One-generation divergent selection on large and small yolk proportions in a White Leghorn line

1. A striking change in egg consumption from shell eggs toward egg products is taking place. Consequently, internal egg quality traits must be seen in a different light, as they may affect the profitability of the egg processing industry. In order to study the possibility of using breeding as a means to alter yolk production, a one-generation divergent selection experiment was set up. The trait was yolk proportion. The effect of hen's age on egg composition was also studied. Genetic parameters for yolk proportion, yolk weight, egg weight and albumen weight were estimated, using a multiple trait animal model, and restricted maximum likelihood. 2. Selection response was obtained for yolk proportion and correlated selection responses for yolk weight and albumen weight. In the 'high line' a decrease in egg weight and an increase in yolk weight was established, whereas in the 'low line', egg weight remained more or less the same and yolk weight decreased slightly 3. Yolk proportion, yolk weight, egg weight and albumen weight all increased with increasing age of the hen in both selection lines. The difference between selection lines in yolk proportion, yolk weight and albumen weight persisted throughout the laying period. 4. Estimated heritabilities for yolk proportion, yolk weight, egg weight and albumen weight were 0.38, 0.22, 0.34 and 0.41 respectively. The genetic correlation between yolk proportion and yolk weight was 0.52, whereas the genetic correlations with egg weight and albumen weight were -0.51 and -0.74 respectively. 5. We conclude that selection can be used to alter yolk production. Selection can be at an early age with a sustained effect throughout the laying period.     

Genetic relations of yolk proportion and chick weight with production traits in a White Leghorn line

1. The main purpose of this study was to estimate genetic correlations between yolk proportion, chick weight and production traits using an animal model. 2. Direct-direct genetic correlations were estimated between yolk proportion and age at first egg (-0.34), body weight at 20 (0.10), 40 (0.58) and 60 (0.52) weeks of age, egg number (0.56), egg mass (0.59), feed intake (0.64) and feed conversion (-0.25). 3. Maternal-direct genetic correlations were estimated between chick weight and age at first egg (0.40), body weight at 20 (0.57), 40 (0.66) and 60 (0.56) weeks of age, egg number (-0.50), egg mass (0.21), feed intake (0.45) and feed conversion (0.17), respectively. 4. In conclusion, the results suggest that selection on a higher yolk proportion would not have any unfavourable effects on egg production. Maternal-direct genetic correlations between chick weight and production traits resembled direct-direct genetic correlations between egg weight and production traits found in other studies.     

Inbreeding and heterosis effects on quantitative traits in a White Leghorn population under long-term reciprocal recurrent selection

1. Inbreeding and heterosis effects for quantitative traits were estimated in two White Leghorn lines selected with reciprocal recurrent selection (RRS) since 1950. 2. Pedigreed progeny were produced from full-sib, half-sib and unrelated pure line as well as reciprocal cross line matings to estimate inbreeding and heterosis effects "within sires". 3. Inbreeding effects estimated as linear regressions agreed well with estimates considering inbreeding as fixed effect. The inbreeding depression per 10% inbreeding was highest for hatchability (6-7%), intermediate for production-related traits (3%), and about 1% for shell quality, body weight and egg weight. 4. Heterosis effects were estimated by comparing pure line and cross line progeny of the same sires. 5. Results indicate considerably less heterosis for egg production than found earlier, which is interpreted as a consequence of pure line selection.     

Within- and between-strain genetic variability in White Leghorn population detected through RAPD markers

1. Five White Leghorn (WLH) strains, namely G, H, I, J and C, differing in selection history, were screened for randomly amplified polymorphic DNA (RAPD) polymorphism using 50 random decamer primers. 2. Only 12 primers detected polymorphism between the strains. Out of 96 bands scored using these primers, only 21 (21.9%) were found to be polymorphic. 3. Strains differed considerably for within-population genetic similarity, estimated either by band sharing (WS=0.836 to 0.968) or band frequency (WF=0.820 to 0.969). 4. Between-strain genetic similarity estimates, based on band sharing (BS) as well as on band frequency (BF) ranged from 0.756 to 0.958 and from 0.830 to 0.996, respectively. Strains C and H were most closely related to each other, while J appeared to be more distant from other strains. 5. The between-strain genetic distance estimates also revealed similar trends. 6. A phylogenetic tree, derived using Nei's coefficient of similarity revealed similar relationships between the WLH strains.     

