Do weaner pigs need in-feed antibiotics to ensure good health and welfare?
By Alessia Diana, Edgar G. Manzanilla, Julia A. Calderon Diaz, Finola C. Leonard,
Laura A. Boyle. 2017. PlosOne.
Antibiotics (AB) are used in intensive pig production systems to control infectious diseases
and they are suspected to be a major source of antibiotic resistance. Following the ban on
AB use as growth promoters in the EU, their prophylactic use in-feed is now under review.
The aim of this study was to evaluate the effect of removing prophylactic in-feed AB on pig
health and welfare indicators. Every Monday for six weeks, a subset of 70 pigs were
weaned, tagged and sorted into two groups of 35 pigs according to weight (9.2 ± 0.6 kg). AB
were removed from the diet of one group (NO, n = 6) and maintained in the other group (AB,
n = 6) for nine weeks. Ten focal pigs were chosen per group. After c. five weeks each group
was split into two pens of c.17 pigs for the following 4 weeks. Data were recorded weekly.
Skin, tail, ear, flank and limb lesions of focal pigs were scored according to severity. The
number of animals per group affected by health deviations was also recorded. The number
of fights and harmful behaviours (ear, tail bites) per group was counted during 3×5min
observations once per week. Data were analysed using mixed model equations and binomial
logistic regression. At group level, AB pigs were more likely to have tail (OR = 1.70; P =
0.05) but less likely to have ear lesions than NO pigs (OR = 0.46; P<0.05). The number of
ear bites (21.4±2.15 vs. 17.3±1.61; P<0.05) and fights (6.91±0.91 vs. 5.58±0.72; P = 0.09)
was higher in AB than in NO pigs. There was no effect of treatment on health deviations and
the frequency of these was low. Removing AB from the feed of weaner pigs had minimal
effects on health and welfare indicators.