Ewes with higher embryo survival rear lambs that grow faster.

A key economic driver of a meat producing sheep flock is the total kilograms of lamb liveweight at weaning per ewe exposed to the ram. Optimization of key reproductive steps is required to achieve peak performance of a sheep flock. The goal of this paper was to use more than 56,000 records from a commercial flock to investigate the key reproductive steps affecting flock reproductive performance.

The follicular microenvironment in low (++) and high (I+B+) ovulation rate ewes.

Ewes with single copy mutations in GDF9, BMP15 or BMPR1B have smaller preovulatory follicles containing fewer granulosa cells (GC), while developmental competency of the oocyte appears to be maintained. We hypothesised that similarities and/or differences in follicular maturation events between WT (++) ewes and mutant ewes with single copy mutations in BMP15 and BMPR1B (I+B+) are key to the attainment of oocyte developmental competency and for increasing ovulation rate (OR) without compromising oocyte quality. Developmental competency of oocytes from I+B+ animals was confirmed following embryo transfer to recipient ewes.

Early embryo loss, morphology, and effect of previous immunization against androstenedione in the ewe.

In a naturally mated cycle, ova and viable embryo number as well as embryo size were assessed on Day 4, 10, 14, 18, and 30 of gestation in Romney ewes (n = 38-44 per gestational group). For Days 4-18 of gestation, embryos were recovered by flushing the reproductive tract after slaughtering of the ewe. Ovulation rate was determined by counting the number of corpora lutea present on both ovaries.

Reduced ovulation rate, failure to be mated and fertilization failure/embryo loss are the underlying causes of poor reproductive performance in juvenile ewes.

A ewe that is mated as a juvenile (producing a lamb at 1 year of age) will produce an average of only 0.6 lambs to weaning, compared to an average of 1.2 lambs in adult ewes.

Activin A and follistatin during the oestrous cycle and early pregnancy in ewes.

The activin pathway has been postulated to be involved in regulation of multiple reproductive processes important for survival of the conceptus. These processes include luteinisation of the follicular cells and thus function of the corpus luteum, early embryo development and uterine function including implantation of the conceptus. Therefore, the aim of the current study was to determine whether the concentrations of activin A and follistatin (FST), an activin-binding protein, differed between ewes with a lifetime history of enhanced or reduced embryonic survival (ES).

Mutations in the leptin receptor gene associated with delayed onset of puberty are also associated with decreased ovulation and lambing rates in prolific Davisdale sheep.

The aim of this study was to determine if single nucleotide polymorphisms (SNPs) in the leptin receptor (LEPR) gene associated with delayed onset of puberty are associated with changes in other reproductive traits in adult ewes. The ovulation rate of ewes homozygous for the SNPs was ~15% lower (PPLEPR SNPs than their wild-type or heterozygous contemporaries. Partial failure of multiple ovulations was also increased (PLEPR had on average 0.

Single-nucleotide polymorphisms in the LEPR gene are associated with divergent phenotypes for age at onset of puberty in Davisdale ewes.

Attainment of puberty is a key developmental event influenced by genetic and environmental factors. In examining age at attainment of puberty, we observed closely related rams from the Davisdale line whose daughters differed in age at which they attained puberty. A candidate gene approach was used to identify mutations that may underlie these observed differences.

An earlier rise in systemic progesterone and increased progesterone in the uterine vein during early pregnancy are associated with enhanced embryonic survival in the ewe.

Improved livestock production efficiency through greater embryonic survival (ES) is of economic and animal welfare benefit. Physiological characterization of animals that are extreme outliers for ES provides a valuable opportunity to identify a naturally occurring mechanism by which this trait may be enhanced. The objective was to determine the likely cause for the lifetime history of enhanced or reduced ES in a line of ewes selected for high fecundity.

Identification of a line of sheep carrying a putative autosomal gene increasing ovulation rate in sheep that does not appear to interact with mutations in the transforming growth factor beta superfamily.

Sheep lines with mutations in single genes that have major effects on ovulation rate have been very useful in gaining a better understanding of pathways important in controlling follicular development and ovulation rate. To date however, all known mutations are in the transforming growth factor beta (TGFB) superfamily. Ovulation rates were measured in 720 progeny of 20 rams that were descendants of a single prolific ewe.

Postnatal uterine development in Inverdale ewe lambs.

Postnatal development of the uterus involves, particularly, development of uterine glands. Studies with ovariectomized ewe lambs demonstrated a role for ovaries in uterine growth and endometrial gland development between postnatal days (PNDs) 14 and 56. The uterotrophic ovarian factor(s) is presumably derived from the large numbers of growing follicles in the neonatal ovary present after PND 14.

Patterns of expression of messenger RNAs encoding GDF9, BMP15, TGFBR1, BMPR1B, and BMPR2 during follicular development and characterization of ovarian follicular populations in ewes carrying the Woodlands FecX2W mutation.

Woodlands sheep have a putative genetic mutation (FecX2(W)) that increases ovulation rate. At present, the identity of FecX2(W) is unknown. The trait does not appear to be due to the previously described mutations in bone morphogenetic protein 15 (BMP15), growth differentiation factor 9 (GDF9), or bone morphogenetic protein receptor type 1B (BMPR1B) that affect ovulation rate in sheep.

Growth differentiation factor 9 and bone morphogenetic protein 15 are essential for ovarian follicular development in sheep.

The aim of this study was to test the hypothesis that both growth differential factor 9 (GDF9) and bone morphogenetic protein (BMP15; also known as GDF9B) are essential for normal ovarian follicular development in mammals with a low ovulation rate phenotype. Sheep (9-10 per group) were immunized with keyhole limpet hemocyanin (KLH; control), a GDF9-specific peptide conjugated to KLH (GDF9 peptide), a BMP15-specific peptide conjugated to KLH (BMP15 peptide), or the mature region of oBMP15 conjugated to KLH (oBMP15 mature protein) for a period of 7 mo and the effects of these treatments on various ovarian parameters such as ovarian follicular development, ovulation rate, and plasma progesterone concentrations evaluated. Also in the present study, we examined, by immunohistochemistry, the cellular localizations of GDF9 and BMP15 proteins in the ovaries of lambs.