Effects of dietary L-glutamine as an alternative for antibiotics on the behavior and welfare of weaned pigs after transport
Résumé
A decrease in antibiotic use in livestock production is a societal demand. Alternative feed supplements have shown promising effects in terms of performance, but their impacts on welfare have had little evaluation. The objectives of the study were to evaluate the effect of no antibiotic, L-glutamine or antibiotic supplementation after weaning and a transport stress on short-term and long-term welfare indicators and behaviors to determine if L-glutamine could be a viable antibiotic alternative for piglets post-weaning. A total of 240 piglets, from 32 distinct litters, were weaned at 18±4.2 days (means ± SD; weight 5.4±1.4 kg) and immediately
herded up ramps into a trailer for a 12 h transport. After transport, they were divided, per group of 8, between 3 diets fed for a 2 week period: A – an antibiotic diet including a common commercial prophylactic antibiotic (n=80; chlortetracycline(0.40 g/kg) + Tiamulin(0.035 g/kg)); NA – a control diet without any prophylactic antibiotic or feed supplement (n=80); GLU – a diet including L-glutamine (n=80; 0.20% L-glutamine as-fed). After the 2-week period, all piglets were fed the same control diet. Tear staining, as an indicator of stress, was measured on days 0, 2, 7, 15, 21, 28, 34, 47, 84, 110, 147 post-weaning from photographs. Skin lesions,
as an indicator of aggression, were counted 2 days before weaning and on days 2 and 36 postweaning.
Novel object tests (NOT) were done in groups in the pigs’ home pen on days 16, 46, 85, 111 post-weaning. The treatment effects were evaluated using repeated measures ANOVA, with treatment groups, periods and their interaction as fixed effects, and the pen as a random effect. The statistical unit was the pig. The NA pigs tended to have larger tear stains than A pigs on days 84, 110 (P<0.1), and larger tear stains than GLU pigs on day 84 and 110 (P<0.05). Effects on skin lesions were only found on day 2 for the establishment of the hierarchy, with NA pigs (25.3±12.3) having more lesions than A (21.1±12.3) and GLU (18.8±12.0) pigs (P<0.01). During the NOT on day 16, A pigs tended to avoid (1.6±2.6 times) the object more than NA
pigs (0.8±1.4) (P<0.1). On day 85, NA pigs spent less time (190±68.5 s) exploring the object than the two other groups (215±42.7 and 216±41.6 s, both P<0.01), and on day 111, NA pigs took longer (11±21.4 s) to interact with the object than GLU (4±5.5 s, P<0.01) and A pigs (5±5.7 s, P<0.05). The results demonstrate that short-term feeding strategy can have both short- and long-term effects on behavior and welfare. NA pigs appeared less interested in novel objects and more sensitive to environment and management than pigs on the other two treatment groups. Supplementation with L-glutamine appears to confer similar benefits to, and thus could be a viable alternative to dietary antibiotics.