M. C. Walsh

Nutritional and metabolic implications of replacing cornstarch with D-xylose in broiler chickens fed corn and soybean meal-based diet.

&NA; Effects of substituting cornstarch with D‐xylose on growth performance, nutrients digestibility, serum metabolites, and expression of select hepatic genes involved in glucose and lipid metabolism were investigated in broiler chickens. A total of 360 one‐day‐old male Ross chicks were fed 3 diets (n = 24; 5 chicks/cage) for 21 days. A control corn‐soybean meal‐based diet with 25% cornstarch was formulated to meet specifications. Two additional diets were formulated by substituting cornstarch with 5 or 15% D‐xylose w/w. Growth performance and digestibility by index method were determined in 12 replicate cages. Birds in these replicates had free access to feed and water, the BW and feed intake (FI) were monitored weekly and the excreta samples were collected on d 18 to 20. The other 12 replicates were used for blood and liver sampling by serial slaughter. On d 18, baseline (t0) birds were sampled following a 12 h overnight fasting and birds allowed 30 min access to the feed; samples were subsequently taken at 60, 120, 180, 240, and 300 min post feeding. Serum metabolites (glucose, xylose, and insulin) were assayed at all time points, whereas expression of hepatic transcripts was evaluated at zero, 180 and 300 min. Xylose linearly reduced (P < 0.05) FI, BWG, gross energy digestibility, and feed conversion ratio (FCR) but increased (P < 0.05) serum xylose level. Serum glucose and insulin levels were higher (P < 0.05) in the post‐fed state compared with baseline, irrespective of treatments. There was an interaction (P < 0.05) between diet and sampling time on the expression of hepatic genes. At t0, xylose linearly increased (P < 0.05) the expression of pyruvate carboxylase, Acetyl Co‐A acethyltransferase 2 (ACAT2), and glucose transporter 2. Xylose linearly reduced (P < 0.05) the expression of ACAT2 at 300 min post feeding. In conclusion, 5% or more xylose reduced growth performance and utilization of nutrients linked to hepatic enzymes and transcription factors involved in glucose and lipid metabolism.

Effects of a 3 strain -based direct-fed microbial and dietary fiber concentration on growth performance and expression of genes related to absorption and metabolism of volatile fatty acids in weanling pigs

Effects of a -based direct-fed microbial (DFM) on growth performance, plasma tumor necrosis factor ɑ (TNFɑ), relative gene expression, and intestinal VFA concentrations in weanling pigs fed low- or high-fiber diets were evaluated. Two hundred pigs (initial BW: 6.31 ± 0.73 kg) were allotted to 1 of 4 dietary treatments (5 pigs per pen and 10 pens per treatment). Treatments were arranged in a 2 × 2 factorial design with 2 diet types [low-fiber (LF) or high-fiber (HF)] and 2 concentrations of DFM (0 or 60 g DFM/t of feed). The DFM contained 1.5 × 10 cfu/g and was obtained from Danisco Animal Nutrition-DuPont Industrial Biosciences, Marlborough, UK. Phase 1 diets were fed for 2 wk post-weaning and phase 2 diets were fed over the following 29 d. Low fiber diets contained corn and soybean meal as main ingredients and HF diets contained corn, soybean meal, corn distillers dried grains with solubles (7.5 and 15.0% in phase 1 and 2, respectively), and wheat middlings (10.0%). Pigs and feed were weighed at the start and at the end of each phase, and ADG, ADFI, and G:F were calculated. At the conclusion of phase 2, blood was collected from 1 pig per pen and 1 pig per pen was sacrificed. Cecum and rectum contents were analyzed for VFA, and tissue samples were collected from the ileum, cecum, rectum, and liver to determine expression of genes related to absorption and metabolism of VFA using quantitative reverse transcription-PCR. Results indicated that feeding HF diets reduced ( ≤ 0.05) ADFI and ADG of pigs compared with feeding LF diets. Pigs fed DFM diets had improved ( ≤ 0.05) G:F compared with pigs fed non-DFM diets. Pigs fed LF diets had greater ( ≤ 0.05) BW at the end of phase 2 compared with pigs fed HF diets. The concentration of VFA in rectum contents was greater ( ≤ 0.05) in pigs fed LF diets than in pigs fed HF diets. The expression of in the rectum of pigs fed HF diets was greater ( ≤ 0.05) than for pigs fed LF diets, and pigs fed DFM-containing diets had an increased ( ≤ 0.05) expression of in the liver. Pigs fed HF diets had greater ( ≤ 0.05) concentrations of urea N in plasma compared with pigs fed LF diets, but dietary fiber and DFM had no effect on plasma concentration of TNF-ɑ. In conclusion, the -based DFM improved overall G:F of weanling pigs, but pigs fed LF diets had greater final BW than pigs fed HF diets.

