Evolution of the sheep coat: the impact of domestication on its structure and development

Wild sheep and many primitive domesticated breeds have two coats: coarse hairs covering shorter, finer fibres. Both are shed annually. Exploitation of wool for apparel in the Bronze Age encouraged breeding for denser fleeces and continuously growing white fibres. The Merino is regarded as the culmination of this process. Archaeological discoveries, ancient images and parchment records portray this as an evolutionary progression, spanning millennia. However, examination of the fleeces from feral, two-coated and woolled sheep has revealed a ready facility of the follicle population to change from shedding to continuous growth and to revert from domesticated to primitive states. Modifications to coat structure, colour and composition have occurred in timeframes and to sheep population sizes that exclude the likelihood of variations arising from mutations and natural selection. The features are characteristic of the domestication phenotype: an assemblage of developmental, physiological, skeletal and hormonal modifications common to a wide variety of species under human control. The phenotypic similarities appeared to result from an accumulation of cryptic genetic changes early during vertebrate evolution. Because they did not affect fitness in the wild, the mutations were protected from adverse selection, becoming apparent only after exposure to a domestic environment. The neural crest, a transient embryonic cell population unique to vertebrates, has been implicated in the manifestations of the domesticated phenotype. This hypothesis is discussed with reference to the development of the wool follicle population and the particular roles of Notch pathway genes, culminating in the specific cell interactions that typify follicle initiation.

Evolution of the Meat Standards Australia (MSA) beef grading system

The Australian Beef Industry identified variable eating quality as a major contributor to declining beef consumption in the early 1990s and committed research funding to address the problem. The major issue was the ability to predict the eating quality of cooked beef before consumption. The Meat Standards Australia (MSA) program developed a consumer testing protocol, which led to MSA grading standards being defined by consumer score outcomes. Traditional carcass grading parameters proved to be of little value in predicting consumer outcomes. Instead a broader combination of factors forms the basis of an interactive prediction model that performs well. The grading model has evolved from a fixed parameter ‘Pathway’ approach, to a computer model that predicts consumer scores for 135 ‘cut by cooking method’ combinations for each graded carcass. The body of research work conducted in evaluating critical control points and in developing the model predictions and interactions has involved several Australian research groups with strong support and involvement from the industry.

Effect of repeated implants of oestradiol-17β on beef palatability in Brahman and Braham cross steers finished to different market end points

The effect of repeated implantation with 20 mg oestradiol-17β (Compudose 100) on carcass and meat quality traits was investigated using 478 Bos indicus and B. indicus × Bos taurus cross steers finished on either pasture or grain to achieve carcass weight for one of three market end points (domestic, 220 kg; Korean, 280 kg; or Japanese, 340 kg). In the oestradiol-17β treatment group, animals were administered implants at ~100-day intervals, with the number of implants administered to any steer ranging from one to eight. Cattle were slaughtered and at boning the anterior portion of the M. longissimus lumborum was removed and frozen after aging for 1 day for later objective meat quality measurements (shear force, compression and cook loss %). The adjoining portion was aged for 14 days before consumer sensory testing using the Meat Standards Australia protocols. Each sample was scored for tenderness, juiciness, like flavour and overall liking by 10 untrained consumers. Implanting increased carcass weights and ossification scores (P < 0.05) and reduced marbling scores in comparison to non-implanted carcasses. For tenderness, like flavour, overall liking and MQ4 scores there was a significant (P < 0.05) interaction between B. indicus content and oestradiol-17β treatment, whereby high B. indicus content cattle that were implanted with oestradiol-17β had the lowest sensory scores. The number of implants administered did not affect carcass weights or marbling scores, whereas ossification scores increased in carcasses as the number of implants increased. The number of implants administered had no effect (P > 0.05) on sensory scores, or objective meat tenderness.