engleski

Quick prepartal hormonal overturn in young primiparous Labrador retriever bitches: from high level of serum progesterone today to the healthy litter tomorrow

Routine quantitative serum progesterone (P4) assay is the most common method to estimate the date of ovulation and consequently the whelping date, which is 63±1 days after ovulation (1, 2). Whelping is a result of hormonal changes, including a final drop in a P4 values, which sharply decreases from 4-5 ng/ml to below 2 ng/ml starting 24 hours before the onset of whelping (1). When P4 is validated on a daily basis, it is important to have in mind fluctuations in progesterone level during the day, depending on a rhythmic secretion of this hormone (3). Serum progesterone level was measured in total of 17 Labrador retriever bitches in a late pregnancy starting from 58 days post ovulation. Blood samples were taken daily, at the same time. Enzyme-linked fluorescent assay (ELFA) was used to estimate a serum progesterone level. Retrogradely, the data from last 72 hrs was taken. According to a different rate of decrease, values were divided into two groups: rapid decrease (range between P4 values in last 72 hrs were 4, 15±1, 03 ng/ml) and gradual (slow) decrease (range were 1, 54±0, 54 ng/ml). Rapid decrease in P4 values was recorded in 41.2% and gradual rate decrease in 58, 8% of the bitches. Variations in changes of P4 level can be related to the age of the bitches. In the group with rapid decrease (n=7) mean age was 2±0.65 yrs and in the group with gradual decrease (n=10) was 3, 3±1, 73 yrs. Primiparous bitches were 47, 1% of the all bitches and 62, 5% of them had a rapid drop in P4 values. Consequently, percentage of the primiparous bitches in a group with a rapid decrease were 71.4% and in a group with gradual decrease were 30%. The size of a litter and the number of healthy puppies per litter doesn't seem to affect the rate of P4 decrease. Both groups had similar total number of the puppies (6, 6±2 and 7, 2±3 puppies for rapid and gradual P4 decrease) and the number of the healthy puppies (6, 1±1, 5 and 5, 1±3, 1 for rapid and gradual decrease). However, the number of the dead puppies per litter could be related to a rate of P4 decrease. Of all the newborn puppies 20, 3% were dead, 6, 5% in rapid decrease and 29, 2% gradual decrease group, respectively. Dystocia was present in 35, 3% of the all bitches, 28, 6% in group with rapid decrease and in 40% in group with gradual decrease, respectively. According to these findings, a rate of prepartum decrease in P4 level can differ greatly between bitches, which disables prediction of a precise time of whelping. Rapid decrease of P4 level can be expected in a young primiparous bitches. This quick hormonal turnover can be related to the stress of the first whelping, fast metabolism in a young animal and also can be a predictor of the healthy litter.

Progesterone, bitch, whelping

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