Genetic improvement of reproductive efficiency of sheep and goats

Sheep and goats are produced in a wide range of production systems and climatic conditions and possess great genetic diversity in reproductive potentials. Mean litter sizes range from near 1 to 3 or more, and patterns of seasonal reproduction are often strongly synchronised to local conditions. Thus, optimisation, rather than maximisation, of reproductive potentials is required, and optimum reproductive rates are often well below those which could be achieved. However, changing employment patterns, increasing urbanisation, and emergence of new markets provide corresponding opportunities for sustainable intensification of small ruminant production, potentially requiring enhancements in reproductive potentials. Heritabilities for most reproductive traits are less than those for many other traits, usually ranging from 0.05 to 0.15, and opportunities for within-breed selection are therefore limited. Substantial changes in litter size or major changes in seasonal breeding patterns are thus best achieved by crossing of divergent breeds to rapidly reset genetic potentials for these traits, followed by within-breed selection to optimise reproductive potentials. Various mutations influencing ovulation rate and litter size in sheep provide additional opportunities to rapidly adjust genetic potentials, but require careful breeding management. Comparable major genes have not yet been found in goats or for traits associated with breeding season.     

Livestock production in central Mali: Reproductive performance and reproductive wastage in ruminants in the agro-pastoral system

Results of a 7-yr field study and a 3-yr slaughterhouse study into reproductive performance and reproductive wastage of ruminants in central Mali are reported. Cattle had delayed age at first puberty (40), long calving intervals (644) and produced few young (3.02) per lifetime. Goats and sheep first conceived at about 11 mo, had shorter parturition intervals (298 and 280 d) but also produced few young (2.64 and 1.92) per lifetime. Conceptions showed a strong seasonality in cattle and mainly occurred during and shortly after the short rainy season. Seasonality was less marked in small ruminants, but most females conceived before the rains. However, maximum litter sizes were associated with late-rain and post-rain conceptions. Early embryonic wastage did not appear to be a major problem but abortions, stillbirths and heavy preweaning mortality were sources of loss of reproductive potential. Additionally at a secondary (government controlled) abattoir, 15.0 % of cows, 31.7 % of goats and 20.0 % of sheep that were slaughtered were found to be pregnant.     

Chorioptic Mange (Acarina: Psoroptidae) in Domestic and Wild Ruminants in Israel

In a 20-year-survey, 9364 dairy cattle in 324 herds kept under a zero-grazing management, 1252 beef cattle in 46 herds grazing all the year round, 3347 sheep in 134 herds (only 26 are grazing herds), and 872 goats in 47 herds (only 20 are grazing) were examined. The mites collected from cattle were identified as Chorioptes texanus only, and those from sheep, goats and gazelles were identified as C. bovis. Chorioptic mange was not diagnozed in grazing beef cattle, ibexes and housed animals (as compared to grazing herds), and in rams and billy goats. Holstein-Israeli bulls kept in insemination centres were not clinically infested, whereas four Charolais bulls were infested with chorioptic mange. Infestation rate was higher in older animals than in younger ones. Hoggets and young goats over 10 months and heifers over 13 months were found clinically infested with Choriopic mites. Lesions were not usually extensive and occurred mainly in predilection sites. The ocular form in sheep and the groin form in goats are very uncommon and apparently are reported for the first time. Chorioptic mange was recorded generally throughout the year. In our study seasonal distribution could not be demonstrated in cattle, while in sheep and goats the highest infestation rate occurred in February to March and the lowest in August and September.     

Toxoplasma gondii infection in meat-producing small ruminants: Meat juice serology and genotyping

The consumption of ovine and caprine meat is considered one of the major transmission routes for Toxoplasma gondii infection in humans. The present study aimed at obtaining epidemiological and molecular data on T. gondii infection in small ruminants slaughtered or commercialized in Italy. Meat juices from 227 sheep and 51 goats were analyzed with a commercial ELISA and antibodies were detected in 28.6% sheep and 27.5% goats. A significant difference was highlighted between adult sheep and the other considered categories (young sheep, young and adult goats) concerning the detection of antibodies (94.1%; p-value = .008). Muscles of positives samples were submitted to molecular analysis, and T. gondii DNA was detected in 15 sheep and three goats; sequencing of B1 gene showed that all belonged to Type II. The present study confirmed small ruminants' meat as a possible source of T. gondii infection for consumers eating raw or undercooked meat, particularly in those countries where the consumption of sheep and goats' meat products is a traditional gastronomic habit.     

