Avian leukosis virus (ALV) infection, shedding, and tumors in maternal ALV antibody-positive and -negative chickens exposed to virus at hatching

Chickens highly susceptible to avian leukosis virus (ALV) infection and tumors, with and without ALV subgroup A maternal antibody (MAB), were infected with a field strain of ALV subgroup A at hatching. Viremia, antibody development, cloacal and albumen shedding, and tumors in chickens with MAB (MAB+) were compared with those in chickens lacking MAB (MAB-). At 18 weeks of age, the incidence of viremia was significantly lower in MAB+ chickens than in MAB- chickens; further, MAB significantly reduced the proportion of tolerantly infected (viremic antibody-negative) chickens. Cloacal shedding of ALV at 22 weeks of age and shedding of ALV group-specific (gs) antigen in albumen of eggs from all laying hens at 30-32 weeks of age were significantly lower in MAB+ hens than in MAB- hens. The incidence of ALV-induced tumors was lower in MAB+ chickens than in MAB- chickens, significantly so in one of three trials conducted. These results suggest that MAB may influence the development of viremia, antibody, and shedding of ALV following massive exposure to virus at hatching.     

On epizootiology and control of lymphoid leukosis in chickens

Sera and organ extracts from ten different commercial stocks of layer chickens were examined for the presence of lymphoid leukosis (LL) viruses. Virus was recovered from 40.8% of the cockerels between three and six weeks of age. Their female hatch mates were examined at the age of 20 months. A mean of 11.3% of these laying hens was positive in the NP activation test. Lymphoid leukosis was successfully controlled in three inbred strains of White Leghorn chickens and in a commercial White Plymouth Rock line. All flocks were kept in a filtered air positive pressure (FAPP) house during the first two months of life and thereafter transferred to a conventional environment. The control method is based on three elements:

• —from an infected flock, hens are selected in whose eggs no avian lymphoid leukosis viruses can be detected by examination of pooled extracts of groups of embryos;

• —only eggs from hens that are shown not to shed congenitally virus in their eggs are used for the production of progeny. The offspring are reared in isolation until two months of age at which time the age-related resistance against tumour formation appears to be sufficiently developed;

• —the chickens are subsequently intramuscularly inoculated with lymphoid leukosis viruses of subgroups A and B and transferred to a conventional chicken house. The inoculated birds become persistently viremic and resist horizontal virus exposure and intramuscular challenge infections.

Horizontal virus transmission was observed to take place when virus-free non-vaccinated chickens were reared in isolation for two months and then exposed under field conditions.Efficiency of virus recovery was considerably improved when washed buffy coat cells were cocultivated with chick embryo fibroblasts or explant cultures were prepared from various tissues before testing with the NP activation test.     

Review of induced molting by feed removal and contamination of eggs with Salmonella enterica serovar Enteritidis

As laying hens age, egg production and quality decreases. Egg producers can impose an induced molt on older hens that results in increased egg productivity and decreased hen mortality compared with non-molted hens of the same age. This review discusses the effect of induced molting by feed removal on immune parameters, Salmonella enterica serovar Enteritidis (SE) invasion and subsequent production of SE-contaminated eggs. Experimental oral infections with SE show molted hens are more susceptible to SE infection and produce more SE-contaminated eggs in the first few weeks post-molt compared with pre-molt egg production. In addition, it appears that molted hens are more likely to disseminate SE into their environment. Molted hens are more susceptible to SE infection by contact exposure to experimentally infected hens; thus, transmission of SE among molted hens could be more rapid than non-molted birds. Histological examination of the gastrointestinal tracts of molted SE-infected hens revealed more frequent and severe intestinal mucosal lesions compared with non-molted SE-infected hens. These data suggest that induced molting by feed deprivation alters the normal asymptomatic host-pathogen relationship. Published data suggest the highest proportion of SE-positive eggs is produced within 1-5 weeks post-molt and decreases sharply by 6-10 weeks and dissipates to the background level for non-molted hens by 11-20 weeks. Appropriate treatment measures of eggs produced in the fist 5 weeks post-molting may decrease the risk of foodborne infections to humans.     

Observations on the patterns of embryonic mortality over the laying season of pheasants.

