Meat eating and nutritional quality of lambs sired by high and low muscle density rams.

Intramuscular fat (IMF) content affects eating and nutritional quality of lamb meat. Muscle density measured by computer tomography is an in vivo proxy measure of IMF content that affects eating and nutritional quality of lamb meat. Lambs sired by high muscle density (HMD) or low muscle density (LMD) rams, selected for slaughter on commercial criteria were measured for meat quality and nutritional traits.

Population structure and history of the Welsh sheep breeds determined by whole genome genotyping.

Background: One of the most economically important areas within the Welsh agricultural sector is sheep farming, contributing around £230 million to the UK economy annually. Phenotypic selection over several centuries has generated a number of native sheep breeds, which are presumably adapted to the diverse and challenging landscape of Wales. Little is known about the history, genetic diversity and relationships of these breeds with other European breeds.

Heterogeneous variances and genetics by environment interactions in genetic evaluation of crossbred lambs.

Accounting for environmental heteroscedasticity and genetics by environment interaction (G×E) in genetic evaluation is important because animals may not perform predictably across environments. The objectives of this study were to evaluate the presence and consequences of heteroscedasticity and G×E on genetic evaluation. The population considered was crossbred lambs sired by terminal sires and reared under commercial conditions in the UK.

Effect and mode of action of the Texel muscling QTL (TM-QTL) on carcass traits in purebred Texel lambs.

TM-QTL is a quantitative trait locus (QTL) on ovine chromosome 18 (OAR18) known to affect loin muscling in Texel sheep. Previous work suggested that its mode of inheritance is consistent with paternal polar overdominance, but this has yet to be formally demonstrated. This study used purebred Texel sheep segregating for TM-QTL to confirm its presence in the chromosomal region in which it was first reported and to determine its pattern of inheritance.

Flood-related contamination in catchments affected by historical metal mining: an unexpected and emerging hazard of climate change.

Floods in catchments affected by historical metal mining result in the remobilisation of large quantities of contaminated sediment from floodplain soils and old mine workings. This poses a significant threat to agricultural production and is preventing many European river catchments achieving a 'good chemical and ecological status', as demanded by the Water Framework Directive. Analysis of overbank sediment following widespread flooding in west Wales in June 2012 showed that flood sediments were contaminated above guideline pollution thresholds, in some samples by a factor of 82.

Progesterone exposure of seasonally anoestrous ewes alters the expression of angiogenic growth factors in preovulatory follicles.

Small-dose, multiple injections of GnRH given to seasonally anoestrous ewes induce final stages of the preovulatory follicle development, but result in an high incidence of defective CL unless animals are primed with progesterone, which completely eliminates luteal dysfunction. Progesterone priming upregulates luteal vascularization; however, its effect on follicular angiogenesis is poorly understood. This study tested the hypothesis that progesterone priming of seasonally anoestrous ewes treated with dose multiple injections of GnRH eliminates defective luteal function by altering the expression of vascular endothelial growth factor (VEGF), VEGF receptor-2, angiopoietin (ANG)-1, ANG-2, and TIE-2 during early and late preovulatory follicle development.

Genetic evaluation of days to harvest in crossbred lambs.

Days to harvest (DTH) is the number of days a lamb is fed before reaching a target level of fatness. Although economically relevant, this trait has not been thoroughly evaluated in sheep. Most lambs harvested in the United Kingdom are crossbreds sired by purebred terminal sires, with Charollais, Suffolk, and Texel most commonly used.

Index selection in terminal sires improves lamb performance at finishing.

Lamb meat is often perceived by consumers as fatty, and consumption has decreased in recent decades. A lean growth index was developed in the UK for terminal sire breeds to increase carcass lean content and constrain fat content at a constant age end point. The purposes of this study were 1) to evaluate the effects of index selection of terminal sires on their crossbred offspring at finishing and 2) to evaluate its effectiveness within terminal sire breeds.

Progesterone exposure of the preovulatory follicle in the seasonally anestrous ewe alters the expression of angiogenic growth factors in the early corpus luteum.

Gonadotrophin releasing hormone (GnRH)-induced ovulation in seasonally anestrous ewes is associated with a high incidence of defective corpora lutea (CL), which can be completely eliminated by priming ewes with progesterone before GnRH treatment, but the physiological basis of this has remained elusive. This study tested the hypothesis that progesterone priming eliminates defective luteal function by altering the expression of Vascular Endothelial Growth Factor (VEGF), its receptor VEGFR-2, and angiopoietin (ANG)-1, ANG-2 and their receptor TIE-2 in the early CL. Fifteen seasonally anestrous ewes were treated by i.