Reproductive capacity and dominant lethal mutations in female guinea-pigs and Djungarian hamsters following X-rays or chemical mutagens.

The reproductive capacity and induction of dominant lethal mutations in adult female guinea-pigs and Djungarian hamsters were tested following treatment with 400 rad X-rays, 1.6 mg/kg triethylenemelamine (TEM) or 75 mg/kg isopropylmethanesulphonate (IPMS). A fairly high level of dominant lethals were observed in female guinea-pigs mated at the first oestrus after irradiation (23.4 +/- 6.4%) with a lower yield at 3 months (9.6 +/- 8.2%). Neither of the chemicals caused any significant induction of dominant lethals at either mating time. In the reproductive capacity experiments, the mean litter size of irradiated female guinea-pigs was reduced for about 12 months and this was especially marked in the first 6 months following treatment. Neither of the chemicals caused any significant differences in early litter sizes but there was a noticeable reduction in the litter sizes of TEM-treated females in the 18--24 month interval. With Djungarian hamsters a marked effect of X-rays on reproductive capacity was apparent. After 400 rad a smaller proportion of irradiated females littered in the first 25-day interval than after the other treatments, and no irradiated females produced more than one litter. Neither of the chemicals caused such a drastic reduction in fertility but TEM-treated females produced fewer litters and became sterile at an earlier age than control or IPMS-treated females. With IPMS, the number of litters produced was similar to the controls. Both chemicals caused a significant reduction in litter-size but further work is needed to establish whether this was due to induction of dominant lethals. No translocations were observed in the sons of treated female guinea-pigs or hamsters, but the numbers of animals studied were too small for any conclusions to be drawn.     

The establishment and reversibility of species affinities in domestic sheep and goats

The establishment and reversibility of cross-species attachments were studied in sheep and goats taken from their mothers at birth and reared in same- or cross-species pairs until 12 months of age. Species affinities were determined at eight to nine months of age by time spent proximate to stimulus herds of sheep and goats housed in separate enclosures within a larger pasture. Sheep reared with goats spent significantly more time with the stimulus goats than did controls (sheep reared with sheep). Likewise, goats reared with sheep spent a significantly greater percentage of time with the stimulus sheep than did control goats. At approximately 13 months of age the sheep were segregated from the goats in separate pastures and were retested, as before, for species affinities after 34 to 90 days of exposure to conspecifics. Experimental subjects demonstrated a significant reversal of species preferences. However, the reversal was more complete for subjects housed for 57 to 90 days in same-species groups than for those tested after 34 to 56 days of exposure to conspecifics. It was concluded that species affinities of sheep and goats are basically learned and that relatively long-standing cross-species social attachments can be reversed by approximately 60 to 90 days of same-species cohabitation.     

