Molecular genetics of behaviour: research strategies and perspectives for animal production

Genetic factors are undoubtedly involved in inter-individual variability of the behaviours that may be important for livestock production, as shown by pedigree studies, comparison of genetic stocks raised in the same environment, and selection experiments. The knowledge of gene polymorphisms responsible for genetic variability would increase the efficiency of selection, as shown for instance by the identification of the ryanodine receptor gene that harbours the mutations responsible for the porcine stress syndrome, that allows the eradication of the susceptibility allele. One strategy is to screen systematically the genes that are known to be involved in regulation of behaviour (functional candidate genes). This strategy is however very difficult for most behavioural traits, since behaviour is an emerging function from the whole brain/body and the molecular pathways involved in genetic variability are very poorly understood. Another strategy is to investigate linkage between trait variation and genetic markers in a segregating population (usually an intercross or backcross between two strains or breeds contrasting for the trait under study). It allows the detection of genomic regions influencing that trait (quantitative trait loci or QTL), and further investigation aims at the identification of the gene(s) located in each of these regions and the molecular polymorphisms involved in phenotypic variation. Although many QTL have been published for behavioural traits in experimental animals, very few examples are available where strong candidate genes have been identified. Further progress will be very much dependent upon the careful definition of behavioural traits to be studied (including their importance for animal production), on the reliability of their measurement in a large number of animals and on the efficient mastering of environmental factors of variability. The fast increase in the knowledge of genome sequence in several species will undoubtedly facilitate the application to farm animal species of the knowledge obtained in model organisms, as well as the use of model organisms to explore candidate genes detected by QTL studies in farm animals.     

Quantitative trait locus detection in commercial broiler lines using candidate regions

A QTL that explained a large proportion of the phenotypic difference between broiler and layer chickens in an experimental cross was evaluated in a commercial broiler line. A three-generation design, consisting of 15 grandsires, 608 half-sib hens, and more than 50,000 third-generation offspring, was implemented within the existing breeding scheme of a broiler breeding company. Four markers from a candidate region on chicken chromosome 4 were selected for their informativeness in the grandsires and used to genotype the first two generations. Using half-sib analyses, linkage was studied between these markers and 13 growth and carcass traits. The QTL analyses confirmed the presence of significant QTL for body weight (P < 0.01) and residual feed intake (P < 0.05) on chicken chromosome 4. Furthermore, evidence was found for QTL affecting the relative weight of bone and muscle in the thigh. Four more markers were added to increase resolution of the QTL positions. This increased the significance of the QTL for body weight (P < 0.001) and residual feed intake (P < 0.01) and showed evidence (P < 0.05) for additional QTL affecting carcass weight and conformation score. This study showed for the first time that a QTL that explains differences between broilers and layers was segregating in lines that have been selected for body weight over 50 generations. A possible explanation could be a pleiotropic or closely linked effect on fitness-related traits that are not part of the present study. The results demonstrate the feasibility of QTL detection and the potential for marker-assisted selection within a commercial broiler line without altering the existing breeding scheme.     

Influence of Dermanyssus gallinae and Ascaridia galli infections on behaviour and health of laying hens (Gallus gallus domesticus)

(1) The effect of infections with Dermanyssus gallinae (poultry red mite or chicken mite) and Ascaridia galli (roundworm) on the behaviour and health of laying hens was investigated. (2) Six groups of 15 pullets (Isa Brown) were kept in indoor pens from 18 weeks of age. Two groups were artificially infected with D. gallinae, two groups with A. galli and two groups were kept as uninfected controls. The hens were observed for behavioural reactions and physiological changes (weight gain and various blood variables) to the parasitic infections. (3) Infections with D. gallinae resulted in reduced weight gain, anaemia and even death of some of the hens. Behavioural changes were also observed, as the mite-infected hens showed higher self-grooming and head scratching both during the day and night. (4) A. galli resulted in a lower weight gain but no significant changes were seen in blood variables or behavioural activities.     