Cervical expression of hyaluronan synthases varies with the stage of the estrous cycle in the ewe.

The natural cervical relaxation which occurs at estrus in the ewe may be initiated by binding of hyaluronan (HA) to its receptor CD44. Indeed, we have previously shown that HA content and fragment size in the ovine cervix varies with the stage of the estrous cycle. Despite the importance of cervical relaxation in promoting sperm transport and facilitating the possible development of transcervical artificial insemination (AI), the mechanisms coordinating these changes in HA content remain to be defined.

Index selection in terminal sires improves early lamb growth.

The use of terminal sires (TS) for crossbreeding is integral to the UK sheep industry where approximately 71% of market lambs are sired by TS rams. Early growth of these crossbred lambs affects profitability. The objectives of this study were i) to evaluate the effectiveness of index selection among TS on BW and ADG of their crossbred offspring; and ii) to compare the efficacy of that selection within TS breeds.

Genotypic effects of the Texel Muscling QTL (TM-QTL) on meat quality in purebred Texel lambs.

Texel Muscling QTL (TM-QTL) increases loin muscling in lambs inheriting it from their sire only. This study investigated TM-QTL effects on meat quality in 209 Texel lambs that were CT-scanned then slaughtered at 20weeks (carcasses aged for ~1week). Loin meat quality traits included: CT-measured muscle density (predicting intramuscular fat); mechanical tenderness using Volodkevich-type jaws or MIRINZ tenderometer; intramuscular fat; sensory eating quality (sub-sample of 40 lambs).

Evaluating the effects of a single copy of a mutation in the myostatin gene (c.*1232G>A) on carcass traits in crossbred lambs.

This study evaluated the effects of the ovine c.*1232G>A myostatin mutation (MM) on carcass traits in heterozygous crossbred lambs sired by Texel and Poll Dorset rams using ultrasound, CT scanning, carcass classification and VIA. In experiment 1, MM was associated with increased loin depth (+2.

Intracervical application of hyaluronan improves cervical relaxation in the ewe.

Artificial insemination (AI) using frozen semen is a key method to enable rapid genetic improvement but its use in the sheep industry is currently limited by poor fertility. Laparoscropic AI is most effective but has not gained popularity due to cost and welfare considerations. Transcervical intrauterine AI (TCAI) may offer a practical alternative but the complex anatomy of the ovine cervix limits adequate penetration of the inseminating pipette.

Comparison of repeatability and multiple trait threshold models for litter size in sheep using observed and simulated data in Bayesian analyses.

Bayesian analyses were used to estimate genetic parameters on 5580 records of litter size in the first four parities from 1758 Mule ewes. To examine the appropriateness of fitting repeatability (RM) or multiple trait threshold models (MTM) to litter size of different parities, both models were used to estimate genetic parameters on the observed data and were thereafter compared in a simulation study. Posterior means of the heritabilities of litter size in different parities using a MTM ranged from 0.

The effect of the Texel muscling QTL (TM-QTL) on meat quality traits in crossbred lambs.

A quantitative trait locus (QTL) has been identified on chromosome 18 in Texel sheep (TM-QTL) that increases depth and area of the longissimus dorsi muscle. The study aimed to assess the pleiotropic QTL effects on key meat quality traits (toughness and intramuscular fat content after >or=7 days aging) of crossbred lambs carrying one copy of the TM-QTL. The results showed that male TexelxMule lambs carrying the TM-QTL had significantly less intramuscular fat (1.

The effect of conditioning period on loin muscle tenderness in crossbred lambs with or without the Texel muscling QTL (TM-QTL).

A Texel muscling quantitative trait locus (TM-QTL) has been identified on chromosome 18, which increases loin muscling, but may also have a negative impact on mechanically-measured loin tenderness in crossbred lambs, depending on conditioning time. This study investigated the influence of a range of conditioning times (3, 5, 7 or 9 days) on the effect of TM-QTL on loin muscle tenderness. Using Texel rams heterozygous for TM-QTL, mated to non-carrier Mule ewes, heterozygous (n=45) and wild-type (n=50) crossbred lambs were produced.

Hyaluronan (HA) content, the ratio of HA fragments and the expression of CD44 in the ovine cervix vary with the stage of the oestrous cycle.

