Grazing behaviour of free-ranging donkeys and Shetland ponies in different reproductive states

We investigated how free-ranging mares of two species of equids (donkeys and Shetland ponies) modify their foraging behaviour to meet the increased nutritional requirements induced by lactation. We initially hypothesised that lactating mares would graze for a longer time and/or graze faster than non-lactating (dry) mares. The grazing behaviour of free-ranging animals, foraging in two low-productive dune areas, was recorded during 1 year. Results show that in both species lactating animals did not spend more time grazing than non-lactating mares. However, lactating animals took more bites, and therefore achieved a higher bite rate than dry mares. Several factors affected the differences between lactating and non-lactating animals. Lactating mares took more bites only in grassy and rough vegetations and they did this only in patches with a short sward height. In addition, lactating mares took more bites of grasses only and not of forbs or woody plants. We conclude that the extra grazing effort of the lactating animals was not distributed randomly. Lactating mares invested their extra grazing effort principally towards those items that are the most grazed by the equids in general. We propose some hypotheses to explain why lactating mares increase their bite rate instead of augmenting the time spent grazing.     

Sensory varieties in concentrate diets for stabled horses: effects on behaviour and selection

There is little published information about feeding behaviour of horses presented with concentrate diets and whether restricted variety affects foraging behaviour on concentrate diets is currently unclear. This study investigated the effects of sensory variety on diet selection and behaviour of stabled horses. In three replicated trials, four low energy concentrates were presented. In trial 1 formulation varied with no added flavourants, in trial 2 formulation and flavour varied, in trial 3 formulation was constant and flavour varied.

Up to eight horses were observed in two identical stables containing, either a single concentrate feed or four concentrate feeds (multiple concentrates) for 5 min. To control for palatability each concentrate was presented as the single concentrate twice within each trial. Trials were videotaped and 12 mutually exclusive behaviour patterns compared.

Significant differences (P < 0.05 − P < 0.001) in foraging and non-foraging behaviour were recorded between single and multiple sessions in trials 1, 2 and 3. In all trials the concentrate available in the single concentrate sessions was shown to influence diet selection during multiple sessions. In trial 3, four otherwise identical base diets flavoured with molasses, garlic, mint or herbs, tested whether manipulating flavour was sufficient to affect behaviour and diet selection. When multiple and single session behaviour was compared horse foraged more frequently (P < 0.005) and for longer (P < 0.05) in multiple sessions but foraging bouts were shorter (P < 0.05), suggesting natural patch foraging behaviour occurs in stabled horses offered multiple concentrate diets even if they vary only in flavour.     

Robustness of Selection Procedures

In the article Bechhofers Indifference-zone formulation for selecting the t populations with the t highest means is considered in a set of non-normal distributions. Selection rules based on the sample mean, the 10% and the 20% trimmed means, two estimators proposed by Tiku (1981) for valuating the smallest and highest accepted sample values higher, the sample median and a linear combination of quantile estimators, two adaptive procedures and a ranksum procedure are investigated in a large scale simulation experiment in respect of their robustness against deviations from an assumed distribution. Robustness is understood as a small percentage of the difference β_A-β between the actual probability of incorrect selection β_A and the nominal β-value. We obtained a relatively good robustness for the classical sample mean selection rule and useful derivations for the employment of other selection rules in an area of practical importance.     

Selection signatures for high-altitude adaptation in ruminants

High-altitude areas are important socio-economical habitats with ruminants serving as a major source of food and commodities for humans. Living at high altitude, however, is extremely challenging, predominantly due to the exposure to hypoxic conditions, but also because of cold temperatures and limited feed for livestock. To survive in high-altitude environments over the long term, ruminants have evolved adaptation strategies, e.g. physiological and morphological modifications, which allow them to cope with these harsh conditions. Identification of such selection signatures in ruminants may contribute to more informed breeding decisions, and thus improved productivity. Moreover, studying the genetic background of altitude adaptation in ruminants provides insights into a common molecular basis across species and thus a better understanding of the physiological basis of this adaptation. In this paper, we review the major effects of high altitude on the mammalian body and highlight some of the most important short-term (coping) and genetically evolved (adaptation) physiological modifications. We then discuss the genetic architecture of altitude adaptation and target genes that show evidence of being under selection based on recent studies in various species, with a focus on ruminants. The yak is presented as an interesting native species that has adapted to the high-altitude regions of Tibet. Finally, we conclude with implications and challenges of selection signature studies on altitude adaptation in general. We found that the number of studies on genetic mechanisms that enable altitude adaptation in ruminants is growing, with a strong focus on identifying selection signatures, and hypothesise that the investigation of genetic data from multiple species and regions will contribute greatly to the understanding of the genetic basis of altitude adaptation.     

