Genome‐wide association study for egg production and quality in layer chickens

Discovery of genes with large effects on economically important traits has for many years been of interest to breeders. The development of SNP panels which cover the whole genome with high density and, more importantly, that can be genotyped on large numbers of individuals at relatively low cost, has opened new opportunities for genome‐wide association studies (GWAS). The objective of this study was to find genomic regions associated with egg production and quality traits in layers using analysis methods developed for the purpose of whole genome prediction. Genotypes on over 4500 birds and phenotypes on over 13 000 hens from eight generations of a brown egg layer line were used. Birds were genotyped with a custom 42K Illumina SNP chip. Recorded traits included two egg production and 11 egg quality traits (puncture score, albumen height, yolk weight and shell colour) at early and late stages of production, as well as body weight and age at first egg. Egg weight was previously analysed by Wolc et al. ( 2012 ). The Bayesian whole genome prediction model – BayesB (Meuwissen et al. 2001 ) was used to locate 1 Mb regions that were most strongly associated with each trait. The posterior probability of a 1 Mb window contributing to genetic variation was used as the criterion for suggesting the presence of a quantitative trait locus (QTL) in that window. Depending upon the trait, from 1 to 7 significant (posterior probability >0.9) 1 Mb regions were found. The largest QTL, a region explaining 32% of genetic variance, was found on chr4 at 78 Mb for body weight but had pleiotropic effects on other traits. For the other traits, the largest effects were much smaller, explaining <7% of genetic variance, with regions on chromosomes 2, 12 and 17 explaining above 5% of genetic variance for albumen height, shell colour and egg production, respectively. In total, 45 of 1043 1 Mb windows were estimated to have a non‐zero effect with posterior probability > 0.9 for one or more traits.     

近50年全球家畜生产分析

1962-2002年,全球家畜存栏量增加2倍,禽、猪和牛分别增加3倍、1.2倍和42.8%;目前中国牛、羊和猪存栏量分别占全球的1/10、1/5和1/2;发展中国家各种家畜存栏连续增多,发达国家除禽外其余家畜开始减少,与人口和产业结构调整有关。发展中国家家畜个体生产效率虽低于发达国家,但提升幅度高于后者。当前专门化家畜生产贡献全球3/4的禽肉、1/2以上的猪肉和2/3的蛋类,猪、禽和牛肉占94%的肉类总产量,我国猪、禽和牛肉产量分别占全球的55.7%、23.6%和13.2%。1961-2008年,发展中国家肉类和奶类人均年消费量的平均增幅分别为0.43和0.57kg/年,高于发达国家的0.28和0.25kg/年。2002年,全球年均饲草料消耗比1962年增加66%,牛、猪和禽的消耗分别为48.9%、16.8%和12.5%,所占饲草料生产用地的比例则分别为30.7%、31.7%和23.6%。     

Dominance genetic and maternal effects for genetic evaluation of egg production traits in dual-purpose chickens

• 1.?A study was conducted to study direct dominance genetic and maternal effects on genetic evaluation of production traits in dual-purpose chickens. The data set consisted of records of body weight and egg production of 49 749 Mazandaran fowls from 19 consecutive generations. Based on combinations of different random effects, including direct additive and dominance genetic and maternal additive genetic and environmental effects, 8 different models were compared.

• 2.?Inclusion of a maternal genetic effect in the models noticeably improved goodness of fit for all traits. Direct dominance genetic effect did not have noticeable effects on goodness of fit but simultaneous inclusion of both direct dominance and maternal additive genetic effects improved fitting criteria and accuracies of genetic parameter estimates for hatching body weight and egg production traits.

