Sheep - AgRIS

5.6.3 Wool Production/Wool yield and Wool Quality
Wool production is largely dependent upon fleece weight and staple length. Greater gains
are obtained with increas,y in staple length in both the fine-wool and the coarse-wool breeds.
With some breeds, selection may have to be practiced against coarseness of wool, but selection
should be practiced for the grade of wool most desirable in a particular area.
Heritability estimates show that most wool characterislics are highly heritable. The average
heritability of fleece weight has been estimated as 40 per cent, and of staple length as 45
percent. Theseheritabilityestimates are high enough that the mating together of the best
individuals for these two traits should result in genetic improvement, and because of their
economic value, these tvraits should be given attention in a breeding program.
Face covering in ewes is an important economic trait. Open-faced ewes produce more
lambs and wean more pounds of lamb than those with wool-covered faces.
5. 6.4 Carcass yield
Evaluation of carcass can be done when intact or partially cut or as wholesale cuts or retail
cuts or meat.
Evaluation of an intact carcass depends on its conformation and finish. The most desirable
carcass conformation is the one which will yield the greatest quantity of edible meat. Wellfinished
carcasses show greater depth of fat over the back and rumps, a covering of smooth
white interior fat over the kidneys, much thinner covering over the inner surface of ribs and
liberaWeposits of fat between the muscles. Poorly finished carcasses show marked deficiency
of extemal and intemal fat with uneven distribution of soft, flabby and yellowish fat. Hot
carcass weight, carcass weight/day of age and dressing percentage (carcass weightAive weight
x 100) are three useful criteria which will help in comparing carcasses of sheep from different
famms, breeds, sires, or production systems.
As consumers would hesitate to buy cuts wlth more bone and fat, their production is not
economical. A carcass with higher lean to fat and lean to bone ratio should be the goal of any
sheep husbandry system meant for meat production. In a country like ours where information
on preferences for or against is not available, clubbing together meat and fat for meat to bone
ratio estimation may be reasonable. However, in the long run due emphasis given for
production, of optimum amount of fat in the carcasses will help.
There is very less information about carcass quality and the degree of heritability of the
various carcass items. Studies to gain such information are in progress, and results should be
available in the near future. Since nearly all carcass traits are highly heritable in swine and beef
cattle, it seems very likely that the same will also be found true in sheep. Tendemess and a high
proportion of lean to fat in mutton undoubtedly are needed to meet consumer desires.
At present, the proportion of leanness and tenderness of mutton can be measured only after
the animal is slaughtered, making it impossible to measure this trait in animals to be used for
breeding purposes. The next best measurement is probably that made in the close relatives of an
individual.
Carcass information may also be obtained on the progeny of a ram, but the same
disadvantage of progeny tests applies in sheep as in other classes of farm animals . It takes so
long to get a good progeny test that the ram may be dead before his worth is fully known. Once
he is progeny tested, however, and proved to be superior, whether he is dead or living, his
offspring should be given preference when selecting breeding animals. If he is dead when the
results of prgeny tests are fully known, there is still the possibility of keeping the relationship of
individuals in the flock closer to the outstanding ancestor through linebreeding.
5.6.5 Carcass Quality
When a carcass is partially cut by ribbing at 12th and 13th ribs intersection, area of
longissimus dorsi, its colour and marbling, fat thickness over the 12th rib, and per cent kidney
and pelvic fat can be used to evaluate carcasses and grade them.
Sheep carcasses can be cut into 5 major wholesale cuts, viz. leg, loin, rack, neck and
shoulder (with 4 ribs) and breast and shank. They can be further trimmed into retail cuts
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