The effect of nutrition on the reproductive performance of first-litter sows 4. The relative effects of energy and protein intakes during lactation on the performance of sows and their piglets

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Abstract
Eighty-eight first-litter sows were used in a factorial experiment to examine the effects of energy and protein intakes during lactation on subsequent performance. Some received either 45 MJ (E,) or 60 to 63 MJ (E2) digestible energy per day and either 508 to 511 (P,) or 703 to 815 (P2) g crude protein per day during a 28-day lactation.Sows on the E2P2 treatment lost less body weight during lactation than sows on the other three treatments (P < 0·05). Average live-weight losses during lactation were 21·8, 20·8, 17·8 and 9·6 kg for the E1P1, E1P2, E2P1, and E2P2 sows, respectively. The corresponding reductions in backfat measurements during lactation were 5·5, 7·9, 3·2 and 4·0 mm. Backfat losses were greater for sows given either moderate energy intakes or high protein intakes (P < 0·01).Neither protein intake nor energy intake during lactation affected subsequent ovulation rate, but piglets sucking sows given high protein intakes grew faster, particularly during the last week of lactation, than piglets sucking sows receiving low protein intakes (P < 0·05).Within 8 days of weaning, more sows given high intakes of protein during lactation exhibited oestrus than did sows which received lower intakes of protein (27/44 v. 14/44, x2 = 7·7, P < 0·01). Protein intake during lactation affected the nitrogen balance of sows in a similar way. The nitrogen balances were estimated during the 3rd week of lactation, and for sows given rations E1P1, E1P2, E2P1, and E2P2were -20·2, -11·5, -17·5 and -7·2 g/day respectively.