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Although most of the proteins in soybean meal are easily digested, some of them, such as glycinin and β-conglycinin, are difficult to digest especially for newly weaned piglets. Previous studies have shown that these proteins can damage intestinal morphology and impair immune function in newly-weaned pigs. Keratinase is a broad range protease which hydrolyzes different protein substrates including proteins containing cystine disulfide bonds, thus it is reasonable to hypothesize that dietary supplementation with keratinase could improve the amino acid utilization and performance of weaned piglets. Therefore, two experiments were conducted to investigate the in vitro ability of keratinase to hydrolyze soybean glycinin and β-conglycinin and to evaluate the in vivo effects of keratinase when included in corn-soybean diets with different levels of crude protein and fed to nursery pigs. In experiment 1, a saturated keratinase solution (1 ml) was added to two blank controls of either glycinin or β-conglycinin resulting in the hydrolysis of 94.74% glycinin and 88.89% β-conglycinin. In experiment 2, 190 pigs (8.3 ± 0.63 kg BW) were allotted to one of four treatments in a 2 × 2 factorial. The effects of crude protein (19 vs. 22%) and keratinase (0 vs. 0.05%) were studied. Pigs were fed the experimental diets for 21 d.
Weight gain and feed conversion ratio were improved (P < 0.05) with keratinase supplementation while feed intake was reduced (P < 0.05). Keratinase supplementation increased (P < 0.05) the apparent total tract digestibility of dry matter, energy, crude protein and phosphorus. Keratinase supplementation also increased n-butyric acid in the cecum and colon, lactobacilli and total anaerobe counts in the colon as well as the ratio of villus height to crypt depth in the ileum (P < 0.05). Additionally, fecal score, ammonia nitrogen and branch chain volatile fatty acids in the colon, E. coli and total aerobe counts in the colon, crypt depth in the jejunum and ileum as well as serum interleukin-1 and interleukin-6 concentrations were also decreased (P < 0.05) by keratinase supplementation. A reduction in dietary crude protein decreased (P < 0.05) colon ammonia nitrogen concentration and cecal propionic acid and branch chain volatile fatty acid concentrations. In addition, cecal E. coli counts, colon total anaerobe counts, ileal crypt depth, and serum interleukin-1 and interleukin-6 concentrations were also decreased (P < 0.05) with the reduction of dietary crude protein. With the exception of fecal scores, there were no significant interactions between crude protein and keratinase.
This study provides evidence that dietary keratinase supplementation improved nursery pig performance by improving intestinal morphology and ecology, thus improving nutrient digestibility and alleviating the inflammatory response.
D Wang, XS Piao, ZK Zeng, T Lu, Q Zhang, PF Li, LF Xue and SW Kim, 2011. Effects of keratinase on performance, nutrient utilization, intestinal morphology, intestinal ecology and inflammatory response of weaned piglets fed diets with different levels of crude protein. Asian-Australasian Journal of Animal Science, 24(12): 1718-1728