Effects of the classification of boars according to progressive sperm motility and the extender type on the reproductive performance of a single fixed-time insemination.

The study aimed to evaluate the fertility of boars according to the resistance of their semen to storage using dilution in either Short- or Long-term extender for single fixed-time insemination. From a total of 32 boars, twelve boars were classified during three semen collection (one collection/boar/week) as Low- (64.5%) or High-preservation (83.9%) capacity for maintaining progressive motility (PM) at 120 h of storage using Short-term extender. After the selection period, six ejaculates (weekly collected) from the Low- and High-preservation boars were diluted in Short- or Long-term extender (2 × 2 factorial design) for insemination and evaluation of fertility. A total of 519 weaned sows were submitted to induction of ovulation with triptorelin (OvuGel®) at 96 h post-weaning. Twenty-four hours later, estrus sows were single fixed-time inseminated (FTAI) with semen doses from the different groups of evaluation. The SAS® software was used for statistical analysis considering the class of boar, type of extender, and interaction as fixed effects. The GLIMMIX procedure was used, considering a binomial distribution for total motility (TM) and PM, binary distribution for pregnancy (PR), and farrowing rate (FR), and the total born (TB) was analyzed assuming a normal distribution with the comparison of means by Tukey-Kramer test. An interaction of class of boars and type of extender was observed for TM and PM at insemination (P < 0.001). Long-term extender increased TM in Low-preservation boars, with no effect in High-preservation boars. The ejaculates from High-preservation boars diluted in Short- or Long-term extender showed higher PM at insemination (86.8 and 87.8%, respectively) compared to those from Low-preservation boars in Short- or Long-term extender (73.2% and 77.9%, respectively). There was no effect of the interaction of boar preservation class and type of extender (P ≥ 0.163) on PR, FR or TB. However, Low-preservation boars presented lower TB (14.1 ± 0.2) compared to High-preservation boars (15.0 ± 0.2; P < 0.01). The PR (93.3 vs. 90.1) and FR (88.8 vs. 88.2) were not affected by class of Low- or High-preservation boars, respectively (P ≥ 0.187). The type of extender did not affect PR, FR, or TB (P ≥ 0.440). In conclusion, Low-preservation boars impaired the reproductive performance of single-FTAI sows by reducing TB with no apparent effect on PR or FR.

Seminal factors influencing return to estrus in female pigs following artificial insemination

Tests were applied to extended, chilled boar semen to further define those factors associated with return to estrus in inseminated female pigs (sows and gilts). Females were each inseminated twice with the same batch of extended chilled single-sire semen that was concurrently assessed at the Charles Sturt University Andrology Laboratory (CSUAL) in Australia. Semen traits tested were pH, clump score and temperature while sperm morphology assessment included abnormal heads, acrosomes, midpieces, tails and retained cytoplasmic droplets. Sperm motility and concentration were tested using a computerized sperm analyser (CASA) system. Female return types were categorised as early, early regular, early irregular, late regular and late. Depending on the type of variable of interest, statistical analyses used linear mixed models or generalised linear models. Terms included in the models were dam line, sire line, parity, insemination season, return type, individual boars and inseminators. Of 1205 inseminated females, 894 (74.2%) farrowed, 3 (0.2%) aborted and 308 (25.6%) showed different types of return to estrus. The fixed variables dam-line, sire-line and parity were significantly (P < 0.05, P < 0.05 and P < 0.001 respectively) associated with female return type, although inseminator and insemination season were not. Of the semen/sperm traits tested, the acrosomal defects that were significantly associated (P < 0.05) with female return-type were morphologically abnormal acrosomes and percent intact acrosomes while cytoplasmic droplets, normal morphology and bacterial score also influenced return type (P < 0.05). There were also correlations between sperm factors such as abnormal sperm tails, motility and velocity and sow parity. In conclusion, sperm morphologic assessment, in particular of the acrosome region, was useful in predicting female returns to estrus.

Seminal factors influencing return to estrus in female pigs following artificial insemination

Tests were applied to extended, chilled boar semen to further define those factors associated with return to estrus in inseminated female pigs (sows and gilts). Females were each inseminated twice with the same batch of extended chilled single-sire semen that was concurrently assessed at the Charles Sturt University Andrology Laboratory (CSUAL) in Australia. Semen traits tested were pH, clump score and temperature while sperm morphology assessment included abnormal heads, acrosomes, midpieces, tails and retained cytoplasmic droplets. Sperm motility and concentration were tested using a computerized sperm analyser (CASA) system. Female return types were categorised as early, early regular, early irregular, late regular and late. Depending on the type of variable of interest, statistical analyses used linear mixed models or generalised linear models. Terms included in the models were dam line, sire line, parity, insemination season, return type, individual boars and inseminators. Of 1205 inseminated females, 894 (74.2%) farrowed, 3 (0.2%) aborted and 308 (25.6%) showed different types of return to estrus. The fixed variables dam-line, sire-line and parity were significantly (P < 0.05, P < 0.05 and P < 0.001 respectively) associated with female return type, although inseminator and insemination season were not. Of the semen/sperm traits tested, the acrosomal defects that were significantly associated (P < 0.05) with female return-type were morphologically abnormal acrosomes and percent intact acrosomes while cytoplasmic droplets, normal morphology and bacterial score also influenced return type (P < 0.05). There were also correlations between sperm factors such as abnormal sperm tails, motility and velocity and sow parity. In conclusion, sperm morphologic assessment, in particular of the acrosome region, was useful in predicting female returns to estrus.(AU)