Naturally-derived genetic mutations affecting ovulation-rate are referred to as fecundity genes, since the most noticeable effect is on the number of offspring produced. Mechanisms by which mammals (notably sheep) with altered ovulation-rates achieve these effects are not due solely to the actions of the pituitary gland on the ovary as the ovary itself contributes significantly to this outcome. Currently, 16 different mutations in six genes have been identified in sheep that influence ovulation rate. At least 13 mutations in four different genes are expressed in the oocyte indicating that the oocyte has a profound influence on ovulation-rate.

This study was conducted to investigate the effect of attaining puberty in the first year of life on future reproductive performance in ewes. Records were collected from 2091 ewes born between 2005 and 2009. In the first breeding season of life, receptivity to the ram was monitored to determine whether ewe lambs attained puberty or not. Ewes were then mated in order to produce a lamb at 2, 3 and 4 years of age and the following traits were measured each year: ovulation rate (OR), number of foetuses present at scanning (NLS), number of lambs born (NLB) and live weight at various time points. The percentage of ewe lambs attaining puberty was highly variable between years (p < 0.001) and this variability was not explained by differences in live weight. Attainment of puberty in the first year of life increased NLB at 2 years of age (p < 0.001), largely due to an increase in OR (p < 0.01). Ewes that attained puberty in their first year were more likely to become pregnant at 2 years of age (p < 0.01) and produced more multiple births and fever singletons (p < 0.05). These differences were not maintained at 3 and 4 years of age although differences in live weight remained (p < 0.001). These results demonstrate that attaining puberty in the first year of life improves reproductive performance as a 2 year old, increasing NLB by 20 lambs per hundred ewes and reducing the incidence of non-pregnant ewes. This has implications for improving the efficiency of sheep production on-farm. (C) 2014 Elsevier B.V. All rights reserved.

Partial neutralization of bone morphogenetic protein 15 (BMP15) bioactivity by immunization is known to increase ovulation rate in sheep. However, it remains uncertain whether BMP15 vaccination would be a suitable procedure for increasing lambing rate. The aim of this study was to compare the efficacy of a BMP15 vaccination treatment on lamb production to that of commercially-available androstenedione-based vaccines that are used for this purpose. Ewes were immunized for 3 yr against androstenedione, BMP15, or no antigen (control). Vaccination with androstenedione or BMP15 altered (P < 0.05) ovulation rate as well as litter size at midpregnancy, birth, and weaning compared with controls. No differences were detected in the proportions of ewes conceiving in the first cycle or partial failure of multiple ovulations. Both gender and litter size affected birth weight of the lamb (P < 0.05), but no effect of treatment was found. Growth rate was significantly affected (P < 0.05) by gender, birth weight, and the number of lambs raised, but not treatment. In conclusion, immunization against either androstenedione or BMP15 increased ovulation rate. Androstenedione vaccination also increased the number of lambs weaned (P < 0.05). Bone morphogenetic protein 15 vaccination altered the pattern of the number of lambs weaned, but no increase in lamb production was observed as more ewes produced zero or three lambs. Overall, androstenedione or BMP15 vaccination did not significantly affect embryo or fetal survival or lamb performance independently of the effects of these treatments on ovulation rate.

This study aimed to determine whether ewes heterozygous (I+) for the Inverdale mutation of the bone morphogenetic protein-15 (BMP15) gene with high natural ovulation rate (OR) show similar sensitivity to nutritional manipulation as non-carriers (++). Increasing pre-mating nutrition results in OR increases in sheep, but whether this effect occurs in ewes with naturally high OR is unknown. Over 2 years, I+ or ++ ewes were given high (ad libitum) or control (maintenance) pasture allowances for 6 weeks prior to mating at a synchronised oestrus, with OR measured 8 days later. The high group increased in weight compared with controls (+5.84kg; P<0.01), accompanied by increased OR (+19%; P<0.01). As well as having higher OR (+45%; P<0.01), I+ ewes responded to increased feed with a larger proportional increase in OR (+27%; P<0.01) compared with the response in ++ ewes (+11%; P<0.05), suggesting an interaction between BMP15 levels and nutritional signals in the follicle to control OR. Although litter size increases only tended to significance (+12%; P=0.06), extra feed resulted in over 50% of I+ ewes giving birth to more than three lambs, compared with 20-31% of I+ ewes on maintenance rations. This information can guide feed management of prolific Inverdale ewes prior to breeding.

