Genetic adaptation of White Leghorn hens to life in single cages

Specific adaptations of selected lines to their conditions of management were found for egg production, but not for several other traits, when hens of different selection histories were tested under both conditions. Floor selected sublines were superior to cage selected sublines in floor pens but inferior when both were tested in individual cages. The study involved three populations of two sublines in each of which selection for egg production had been practised over seven generations. Under one management birds from the three populations were intermingled in large floor pens; under the other, among individual cages.

The role of social dominance as expressed in competition for food was explored. Floor selected hens were the more dominant in floor pens as well as in paired tests in cages.     

Genetic and phenotypic parameters for monthly egg production in White Leghorn hens

This article reports genetic and phenotypic parameters of monthly egg production and the influence of Box‐Cox transformation on the parameters from a population of White Leghorns, selected for feed efficiency. A total of 6450 daughters of 180 sires and 1335 dams were analysed by restricted maximum likelihood (REML) using a multivariate animal model. The traits considered were monthly egg productions, cumulative production of the first 5 months (S5), cumulative production of first 10 months (S10), and survivor egg production in the first cycle (S12). Two sets of data were analysed: the original data and with the Box‐Cox method transformed data. The results indicated that there were no great differences in the estimates between untransformed and transformed data. The estimates of heritability for monthly egg production were high for the first period, decreased to reach the lowest during peak production, and increased to the end of lay. The estimates of heritability for cumulative records were generally higher than monthly records. Genetic and phenotypic correlations among monthly egg production totals were generally high for contiguous periods and then decreased as the interval between months increased. The highest genetic correlation between monthly records and S5 was for the second month of production, whereas the correlations between monthly production totals and S10 and S12 reached their peak at the sixth and eighth months of production, respectively.     

Co-segregation of behaviour and production related traits in an F3 intercross between red junglefowl and White Leghorn laying hens

In poultry breeding, selection for production traits may cause side-effects on the physiology and behaviour of the birds with a potential influence on animal welfare. Genetic associations between phenotypic traits can be studied in an intercross of two divergent breeds. In advanced generations, traits controlled by the same genes or by genes located close to each other will co-segregate. Our aim was to study if behavioural styles expressed by red junglefowl (n=26) and White Leghorn (n=26) in a social vs. exploration motivation test as well as breed-differences in contrafreeloading (CFL), an energy demanding feeding strategy, would co-segregate with production related traits in their F3 intercross progeny (n=78). The results revealed Leghorns to maintain closer social contact in the test, whereas junglefowl, which according to previous studies have also a higher degree of CFL, were more active and explorative. Furthermore, these behavioural differences correlated with several production related traits, such as growth and residual feed intake (RFI), in the F3 generation. F3 birds with higher levels of production related traits behaved in a fashion resembling Leghorns more than junglefowl. Both in parental animals and the F3 birds, the above effects were clearest among females. The results, thereby, suggest that selection for high production in fowl may simultaneously have side-effects on sociality and foraging. This could further influence the general capacity of birds to cope with environmental challenges such as exploring a novel environment. The genetic mechanisms underlying this co-segregation remain to be investigated.     

Effect of induced molting on heterophil function in White Leghorn hens.

This study was undertaken to determine the effects of induced molt on basal functional activities of heterophils from aging hens. For this purpose, heterophils from both molted and unmolted hens were examined by in vitro bioassays for functional responsiveness and efficiency. We evaluated the ability of the heterophils to migrate to chemotactic stimuli, phagocytize opsonized and nonopsonized Salmonella-enteritidis (SE), and generate an oxidative burst in response to inflammatory agonists. A significant (P < 0.001) heterophilia was found in the molted hens within 2 days after feed withdrawal and remained throughout the length of the experimental feed withdrawal period. No significant differences were found in the random migration of heterophils from either group. The chemotactic movement of heterophils from molted hens was not affected until 8 days after feed withdrawal when compared with heterophil chemotaxis from unmolted hens. A significant decrease in chemotaxis by the heterophils from molted hens was observed days 8-12 after feed withdrawal (P < 0.05). Significantly (P < 0.05) fewer heterophils from molted hens were able to phagocytize opsonized (59% vs. 38%) and nonopsonized (26% vs. 15%) SE within 2 days after feed withdrawal. Likewise, significantly (P < 0.05) fewer bacteria were phagocytized per heterophil from the molted hens when compared with the number of bacteria per heterophil from the unmolted hens. The oxidative burst of heterophils stimulated by either opsonized zymosan A or phorbol myristate acetate of heterophils from molted hens was significantly (P < 0.05) reduced when compared with that generated by heterophils from the unmolted hens. These results indicate that feed withdrawal to induce molt alters the number and function of peripheral blood heterophils. This decreased efficiency of heterophil functional activity appears to play a role in the increased susceptibility of molting hens to SE infections.     