Selection of individual tubers in potato breeding

Summary Out of 720 field-grown potato first year seedlings plants with best tuber apearance and large and medium size tubers with best shape were respectively selected. The tuber progeny of each group was evaluated in field experiments. It was demonstrated that the selection of individual tubers was very effective in the elimination of clones with irregular tuber shape and deep eyes. The tuber progeny of selected tubers was not inferior to the tuber progeny of selected plants. Possible applications of the results to practical potato breeding are discussed.     

Selection strategies and artificial evolution

Summary Artificial selection results in biolgical changes, creating artificial evolution. When using selection indexes, the artificial evolution depends on the relative economic (or other) weight of traits in the breeding objective, and on the phenotypic and genetic variances and covariances among these traits and the traits recorded in the selection index. As shown here, the selection strategy (in this case, individual selection versus progeny test selection) can also have marked effects on the kind of artificial evolution produced. Thus, where economic weights are uncertain, choice between alternative selection strategies might take into account the different types of animal or plant resulting.     

Selection indices for non-linear profit functions

Summary Conventional selection index theory assumes that the total merit or profitability of animals is a linear function of measurable traits. However, in many cases merit may be a non-linear function of these traits. A linear selection index can still be used in this situation but the optimum index depends on the selection intensity to be used and on the number of generation over which the selection response is to be maximized. Nonlinear selection indices have been suggested but these result in a lower selection response than the best linear index. Linear selection indices suggested in the past are shown to correspond to the optimum linear index for either a very small selection response or, in the case of restricted indices, a very large selection response. The economic value of a trait may depend on management decisions taken by the farmer. In this situation the economic values should be calculated assuming that the management decisions taken maximize profit given the present genetic value of the animals.     

Selection versus random drift: long-term polymorphism persistence in small populations (evidence and modelling)

Our data on a subterranean mammal, Spalax ehrenbergi, and other evidence, indicate that appreciable polymorphism can be preserved in small isolated populations consisting of several dozens of, or a hundred, individuals. Current theoretical models predict fast gene fixation in small panmictic populations without selection, mutation, or gene inflow. Using simple multilocus models, we demonstrate here that moderate stabilizing selection (with stable or fluctuating optimum) for traits controlled by additive genes could oppose random fixation in such isolates during thousands of generations. We also show that in selection-free models polymorphism persists only for a few hundred generations even under high mutation rates. Our multi-chromosome models challenge the hitchhiking hypothesis of polymorphism maintenance for many neutral loci due to close linkage with few selected loci.     

Studies on Selection of Valuable Somaclonal Mutants in Silage Maize

The calli were induced from young embryo, shoot apex, young leaf, young infiorescences, and hypocotyl of silage maize (Zea mays). The inducing freguency of young embryo was higher than the hypocotyL but the latter was not affected by season changes. The induction of calli were different in response to different kinds and concentration of hormones. Plantlet were regenerated from repetitive subcultured calli, among which three plant lines with characteristics of more tillers and early maturity were selected. Two of the plant lines with characteristics of more tillers and early maturity were selected. Two of the plant lines have become new inbred lines: 8501 and 8502. Through several generations of experimental hybrid combination "Baidan~ 8502" characterized by high silage yield, disease resistant, prolong green period and abundant tillers, has been obtained. The silage yield was 75000~105000 kg/hm2 which accounted for 40% more than the CK variety and commercial varieties.     

Selection for improved yield in inter-specific mixtures or intercrops

Summary A simple recurrent selection scheme using randomly constructed intercrop or mixture treatments for the mutual improvement of two or more species is described. Several possible selection criteria are available for each species, including its own yield, those of each of its associates, and combinations of these. Statistical expressions are developed to describe the expected gain in economic yield in each species given selection for one or more species on the basis of any common criterion, and it is shown that the gains from all responding species and applied selection criteria are additive. Negative correlations between the direct and associate effects of genotypes favour the selection of whole mixtures. Selection indices of several species yields can be applied either on an individual species basis or to whole mixtures, but only in the latter case can the statistics required for the calculation of the optimum index be estimated from the data provided by the trial. Some general properties and possible long term effects of different selection methods are discussed.     

