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 perform ance during a 21 day lactation were examined through two parities. A 2 x 2 factorial design with four replications per parity was used. Diet ary 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 pr imiparous sows were utilized in Parity 1. Eighty-seven sows completed both parities. All females received 1.8 kg day-1 of a 14% crude protei n (CP) diet during gestation. Sows were allotted to lactation treatmen t in Parity 1 and remained on the same treatment in Parity 2. No prote in x soya-bean oil interaction occurred for any of the criteria measur ed 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 i n 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 survivabil ity, weaning litter size, weaning litter weight, average pig weaning w eight, or percentage of sows returning to estrus by Day 7 post-weaning . Also, neither dietary protein nor soya-bean oil had any effect on se rum concentrations of urea, creatinine, or free fatty acids. Feed inta ke was depressed (P < 0.05) for sows receiving 3% soya-bean oil. Howev er, 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 dail y 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 retur ned 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 fo llowing 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-bea n oil had a longer interval from wearing to estrus (P < 0.05). In conc lusion, a 14% protein diet without added fat was adequate during the f irst and second lactation for the sows used in this experiment.