Catecholamines in ovarian follicles during the ovulatory cycle of White Leghorn hens

Dopamine (DA) concentrations in the largest ovarian follicle (F1) showed significant decrease at 12 and 8 h prior to ovulation. Nor-epinephrine (NE) and epinephrine (E) concentrations in the F1, sampled at different times of the ovulatory cycle, were found to increase with the approach of ovulation time. However, the concentration of epinephrine in the F1 was low just after oviposition compared with the immediate two previous stages investigated. The concentrations of DA, NE and E in the second largest follicles (F2) did not vary significantly during the ovulatory cycle. Average concentration of DA was low and that of NE and E high in the F1 compared with the respective concentrations in the F2.     

Selection for egg shell strength in laying hens using shell membrane characteristics

1. Divergent selection for attachment strength between the shell membrane and the calcium shell was performed in a White Leghorn strain. Multivariate analysis was used to estimate genetic parameters for shell membrane measurements and shell thickness. The aim was to investigate the possibility of improving shell strength in laying hens by selecting for increased attachment strength.

2. A significant direct selection response for attachment strength was achieved. There was a favourable correlated selection differential in the frequency of cracked eggs which resulted in a nonsignificant but favourable, correlated response. Selection for a strong attachment resulted in a thinner egg shell, and vice versa. Heritabilities were all relatively high (0.30 to 0.70). Most of the genetic correlations were in agreement with the achieved correlated responses.

3. Two factors that probably contributed to the responses in egg shell thickness were an unfavourable genetic correlation between attachment strength and shell thickness, and natural selection against changes in attachment strength, in the form of increased mortality during incubation and hatching. Problems connected with breeding for increased shell strength are discussed.     

Effects of fasting and refeeding on structures of the intestinal villi and epithelial cells in White Leghorn hens

1. The fine structural alterations of villi and epithelial cells in each part of the small intestine were investigated in layer‐type hens fasted for 12 h to 20 d or refed for one day after each fasting period.

2. Within the first 24‐h‐fasting, villi of the duodenum showed a remarkable reduction in height and those of the jejunum revealed a gradual decrease; such a significant reduction of the villus height was not obtained in the ileum. After 36‐h‐fasting, villus height in each part gradually decreased with days of fasting.

3. All intestinal villus heights increased after only 1‐d‐refeeding of various kinds of diets following 3‐, 10‐, or 20‐d‐fasting. The duodenum especially rapidly recovered even after long‐term fasting of 20 d but the ileum showed very slow recovery, suggesting that the ileum seems to be inactive in absorptive function.

4. These variable alterations of villus height in the proximal intestine suggest that the higher intestinal absorptive ability is under the normal feeding, the more rapidly villus height is influenced by nutritional conditions.

5. Cell area and cell mitosis decreased after fasting, the latter showing a marked reduction. However, in spite of a remarkable decrease of cell mitosis in the proximal intestine after fasting, refeeding activated cell renewal and it soon reached control levels, demonstrating that the villus height mainly varied with the numbers of epithelial cells.

6. In the epithelial cells of the proximal intestine in chickens fasted for 20 d, large lysosomal autophagous vacuoles including mitochondria and dense bodies were observed. These were reduced in size by refeeding for only one day, suggesting that fasting may cause intracellular digestion through lysosomal autophagy.

7. These results lead to the conclusion that long‐term fasting for force moulting is possible, that a high protein and high energy diet can be fed immediately after fasting and that a cell undergoing lysosomal autophagy in normal chickens indicates undernutrition.     