Preferences for sheep or goats in Indonesia

This paper aims to explore farmers’ preferences for sheep or goats based on feeding practices, animal and flock performances and economic benefits of sheep and goats in different agro-ecological zones in Central Java, Indonesia. In total, 150 smallholder farmers were selected from three agro-ecological zones: the lowlands, the middle zone, and the uplands. Feeding and performance parameters were estimated through weekly farm visits and farm records, from September 2001 to August 2003. In the lowlands, small ruminants were fed mainly with field grass and crop residues, whereas in the middle zone and uplands feeds fed were mainly field grass and leaves. Sheep were given more opportunities to graze than goats, however, grazing was not a major component in the diets. In the lowlands and the middle zone the differences in feed intakes, ADG and reproductive performances between sheep and goats were small. In all zones, does had significantly larger litters than ewes. In the uplands, goats had a significantly higher DMI, grew slightly faster, and had a higher weaning rate than sheep. Consequently, in the uplands, the total economic benefits from goat flocks were 25% higher than from sheep flocks. The major differences in agro-ecological conditions that affect the choice for sheep or goats were the availability of cassava peels in the lowlands, favouring a choice for sheep, and the abundance of leaves in the middle zone and uplands, which favours keeping goats. The promotion of goats by the government, the family tradition of keeping sheep or goats, the preference for sacrificing sheep for religious festivities, and the high initial investment needed to buy goat breeding stock could be other important motives to keep sheep or goats. Sheep fattening based on rice bran supplementation could be a feasible innovation in the lowlands. In the middle zone and uplands goat breeding could make a positive contribution to rural livelihoods.     

Orthoptera as ecological indicators for succession in steppe grassland

Understanding the effects of land-use on threatened ecosystems is of special relevance for nature conservation. The aim of our study was to use Orthoptera as ecological indicators for succession in Central European steppe grasslands.Orthoptera showed a clear response to succession. Each successional stage harboured a unique assemblage. Species richness of habitat specialists was highest in the earliest seral stages. In contrast, density of all species peaked at the intermediate successional stage. Early successional stages are mostly likely to be preferred by specialized Orthoptera because they provide warm suitable oviposition sites (bare ground) and microclimatic conditions. The density peak in the mid-successional stage probably reflects a trade-off between favourable ambient temperatures for optimal development, sufficient food and shelter against predators.Although all successional stages of steppe grassland are relevant for conservation, early and mid-successional stages are the most important. Consequently, conservation management should aim at re-introduction of a traditional, low-intensive land use for abandoned steppe grasslands. As an optimal land use, we recommend traditional rough grazing with sheep and goats, which creates a heterogeneous habitat structure with bare ground, and avoids the accumulation of litter, favouring Orthoptera.     

Individual variation in reproductive costs of reproduction: high-quality females always do better

1. Although life-history theory predicts substantial costs of reproduction, individuals often show positive correlations among life-history traits, rather than trade-offs. The apparent absence of reproductive costs may result from heterogeneity in individual quality. 2. Using detailed longitudinal data from three contrasted ungulate populations (mountain goats, Oreamnos americanus; bighorn sheep, Ovis canadensis; and roe deer, Capreolus capreolus), we assessed how individual quality affects the probability of detecting a cost of current reproduction on future reproduction for females. We used a composite measure of individual quality based on variations in longevity (all species), success in the last breeding opportunity before death (goats and sheep), adult mass (all species), and social rank (goats only). 3. In all species, high-quality females consistently had a higher probability of reproduction, irrespective of previous reproductive status. In mountain goats, we detected a cost of reproduction only after accounting for differences in individual quality. Only low-quality female goats were less likely to reproduce following years of breeding than of nonbreeding. Offspring survival was lower in bighorn ewes following years of successful breeding than after years when no lamb was produced, but only for low-quality females, suggesting that a cost of reproduction only occurred for low-quality females. 4. Because costs of reproduction differ among females, studies of life-history evolution must account for heterogeneity in individual quality.     

