Mechanisms of intake induction of a low-nutritious food in sheep (Ovis aries)

Intake induction refers to the phenomenon by which animals increase consumption of a less-valued meal when followed by a highly-preferred food relative to when followed by no food or by the same less-preferred food. In the Training phase of the present experiment, we assessed the induction effect in sheep using a within-subject design where learning could be tested while controlling for digestive state. Results showed that, once intake reached stability, subjects ate more low-nutritious food (oat hay) when followed than when preceded by a preferred food (soybean meal), supporting the learning hypothesis of induction. The objective of the second, Revaluation, phase of the experiment was to explore the associative mechanism of induction, for which we paired gastrointestinal malaise caused by lithium chloride intoxication with consumption of soybean meal or a control food (wheat bran). Despite subjects partially rejecting soybean meal relative to controls after the aversive conditioning protocol, oat hay consumption seemed unaffected by soybean meal devaluation. We conclude that intake induction in sheep may rely on changes in hedonic properties of the low-nutritious food based on its association with post-ingestive feedback from the preferred food (hedonic hypothesis), but not on an explicit anticipation of the latter (signalling hypothesis).     

Physiological and genetic characteristics of black-boned sheep (Ovis aries)

Here we report for the first time the discovery of sheep that have black bones and black muscles. The spectral pattern of pigment extracted from tissues of these black-boned sheep is similar to that of black-boned Chinese silky fowl. Additionally, black-boned sheep have significantly higher plasma colour, tyrosinase activity and kidney function than normal sheep. Synonymous nucleotide substitutions in the tyrosinase (TYR) and melanocortin 1 receptor (MC1R) genes were detected in black-boned sheep when compared with the corresponding sequences in normal sheep. In addition, a missense mutation (215T>C) in exon 2 of tyrosinase-related protein 1 (TYRP1) was detected in black-boned sheep, and this resulted in a putative valine-to-alanine substitution at codon 68 (Val68Ala).     

A novel maternal lineage revealed in sheep (Ovis aries)

It is generally believed that domestic sheep have two maternal lineages (haplotypes A and B), based on mitochondrial DNA analysis. In the present study, we provide evidence that a novel maternal lineage (haplotype C) is exhibited in Chinese native sheep. To verify this finding, 231 samples were collected from six Chinese local breeds, which cover the vast geographical region of sheep inhabitation in China. For comparison, 50 samples were collected from two Western breeds collected in China. Mitochondrial DNA was screened by PCR single-strand conformational polymorphism (SSCP), leading to the identification of novel band patterns in ND2 and ND4 genes in the Chinese breeds. Interestingly, mutations at the two loci were in strong linkage disequilibrium. Direct sequencing of the DNA fragments revealed a non-synonymous substitution in ND2. Furthermore, two synonymous mutations were identified by comparisons of the novel type (haplotype C) and the established types (haplotypes A and B). The entire mitochondrial control region for 55 samples was then sequenced to construct a phylogenetic tree and median joining network. Both the tree and network demonstrated a topology of three groups, which is in consistent with the SSCP analysis. Unlike Western breeds, Chinese breeds are composed mainly of haplotypes A and B, but with a small fraction of haplotype C. According to Fu's test and mismatch distribution, haplotype C has not been subject to a recent population expansion. Based on these results, we propose a novel origin for Chinese sheep.     

Mitochondrial DNA variation of domestic sheep (Ovis aries) in Kenya

The history of domestic sheep (Ovis aries) in Africa remains largely unknown. After being first introduced from the Near East, sheep gradually spread through the African continent with pastoral societies. The eastern part of Africa was important either for the first diffusion of sheep southward or for putative secondary introductions from the Arabian Peninsula or southern Asia. We analysed mitochondrial DNA control region sequences of 91 domestic sheep from Kenya and found a high diversity of matrilines from the widespread haplogroup B, whereas only a single individual from haplogroup A was detected. Our phylogeography analyses of more than 500 available mitochondrial DNA sequences also identified ancestral haplotypes that were probably first introduced in Africa and are now widely distributed. Moreover, we found no evidence of an admixture between East and West African sheep. The presence of shared haplotypes in eastern and ancient southern African sheep suggests the possible southward movement of sheep along the eastern part of Africa. Finally, we found no evidence of an extensive introduction of sheep from southern Asia into Africa via the Indian Ocean trade. The overall findings on the phylogeography of East African domestic sheep set the grounds for understanding the origin and subsequent movements of sheep in Africa. The richness of maternal lineages in Kenyan breeds is of prime importance for future conservation and breeding programmes.     

