Dustbathing in fowls (eg chickens, Gallus gallus) consists of tossing the litter onto and between the fluffed feathers and subsequently enclosing it by flattening the feathers. The proximal contact between litters like sand and peat, and the integument is intensified by rubbing the body. This is not the case in wood-shavings which adhere to the distal plumage after tossing; rubbings in wood-shavings are frequently interrupted by reinitiated tossings. Lipids accumulate on the feathers and become stale during dust deprivation. Only baths in sand and peat are effective in removing excessive lipids from the proximal downy feather parts. Fluffiness of the down is highest in hens on peat, intermediate on sand and lowest on wood-shavings, while the reverse is true for the plumage surface temperature of the back Hens monitor the integumental lipid condition which becomes causally connected with bathing in the course of experiencing litter bathing effects. It is shown from the author's experimental study that hens naive of bathing in litter, and hens experienced with wood-shavings initially shifted bathing litters but finally preferred peat or sand (in that order) when peat, sand and wood-shavings were simultaneously presented Most of the hens experienced with bathing in sand did not shift to another substrate when presented with one. Recommendations are given concerning adequate dustbathing litter. A chronic deprivation of adequate litter leads to an uncontrollable condition of the lipids on the integument and an abnormal development of dustbathing. Such a deprivation therefore reduces animal welfare. Moreover, it is suggested to be costly.

Improving the fowl's natural ability to clear Salmonella from their body is important in reducing disease prevalence in poultry flocks, as recommended by a recent regulation of the European Commission. It may be efficient, as expected from estimation of heritability coefficients : 0.16 in chicks and 0.18 for global contamination of hens. The animal's age has to be considered since the genetic correlation between resistances at the two ages is negative. Selecting two series of divergent lines for increased or decreased resistance, after inoculation at one week of age (chick resistance) or at the peak of lay (adult resistance) confirmed the efficiency at least of selection for the adult resistance. In parallel, genes controlling variations to Salmonella resistance were researched and several QTLs identified in crosses between experimental lines and, for some of them, confirmed in commercial lines. Thanks to the derivation of a model of Salmonella propagation within a flock, it has been shown that a combination of vaccination and genetic selection can result in very low percentage of contamination.

Heat production (HP) and the intake and retention of energy and nitrogen were measured in growing broiler fowl kept at 32° and given diets with metabolizable energy contents from 8 to 15 MJ/kg and crude protein (N × 6·25; CP) contents of 130 and 210 g/kg. The temperature of 32° was chosen for comparison with earlier measurements at 20° to minimize heat produced for the maintenance of body temperature. The effects of diet composition were observed when the same birds were taken from 20 to 32°. The tendency for energy intake to increase with dietary energy concentration was less at 32 than at 20°. The lower heat increments measured for the high-fat diets did not, therefore, confer an increased ability to sustain higher energy intake at 32°. HP was about 17% lower at 32 than at 20°; the change in HP between 20 and 32° was not significantly influenced by diet composition. The absence of significant effects of diet composition on HP, combined with the significant trend in energy intake, produced significant differences (related both to dietary energy and dietary protein concentrations) in total energy retention and in the partition of retained energy between protein and fat. As at 20°, variation in energy retention and in the composition of retained energy were the main responses to variation in dietary CP concentration and energy intake; a significantly higher energy cost of unit protein accretion on the low-CP diets was insufficient to produce an elevation in total HP because the higher unit energy cost was balanced by a lower absolute rate of protein accretion.

An experimental model is described that was used for assessing in vivo effects in fowls of exogenous enzyme supplementation on the degradation of plant cell walls to metabolizable monosaccharide residues. It was based on tube-feeding U-14C-labelled cell-wall substrates, cellulose, spinach (Spinacia oleracea) or Festuca with and without enzyme treatments, and monitoring recovery of 14C radioactivity in exhaled carbon dioxide and excreta in the following 8 h. Normal digestion of cell-wall polysaccharides by endogenous microbial activity was also studied by pretreating birds with an antibiotic mixture intended to deplete their intestinal microflora. The results of this pretreatment appeared to confirm the existence of microbial degradation of cellulose in (conditioned) fowls. Judging from differences in 14CO2 production, effects of exogenous enzyme additions were greatly enhanced with all substrates by combining them with a wet pretreatment, thereby increasing the time-period available for them to act in aqueous conditions. However, estimations of digestibilities of cellulose, hemicellulose and pectin with dry and wet treatments, based on recovery of 14C in excreta, indicated that it was only cellulose digestion that was improved by the wet pretreatment. This suggests that degradation of cellulose, which appeared to be slowest, was limited by the dry treatments, whereas that of hemicellulose and pectin was not. Respective digestibilities of these three cell-wall components, from all treatments combined, were in the proportions 1:1.5:4·2.