• 3.?Estimates of heritability (h²) for body weights at hatch, 8 weeks and 12 weeks of age (BW0, BW8 and BW12, respectively), age at sexual maturity (ASM), average egg weights at 28–32 weeks of laying period (AEW), egg number (EN) and egg production intensity (EI) were 0.08, 0.21, 0.22, 0.22, 0.21, 0.09 and 0.10, respectively. For BW0, BW8, BW12, ASM, AEW, EN and EI, proportion of dominance genetic to total phenotypic variance (d²) were 0.06, 0.08, 0.01, 0.06, 0.06, 0.08 and 0.07 and maternal heritability estimates (m²) were 0.05, 0.04, 0.03, 0.13, 0.21, 0.07 and 0.03, respectively. Negligible coefficients of maternal environmental effect (c²) from 0.01 to 0.08 were estimated for all traits, other than BW0, which had an estimate of 0.30.

• 4.?Breeding values (BVs) estimated for body weights at early ages (BW0 and BW8) were considerably affected by components of the models, but almost similar BVs were estimated by different models for higher age body weight (BW12) and egg production traits (ASM, AEW, EN and EI). Generally, it could be concluded that inclusion of maternal effects (both genetic and environmental) and, to a lesser extent, direct dominance genetic effect would improve the accuracy of genetic evaluation for early age body weights in dual-purpose chickens.

     

The critical importance of planned small ruminant livestock health and production in addressing global challenges surrounding food production and poverty alleviation

ABSTRACT

Small ruminants are particularly well suited to meet United Nations Sustainable Development Goals surrounding food security, human wellbeing and poverty alleviation in different environmental and climatic settings. However the current efficiency of food production from small ruminants in both developed agricultural regions and in lower and middle income countries is woefully inadequate to meet predicted global needs over the forthcoming decades. Most global research to address this challenge is focussed on the genetics of animal growth, conformation and disease tolerance or resistance traits, albeit the practical consequences of such selection and strategies to use genetically improved animals in the field are uncertain. Any long-term benefits derived from small ruminant genetic selection will only be impactful if steps are first taken to keep animals alive, healthy and productive through iterative planned health management. Parasites are the foremost global infectious disease constraints to efficient small ruminant production. Their genetic adaptability to exploit opportunities afforded by effects of climatic or management changes on free-living stages, or exposure of parasitic stages to drugs, presents specific challenges to their sustainable control. Hence, parasite control provides a relevant means of engagement with livestock keepers and farmers on the topic of planned animal health management. The value of parasitology in this regard is enhanced by the availability of simple to use and accessible diagnostic tools.     

骨疏康在集约化鸡场的应用及其对产蛋后期蛋鸡生产性能、蛋壳品质和骨代谢的影响

选择1000只55周龄的蛋鸡,随机分为2组。对照组饲喂基础日粮,骨疏康组在基础日粮中添加1％的骨疏康,试验期为10周。结果显示,与对照组比较,骨疏康组的破壳蛋率和料蛋比显著降低,产蛋率、蛋壳强度,骨指数、骨放射密度、皮质骨厚度、皮质骨面积百分率,骨强度显著增加,而血清骨代谢生化标志物血钙、血磷和血清碱性磷酸酶水平则显著降低。表明骨疏康可用于集约化蛋鸡场,并显著提高产蛋后期蛋鸡的生产性能和蛋壳品质,改善骨代谢。     

育成期日粮蛋白质和能量水平对农大3号节粮小型蛋鸡生长性能及产蛋高峰期产蛋性能的影响

试验选用84日龄农大3号节粮小型蛋鸡540只,采用3×3因子试验设计,随机分成9个处理,每个处理5个重复。蛋白质水平分别为15%、16%、17%,代谢能水平分别为11.50、11.70、11.91 MJ/kg,旨在研究不同蛋白质和代谢能水平对农大3号节粮小型蛋鸡育成期(13～18周龄)生长以及产蛋高峰期(27～30周龄)产蛋率的影响。结果表明:育成期日粮蛋白质和能量水平对农大3号节粮小型蛋鸡生长性能和产蛋率影响差异不显著(P>0.1)。但二者存在交互作用,日粮蛋白质水平17%、能量水平11.91 MJ/kg处理组提高了育成期增重,并降低了料肉比。总之,同时提高育成期日粮蛋白质和能量水平能改善农大3号节粮小型蛋鸡群体均匀度,对生长具有积极作用。     

