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Low tannin content sorghum can substitute other cereal grains used in swine diets but often growth performance of pigs fed sorghum-based diets may not be comparable to that of corn-based diets. However, when available, sorghum may help to reduce feeding costs in growing-finishing diets. Kafirin, the prolamin storage protein in sorghum grains, has relatively low levels of basic amino acids, especially Lys with poor protein digestibility due to the hydrophobicity and disulphide crosslinking of kafirins, which is nowadays what most limits the use of sorghum in non-ruminant species. It has been reported that proteases are able to break the disulphide bounds increasing protein digestibility of sorghum. Therefore, the objective of this study was to determine the effect of protease on growth performance, nutrient digestibility, and gut health of pigs fed sorghum based diets at late nursery and grower stages. A total of 144 pigs with 18.4 ± 2.3 kg initial body weight (BW) at 6 wk of age were used in a 40-d trial. Pigs were randomly allotted to 4 experimental treatments (12 pens per treatment, 3 pigs per pen) in a 2 x 2 factorial arrangement (corn or sorghum basal diets, and 0 or 0.05% protease) with sex and initial BW as blocks. Experimental period had phase 1 (d 1 to 21) and phase 2 (d 22 to 40). About 65% (phase 1) and 72% (phase 2) of cereal grains were used in corn or sorghum based diets. Both grains were ground at the same screen sieve (0.4 mm). Body weight and feed intake were recorded weekly. On d 35, serum was collected to quantify tumor necrosis factor-a (TNF-a) and malondialdehyde (MDA). Titanium dioxide (0.3%) was used as an indigestible marker for an additional 4 d feeding. On d 40, 32 pigs (8 pigs per treatment) were euthanized to collect digesta from jejunum and ileum (for viscosity and apparent ileal digestibility), tissues (for morphology) and mucosa samples (for TNF-a and MDA) from duodenum, jejunum, and ileum.
Replacing corn with sorghum in the diet increased (P < 0.05) overall average daily gain (from 756 to 787 g/day) and average daily feed intake (from 1,374 to 1,473 g/day), reduced (P < 0.05) overall gain:feed ratio (from 0.553 to 0.537) without affecting apparent ileal digestibility. Pigs fed diets with sorghum had lower (P < 0.05) MDA content in serum (from 14.61 to 6.48 mmol/L) and jejunum (from 1.42 to 0.91 mmol/g protein), and showed a reduced (P < 0.05) villus height (from 492 to 396 mm) and crypt depth (from 310 to 257 mm) in jejunum. Dietary protease supplementation improved (P < 0.05) apparent ileal digestibility of crude protein (from 81.8% to 86.0%), decreased MDA level (from 1.20 to 0.98 mmol/g protein) in duodenum, and increased (P < 0.05) the ratio of villus height to crypt depth (from 1.08 to 1.21) in duodenum.
It can be concluded that the use of sorghum to completely replace corn in pig diets could enhance growth and feed intake, which may be potentially explained by a reduction of oxidative stress, whereas feed efficiency was compromised. Supplementation of protease improved protein digestion and maintained gut health, independently of the nature of the cereal used in the diet (sorghum or corn).
H. Chen, S. Zhang, I. Park, S. W. Kim (2017). Impacts of energy feeds and supplemental protease on growth performance, nutrient digestibility, and gut health of pigs from 18 to 45 kg body weight. Animal Nutrition 3: 359-365. https://doi.org/10.4148/2378-5977.7457
