Effect of temperature during induced moulting on plumage renewal and subsequent production

1. Four groups of 18 cages each containing 4 brown laying hybrids aged 79 weeks were formed by two levels of restriction of a moulting diet (lasting for 29 d) being applied at two moulting temperatures (11 degrees C and 29 degrees C, lasting for 56 d). 2. Low temperature-low feeding resulted in greatly retarded growth of remiges, but the final extent was similar in all 4 groups, and reached 4 to 5 new primaries (median value). Body-plumage of hens moulted at 11 degrees C was 25% heavier than of hens moulted at 29 degrees C. 3. Second year production variables (rate of laying, egg mass, efficiency of food utilisation) were greatly influenced by moulting temperature (low moulting temperature performing better), but not by feeding rate. 4. The persistence of the improved food utilisation is related to energetic consequences of improved plumage renewal during moulting at the lower temperature, which can be seen as an acclimatization effect.     

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.     

Fatness of laying hens and induced moulting regimens

1. A flock of laying hens was divided into two groups according to their fatness, which was estimated using abdominal fatness callipers.

2. A moult was induced in both groups by reducing day‐length and restricting food intake. The food restriction period lasted for 2, 3 or 4 weeks and the birds were given either 15 or 25 g of whole wheat/bird.

3. No differences were observed between the moulting treatments on post‐moult egg weights, shell strength or Haugh units, but maximum egg output (g/bird d) was obtained by the 4‐week food restriction period for the fat‐grouped birds but by the 3‐week food restriction for the lean‐grouped birds.

4. The birds restricted to 15 g wheat/bird d showed a more rapid regression of the ovary and oviduct, which may account for their increased egg numbers towards the end of the 22‐week laying period compared to the birds allocated 25 g/bird d.     

Hormonal changes associated with ageing and induced moulting of domestic hens

1. The effect of age on ovarian function was studied in 245-, 350-, 500-, 700- and 800-d-old Lohmann hens. The effect of three different methods for moult induction on ovarian function and corticosterone concentration was studied in 500-d-old hens. 2. No significant reductions in ovarian weight or in number of follicles before the age of 700 d were found. The ability to produce progesterone and oestradiol-17beta was unchanged up to the age of 700 d and the circadian secretion of these two steroids was identical in young (225 d) and old hens (600 d). 3. The effects of induced moulting by feed withdrawal (FW) and a high Zn (HZn) diet on body weight and ovarian function were very similar; those of a moderate Zn with low Ca (MZn/LCa) diet were smaller. 4. The first significant effect of moulting was a decrease in oestradiol-17beta plasma concentration (d 2). Plasma progesterone decreased more gradually than oestradiol-17beta, and reached a nadir on d 6 in FW- and HZn-treated hens and on d 9 in MZn/LCa-treated ones. 5. Hens treated with either FW or the MZn/LCa, but not those with the HZn diet, showed a very sharp rise in corticosterone concentration on d 2 of treatment. Thus the MZn/LCa diet was less efficient than the other treatments in induction of ovarian involution, but had a similar effect on stress induction, as indicated by increases in plasma corticosterone.     

Effects of induced moulting on immune responses of hens.

1. The potential for induced moult to be a stressor and therefore alter the immune response in hens was examined. Spent hens from White Leghorn and White Rock layer flocks were induced into a moult by withdrawal of food and the effects on the humoral and cellular immune responses of these birds were examined. 2. Lymphocyte numbers were lower in moulted birds compared with nonmoulted controls. 3. Antibody responses to sheep red blood cells or Brucella abortus antigen were largely unaffected. 4. The delayed type hypersensitivity response to the skin sensitiser dinitrofluorobenzene (DNFB) was depressed during the period of food withdrawal but recovered when feeding resumed. 5. Induced moulting probably has a negative effect on the cellular component of the immune system of the moulted birds.     

