Is neutral genetic diversity related to quantitative variation in semen traits in bulls?

Conservation decisions based on neutral genetic diversity have been observed to promote retention of useful quantitative variation in biological populations. An experiment was undertaken to determine the association between microsatellite marker polymorphisms and phenotypic variation in semen production and cryosurvival traits in bulls. Thirty-five ejaculates were collected from ten bulls of two breeds and evaluated before and after cryopreservation for several semen traits. The bulls were also genotyped using a set of sixteen bovine-specific microsatellite marker loci. Fixation indices (FST ), heterozygosity and Nei's genetic distance measures were computed from allele frequency data for each of the bulls. Molecular and phenotypic data were used to compute tri-distance matrices for the ten bulls and correlated using Mantel's test in GenAIEx 6.5. The study revealed extensive heterogeneity in semen traits, heterozygosity and FST values among the bulls. Large pairwise phenotypic and genetic distances were also observed. Correlation between pairwise genetic distances and phenotypic distances was significant and highly positive for sperm viability (r = .61, p < .001) and moderately positive for sperm motility (r = .40-42, p < .05) variables. For sperm morphology, ejaculate volume and sperm concentration, correlation with genetic distances was positive, low and not significantly different from zero (p > .05). A tendency for a triangular-shaped relationship between genetic and phenotypic distances for post-thaw motility and viability traits was also observed. Accordingly, association with neutral genetic diversity was absent for semen production traits and moderate to highly positive for sperm cryosurvival traits. Given these findings, conservation decisions based on neutral genetic diversity may capture variation in some adaptive traits, but not others.

Efficacy of neem (Azadirachta indica) aqueous fruit extracts against Sarcoptes scabiei var. suis in grower pigs.

The acaricidal activity of Azadirachta indica (neem) aqueous fruit extracts was evaluated against Sarcoptes scabiei var. suis (mange mites) in an on-farm trial using grower pigs. Aqueous neem fruit extracts of three concentrations 5%, 10%, and 25% w/v and a commercial acaricide, 12.5% amitraz-based Triatix spray (positive control), were compared with pigs that received no treatment (negative control). Thirty grower pigs of the Dalland breed were allocated to the five treatments in a completely randomized experiment. Each experimental animal was sprayed on day 0 and again on day 7. Counts of mange mites, scoring of lesion index, and calculation of rubbing index were done weekly. Topical application of 25% aqueous neem fruit extract had a higher efficacy ratio (p < 0.05) than the other fruit extract concentrations, and performed similarly to an amitraz-based acaricide, suggesting a dose-dependent response. Amitraz (positive control) cured clinical mange on grower pigs after 5 weeks and 25% aqueous neem fruit extract 6 weeks post-treatment. The results indicated that aqueous neem fruit extracts have acaricidal effects against mange mites and can provide a cheaper, safer, and more eco-friendly alternative for the control of Sarcoptes mange in pigs.

Variation in sperm cryosurvival is not modified by replacing the cryoprotectant glycerol with ethylene glycol in bulls.

Breed and sire differences in sperm cryosurvival have been noted, with negative implications for sperm cryobanking and assisted reproduction programmes. This study hypothesized that these differences could be modified by using lower molecular weight cryoprotectants. Therefore, the effect of replacing glycerol (GLY) with ethylene glycol (EG) on differential cryosurvival of semen from two Sanga cattle breeds (Mashona vs. Tuli) was determined. Three to five ejaculates were collected from each of ten bulls (3-8 years) by electro-ejaculation, diluted in three Tris-egg yolk extenders (Triladyl® , 7% GLY-based and 7% EG-based) and evaluated for sperm motility, viability and morphology at three time periods (fresh - 0 hr, pre-freeze - 4 hr and post-thaw). Tuli bulls produced larger (11.8 ± 0.31 ml vs. 8.5 ± 0.38 ml) and more concentrated ejaculates of lower fresh semen quality. Breeds differed across time for motility and morphology, but not viability. Mashona bull semen had significantly higher motility and normal morphology values at each sampling time. Bulls classified as poor freezers had lower concentration (0.70 ± 0.09 × 109  sperm/ml vs. 1.37 ± 0.10 × 109  sperm/ml), sperm motility index (SMI, 35.0 ± 3.4 % vs. 67.8 ± 2.1 %) and viability (69.7 ± 1.1 % vs. 75.7 ± 1.0 %) compared to good freezers. Maintenance of semen quality by GLY and EG did not differ between breeds, poor and good freezers, or age groups. The interaction breed by extender across time did not reach statistical significance for all variables. The study revealed that bull and breed variation in sperm quality and cryosurvival is not modified by replacing GLY with EG, suggesting that cryostress tolerance of sperm may be under control of mechanisms other than differential response to GLY cytotoxicity.