Artificial long days in addition to exogenous melatonin and daily contact with bucks stimulate the ovarian and oestrous activity in Mediterranean goat females

The male effect associated with prostaglandins and reproductive outcomes in photo-stimulated Saanen goats during the non-breeding season

The efficiency of combining oestrous induction via a light program (16 h of light and 8 h of darkness for 60 days, ending on Day 0 - D0) with cloprostenol administration, followed by the male effect or not, was tested in acyclic Saanen goats during the non-breeding season (June/2019 to January/2020). Initially, all animals (males and females) were submitted to the described light program; 60 days after its ending (D60), the females were divided into two groups, with (G1; n = 67) or without (G2; n = 61) a male effect from D60 to D75 after the light program. At D75, both groups received two cloprostenol doses (120 μg; intramuscular) 7.5 days apart (D75 and D82.5). Artificial insemination was performed at a specific time according to the oestrous onset (approximately 68.4 ± 1.2 h between the second cloprostenol dose and IA). Ultrasound scans were performed at different intervals to evaluate follicular dynamics and confirm pregnancy. At the first cloprostenol dose (D75), the proportion of does with at least a corpus luteum (CL), which indicates resumed cyclicity, was greater in G1 than in G2 (85.2% vs. 48.8%; p < .05), although no difference was found at the second dose (p > .05). The adjusted pregnancy rates (number of pregnant goats/oestrous goats) differed between G1 and G2 (21.7% vs. 42.0%; p < .05). G1 also showed a higher frequency of functional CL (based on blood flow and morphology) compared to G2 (96.9% vs. 66.7%; p < .05) at D116. A male effect using photo-stimulated bucks after the first cloprostenol dose increased the number of does presenting CL after buck removal, and no impairment in the pregnancy rates of multiparous does was found.

Effects of Melatonin Implants on Reproductive Performance of Dairy Sheep and Dairy Goats

This study investigated the effects of melatonin implants in female and male before the breeding season on the reproductive performance of Tahirova sheep and Turkish Saanen goats. Seventy-five sheep and 53 goats (including 6 rams and 4 bucks) were used in the research. Melatonin implants (18 mg) were applied to half of the female and male animals, one to females and three to males. The rate of estrus was determined as 100% in the melatonin (M) and control (C) groups. The non-return rate, conception rate and lambing rate were close in both groups of ewes and rams groups (P>0.05). The rate of estrus was 100% in the melatonin and control groups of does and bucks groups in Turkish Saanen goats. The non-return rate in does was 75.0±9.02% in M group and 92.0±5.53% in C group (P=0.0101), the non-return rate was 83.3±6.92% in group M and 84.2±8.59% in group C for bucks (P=0.5570). For ewes, the duration from ram introduction to first estrus, conception and lambing was significantly lower in group M than in group C (P≤0.05). Litter size of M in ewe and ram groups were 1.70±0.08 and 1.59±0.09, respectively, whereas it was 1.62±0.10 and 1.74±0.10 in C group, respectively. The birth weight significantly differed between ewe groups (P=0.0017). For goats, the duration from buck introduction to first estrus, conception and lambing was similar in the groups of does and bucks (P>0.05). Litter size of M in doe and buck groups were 1.57±0.11 and 1.53±0.12, respectively, and 1.46±0.11and 1.50±0.09 in C group, respectively (P>0.05). While the live weight and body condition score (BCS) of ewes were significantly affected by melatonin implants (P≤0.05), the live weight and BCS of does were not affected. In conclusion, it might be said that melatonin implants obtained better results for reproduction in Tahirova sheep than Turkish Saanen goats.

Reproductive performance is improved during seasonal anoestrus when female and male Murciano-Granadina goats receive melatonin implants and in Payoya goats when females are thus treated

This work investigates whether the reproductive performance of Mediterranean goats achieved using melatonin implants at around the spring equinox is affected by the protocol followed, i.e. implanting females only, males only, both sexes or neither sex. In a first experiment, Murciano-Granadina females (n = 419, 510 and 631 for three consecutive years) were divided into four groups: treated with melatonin (FM) and not treated with melatonin (FC), mounted by males treated with melatonin (MM) or not (MC). In a second experiment, performed during 2009, the same protocols were used with 635 Payoya females and the results compared with those obtained for the same year for the Murciano-Granadina breed. Fertility (percentage of goats kidding), litter size (number of kids born per female kidded) and productivity (number of kids per female in each mating group) were calculated. In the first experiment, better reproductive performances were obtained when females (overall fertility: 71.1% vs 57.0% for the FM and FC animals; productivity 1.37 ± 0.04 kids per female vs 1.12 ± 0.03 kids per female for the FM and FC animals; p < 0.01) or males (overall fertility: 65.9% vs 58.4 for the MM and MC animals; productivity 1.28 ± 0.03 kids per female vs 1.13 ± 0.04 kids per female for MM and MC groups, respectively; p < 0.01) were implanted with melatonin. Moreover, the interaction sex × melatonin treatment had a significant effect (p < 0.05) on productivity. In the second experiment, for the Murciano-Granadina breed, the greatest increase in the number of kids born per female was obtained when the females were treated with melatonin, in either the FM/MC or FM/MM protocols (0.54 extra kids and 0.53 extra kids per female, respectively) (p < 0.01). In the Payoya breed, the greatest increase was obtained using the FM/MC protocol (0.19 extra kids per female). Thus, improved reproductive performances are obtained when female Murciano-Granadina and Payoya goats are implanted with melatonin, although important differences in reproductive performance are seen between the breeds.