Low birthweight pigs are on a different growth trajectory from their normal birth weight litter-mates and as a consequence they may need to be fed differently, if they are to show compensatory gain, according to Ilias Kyriazakis and colleagues of Newcastle University in the UK.

The objective of their experiment, published in the current issue of Journal of Animal Science was to determine if low birthweight pigs will respond to a higher amino acid:energy diet, in a manner similar to the response of normal birthweight pigs whose bodyweight gain has been previously reduced as a result of feed restriction.

The experiment was a 3×2 factorial with 180 pigs and six replicates. Treatments comprised of three bodyweight categories:

• NU = normal birthweight fed unrestrictedly (1.7 to 2.0kg)
• NR = normal birthweight but fed restrictedly from days 49 to 63 and
• L = low birthweight (≤1.2 kg)

Two diet specifications given from days 63 to 91 (high or standard amino acid:energy ratio).

In period 1 (days 0 to 49), pigs were selected within 24 hours of birth and cross-fostered into litters by birthweight (11 or 12 piglets). Pigs were weaned on day 28 and kept in their litters until day 49.

In period 2 (days 49 to 63), litters were split to form two treatment groups consisting of five pigs each: NR pigs received restricted amounts of feed (600g per day) with the remaining NU and L pigs fed ad libitum on a conventional diet. The aim was for NR and L pigs to have the same bodyweight by day 63.

In period 3 (days 63 to 91), groups within litter were randomly allocated to a high or standard amino acid:energy ratio diet.

Bodyweight on day 63 was 25.8, 21.2, 21.8kg (0.381 SED) for NU, NR and L pigs, respectively.

By day 91, there was no difference in the bodyweight of NU and NR pigs (P>0.05) but L pigs still weighed less (P<0.001).

There was a significant effect of bodyweight category and diet specification during period 3 on the average daily gain and gain:feed ratio of pigs (P<0.05), with NR pigs exhibiting higher average daily gain and gain:feed ratio than L and NU pigs.

For gain:feed ratio only, there was a tendency towards significance for an interaction (P=0.057) with NU and NR pigs having an improved gain:feed ratio on the high specification diet but L pigs did not.

Average daily feed intake was similar for all bodyweight categories and diets from days 63 to 91. However, both L and NR pigs consumed more feed than NU pigs relative to their bodyweight but only NR exhibited higher average daily gain than NU pigs.

Kyriazakis and colleagues say their results suggests that a higher specification diet post-weaning may not improve the performance of low birthweight pigs. However, previously restricted normal birthweight pigs were able to exhibit compensatory growth and were more efficient when fed a higher specification diet.

Reference

Douglas S.L., S.A. Edwards and I. Kyriazakis. 2014. Too late to catch up: A high nutrient specification diet in the grower phase does not improve the performance of low birth weight pigs. J. Anim. Sci. 92:4577-4584. doi: 10.2527/jas.2014-7793

October 2014