Conservation genetics in Chinese sheep: diversity of fourteen indigenous sheep (Ovis aries) using microsatellite markers

The domestic sheep (Ovis aries) has been an economically and culturally important farm animal species since its domestication around the world. A wide array of sheep breeds with abundant phenotypic diversity exists including domestication and selection as well as the indigenous breeds may harbor specific features as a result of adaptation to their environment. The objective of this study was to investigate the population structure of indigenous sheep in a large geographic location of the Chinese mainland. Six microsatellites were genotyped for 611 individuals from 14 populations. The mean number of alleles (±SD) ranged from 7.00 ± 3.69 in Gangba sheep to 10.50 ± 4.23 in Tibetan sheep. The observed heterozygote frequency (±SD) within a population ranged from 0.58 ± 0.03 in Gangba sheep to 0.71 ± 0.03 in Zazakh sheep and Minxian black fur sheep. In addition, there was a low pairwise difference among the Minxian black fur sheep, Mongolian sheep, Gansu alpine merino, and Lanzhou fat‐tailed sheep. Bayesian analysis with the program STRUCTURE showed support for 3 clusters, revealing a vague genetic clustering pattern with geographic location. The results of the current study inferred high genetic diversity within these native sheep in the Chinese mainland.     

Identification of novel genes for bitter taste receptors in sheep (Ovis aries)

Genetic studies on taste sensitivity, and bitter taste receptors (T2R) in particular, are an essential tool to understand ingestive behavior and its relation to variations of nutritional status occurring in ruminants. In the present study, we conducted a data-mining search to identify T2R candidates in sheep by comparison with the described T2R in cattle and using recently available ovine genome. In sheep, we identified eight orthologs of cattle genes: T2R16, T2R10B, T2R12, T2R3, T2R4, T2R67, T2R13 and T2R5. The in silico predicted genes were then confirmed by PCR and DNA sequencing. The sequencing results showed a 99% to 100% similarity with the in silico predicted sequence. Moreover, we address the chromosomal distribution and compare, in homology and phylogenetic terms, the obtained genes with the known T2R in human, mouse, dog, cattle, horse and pig. The eight novel genes identified map either to ovine chromosome 3 or 4. The phylogenetic data suggest a clustering by receptor type rather than by species for some of the receptors. From the species analyzed, we observed a clear proximity between the two ruminant species, sheep and cattle, in contrast with lower similarities obtained for the comparison of sheep with other mammals. Although further studies are needed to identify the complete T2R repertoire in domestic sheep, our data represent a first step for genetic studies on this field.     

An assessment of Walk-over-Weighing to estimate short-term individual forage intake in sheep

The main limitation for determining feed efficiency of freely grazing ruminants is measurement of daily individual feed intake. This paper describes an investigation that assessed a method for estimating intake of forage based on changes in BW of ewes. A total of 24 dry and non-pregnant Romane ewes (12 hoggets, HOG; mean±SD 51.8±2.8 kg BW; body condition score (BCS) 2.6±0.2; and 12 adults, ADU; 60.4±8.5 kg BW; BCS 2.7±0.8) were selected for the study and moved from their rangeland system to a confined pen with controlled conditions and equipped with individual automatic feeders. The experiment lasted for 28 days (21 days adaptation and 7 days feed intake measurement). Ewes were fed hay and trained to use the electronic feeders (one feeding station per ewe) in which actual daily intake (H_intake24) was measured. The pens were designed to maximize movement of trained ewes through an automated Walk-over-Weighing device, by using water and mineral salts as attractants. Total individual intake of hay measured in the automatic feeder at each meal (H_intake) was compared with indirect estimates of feed intake determined using differences in the BW of the ewes (∆BW) before and 1 h following morning and afternoon feeding at fixed times. The BW, BCS, H_intake, H_intake24, as well as plasma non-esterified fatty acids (NEFA), glucose and insulin profiles were determined. The BW was higher in ADU v. HOG but BCS was not affected by parity. The H_intake24 was affected by day of experiment as a consequence of reduced availability and intake of water on one day. Plasma glucose, NEFA and insulin were not affected by parity or day of experiment. The H_Intake was and ∆BW tended to be higher in the morning in HOG, whereas H_intake was and ∆BW tended to be higher in ADU at the afternoon meal. Irrespective of parity or feeding time, there was very strong correlation (r²=0.93) between H_intake and ∆BW. This relationship confirms that our indirect method of estimating individual forage intake was reliable within the strictly controlled conditions of the present experiment. The method appears suitable for use in short-term intensive group feeding situations, and has potential to be further developed for longer-term forage intake studies, with a view to developing a method for freely grazing ruminants.     