Quantitative trait loci for milk production and functional traits in two Danish Cattle breeds

Quantitative trait loci (QTL) in Danish Jersey and Danish Red cattle were independently mapped by least squares regression analysis. For Jersey breed, five grandsire families were genotyped for 186 markers on 16 chromosomes (BTAs). Eight traits analysed were milk yield (MY), fat percentage (FP), protein percentage (PP), clinical mastitis (CM), somatic cell score (SCS), maternal stillbirth, maternal calf size (MCS) and maternal calving difficulty. For Red breed, nine grandsire families were genotyped for 166 markers on 18 BTAs. Six traits analysed were MY, FP, PP, CM, SCS and female fertility. Nine and five QTL were detected in Jersey and Red breed, respectively, in across family tests. In Jersey breed, the results indicate QTL for CM and MCS on BTA 3. Additionally, there is an indication of QTL for MCS and FP on BTA 1 and a tentative evidence for a QTL for MY on BTA 26. There is a high risk of detected QTL being false positives. The detected QTL in Jersey breed indicate interesting results from a breeding perspective, but a practical application should await genome-wide association studies.     

The vitamin A supply of laying hens including during rearing. 1. Testing of mixed feed with a varied vitamin A supplementation in chicks and young hens

In seven experiments with 46,310 young animals from hatching to the 21st week the vitamin A supplement varied between 0 and 10,000 IU per kg mixed feed. Feed intake was significantly diminished in three out of seven experiments when chicken feed was given without vitamin A supplement. In the young chicken period 1,500 IU vitamin A supplement were sufficient for optimal body weight development, in the young hen period native carotene was sufficient. The variation of the body weight of the individual animals on the 126th day did not show any connection with vitamin A supply. The carotene content of the rations was sufficient to prevent deficiency symptoms. The livers and yolk sacs of one-day-old chickens on average contained 114 and 56 IU vitamin A/g substance when the parents had received mixed feed with 15,000 IU vitamin A/kg. There is a positive relation between the vitamin A supply of the young chickens and hens and the vitamin A content of the liver.     

威宁鸡体尺与屠宰性状间的相关性研究

试验旨在揭示威宁鸡体尺和屠宰性状的性别差异情况及体尺与屠宰指标间的相关性,参照中国家禽体尺和屠宰性状测定标准对65只(♀:33;♂:32)180日龄公、母威宁鸡的体尺和屠宰性状进行测定和分析。结果发现,威宁鸡体斜长在公、母鸡之间呈现显著差异,公鸡显著高于母鸡(P< 0.05);冠高和胫长公鸡极显著高于母鸡(P< 0.01),体尺和屠宰性状均呈性别差异,较国内其他地方鸡种,威宁鸡表现出了优异的体形外貌特征,体质健壮,肉用性能好,抗逆性强,其中,公鸡较母鸡表现为体形结构大,肉用性能更佳;另外,威宁鸡各体尺性状、多数屠宰性状及多数体尺与屠宰性状间均呈正相关关系,且多数指标间达到了显著或极显著水平(P< 0.05;P< 0.01),这对今后威宁鸡的选育尤其是早期选育具有重要参考意义。     

The Correlative Analysis between Body Size and Slaughter Traits in Wei-ning Chickens

It aimed to investigate the sex differences and correlation of body size and slaughter traits in Wei-ning chicken,the research measured the body size and slaughter traits of 65 Wei-ning chicken(♀:33;♂:32 ) at the age of 180 days according to the nation livestock body size and slaughter measurement standards,and analysis on the correlative between body size and slaughter traits.The results showed that the lean body length was significant difference in the different sex chicken groups (P< 0.05 ),and the cocks were higher than hens,the comb hight and keel bone length of cocks were extremely significant higher than hens (P< 0.01 ).All of the body size and slaughter trait showed difference between cocks and hens,moreover,the Wei-ning chicken also showed excellent appearance,hold the strong body constitution character,good meat performance and adaptability for other native chickens,the body constitution and meat performance of cocks were better than hens.Besides,the different body size,most of slaughter traits and between body size and slaughter traits were positively correlaton,and most of indexes showed the significant or extremely significant correlation levels (P< 0.05;P< 0.01),these data would be crucial insight for the breeding,especial early breeding of Wei-ning chicken.     

