Responses in egg shell quality to sodium chloride supplementation of the diet and/or drinking water

1. Supplementing the drinking water of 50-week-old laying hens with sodium chloride (NaCl) concentrations between 0.5 and 2 g/l for 7 weeks significantly increased the incidence of egg shell defects and significantly decreased egg shell quality. Dietary NaCl concentrations between 0 and 2 g/kg had little effect on this response. 2. At similar total NaCl intakes egg shell defects were much greater when the NaCl was obtained from the drinking water rather than from the diet. 3. Hens producing eggs with defective shells as a result of receiving saline drinking water failed to recover the ability to lay eggs with good shells after 8 weeks on normal water. 4. The increased incidence of shell damage was not related to decreased food intake or increased egg weight or production.     

Chloroanisole residues in broiler tissues

The relative tissue concentrations and total bird levels of chloroanisoles in commercial broilers reared on litter are reported. The levels observed at either 4 or 8 weeks of age are well below those quoted as inducing taint development in cooked birds. Although the highest concentrations of chloroanisoles occurred in bone and adipose fat the greatest contribution of chloroanisoles to “whole bird” levels was found in edible tissue. However, this was predominantly pentachloroanisole which is unlikely to cause a taint problem since it has a much higher taint threshold than tetrachloroanisole.     

The influence of tungsten on the molybdenum status of poultry

1. Large doses of tungsten, administered to the chick either by injection or by feeding, increased tissue concentrations of tungsten and decreased tissue concentrations of molybdenum and tissue activities of xanthine dehydrogenase.

2. The rate of loss of large doses of tungsten from the liver occurred in an exponential manner with a half‐life of 27 h.

3. When tungsten was administered to chicks fed on a semi‐synthetic diet containing abnormally low concentrations of molybdenum, the activity of hepatic xanthine dehydrogenase was reduced to negligible levels.

4. The alterations in molybdenum metabolism resulting from the administration of large doses of tungsten to the chick appears to be the result of tungsten toxicity and not of molybdenum deficiency.

5. Deaths from tungsten toxicity occurred when tissue concentrations of tungsten were increased to approximately 25 μzg/g liver. At this tissue tungstencon centration the activity of xanthine dehydrogenase was zero.     

Aspects of lipid and carbohydrate metabolism, dietary biotin and fatty liver and kidney syndrome in broilers.

Two experiments were performed to investigate the biochemical changes associated with FLKS. A diet reported to induce FLKS was fed with or without supplementary biotin to broilers. In experiment 1 various stresses were applied to the birds. 2. In experiment 1 mortality from FLKS was 6% and in experiment 2 nil. Stress had little effect on the induction of the syndrome. 3. There were no significant differences due to diet in any of the variables examined in apparently normal birds. 4. Birds affected by FLKS showed the typical changes of increased liver and kidney weights and lipid contents but hepatic enzyme activities did not differ significantly from those of normal birds except that malate dehydrogenase (decarboxylating) (NADP) activity was significantly decreased. 5. Despite the low content of biotin in the unsupplemented diet (57 mug/kg) liver biotin content was not low in birds fed on this diet. 6. The results suggest that the incidence of FLKS is not related solely to dietary biotin content.     

Comparison between concentrated complete diets and self‐selection for feeding sexually‐maturing pullets at hot and cold temperatures

1. Pullets in late growth and early lay were maintained at hot (25° to 35°C) or cold (6° to 16°C) ambient temperatures and either fed complete diets or allowed to self‐select nutrients from separate energy‐ and protein‐rich foods.

2. Manipulating the metabolisable energy (ME) and/or nutrient density (ND) of complete layer diets failed to improve egg output at hot temperatures to that obtained at cold temperatures.

3. At both temperatures self‐selection increased protein, but not ME, intake. This increased egg output and body weight gain at the hot, but not cold, temperatures. At the hot temperatures pullets fed by self‐selection were the only ones to gain weight between sexual maturity and 28 weeks of age.

4. Nutrient intake patterns, related to each pullet's physiological age of sexual maturity, identified distinctive changes in protein intake and the selected protein: ME intake ratio of pullets fed by self‐selection. Pullets attempted to maintain a preferred protein:ME intake ratio, irrespective of the markedly different intakes of ME and protein at the two temperatures.

5. Pullets trained to self‐select nutrients from separate energy‐ and protein‐rich foods are better able to sustain egg output and body weight at sexual maturity when food intake is limited by high ambient temperatures.     

Characterisation of midgut digestive proteases from the maize stem borer Busseola fusca

BACKGROUND: Insect damage is a major constraint on maize production. Control of Busseola fusca (Fuller) in sub‐Saharan Africa is relatively ineffective; the major larval digestive enzymes were characterised with a view to developing future control strategies. RESULTS: Using BODIPY‐FL Casein, maximal activity was at pH 9.5, with six protease forms visualised by gelatin‐PAGE. Synthetic substrates and diagnostic inhibitors demonstrated the presence of serine proteases. Chymostatin was a potent inhibitor of general proteolysis (90%), providing strong evidence for the presence of chymotrypsin; it also caused significant inhibition (>95%) with SA₂PFpNA as substrate. The I₅₀ values for chymostatin with casein and SA₂PFpNA were 0.0075 µM and 0.06 µM respectively. Z‐Phe‐Arg‐pNA activity was inhibited by chymostatin and TLCK (50 and 30% respectively), suggesting the presence of trypsin‐like activity. BApNA hydrolysis was also strongly inhibited by chymostatin and TLCK (92 and 75%), suggesting trypsin activity, while SBBI, PMSF, pepstatin and E‐64 had no significant effect. Interestingly, SBBI (I₅₀ = 0.39 µM ) and SBTI both inhibited general proteolysis by approximately 70%, suggesting that SBBI's dual inhibitory role makes this inhibitor a potentially useful candidate for expression in maize for control of B. fusca. CONCLUSION: These results provide a basis for the rational design of insect‐resistant transgenic maize expressing protease inhibitors. Copyright © 2008 Society of Chemical Industry     

The effects on liver metabolism of administering excesses of biotin to immature pullets and laying hens.

1. The administration of a ten-fold excess of biotin to immature chicks and a 25-fold excess to laying hens had no adverse effect on growth rate, liver weight or liver lipid content. 2. There were no marked effects of excess biotin on glutamate-metabolising enzymes but the specific activity of ATP citrate lyase was decreased.     

The influence of environmental temperature, age and sex on the digestibility of amino acids in growing broiler chickens

The ability of the broiler chicken to metabolise energy and to digest and absorb amino acids increased from 30 to 50 d of age. Although sex had no major effect on metabolisable energy or amino acid digestibilities at these ages, the influence of environmental temperature on amino acid digestibilities appeared to be sex-related, there being decreased digestibilities of most amino acids at higher temperatures in female but not male birds.