Competition between red kangaroos (Macropus rufus) and sheep (Ovis aries) in the arid rangelands of Australia

Abstract Competition between red kangaroos and sheep in the more arid areas of Australia was examined by means of a large-scale manipulative experiment incorporating two replicates of each of three treatments: sheep-only, kangaroo-only and a sheepAangaroo mixture. The study was conducted over two years during which time pasture conditions varied markedly. Competition was intermittent, occurring only during a period of climatically related food depletion (semi-drought). At this time there was a large increase in kangaroo densities due to an influx of kangaroos from neighbouring areas. Competition reduced live-weight in sheep but had no significant impact on wool production. This effect was linked to diet selection. Competition caused red kangaroos to favour paddocks destocked of sheep but had no detectable effect on the condition of kangaroos.     

Maize supplementation of Pelibuey sheep in a silvopastoral system: fodder selection, nutrient intake and resilience against gastrointestinal nematodes

This trial evaluated the effect of maize supplementation on the ingestive behavior, nutrient intake and the resilience against gastrointestinal nematode (GIN) infection of hair sheep in a silvopastoral system containing tropical grasses and legume trees. In addition, it attempted to determine the metabolic cost of the natural GIN infection in supplemented and non-supplemented animals. Twenty-nine 3-month-old lambs (male and female), raised nematode free, were allocated to four groups: I-NS (infected, not supplemented, n = 8), I-S (infected, supplemented with maize at 1.5% live weight (LW), n = 7), T-NS (treated with moxidectin 0.2 mg/kg LW every 28 days, and not supplemented, n = 7) and T-S (treated with moxidectin and supplemented with maize at 1.5% LW, n = 7). During the 70-day trial, fodder intake, fodder selection, LW change (LWC), red blood cell counts (RBC), hemoglobin (Hb), hematocrit (Ht) and eggs per gram of feces (EPG) were measured every 14 days. Supplement consumption was recorded daily. Metabolizable energy (ME) and protein (MP) consumption from the feeds were estimated. Maize supplementation helped to improve the resilience of hair sheep lambs against GIN infections. The I-S and T-NS groups showed similar LWC, RBC, Hb and Ht (P > 0.05) and both were higher than those in the I-NS group (P < 0.05). No difference was found in EPG between the I-NS and the I-S groups (P > 0.05). No effect of sex was observed in the different variables. Although all groups showed low dry matter intake (DMI) (< 2% LW), supplemented groups (T-S and I-S) showed higher total DMI (fodder + maize; P < 0.05), hence higher ME and MP intakes than the non-supplemented groups (T-NS and I-NS). All groups showed similar fodder selection patterns. The estimated metabolic cost of parasitism was ME = 0.70 MJ/day and MP = 9.2 g/day in the I-S animals. Meanwhile, the cost in the I-NS animals was ME = 1.46 MJ/day and MP = 12.71 g/day. Maize supplementation was an economically viable strategy to control GIN compared with no intervention.     

Genetic variability and individual assignment of Chinese indigenous sheep populations (Ovis aries) using microsatellites

