PREDICTION OF WHELPING DATE IN JACK RUSSELL TERRIER

Predicting whelping date is essential to be ready to provide help in case of dystocia, and Jack Russell Terrier have been identified as the fourth breed most frequently presented in emergency for dystocia in the UK [1]. The main purposes of this scientific paper were: 1) to develop breed-specific formulas to predict the days before parturition (dbp) in Jack Russell Terrier bitches based on inner chorionic cavity (ICC) diameters and biparietal (BP) diameters; 2) to evaluate the accuracy of these formulas and the accuracy of estimated ovulation date in predicting parturition date. Ultrasound examinations of 22 pregnancies of 15 bitches were included in this retrospective study: 19 pregnancies for ICC group and 17 for BP group. Only physiological pregnancies were included, single puppy pregnancies were excluded and multiple images for each conceptus were taken. The ultrasound examinations were performed between September 2018 and December 2022. ICC diameters were measured from 21 to 27 days post-ovulation, while BP diameters were measured from 39 to 47 days post-ovulation. Ovulation date was estimated through serum progesterone concentration (considering 4.01–8.0 ng/ml as the day of ovulation) [2] and confirmed by ovarian ultrasonography [3]. The parturition date and the number of puppies delivered were recorded. For ICC group, the correlation showed a weak relationship with litter size (rho=-0.17) and this was not included in the simple linear regression. The latter (dbp=44.983-0.6352*ICC) was statistically significant (P<0.001, r2=77.58). For BP group, the correlation of dbp with litter size was moderate (rho=-0.49) and this was included in the regression (dbp=49.40-1.228*BP-0.546*number of fetuses; P<0.001, r2=90.85). Effect of BP (P<0.001) and number of fetuses (P=0.006) was significant. Accuracy for single parameters of ovulation date, ICC and BP was 71.4%, 78.6% and 85.7% with an error of ±1 day, and 85.7%, 100% and 100% with an error of ±2 days, respectively. When considering all these parameters together, the accuracy was not increased compared to that of the BP formula (85.7% at ±1 days and 100% at ±2 days). BP diameter taken within the sixth week of pregnancy was the best morphometric parameter in predicting whelping date, when corrected by the number of fetuses, as already described. In conclusion, to improve the prediction of the parturition date in Jack Russell Terriers, a re-evaluation of pregnancy at the 6th-7th week of pregnancy is indicated.