Experimental Procedures
A total of 74 sows (Yorkshire x Landrace or Yorkshire), involving a total of 192 farrowings over four parities, were used in a 3 x 2 factorial experiment. The feeding of different dietary lysine levels and sources, and the addition of a simple carbohydrate added to the lactation diet was evaluated. The first factor evaluated three different lysine diets, while the second factor evaluated the effects of added dextrose (0 or 10%). A basal diet was formulated using corn and SBM to meet the NRC lysine (total) requirement (0.90%) for both first-parity and multiparous sows (Table 1). First-parity sows were fed the basal level (B), or the basal plus an additional 0.30% lysine level from either SBM (B+NL), or from a combination of 0.15% lysine from SBM and 0.15% lysine from synthetic lysine (B+SL). During parities 2 through 4, the same basal level (0.90% lysine) was fed, but the B+NL treatment contained 0.15% added lysine from SBM, while the B+SL treatment groups were fortified only with 0.15% synthetic lysine.
The gestation diet was formulated to contain 15% crude protein during parity 1 and was fed at 4.4 lb/day, while a 13% crude protein diet was fed at 4.6 to 5.1 lb/day from parity 2 through 4 (Table 1). The amount fed increased by parity. Sows were randomly assigned to treatments and fed their experimental diets upon entering the farrowing room at approximately 5 days prefarrowing. Lactation length was 21 days during parity 1 and 17 days during parity 2 through 4.
Sow body weights and backfat thicknesses were collected at breeding, 109 days postcoitum, farrowing, and at weaning. Sow lactation feed intakes were determined at weekly intervals, however only total and daily feed intakes are presented.
At 109 days, postcoitum sows were moved to individual farrowing crates and fed their treatment diets until farrowing. Feed intake was subsequently increased from 4.4 lb to ad libitum access by 4 days postpartum. In order to assess the effects of the lactation diets more completely, litter size was equalized across treatments by 3 days postpartum. Pig weights were collected at farrowing, 3 days postpartum, and at weaning. Colostrum and milk were collected from all functional glands at farrowing and weaning and analyzed for milk fat and protein contents. Blood samples were collected from sows at weaning and analyzed for PUN concentration.
At weaning, sows were moved to individual gestation crates, checked twice daily for estrus and artificially inseminated twice within 24 hours of estrus detection. Sows not exhibiting estrus within 10 days of weaning were removed from the experiment; however estrus detection continued to a maximum of 30-days postweaning.
Statistical analyses were performed using the General Linear Model Procedures of SAS (SAS Inst. Inc., Cary, NC) using a randomized complete block design. Individual sow and litter measurements were considered the experimental unit. Breed and group effects were pooled after it was determined that there were no effects on sow and litter measurements.