Relationship between duration from proestrus until predicted ovulation and changes of progesterone concentration during this time on canine litter size

Abstract

The aim of this research is to predict the number of puppies that may be born by duration of period from proestrus until POD and the change of P4 concentration during this time of medium size canines. The study was conducted when the oestrus cycles of clinically healthy medium size primiparous and multiparous canine females (n=47) at 2–7 years old were observed. Canine females were observed from first proestrus signs (FPS) till litter was born. Blood samples were collected on day 5 from the onset of discharge from the vulva until the day when the progesterone (P4) concentration rate changed till 4 ng/mL. If P4 concentration was <1 ng/mL on the day of test making, the test was repeated after 3 days; if it was 1–3 ng/mL, the test was repeated after 2 days; and if it was >3 ng/mL, the test was repeated every day until the predicted ovulation day (POD). Mating was performed 2 times with medium size breed clinically healthy 2–8 –year –old canine males, which already had offspring. The number of alive and stillbirth puppies in a litter were counted at a time when they were born. All females were divided into 3 groups by the litter size: small, medium, and large. The mean POD for females in this study was 11.36±2.17 day. [...].