographic echogenicity and heterogeneity can be objectively assessed using digital image analysis and testicular echogenicity and heterogeneity may be useful adjunct measurements in a breeding soundness examination.