Two experiments were designed to determine the nitrogen and amino acid digestibilities of plant protein sources (potato protein concentrate, soy protein concentrate, soy protein isolate, linseed meal, sunflower meal, cottonseed meal, canola meal, and camelina meal) fed to growing pigs. In each experiment, barrows were surgically fitted with a simple T-cannula at the distal ileum and fed four experimental diets and a N-free diet based on a replicated 5 x 2 crossover arrangement with five diets and two feeding periods.

Key Findings:

• In the first experiment, the apparent  ileal digestibility (AID) and standardized ileal digestibility (SID) of nitrogen were similar for soy concentrate and soy isolate and greater than linseed meal (P < 0.05);
• In the second experiment, sunflower meal, cottonseed meal, canola meal, and camelina meal were fed to 42-kg barrows to determine their AID and SID of amino acids. The AID and SID of nitrogen and most  amino  acids were not significantly different for sunflower meal and canola meal; and
• Cottonseed meal had lower AID and SID for nitrogen and the essential amino acids compared with the other protein sources (P < 0.05).

The researchers concluded that the digestibility of nitrogen and amino acids vary greatly among oilseed meals. The digestibility of potato protein concentrate was greater than that of the two soy protein ingredients which had similar protein digestibilities. The other protein meals, linseed, canola, sunflower and cottonseed had both lower crude protein levels and protein digestibilities. (Editor’s note: This research supports the role of soy protein in supplying needed amino acids in diets of the growing pig. Soy protein normally has amino acid digestibilities values higher than other commonly used plant protein ingredients. Feed formulators find soybean meal very competitive based on its availability, composition and price.

Table 1. Analyzed nutrient composition of the ingredients

Table 2. Apparent ideal digestibility of nitrogen and amino acids in test ingredients

Table 3. Standardized ideal digestibility of nitrogen and amino acids in test ingredients