Simple SummaryThe lifetime performance of commercial sows relies on longevity, which is dependent on good health, particularly, limb health. In many countries, young female pigs (gilts) intended for breeding are often reared with male finisher pigs destined for meat production. However, finisher diets are not designed to meet the needs of developing gilts and may not supply the necessary minerals to support good limb health. Moreover, gilts reared with uncastrated (i.e., entire) male pigs are exposed to high levels of sexual mounting and aggression, which may cause physical damage. This experiment investigated the effect of female-only or mixed-sex rearing with and without supplementary minerals (Copper, Zinc and Manganese) on locomotory ability, cartilage condition and areal bone mineral density (aBMD) of breeding age gilts. The addition of the minerals to the diet resulted in increased aBMD in the humerus bone compared to gilts on the control diet. Rearing gilts in female-only groups reduced the number of cartilage lesions, and there were fewer incidences of elbow cartilage fractures. Overall, both strategies (mineral supplementation and female-only rearing) had benefits for limb health, which could help to improve sow longevity.AbstractLameness is a major cause of poor longevity and poor welfare in replacement gilts. The problem is exacerbated by inappropriate housing and diet during the rearing period. Replacement gilts are often reared with male finisher pigs destined for slaughter. If they are not castrated, they perform high levels of potentially injurious sexual and aggressive behaviour. Furthermore, finisher pig diets are not designed to meet the needs of developing gilts and may not supply the necessary minerals to support good limb health. The objective of this study was to evaluate the effect of supplementing the diet of replacement gilts with copper, zinc and manganese and separating them from males during the rearing period on locomotory ability, bone mineral density and cartilage lesion scores. A 2 × 2 factorial design experiment investigated the effect of female-only or mixed-sex rearing, with or without supplementary minerals (Copper, Zinc and Manganese). In total, 384 maternal line gilts were assigned to 32 pens of 12 and were locomotion scored during the rearing period. A sub-sample (n = 102) of gilts were culled at breeding age and the front right limb was removed at slaughter. Areal bone mineral density (aBMD) was measured using dual energy X-ray absorptiometry, after which the limb was dissected to score the condition of the cartilage. The addition of trace minerals to the diet resulted in increased aBMD in the humerus (P < 0.05) compared to the control diet. Rearing gilts in female-only groups reduced the number of cartilage lesions overall (P < 0.05), and on the humeral condyle (P < 0.05). Rearing replacement gilts in female-only groups and with mineral supplementation had benefits for limb health.

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 &lt; 0.05) and sexual behavior in the FEM compared to the MIX groups with more play behavior in MIX compared to FEM groups (P &lt; 0.01). Gilts in the MIX groups had higher BL scores than gilts in the FEM groups (P &lt; 0.001). Total hoof scores were higher in MIX (8.01 ± 0.15) than FEM (7.70 ± 0.12; P &lt; 0.02) gilts. CON diet gilts had higher HE scores than SUPP gilts (P &lt; 0.05). HSS (P &lt; 0.05) and WLS (P &lt; 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.

The lifetime performance of commercial sows relies on longevity, which is dependent on good health and reproductive performance. However there is a high rate of wastage of sows in the early parities which is influenced by the way they are managed and housed during rearing. This study investigated the carry-over effect of gilt rearing strategy on measures of welfare and performance. Eighty sows were reared using a 2 × 2 factorial design; rearing group composition (GC; female only (FEM) or mixed sex (MIX) from weaning) , with or without supplementary minerals (MIN; CON = control diet; SUPP= control + Cu, Zn and Mn) from five weeks into the finisher stage . Once served, gilts were managed in a dynamic group gestation pen and fed a standard gestating sow diet. Locomotory ability was scored (0-5) and salivary cortisol measured 5 times during the 1 st gestation, and human approach tests carried out at d108. Hooves were scored for injuries and legs for bursas at d70 of the 1 st gestation, at 1 st weaning, and at the 2 nd farrowing. Sow behavior in the hoof scoring crate (movement, vocalization, handling ease) was also recorded. The numbers of piglets born alive and dead during the first 5 parities was recorded, as was the performance of the first litter to finish. Data were analyzed using general or generalized linear mixed models, as appropriate, using SAS (v 9.4). There was no effect (P &gt; 0.05) of rearing treatment on locomotory ability, bursa score, the total number of piglets born or on offspring growth. However, there was an interaction between GC and MIN (P &lt; 0.05) on salivary cortisol levels with MIX × SUPP sows having the highest levels. Total hoof scores and heel erosion scores were higher in sows reared in MIX groups (P &lt; 0.01), and CON sows tended to have higher horizontal crack scores (P=0.06). Sows from MIX kicked more at weaning than FEM (P &lt;0.05) and tended to be more fearful in the forced human approach (FHA) test (P = 0.1) where they are scored on their reaction to being approached. They also had more stillborn piglets across all 5 parities than FEM (P &lt; 0.05). Overall, rearing replacement sows in FEM groups and dietary mineral supplementation had minimal but beneficial effects on their subsequent welfare and performance.