Selection for efficiency of feed utilization in growing mice

Summary Selection was practised for improved feed efficiency (gain/feed intake) of mice on two alternative feeding regimes. In one set of lines animals were fed ad libitum, in the other set they were individually fed a fixed amount of feed (about 10% below the control ad libitum intake) which was not changed over generations. For each treatment, a pair of replicate lines (E) were selected on efficiency from 3–5 weeks of age for 8 generations and another pair (L) from 5–7 weeks for 7 generations. A control line was maintained for both E and L lines. In terminal generations mice from each line were tested on each feeding regime, and carcasses of ad libitum fed mice were analysed.The realized heritability (within families) for efficiency averaged 13%, without much variation over treatments. In the E lines efficiency increased by about 18% of the control mean and in the L lines by about 60%, although absolute changes were small, and responses were similar on the two feeding regimes. Weights at the start of test decreased in the E lines and increased in the L lines; weights at the end of test increased in both.When tested on the alternative regimes, no interactions were detected for live weights, weight gains or efficiency; selection under fixed intake led to the same increase in appetite as did that under ad libitum.There were no interactions for carcass composition. Selection for efficiency led to an increase in fatness on both selection regimes and both weight ranges.     

Subset Selection for Exponential Populations: Determination of the Selection Constant

Given are k(≧2) exponential populations differing only in their location parameter. One wishes to choose the best one, that is the population with the largest value of the location parameter. A possible method for solving this problem is to select a subset of the k populations of size at least one which includes the best population with a required confidence P*(k^?1 ≤ P* ≤1). In this paper the required selection constant is determined for different values of k and P*. Also an approximation for the selection constant is derived. A comparison with the exact results is made.     

Selection for increased length of reproductive life in mice

Summary An experiment was conducted in mice to examine whether selection can increase reproductive life and lifetime production of progeny. Mice in two lines with litter size standardized at birth and in two lines without standardization were pair-mated at 7 weeks of age and maintained as long as they produced litters up to 382 days. Progeny from the sixth litters were used to maintain the four selected lines, while progeny from the first litters were bred to maintain unselected control lines. Selected and control lines were compared at five and six generations of the selected lines. Contemporary comparisons revealed that the length of reproductive life and most lifetime production traits were significantly greater in the selected than in control lines. Realized heritability of the length of reproductive life ranged from 0.08 to 0.13. It was concluded that the length of reproductive life and lifetime production in mice can be increased by selection.Animal Research Centre Publication No. 1618     

Darwinism and Ethology The Role of Natural Selection in Animals and Humans

The role of behaviour in biological evolution is examined within the context of Darwinism. All Darwinian models are based on the distinction of two mechanisms: one that permits faithful transmission of a feature from one generation to another, and another that differentially regulates the degree of this transmission. Behaviour plays a minimal role as an agent of transmission in the greater part of the animal kingdom; by contrast, the forms it may assume strongly influence the mechanisms of selection regulating the different rates of transmission. We consider the decisive feature of the human species to be the existence of a phenotypical system of cultural coding characterized by precision and reliability which are the distinctive features of genetic coding in animals. We examine the consequences for the application of the Darwinian model to human history. This revised version was published online in June 2006 with corrections to the Cover Date.     

Genomic signatures of selection associated with benzimidazole drug treatments in Haemonchus contortus field populations

Genome-wide methods offer a powerful approach to detect signatures of drug selection. However, limited availability of suitable reference genomes and the difficulty of obtaining field populations with well-defined, distinct drug treatment histories mean there is little information on the signatures of selection in parasitic nematodes and on how best to detect them. This study addresses these knowledge gaps by using field populations of Haemonchus contortus with well-defined benzimidazole treatment histories, leveraging a recently completed chromosomal-scale reference genome assembly. We generated a panel of 49,393 genomic markers to genotype 20 individual adult worms from each of four H. contortus populations: two from closed sheep flocks with an approximate 20 year history of frequent benzimidazole treatment, and two populations with a history of little or no treatment. Sampling occurred in the same geographical region to limit genetic differentiation and maximise the detection sensitivity. A clear signature of selection was detected on chromosome I, centred on the isotype-1 β-tubulin gene. Two additional, but weaker, signatures of selection were detected; one near the middle of chromosome I spanning 3.75 Mbp and 259 annotated genes, and one on chromosome II spanning a region of 3.3 Mbp and 206 annotated genes, including the isotype-2 β-tubulin locus. We also assessed how sensitivity was impacted by sequencing depth, worm number, and pooled versus individual worm sequence data. This study provides the first known direct genome-wide evidence for any parasitic nematode, that the isotype-1 β-tubulin gene is quantitatively the single most important benzimidazole resistance locus. It also identified two additional genomic regions that likely contain benzimidazole resistance loci of secondary importance. This study provides an experimental framework to maximise the power of genome-wide approaches to detect signatures of selection driven by anthelmintic drug treatments in field populations of parasitic nematodes.     