The purpose of this study was to assess the genetic characteristics of six breeds of Chinese local sheep using 19 microsatellite loci and to effectively validate statistical methods for individual assignment based on informative microsatellites. All the six breeds deviated from Hardy–Weinberg equilibrium expectations, while the majority of markers complied. The polymorphism information content (PIC) of overall loci for the six populations ranged from 0.283 (SRCRSP5) to 0.852 (OarVH72). Tibetan sheep were the most diverse population with the highest mean allelic richness (6.895), while Ujmuqin (UQ) harboured the lowest allelic richness (6.000). The F‐statistics for the six populations were F_IS = ?0.172, F_IT = ?0.082 and F_ST = 0.077, respectively. Furthermore, the pair‐wise F_IS revealed a moderate genetic differentiation among populations (P < 0.01), indicating that all breeds can be considered genetically independent entities. The lowest genetic differentiation was between Tengchong (TC) and UQ (F_ST = 0.041), and the highest one was between TC and Fat‐tailed Han (F_ST = 0.111). In comparing the three statistical models, we note that the seven microsatellite loci (MAF65, OarJMP58, SRCRSP9, MCM140, OarAE129, BM8125 and SRCRSP5) commonly used for individual assignment will ensure a powerful detection of individual origin, with accuracy up to 91.87%, when the likelihood‐based method is used. Overall, these findings shed light onto the genetic characteristics of Chinese indigenous sheep and offer a set of microsatellite loci that is simple, economic and highly informative for individual assignment of Chinese sheep.     

The dietary overlap between red kangaroos (Macropus rufus) and sheep (Ovis aries) in the arid rangelands of Australia

Abstract The interaction between red kangaroos and sheep in the more arid areas of Australia was examined by means of a large-scale manipulative experiment. The diets of red kangaroos and sheep grazing together and separately in large paddocks were studied to assess whether competition for food might influence diet selection in these species. Diets and the amount of intra- and interspecific dietary overlap varied in accordance with pasture conditions. At pasture biomasses ranging from 50 to 200 g m^?2 (dry weight [wt]), the diets of red kangaroos and sheep overlapped by 58–73%, with forbs and grasses being the major items in the diets of both species. The diets of both sheep and red kangaroos under different experimental regimes were similar. In dry times (pasture biomass 40–50 g m^?2 (dry wt) more shrubs were eaten by both species and the amount of dietary overlap tended to be lower (52–66%). The diets of kangaroos were similar between paddocks. However, in paddocks containing both species sheep consumed proportionately more chenopodaceous shrubs and fewer grasses than those in ‘kangaroo-free’ paddocks.     

Sister chromatid exchange in chromosomes of sheep (Ovis aries)

Blood lymphocyte cultures from 32 Comisana and Laticauda sheep breeds (15 males and 17 females) raised in Southern Italy were studied using sister chromatid exchange (SCE) test. Of the 932 cells studied, the SCE-mean value was 7.20 +/- 2.5 per cell for both breeds. Indeed, the SCE mean values were 7.12 +/- 2.45 and 7.28 +/- 2.55 in Comisana and Laticauda breeds, respectively, and the differences were not significant. No statistical differences were noticed between male and female cells (7.25 +/- 2.39 and 7.16 +/- 2.60, respectively). The SCE frequency distribution did not follow a Poisson distribution. The number of SCE were significantly higher than expected in chromosomes 1, 2 and 3 (p < 0.001) and significantly lower than expected in the X and remaining chromosomes (p < 0.001) on the basis of relative chromosome lengths.     

Genome‐wide association study reveals novel genes for the ear size in sheep (Ovis aries)

Variations in ear size can be observed in livestock such as sheep; however, the genetic basis of variable ear size in sheep is still poorly understood. To investigate causative genes associated with ear size in sheep, a genome‐wide association study was performed in 115 adult Duolang sheep with different‐sized floppy ears using the Ovine Infinium HD BeadChip. We found 38 significant SNPs at the genome‐wide or chromosome‐wise 5% significance level after Bonferroni correction. The most significant association (P = 1.61 × 10^?6) was found at SNP rs402740419, located in the DCC gene, which plays a critical role in ear development. Also, we observed two additional significant SNPs, rs407891215 in PTPRD and rs407769095 in SOX5, both of which are functionally associated with ear developmental processes. Our results are useful for future sheep breeding and provide insights into the genetic basis of ear size development in sheep and other livestock.     