Chicken egg antibodies for prophylaxis and therapy of infectious intestinal diseases. V. In vivo studies on protective effects against Escherichia coli diarrhea in pigs

A field study and a controlled infection trial showed the protective effect of egg yolk lyophilisate and whole egg lyophilisate against enterotoxic E. coli germs. The lyophilisates were gained from eggs of hens immunized against pilus antigen of porcine-enterotoxic E. coli. In a first field study using egg yolk antibodies, 92% of 299 diarrhea affected piglets were cured. In a further field study diarrhea affected piglets were cured after 3 days by application of egg yolk lyophilisate from immunized hens. Piglets treated only with egg yolk of not immunized hens showed no signs of recovery. The infection trial showed, that whole egg lyophilisate of immunized hens was as successful as a common antibiotic therapy in curing piglets, orally infected with 5 x 10(10) E. coli/feeding and animal. The present data show that chicken egg antibodies can be used for treatment of infectious diarrheal diseases in young animals. So far they represent a good alternative to the common used antibiotic therapy.     

Onset of sexual maturity in female chickens is genetically linked to loci associated with fecundity and a sexual ornament

Onset of sexual maturation is a trait of extreme importance both evolutionarily and economically. Unsurprisingly therefore, domestication has acted to reduce the time to sexual maturation in a variety of animals, including the chicken. In comparison with wild progenitor chickens [the Red Junglefowl (RJF)], domestic layer hens attain maturity approximately 20% earlier. In addition, domestic layers also possess larger combs (a sexual ornament), produce more eggs and have denser bones. A large quantitative trait loci (QTL) analysis (n=377) was performed using an F(2) intercross between a White Leghorn layer breed and a RJF population, with onset of sexual maturity measured and mapped to three separate loci. This cross has already been analysed for comb mass, egg production and bone allocation. Onset of sexual maturity significantly correlated with comb mass, whilst the genetic architecture for sexual maturity and comb mass overlapped at all three loci. For two of these loci, the QTL for sexual maturity and comb mass were statistically indistinguishable from pleiotropy, suggesting that the alleles that increase comb mass also decrease onset of sexual maturity.     

Perching behaviour and perch height preference of laying hens in furnished cages varying in height

1. The objective was to investigate the effect of cage height on perch height preference and perching behaviour in laying hens. Twelve groups of two hens and 12 groups of 14 hens were tested in furnished cages equipped with two wooden perches. These stepwise perches were designed such that hens could choose between 7 different heights (6, 11, 16, 21, 26, 31 and 36 cm). Day- and night-time perching behaviour was observed on 4 consecutive days with a different cage height each day: 150, 55, 50 and 45 cm. 2. Given that a minimum perch-roof distance of 19 to 24 cm was available, hens preferred to roost on the highest perches at night. 3. Lowering cage height not only forced hens to use lower perches, but also reduced time spent on the perches during the day (two-hen and 14-hen test) and night (14-hen test). Moreover, it affected daytime behavioural activities (more standing and less preening) on the perches in the two-hen tests (but not in the 14-hen tests). 4. During the day lower perches were used more for standing and walking, higher perches more for sitting and sleeping. This behavioural differentiation was most pronounced in the highest cages. 5. Perch preference and perching behaviour depend on both the floor-perch distance and the perch-roof distance. Higher cages provide more opportunity for higher perches (which hens prefer), for better three-dimensional spacing (and consequently reduced density at floor level) and for behavioural differentiation according to perch height.     

Fundamental ethological and ecological aspects for the husbandry of domestic animals, especially for hens

The significance of ethology applied to farm animals is demonstrated from 1. a broader point of view and 2. focussed on the management of poultry. The topic of animal ethology is the study of their behaviour. Basic functions of animal behaviour are satisfaction of their requirements and needs including reproduction and avoidance of harm. A significant task for ethologists is the scientific elaboration of the animals' interactions with their surrounding, in their keeping system. The documented information aim to show how to satisfy the basic behavioural and physiological needs of hens and how to produce eggs of high quality in adequate quantity in respect also to the environment.     

Artificial lighting in poultry houses: Do hens perceive the modulation of fluorescent lamps as flicker?