Group size and plumage damage in laying hens

1. Ninety‐one Shaver 288 laying hens were kept in groups of 1, 2, 4 or 6 birds per cage and were provided with a floor space of 1300 cm² for the single birds and 650 cm²/bird for the groups. The overall damage to the plumage of each bird was assessed at monthly intervals from 18 to 72 weeks of age.

2. Most of the plumage damage occurred during the first 24 weeks after caging and was attributed mainly to mechanical abrasion between the birds’ bodies and their cages. Little additional deterioration in feather cover occurred between 45 and 72 weeks of age.

3. The plumage damage of single birds was always less than that of birds kept in groups.     

Changes in luteinizing hormone-containing gonadotrophs after moulting induced by fasting and zinc in laying hens (Gallus domesticus)

The purpose of the present study was to investigate egg production performance, immunohistochemical (IHC) identification, localization and morphological characterization of moulted hen’s pars distalis luteinizing hormone (LH) gonadotrophs. This system has been validated for chicken LH by immunodetection of purified hormones on dot blots, western blotting and by specific labelling of cells on sagittal sections of chicken pituitaries. This study showed that egg production and egg weight increased significantly after zinc-induced moult when compared with fasting-induced moult. Luteinizing hormone-gonadotrophs are of numerous shapes and distributed throughout the adenohypophysis, with densely populated regions on the margins of pars distalis. Moulting of laying hens was associated with a significant increase in immunoreactive LH gonadotroph cell count and cell size, which peaked at the subsequent production stages. Zinc-induced moulting also caused a significant increase in LH gonadotroph cell size as compared with fasting-induced moulting. The nuclear size of LH-positive cells was distinct during decreased egg production. Our results validate the use of ovine LHβ antibodies for the IHC localization of chicken LH gonadotrophs. This technology was further applied to the characterization of the shape and morphological changes of gonadotrophs as a function of the egg production status of the birds.     

Production responses of layer strain hens to food restriction during rearing

Production responses of laying hens to food restriction during rearing were measured in two trials. Food was restricted by two methods: time restriction (TR, food continuously available for 24 to 30 h each 72 h) and proportion restriction (PR, daily allocations of about 60 to 70% of that consumed by ad libitum fed birds (F]. The rearing treatments were applied from 42 to 162 d and from 56 to 168 d of age in experiments 1 and 2 respectively. All birds were fed ad libitum in the laying period to 437 d and 476 d of age in experiments 1 and 2 respectively. Body weight was reduced significantly in both experiments by both methods of restriction, but more so by TR. Marked compensatory growth accompanied the high food intake following the end of food restriction. There was a significant increase in average egg weight concommitant with a change in the relationship between egg weight and age. Possibly this is due to an altered pattern of food intake at onset of lay.     

Localisation of MHC class II,lymphocytes and immunoglobulins in the oviduct of laying and moulting hens

1. Our aim was to determine the presence and numbers of immunocompetent cells in the oviduct of laying and moulting hens. Immunocompetent cells were localised by immunocytochemistry throughout the entire length of the oviduct.

2. In laying birds, MHC class II + cells were observed in the subepithelial and middle part of the stroma of all oviducal segments and the mucosal epithelium of the infundibulum and vagina. CD3 + cells were also localised in subepithelial and middle part of stroma as well as in mucosal epithelium of each oviducal segment. Bu‐lb + and IgG + cells were also observed in the epithelium and subepithelial and middle part of the stroma of all oviducal segments, though stroma of the magnum, isthmus and uterus contained few Bu‐lb + cells. IgA + cells were observed only in the mucosal epithelium of the magnum in small numbers.

3. In moulting hens, there were few numbers of immunocompetent cells in the mucosal epithelium of each oviducal segment, although CD3 + cells were observed in the infundibulum and vagina. In the subepithelial stroma, the populations of MHC class II + cells in the infundibulum, magnum and uterus, CD3 + cells in the infundibulum and vagina, as well as IgG + cells in each oviducal segment except for isthmus were smaller than in laying hens. In contrast, the number of immunocompetent cells in the middle part of stroma of moulting hens were equal to or greater than in laying hens.