The Garole is a prolific breed of sheep. High prolificacy in sheep carrying the Booroola gene (FecB) is the result of a mutation in bone morphogenetic protein receptor-IB (BMPR-IB) (Wilson et al., 2001a,b) which had previously been identified in Garole sheep from the Sunderban region of West Bengal (Davis et al., 2002) . There is evidence that the breed has originated from the sheep brought by the Tibetan traders and traded in the plains of Bengal during the seventeenth till the nineteenth century. The present study was carried out to remap the distribution of the Garole sheep within the state of West Bengal (India) using the presence of the BMPR-IB mutation in the sheep flocks reared at different locations within the state of West Bengal. The breeding tract of Garole sheep was initially thought to be in the districts of 24 Parganas, South and North alone. However, the results from the present study indicate that the sheep is also reared in the district of Midnapur (East), besides in Jalpaiguri and Cooch Behar districts situated in northern parts of the state. The results of the present study indicate that the breeding tract of Garole sheep extends up to Jalpaiguri and CoochBehar districts of West Bengal at 26°16′ and 27°0′ North latitude and 88°4′ and 89°53′ East longitude. This study also indicates that the ancestors of the Garole sheep have migrated from China/Tibet, during the trading between West Bengal and Bangladesh during the seventeenth century till the earlytwentieth century.

We have constructed a genetic linkage map of the sheep X chromosome (OARX) containing 22 new gene loci from across the human X chromosome (HSAX). The female OARX linkage map has a total length of 152.6 cM with average gene spacing of 5.5 cM. Comparison with HSAX confirms one previously reported major breakpoint and inversion, and other minor rearrangements between OARX and HSAX. Comparison of the linkage map with sheep sequence data OAR 1.0 reveals a different arrangement of markers on the q arm, which may more accurately reflect the genuine arrangement of this region.

Introduction: A significant proportion of potential lambs are lost (commonly 15–20%) between ovulation and birth. Little is currently known about factors associated with multiple birth capacity of the uterus which are essential to convert gains in ovulation rate to live lambs. The relationship between maternal uterine and hormonal environment as well as the heritability of embryonic survival (ES) in prolific ewes is investigated. Methods: Litter size (LS) from known ovulation rate (OR) records (n = 6393) collected over 16 years were assessed for heritability with ASREML analysis and to identify the pedigree of outliers. From this flock, closely related high ovulation rate ewes with significantly different litter sizes (High ES; OR2.6/LS2.4 v. Low ES; OR2.9/LS1.6) were selected. Uterine anatomy collected from Day 14 cyclic (n = 5 High and n = 5 Low ES) and Day 16 pregnant ewes (n = 14 high and n = 10 Low) as well as systemic concentrations of hormones indicative of uterine (activin-A, follistatin) and ovarian (inhibin-{α}, progesterone) function were compared. Results and Discussion: ASREML analysis reported ES to be a trait of low repeatability (r = 0.10) and even lower heritability (h2 = 0.04). However, pedigrees of outlier animals indicated a segregation pattern consistent with a single autosomal gene with a major effect on enhanced ES. No anatomical differences between high and low ES ewes were discerned. However, significant differences for circulating levels of activin-A (depressed), time of activin-A peak (earlier), follistatin (elevated), progesterone (early rise) and inhibin-{α} (depressed) concentrations were found around the time of oestrus in High v. Low ES ewes. Given the involvement of activin-A in injury-induced inflammation, these results suggest a role for the activin-follistatin system, possibly through increased residency of immune cells and cytokine activation, for increasing ES in prolific ewes. Acknowledgements; Norma Hudson and Stan Lun for progesterone and inhibin-{α} assays.

Molecular information is finding increasing use in sheep and goat breeding programs, as systems become available to make use of this information and the cost of obtaining the information declines. Genetic markers have been used for parentage verification or determination, for product tracing or brand protection, and for assisting selection decisions for production or breeding stock. The predominant uses of markers in selection have been in selecting for scrapie resistance, high prolificacy and for increased size of higher value muscles. Most of these applications of selection have placed preferential emphasis on the favourable gene variant, and quantitative information is used to select within genotype. The sophisticated use of molecular and quantitative information on an industry-wide scale will require robust systems that can cope with imperfect data as well as development of selection indices to take full advantage of the information. The prospect for further increases in the use of molecular information looks bright.

