By Kiah M. Gourley, Jason C. Woodworth, Joel M. DeRouchey, Mike D. Tokach, Steve S. Dritz and Robert D. Goodband, Kansas State University
Encouraging feed intake in lactating sows is one of the most critical factors in achieving maximum productivity in the farrowing house. Increased feed intake is associated with improved litter performance and sow reproductive performance. It is important that diet composition does not deter maximum lactation feed intake, and one of the possible deterrents could be soybean meal concentration.
Previous studies that investigated increasing lactation lysine concentrations (by also increasing soybean meal concentration) observed a decrease in feed intake as total lysine increased. While the researchers hypothesized the decrease in intake was due to elevated serum urea nitrogen levels and varying branch chain amino acid ratios across their experimental diets, the soybean meal concentration also increased from 12.6% to 48.5% of the diet. In order to meet the standardized ileal digestible lysine requirement of the high-producing sow, both soybean meal and crystalline lysine are typically added to the diet. However, is there a maximum concentration of soybean meal that should be considered?
The objective of the current study was to determine if the soybean meal concentration in lactation diets affects sow performance and feed intake. A total of 131 sows (Line 241; DNA, Columbus, Neb.) were used at the Kansas State University Swine Teaching and Research Center. On Day 112 of gestation, sows were weighed and moved into the farrowing house. Dietary treatments were corn-soybean meal-based and consisted of three concentrations of soybean meal (25%, 30% or 35% of the diet). L-Lysine hydrochloride was decreased in the diets as soybean meal increased in order to formulate all diets to 1.05% SID lysine. Other feed-grade amino acids (methionine, threonine, tryptophan, valine) were added as needed to maintain a similar ratio to lysine. Sows were hand-fed 6 pounds of dietary treatments from Day 112 until farrowing, and then received dietary treatments ad libitum from farrowing to weaning.
Increasing soybean meal concentration increased sow body weight loss and tended to increase sow backfat loss from farrowing to weaning. Sow average daily feed intake from Day zero to 7 was similar across treatments. However, from Day 7 to 14, Day 14 to wean, and overall, average daily feed intake decreased as soybean meal concentration increased (Figure 1). Litter count at Day 2 and weaning were similar, thus there was no evidence for piglet survivability to be influenced across dietary treatments.
Litter weights on Day 2 and weaning, as well as litter average daily gain were similar regardless of dietary treatment (Figure 2). This would suggest modern sow genotypes will support high litter growth, even when feed intake is limited. The greater body weight loss and backfat loss observed with sows fed the high soybean meal diet in this trial would support this conclusion. No difference in sow wean-to-estrus interval was observed.
In summary, increasing soybean meal concentration from 25% to 35% decreased voluntary feed intake in lactating sows, with the greatest magnitude of change occurring after 30%. Interestingly, there was no evidence for feed intake to be affected in the first seven days after farrowing. This suggests the decreased feed intake is not a result of initial palatability or the transition from a relatively low soybean meal level in the gestation diet compared to the lactation diet. There was no impact on litter growth or wean-to-estrus interval. However, sows fed diets with 35% soybean meal had the greatest farrow-to-wean weight loss and backfat loss which could impact future reproductive performance or longevity within the herd.