1. Embryonic mortality of domestic pheasant (Phasianus colchinus) eggs was recorded for a 10-week laying season for two groups of laying hens maintained under mating ratios of 8:1 and 12:1 (females:males). 2. Mating ratio had no significant effect on embryonic mortality between 1 and 4 or 5 and 20 d but values for these categories doubled as the laying season progressed, both rising to 8% to 9% of fertile eggs. 3. Higher embryonic mortality was observed between 21 and 25 d for the eggs from the 8:1 mating ratio (14.5% of fertile eggs compared with 12.1%) but this was unaffected by week of setting. 4. Reasons for these patterns of embryonic mortality were not clear and further research is needed to determine the factors affecting embryonic mortality in pheasants.     

洪江雪峰乌骨鸡和罗曼粉蛋鸡鸡蛋营养成分和蛋品质比较

试验旨在比较洪江雪峰乌骨鸡和罗曼粉蛋鸡的鸡蛋营养成分和蛋品质,为洪江雪峰乌骨鸡蛋用新品系选育提供依据。随机选取40周龄的洪江雪峰乌骨鸡(绿壳)、洪江雪峰乌骨鸡(粉壳)和罗曼粉壳蛋鸡各100只,每品种鸡随机分为5个重复,每个重复20只,在相同饲粮和饲养管理方式下进行饲养,45周龄收集鸡蛋检测营养成分和蛋品质指标。结果表明:洪江雪峰乌骨鸡绿壳蛋的蛋黄比例极显著高于罗曼粉壳蛋(P<0.01),蛋重、蛋壳厚度、哈氏单位极显著低于罗曼粉壳蛋(P<0.01),洪江雪峰乌骨鸡粉壳蛋的蛋重和蛋壳厚度极显著低于罗曼粉壳蛋(P<0.01);洪江雪峰乌骨鸡蛋中的多不饱和脂肪酸和硒元素含量均极显著高于罗曼粉壳蛋(P<0.01),洪江雪峰乌骨鸡绿壳蛋胶原蛋白含量极显著高于罗曼粉壳蛋(P<0.01)。综上所述,洪江雪峰乌骨鸡鸡蛋蛋黄比例高,蛋黄多不饱和脂肪酸、胶原蛋白、硒和锰含量高,适合作为优质禽蛋开发。     

鸡白血病的流行现状和防制对策

鸡白血病普遍存在于商品鸡群中,呈渐进性发生和持续的低死亡率,白血病毒感染鸡群,导致鸡群生产性能下降,尤其是产蛋率和蛋的品质下降。介绍了鸡白血病病毒和该病在鸡群中的流行现状,分析了病毒间的谱系关系和发病原因,指出鸡白血病与禽网状内皮组织增生症的鉴别诊断方法,科学地提出对鸡白血病的预防和控制措施。     

Vaccination of turkey breeder hens and toms for fowl cholera with CU strain

Unvaccinated laying breeder hens and semen-producing toms were susceptible to the CU strain of Pasteurella multocida and highly susceptible to a virulent strain of P. multocida. Laying breeders vaccinated with CU strain when environmental temperatures were low ceased egg production during the first week after vaccination and had 29% mortality, whereas those vaccinated when temperatures were moderate had only a 25% decrease in egg production and 17% mortality. Comparable nonlaying breeders vaccinated during moderate temperatures did not die. Although few semen-producing toms died postvaccination and the quantity and quality of semen was not affected, 21.7% developed torticollis. Laying breeders were protected against CU vaccine and challenge with virulent P. multocida if vaccinated every 4 weeks beginning when 7 weeks old. Potential breeders vaccinated before laying with combinations of 3 vaccinations via drinking water, wing-web puncture, or inoculation into the air spaces of the head through the auditory tube were protected against challenge after the onset of laying. However, vaccination via wing-web puncture at 25 weeks of age resulted in abscesses that failed to resolve. The combination of vaccinations most effective in protecting laying breeders was vaccination in the drinking water at 7 and 11 weeks and inoculation into the air spaces of the head at 15 weeks.     

