In vitro assessment of sperm quality from rams of high and low field fertility.

The aim of the present study was to investigate whether differences in field fertility of rams are reflected in differences in several sperm quality parameters. Ejaculates from 8 adult rams, 4 with high and 4 with low field fertility, were collected weekly using an artificial vagina over 6 consecutive weeks. Analyses of sperm motility by computer-assisted sperm analysis (CASA), membrane integrity by acridine orange-propidium iodide combination and sperm DNA fragmentation using the sperm chromatin dispersion test (SCD) were performed at 0, 3, 6 and 24h of incubation at 37°C. Sperm nuclear morphometry was also determined at 0h by computer-assisted sperm morphometry-fluorescence (CASMA-F). Sperm viability and most CASA sperm motility parameters were higher at 0, 3 and 6h in the high fertility rams. These rams had also a higher sperm nuclear area, perimeter and length (P<0.05) determined by CASMA-F. Significant differences between high and low fertility groups were also found in the dynamics in DNA fragmentation, with significant differences at 6h (14.42±1.40 and 20.27±1.77, respectively, P<0.05) and at 24h (22.32±2.03 and 31.24±2.54, respectively, P<0.01). It was concluded that high and low fertility rams present clear differences in several sperm quality parameters. This opens up the possibility of selection of males for artificial insemination based on sperm quality data.

Factors affecting fertility after cervical insemination with cooled semen in meat sheep.

Field results of 18,328 cervical artificial inseminations (AI) with cooled semen in Rasa Aragonesa meat sheep under field conditions in north-eastern Spain AI were analyzed. Logistic regression procedures were used including fertility at AI as the dependent variable (measured by lambing, 0 or 1) and year, month of AI, farm, hours between extraction and insemination, number of ewes inseminated in a set of AI, parity, lambing-treatment interval, total number of synchronization treatment per ewe, inseminating ram and AI technician as independent factors. Previous parturitions, lambing-AI interval, month, farm, inseminating ram and technician were factors with significant impact on AI fertility. Based on the odds ratio, the likelihood of pregnancy decreased: in ewes with more than five previous parturitions (by a factor of 0.87, 0.79 and 0.66 for the 6th, 7th and ≥8 parturitions, respectively); in ewes with lambing-AI interval higher than 240 days (by a factor of 0.8); and for inseminations performed during the spring period, (March, April, May and June, 0.70, 0.76, 0.66, and 0.76, respectively). We noted a higher fertility in seven inseminating rams (odds ratios between 1.4 and 1.7) and lower in two rams (odds ratios between 0.6 and 0.7). Of the 17 AI technicians, two were related to fertilities improved by odds ratio of 1.6, and 1.30, whereas two technicians were attributed fertility rates reduced by odds ratios of 0.68 and 0.40. These findings should be taken into account to evaluate the AI technique performance and make decisions to enhance fertility results.