Food intake and abdominal adipose tissue in White Leghorn hens fed diets of different protein and energy concentrations

1. Single Comb White Leghorn hens of 2 ages (44 and 80 weeks) were fed diets of different energy (10.88, 12.13 or 13.39 MJ ME and 140 g protein/kg) or protein (120, 140, 160 or 180 g and 12.13 MJ ME/kg) concentration over an 8-week period. 2. Food intake did not change with increasing concentrations of dietary protein. Protein intake was directly correlated with dietary protein concentration. 3. Energy intake increased with dietary energy concentration but, generally, failed to match the increases in dietary energy concentration. Energy, rather than protein, concentration was the major determinant of food intake. 4. Efficiency of energy utilisation decreased and mean adipocyte size increased with higher energy intake. 5. A bimodal adipocyte size distribution, consisting of a primary large size and a secondary small size population, was present in the abdominal fat pad of birds of both ages. There was no significant difference in the numbers of large adipocytes between the hens of the two ages. 6. The greater mean fat pad weight in the older hens was associated with increased mean cell volume in the population of large adipocytes.     

The absorption and excretion of minerals by laying hens in relation to egg shell formation

The absorption and urinary and faecal excretion of calcium, phosphorus, magnesium, sodium, potassium and chloride were studied in four colostomised laying hens during 24 hr periods. The urinary excretion of ammonia was also determined. Data for 10 laying and 5 non‐laying days were obtained. On laying days (a) net absorption of all minerals, expressed either as actual weights or as a percentage of intake was greater, (b) urinary excretion of phosphorus, potassium and ammonia was greater and of calcium, magnesium and chloride less and (c) retention of all minerals was greater, than on non‐laying days.

The urinary findings can be largely explained in terms of the requirements of the shell gland for calcium and bicarbonate ions and the need to excrete the phosphate liberated from the skeleton during egg shell formation.     

Effect on shell strength of feeding supplemental sources of calcium to adult laying hens given insoluble grit during the rearing period

1. An experiment was conducted to determine the separate and combined effects of giving insoluble grit during the rearing period and small or large particle size (0.3 mm and 3 to 8 mm in diameter) limestone or oyster shell, as extra sources of calcium, during the laying period. 2. For the entire laying period the extra sources of calcium resulted in improved shell strength but, overall, grit-supplements during the rearing period did not affect either egg shell strength or other performance traits. 3. An analysis for interactions however revealed that limestone of larger particle size coupled with rearing period-grit resulted in improved egg-shell strength during the last quarter of the laying period.     

Changes in feather condition in relation to feather pecking and aggressive behaviour in laying hens

The aim of this experiment was to describe and examine the relationship between pecks received by individual birds and the feather and skin damage of those birds at different ages. The effect of group size was also studied. Laying hens were raised in floor pens in group sizes of 15, 30, 60 and 120 birds, each with 4 replicates. Behavioural observations were performed at the ages of 22, 27, 32 and 37 weeks. Detailed feather scoring was carried out at the ages of 18, 23, 28 and 33 weeks. Behavioural observations focused on the number of feather pecks (gentle and severe) and aggressive pecks received, and on the part of the body that was pecked. Scoring of feather and skin damage focused on the same 11 parts of the body. Increasing numbers of aggressive pecks received were associated with decreased body weight and increased feather damage at the ages of 27 and 32 weeks. The number of severe feather pecks received was significantly related with feather damage at all ages; however, no relation with gentle feather pecks received was found. Group size had a significant effect on feather condition, with large group sizes having most feather damage.     

Influence of quantity of utter on nest box selection and nesting behaviour of domestic hens

1. Twenty two hens (Gallus gallus domesticus) were given a free choice, for egg laying, between 4 nest boxes containing different quantities of wood shavings (litter): 3180 cm³ (large), 1060 cm³ (medium), 350 cm³ (small) and none (zero).

2. There was considerable individual variation in the quantity of litter selected for egg laying, but 17 hens laid 50% or more of their eggs in a single litter quantity. Hens selected the large quantity in preference to the small and zero. More searching, nest selection and nesting behaviours tended to be directed to the boxes with the largest quantities and also to the quantities that the hens finally selected for egg laying.

