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.     

Genetic study of embryonic mortality in White Leghorn lines selected for egg production traits

The present study compares embryonic mortality between lines selected for different production traits, assesses the effects of inbreeding of the hen and embryo on embryonic mortality, and estimates genetic parameters of embryonic mortality. The experiment covered 10 generations of selection for increased egg number (EN), egg weight (EW), egg mass (EM) and a control line (C). The data included age at 1st egg, egg number and egg weight. Percent fertile eggs (PF), percent hatched of fertile eggs (PHF) and percent dead chick at hatch (PDH) were also recorded for the selected parents. PDH was higher in the selected lines than in the control line. Among the selected lines, the EW line had the highest embryonic mortality. Inbreeding of the hen and embryo had no significant effect on PDH in any of the lines. Estimates of heritability for PDH were 0.10+/-0.05, 0.02+/-0.02, 0.03+/-0.02 and 0.02+/-0.02 for lines EN, EW, EM and C, respectively. There was a positive genetic correlation between egg weight and PDH in line EW indicating that selection for increased egg weight was associated with high embryonic mortality. A negative genetic correlation between PDH and reproductive traits in line EN was observed, which is favourable.     

Effects of Eimeria mitis on egg production of single-comb White Leghorn hens.

Single-comb white leghorn hens infected with either B4 or C2 strain of Eimeria mitis produced watery droppings as early as day 5 PI. E. mitis infection did not affect egg weight. However, specific gravities of the eggs produced by the hens infected with E. mitis were lower than those produced by the controls. Egg production was significantly reduced temporarily, but most birds returned to production within 14 days. Many of the birds that ceased to lay went through a complete-body molt (56% of the C2-infected hens and 20% of the B4-infected hens). Hens that ceased to lay regained considerable amounts of pigment in their skin, beaks, and shanks.     

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.     

合生素对蛋鸡生产性能及蛋品质的影响

在我国传统养殖生产中,抗生素一直被用作饲料添加剂来控制畜禽疾病和提高生产性能。但随着抗生素的大量使用,其带来的负面影响日趋严重。药物残留和耐药菌株的产生及畜禽产品质量的下降,已对畜牧业可持续发展和人类健康带来严重的影响。研制开发无公害和无残留的饲料添加剂替代     

Mycoplasma gallisepticum vaccination: effects on egg transmission and egg production

The effects of Mycoplasma gallisepticum (MG) vaccination on egg transmission of MG and egg production were evaluated. Leghorn hens vaccinated with live MG (strain F), with strain F plus MG bacterin, with one dose of MG bacterin, or with two doses of MG bacterin all transmitted MG through the egg at a significantly lower level than unvaccinated controls. Hens vaccinated with two doses of MG bacterin had the longest lag before detectable transmission of MG through the egg. All vaccinated groups were protected against the egg-production drop seen in unvaccinated hens challenged with virulent MG.     

Genetic differences of Ascaridia galli egg output in laying hens following a single dose infection.

Groups of 20-week-old white (Lohmann LSL) and brown (Lohmann Brown) hens were reared under helminth-free conditions and both divided into two subgroups. One subgroup was artificially infected with 250 embryonated Ascaridia galli eggs, the other subgroup were kept as uninfected controls. During the following 12-month laying period individual faecal Ascaridia egg counts (FEC) were performed and bodyweight measured at monthly intervals. Laying performance and egg weights were determined daily. The mean FEC were significantly (P < 0.01) higher in infected white hens than in infected brown hens. The growth rate of the white hens was significantly (P < 0.05) higher in the control group, whereas in brown hens no significant group difference was observed. The laying performances and egg weights did not differ significantly (P > 0.05) between control and infected animals for either line. The estimated repeatabilities for mean log(10) FEC of different samples were reasonably high (0.16-0.54). Heritabilities for mean log(10) FEC were between 0.13 and 0.19 for white hens and between 0.0 and 0.10 for brown hens. Thus, it should be possible to select for A. galli resistance in chickens, which will be of importance for birds kept in alternative and organic farming systems.     

