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Impact of dietary protein and dried citrus pulp contents on gut morphology of weanling pigs
One hundred and eight barrows weaned at 21 d (5.82 ± 0.96 kg initial BW) were used to determine the effects of dietary CP and dried citrus pulp (DCP; rapidly fermentable carbohydrate source) contents on small intestinal morphology. Pigs were blocked by initial BW and randomly assigned to 1 of 4 treatments with 9 replicate pens per treatment and 3 pigs per pen in a randomized complete block design. Treatments were arranged in a 2 x 2 factorial, with 2 CP contents (high- and low-CP diets) and 2 DCP contents (0 and 7.5%, as-fed basis). The high-CP diets consisted of feeding 20 and 21% CP contents (as-fed basis) throughout phase I (0 to 14 d) and phase II (14 to 28 d), respectively. For the low-CP diets, CP contents were reduced by 4% units as compared with the high-CP diets in both phases. Dietary AA contents were balanced by supplementation with crystalline AA, such as L-Lys, DL-Met, L-Thr, L-Trp, L-Val, and L-Ile, to maintain an ideal AA pattern. On d 7 and 28 postweaning, 1 pig per pen was euthanized to collect duodenum, jejunum, and ileum samples for morphological evaluation. Data were analyzed as repeated measures using the MIXED procedure of SAS. There were no CP x DCP interactions for duodenal, jejunal, and ileal morphology on d 7 and 28 postweaning. Dietary treatments did not change duodenal and jejunal villus height. Pigs fed the low-CP diet, regardless of DCP inclusion, tended to have greater crypt depth (256.0 and 271.6 ± 5.81 μm for high- and low-CP diets, respectively; P = 0.08) and had decreased villus:crypt ratio (1.61 and 1.46 ± 0.04 for high- and low-CP diets, respectively; P = 0.05) in the duodenum on d 7, but not on d 28 postweaning. Decreasing dietary CP content also increased crypt depth (211.7 and 228.7 ± 3.98 μm for high- and low-CP diets, respectively; P = 0.03) and tended to decrease villus:crypt ratio (1.85 and 1.63 ± 0.06 for high- and low-CP diets, respectively; P = 0.08) in the jejunum on d 7, but not on d 28 postweaning. Neither CP content nor DCP inclusion altered ileal morphology on both d 7 and 28 postweaning. In conclusion, feeding diets containing 7.5% DCP does not affect gut architecture of weanling pigs. However, low-CP AA-supplemented diets were detrimental to intestinal morphology of pigs on d 7 postweaning.
Keywords:
fiber, intestinal structure, nursery pigs