绵羊产羔性状主效基因检测研究

以绵羊BMP15基因和BMPR-IB基因为候选基因,以湖羊、中国美利奴单胎品系、中国美利奴肉用和毛用多胎品系为研究对象,采用PCR-RFLP方法对候选基因进行单核苷酸多态性（SNP）位点检测和基因型分析,同时研究基因对绵羊产羔数的影响。对BMP15基因进行SNP检测,结果未发现多态性位点;对BMPR-IB基因进行多态性检测,结果发现了一个A746 G SNP位点。依据A746 G SNP位点进行基因型分析,结果在各品种（系）羊中发现了3种基因型,即BB、B+和++。等位基因型频率在各品种（系）间差异极显著（P<0.001）,在湖羊中以BB基因型为主,在中国美利奴单胎品系中以++基因型为主, 而在中国美利奴肉用和毛用多胎品系中以B+基因型为主。BMPR-IB A746G位点的变异明显影响绵羊的产羔数,与++基因型母羊相比, BB和B+基因型母羊产羔数明显较多。研究结果同时表明,利用BMPR-IB基因型可以很好的预测母羊的产羔数。研究获得的这些结果强烈表明BMPR-IB为影响绵羊的产羔数的主效基因,可以用于对绵羊产羔数的选择。Abstract: The current study was designed to detect SNPs within BMP15 and BMPR-IB gene and investigate the effect of the genes on sheep litter size. Four sheep lines, HU-Yang, Chinese M erino monotocous, Chinese Merino multiparous for wool production and Chinese Merino multiparous for mutton production, were used in this study. Litter sizes were recorded for each ewe in the four lines. Primers for BMP15 and BMPR-IB gene were designed from database sheep sequence and polymorphisms were detected by PCR-RFLP method. The results showed that there was no polymorphism with BMP15 gene among the four lines, and there was an A / G SNP with BMPR-IB gene at base 746 among the four lines. Three types of genotype (BB, B+ and ++), based on A / G locus, were found within each line. The frequencies of genotypes were significantly different among the lines (P<0.001), with BB genotype primarily existing in HU-Yang, ++ genotype in Chinese Merino monotocous line, and B+ genotype in Chinnese Merino multiparous lines. The A / G mutation influence significantly the sheep litter sizes, and the BB and B+ ewes had significant higher litter sizes than ++ ewes. The results of present study showed simultaneously that the genotype of BMPR-IB was a perfect predictor of the sheep litter sizes. These results intensively indicated that BMPR-IB is a major gene to affect litter size in sheep, and could be used as the molecular genetic marker to select litter size in sheep.     

Hemoglobin function in the developing goat and sheep

Comparative studies of the blood of newly born goats and sheep have indicated a number of mechanisms which are responsible for a decreasing affinity for molecular oxygen in these developing animals during the first 40 to 60 days after birth.
The concentration of 2,3-DPG in the red cells of young goats increases four to sixfold during the first 3 to 4 days of life, and this increase is associated with a marked decrease in the cellular pH; 2,3-DPG does not bind to hemoglobins of goats and the decreased affinity for oxygen of goat blood at this period is apparently due to the lowered pH produced by the large increase of intracellular anions. Similar changes occur in young lambs.
After 15 to 20 days the changes of the dissociation curve are related more to structural differences between adult and fetal hemoglobins; cellular pH moves closer to the values of adult red cells. In goats of this age the predominate hemoglobins are those with β chains and these have dissociation curves shifted further to the right than other adult hemoglobins.
In young lambs Hb-C is found only in association with Hb-A but the amount present seldom exceeds 5 to 10%. The oxygen affinities of sheep Hb-A and Hb-C are identical but higher than that of sheep Hb-B.     

Developmental and hair-coat determinants of grooming behaviour in goats and sheep

Self-grooming is a common behaviour among many species of ungulates, as it is among several other mammalian taxonomic groups. In goats, as in rodents and small felids, self-grooming appears to reflect an underlying endogenous timing mechanism, resulting in what has been referred to as programmed grooming. We tested the prediction from the programmed grooming model that newborn and young goats, Capra hircus, would groom more frequently than similarly maintained conspecific adults. This prediction was upheld in that goat kids, from 2 weeks of age, orally groomed and scratch-groomed significantly more frequently than adult females. When the body surface-to-mass ratio of young goats, which was initially about 230% that of adults, declined to about 150%, the difference in grooming rate of the young was no longer significantly elevated over that of adults recorded at the same time of year. We also tested the predictions that oral grooming in wool sheep, Ovis aries, is inherently programmed and will occur in adults after shearing and in lambs with undeveloped fleece at levels similar to those of ancestral hair sheep and lambs. When fully fleeced adult wool sheep were shorn, they engaged in grooming in a pattern and frequency not different from that of hair sheep with a pelage representative of ancestral sheep. Wool lambs also groomed at a rate similar to that of hair lambs. Therefore, the elevated rate of programmed grooming of newborn and young ungulates appears to reflect their developmental precociousness and consequent exposure, in nature, to ectoparasites.     