4. These results suggest that the oviducal immune function is active in the surface tissues of the mucosa in laying hens, whereas it is reduced in moulting hens.     

Changes in eggshell conductance,water loss and hatchability of layer hens with flock age and moulting

1.?Changes in water loss, eggshell conductance and hatchability with flock age were monitored in layer hens in a commercial hatchery.

2.?Optimal water loss for maximal hatchability of layer eggs was found to be 12 to 13% of initial egg mass at d 18 of incubation.

3.?Mass specific water vapour conductance (GH₂Osp) increased linearly with flock age from 0·31 mg/(d·g·Torr) at the beginning of the first breeding season to 0·40 mg/(d·g·Torr) at its end after 77 weeks (=4·21 and 5·44 mg/(d·100 g·kPa), respectively).

4.?After forced moulting GH₂Osp increased from 0·35 to 0·41 mg/(d·g·Torr) (=4·76 and 5·58 mg/(d·100 g·kPa), respectively).

5.?The coefficients of variation of GH₂Osp increased with flock age from 14% at the beginning of the breeding season to 31% at the end of the second breeding season.

6.?In order to preserve normal incubation water loss for maximising hatchability, the humidity setting of an incubator should increase gradually, with flock age, from 53% RH to 66% RH in the first laying season and from 61% RH to 67% RH after forced moulting.

7.?A 3·5-fold increase (from 2 to 7%) in the difference between mean and median GH₂Osp of egg batches with flock age was found, indicating increasing frequency of microscopic cracks in eggshells with flock age. This has to be taken into account when setting the humidity regime in the incubator.     

Reducing stress during welfare inspection: validation of a non-intrusive version of the LayWel plumage scoring system for laying hens

1. The objectives of the present study were to validate a reduced, non-intrusive version (RLS) of the LayWel plumage scoring system in domestic laying hens with reference to complete, intrusive scoring (CLS) and to investigate the effect of these two scoring methods on corticosterone metabolite concentrations. 2. A total of 312 medium-heavy laying hens from 4 commercial hybrids kept in 24 floor pens were scored by two experienced teams. Another 150 hens from two hybrids kept in 6 pens were used for estimating scoring treatment effects on corticosterone metabolites in droppings. 3. Plumage scores were in general higher using the RLS method compared to the CLS method. The agreement between teams for plumage scores (CLS) were on a high (total score) to an excellent (single body part except breast and cloaca) level. 4. Birds subjected to CLS tended to have higher concentrations of corticosterone metabolites in droppings 2 h after scoring compared with birds in the control treatment (not scored). Birds subjected to RLS had intermediate concentrations. 5. It was concluded that a reduced version of the LayWel scoring system is a valid and reliable scoring method which tends to induce less stress to the subjects than the original procedure.     

An appraisal of moulting on post-moult egg production and egg weight distribution in white layer hens; meta-analysis

1. The aim of this study was to establish how different moulting methods and body weight losses influenced post-moult performance and USDA egg weight distribution.

2. Data on 5 laying flocks (#34–38) of the North Carolina Layer Performance and Management Test were used in this meta-analysis.

3. The moulting methods were non-fasted moulted (NF), short feed restricted (SF), 13-d feed restricted (FR), non-anorexic moult programme (NA), non-anorexic moult programme with low sodium (NALS) as well as non-moulting programme as control treatment. The percentages of targeted body weight loss during the moulting period were 20, 24, 25 and 30% of body weight at the end of the first egg production cycle.

4. Post-moult egg production and egg mass were influenced by all moulting methods. Maximum increase in post-moult egg production rate and egg mass occurred with FR and NF programmes, respectively, at 30% of body weight loss, compared to non-moulted hens. Non-fasting methods reduced mortality rate more effectively than fasting methods.

