Intestinal starch and energy digestibility in broiler chickens fed diets supplemented with α-amylase

Dietary starch is the major energy source for broiler chickens; therefore, relevant information on its intestinal utilization is important. The present study was designed to evaluate intestinal starch and energy digestibility of broiler chickens fed diets supplemented with α-amylase. A total of 240 day-0 male broiler chicks were randomly assigned to 3 nutritionally adequate corn-soybean-based experimental diets comprising 3 levels of α-amylase supplementation (0, 80, or 160 KNU/kg diet). Each treatment comprised 8 replicate cages of 10 birds each. At day 21 after hatching, digesta was collected from 4 intestinal sites: the anterior jejunum (AJ), posterior jejunum (PJ), anterior ileum (AI), and posterior ileum. Increasing α-amylase supplementation linearly improved (P < 0.01) overall BW gain and feed efficiency of the birds. There were linear and quadratic (P < 0.01) responses of increasing α-amylase supplementation on starch and energy digestibility at the PJ and AI. The total tract digestibility of starch increased (P < 0.05) with increasing α-amylase supplementation. Starch disappearance and digestible energy (kcal/kg) linearly increased (P < 0.01) with digesta flow from the AJ to PJ as dietary α-amylase supplementation increased. There were linear (P < 0.01) and quadratic (P < 0.05) effects of increasing α-amylase supplementation on the villus height in the jejunum. The viscosity of the jejunal digesta decreased (P < 0.05) with increasing dietary α-amylase supplementation. The results from this study showed the efficacy of exogenous amylase in improving growth performance and starch and energy digestibility in broiler chickens. Furthermore, the digestibility of starch and energy and the impact of the exogenous amylase were higher at the PJ than other intestinal sites.

Additivity of apparent and standardized ileal amino acid digestibility of corn and soybean meal in broiler diets

A total of 144 male Ross 308 broiler chickens were used in a digestibility bioassay to determine the additivity of apparent or standardized amino acid (AA) digestibility values for corn, soybean meal (SBM), or a mixture of corn and SBM. Following the receipt of a standard commercial starter diet from days 1 to 21, broilers were divided into 4 treatments (6 cages per treatment; 6 birds per cage) and received semi-purified diets based on corn, SBM, or a mixture of corn and SBM or a nitrogen-free diet (for the estimation of basal endogenous AA losses). Apparent and standardized ileal AA digestibility values were determined on day 28 and the measured values for the mixture of corn and SBM were statistically compared to calculated values based on the digestibility of the individual raw materials and their concentration in the mixed diet. The use of apparent ileal AA digestibility values for single ingredients resulted in an underestimation (P < 0.05) of the digestibility of the mixed feed for nitrogen, Lys, Arg, Thr, Asp, and Gly. Correction of apparent digestibility values to standardized values entirely corrected the underestimation in the mixed feed and resulted in a predictable linearity from single ingredients to the mixed diet. It can be concluded that standardized ileal AA digestibility values are more additive than apparent values and should be used, where possible, to enhance the accuracy of feed formulation and reduce both the diet cost and the environmental impact of nitrogenous pollution.

Thymidine phosphorylase and dihydropyrimidine dehydrogenase protein expression in colorectal cancer

It is essential for actively proliferating cells to increase their rate of DNA synthesis to progress through the cell cycle. This is reflected in the increased uracil usage that is a common feature in solid tumours. Thymidine phosphorylase (TP) anabolises formation of pyrimidine nucleosides available for DNA synthesis, whereas dihydropyrimidine dehydrogenase (DPD) catabolises the degradation of pyrimidine bases, thereby reducing levels of uracil and thymine available for DNA synthesis. In addition, tissue levels of TP or DPD have been associated with the clinical efficacy of pyrimidine anti-metabolites commonly used in the treatment of colorectal cancer. There is little information, however, on the relative expression or degree of co-ordinated regulation of either protein in primary or metastatic colorectal cancer. DPD and TP protein levels were measured in 15 primary colorectal carcinomas, 10 colorectal liver metastases and 25 adjacent uninvolved tissues. DPD was reduced in 67% (10/15) of colorectal tumours (mean tumour/normal = 0.52) and in all liver metastases (mean tumour/normal = 0.41) compared with the corresponding normal tissue. In contrast, TP was increased in 80% (12/15) of colorectal tumours (mean tumour/normal = 18.91) and in all metastases (mean tumour/normal = 3.70). TP and DPD protein expression were highly variable in uninvolved and tumour tissues. The ratio of TP:DPD was higher in 87% of colorectal tumours and in all liver metastases compared with the adjacent uninvolved tissues. This suggests the presence of co-ordinated regulation of these pyrimidine metabolic enzymes and offers a strategy for optimising the use of pyrimidine-based chemotherapy.