Sexual activity and ovarian steroidogenic capacity of lactating and non-lactating barki ewes synchronized for estrus during seasonal anestrus under subtropical conditions

Abstract EN

This study was designed to identify the sexual activity and ovarian steroidogenic capacity of lactating ewes during periods of early and mid-lactations compared to non-lactating ewes through the anestrous season under subtropical conditions.

Occurrence of uterine involution and resumption of ovarian activity of lactating ewes (n=10) were recorded and confirmed on days 15 and 30 postpartum (PP) using ultrasonography.

Both lactating ewes (during early lactation: 40-60 days PP and mid-lactation: 70-90 days PP) and non-lactating ewes (n=10) were subjected to estrus synchronization using a double intramuscular injection of prostaglandin F2α (125 μg of cloprostenol/head), 11 days apart.

Blood samples were collected on day 2 (follicular phase) and day 9 (luteal phase) following the second PGF2α injection.

Serum concentrations of progesterone (P4), estradiol (E2) and their ratios were evaluated as well as concentrations of insulin and some blood metabolites.

Ultrasonic examinations revealed that by day 30 PP lactating ewes had mean uterine horn diameters and ovarian structures in line to those of non-lactating ewes.

During the experimental period, regardless of the physiological status (lactating or non-lactating) most females failed (P>0.05) to exert signs of estrus (100% in early lactation, 80% in mid-lactation and 60% in non-lactating ewes).

However, 70% of the ewes in early lactation, 70% of the ewes in mid-lactation and 100% of the non-lactating ewes had corpora lutea (CLs) in the luteal phase of the synchronized estrus.

Concentrations of P4 and E2 and P4/E2 ratios did not significantly differ between both follicular and luteal phases of the synchronized estrous cycles either in lactating (early lactation or mid-lactation) or non-lactating ewes.

Lactating ewes in both early and mid-lactation periods had lower (P<0.05) concentrations of circulating blood glucose, triglycerides, total protein and albumin compared with non-lactating ewes.

Also, the lowest (P < 0.05) overall means of P4 and E2 concentrations were recorded for ewes in mid-lactation, followed by ewes in early lactation and non-lactating ewes.

Concentrations of serum P4 and E2 were positively correlated (P < 0.05) with each of body weight (r = 0.3 for both correlations), concentrations of serum glucose (r = 0.3, P < 0.05 and r = 0.4, P < 0.01; respectively) and concentrations of serum triglycerides (r = 0.4, P < 0.05 and r = 0.6, P < 0.01; respectively).

Results of the present study revealed that both lactating and non-lactating ewes during seasonal anestrus displayed similar pattern of sexual activity and hormonal disturbances as reflected by unchanged P4/E2 ratios on day 2 (follicular phase) and day 9 (luteal phase) of the synchronized estrous cycle, suggesting presence of a persistent corpus luteum in a high proportion of females.

This ovarian dysfunction seems to be related to seasonal effects more likely than lactational effects.

However, lactation presents an additional load on the reproductive functions by inducing symptoms of negative energy balance (lower body weight and poorer metabolic status).