A major benefit of supplementing non-ruminant feedstuffs with exogenous enzymes is presumed to be the degradation of plant cell-wall polysaccharides to metabolizable monosaccharide residues. In the present study, metabolic fates of (U-14C-labelled, 10 mM) glucose, galactose, mannose, xylose and arabinose were compared in the fowl, by measuring recoveries of 14C radioactivity in exhaled carbon dioxide, excreta and body tissues after administration either by wing vein (iv) or into the crop (ic). A further comparison was made with a tube-fed, enzyme-treated, U-14C-labelled cell-wall substrate, Festuca arundinacea and a final experiment tested possible competition for absorption between different cell-wall residues. Delays between iv and is treatments in recovery of 14C in CO2, which were assumed to reflect intestinal absorption, indicated that xylose was absorbed more slowly than glucose and galactose, but faster than mannose and arabinose. Total recoveries of 14C in CO2 and excreta over the whole test period indicated that metabolizabilities were highest with glucose, galactose and mannose, and lowest with arabinose. After testing, 14C recovery in caecal contents was highest with is arabinose, and recoveries in body tissues, with all sugar treatments, were in the order liver > breast and leg muscle > abdominal fat > plasma. Results with the Festuca substrate showed similar patterns of recovery in body tissues and confirmed an increase in metabolizability with addition of enzymes. The timing of the 14CO2 response with Festuca and a wet enzyme pretreatment was broadly similar to a ‘predicted Festuca’ response, based on the composition of the substrate and the measured responses with individual (ic) monosaccharides. There was no evidence of any competition for absorption or metabolism among cell-wall residues. It was concluded that glucose release from cellulose is potentially the most important product of cell-wall degradation to contribute to enzyme enhancement of metabolizable energy.

To test a possible influence of dietary fibre on intestinal sugar uptake, rates of absorption of 10 mm-d[U-14C] glucose and 10 mm-d-[U-14C] xylose were measured in either jejunum or (distal) caecum, by in vivo lumen perfusion, in immature female fowls preconditioned to a standard diet containing (g/kg) either 0, 100, 200 or 400 added dried grass, 200 powdered cellulose, or 200 grass with a polysaccharidase enzyme supplement. When birds were killed after perfusion, dimensions of (unperfused) parts of their alimentary tracts were determined, and recoveries of 14C radioactivity in some body tissues were compared with measured activities absorbed. On average, absorption of glucose was 1·9 and 1·2 times faster than xylose in jejunum and caecum respectively, although these differences varied with dietary treatment and order of perfusion. Increasing grass in the diet caused significant changes in xylose absorption rate in both jejunum and caecum, but only when it was perfused before glucose. With any one sugar and intestinal segment, mean rates of absorption were correlated positively with corresponding mean rates of fluid loss from perfusate. Although their influence on sugar absorption was not well defined, the dietary fibre treatments had more pronounced effects on gross dimensions of parts of the alimentary tract and, hence, potentially on total rates of absorption. Compared with the basal diet, addition of 100, 200 or 400 g grass/kg or 200 g cellulose/kg caused significant increases in small intestine length while 200 g grass/kg with supplementary enzyme did not, and combined caecal length increased with the 400 g grass/kg and the supplementary enzyme treatments. Absorbed 14C activity was recovered in plasma after jejunal perfusions but not caecal ones, whereas it was recovered in liver and in the flushed perfused segment after both types of perfusion. Since there was overlap in absorption rates between jejunum and caecum, this result suggests that the liver may be able to distinguish and treat differently compounds absorbed in the two regions.