Introduction
A goal for the commercial swine producer is to provide a sufficient supply of nutrients during lactation in order to ensure that sows are in good breeding condition. Recent genetic emphasis toward selecting high-producing females has resulted in increased sow milk production and litter size. During the past decade, swine producers have reduced sow lactation lengths, but high culling rates (i.e. > 40%) continue to be a persistent problem. Although lactating sows should consume feed ad libitum, low feed intakes still occur in most sow herds.
High-producing sows compensate for dietary inadequacies by mobilizing body reserves when production demands are high. Depletion of body reserves, particularly fat can affect subsequent rebreeding performance. Often times the more productive animals are prematurely culled from the herd because of poor body condition. When formulating lactation diets for high-producing sows, the emphasis should be to maximize genetic productivity and sow longevity.
Previous research has demonstrated that first-parity lactating sows consuming greater than 50 g lysine/day had improved litter gains and lower lactation weight losses (Johnston et al., 1993; Touchette et al., 1998). Although higher lysine levels can be achieved by increasing the dietary crude protein level, it can also be attained by the use of supplemental amino acids. Lysine is usually considered the first limiting (most deficient) amino acid in most corn-soybean meal diets for lactating sows. The addition of synthetic lysine alters dietary amino acid ratios, without increasing other amino acids. An imbalance, however, may cause other amino acids to become deficient. Recent research has demonstrated that valine may be the dietary amino acid most affected when synthetic lysine is added to sow diets (Richert et al., 1997).
There are other reports indicating that synthetic lysine also may have a detrimental effect on lactation feed intake (Libal et al., 1997). This might be due to the faster rate of lysine absorption relative to other dietary ingredients, particularly the carbohydrate component, and may result in inefficient utilization of the synthetic lysine source. Adding a highly digestible sugar to the diet, in combination with synthetic lysine, may improve feed intake and protein utilization.
This experiment evaluated the response of lactating sows fed various lysine diets and a simple sugar (i.e. dextrose). Lactation feed intake, and subsequent reproductive performance were evaluated using both primiparous and multiparous sows.