Reconstructing Anthropogenic Disturbance Regimes in Forest Ecosystems: A Case Study from the Swiss Rhone Valley

Anthropogenic disturbances of forest ecosystems are increasingly recognized as fundamental ecological processes with important long-term implications for biogeochemical cycles and vegetation patterns. This article aims at reconstructing the extent and intensity of the two most common types of traditional forest uses—forest litter collecting and wood pasture—in the Swiss Rhone valley (Valais) by (i) identifying the spatiotemporal patterns, and (ii) modeling the biomass removal through these practices. Detailed information on agricultural practices and socio-economic context were essential to develop reliable estimates of anthropogenic disturbance regimes. In the Valais, predominately goats and sheep grazed in the forests. The intensity of grazing was a function of the number of grazing animals and the available grazing area. Forest litter was used as bedding for farm animals during the winter. Key factors determining the intensity of litter collecting were the number of animal units, the amount of available substitute products (straw), and the area where litter raking could be practiced. The results show that wood pasture and forest litter collecting were practiced on a significant proportion of the forested landscape in the Valais up to the second half of the 20th century. Until the implementation of forest management plans in the 1930s, almost half of the forests in the study area were affected by wood pasture and/or forest litter collecting. The regulations in the management plans led to an essential reduction of the area available for these traditional practices but likewise to an increased pressure on the remaining areas. The results suggest that the notion of a slow but steady disappearance of traditional non-timber forest uses and the associated effects on forest ecosystems is oversimplified. Quantitative reconstructions of biomass output resulting from these practices confirm the importance of traditional non-timber forest uses for ecosystem development in this region. Furthermore, it is very likely that similar effects have been widespread throughout regions with similar natural and socio-economic context, for example, throughout a significant proportion of the European Alps. This study underlines the importance of environmental history for ecological sciences as well as for forest management and conservation planning.     

Initiation of the breeding season in ewe lambs and goat kids with melatonin implants

Sixty-eight female and 4 male lambs of the Chios breed born in autumn (September–October) and 48 female and 4 male kids of the Damascus breed also born in autumn (November), were used to evaluate the effect of melatonin implants (Regulin^®) on the initiation of the breeding season. For each species and sex, half of the animals were either left untreated to serve as controls (C) or received ear implants (females one and males two implants) of melatonin (MEL) in May (spring). Each C and MEL group of females was kept separately and away from males for 5 weeks after implantation and then, C and MEL males were joined with the respective groups for 45 (sheep) and 35 days (goats). Animals not conceiving during the early June–July breeding season, were mated again in September (natural breeding season). The reproductive performance and the 60-day milk yield of animals giving birth during the two seasons were compared. Early in the season (mid November–December), significantly more MEL than C ewes and goats gave birth (75.5% versus 23.5%, p < 0.01; 70.8% versus 37.5%, p < 0.05, respectively). For both species, most of the other characteristics examined were significantly affected by season, but not by treatment. Females giving birth early in the season were approximately 80 days younger at parturition and recorded a lower body weight at mating than those giving birth in the natural February–March season. In the first mating period, the animals mated and conceived had similar body weights to those not mated. The natural, compared with the early June–July mating season, was associated in sheep with higher litter weight at birth (7.0 kg versus 5.8 kg, p < 0.05) and in sheep and goats with a higher number (p < 0.05) of offspring born live (1.78 versus 1.38; 2.0 versus 1.61, respectively) and weaned (1.74 versus 1.36; 1.82 versus 1.35, respectively). Total litter size at birth and 60-day milk yield after weaning, were not significantly different between the two seasons. It could be concluded that melatonin implants administered during the last month of spring in autumn-born female Chios sheep and Damascus goats, advanced the initiation of their breeding season by about 80 days when joined with young males also treated with melatonin implants. The overall reproductive performance and milk yield of animals breeding early, was satisfactory and comparable to that of animals breeding in the natural breeding season.     