饲料中添加白术多糖对林下养殖绿壳蛋鸡生产性能与蛋品质的影响

为研究饲料中添加白术多糖对林下养殖绿壳蛋鸡生产性能与蛋品质的影响,试验选用28周龄产蛋的东乡黑羽绿壳蛋鸡540只,随机分为3组,每组3个重复,每个重复60只,1组为对照组饲喂基础日粮,试验2、3组分别在基础日粮中添加2.5%、5.0%白术多糖,预饲期7 d,试验期28 d。在试验期间,测定林下养殖绿壳蛋鸡生产性能和蛋品质。结果表明:(1)试验3组产蛋率和平均蛋重分别较对照组提高7.33%、6.26%(P <0.05);试验3组料蛋比较对照组降低12.64%(P <0.05);试验2、3组的商品合格率、日产蛋量、日均采食量均高于1组,差异不显著(P> 0.05)。(2)试验3组蛋质量、哈夫单位、蛋壳厚度分别较对照组提高5.63%、3.02%、6.12%(P <0.05);试验2、3组的蛋形指数、蛋黄颜色、蛋黄比例均高于1组,差异不显著(P> 0.05)。综上所述,在基础饲料中添加5.0%白术多糖可以提高林下养殖绿壳蛋鸡生产性能与蛋品质。     

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.     

蛋氨酸对开产蛋鸡生产性能及蛋品质的影响

以19周龄开产海兰褐蛋鸡为试验动物,采用饲养、屠宰试验和蛋品质分析测定等方法,研究蛋氨酸对开产蛋鸡生产性能及蛋品质的影响。结果表明:除添加0.4%组部分指标劣于对照组外,各试验组蛋品质均有不同程度提高,且以添加0.2%蛋氨酸水平组影响最显著,较对照组日均产蛋率、蛋壳厚度、蛋黄指数分别提高5.94%、9.0%、9.84%(P<0.05),料蛋比和蛋黄中胆固醇含量降低8.29%和1.67%(P<0.05)。     

Rare earth element‐enriched yeast improved egg production and egg quality in laying hens in the late period of peak egg production

The objective of this study was to determine the effects of rare earth element‐enriched yeast (RY) on egg production, coefficient of total tract apparent digestibility (CTTAD), egg quality, excreta gas emission and excreta microbiota of laying hens. A total of 216 ISA brown laying hens of 52 weeks of age were used in a 5‐week feeding trial and data were collected every week. Birds were randomly allotted to three dietary treatments each with six replicates and 12 hens per replicate. Each cage (38 cm width × 50 cm length × 40 cm height) contained one hen. Treatments consisted of corn–soya bean meal‐based diet supplemented with 0, 500 or 1000 mg/kg of RY. From weeks 55 to 56, inclusion of RY linearly increased (p < 0.05) egg production. The CTTAD of nitrogen was increased (linear, p < 0.05) with increasing dietary level of RY. In week 55, yolk height and Haugh units were increased linearly (p < 0.05) with increasing dietary RY content. However, no significant effects were observed in terms of excreta emissions and excreta microbiota in laying hens. In conclusion, dietary supplementation with RY improved egg production and CTTAD of nitrogen and slightly improved egg quality in laying hens of the late period of peak egg production.     

Polymorphisms in GnRHI and GnRHII genes and their association with egg production and egg quality traits in chicken

1. Two candidate genes, namely, Gonadotropin releasing hormone I (GnRHI) and Gonadotropin releasing hormone II (GnRHII) play pivotal roles in ovulation and egg production in chicken. The objective of this study was to explore polymorphism in these genes and to estimate the effects of polymorphism of these two genes on egg production and egg quality traits in White Leghorn laying hens.

