EFFECT OF DIETARY-PROTEIN AND SUPPLEMENTAL SOYBEAN OIL FED DURING LACTATION ON SOW AND LITTER PERFORMANCE THROUGH 2 PARITIES

The effects of protein and/or energy intakes on sow and litter performance during a 21 day lactation were examined through two parities. A 2 x 2 factorial design with four replications per parity was used. Dietary treatments consisted of two dietary protein levels (14 or 16%) and two levels of soya-bean oil (0 or 3%). One hundred and fifty-eight primiparous sows were utilized in Parity 1. Eighty-seven sows completed both parities. All females received 1.8 kg day-1 of a 14% crude protein (CP) diet during gestation. Sows were allotted to lactation treatment in Parity 1 and remained on the same treatment in Parity 2. No protein x soya-bean oil interaction occurred for any of the criteria measured in either Parity 1 (P > 0.24) or Parity 2 (P > 0.07). Also, no diet by season interaction occurred (P > 0.18) for any criteria measured in either parity. In Parity 1, dietary protein or soya-bean oil had no effect (P > 0.12) on sow weight loss, sow backfat loss, pig survivability, weaning litter size, weaning litter weight, average pig weaning weight, or percentage of sows returning to estrus by Day 7 post-weaning. Also, neither dietary protein nor soya-bean oil had any effect on serum concentrations of urea, creatinine, or free fatty acids. Feed intake was depressed (P < 0.05) for sows receiving 3% soya-bean oil. However, caloric intake was not affected (P > 0.59) by dietary addition of soya-bean oil. Dietary protein intake had no effect (P > 0.47) on daily feed intake or on the percentage of sows returning to estrus by Day 14 post-weaning. However, fewer sows on the 16% protein diet had returned to estrus by Day 28 post-weaning (P < 0.08). Fewer sows fed a diet containing 3% soya-bean oil returned to estrus by Day 14 or Day 28 following weaning (P < 0.03). In Parity 2, neither dietary protein level nor addition of 3% soya-bean oil had any effect (P > 0.10) on sow or litter performance, with the exception that sows receiving 3% soya-bean oil had a longer interval from wearing to estrus (P < 0.05). In conclusion, a 14% protein diet without added fat was adequate during the first and second lactation for the sows used in this experiment.