Factors affecting direct and correlated responses in a White Leghorn population under long term selection for egg number

1. Data on 13,773 pullets, the progeny of 30 to 50 sires and about 135 to 220 dams per generation of a strain of White Leghorn under long term selection for part period egg production over 16 generations, were examined. 2. Realised genetic gain per generation was highly significant for egg production (2.55 eggs), egg weight (- 0.51 g), age at sexual maturity (- 2.30 d) and 40 week body weight (- 11.73 g). 3. The significant genetic response of 4.46 to 4.72 eggs per generation was realised in the first 8 generations only, which was accompanied by a marked decline in egg weight (- 1.67 and- 0.79 g per generation) and in age at sexual maturity (- 4.63 and- 6.39 d per generation). The 20 and 40 week body weights showed significant improvement in the last 4 generations. 4. Realised heritabilities were much lower in the last 8 than in the first 8 generation. 5. The additive genetic variance for most traits, except 20 week body weight and genetic covariances of egg production with egg weight and age at sexual maturity, declined significantly. 6. Natural selection did not seem to play any major role. No appreciable change in fitness traits was observed in the selected line. 7. The time trends were non-significant for all the traits in the control line, indicating its stability over generations.     

白来航鸡慢羽品系遗传分析

对白来航鸡慢羽品系第９世代的１２个数量性状进行了遗传参数的遗传力、表型相关、遗传相关、环境相关估测与分析,证明该系遗传性能趋于稳定,成为培育高产自别雌雄配套系中一个重要品系。     

Monochromatic green light stimulation during incubation shortened the hatching time via pineal function in White Leghorn eggs

Background:Effect of monochromatic green light illumination on embryo development has been reported in chickens. The avian pineal gland is an important photo-en...     

Effects of restricted feeding in the growing and laying periods on the performance of White Leghorn by Australorp crossbred and White Leghorn strain cross chickens

1. The effects of restricted feeding in the rearing and laying periods on the performance of three White Leghorn cockerel by Australorp pullet crossbred strains and one White Leghorn strain cross were studied in two experiments.

2. After feeding ad libitum in the rearing period, mean body weights of the three crossbred strains at 20 weeks of age were 1.75, 1.66 and 1.55 kg and that of the White Leghorn strain cross was 140 kg. The differing restrictions during rearing reduced mean body weight at 20 weeks by 14 to 33% and increased the time to sexual maturity by 8 to 23 d.

3. All restriction regimes during rearing increased mean egg weight and tended to reduce mortality in the laying period. Optimum hen‐day egg number over 64 weeks of lay was obtained following mild restriction (14% body weight reduction) of the two heavier strains or ad libitum feeding of the lighter strains. Over 48 or 64 weeks of lay, egg number per hen housed (at 18 to 20 weeks of age) was optimised after moderately restricting (14 to 21% body weight reduction) the crossbred strains or feeding the White Leghorn strain cross ad libitum.

4. Over 64 weeks of lay, mortality was reduced from 19.3% to 10.5% in the lightest crossbred strain, in which a high proportion of deaths were associated with Marek's disease and lymphoid leucosis, by restriction during rearing.

5. Restricting food intake by 7 or 8% throughout the laying period reduced hen‐day and hen‐housed egg number and mean egg weight of all four strains. The reduction in hen‐day egg number associated with food restriction during lay was less for the heavier strains that had also been restricted during rearing.