2. Single strand conformation polymorphism followed by sequencing was performed to detect polymorphism in these genes.

3. The coding regions of the GnRHI and GnRHII genes were found to be polymorphic. In the GnRH1 gene, 12 haplotypes were determined, of which the h1 haplotype was predominant and the h5, h9 and h11 haplotypes were the least frequent ones. In the GnRHII gene, eight haplotypes were found, of which the h1 haplotype was the most frequent and the h6 was the least frequent haplotype in the White Leghorn population.

4. The haplogroups of GnRHI had a significant effect on body weight and egg production up to 64 weeks of age, yolk content, Haugh units and egg shell parameters. The h1h2 haplogroup of the GnRHI gene showed the highest egg production, with 211.0 ± 24.3 eggs up to 64 weeks of age, while the highest yolk content and Haugh unit was found in h3h10 haplogrouped birds. The haplogroups of GnRHII had a significant effect on age at sexual maturity (ASM) where the shortest ASM was found in the h1h4 birds (147.3 ± 5.9 d) and the longest ASM was observed in the h1h3 birds (160.6 ± 23.4 d).

5. It was concluded that GnRHI and GnRHII genes are polymorphic and have a significant effect on body weight, egg production and egg quality traits in White Leghorn laying hens.     

Effects of feeding fermented fish on egg cholesterol content in hens

This study was conducted to investigate the effects of feeding fermented fish (FF) to layers on laying performance, and polyunsaturated fatty acid and cholesterol levels in eggs and plasma. A total of 96, 13-week-old Babcock B380 pullets were used in this study. They were randomly assigned to four numerically equal groups with eight replicates per treatment, three birds per replicate. All the birds were housed in individual cages. The dietary treatments were: Control diet, without FF; FF3 diet containing 3% (w/w) FF, FF6 diet containing 6% (w/w) FF and FF9 diet containing 9% (w/w) FF. The study was carried out for 16 weeks inclusive of two weeks of adjustment. Weekly feed intake and egg production were recorded. Blood plasma cholesterol and fatty acid profiles were assayed at the end of the experiment. FF did not enhance ( P  > 0.05) egg mass but ( P  < 0.05) decreased egg weight slightly. However, egg yolk cholesterol and plasma cholesterol concentrations were reduced ( P  < 0.05) by FF. The n-6:n-3 fatty acids ratio in the egg yolk (Control = 7.9, FF9 = 6.2) and plasma (Control = 10.6, FF9 = 6.2) were decreased by feeding FF. Moreover, FF was able to increase ( P  < 0.05) the docosahexaenoic acid (DHA) concentrations in egg yolk and plasma. In conclusion, this study demonstrated that FF increased DHA and reduced egg yolk cholesterol in poultry eggs.     

Genetic parameters and trends for production traits and their relationship with litter traits in Landrace and Yorkshire pigs

Genetic parameters and trends in the average daily gain (ADG), backfat thickness (BF), loin muscle area (LMA), lean percentage (LP), and age at 90 kg (D90) were estimated for populations of Landrace and Yorkshire pigs. Additionally, the correlations between these production traits and litter traits were estimated. Litter traits included total born (TB) and number born alive (NBA). The data used for this study were obtained from eight farms during 1999 to 2016. Analyses were carried out with a multivariate animal model to estimate genetic parameters for production traits while bivariate analyses were performed to estimate the correlations between production and litter traits. The heritability estimates were 0.52 and 0.43 for ADG; 0.54 and 0.45 for BF; 0.25 and 0.26 for LMA; 0.54 and 0.48 for LP; and 0.56 and 0.46 for D90 in the Landrace and Yorkshire breeds, respectively. The ADG and D90 showed low genetic correlation with BF and LP. The LMA had ?0.40, ?0.32, 0.49, and 0.39 genetic correlations with ADG, BF, LP, and D90, respectively. Genetic correlations between production and litter traits were generally low, except for the correlations between LMA and TB (?0.23) in Landrace and ADG and TB (?0.16), ADG and NBA (?0.18), D90 and TB (0.19), and D90 and NBA (0.20) in Yorkshire. Genetic trends in production traits were all favorable except for LMA.     