Are cattle,sheep, and goats endangered species?

For about 10 000 years, farmers have been managing cattle, sheep, and goats in a sustainable way, leading to animals that are well adapted to the local conditions. About 200 years ago, the situation started to change dramatically, with the rise of the concept of breed. All animals from the same breed began to be selected for the same phenotypic characteristics, and reproduction among breeds was seriously reduced. This corresponded to a strong fragmentation of the initial populations. A few decades ago, the selection pressures were increased again in order to further improve productivity, without enough emphasis on the preservation of the overall genetic diversity. The efficiency of modern selection methods successfully increased the production, but with a dramatic loss of genetic variability. Many industrial breeds now suffer from inbreeding, with effective population sizes falling below 50. With the development of these industrial breeds came economic pressure on farmers to abandon their traditional breeds, and many of these have recently become extinct as a result. This means that genetic resources in cattle, sheep, and goats are highly endangered, particularly in developed countries. It is therefore important to take measures that promote a sustainable management of these genetic resources; first, by in situ preservation of endangered breeds; second, by using selection programmes to restore the genetic diversity of industrial breeds; and finally, by protecting the wild relatives that might provide useful genetic resources.     

PROXIMATE AND ULTIMATE CONTROLS ON LIFE-HISTORY VARIATION: THE EVOLUTION OF LITTER SIZE IN WHITE-FOOTED MICE (PEROMYSCUS LEUCOPUS)

Recruitment of litter-mates of nest-box-inhabiting white-footed mice was monitored to study the evolution of litter size. The frequency distribution of litter sizes was nonsymmetrical, and the most frequent litter size was less than the optimum. This was not the result of differential parental survival, which was independent of litter size produced. Recruitment remained constant or increased slightly to a peak in litters of five young, and then dropped precipitously for larger litters. The single optimum litter size of five did not appear to have any physiological correlates. Instead, the equally low probability of successful recruitment of any young from any given litter may have given rise to a bet-hedging strategy of frequent iterated reproductions. A theoretical analysis of optimal parental investment in offspring was initiated under the assumption that optimal brood size represents a maximization of differences between age-specific costs and benefits of reproduction, both of which should be measured in constant currency of inclusive fitness. In the past, benefit has been measured by current fecundity, and cost by residual reproductive value. However, reproductive value is an appropriate estimate of inclusive fitness only for organisms in which parental investment has little effect on the subsequent survival of offspring to reproductive age. Reproductive value weighted by offspring survival and devalued by the degree of genetic relatedness defines a new currency, replacement value, which is more appropriate for evaluating the costs and benefits of parent-offspring conflict over parental investment in current as opposed to future young. Total parent-offspring conflict intensifies with increases in current brood size. For species with severe reproductive constraints, such as post-partum estrus in white-footed mice, such conflict may force parents to curtail investment in current offspring at or near parturition of subsequent litters, even if that means reducing the survival of current young.     

Litter sizes of Ha(ICR) mice: a preference for even numbers?

The frequency distributions of litter sizes at birth for eight sublines derived from the same Ha(ICR) mouse stock with or without selection for large litters have their modes at even numbers of young. Each of the eight sublines produced a majority of even-numbered litters. An upward integral shift relationship among the medians of the frequency distributions was established. These findings are interpreted to mean that, in response to continued plus selection, ovarian and uterine performance of the Ha(ICR) bipartite reproductive system tends to be maximal bilaterally, which results in an excess of even-numbered litter sizes.     

