Summer Carcass Weight Dip

DDGS can be used successfully in swine diet formulations, but they cannot be used at a level greater than 10% in a summer feeding program without a significant reduction in carcass weight gain. Ingredients that increase dietary fiber content (NDF), such as DDGS, corn germ meal and wheat midds reduce feed intake. The extent to which feed intake declines is dependent on the specific dietary level, with intake reduction being slightly greater in the growing phase than in the finishing phase. Excessive levels of DDGS in growing diets (greater than 10%) and in late-finishing (greater than 15%–20%) pig diets will negatively affect growth, especially during the summer.

There are some large-scale studies conducted in production systems that have shown a benefit from limiting the amounts of DDGS fed during the summer months, in order to prevent a reduction in intake and average daily gain (ADG). Increasing SBM does not reduce feed intake. The feeding matrix used by one production company to eliminate summer carcass weight dip is shown below, with diets being less expensive than traditional summer diets.

Note that the maximum levels of L-lysine shown in the table are applicable to all seasons and do not vary with limits on SBM or dried distillers’ grains with solubles (DDGS). Optimal L-lysine maximums have been determined in a number of commercial systems, but not all nutritionists are aware of this work and the performance effects. A minimum DDGS level is suggested based on field reports of improved bowel health.

Diet Matrix for Maximum Growth During Summer Heat Stress

The summer program involves a suggested minimum SBM and maximum DDGS content to minimize or prevent the carcass weight dip (see S3.Q1). The DDGS restriction is important because there is a doserelated reduction in feed intake, irrespective of source. However, a certain but greatly reduced level of DDGS is important to gut health. Growing and finishing pigs will consume 4%–8% less feed due to heat, and dietary fiber reduces intake even further. The diet matrix shown in S3.Q1 consists of corn, higher levels of SBM, some DDGS for gut health and no fat. Increasing amino acid levels is often recommended to compensate for reduced feed intake; however, research has not proven this to be beneficial, unless amino acids are already below their required levels.

Recent changes in the cost of fats and oils have made it more difficult to justify the use of these ingredients based on benefit-over-feed cost. The SBM diet matrix eliminates the need for fat. To reiterate, the most important factor in carcass growth recovery is to not reduce feed intake in the first place.

Due to ambient temperature differences, the various “effective temperature” comfort ranges for each phase must be considered. In the Corn Belt region, putting summer diets in place by May and continuing through the month of September is recommended. In warmer regions, such as the Southeast and Southwest, putting summer diets in place in April may be more appropriate.

A mitigating factor is swine respiratory disease (SRD) prevalence. If producers have experienced a winter/ spring challenge, then a carcass weight decline can emerge before it gets hot enough to reduce feed intake. This early start of carcass weight decline due to SRD becomes a calibrating factor for beginning the summer minimum SBM program to promote carcass growth. For example, in the Midwest, April may be a prudent choice to avoid creating a carcass weight dip that is difficult to overcome economically.

A gender-by-season interaction has not been observed, but barrows will consistently consume more feed and grow faster than gilts. Boars have a higher protein accretion rate and lower feed intake in the early growth phases; thus, they will require higher amino levels (15%–25%) than barrows.