混饲鲜树叶糊浆对蛋鸡生产性能及蛋品质的影响

试验选用360只45周龄的海兰白蛋鸡,随机分成3组,每组设3个重复,每个重复40只,对照组喂基础日粮,试验1、2组为基础日粮分别加鲜树叶糊浆25g/d·只和50g/d·只。试验结果表明:混饲鲜树叶糊浆分别提高蛋鸡产蛋率为4.3、7.5个百分点,饲料报酬提高5.26%和10.5%,显著提高蛋壳厚度和蛋壳强度,降低鸡蛋的破损率,明显提高了经济效益。     

Factors affecting egg production and layer bird mortality in private poultry farms in the subhumid zone of Nigeria

Egg production and layer bird mortality data obtained from five different private farms in Zaria within the subhumid zone of Nigeria, over a 6‐year period (1994–1999) were subjected to least squares analysis to determine the effects of age, season and year. It was demonstrated that age had a highly significant influence (P < 0.01) on egg production in that birds falling within the age group 30–39 weeks produced the highest number of eggs (3255 ± 109), while birds over 100 weeks of age produced the lowest number of eggs (1206 ± 412). Similarly, seasonal variation in egg production was also significant (P < 0.05); the highest egg production (2926 ± 90) was obtained during the early dry season, and the lowest (2423 ± 95) during the late wet season. Mortality was generally low (0.0–0.9%) and not significantly different from 20 to 49 weeks of age (P > 0.05). However, from 50 to 100 weeks of age, highly significant differences (P < 0.01) in mortality were observed, with the 90–100 weeks age group recording the highest mortality of 15.7 ± 1.3%. Furthermore, yearly variations in egg production and mortality were highly significant (P < 0.01) with 1999 producing the most eggs (4410 ± 102) and recording the lowest mortality (1.4%). It was concluded that due to the significant seasonal, age and yearly variations, data on egg production and mortality need to be adjusted for these effects to enable unbiased comparison between and within farms. Furthermore, farmers can make adequate feeding preparations commensurate with each season for optimal egg production.     

Genetic relationships between length of productive life and lifetime production efficiency in a commercial swine herd in Northern Thailand

Genetic parameters and trends for length of productive life (LPL), lifetime number of piglets born alive per year (LBAY), lifetime number of piglets weaned per year (LPWY), lifetime litter birth weight per year (LBWY) and lifetime litter weaning weight per year (LWWY) were estimated using phenotypic records of 3085 sows collected from 1989 to 2013 in a commercial swine farm in Northern Thailand. The five‐trait animal model included the fixed effects of first farrowing year‐season, breed group and age at first farrowing. Random effects were animal and residual. Heritability estimates ranged from 0.04 ± 0.02 for LBWY to 0.17 ± 0.04 for LPL. Genetic correlations ranged from 0.66 ± 0.14 between LPL and LBAY to 0.95 ± 0.02 between LPWY and LWWY. Spearman rank correlations among estimated breeding values for LPL and lifetime production efficiency traits tended to be higher for boars than for sows. Sire genetic trends were negative and significant for all traits, except for LPWY. Dam genetic trends were positive and significant for all traits. Sow genetic trends were mostly positive and significant only for LPWY and LBWY. Improvement of LPL and lifetime production efficiency traits will require these traits to be included in the selection indexes used to choose replacement boars and gilts in this population.     

Trial for detecting carriers with major genes in a selected layer line

Production traits of a Rhode Island Red layer line were analyzed to detect carrier animals with major genes that influenced a particular trait by applying the major gene index (MGI) approach. This method was used to examine the deviation of predicted breeding values between parents and offspring. Advantages of this method include its simplicity and time‐reducing, cost‐saving benefits compared with any other statistical approach for screening major genes. The layer line had been selected based on the desired gain index for 6 years at the National Livestock Breeding Center, Okazaki station. The line consisted of 125 sires and 2986 dams. Two economic traits as breeding objectives were studied – age at sexual maturity (ASM, days) and egg production efficiency (EP, %). The MGI detected nine sires and 23 dams as carriers with major genes for ASM, and five sires and 26 dams for EP. They were identified as important breeding stock, and pedigree information provided candidates possessing major genes with favorable effect at the founding of the selected layer line. It seems likely that the simple approach of the MGI could be a useful preliminary method for detecting carrier animals with major genes before applying molecular techniques on a sampled population to identify in more detail the existence of major genes and their carriers.     

