The incidence of luteal activity, as determined by peripheral plasma progesterone concentration, before the onset of the breeding season in the Rasa Aragonesa breed of sheep.
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Biomedical subjects
F Forcada
Publications and source records attributed to F Forcada.
Effect of exogenous melatonin and plane of nutrition after weaning on estrous activity, endocrine status and ovulation rate in Salz ewes lambing in the seasonal anestrus.
Forty-nine Spanish Salz ewes lambing in the second fortnight of March (20 March +/- 1.5 d) were used to determine the effects of exogenous melatonin and postweaning nutrition on endocrine status, date of first estrus and ovulation rate. Experimental design was a factorial defined by 2 postweaning planes of nutrition, 1.80 (high) and 1.35 (low) times the maintenance requirements, and treatment with a single 18-mg subcutaneous implant of melatonin (M) 32 d after lambing or no treatment control (C). Mean weaning to first estrus interval was shorter in treated than in control ewes (50.8 +/- 4.2 vs 87.6 +/- 6.3 d; P < 0.01). Considering both the treated and control animals together, the ratio between mean night and daytime plasma melatonin levels was significantly correlated with the implant insertion-first estrus interval on Day 5 (0.67; P < 0.01) and Day 35 (0.63; P < 0.05) after implantation. Melatonin implants induced a significant increase of mean LH concentrations at Days 14 and 33 after implantation (P < 0.01) without any significant influence of plane of nutrition. Ovulation rate was higher for treated than control ewes in the second estrus (P < 0.05). An interaction between plane of nutrition and exogenous melatonin on ovulation rate at the second cycle after weaning was detected (P < 0.01), being close to the significance in the first, fourth and fifth cycles (P < 0.1). These results suggest that exogenous melatonin in April may be an effective way of advancing the breeding season and enhancing ovulation rate associated with a low rather than a high plane of nutrition.
Journal Article↗
Effect of plane of protein after weaning on resumption of reproductive activity in Rasa Aragonesa ewes lambing in late spring.
The effect of protein supplementation after weaning on the resumption of reproductive activity in a Spanish breed of ewes (Rasa Aragonesa) with a reduced seasonality was studied. Two equal groups of ewes were weaned in the first 2 weeks of July. From weaning to the end of the experiment both groups were fed identical energy-content rations but with different protein levels (high, Group H; low, Group L). The mean time between weaning and first detected estrus was 64 days. No differences between groups were found either in relation to this interval or in the ovulation rate in the first estrus. Ewes showing a multiple ovulation rate in the first cycle anticipated the onset of sexual activity after weaning. Significant differences in the ovulation rate were detected between the 2 groups from September to the end of the experiment (1.55 vs 1.05 corpora lutea for Groups H and L, respectively; P<0.001). In conclusion, the effect of a protein supplement after weaning in Rasa Aragonesa ewes lambing in late spring is reflected at mid-term in the early breeding season, with an evident rise of ovulation rate in the nutrient supplemented group.
Journal Article↗
Ram sperm selection by a dextran/swim-up procedure increases fertilization rates following intrauterine insemination in superovulated ewes.
The objective of this study was to compare the efficacy of 2 dextran/swim-up media to increase the sperm quality parameters and the maintenance of these parameters at 15 degrees C and 30 degrees C over 6 hours. Additionally, this study examined whether differences in sperm quality reflect different reproductive efficiencies following intrauterine insemination in superovulated ewes. The study involved 2 selected samples (SS) obtained by dextran/swim-up, performed either with (SS+) or without (SS-) capacitating compounds, and a control sample consisting of raw semen diluted in the same medium. The efficacies of the swim-up sperm selection procedures were similar in both media, and no significant differences were found among the evaluated parameters. Conversely, we found important differences between selected and control samples. Sperm motility, viability (as assessed by carboxifluorescein diacetate/propidium iodide [PI] staining), and mitochondrial activity (as assessed by rhodamine 123/PI) were significantly higher in the selected samples than in the control. Additionally, following incubation at 15 degrees C, the preservation of sperm quality was significantly better in the selected samples than in the control samples. After 6 hours of incubation at 15 degrees C, selected samples had a motility value of 46%, which was significantly (P < .001) higher than the value observed in control samples (27%). The percentage of viable cells observed after 6 hours of incubation at 15 degrees C was significantly (P < .0001) higher in selected samples than in the control samples. Furthermore, after 2 hours of incubation at 30 degrees C, swim-up samples had viability values that were significantly (P < .0001) higher than those of the control samples. SS+ and SS- samples did not differ significantly in spermatozoa yield, sperm quality, or survival. Differences between selected samples and controls were reflected in the fertilization rate obtained following intrauterine insemination in superovulated ewes that experienced a 52-hour interval between progestagen removal and artificial insemination. A restricted criterion for fertilization rate evaluation was established, and only the percentage of embryos recovered from the uterine horns 6 days after insemination was considered with respect to the total number of corpora lutea counted in the ovaries. The fertilization rate of SS- samples (50%) was significantly higher (P > .001) than those of the SS+ (2%) and control samples (5%).
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