Interspecific transfer of IVM IVF-derived red sheep (Ovis orientalis gmelini ) embryos to domestic sheep (Ovis aries )

Two embryo production methodologies were investigated to generate Red sheep embryos for use in an interspecific embryo transfer program. In Experiment 1, 4 multiparous female Red sheep (Ovis orientalis gmelini ) were implanted with CIDR type G devices for 11 d. Forty-eight hours prior to CIDR removal, a total of 22.5 mg bid of FSH-P was administered over a 3-d period. Laparoscopic embryo collection was performed 5 d post breeding, and embryos were transferred to domestic recipient ewes (Ovis aries and Ovis orientalis musimon ). In Experiment 2, 7 nulliparous female Red sheep were implanted with CIDR devices and injected with 200 IU of PMSG and 25 mg of FSH-P on the 8th day of implant insertion. At 60 to 70 h post PMSG/FSH-P treatment, follicular oocytes were aspirated laparoscopically. The recovered oocytes were matured in M199 (with fetal calf serum, FSH, LH, penicillin and streptomycin) at 39 degrees C in a humidified atmosphere containing 5% CO(2). At 24 h oocytes were fertilized with frozen-thawed semen at a concentration of 1.6 x 10(6) sperm/ml. The ova/embryos were placed in CR2 or BOEC culture medium at 20-22 h post IVF. Following 3 to 4 d in culture, embryos were transferred laparoscopically to the uterine horn of synchronized recipients. In Experiment 1, 4 embryos and 6 UFO were collected from 2 embryo donors, respectively. Two embryos were transferred with the aid of a laparoscope to each of 2 Rambouillet recipients, one of which gave birth to a healthy Red sheep lamb at 158 d of gestation. In Experiment2, a total of 62 oocytes was collected from 7 oocyte donors; 16 developed to the 16- to 32-cell stage and were transferred to 8 recipients. Three of these IVM-IVF embryos were transferred laparoscopically to 2 Mouflon recipients, resulting in no pregnancies. Thirteen IVM-IVF embryos were transferred to 6 Rambouillet recipients. Each of these gave birth to a single healthy Red sheep lamb. Gestation lengths of the 3 IVM-IVF lambs ranged from 152 to 162 d. This research demonstrates that when using compatible species IVM-IVF technology in conjunction with interspecific ET can lead to the production of live offspring and can be used to propagate exotic ovine species.     

Quantitative trait loci (QTL) mapping of resistance to strongyles and coccidia in the free-living Soay sheep (Ovis aries)

A genome-wide scan was performed to detect quantitative trait loci (QTL) for resistance to gastrointestinal parasites and ectoparasitic keds segregating in the free-living Soay sheep population on St. Kilda (UK). The mapping panel consisted of a single pedigree of 882 individuals of which 588 were genotyped. The Soay linkage map used for the scans comprised 251 markers covering the whole genome at average spacing of 15cM. The traits here investigated were the strongyle faecal egg count (FEC), the coccidia faecal oocyst count (FOC) and a count of keds (Melophagus ovinus). QTL mapping was performed by means of variance component analysis so that the genetic parameters of the study traits were also estimated and compared with previous studies in Soay and domestic sheep. Strongyle FEC and coccidia FOC showed moderate heritability (h(2)=0.26 and 0.22, respectively) in lambs but low heritability in adults (h(2)<0.10). Ked count appeared to have very low h(2) in both lambs and adults. Genome scans were performed for the traits with moderate heritability and two genomic regions reached the level of suggestive linkage for coccidia FOC in lambs (logarithm of the odds=2.68 and 2.21 on chromosomes 3 and X, respectively). We believe this is the first study to report a QTL search for parasite resistance in a free-living animal population and therefore may represent a useful reference for similar studies aimed at understanding the genetics of host-parasite co-evolution in the wild.     

Sex differences in relationships between habitat use and reproductive performance in Soay sheep (Ovis aries)

The role of habitat use in generating individual variation in fitness has rarely been examined empirically in natural populations of long‐lived mammals, particularly for both sexes simultaneously. This is the case despite the increase in studies attempting to understand evolutionary change in such populations. Using data from the St. Kilda Soay sheep population, we quantified the association between lifetime reproductive performance (lifetime breeding and reproductive success) and the proportion of the home range covered by a key grass species, H. lanatus, for 490 females and 304 males. Increased H. lanatus cover was associated only with increased female lifetime reproductive success, but increased lifetime breeding success for both sexes, arising through increased male longevity and increased female fecundity. This work suggests that improved understanding of the causes and consequences of fitness differences will likely require us to better account for habitat‐derived individual variation, and to do so for the sexes appropriately.