Improper heat treatment of soybean meal affects the intestinal integrity of broiler chickens and flock performance, according to a study by researchers at the University of Georgia (UGA).

Ana Maria Villegas Gutierrez, a graduate research assistant at UGA who led the study, said improper heating can negatively affect nutrient digestion, absorption and metabolism.

Unprocessed soybean meal contains anti-nutritional factors when fed to various livestock and poultry species. An optimal heating process is used to eliminate these anti-nutritional factors, but improper heating can either be ineffective or can burn the meal, altering its nutritional profile.

In research presented at the 2022 International Poultry Scientific Forum (IPSF), UGA poultry-science researchers reported on the effect soybean meal processing conditions have on growth performance and intestinal integrity in broiler chickens vaccinated for coccidiosis.

Study details

The research team subjected three commercial soybean meal batches to different heat treatments — extruder temperatures of 182° C, 199° C or 154° C for normal/control, overcooked or undercooked soybean meals, respectively — and fed the resultant meals to a total of 1,860 male Cobb 500 broiler chicks that had been vaccinated at 1 day of age with a commercial coccidia vaccine via coarse spray.

“Increasing processing temperature ensured reduction of trypsin inhibitor, protein dispersibility index and potassium hydroxide solubility (a measure of protein quality in soybean meal),” the researchers explained.

Each treatment was fed to 10 pens of 62 birds from 0 to 35 days of age. Soybean meal was fed as a fixed inclusion in the diet, which notably soybean meal varied by crude protein by 49.2%, 47.9% and 46.1% among the control, overcooked and undercooked meals, respectively.

Interesting results

According to the researchers, intestinal permeability increased in birds fed the overcooked soybean meal (P < 0.05). On days 14, 28 and 35, overcooked soybean meal depressed weight gain and feed intake, and increased the feed conversion ratio (P < 0.05).

In addition, the undercooked soybean meal decreased the villus height: crypt depth ratio in the jejunum on day 14 and reduced bodyweight gain in days 0 to14 and 0 to 35 periods compared to the soybean meal control group.

The relative weights of the right pectoralis major muscle also decreased significantly in 35-day-old birds fed overcooked soybean meal (P < 0.05).

The researchers noted that the adverse effects of overcooked soybean meal on bodyweight gain were driven by digestible amino acid intake, which was lower (P < 0.05) for lysine, methionine plus cysteine and threonine in the overcooked treatment compared to the normal and the undercooked treatment groups.

For more on this study, see the 2022 IPSF proceedings (abstract M60, page 22).