Commercial evaluation of a mating in lactation protocol

Alternative management of the sow and her litter in conventional farrowing accommodation to uncouple mating from the weaning process has been investigated over recent years in Australia. The main rationale behind this research was to enhance the weaning process for the piglet without compromising sow productivity. Extending weaning age or gradual weaning through intermittent sucking can help piglets adapt to the weaning process, resulting in a decrease in the incidence and/or severity of the post-wean growth check (Kuller et al. 2004). However, increasing weaning age will decrease the number of litters per sow per year and gradual weaning will result in some sows cycling whilst they are still lactating, leading to an increase in sow non-productive days (Downing 2015). In order to improve the piglet weaning experience in combination with maintaining sow performance, mating sows whilst they are still lactating may be a viable option. The aim of this study was to compare subsequent reproductive outcomes between sows that were mated during lactation and those that were mated after weaning under commercial production conditions.

This study was conducted over a 12 month period between August 2015 and July 2016. The lactation oestrus (LO) induction protocol consisted of sow and piglet separation (placement of a solid board within the farrowing crate that separated the piglets from the sow) along with fence line boar exposure during the last week of lactation. All sows were monitored for signs of oestrus and were mated in the farrowing crate by artificial insemination if they displayed standing oestrus. Those sows that did not display oestrus during lactation were mated at their first standing oestrus after weaning. Subsequent reproductive outcome data was analysed using GLM analysis or Chi-squared (χ²) (SPSS v24.0, IBM, Armonk, NY, USA). The percentage of sows (Parity 3.1 ± 0.10) that had a lactation oestrus was 40%. Sows mated during lactation (responders, n = 166) had a lactation length (LL) of 29.8 ± 0.37 days and a wean to re-mating interval (WRI) of –1.3 ± 0.34 days compared to a LL of 28.8 ± 0.28 days and WRI of 6.5 ± 0.27 days for those sows mated after weaning (non-responders, n = 253) (P < 0.05). The farrowing rate for responders was 78% compared to 88% for non-responders (χ² = 7.99; P < 0.05) and piglets born alive was 10.7 ± 0.46 for responders and 11.2 ± 0.41 for non-responders (P > 0.05). The number of sows that displayed oestrus during lactation dropped during summer and those that were mated had a lower farrowing rate and piglets born alive compared to both responders mated during winter, spring and autumn and non-responders mated in summer and winter, spring and autumn (Fig. 1).

Fig. 1.  Farrowing rate and born alive for non-responders (NR) and responders (R) according to season. S NR (Summer – Non-Responders); S R (Summer – Responders); WSA NR (Winter, Summer and Autumn – Non-Responders); WSA R (Winter, Summer and Autumn – Responders). ^a,bare significantly different from each other (P > 0.05).

In conclusion, lactation length and season had a significant effect on the number of sows that responded to the LO induction protocol. Additionally, subsequent reproductive outcomes were negatively affected for sows mated during lactation in summer compared to those mated during lactation in other seasons. However, there was no difference in subsequent reproductive outcomes between sows mated in lactation outside of summer and those mated after weaning.