Nutrient and fiber utilization responses of supplemental xylanase in broiler chickens fed wheat based diets are independent of the adaptation period to test diets2

ABSTRACT The effects of adaptation (AD) to xylanase‐supplemented diets on nutrient and fiber utilization in 21‐d‐old broilers were investigated. Six treatments, arranged in two levels of AD (starting at d 0 or d 14 of age) and three levels of xylanase (0 or 2,500 or 5,000 xylanase units/kg feed) were used. All diets had 500 phytase U/kg and 0.3% TiO2 as indigestible marker. A total of 384 d old male broiler (Ross 308) chicks were divided into two groups. The first group was assigned on weight basis to 24 cages (8 chicks per cage) and randomly allocated to the diets from d 0. Birds in the second group were reared on a commercial starter diet in the same room for 13 d. On d 14, the birds were individually weighed, assigned on weight basis to 24 cages (8 chicks per cage), and randomly allocated to the diets. Birds had free access to experimental diets and water. Excreta samples were collected from d 18 to 21. On d 21, all birds were euthanized to access ileal digesta. There was no interaction (P > 0.05) between AD and xylanase on the apparent ileal digestibility (AID) and apparent retention (AR) of components. The main effect of AD was such that the birds exposed to diets for 7 d (d 14 to 21) had higher (P < 0.01) AID of energy than those exposed for 21 d (d 0 to 21). In contrast, birds exposed to diets for 21 d had higher (P < 0.05) AMEn and AR of neutral detergent fiber. Xylanase improvements (P < 0.01) in the AID of energy and AMEn were dose dependent and coincided with linear improvements (P < 0.05) in the AID of nitrogen, fat, and starch. In conclusion, xylanase improvements on retention of fiber and nutrients were independent of AD (7 or 21 d) suggesting that the xylanase effects are not transitional. Greater retention of fiber with longer AD is suggestive of possible microbial adaptation.

Dietary D-xylose effects on growth performance, portal nutrient fluxes, and energy expenditure in growing pigs

Xylanase is commonly added to pig diets rich in arabinoxylans to promote nutrient utilization and growth. However, high doses of xylanase could release high amounts of xylose in the upper gut, which could have negative nutritional and metabolic implications. However, the amount of xylose to elicit such adverse effects is not clear. Thus, two experiments were conducted to investigate the effects of dietary xylose on the growth performance and portal-drained viscera (PDV) fluxes of glucose (GLU), urea-N (BUN), insulin production, and O2 consumption in growing pigs. In Exp. 1, 64 pigs (21.4 ± 0.1 kg BW), housed as either two barrows or gilts per pen (eight pens per diet) were used to determine the effects of increasing levels of D-xylose (0, 5, 15, and 25%) in a corn-soybean meal-cornstarch-based diet on pig growth performance in a 28-d trial. Cornstarch was substituted for D-xylose (wt/wt) in the control diet. BW and feed intake were monitored weekly. D-xylose linearly reduced (P < 0.05) final BW, ADG, and G:F but not ADFI. However, final BW, ADG, and G:F of pigs fed 15% D-xylose did not differ from pigs fed 0% D-xylose. Thus, the results suggested that pigs could tolerate up to 15% dietary D-xylose. In Exp. 2, six gilts (22.8 ± 1.6 kg BW), fitted with permanent catheters in the portal vein, ileal vein, and carotid artery, were fed the 0% and 15% D-xylose diets at 4% of their BW once daily at 0900 h for 7 d in a cross-over design (six pigs per diet). On d 7, pigs were placed in indirect calorimeters to measure whole-animal O2 consumption and sample blood simultaneously for 6 h from the portal vein and carotid artery after feeding to assay GLU, O2, BUN, and insulin concentrations. Net portal nutrients and insulin production were calculated as porto-arterial concentration differences × portal blood flow (PBF) rate, whereas PDV O2 consumption was calculated as arterial-portal O2 differences × PBF. Diet had no effect on postprandial PBF, insulin production, and portal BUN flux and O2 consumption. Pigs fed 0% D-xylose had greater (P < 0.05) postprandial portal and arterial BUN concentrations, and portal GLU concentration and flux than pigs fed 15% D-xylose diet. In conclusion, feeding growing pigs a diet containing 15% D-xylose did not reduce pig performance or affect PDV energetic demand but reduced GLU fluxes.