Histamine in egg yolk: heat resistance and relation to production status

1. The presence of histamine in egg yolk, its losses during storage, incubation and heating, and its relationship to cage density stress and the egg production status of hens are described. 2. A significant (P less than 0.05) reduction in the histamine concentration of egg yolk was noted after incubating or heating egg yolks or on storage eggs. 3. Histamine concentration was greater in the yolks of high egg producing hens. 4. The concentrations of histamine in egg yolks did not change significantly (P less than 0.05) on keeping the hens individually in a cage, pairing them in the same size cage or after separating them again to individual cages.     

Effects of dietary copper on production and egg cholesterol content in laying hens

1. This experiment was carried out to determine the effects of diets supplemented with different amounts of copper on egg production, food intake, food conversion ratio, egg weight, damaged egg ratio, specific gravity, mortality and cholesterol concentration in yolk. The experiment lasted 90 d and 400 Hisex-Brown hens, aged 27 weeks at the start of the study, were used. 2. There were no statistically significant effects of supplementary copper on egg production, food intake or food conversion efficiency. 3. There were no statistically significant differences between the groups in terms of damaged eggs, egg weight, specific gravity and live weight. 4. At the end of the experiment, the lowest yolk cholesterol concentrations were obtained in the 150 kg/kg copper group and the greatest concentrations were in the control group. 5. Consequently, the use of supplementary copper to provide 150 kg/kg in poultry diets was concluded to decrease yolk cholesterol concentrations without any effect on production performance.     

Sand intake by laying hens and its effect on egg production parameters

Soil intake may be the most prominent source of environmental contaminants for free range and organic hens, but there are no quantitative data concerning soil intake by domestic hens. Consumption of soil of 14–32 g a day can be estimated from literature, but such a dilution of nutrient intake seems incompatible with high productivity. In this study laying hens were fed pelleted diets with 0%, 10%, 20%, 25% and 30% of sand addition to determine its effect on productivity. Feed intake, feed and nutrient (feed minus sand) conversion ratio, egg production, egg weight and body weight gain were measured over a 4-week period. Acid insoluble ash concentration in the faeces was measured to determine the accuracy of estimating the soil ingestion by the soil-ingestion equation for wildlife as a way to determine soil ingestion of free range and organic hens under practical circumstances. The hens were able to compensate the dilution of the diet with 20%, 25% and 30% of sand by increasing their feed intake. Feed intake increased significantly and feed to egg conversion ratio decreased significantly with increasing sand levels in the diet. The nutrient to egg conversion ratio of the diet without sand tended to be worse than for the diets with sand, presumably due to the total absence of coarse material in the diet. There were no differences in egg production and egg weight between hens fed the different diets but body weight gain was significantly lower for the hens fed the diets with 20%, 25% and 30% of sand. Estimation of sand ingestion was done by the soil-ingestion equation for wildlife. Provided that the actual dry matter digestibility coefficient of the nutrient part of the diet is taken into account, estimating the soil ingestion according to the soil-ingestion equation for wildlife seems an appropriate way to determine soil ingestion for free range and organic hens under practical circumstances.     

The influence of handling on egg production,egg shell quality and avoidance behaviour of hens

1. Egg production was similar in non‐handled and in regularly handled hens, but was reduced by handling hens unaccustomed to the procedure.

2. Handling reduced avoidance behaviour (”flightiness“) in growers and pullets but its effect declined with age and it had no influence in these hens when mature.

3. Handling affected egg shell quality; it resulted in an increased incidence of cracks and of equatorial bulges. Previous work has suggested that this defect is an indication of stressors applied at a critical period during egg formation. Therefore, handling may be a stressor.     

抑制素基因免疫对京白鸡产蛋性能的影响

120只380 d京白鸡随机分为4组,分别腿部肌肉注射0、50、100、150 μg抑制素真核表达质粒pcISI,20 d后加强免疫1次.ELISA检测抗抑制素抗体水平,观察产蛋量,并进行鸡蛋品质测定.免疫4个月后全部捕杀,统计各级卵泡数.结果表明,抑制素基因加强免疫后抗体水平显著升高(P<0.05),3个剂量组间差异不显著(P>0.05).试验组全期产蛋量极显著高于对照组(P<0.01),大白泡和小白泡比对照组显著增多(P<0.05),优势卵泡、小黄泡和鸡蛋品质与对照组差异不显著(P>0.05).表明抑制素基因免疫京白鸡可产生抗抑制素抗体,并能提高京白鸡的产蛋性能.     

