Effect of diets containing potato protein or soya bean meal on the incidence of spontaneously-occurring subclinical necrotic enteritis and the physiological response in broiler chickens.

1. An experiment was conducted to compare and explain the incidence of spontaneously occurring subclinical necrotic enteritis in broiler chickens that were fed on two practical broiler diets that differed in the major protein concentrates (soya bean meal or potato protein concentrates) and examine the relationships between the severity of the disease and the growth performance and physiological responses of the chickens. 2. A total of 840, 20-d-old birds were randomly allocated to 12 pens. Two maize-based nutritionally complete diets that either contained some potato protein or soya bean meal as the major protein supplement were fed for 16 d. Twelve birds were randomly sampled from each pen at the end of the feeding period and their blood sampled and intestinal tracts and livers dissected. 3. The birds fed on the potato protein diet had a significantly 7·7% lower feed intake and a significantly 7·8% lower growth rate compared with the birds fed on the soya-based diet. There were no significant differences in feed conversion efficiency or mortality. There were no differences in the determined apparent metabolisable energy concentrations, however, the apparent dry matter digestibility of the potato protein diet was significantly higher than that of the soya based diet and the apparent crude protein digestibility of the potato protein diet was significantly lower. 4. A significantly higher alpha toxin antibody titre was found in the birds fed on the potato protein diet compared with those fed on the soya protein diet. There was a significantly increased incidence of hepatic lesions in the birds fed on the potato protein diet compared with the birds fed on the soya diet. The mean incidence of intestinal necroses tended to be greater in the birds fed on the potato protein diet (23·6%) compared with the birds fed on the soya-based diet (15·3%). 5. There was a significant linear relationship between ileal digesta sialic acid concentration and serum alpha toxin antibodies, although there were a considerable number of outliers to this relationship. Measurement of sialic acid concentration may be a useful variable to indicate the severity of necrotic enteritis in broiler flocks.

The efficiency of energy retention of broiler chickens and turkeys fed on diets with different lysine concentrations.

1. An experiment determined the effect of 6 different lysine concentrations (40, 52, 58, 65, 90 and 130 g/kg CP) in two protein concentrations (210 and 260 g/kg) on the efficiency of energy utilisation of broiler chickens and turkeys. Ninety-six male Ross 308 broiler chicks and 96 male BUT Big 6 turkey poults were fed at 90% of ad libitum during a 12 d bioassay period. At the end of the bioassay, birds were slaughtered and carcase crude protein, fat and gross energy were measured and nutrient metabolisability determined. 2. Broiler chickens had lower AME and AME(N) than turkeys. AME was higher in the 260 g/kg than in the 210 g/kg protein diet; however, no difference was evident in AME(N) between any of the diets in both species. A significant species x lysine interaction indicated that the decrease in AME and AME(N) with increasing lysine was greater in turkeys than in broiler chickens. 3. Turkeys had lower weight gains and efficiencies of energy retention than broiler chickens. The effects of different lysine concentrations on growth and the efficiency of energy retention were significant and growth responses were quadratic but there were negative linear responses in the efficiency of energy retention in both species at both crude protein concentrations. The efficiency of energy retention was increased with decreasing lysine concentrations throughout the wide range of concentrations used in the experiment.

Different soil media for free-range laying hens.

1. A replicated experiment compared bird use, soil structure, grass wear and free-moving nematode populations in 4 different soil media (recycled vegetable compost, 90% recycled vegetable compost and 10% sand, re-used topsoil and sterilised topsoil) all with established grass swards within the range area of a large free-range laying hen unit. 2. The birds initially spent a greater proportion of their time on the two topsoil swards in comparison to the two compost-based swards. However, once the whole flock of hens had prolonged access to the different swards (unfenced areas) there were no significant differences in the number of birds that frequented the different sward types. 3. The two compost-based soil media had 33% fewer nematodes per g of dry soil compared to the two topsoil-based media. However, the rate of loss of grass from the subplots was greater with the two compost-based soil media; this was probably due to the greater porosity of these types of soil media.

Effect of enzyme supplementation of a rye-based diet on xylanase activity in the small intestine of broilers, on intestinal crypt cell proliferation and on nutrient digestibility and growth performance of the birds.

1. A study was undertaken to investigate the susceptibility to peptic digestion of exogenous xylanase (EC 3.2.1.8) from Trichoderma longibrachiatum, added to a rye-based diet for broiler chickens, in order to elucidate its possible site of action. 2. It was also designed to investigate the effects of the enzyme (plus exogenous protease EC 3.4-24.28) when added to a rye-containing diet (60% rye/kg diet) on crypt cell proliferation in the mucosa of the small intestine, on short chain fatty acid (SCFA) concentrations in the small intestine digesta and in portal blood and on nutrient digestibilities. 3. In Experiment 1, the enzymes were added at activities 10x and 30x those recommended in commercial practice, but in Experiment 2 the activities were the recommended levels. 4. A significant proportion (estimated to be 15 to 20%) of the xylanase added at the higher concentration (15,000 and 45,000 units/kg diet) remained active in the small intestine of the growing chicken. 5. The crypt cell proliferation rate in birds fed on the control diet (45 cells/2 h) was significantly higher than in birds fed on the diets supplemented with enzyme at the higher level (29 and 33 cells/ 2 h), but there was no significant effect on SCFA. In birds fed on the diet supplemented with enzyme at the commercial level there was no clear-cut effect on crypt cell proliferation but exogenous xylanase could be detected in the small intestine. Intestinal fluid viscosity was reduced and growth performance of the birds was improved by the supplementation with exogenous enzymes. 6. Part of the improvement in growth performance could be ascribed to a 25% increase in the digestibility of nitrogen and a doubling of the digestibility of fat.