5. Moulting resulted in increases in percentage of grade A and decreases in percentage of grade B eggs. Non-fasting methods increased percentage of grade A eggs more effectively than fasting methods. Percentage of cracked eggs decreased in moulted rather than non-moulted hens and the lowest rate was associated with the NA programme.

6. Post-moult egg weight was not significantly influenced by moulting methods. However, percentage of body weight reduction affected egg weight. The optimum increment in egg weight was achieved by 24% body weight reduction.

7. Overall, non-fasting methods resulted in similar egg production compared with fasting methods. Considering post-moult mortality and USDA egg weight distribution, non-fasting methods, especially NF and NA programmes, performed much better than fasting methods, indicating that non-fasting moulting methods, which are better for animal welfare, are effective alternatives to fasting methods.     

Perch length in cages for medium hybrid laying hens

1. ISA Brown hens were housed as groups of 4 from 18 to 72 weeks in 24 cages 450 mm deep, each with a softwood perch of rectangular cross‐section fitted across the rear. There were 4 treatments, each with 6 cages: cage widths and perch lengths were 480, 520, 560 or 600 mm.

2. Daytime perching did not differ significantly between the treatments. At night, over the whole year, 81% of birds in the 480 mm cages and 86% in the 520 mm cages roosted on the perch. This figure reached about 95% in the 560 and 600 mm cages, significantly more at most ages than in the 480 mm cages.

3. Feather damage was slightly less, but claw problems slightly more, in the 2 wider treatments than in the 2 narrower treatments. Birds in the wider cages were calmer when approached or handled by humans than those in the narrower cages. This may have been associated with variation in space allowance between the treatments.

4. There was a trend for lower production in the 480 mm cages than in the other treatments which may have been associated with the reduced feeding space in this treatment. There were few other treatment differences in production traits.

5. The balance of the evidence from this study is that when perches are provided in laying cages for medium weight hybrids, 140 mm of perch space per hen is adequate. For the amelioration of a number of the welfare problems of conventional cages, provision of perches should be combined with other modifications.     

黄羽肉鸡与四川山地黑羽乌骨鸡杂交试验

用四川山地乌骨鸡作父本,黄羽肉鸡作母本进行杂交,杂交后代在生长速度、１２周龄累计料肉比等方面体现了极显著的杂种优势。屠宰性能得到普遍改善,胸腿肌率得到了显著提高,说明黄羽肉鸡能与四川山地乌骨鸡配套进行仿土鸡的商品生产。     

Effect of including whole oats into pellets on performance and plumage condition in laying hens housed in conventional and furnished cages

In an experiment including 2400 layers, a diet with 40% whole oats incorporated into 3 mm pellets (experimental diet) was compared with a complete diet, also as 3 mm pellets, but containing no whole oats (control diet). These diets were examined in conventional 3-hens cages and two furnished cage systems with 8 or 16 birds per group including nest, perches and litter. The effects of diet, rearing condition and cage system on performance, plumage condition, comb lesions and rear body wounds were studied. Furthermore, the effect of feed structure on gizzard characteristics and interactions with access to litter during rearing and laying periods were examined. The hybrids LSL and Shaver 2000 were included in the experiment. Egg production was lower (P<0.05) in furnished cages than in conventional cages. No difference in plumage condition was found between diets, but a significantly poorer plumage condition (P<0.05) was observed with increasing group size. Also, the frequencies of rear body (P<0.05) wounds increased as the group sizes increased, while no such effect was observed for comb lesions. Higher (P<0.05) feed consumption was observed in furnished cages than in the conventional, causing a corresponding increase (P<0.05) in feed conversion rate (FCR). Higher (P<0.05) FCR was observed for birds fed pellets with whole oats than the control. Whole oats also increased (P<0.05) the weight of gizzard and gizzard contents. For LSL, better (P<0.05) plumage condition was found for birds reared on a deep litter floor compared to cage rearing. It was concluded that no beneficial effect of replacing high amounts of ground oats with whole oats was observed. Genotype and rearing method may interact with housing system.     

