Effects of Ram Introduction After the Second Prostaglandin F_2α Injection on Day 11 on the LH Surge Characteristics in Fat‐Tailed Ewes

Abstract

The aim of this study was to evaluate the effects of ram introduction after the second prostaglandin F2alpha (PG F2alpha) injection on day 11 on the secretion characteristics of pre-ovulatory LH surge of fat-tailed ewes. Multiparous Morkaraman ewes (n=12) were divided into three groups by balancing the groups for liveweight (BW) and body condition score (BCS). On the day of second PGF2 alpha injection (0 h), performance tested rams (n=2) were either introduced to the ewes at 0 h (ram 0 group, n=4) or at 18 h (ram 18 group, n=4) or were not introduced (control group, n=4). Blood samples were collected at 6, 18, 42, 48, 56, 62, 66, 70, 74, 78 and 90 h for the determination of pre-ovulatory LH surge. BCS and BW during the experimental period were 2.2 +/- 0.2 units and 50.9 +/- 2.3 kg, 2.4 +/- 0.4 units and 49.2 +/- 6.2 kg, 2.1 +/- 0.3 units and 45.9 +/- 4.4 kg, respectively for the ram 0, ram 18 and control groups (p > 0.05). No significant difference was observed in LH surge characteristics for the experimental groups. Peak LH concentrations were also not different between groups (p > 0.05) and they were 12.2 +/- 8.3, 29.1 +/- 9.9 and 15.8 +/- 9.5 microg/l for the ram 0, ram 18 and control groups, respectively. There was, however, a significant correlation between peak LH concentrations and BCS (p < 0.05, R2=0.373). In conclusion, it appears that, compared with ram introduction, variability in body condition of the ewe has much pronounced effect on the amount of LH secreted after the usage of two PGF2 alpha injections (11 days apart) as a tool for oestrus synchronization.

Effects of Sexually Activated Rams or Ewes on Pulsatile LH Secretion in Anoestrous Sheep

“…It has been reported that BCS is positively correlated to timing of LH surge in sheep (Yildiz et al 2002b) and LH pulse frequencies in sheep (Robinson 1990) and cattle (Yildiz et al 1997). The link between BCS and hypothalamus, where GnRH secretion is initiated, appear to include leptin secretion from the adipose tissue (Blache et al 2000;Yildiz et al 2001) since leptin informs the hypothalamus about the sufficiency of energy stores for the initiation of reproductive activity (Blache et al 2000).…”

“…A sensitive competitive enzyme immunoassay method developed by Mutayoba et al (1990) for bovine LH and modified by Yildiz et al (2002b) was used to analyse LH concentrations. Briefly, D-Biotinyl-ε-aminocaproic acid N-hydroxy-succimidine ester (Biotin-X-NHS, SIGMA, Germany) was used for labelling oLH (NIDDK-oLH-I-4 (AFP-8614B)).…”

“…Photoperiod, nutrition, body energy reserves and social interactions are among the factors that affect the reproductive activity of the sheep (Adam and Robinson 1994;Yildiz et al 2001;Yildiz et al 2002a and2002b). In spite of the difficulties in managing photoperiod, nutrition and body energy reserves, social manipulation of the reproductive activity in farm animals emerges as a good alternative, especially, to reproductive management techniques that facilitate application of reproductive hormones (Rekwot et al 2001).…”

A Comparative Study of Induction of Estrus and Ovulation by Three Different Intravaginal Devices in Ewes during the Non-Breeding Season

“…The attempted methods are control of daily length and/ o r h o r m o n a l t r e a t m e n t s s u c h a s n a t u r a l p r o g e st e r o n e , s y n t h e t i c p r o g e s t o g e n s , prostaglandin F2α (PGF2α) or gonadotrophin releasing hormone (GnRH), and isolated ram introduction [3]. Recently, a method using PGF2α combined with GnRH was reported in ewes with a successful lambing rate after natural mating or artificial insemination [1,4]. Treatment with GnRH and PGF 2α is a practical method for controlling ovarian follicular and luteal functions and for increasing the precision of estrus synchronization in cyclic and acyclic postpartum cows and heifers [5][6][7][8].…”

Onset of reproductive activity of white and natural colored corriedale ewe lambs

“…This may be due to the observed depletion of body reserves (Table 2) and weight loss (Figure 3), because of the low nutritional value of the herbage, which could have interrupted the sexual activity. The body condition score is positively related with the presence of a peak and pulsatile behavior of the luteinizing hormone in sheep (YILDIZ et al, 2003). Viñoles (2003) concluded that a satisfactory body score condition increased the ovulation rate in sheep, and that nutritional supplementation from day 8 to 14 of the estrus cycle increased that of sheep with moderate body score condition.…”