6. Metabolisable energy intakes required to support maximum production over 64 weeks of lay were 1.23 to 1.36 MJ/d.     

添加剂对不同干物质含量的多花黑麦草青贮品质的影响

为分析不同添加剂类型与干物质含量对多花黑麦草(Lolium multiflorum)青贮品质的影响,本研究将3种添加剂处理——甲酸(formic acid,FA)、植物乳杆菌(Lactobacillus plantmentum,LP)、布氏乳杆菌(L.buchneri,LB)添加于3种干物质含量(20%、30%、40%)的多花黑麦草中,青贮60d后,测定不同处理青贮营养成分和发酵品质的相关指标。结果表明,甲酸处理组在3种干物质条件下,其pH均在4.3以下,氨态氮(NH3-N)均显著低于其他处理组(P0.05),而可溶性碳水化合物(water soluble carbohydrate,WSC)含量则显著高于其他处理组(P0.05)。在干物质含量为30%、40%的多花黑麦草中添加两种乳酸菌可以获得较好的发酵效果,其中,LB处理组乙酸含量显著高于其他处理组(P0.05),LP处理组乳酸含量显著高于其他处理组(P0.05)。就干物质含量而言,干物质30%和40%时发酵品质均优于干物质20%时同样的添加剂处理组,且在干物质20%时,对照组和乳酸菌处理组均含有大量的丁酸。因此,在制作多花黑麦草青贮时尽量凋萎使干物质含量保持在30%~40%,同时添加乳酸菌类添加剂是保证青贮料品质的关键。当没有条件凋萎,将鲜样直接青贮时,添加一定量的甲酸(4mL·kg~(-1))是保证青贮料发酵品质的有效手段。     

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.     

不同蛋白质对白来杭鸡产蛋性能的影响试验

各种动物性食品中,以鸡蛋蛋白质的生理价值最高,其中94%能为人体消化吸收.影响鸡产蛋性能的因素有很多,饲料蛋白质是影响产蛋性能的主要因素,国内外研究涉及产蛋鸡对蛋白质需求量的较多,但是对不同蛋白质品质和不同蛋白质水平对产蛋鸡产蛋性能的影响研究尚未见报道.     

Genetic basis of the increase in egg weight with pullet age in a White Leghorn flock

1. In a closed White Leghorn flock over a 6-year period the average increase in egg weight from the start of lay to 37 weeks of age was 12.6 g. 2. The heritability of this egg weight increase was estimated at 0.36 +/- 0.06. 3. The genetic correlations of egg weight increase with other characteristics were: age at first egg -0.50, early egg weight -0.51, 37 week egg weight 0.42 and egg production to 273 d 0.44. 4. It is predicted that with unit selection intensity the direct response in egg weight increase will be -1.30 g, with correlated responses in age at first egg of 2.1 d, early egg weight 0.64 g, 37 week egg weight -0.51 g and egg production to 273 d -1.83 eggs.     

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.     

Strain differences in the erythrocyte and spermatozoan head dimensions of White Leghorn cocks

Differences amongst the length, breadth and area of erythrocyte nuclei, and the length, breadth, shape and area of the heads of spermatozoa were observed in six strains of White Leghorn cocks. Erythrocyte nuclear and spermatozoan head dimensions were negatively correlated. The negative correlations were explained on the basis of cellular oxidation rate.     

闭锁群体BLUP选择下遗传方差和近交系数的变化

采用计算机随机模拟方法模拟了在一个闭锁群体内连续对单个性状进行 1 5个世代选择的情况。选择过程中世代不重叠 ,每个世代的种畜根据动物模型最佳线性无偏预测 (BLUP)法估计的育种值进行选留 ,并在此基础上系统地比较了不同群体规模、公母比例和性状遗传力对群体遗传方差和近交系数变化的影响。结果表明 ,扩大育种群规模、增加公畜比例以及对低遗传力性状进行选择时 ,群体遗传方差降低的速度和近交系数上升的速度会更慢 ,在长期选择时可望获得更大的持续进展和适宜的近交增量     