Improving production efficiency in the presence of genotype by environment interactions in pig genomic selection breeding programmes

We simulated a genomic selection pig breeding schemes containing nucleus and production herds to improve feed efficiency of production pigs that were cross‐breed. Elite nucleus herds had access to high‐quality feed, and production herds were fed low‐quality feed. Feed efficiency in the nucleus herds had a heritability of 0.3 and 0.25 in the production herds. It was assumed the genetic relationships between feed efficiency in the nucleus and production were low (r_g = 0.2), medium (r_g = 0.5) and high (r_g = 0.8). In our alternative breeding schemes, different proportion of production animals were recorded for feed efficiency and genotyped with high‐density panel of genetic markers. Genomic breeding value of the selection candidates for feed efficiency was estimated based on three different approaches. In one approach, genomic breeding value was estimated including nucleus animals in the reference population. In the second approach, the reference population was containing a mixture of nucleus and production animals. In the third approach, the reference population was only consisting of production herds. Using a mixture reference population, we generated 40–115% more genetic gain in the production environment as compared to only using nucleus reference population that were fed high‐quality feed sources when the production animals were offspring of the nucleus animals. When the production animals were grand offspring of the nucleus animals, 43–104% more genetic gain was generated. Similarly, a higher genetic gain generated in the production environment when mixed reference population was used as compared to only using production animals. This was up to 19 and 14% when the production animals were offspring and grand offspring of nucleus animals, respectively. Therefore, in genomic selection pig breeding programmes, feed efficiency traits could be improved by properly designing the reference population.     

Economic and environmental assessments of combined genetics and nutrition optimization strategies to improve the efficiency of sustainable pork production

We evaluated the economic and environmental impacts of strategies that incorporated selection for pig feed efficiency and dietary optimization based on a single or multiple objectives tailored to meet the population nutritional requirements, with the goal to optimize sustainable farm feed efficiency. The economic and environmental features of the strategy were evaluated using life cycle assessment (LCA) and bio-economic models. An individual trait-based LCA model was applied to evaluate global warming potential, terrestrial acidification potential, freshwater eutrophication potential (EP), and land occupation of the combined genetics and nutrition optimization to produce 1 kg of live pig weighing 120 kg at the farm gate. A parametric individual trait-based bio-economic model was developed and applied to determine the cost breakdown, revenue, and profit to be gained from a 120-kg live pig at the farm gate. Data from two genetic lines with contrasted levels of feed efficiency were used to apply the combined genetics and nutrition optimization: accounting for the average nutritional requirements for each line, the individual pig responses to diets formulated for least cost, least environmental impacts, or minimum combination of costs and environmental impacts objectives were predicted with INRAPorc. Significant differences in the environmental impacts (P < 0.0001) and profit (P < 0.05) between lines predicted with the same reference diet showed that selection for feed efficiency (residual feed intake) in pigs improves pig production sustainability. When pig responses were simulated with their line-optimized diets, except for EP, all the line environmental impacts were lower (P < 0.05) than with the reference diet. The high correlations of feed conversion ratio with the environmental impacts (> 0.82) and the profit (< −0.88) in both lines underlined the importance of feed efficiency as a lever for the sustainability of pig production systems. Implementing combined genetics and nutrition optimization, the inherent profit and environmental differences between the genetic lines were predicted to be reduced from 23.4% with the reference diet to 7.6% with the diet optimized jointly for economic and environmental objectives (joint diet). Consequently, for increased pig sustainability, diet optimization for sustainability objectives should be applied to cover the specific nutritional requirements arising in the herd from the pigs genetic level.