3. In a second experiment, the hens from experiment 1 which showed a preference for litter, and a further 22 naïve hens were given a choice of three nest boxes containing no litter and one containing one of 6 quantities. Over 30 trials there were 5 replicates using each of the three quantities used in experiment 1 plus 115 cm³, 40 cm³ and 10 cm³.

4. There was a wide range in the proportion of trials in which hens selected litter; for experienced hens the range was 0.43 to 0.97, but only two naïve hens were within this range, all others being between 0 and 0.43.

5. The pattern of choosing litter quantities was comparable but at different levels of preference in experienced and naive hens and a contour map was derived enabling predictions to be made of the probability of a particular quantity being chosen.

6. The variability of individual responses suggest that no single type of nest box system can cater for the requirements of all hens.     

Genetic resistance to Leukosis virus infection: effects on mortality and egg production in Leghorn hens

The influence of genotypic differences in resistance to infection from Lymphoid Leukosis (LL) on mortality and egg production was studied in three pairs of sublines. One subline of each pair had been selected for resistance and the other for susceptibility to infection. At 10 months of age, almost no hens with neutralising antibodies against LL were found in the resistant sublines, while in each susceptible subline more than 40% of the hens had LL antibodies. At 21 months of age, very few hens of the resistant sublines had group-specific (gs) antigen in their eggs. Susceptible sublines differed considerably in this respect, from 81% gs antigen-positive hens in one subline to 9% or no positive hens in the others. On the whole, the susceptible sublines had 6% higher mortality during the laying period (8 months) but the size of the difference was influenced by vaccination against Marek's disease (MD) and varied considerably between pairs of sublines. Significant interactions between strain and genotype of resistance to LL infection were observed for mortality from "other causes" in hens vaccinated against MD, as well as for mortality from "Leukosis" and from "MD" in non-vaccinated hens. The average rate of lay from 1 to 8 months was 8% lower in susceptible hens. In the subline with the highest frequency of eggs containing LL group-specific antigen in the albumen, the reduction of laying rate was twice as large as in the other susceptible sublines.     

Carbonic anhydrase and its isozymes in heat stressed white Leghorn hens

Experiments were conducted to study the effect of heat stress on uterine tissue carbonic anhydrase levels and their isozyme patterns in relation to production of no- and thin-shelled eggs. Birds exposed to naturally occurring heat stress had lower enzyme levels in their uteri than birds kept in an air-conditioned pen. 4 isozyme bands of carbonic anhydrase were visible in uterine tissue homogenate from both groups of birds. Isozymes were suppressed in heat-stressed birds, as was evident from staining intensities of the bands. This provided evidence to the effect that heat stress not only decreased the total quantity of carbonic anhydrase in the uteri of the hens but also suppressed its isozyme fractions, leading to greater production of no-shell and thin-shelled eggs.     

Effect of husbandry system on broken bones and bone strength in hens

The effects of rearing system, forced moulting and three different layer housing systems on broken bones and bone strength, were examined in hens at the end of lay. Weak bones and broken bones were more common in battery hens which had been reared to point of lay on deep litter rather than in cages. The incidence of old breaks was greater in perchery birds (14 per cent) than in tiered terrace birds (5 per cent), and there was also a difference between their incidence in two types of perchery design (17 per cent and 11 per cent). Moulting was associated with a transient decline in bone strength, followed by an increase in strength during the second lay.     

Limb bone strength and movement in laying hens from different housing systems

Walking and bouts of wing movement performed by 61-week-old ISA brown laying hens which had been taken from one batch of eggs and then kept in three different housing systems which allowed a gradation in spatial freedom, were recorded. After slaughter the breaking strengths of the humerus and tibia of birds from each system were measured. Birds from battery cages exhibited the fewest limb movements and had the weakest bones, their humeri having only 54 per cent of the strength of those of birds from a perchery. Birds from the Elson terrace system were heavier and had a stronger tibia than cage birds. Compared with perchery birds, terrace birds had weaker humeri and also performed fewer wing movements. The results indicate that the amount of movement possible for laying hens in battery cages was insufficient to avoid levels of osteopenia and consequent bone fragility much greater than in birds kept in the perchery and Elson terrace systems.     