Ovulation rates were measured in 547 progeny of 24 rams in a Romney flock with a long history of high prolificacy. These sheep were from the same family line and the distribution of ovulation rates suggests the presence of a segregating major gene (FecW) that increases prolificacy. The phenotype differs from those previously described for major genes affecting prolificacy in sheep. The putative gene shows autosomal inheritance and one copy increases ovulation rate by 0.8-1.0 eggs per ewe ovulating. To date, we have found no evidence of infertility among putative homozygous ewes, as described in some autosomal major genes for prolificacy.

Twenty-one of the world's prolific sheep breeds and strains were tested for the presence of the FecB mutation of BMPR1B and the FecXI mutation of BMP15. The breeds studied were Romanov (2 strains), Finn (2 strains), East Friesian, Teeswater, Blueface Leicester, Hu, Han, D'Man, Chios, Mountain Sheep (three breeds), German Whiteheaded Mutton, Lleyn, Loa, Galician, Barbados Blackbelly (pure and crossbred) and St. Croix. The FecB mutation was found in two breeds, Hu and Han from China, but not in any of the other breeds. The 12 Hu sheep sampled were all homozygous carriers of FecB (FecBB/FecBB) whereas the sample of 12 Han sheep included all three genotypes (FecBB/FecBB, FecBB/FecB+, FecB+/FecB+) at frequencies of 0.33, 0.58 and 0.08, respectively. There was no evidence of FecXI in any of the breeds sampled.

Woodlands are a line of Coopworth sheep with a novel, imprinted X-linked fecundity allele resulting in ovulation rates about 0.40 higher than wild-type animals. Daughters of progeny tested sires with and without the gene were studied. Previously, lambs heterozygous for the Woodlands allele were found to have larger ovaries and more antral (i.e. type 5) but not preantral (i.e. types 1–4) follicles than in wild-type contemporaries. The large ovary phenotype was found to be transient and was absent after puberty. However, based on follow-up studies it was evident that the large ovary phenotype was not strongly associated with the Woodlands fecundity allele. Thus, it was uncertain whether animals carrying the Woodlands gene had different follicular populations compared to wild-type controls. To address this question, follicular populations were compared in adult ewes heterozygous for the Woodlands allele with age-matched controls. Using standard morphometric methods and histological analysis, no differences were observed in the mean numbers of types 1, 1a, 2, 3 and 4 preantral follicles between the genotypes. Furthermore, no differences were observed between genotypes in follicular or oocyte diameters for any follicular type. The adult Woodlands carrier ewes had twice as many small type 5 follicles (< 1mm) when compared to wild-type contemporaries although no difference was seen in the numbers of antral follicles > 1mm in diameter. In addition, antrum formation occurred at a smaller follicular diameter in the heterozygous Woodlands animals. Therefore, the increased number of antral follicles observed in both lambs and adult ewes suggests that this difference in pattern of follicular development is associated with the X-linked fecundity allele. This novel phenotype of early antrum formation and larger number of small preantral follicles differs from that observed in sheep with the Inverdale or Booroola mutations, suggesting that a different mechanistic pathway is involved. Acknowledgements: The Marsden Fund, FRST and Ovita.

Since 1980 there has been increasing interest in the identification and utilisation of major genes for prolificacy in sheep. Mutations that increase ovulation rate have been discovered in the BMPR-1B, BMP15 and GDF9 genes, and others are known to exist from the expressed inheritance patterns although the mutations have not yet been located. In the case of BMP15, four different mutations have been discovered but each produces the same phenotype. The modes of inheritance of the different prolificacy genes include autosomal dominant genes with additive effects on ovulation rate (BMPR-1B; Lacaune), autosomal over-dominant genes with infertility in homozygous females (GDF9), X-linked over-dominant genes with infertility in homozygous females (BMP15), and X-linked maternally imprinted genes (FecX2). The size of the effect of one copy of a mutation on ovulation rate ranges from an extra 0.4 ovulations per oestrus for the FecX2 mutation to an extra 1.5 ovulations per oestrus for the BMPR-1B mutation. DNA tests enable some of these mutations to be used in genetic improvement programmes based on marker assisted selection.

Two related oocyte-derived members of the transforming growth factor-β (TGF-β) superfamily, namely growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15, also known as GDF9B), have recently been shown to be essential for ovarian follicular growth. In addition, both proteins have been shown to regulate ovulation rate in sheep, and although it is evident that these growth factors interact both with one another and with other intra- and extra-ovarian factors, the precise mechanisms by which they influence follicular growth and ovulation rate have not been thoroughly elucidated.