川西平原大足鼠的种群生态学 III.繁殖

在川西平原利用标志重捕、夹捕解剖和半自然条件下笼养的方法,提供了1989～1995年大足鼠种群雄性和雌性个体处于繁殖状态的比例、胎次数、每胎幼仔数、幼年个体的补充和发育等有关繁殖的基本资料。结果显示,大足鼠极灵活的繁殖策略 提高了这个物种幼年个体的存活,使该物种在可预见而频繁的周期性变化的农田环 境中能够保持相对稳定的种群。大足鼠的繁殖特征主要有：处于繁殖状态的雄性比例较大（平均0.491,95%置信区间0.451和0.534）,怀孕雌性的比例较小（平均0.227,95％置信区间0.213和0.301）,较高和相对稳定的繁殖能力（每年4胎,每胎8.245±0.452只）,雌性幼仔较慢的生长和性成熟（4月）,以及幼年个体加入种群与春季的小麦和秋季的水稻成熟相同步。这些繁殖特征使得大足鼠的繁殖活动集中在有利的时间。结果,虽然伴随繁殖活动雌雄性的个体质量下降,但仍能在短暂的时间里恢复到原来的水平。将大足鼠的胎仔数与一些关于中国啮齿动物繁殖参数地理变异 的研究进行了分析比较,发现后者提供的资料尚不足以支持中国所有啮齿动物都有 "胎仔数随纬度增加"的过分简单的一般结论。每一个物种种群都有自己的最优胎 仔数,但最优胎仔数不一定随纬度而增加。我们认为在大尺度上研究如胎仔数这样的生活史性状时,生活史多样性的提法比单一性状的过分简单的一般化更好。     

The intake and digestion of a range of temperate forages by sheep and fibre-producing goats

The voluntary intake, digestibility and mean retention time of six temperate forages differing in their chemical composition by 12 adult castrated male Scottish blackface sheep, aged 15 months, and fibre-producing castrated male goats, aged 27 months, and of similar live weight, 40 kg, were described. The creation of a range of chemical compositions was effected through the use of barley straw, and a low- and high-digestibility hay, and the use of ammonia treatment of these forages. A wide range of voluntary intakes (42–78 g DM/kg W^0.75/day), digestibility of dry matter (0.46–0.60) and mean retention times of undigested residues (36–72 h) was achieved through feeding the six forages. Across all the forages fibre-producing goats had higher voluntary intakes, expressed on a metabolic live weight basis, and lower digestibility values than sheep, whereas the mean retention time of the undigested residues was similar for the two species. Within forages goats selected a diet of potentially higher nutritive value, as predicted from chemical composition, with a smaller particle size than sheep. It was concluded that the differences in intake and digestion of temperate forages between sheep and fibre-producing goats are broadly similar to those observed in other experiments between sheep and goats ingesting tropical forages.     

Polymorphism of FecB gene in nine sheep breeds or strains and its effects on litter size, lamb growth and development

Nine sheep breeds or strains, including 615 individuals were screened with forced PCR RFLP method for the FecB gene to study the polymorphism and its effects on litter sizes, body weights and body sizes. Results show that the polymorphism frequencies of FecB gene are significantly imbalanced in these breeds or strains. The Hu sheep were all homozygous carriers (BB). In the Chinese Merino prolific meat strain, the genotype frequencies of BB, B+ and ++ are 51%, 30% and 19%, respectively, whereas all the other flocks had only the wild-type (++) genotype. Results within Chinese Merino prolific meat strain showed that mean litter sizes of ewes with genotype BB and B+ are 2.8 (+/-0.74) and 2.3 (+/-0.63) (P > 0.05), whereas ++ ewes had a litter size of only 1.2 (+/-0.68) (P < 0.01). At 90 days after birth, the body weights of BB/B+ lambs were higher than that of ++ lambs (18.6 +/- 3.70 kg, 18.0 +/- 3.71 kg versus 15.6 +/- 2.22 kg, P < 0.05). In addition, the heart girth and chest width of BB/B+ lambs were significantly longer than ++ lambs (P < 0.05). No significant differences were observed in either body weight or body size at day 120. Litter size at first lambing from Hu at Natural Source Conservative Region was found to be significantly higher than that from the other two regions sampled (P < 0.05). In addition to the additive effect on litter size, these findings show for the first time that the FecB gene had a positive effect on early postnatal body growth.