Egg shell colour is affected by laying cage design

1. When laying hens are stressed some retain their eggs in the shell gland beyond the normal time of laying and this can result in the deposition of extra-cuticular calcium which makes brown eggs appear paler. 2. Three different types of enriched modified cage were compared: the location where eggs were laid was recorded and shell colour was measured using a reflectometer. 3. In 2 types of cage with enclosed nest boxes more eggs (80%) were laid in the nests than in a design with nest hollows in the open part of the cage (41%). 4. The eggs from the cages with enclosed nests were darker (had less extraneous calcium) than those with open nest hollows. This implies that in the designs with nest boxes fewer eggs had been retained and the hens may have been less stressed. 5. The results support previous evidence that to reduce stress and improve welfare it is desirable to provide enclosed nest sites for caged laying hens.     

Performance of commercial laying hen genotypes on free range and organic farms in Switzerland,France and The Netherlands

1. A total of 257 farmers with free ranging laying hens (organic and conventional) in Switzerland, France and The Netherlands with 273 flocks were interviewed to determine the relationships between the genotype of the hens, management conditions and performance.

2. Almost 20 different genotypes (brands) were present on the farms. In France, all birds were brown feathered hens laying brown eggs. In Switzerland and The Netherlands, there were brown, white (white feathered hens laying white eggs) and silver (white feathered hens laying brown eggs) hens. In Switzerland, mixed flocks were also present.

3. The overall effect of system (organic vs. conventional free range) on egg production and mortality was significant, with higher mortality and lower egg production among organic hens. In pair wise comparisons within country, the difference was highly significant in The Netherlands, and showed a non-significant tendency in the same direction in Switzerland and France.

4. White hens tended to perform better than brown hens. Silver hens appeared to have a higher mortality and lower production per hen housed at 60 weeks of age.

5. There were no significant relationships between production, mortality, feather condition and use of outside run or with flock size.

6. There was more variation in mortality and egg production among farms with a small flock size than among farms with a large flock size.     

Studies on reducing the crude protein content of feeds fed to chicks and young hens (laying stock)]

2 rearing trials were carried out on a total of 8550 hybrid chicks (White Leghorn) to investigate in which way food mixtures containing reduced levels of crude protein (supplemented or unsupplemented with amino acids) might influence the growth of chicks and young hens. Decreases from 21.5% to 16.5% in the crude protein content of chicken feed and from 15% to 13% in feeds feed to young hens (greater than 8 weeks of life) did not reduce the live weight of birds at the end of the rearing period to any appreciable extent. No clearly defined differences were found to exist between the different types of feed tested concerning the amount of food and energy consumed per unit of weight gain and the mortality rate among the birds; it was shown, however, that the demand for crude protein per unit of weight gain was clearly reduced in birds reared at the lower crude protein level. For young hens receiving the diet poorer in protein the date when the birds began laying was slightly delayed. Otherwise, no statistically significant differences were found to exist between the young birds fed varying levels of crude protein, concerning the age at 50% laying performance and other parameters that are characteristic of the entire laying period (laying performance, weight of individual eggs, food consumption, mortality, fertilization of hatching eggs, hatchability of eggs). It appears that the feeding of a reduced protein diet to chicks and young hens (laying stock) did not have any detrimental effect on the growth and later laying performance of the birds. Apart from the fact that the demand for protein feeds is considerably reduced during the rearing period the costs of feeding per bird can also be cut down.     

鸡黄病毒灭活疫苗的研制及免疫效果研究

鸡黄病毒FQ—C1株经SPF鸡胚连续传40代后,检测其尿囊液毒的ELD50达到1×10^-4.33／0．1mL。将该病毒第40代SPF鸡胚液毒灭活后制备成油乳剂灭活疫苗。SPF雏鸡和蛋鸡安全性试验表明,该疫苗的安全性好,无不良影响。以该疫苗一次单剂量（1mI／只）免疫开产蛋鸡,28d后攻以鸡黄病毒强毒测定疫苗的保护效果,结果显示疫苗免疫组较未免疫组蛋鸡的产蛋率高出75．8％,产蛋保护率达93．2％以上。试验表明,本研究制备的鸡黄病毒灭活疫苗安全性好,且具有良好的免疫原性,免疫后可有效抵抗鸡黄病毒所致的产蛋骤降。     

Battery gage shape: The laying performance of medium‐ and light‐body weight strains of hens

1. One thousand two hundred and ninety‐six medium‐ and 1296 lightweight hens were housed, four to a cage, in deep (conventional) cages, 405 mm wide by 460 mm deep, or shallow cages, 610 mm wide by 305 mm deep, between 18 and 70 weeks of age. The performance of the hens during different periods of the laying stage and over the full laying year was measured.