The complex anatomy of the ovine cervix limits the success of trans-cervical artificial insemination in sheep. However, there is a degree of natural relaxation of cervix at oestrus that is accompanied by an increase in the water content. As hyaluronan (HA) has a high affinity for water molecules, in this study, we tested the hypothesis that the HA content of the cervix, the proportion of different size fragments of HA and expression of its receptor CD44 vary with the stage of the oestrous cycle.

The effects of a loin muscling quantitative trait locus (LoinMAX™) on carcass and VIA-based traits in crossbred lambs.

LoinMAX (LM) is a quantitative trait locus (QTL), which was found to be segregated in Australian Poll Dorset sheep, and maps to the distal end of sheep chromosome 18. LM-QTL was reported to increase Musculus longissimus dorsi area and weight by 11% and 8%, respectively. The aim of this study was to comprehensively evaluate the direct effects of LM-QTL in a genetic background typical of the stratified structure of the UK sheep industry, before it can be recommended for use in the United Kingdom.

Modulating peripheral gonadotrophin levels affects follicular expression of mRNAs encoding insulin-like growth factor binding proteins in sheep.

Evidence suggests that the insulin-like growth factor binding proteins (IGFBPs) are involved in modulating the role that IGF-I and -II play in regulating follicular growth and development in sheep. However, little information exists as to the role that key peripheral factors play in regulating the expression of IGFBP components within the follicle. The present study investigated the regulatory effects of FSH and LH on gene expression for IGFBP-2 to -6 in ovine follicles, using bovine follicular fluid (bFF) and gonadotrophin-releasing hormone antagonist (GnRHa) model systems to perturb endogenous gonadotrophin secretion.

Effects of a quantitative trait locus for increased muscularity on carcass traits measured by subjective conformation and fat class scores and video image analysis in crossbred lambs.

A quantitative trait locus (QTL) for increased loin muscularity (TM-QTL) has previously been identified in purebred Texel sheep. Crossbred lambs born out of Mule ewes mated to heterozygous Texel sires for the TM-QTL were evaluated for a range of carcass traits. Lambs were genotyped and classified as carriers (n = 62) of a single copy of the TM-QTL and non-carriers (n = 49).

Genetic relationship between longevity and objectively or subjectively assessed performance traits in sheep using linear censored models.

Genetic parameters of longevity in crossbred Mule ewes, and genetic relationships among longevity, growth, body composition, and subjectively assessed traits on Mule lambs and ewes have been estimated using Bayesian linear censored models. Additionally, the genetic associations between longevity and culling reasons were examined. Data comprised 1,797 observations of Mule ewes for longevity, culling reasons, growth, body composition, mouth scores, and type traits.

Effects of the Texel muscling quantitative trait locus on carcass traits in crossbred lambs.

Texel muscling quantitative trait locus (TM-QTL) is a QTL on chromosome 18, originally identified in purebred UK Texel sheep, which was reported to increase ultrasonically measured muscle depth at the third lumbar vertebra by around 4% to 7%. The objective of the present study was to comprehensively evaluate the TM-QTL and to determine whether it could provide benefits to the UK sheep industry through increased carcass meat yield in crossbred slaughter lambs. Effects of this QTL on a range of carcass traits, including those measured in vivo and by dissection, were evaluated in heterozygous carrier and non-carrier lambs produced by crossing heterozygous carrier Texel rams with non-carrier Mule (Bluefaced Leicester × Scottish Blackface) ewes from a lowland flock.

Associations between lamb survival and prion protein genotype: analysis of data for ten sheep breeds in Great Britain.

Background: Selective breeding programmes, based on prion protein (PrP) genotype, have been introduced throughout the European Union to reduce the risk of sheep transmissible spongiform encephalopathies (TSEs). These programmes could have negative consequences on other important traits, such as fitness and production traits, if the PrP gene has pleiotropic effects or is in linkage disequilibrium with genes affecting these traits. This paper presents the results of an investigation into associations between lamb survival and PrP genotype in ten mainstream sheep breeds in Great Britain (GB).

Genetic parameters for carcass composition and performance data in crossbred lambs measured by Video Image Analysis.

A total of 7074 crossbred lambs, produced by mating crossbred Mule ewes with terminal sire rams were used in this study. Of these, 630 were scanned using a Video Image Analysis (VIA) to estimate carcass quality traits. Genetic parameters for average daily gain (ADG), scanning live weight (SW), ultrasonic measures of muscle (UMD) and fat (UFD) depths, cold carcass weight (CCW) and VIA measurements of primal carcass joint weights (LEG, CHUMP, LOIN, BREAST and SHOULDER) were estimated using multivariate animal models.