酶解羽毛粉对蛋鸡生产性能的影响

选用192只23周龄产蛋良好的海兰褐商品蛋鸡,探讨日粮中添加不同比例的酶解羽毛粉对蛋鸡生产性能的影响,设3个处理,每个处理4个重复,每个重复16只鸡,三层阶梯式笼养,自由采食和饮水,进行饲养试验。试验期为30d。对各处理组的蛋鸡日只耗料量、产蛋率、日只产蛋量、平均蛋重、料蛋比的记录数据进行统计分析,研究用羽毛粉代替部分植物蛋白饲料（豆粕）的可行性。结果表明,日粮中添加2．5％和5％酶解羽毛粉对蛋鸡日只耗料量、产蛋率、日只产蛋量、平均蛋重、料蛋比5项指标均无显著影响（P〉0．05）。因此,在蛋鸡日粮中用羽毛粉代替部分植物蛋白饲料原料是经济可行的。大力开发利用羽毛粉,对解决我国目前蛋白资源紧缺的状况具有重要的理论和现实意义。     

Prevalence of nematode infection and faecal egg counts in free-range laying hens: relations to housing and husbandry

1. Faecal samples from 19 commercial, 65 week old free-range egg laying flocks were examined to assess the prevalence and number of parasitic nematode eggs. Data were collected to characterise the housing, husbandry, behaviour and welfare of the flocks to examine possible relationships with the egg counts.

2. Eggs of at least one genus of nematode were present in the faeces of all 19 flocks. Heterakis eggs were detected in 17 (89%) flocks, Ascaridia in 16 (84%), Trichostrongylus in 9 (47%), and Syngamus in 6 (32%). Faecal egg counts (FEC) were greatest for Ascaridia and Heterakis.

3. For each nematode genus, there was no significant difference in FEC between organic (N?=?9) and non-organic (N?=?10) flocks, or between static (N?=?8) and mobile (N?=?11) flocks.

4. FEC were correlated with a range of housing, husbandry and management practices which varied between the nematode genus and included depth of the litter, percentage of hens using the range, and number of dead hens. Statistical analysis indicated relationships with FEC that included light intensity above the feeder, indoor and outdoor stocking density, fearfulness in the shed and on the range, distance to the nearest shelter, and swollen toes.

5. None of the FEC for any of the genera was correlated with weekly egg production or cumulative mortality.

6. Although nematode FEC were highly prevalent among the flocks, the overall lack of relation to other welfare and production measures suggests that these infections were not severe.     

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.     

Prevalence of antibodies to Mycoplasma synoviae in laying hens and possible effects on egg shell quality

Mycoplasma synoviae (M. synoviae) can cause respiratory disease, synovitis, or result in a silent infection in chickens and turkeys. The importance of M. synoviae is well established in broilers but only a few studies have been conducted in layers. In the present study, the prevalence of M. synoviae in commercial layer flocks was estimated using ELISA. For this study, 19 commercial layer flocks were selected randomly from New South Wales and Queensland region of Australia from producers who were willing to participate in the survey. Sixty eggs per flocks were randomly collected, out of these 30 eggs were used for ELISA and remaining 30 eggs were used to estimate various egg shell quality parameters. Subsequently, association between the serological status of eggs for M. synoviae and egg shell quality was studied. In the flocks under study, seroprevalence of M. synoviae was found to be high at 69% (95% confidence interval (CI)=41.3-89.0). Statistical analysis showed an association between serological status for M. synoviae and egg quality parameters such as translucency, shell breaking strength, % shell reflectivity and shell deformation. On the other hand, there was no significant association between serological status for M. synoviae and other egg quality parameters such egg weight, egg shell weight, % egg shell or shell thickness.     

Isolation of infectious bronchitis virus from intestine and reproductive organs of laying hens with dropped egg production

A total of 52 samples (22 cloacal swabs and 30 pooled ovaries and oviducts) from hens with a history of a 25 to 40% drop in egg production from 30 flocks were examined for the isolation of infectious bronchitis virus in embryonated chicken eggs. Five isolates were obtained: three from cloacal swabs and two from reproductive organs. These isolates were identified and characterized on the basis of agar-gel-precipitation, hemagglutination, and neutralization tests and other physicochemical characteristics.