2. Egg number per medium‐weight hen housed in shallow cages was significantly higher than of hens housed in deep cages between 18 and 30 weeks and 31 and 42 weeks. Thereafter significant differences were not found. With the light‐weight hens the increase was significant only in the 18‐ to 30‐week period. Apart from the 19‐ to 30‐week period hens of both strains housed in shallow cages consumed significantly less food than those in deep cages, the reduction over the full year being about 4%. In all periods the hens housed in the shallow cages converted food more efficiently. Gage shape had no significant effect on mortality.

3. The incidence of hair‐cracked, cracked and broken eggs between 60 and 70 weeks of age from hens housed in shallow cages was lower than that from hens housed in the deep cages but only with the light‐weight hens did this difference reach significance. Shell thickness, shell weight and albumen quality of eggs laid by hens housed in the different shaped cages were not significantly different.     

Investigations on the pathogenicity of Erysipelothrix rhusiopathiae in laying hens

Erysipelas was diagnosed in 1998 from 34-wk-old laying hens in a free range flock in Germany. Erysipelothrix rhusiopathiae of serotype 1 was cultured from internal organs of the affected birds. This article describes the pathogenicity of the field isolate of E. rhusiopathiae in experimentally infected specific pathogen-free (SPF) laying hens. Three experiments were performed with SPF chickens inoculated at 17, 27, and 37 wk of age by either intramuscular (IM) or oral route. Inoculated birds were observed for 14 days. The highest mortality rates occurred in older birds, with 100% mortality observed in the 37-wk-old birds inoculated IM, 60% mortality reported in the younger 27-wk-old birds, and no mortality in the 17-wk-old age group. In the orally infected 27-wk-old birds, 40% mortality was detected, whereas no mortality was observed in the oldest birds by the same route. The results of the experiments support the contention that older birds are more sensitive to infection than younger birds and that mortality in laying hens is age related and dependent on the route of infection.     

Risk factors for Marek's disease and mortality in white Leghorns in Norway

A prospective longitudinal field study was conducted in the period from January 1994 to January 1996 to analyse the relationship between some selected risk factors in the growing and laying periods and (1) the flock-level occurrence of Marek’s disease (MD) during the period from 16 to 32 weeks of age and (2) the cumulative mortality during the same period. A total of 171 layer flocks in 102 egg-production farms were included in the statistical analyses.

A logistic regression (with strain of layer and vaccination program against MD as fixed effects) of flock-level MD-status during the first 16 weeks of the laying period was conducted. Of the risk factors investigated, “multi-age management” and “housing system” were significantly associated at the rearing farm, and “number of hens in each cage” at the egg-production farm. Flocks kept in single-age facilities had a lower risk of MD than flocks housed in farms with multi-age management. The odds of MD were larger for flocks housed on a litter floor in the rearing farms compared to flocks housed in battery cages. At the egg-production stage, flocks kept in battery cages housing more than three hens were at greater risk of MD than those held in cages for three hens or less.

A weighted least-squares regression (with strain of layer and flock-level MD-status as fixed effects) of cumulative mortality during the period from 16 to 32 weeks of age was also run. The same risk factors (with the same directions of effects) and “size of the rearing farm” were included in the final model of mortality. Chicks reared in medium-sized farms were at higher risk of dying than those coming from either small or large rearing farms. Our results confirm the importance of preventing chicks from being exposed to MD-virus during the rearing period, to reduce the risk of MD-outbreaks (and thereby, mortality losses) during the early stage of the egg-laying period.     

