Effect of removal of antibiotics from the diet on the performance of negative behaviours in weaner pigs

To evaluate the effects of removing antibiotics (AB) from the diet of 1st and 2nd stage weaner pigs on the performance of negative behaviours.

Weaned pigs in a total of 12 groups of 35 pigs each, had in-feed AB removed (NO; n=6) or maintained in the diet (AB; n=6). Groups were observed 1 day/wk between 0900 and 1300h for 3x5min periods each and all occurrences of fights, head knocks, tail, flank and ear biting behaviour were recorded. Additionally, room temperature (RT) and CO₂ concentrations were measured once/wk. Body weight (BW) was recorded when pigs were weaned (i.e. moved into the 1st weaner stage accommodation) and on transfer to the 2nd stage weaner accommodation where groups were split and housed in 24 groups of c. 17 pigs each (AB; n=12 and NO; n=12). Behaviour observations were conducted in a similar manner except that groups were observed for 3x2.5min periods. To account for these changes data from the 1st and 2nd stages were analysed separately. Pen was the experimental unit. Data were analysed using linear mixed model equation methods. Stocking density, BW, RT and CO₂ were included as linear covariates. Group within treatment was included as a random effect.

Treatment had no effect on tail and flank biting during both stages (P > 0.05). In the 1st stage, both ear biting (21.4 ± 2.15 vs. 17.3 ± 1.61 no./5min; P < 0.05) and the no. of fights (6.91 ± 0.91 vs. 5.58 ± 0.72; P=0.09) were higher in AB than in NO pigs. The frequency of tail biting increased with time in the 1st stage (P < 0.05). The no. of fights increased from the 1st to the 2nd wk and reduced in the following wks (P < 0.05). During the 2nd stage, the no. of fights and head knocks increased with time (P < 0.05). Ear, tail and flank biting increased from the 1st to the 3rd wk and reduced in the last week (P < 0.05). In pens with a higher frequency of flank biting during the 1st stage the stocking density (P < 0.05) and RT (P < 0.05) was higher. Additionally, pigs in pens where a higher frequency of ear biting was observed were heavier (P < 0.05). There was an increase in the no. of fights and incidences of ear biting with every 1ºC increase in RT during the 1st stage (P < 0.05); however, the opposite result was observed during the 2nd stage (P < 0.05).

Removing AB from pigs’ diet during the weaner stages had a minimal effect on the performance of negative behaviours. The lower no. of fights and ear biting in NO pigs could be associated with reduced competition for access to feed arising from lower growth rates in these animals. This is supported by the fact that more ear biting was observed in pens where pigs were heavier.

Disclosure of Interest: None Declared.