Shape of the carcass is considered important commercially and is usually assessed using a subjective score for conformation. Carcasses of higher conformation are perceived to have higher lean to bone (L:B) ratios and give joints of better shape at a weight, characterised as shorter and having a greater thickness of muscle. Some of these benefits have been shown, but so has a positive association between conformation and fatness. Purchas et al. (1991) proposed that muscularity indices could be used as an alternative to the conformation score. The objectives of this study were to investigate the relationships between muscularity, shape of joints and composition within breeds and the relationships between different muscularity indices. Knowledge of the latter relationships is important to determine how many indices are required to adequately describe carcass muscularity.

Conformation is often given high priority as a selection objective by pedigree breeders who consider this trait to be related to lean yield and distribution, despite experimental evidence to the contrary. The Texel crossbred lamb is known to have a high lean yield at a given liveweight and in considering the results of breed comparison trials Croston et al (1987) speculated that there may be variation between strains for this trait, possibly associated with differences in conformation. Support for this suggestion comes from the work of Leroy (1989) who reported that the Belgian Texel with a heavily muscled conformation (“double muscled”) had a higher killing-out proportion and lean yield than sheep with conventional shape. The aim of this trial was to investigate potential differences in the carcass traits of pure-bred Texel lambs of extreme versus conventional conformation

Smith (1986) identified the theoretical potential of multiple ovulation and embryo transfer (MOET) to increase the rate of genetic improvement within nucleus sheep breeding flocks by upto 100%. The likely genetic benefits of MOET arise from the potential to overcome limits to female reproduction thus allowing increased selection intensity and reduced generation intervals among females. The present study was conducted to evaluate the potential for MOET from 18 month-old maiden ewes (gimmers) in comparison with aged donor ewes.

In October 1991, a group of twenty 18-month old ewes and twenty aged ewes (3.5 year-old) were synchronised into oestrus using intravaginal pessaries containing 45 mg Cronolone (Chronogest, Intervet Laboratories Ltd.) inserted for 12 days. Superovulation was achieved using 20 i.u. of ovine follicle stimulating hormone (Ovagen, Immuno-Chemical Products N.Z. Ltd) given in eight equal doses at 12-hourly intervals starting 58 hours before progestagen pessary withdrawal.

Combined multiple ovulation and embryo transfer (MOET) from ewe lambs could significantly increase the rate of genetic progress in sheep improvement programmes (Smith, 1986). The benefits arise from a combination of an increased number of progeny from superior females and a reduction in the generation interval. Maximum success requires that the procedures are carried out in ewe lambs at six to seven months of age to produce offspring when the donors are one year old. Previous studies suggest that embryo quality and survival rates are naturally lower in ewe lambs and are likely to limit the success of MOET in this class of animal (Quirke and Hanrahan, 1977; McMillan and McDonald, 1985). The present study was undertaken to evaluate the potential of recently developed superovulatory procedures for application to ewe lambs.