1. Many poultry houses are illuminated by fluorescent lamps which produce discontinuous illumination with a frequency of either 100 or 120 Hz. 2. This study investigated whether domestic fowls perceive this discontinuity as flicker by training two Leghorn hens to choose between a continuous and a discontinuous light, all other variables being identical. 3. The light-stimulus was either monochromatic with 100% sinusoidal modulation or a fluorescent lamp whose modulation frequency could be electrically adjusted. 4. Each (correct) choice for the discontinuous light was followed by a 5 Hz higher frequency, whereas an incorrect choice was followed by a 10 Hz lower frequency. 5. On the basis of this principle the animals themselves established the highest perceivable frequency of the discontinuous light, called the Critical Fusion Frequency (CFF), that they could discriminate from continuous light. 6. These frequencies typically depend on the stimulus intensity increasing with increasing intensities, until a maximum value is reached. 7. Two factors limited the magnitudes of the CFF's that were recorded: the maximum stimulus intensities produced and variability in the chicken's response ("behavioural noise"). In spite of these constraints 105 Hz was established as the maximum CFF. 8. On the basis of extrapolation it is concluded that the direct light from fluorescent lamps driven by 50 Hz alternating current is seen by the chicken as flickering. 9. The results justify large-scale comparison of behaviour and production in poultry houses that are illuminated either by low-frequency or by high-frequency fluorescent lamps.     

Choice of breeding stock,preference of production traits and culling criteria of village chickens among Zimbabwe agro-ecological zones

Free ranging chickens reared by smallholder farmers represent genetic diversity suited for particular environments and shaped by the socio-economic and cultural values of the farming systems. This study sought to investigate the existence of chicken strains and evaluate the breeding goals and strategies used by village chicken farmers in Zimbabwe. A semi-structured questionnaire was administered to 97, 56, 70, 104 and 37 households randomly selected from five agro-ecological-zones I-V, respectively. Fifteen chicken strains mostly defined by morphological traits were reported in the five eco-zones. Production criteria such as body size, and fertility were highly ranked (ranging from 1.3 – 2.6) by farmers across all the eco-zones, while cultural traits were the least preferred production traits. As a common breeding practice, farmers chose the type of hens and cocks to retain for breeding purposes and these randomly mixed and mated with others from community flocks. Chicken body size was ranked the major determinant in choosing breeding animals followed by mothering ability, and fertility. More households culled chickens associated with poor reproductive performance, poor growth rates and those intolerant to disease pathogens. The focus on many negatively correlated production traits and the absence of farmer records compromises breeding strategies in these production systems.     

Genetic background of maternal behaviour and its relation to offspring survival

Maternal behaviour is becoming increasingly important in animal production. Selection for increased litter size at birth in pigs and sheep puts higher demands on the ability of dams to raise large litters. In pig production, the use of loose housing systems for lactating sows increases the importance of good maternal behaviour. Extensive production systems (e.g., ecological farming and outdoor production), where there is a small degree of supervision of the animals, also leaves a greater responsibility with the mother to care for her young. The environment provided by the dam is important for the survival and growth of the offspring in many species. Several behaviour traits of the mother play a role for the offspring's chances of survival and a good start in life. Examples of such behaviour traits are responsiveness towards signals from the offspring (pigs), aggressive behaviour towards the offspring (pigs and sheep), nursing behaviour (pigs and sheep), and fear behaviour (pigs, sheep, and cattle). Some of these traits are in part genetically controlled, and thus possible to improve by selection. Behaviour traits are, however, often difficult to observe and record on a large scale. By studying behaviour, we can gain further understanding about factors affecting survival of the young, and increase our chances to improve maternal behaviour. Improved maternal behaviour would increase the welfare for both mother and young.     

鸡的微卫星DNA标记与胴体性状的相关分析

测定了青脚麻鸡与隐性白鸡杂交后自交的F2代个体的全净堂重、全净堂率、脂肪宽带、腹脂重和腹脂率6个胴体性状,检测10个微卫星DNA标记,对标记基因型胴体性状值进行方差分析和多重比较,结果表明:MCW328对于10周龄体重和全净膛重两性状各基因型均有显著的差异(P<0.05);ADL292对于腹脂重性状各基因型有极显著的差异(P<0.01),对于腹脂率有显著的差异(P<0.05)。MCW328标记基因与控制10周龄体重和全净膛重QTL连锁,ADL292标记基因与控制腹脂重和腹脂率QTL连锁。     

Mapping quantitative trait loci for metabolic and cytological fatness traits of connected F2 crosses in pigs