Equivalence or Selection: A Distribution-Free Approach

Using a distribution-free approach, a modification of the usual procedure for selecting the better of two treatments is presented. Here the possibility of no selection when the treatments appear to be ‘equivalent’ is allowed. The sample size and the constant needed to implement the proposed procedure are determined by controlling the probabilities of a correct selection and a wrong selection when the two treatments are not equivalent.     

Whole-genome resequencing reveals domestication and signatures of selection in Ujimqin,Sunit, and Wu Ranke Mongolian sheep breeds

ObjectiveThe current study aimed to perform whole-genome resequencing of Chinese indigenous Mongolian sheep breeds including Ujimqin, Sunit, and Wu Ranke sheep breeds (UJMQ, SNT, WRK) and deeply analyze genetic variation, population structure, domestication, and selection for domestication traits among these Mongolian sheep breeds.MethodsBlood samples were collected from a total of 60 individuals comprising 20 WRK, 20 UJMQ, and 20 SNT. For genome sequencing, about 1.5 μg of genomic DNA was used for library construction with an insert size of about 350 bp. Pair-end sequencing were performed on Illumina NovaSeq platform, with the read length of 150 bp at each end. We then investigated the domestication and signatures of selection in these sheep breeds.ResultsAccording to the population and demographic analyses, WRK and SNT populations were very similar, which were different from UJMQ populations. Genome wide association study identified 468 and 779 significant loci from SNT vs UJMQ, and UJMQ vs WRK, respectively. However, only 3 loci were identified from SNT vs WRK. Genomic comparison and selective sweep analysis among these sheep breeds suggested that genes associated with regulation of secretion, metabolic pathways including estrogen metabolism and amino acid metabolism, and neuron development have undergone strong selection during domestication.ConclusionOur findings will facilitate the understanding of Chinese indigenous Mongolian sheep breeds domestication and selection for complex traits and provide a valuable genomic resource for future studies of sheep and other domestic animal breeding.     

无髯鸢尾新品种DUS测试性状筛选

植物新品种特异性、一致性和稳定性(DUS)测试是新品种保护的基础和依据,测试性状的筛选是DUS测试的核心。为制定无髯鸢尾DUS测试指南,初步确定测试性状43个,结合性状间R型聚类分析性状间相关性,去除相关性大、贡献较小的雌蕊长、叶长性状,最终确定操作性强、区别明显的测试性状41个;利用品种间Q型聚类分析确定测试指南的分组性状4个;对性状进行分级及分布分析,保证无髯鸢尾测试指南的可行性,为无髯鸢尾品种测试与授权提供技术支持。     

干热灭菌温度指示剂的筛选和效果验证

利用结晶物质在一定温度下熔融的特性,通过对四种化学试剂进行熔点测定。选出试剂Ａ和试剂Ｂ作为干热灭菌温度指示剂和参考指示剂。试验结果表明,这两种温度指示剂终点明确,简便快速,能满足１８０℃干热灭菌的温度要求,可以对干热灭菌的温度验证提供客观证据     

Selection signatures for fiber production in commercial species: A review

Natural fibers derived from diverse animal species have gained increased attention in recent years due to their favorable environmental effects, long-term sustainability benefits, and remarkable physical and mechanical properties that make them valuable raw materials used for textile and non-textile production. Domestication and selective breeding for the economically significant fiber traits play an imperative role in shaping the genomes and, thus, positively impact the overall productivity of the various fiber-producing species. These selection pressures leave unique footprints on the genome due to alteration in the allelic frequencies at specific loci, characterizing selective sweeps. Recent advances in genomics have enabled the discovery of selection signatures across the genome using a variety of methods. The increased demand for ‘green products’ manufactured from natural fibers necessitates a detailed investigation of the genomes of the various fiber-producing plant and animal species to identify the candidate genes associated with important fiber attributes such as fiber diameter/fineness, color, length, and strength, among others. The objective of this review is to present a comprehensive overview of the concept of selection signature and selective sweeps, discuss the main methods used for its detection, and address the selection signature studies conducted so far in the diverse fiber-producing animal species.