A newly weaned pig’s digestive system undergoes a large conversion when moving from a liquid to a dry diet. The goal of nutritionists is to help the pig transition from weaning into the nursery phase with adequate growth without incurring excessive diet cost. Some ingredients and diet formulation techniques help the pig counteract some of the normal gut changes that occur at weaning.
For example, adding lactose at 15% to 20% in the post-weaning diet provides a highly digestible energy source that increases lactic acid production, which lowers gastric pH. The use of pharmacological levels of zinc (1,500 ppm to 3,000 ppm) and/or copper (125 ppm to 250 ppm) for approximately 21 days post-weaning also promotes growth and can decrease diarrhea. High levels of soybean meal immediately post-weaning (over 18% to 20%) can cause transient hypersensitivity when the immune system reacts to an unfamiliar protein source. However, the second diet fed post-weaning often can contain 22% to 25% soybean meal after the initial exposure to soybean meal in the first post-weaning diet.
Think About Amino Acids
From an amino acid perspective, an important dietary attribute to minimize gut challenge and diet cost is to reduce the
dietary crude protein through the optimal inclusion of crystalline amino acids. Reducing crude protein decreases the quantity of fermentable protein entering the large intestine, which lowers post-weaning diarrhea. Diets for newly weaned pigs are often formulated in a range of 1.35% to 1.45% standardized ileal digestible [SID]. Diets higher in SID lysine often maximize piglet growth but diets formulated at 1.35% SID lysine decrease the level of more expensive protein sources, have minimal effect on pig performance and decrease feed cost.
When using diets with lower SID lysine, the correct levels of other amino acids relative to lysine are crucial.
Suggested ratios relative to lysine are 58% for methionine and cysteine, 63% for threonine, 68% to 70% for valine,
53% for isoleucine (60% if high levels of blood products are used) and 18% to 20% for tryptophan.
Producers do not want to feed lower levels of valine, isoleucine and tryptophan in nursery diets as these amino acids are important for driving feed intake.
Specific amino acids (like glycine or glutamine) appear to meet the need for nonessential amino acids and might have specific roles for gut development.
Consider Lowering Crude Protein
Another method to decrease the post-weaning challenge is to lower the crude protein level in the diet. Reducing the crude protein content lowers the need for all intact specialty protein sources (i.e. plant- or animal-based). Presenting the newly weaned pig with a high quantity of protein decreases the ammonia concentration in the small intestine and urea nitrogen and volatile fatty acids in the ileum. Historically, lowering the crude protein level in the diet usually corresponded with reduced growth performance because the minimum requirement for the fourth, fifth or sixth amino acids (often tryptophan, valine or isoleucine) or nonessential amino acids that have a role in gut development (arginine, glutamine or glycine) were not met.
Modern Diets are Better
This is not the case with today’s modern diets. Research trials and field data have demonstrated that performance can be maintained with a reduced crude protein level in the diet when amino acids are correctly balanced.
This is accomplished by using commercially available and economical crystalline amino acids (lysine, methionine, threonine, tryptophan, valine) to replace intact protein sources.
*Editor’s Note: Authors of this paper are with Kansas State University, Manhattan, Kan., and represent the K-State Applied Swine Nutrition Team: Joel DeRouchey, Mike Tokach, Bob Goodband, Steve Dritz and Jason Woodworth. For more information, go to: www.ksuswine.org.