Mixing strategies for group-housed gestating sows: effects on production

Abstract Text:

Social stress from mixing sows has the potential to negatively affect sow production and welfare. Housing sows in stalls from weaning until five weeks after breeding is a common strategy used to prevent aggression and ensure control over individual feeding during breeding, conception and implantation. However, pressure to reduce stall use will likely continue, and alternative management options should be explored. This study compared the effects of three mixing strategies on sow performance in fully-slatted pens. A total of 252 sows were studied over six replicates, in groups of 14 sows/pen (2.2 m²/sow). Treatments consisted of: i) Early mixing (EM)- sows mixed into groups at weaning; ii) Late mixing (LM)- sows stall-housed at weaning and mixed at five weeks gestation; iii) Pre-socialisation (PS)- sows mixed for two days after weaning, then stall housed for breeding up to five weeks gestation, after which they were mixed (same sows). Sows were fed once daily in free-access stalls, after which they were locked out of the stalls, ensuring that sows spent up to 22 hours per day in the loafing area. Breeding and farrowing performance was recorded. Production data were analysed for differences between treatments using the GLIMMIX procedure of SAS, with treatment, parity, replicate and their interaction included in the model. Where applicable, total born was included as a covariate. The number of animals to conceive after one service was analysed by Fisher’s exact test. Production results are shown in table 1.

Table 1. Production results of sows in EM, PS and LM treatments.

Parameter	EM	PS	LM	SEM	P
Conception rate (%)	97.62	94.05	86.9	.	0.028
Wean to Service Interval (days)	4.06	4.51	4.31	0.28	0.672
Total born	15.18	15.64	15.45	0.46	0.708
Born Alive	13.72	12.86	12.93	0.45	0.312
Still born	0.88	1.28	1.35	0.16	0.078
Mummies	0.34	0.32	0.41	0.09	0.777

The lower conception rate of the LM sows may reflect sub-optimal stimulation of oestrus during stall housing. In comparison, the EM and PS groups received mixing stress immediately post weaning, which may have stimulated follicular growth and clearer oestrus expression. A tendency for fewer stillborn piglets in EM sows may result from improved fitness and/or activity levels during early gestation. For other variables, EM sows preformed similarly to PS and LM sows. These results suggest that, under good management conditions, mixing sows at weaning does not negatively impact sow performance.

Keywords: Sows, Gestation, Grouping, Production