Effects of feather cover and insulative jackets on metabolic rate of laying hens

Thermal resistance of chicken (Gallus domesticus) plumage: a comparison between broiler and free-range birds

1. We compared Ross chickens reared under broiler and free-range conditions to see whether there was a difference in thermal resistance of the plumage. 2. There was no difference in resistance to heat loss attributable to rearing environment for plumage from the back and leg but there was a significant difference in the pectoral region. 3. Free-range birds had a thicker plumage and a higher total resistance to heat transfer in the pectoral region, despite showing a lower resistance per unit depth than broiler birds. The pectoral plumage was more heavily soiled in broiler birds, which is the most likely explanation for the higher resistance per unit depth. 4. We suggest that behavioural selection of microclimate is likely to be a more important determinant of heat balance in free-range birds than intrinsic plumage adaptations.

Effects of ambient temperature and restricted feeding on the growth of feathers in growing turkeys

1. Male turkeys were reared to 6 weeks of age at 15 degrees C and 26 degrees C and fed ad libitum or restricted to 0.5 of the body weight of birds fed ad libitum. Basal metabolic rate was determined by indirect calorimetry at an ambient temperature of 20 degrees C. 2. Turkeys at 15 degrees C were lighter than those kept at 26 degrees C. Feather lengths and weight were similar in both groups. Fasting heat production corrected for both metabolic body size and activity was greater in turkeys reared at 15 degrees C than those at 26 degrees C. 3. Cranial breast feathers were significantly longer in restricted birds than in those fed ad libitum in contrast to a proportional decrease in the lengths of other feathers of 0.1 to 0.3. Feather weight as a proportion of body weight was 0.072 in restricted turkeys compared with 0.046 in birds fed ad libitum. There was no difference in basal metabolic rate between ad libitum and restricted turkeys. 4. It was concluded that feather growth was maintained in preference to body and muscle growth and that rearing birds at 15 degrees C did not improve breast feather cover. It is suggested that the growth of breast feathers in turkeys fed ad libitum is impaired.

Effect of plumage renewal after induced moulting on subsequent laying efficiency and persistence

1. Brown egg layers and dwarf broiler breeder females were force-moulted by different diets. The relationship between the extent of feather replacement and subsequent laying performance was studied. Some brown hens were subjected to metabolic experiments in order to compare post-moult heat production in relation to moulting success. 2. The extent of moulting had a clear effect on the post-moult heat production, and the differences were still present after 6 months in the second year of laying. 3. The extent of feather renewal during moulting showed high and very significant rank correlations with efficiency of food utilisation during the subsequent laying cycle. These correlations were generally higher than those of other features of the moulting procedure (body-weight-loss, minimum weight, duration of pause in laying). 4. The long-term energetic implications of the extent of moulting play an important role in subsequent performances and the persistence of lay during the following year is related to the extent of feather replacement.

Effects of feather wear and temperature on prediction of food intake and residual food consumption

Heat production, which accounts for 0.6 of gross energy intake, is insufficiently represented in predictions of food intake. Especially when heat production is elevated (for example by lower temperature or poor feathering) the classical predictions based on body weight, body-weight change and egg mass are inadequate. Heat production was reliably estimated as [35.5-environmental temperature (degree C)] x [Defeathering (=%IBPW) + 21]. Including this term (PHP: predicted heat production) in equations predicting food intake significantly increased accuracy of prediction, especially under suboptimal conditions. Within the range of body weights tested (from 1.6 kg in brown layers to 2.8 kg in dwarf broiler breeders), body weight as an independent variable contributed little to the prediction of food intake; especially within strains its effect was better included in the intercept. Significantly reduced absolute values of residual food consumption were obtained over a wide range of conditions by using predictions of food intake based on body-weight change, egg mass, predicted heat production (PHP) and an intercept, instead of body weight, body-weight change, egg mass and an intercept.

Effects on productivity and aggressive behavior of laying hens of solid versus wire cage partitions and bird density

The effects of solid metal cage partitions or wire mesh cage partitions and two cage densities (5 or 7 birds/60.9 cm X 35.6-cm shallow cage) on production performance traits, aggressive behavior, and feather covering of White Leghorn layers were assessed from 20 to 60 wk of age. Type of cage partition had no significant effects on any of the traits measured. Higher cage density, however, was associated with significantly lower hen-day egg production, feed usage, final body weights, and feather covering. No differences were observed for egg weights, egg loss, mortality, or aggressive head pecking activity of birds housed in the two cage densities.

A new approach to recording plumage deterioration

1. Recording methods for the scoring of plumage wear are reviewed. 2. A new technique, distinguishing between feather tracts, the surface to which damage occurs and the degree of degradation to the feathers themselves is elaborated: a 5 step scale for degradation is applied to all appropriate fractions of 6 feather regions. After correcting for the normal feather weight in the respective areas, all 6 area values are summed to constitute an overall index of body plumage wear (IBPW).

Early egg production in genetically blind (rc/rc) chickens in comparison with sighted (Rc+/rc) controls

The impact of blindness on egg production was investigated by utilizing genetically blind chickens in a factorial experiment involving two genotypes (blind vs. sighted), two densities (1000 cm2 per bird vs. 2000 cm2 per bird), two flock sizes (1 male, 4 female female vs. 4 male male, 16 female female), and two replications (floor pens). Traits measured were number of eggs collected, egg weight, amount of feed taken from the feed troughs, body weight gain, fertility of eggs, feather pecking and comb damage scores, leukocyte count, plasma corticosterone level, and adrenal gland weight. During the 2-month experimental period, blind hens produced 12.7% more eggs (hen-day production) while requiring 44.1 g less feed per bird day compared to sighted hens. There was no significant difference in body weight gained between the two genotypes. Significant genotype X flock size and genotype X density interactions also indicated that the performance of the blind chickens was less affected by differences in density and flock size compared with sighted chickens. Other traits measured provided evidence that the blind chickens were less active, had better feather coverage, and were perhaps under less stress than sighted ones.