In the pig industry, stimulating a fertile oestrus during lactation allows piglet weaning ages to be increased without impairing farrowing frequency (Soede et al., 2012). Therefore, selection of sows with a high propensity to express lactation oestrus would be beneficial. Anti-Mullerian Hormone (AMH) concentration is a reliable indicator of ovarian reserve in many species and plasma AMH is positively related to puberty response in pigs (Reed et al., 2013). We hypothesised that lactating sows with high AMH on day 18 post-parturition will be more likely to express lactation oestrus.
On day 18 post-parturition, 54 Large White x Landrace lactating multiparous sows had a blood sample collected and commenced daily 15 minute boar contact. Sows were artificially inseminated at first detection of lactation oestrus and slaughtered 30 days post-insemination. Ovulation rate and embryo number were recorded. Embryo survival was calculated as the number of embryos as a proportion of corpora lutea. Plasma AMH was measured with the Human MIS/AMH DuoSet ELISA Kit (Beckman Coulter, Roissy, France) previously validated for use in bovine. Sows were divided into HIGH (39.2 ± 5.3 ng/mL) or LOW (5.4 ± 5.5 ng/mL) AMH groups using the median value of AMH. An ANOVA was used to determine the effects of HIGH or LOW AMH on all variables (GenStat Version 11, VSN International, England, UK).
More sows with HIGH AMH expressed a lactation oestrus (96% versus 67%, P<0.01). HIGH AMH sows also had a higher ovulation rate (23.7 ± 0.7 versus 21.4 ± 0.9; P<0.05); however, plasma AMH did not affect embryo survival (HIGH AMH, 62.8 ± 4.6%, versus LOW AMH, 63.3 ± 5.7%; P>0.05). Therefore, this experiment shows that plasma AMH on day 18 post-parturition is a good indicator of sows that will exhibit oestrus in lactation.