In the present study 3 connected F(2) crosses were used to map QTL for classical fat traits as well as fat-related metabolic and cytological traits in pigs. The founder breeds were Chinese Meishan, European Wild Boar, and Pietrain with to some extent the same founder animals in the different crosses. The different selection history of the breeds for fatness traits as well as the connectedness of the crosses led to a high statistical power. The total number of F(2) animals varied between 694 and 966, depending on the trait. The animals were genotyped for around 250 genetic markers, mostly microsatellites. The statistical model was a multi-allele, multi-QTL model that accounted for imprinting. The model was previously introduced from plant breeding experiments. The traits investigated were backfat depth and fat area as well as relative number of fat cells with different sizes and 2 metabolic traits (i.e., soluble protein content as an indicator for the level of metabolic turnover and NADP-malate dehydrogenase as an indicator for enzyme activity). The results revealed in total 37 significant QTL on chromosomes 1, 2, 4, 5, 6, 7, 8, 9, 14, 17, and 18, with often an overlap of confidence intervals of several traits. These confidence intervals were in some cases remarkably small, which is due to the high statistical power of the design. In total, 18 QTL showed significant imprinting effects. The small and overlapping confidence intervals for the classical fatness traits as well as for the cytological and metabolic traits enabled positional and functional candidate gene identification for several mapped QTL.     

Mixture models detect large effect QTL better than GBLUP and result in more accurate and persistent predictions

Background: Accurate evaluation of SNP effects is important for genome wide association studies and for genomic prediction. The genetic architecture of quantitative traits differs widely, with some traits exhibiting few if any quantitative trait loci(QTL) with large effects, while other traits have one or several easily detectable QTL with large effects.Methods: Body weight in broilers and egg weight in layers are two examples of traits that have QTL of large effect.A commonly used method for genome wide association studies is to fit a mixture model such as Bayes B that assumes some known proportion of SNP effects are zero. In contrast, the most commonly used method for genomic prediction is known as GBLUP, which involves fitting an animal model to phenotypic data with the variance-covariance or genomic relationship matrix among the animals being determined by genome wide SNP genotypes. Genotypes at each SNP are typically weighted equally in determining the genomic relationship matrix for GBLUP. We used the equivalent marker effects model formulation of GBLUP for this study. We compare these two classes of models using egg weight data collected over 8 generations from 2,324 animals genotyped with a42 K SNP panel.Results: Using data from the first 7 generations, both Bayes B and GBLUP found the largest QTL in a similar well-recognized QTL region, but this QTL was estimated to account for 24 % of genetic variation with Bayes B and less than 1 % with GBLUP. When predicting phenotypes in generation 8 Bayes B accounted for 36 % of the phenotypic variation and GBLUP for 25 %. When using only data from any one generation, the same QTL was identified with Bayes B in all but one generation but never with GBLUP. Predictions of phenotypes in generations 2 to 7 based on only 295 animals from generation 1 accounted for 10 % phenotypic variation with Bayes B but only6 % with GBLUP. Predicting phenotype using only the marker effects in the 1 Mb region that accounted for the largest effect on egg weight from generation 1 data alone accounted for almost 8 % variation using Bayes B but had no predictive power with GBLUP.Conclusions: In conclusion, In the presence of large effect QTL, Bayes B did a better job of QTL detection and its genomic predictions were more accurate and persistent than those from GBLUP.     

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。     

A pecking device as an environmental enrichment for caged laying hens

To improve the welfare of caged laying hens, a pecking device made of stones was introduced on the cage floor. Twenty‐four White Leghorn hens aged 15 months were divided into four groups: single‐housed hens with device, single‐housed control hens, pair‐housed hens with device and pair‐housed control hens. Hens housed with the device pecked at various pecking objects less often than control hens. Agonistic behavior was also lower in hens with the device than in hens without the device, implied a possibility of improvement in quality of pecking stimuli with the device. Not only time spent pecking, but also quality of pecking might be important to fill their need for stimulation. Both single‐ and pair‐housed hens more often pecked at the device in the evening. Response to various pecking objects also showed that pecking behaviors were most frequently expressed in the evening. Increased foraging at dusk is a well‐known habit; therefore, the increase in pecking behavior in the evening might reflect the hens' general circadian rhythm. These results indicate that the device made of stones could promote some instinctive behavior. Enhancement of behavioral repertories and reduced agonistic behavior with the pecking device might improve the welfare of caged laying hens.