Rearing strategies to optimise gilt and sow welfare

In Ireland, replacement gilts are often reared with finisher pigs, including entire males. This exposes them to sexual mounting and aggression, which is stressful and injurious. Moreover, finisher diets do not supply necessary minerals for optimal limb health which has a negative impact on welfare and performance. The objectives of this thesis were 1) to investigate two rearing strategies we hypothesised would improve limb health in developing gilts 2) to examine the condition of the gilts’ bones and cartilage at breeding age 3) to assess carry-over effects of rearing treatments on sow welfare and performance and 4) to investigate levels of two potential biomarkers (C2C and CPII) of bone cartilage turnover, relative to bone cartilage condition and rearing treatment. Using a 2 × 2 factorial arrangement, we reared 288 gilts in either female-only (FEM) or mixed-sex (MIX) groups, and fed them either a standard finisher diet (CON), or the same diet supplemented with copper, zinc and manganese (SUPP). We expected improved limb health, welfare and performance both during rearing, and subsequently, in gilts in FEM and SUPP, and that the effects would be additive. During rearing, FEM gilts were less exposed to sexual mounting/aggression, and had improved hoof health (specifically less heel sole separation and white line lesions); the SUPP diet also reduced heel erosion. At breeding age gilts from SUPP had a greater aBMD than CON, and gilts reared in FEM had fewer cartilage lesions. The effect of rearing strategy on hoof health carried over into the early parities; FEM gilts had lower total hoof lesion and heel erosion scores, and SUPP gilts had lower horizontal crack scores. However, we found very few effects on levels of C2C or CPII. Thus, both rearing strategies had benefits for animal welfare, but validation of bone cartilage turnover biomarkers in pigs requires further research.