Extra dietary vitamin E - selenium as a mitigation strategy against housing-induced stress in Dohne Merino lambs: Effect on growth performance, stress biomarkers, and meat quality

Deprivation of social contact through solitary confinement has the potential to induce stress in farm animals. Current evidence that housing-induced stress contributes to suboptimal welfare, growth performance and meat quality in sheep is neither ubiquitous nor convincing. This study, therefore, investigated the effect of social stress, as induced by single-pen (isolated) and paired-pen (socially interacting) housing, and extra dietary antioxidants (vitamin E - selenium) on growth performance, oxidative stress biomarkers, carcass characteristics and meat quality of 24 male Dohne Merino lambs (25.8 ± 2.7 kg). Lambs were randomly assigned to four treatment combinations in a completely randomized design: 1. single-pen housing (solitary confinement) with no extra vitamin E - selenium supplementation, 2. single-pen housing (solitary confinement) with extra vitamin E - selenium supplementation, 3. paired-pen housing with no extra vitamin E - selenium supplementation, and 4. paired-pen housing with extra vitamin E - selenium supplementation. Solitary confinement significantly (P < 0.05) reduced the superoxide dismutase and glucose levels but had no effect on glutathione peroxidase. Supplementation with vitamin E - selenium increased (P < 0.05) feed intake, weight gain, metabolic weight gain, packed cell volume (PCV), red blood cells (RBC), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). At the end of the 60-day feeding trial, paired lambs had higher (P < 0.05) slaughter weight compared to those housed individually. However, housing had no effect (P > 0.05) on hot carcass weight, cold carcass weight, carcass conformation, fat score, carcass length, and temperature, water holding capacity, meat colour (L, a*, and b*), shelf life colour (L, a*, and b*), ultimate pH (pHu), and fatty acid profiles. Vitamin E - selenium supplementation increased slaughter weight, dressing percentage, and pHu. It was concluded that solitary confinement reduced the oxidative status of lambs but vitamin E - selenium supplementation reduced the impact of the stress by increasing feed intake and growth performance. However, housing had no influence on the carcass and meat quality traits in Dohne Merino sheep.