Effect of method and phase of nutrient restriction during rearing on productive performance of light hybrid pullets and hens

1. An experiment was conducted to study the effect of method (low-lysine or quantity of food) and phase (starter or grower) of restriction during rearing on growth and laying performance in Leghorn hybrids. 2. A reduction in body weight gain was achieved by feeding pullets a low-lysine diet in either the starter phase (0-6 weeks of age: 4.0 g/kg digestible lysine) or the grower phase (7-18 weeks of age: 3.0 g/kg digestible lysine). 3. In each phase, the lysine restriction was compared with a daily food restriction, in which pullets received a quantity of food sufficient to pair-gain with their lysine-restricted counterparts. 4. The delay in onset of production was greatest in the lysine-restricted birds, for both phases of restriction. 5. Hens restricted during the grower phase laid heavier eggs than those restricted during the starter phase, despite having similar body weights at end of rearing. This effect was not influenced by the restriction method. 6. Production traits varied between pullets reared on different feeding strategies up to similar body weights at 18 weeks and onwards. It is concluded that body weight is not the only factor determining laying performance.     

Individual production differences do not explain cannibalistic behaviour in laying hens

1. Sixty-three laying hens were collected from 5 commercial farms experiencing outbreaks of cannibalism. It is known that cannibalistic behaviour varies strongly between hybrids and between individuals of the same hybrid. The aim of this study was to test specific hypotheses about the causation of cannibalism by comparing matched individuals varying in their cannibalistic behaviour. 2. To investigate feed efficiency, egg production and feed consumption, data were collected over 30 d. Nutrient deficiencies have been associated with outbreaks of cannibalism and we hypothesised that cannibals are more feed efficient than their flock mates and, therefore, more susceptible to transient nutrient deficiencies or imbalances that trigger cannibalistic behaviour. 3. Video recordings were made of victims of cloacal cannibalism and their matched controls during oviposition. Victims were expected to have longer oviposition durations and a higher incidence of short-term cloacal prolapses than controls, because the starting point for cannibalism is often suggested to be pecking at the red mucosa of the victim during, or just after, oviposition. 4. Oviduct swab samples were taken from surviving victims of cloacal cannibalism and their matched controls 4 weeks after the cannibalistic attack. If peck wounds provide a route for subsequent bacterial invasion of the reproductive tract, victims would be expected to have greater bacterial colonisation of the oviduct. 5. Mortality within each matched trio was recorded over a 23-month period after the cannibalistic attack. Victims that survived a cannibalistic attack were expected to have reduced longevity compared to controls and cannibals. This could occur if they developed secondary infections as a result of the cannibalistic attack, or if they had poorer health even before the attack. 6. No significant differences were found between cannibals, victims and controls in feed efficiency or any of the production variables measured. Victims of cloacal cannibalism did not expose their cloacal mucosa more, or for longer, than matched control hens during oviposition, and had no more bacteria in their oviduct. Victims tended to die sooner than their matched cannibals or cannibals during a 23-month period after a cannibalistic attack.     

The shell gland in laying and natural moulting commercial egg-type chickens: A histomorphological and ultrastructural study

The purpose of the present study was to determine the histological and ultrastructural changes in the luminal epithelium of the shell gland associated with natural moulting. Samples of the shell gland from laying (32 weeks old) and moulting (75 weeks old) hens were studied using histological, histochemical and electron microscopic techniques. In addition, TUNEL was used to demonstrate the distribution of apoptotic cells in the luminal epithelium of the shell gland. Autophagy, characterized by the presence of autophagosomes and autolysosomes, was evident in the early stages of degeneration in non-ciliated, ciliated and mitochondrial cells. The intermediate and advanced stages of regression in non-ciliated as well as mitochondrial cells occurred via apoptosis, while both apoptotic and necrotic ciliated cells were observed during the later stages of degeneration. The results of the present study suggest that a synergy of autophagy, apoptosis and necrosis is involved in the involution of the shell gland during natural moulting.