绿壳蛋鸡与白来航蛋鸡microRNA变异及其靶基因预测分析

本研究旨在分析绿壳蛋鸡与白来航蛋鸡microRNA变异及其靶基因,将已鉴定的microRNA与预测microRNA组成全基因组的microRNA,并通过与GGRS得到的两种鸡群体SNP位点进行映射,挖掘含SNP的microRNA。利用生物信息学的方法,对含SNP的microRNA进行靶基因预测,并对直接含有SNP的mature-microRNA进行聚焦。将这些靶基因进行富集,一共得到22个GO分类和10条KEGG信号通路与3个主要IPA调控网络,发现其在与生长相关的mTOR信号通路、Wnt信号通路、生长激素受体网络、胰岛素样生长因子Ⅰ受体网络得到了富集,与产蛋性状相关的卵母细胞减数分裂信号通路、黄体酮卵母细胞成熟信号通路得到了富集。此研究方法和结果可以给后期研究提供参考。     

Effect of microbial phytase on production performance of White Leghorn layers fed on a diet low in non-phytate phosphorus

1. An experiment with 150 White Leghorn layers was conducted to examine the effect of microbial phytase supplementation of low non-phytate phosphorus (NPP) diets on egg production, eggshell quality, bone mineralisation and retention of nutrients at 32-48 weeks of age. 2. Four isonitrogenous and isocaloric diets were formulated to contain 1.2, 1.8, 2.4 and 3.0 g NPP/kg diet with the two lowest NPP (1.2 and 1.8) supplemented with microbial phytase (Biofeed Phytase, India) at 500 FTU per kg diet. Each diet was offered ad libitum to 5 replicates of 5 layers throughout the experiment. 3. Body weight gain was reduced significantly in the layers fed on the 1.2 g/kg NPP diet as compared to those given diets containing 1.8-3.0 g/kg. Addition of phytase to the 1.2 g/kg diet significantly enhanced the body weight and was comparable with those given diets containing 1.8-3.0 g/kg NPP. 4. No additional advantage resulted from enhancing the NPP levels beyond 1.8 g/kg or adding phytase to a diet containing 1.8 g/kg NPP. 5. Hen d egg production, food intake, food efficiency, shell weight, shell thickness, shell strength and tibia strength followed the same trends as above. However, adding phytase to the 1.8 g/kg NPP diet significantly enhanced tibia ash. Egg weight, specific gravity and Haugh units were influenced by neither NPP concentration nor phytase supplementation. 6. Adding phytase to the 1.2 g/kg NPP diet significantly enhanced nitrogen and phosphorus retention. 7. It was concluded that addition of 500 FTU of microbial phytase/kg diet can allow the reduction of NPP content to 1.2g/kg in the layer diet, eliminate inorganic phosphorus supplementation and results in significant reduction of nitrogen and phosphorus excretion without affecting the production performance of layers.     

Analysis on Target Genes with Mutation in microRNA of Blue-shelled Chicken and White Leghorn

The study was conducted to explore the potential different characters between Blue-shelled chicken and White leghorn.Global genome microRNA was combined the identified microRNA with complementary lab-predicted microRNA.Then the two breed chicken's SNP data got by GGRS were mapped to the microRNA and focused on SNP that deliberately located in mature-microRNA.Bioinformatics method was adopted for target prediction on microRNA which had SNPs.By further gene enrichment analysis,the study found these genes enriched in 22 GO terms,10 KEGG pathways,and 3 IPA important networks.And they enriched in traits which associated with growth,such as mTOR signaling pathways,Wnt signaling pathways,growth hormone receptor networks and insulin-like growth factor Ⅰ receptor networks.And they also enriched in some laying traits,such as oocyte meiotic signaling pathways and progesterone mature oocytes signaling pathways.The methods and the results might provide references for further studies.     

Effect of natural zeolite on yolk: Albumen ratio in hen eggs

1. The egg yolk: albumen (Y:A) ratio during the laying year was investigated in a commercial strain (Hisex) when natural zeolite was added to a layer's diet. 2. Dietary natural zeolite (NZ) increased both egg weight and albumen weight, while yolk weight was not significantly affected. 3. The Y:A ratio was less (more albumen) in eggs laid by hens on zeolite treatments. It was concluded that by feeding NZ it is possible to alter the Y:A ratio.