The control of lymphoid leukosis in a flock White Plymouth Rock chickens

Summary Lymphoid leukosis (LL) was successfully controlled in a commercial basic breeding line of White Plymouth Rock chickens. The control method has been developed for breeder flocks and consists of three elements: - In the flock under study, homogenates of embryos from all eggs collected during a number of I4-day periods are tested for the presence of LL viruses. - Only eggs from hens that have been shown not to shed virus in their eggs are used for the production of progeny. The offspring are reared in isolation during the first two months of life, at which time the age-related resistance against tumour formation by LL viruses appears to be sufficiently developed. - The chickens are subsequently inoculated intramuscularly with LL viruses of subgroups A and B transferred to a conventional chicken house. The vaccination raises a solid immunity to horizontal LL virus exposure and, due to the age-related resistance, tumour formation does not follow. No excretion of LL viruses could be detected in three generations of White Plymouth Rock chickens to which the three elements of the control procedure were applied. Clinical disease was not observed in any of the chickens under notice.     

Effects of Observed Incubation Behavior on Egg Production in Laying Hens of a Commercial Chicken Breed and Detection of Single-Nucleotide Polymorphisms Associated with the Incubation Behavior

Upon contact with laid eggs, avians initiate incubation behavior and stop laying additional eggs. This phenomenon suggests that the productivity of laying hens in free-range facilities may decrease because of frequent contact with laid eggs. Here, we examined whether hens of a commercial breed exhibit incubation behavior in a free-range facility and whether egg productivity subsequently decreases. One-hour observations were performed twice weekly for 3 weeks, during which 9 of 129 hens (7.0%) exhibited incubation behavior (i.e., sitting on eggs) in the free-range facility and were defined as incubating hens. During 4 d of continuous behavioral observation, incubating and non-incubating hens laid the same number of eggs statistically (4.6 and 3.6, on average, respectively); however, incubating hens spent significantly more time on average incubating the eggs (2071.9 min) than did the non-incubating hens (20.9 min; P<0.05), indicating a clear behavioral difference. Subsequently, the incubation behavior and egg productivity of incubating hens and a Silkie Fowl breed hen, which is known to exhibit typical incubation behavior and cessation of laying, were continuously compared for 27 d. The average minutes spent incubating eggs during the observation period increased in both the incubating hens and Silkie Fowl hen and the total time was almost the same (18,088.5 and 23,092 min, respectively). However, the Silkie Fowl hen stopped laying on day 17 after laying 17 eggs, whereas the incubating hens continued laying throughout the observation period. Incubating hens laid an average of 24.5 eggs, indicating that some hens (at least those of the commercial breed used in our study) can continue laying while exhibiting incubation behavior. A single-nucleotide polymorphism associated with incubation behavior was detected on chromosome 4 through genome-wide association analysis.     

Effects of stocking density and group size on the performance of white and brown Hyline layers in semi-arid conditions

The effect of housing two Hyline strains of commercial laying hens White Hyline (W-98) and Brown Hyline (Hyline Brown) at densities of 2, 3 or 4 per cage (1100, 733 or 550 cm²/hen, respectively) was investigated over 3 months. Hyline Brown layers gained more weight, laid more but lighter eggs, utilized feed more efficiently and had a lower mortality than W-98 layers. Housing birds 2 or 3 per cage resulted in greater body weight gain, higher egg production, heavier eggs, better feed conversion ratio and a lower mortality than housing them 4 per cage. There were significant interactions between strain and stocking density for egg production, egg weight, egg output and mortality. It is suggested that for egg production in semi-arid areas Hyline Brown hens could be used and housed at a density of 733 cm²/hen.     