大豆黄酮对产蛋鸡蛋壳品质和骨骼代谢的影响

大豆黄酮(Daidzein)属于异黄酮类植物雌激素(Isoflavonic phytoestrogen)，主要存在于豆科的蝶形花亚科植物中。20世纪90年代以来，国外流行病因学研究证明，膳食中的异黄酮具有防癌和抗癌的作用，使人类乳腺癌、结肠癌发病率降低，近年来动物营养研究表明大豆黄酮具有促进动物生长，增加产     

Relationship of plasma calcium and phosphorus to the shell quality of laying hens receiving saline drinking water

1. From 36 to 43 weeks of age 210 White Leghorn laying hens were used to study the relationship of plasma calcium and phosphorus concentrations to egg‐shell quality when saline drinking water was given.

2. Seven experimental treatments in which different amounts of sodium chloride were supplied by the food and/or the drinking water were compared.

3. Increasing salt intake through the drinking water or the food reduced shell thickness and shell calcium, and increased the numbers of damaged eggs. Sodium chloride given in the drinking water was more effective in reducing shell quality and increasing plasma calcium and phosphorus than sodium chloride given in the food.     

Influence of housing system and design on bone strength and keel bone fractures in laying hens

The main objectives of the study were to provide an accurate assessment of current levels of old breaks in end-of-lay hens housed in a variety of system designs and identify the important risk factors. Sixty-seven flocks housed in eight broad subcategories were assessed at the end of the production period. Within each flock, the presence of keel fractures was determined and the tibia, humerus and keel bones dissected for measurement of breaking strength. For each house, variations in internal design and perching provision were categorised and the effective heights of the differing structures recorded. All systems were associated with alarmingly high levels of keel damage although variation in mean prevalence between systems was evident with flocks housed in furnished cages having the lowest prevalence (36 per cent) despite also having significantly weaker bones and flocks housed in all systems equipped with multilevel perches showing the highest levels of damage (over 80 per cent) and the highest severity scores.     

Response of White Leghorn and Nigerian cockerels to experimental salmonella infection

Summary Twenty-two Nigerian cockerels and 19 White Leghorn cockerels were each injected intramuscularly with 1·5×10⁹ viable organisms of a relatively avirulent strain ofSalmonella gallinarum (NCTC 10532). The Nigerian cockerels were more resistant to infection as judged by the values of the haemoglobin, haematocrit, red cell count, leucocyte count and antibody titre during the course of infection. The authors suggest that the higher resistance may be due to the earlier growth and higher organ weight of the bursa of Fabricius of the Nigerian breed than of the White Leghorn (Aire,1973).

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Sumario Ventidos pollos Nigerianos y diecinueve White Leghorn fueron inoculados individualmente vía intramuscular, con 1·5 × 10⁹ de una suspensión relativamente avirulenta de una cepa deSalmonella gallinarum (NCTC 10532). Los pollos Nigerianos fueron más resistentes a la infección, teniendo en cuenta los valores de hemaglobina, hematocrito, número de globulos rojos, leucocitos y título de anticuerpos durante el curso de la infección. Los autores sugieren, que la mayor resistencia de la raza Nigeriana, podría estar relacionada con el peso y desarrollo mástemprano de la bolsa de Fabricius.

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Résumé Trente deux coquelets Nigériens et dix neuf coquelets Leghorn blancs ont été infectés, chacun par une injection intramusculaire de 1·5 × 10⁹ germes vivants d'une souche relativement avirulente deSalmonella gallinarum (NCTC 10532). L'examen, tout au long de l'expérience, de l'hémoglobine, des hématocrites, la numération des hématies et des leucocytes et le titrage des anticorps ont montré que les coquelets Nigériens étaient plus résistants. Les auteurs suggèrent que cette résistance supérieure peut être due au développement plus précoce et au poids supérieur de la bourse Fabricius chez le coquelet Nigérien par rapport au coquelet Leghorn blanc (Aire, 1973).