The effect of group composition and mineral supplementation during rearing on the behavior and welfare of replacement gilts

Abstract

Sow longevity supported by good health and reproductive performance is necessary to optimize sow lifetime performance. In some countries, replacement gilts are reared with finisher pigs destined for slaughter, so they are exposed to sexual and aggressive behaviors performed by males. This is associated with stress and injury. Moreover, diets formulated for finishers are not designed to meet the needs of replacement gilts and may not supply the necessary minerals to promote limb health, optimal reproduction, and, thus, sow longevity. In this 2 × 2 factorial design experiment with 384 animals (32 pens [12 animals per pen]), we investigated the effect of female-only (FEM) or mixed-sex (MIX) rearing, with (SUPP) or without (CON) supplementary minerals (copper, zinc, and manganese) on locomotion, salivary cortisol levels, behavior, body lesions (BL), and hoof health of gilts. The experimental period began at transfer to the finisher stage (day 81.3 ± 0.5 of age; day 0) until breeding age (day 196 ± 0.5 of age; day 115). Locomotion was scored (0–5) biweekly from day 0 until slaughter day 67 or breeding age day 115 for the remaining gilts. Saliva samples were taken monthly from four focal gilts per pen. All counts of aggressive, harmful, sexual, and play behavior were recorded by direct observation 1 d biweekly (5- × 5-min observations/pen/d). BL scores were recorded on focal pigs biweekly from day 1 until day 99 on the back, neck, shoulder, flank, and hind quarter on each side of the body. Hind hooves were scored for eight disorders (heel erosion [HE], heel sole separation [HSS], and white line separation [WLS], dew claw length and dew claw cracks, toe length and both vertical and horizontal toe cracks) by severity, and a total hoof lesion score was calculated by summing individual scores. General linear mixed models were used to analyze cortisol, behavior, BL, and total hoof scores. Generalized linear mixed models were used for locomotion, bursitis and individual hoof disorders. There was less aggression (P < 0.05) and sexual behavior in the FEM compared to the MIX groups with more play behavior in MIX compared to FEM groups (P < 0.01). Gilts in the MIX groups had higher BL scores than gilts in the FEM groups (P < 0.001). Total hoof scores were higher in MIX (8.01 ± 0.15) than FEM (7.70 ± 0.12; P < 0.02) gilts. CON diet gilts had higher HE scores than SUPP gilts (P < 0.05). HSS (P < 0.05) and WLS (P < 0.05) scores were higher in MIX than FEM gilts. Rearing gilts in FEM groups had benefits for hoof health likely mediated through lower levels of activity due to male absence, and minerals helped reduce HE.

Rearing in female-only groups and dietary mineral supplementation improves sow welfare in the early parities and lifetime performance

“…Nevertheless, none of the hoof disorders we observed were severe, and this could explain why no differences in locomotion scores were observed. In line with findings on the same animals during rearing ( Hartnett et al, 2020 ), total hoof lesion scores were higher in the sows reared in the MIX groups compared with sows reared in the FEM groups. Thus, the claw horn damage resulting from more activity (mounting, aggression, and play) on the concrete slatted floors during rearing persisted (Gjein and Larssen, 1995a; Pluym et al, 2011 ; Quinn et al, 2015 ).…”

“…Hoof lesion scores in mid-gestation were considerably higher compared with the scores recorded in the same gilts during rearing ( Hartnett et al, 2020 ). Furthermore, they continued to increase until the last inspection, when sows farrowed for the second time.…”

“…With regard to the increased avoidance response by MIX sows to the FHA test, again, this could be due to a slightly reduced ability to tolerate a novel experience. Rearing conditions have lifelong effects on animal behavior ( Beattie et al, 1995 ) and stress responses ( Olssen et al, 1999 ), and the gilts reared with males were exposed to much higher levels of activity, aggressive behavior, and mounting, for the first 7 mo of their lives, relative to gilts in the FEM groups ( Hartnett et al, 2020 ). We were unable to source information in the literature regarding the long-term behavioral effect on gilts of rearing with un-castrated male pigs.…”

“…Details of the experimental design including the treatments applied during the gilt rearing stage are outlined in Hartnett et al (2020) . In brief, a two by two factorial arrangement was applied to 288 gilts.…”

“…The aim of this study was to investigate the carryover effects of rearing replacement sows in female-only groups and of a trace mineral (Cu, Zn, and Mn) supplemented diet, on aspects of their welfare in their early parities and on their lifetime performance. We previously showed that these strategies had benefits for several aspects of gilt welfare up to breeding age ( Hartnett et al, 2020 ), so we hypothesized that this would improve gilt welfare during the first pregnancy and have long-term benefits for longevity and reproductive performance. A secondary hypothesis was that offspring from gilts reared in female-only groups and supplemented with dietary minerals would have higher birth weights and improved performance from birth to finish.…”