松针粉对蛋鸡生产性能、蛋品质、血清生化指标和抗氧化指标的影响

试验旨在研究松针粉对蛋鸡生产性能、蛋品质、血清生化指标和抗氧化指标的影响,以期为松针粉在蛋鸡生产中的应用提供参考。选用120羽40周龄健康产蛋期京粉1号蛋鸡作为试验动物,随机分为2组,每组6个重复,每个重复10羽鸡。对照组饲喂基础饲粮,试验组用3%松针粉替代基础饲粮中的小麦麸。预试期7 d,正试期56 d。试验期间,每天按重复记录采食量、产蛋总数、总蛋重等,并以组为单位统计其平均日采食量、平均蛋重、日产蛋量、料蛋比等;在正试期第28和56天,分别从各重复中取2枚鸡蛋测定蛋壳强度、蛋壳厚度、蛋黄颜色、哈夫单位;在试验结束前1 d和结束当天,从各重复中抽取10枚鸡蛋于4℃贮藏,每次从各重复中取2枚鸡蛋,测定其贮藏后第15、20、60、105天的哈夫单位;在正试期第56天从各重复中选取试验蛋鸡1只,空腹12 h后经翅下静脉采血5 mL后分离血清,采用全自动生化仪测定血清中总胆固醇（TC）、甘油三酯（TG）、高密度脂蛋白胆固醇（HDL-C）、低密度脂蛋白胆固醇（LDL-C）、总蛋白（TP）、白蛋白（ALB）、尿酸（UA）、尿素（Urea）、葡萄糖（GLU）含量及丙氨酸氨基转移酶（ALT）、天门冬氨酸氨基转移酶（AST）、碱性磷酸酶（ALP）活性;采用试剂盒法测定血清中丙二醛（MDA）含量、超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-Px）、谷胱甘肽（GSH）、过氧化氢酶（CAT）的活性和总抗氧化能力（T-AOC）。结果显示：①与对照组相比,饲粮中添加松针粉显著提高了蛋鸡产蛋率（P<0.05）,显著降低了平均蛋重和料蛋比（P<0.05）,但平均日采食量、平均日产蛋量和合格蛋率均无显著差异（P>0.05）。②试验第28天,试验组蛋黄颜色值显著高于对照组（P<0.05）,试验第56天,两组间蛋黄颜色值差异不显著（P>0.05）;其余时间点,饲粮中添加松针粉对鸡蛋的哈夫单位、蛋壳厚度和蛋壳强度均无显著影响（P>0.05）。③与对照组相比,饲粮中添加松针粉对蛋鸡血清TC、TG、HDL-C、LDL-C、TP、ALB、球蛋白（GLB）、尿素、UA和GLU含量以及ALT、AST、ALP活性均无显著影响（P>0.05）,显著提高了蛋鸡血清MDA含量和GSH-Px活性（P<0.05）,但对GSH含量和SOD、CAT活性以及T-AOC均无显著影响（P>0.05）。综上所述,饲粮中添加3%松针粉能够显著提高蛋鸡产蛋率,改善料蛋比和蛋黄颜色,显著提高蛋鸡血清MDA含量和GSH-Px活性,但未影响机体T-AOC。因此,蛋鸡饲粮中用3%松针粉替代等比例的小麦麸是可行的。     

Effect of feeding low lysine starters and developers on growth,sexual maturity and subsequent performance of broiler breeder pullets 1

Pullets that were fed diets containing 0.53 per cent and 0.42 per cent lysine grew at a slower rate and matured later than those that were given adequate amount of lysine. The latter pullets converted their food more efficiently than did the restricted pullets with the exception of the group fed the ration containing 0.53 per cent lysine for the first 12 weeks. The restricted pullets consumed less food during the growing period. A smaller bird was produced on less food. The restricted pullets were also lighter than the control pullets at the end of the laying season. A saving in food costs is indicated because the smaller hen would require less food for maintenance.

There was a higher mortality in the pullets fed a ration containing 0.53 per cent lysine during the growing period. The mortality in the group fed the ration containing 0.42 per cent lysine from 7 to 22 weeks of age was the same as that of the control. There were no differences in mortality during the laying season that could be related to methods of rearing the pullets.

During the laying season, the highest rate of lay was obtained from hens which had been fed the ration containing 0.42 per cent lysine from 7 to 22 weeks of age. Hens fed on the ration containing 0.53 per cent lysine from o to 4, 8 or 12 weeks of age showed no improvement in rate of lay as compared with controls.

Hens fed the ration containing 0.42 per cent lysine from 7 to 22 weeks laid fewer small eggs at the beginning of the laying season than did hens receiving adequate amounts of lysine throughout or fed the ration containing 0.53 per cent lysine from o to 4, 8 or 12 weeks. The hens fed the latter ration laid smaller eggs throughout the laying season.

No differences were found between the fertility, hatchability or embryonic mortality of eggs obtained from hens fed on lysine deficient diets during growth and those fed on diets adequate in lysine.     

Rapeseed Meal and egg taint

1. Certain rapeseed meals in the diet of hens laying brown eggs result in the production, from some birds, of eggs which have a “ fishy ” or “ crabby ” odour because of the presence of trimethylamine.

2. Such susceptible birds have been used to demonstrate that the activity can be extracted from rapeseed meal with appropriate solvents.