Evaluation of Slaughter Lambs

Evaluation of Slaughter Lambs - EVALUATION OF SLAUGHTER...

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Unformatted text preview: EVALUATION OF SLAUGHTER LAMBS D . E. Eversole The biological factors which determine profit from-commercial ewe flocks in order of their importance are: 1. Raising a high percent lamb crop because it increases the pounds of lamb marketed per ewe per year. 2. Raising fast growing lambs by mating growthy, muscular rams to medium sized ewes in a crossbreeding program. Rapid growth rate in lambs is positively associated with feed efficiency and yield of properly finished retail cuts. The use of small to medium sized ewes reduces the feed maintenance cost of the ewe flock for the year. 3. Marketing properly finished lambs at no less than Choice quality grade. ' The initial purpose of this discussion is to assist the producer in determining number 3 above; which lambs are ready to be marketed for slaughter. If lamb producers are to attract more lamb consumers, the first criterion to determine when lambs should be marketed is proper degree of finish. Consumers also will purchase the lamb chops with a larger cross section of muscle. Therefore, the discussion of determining the correct amount of finish will be followed by an identification of live lamb muscling. Most market lambs are sold to slaughter plant buyers so included is information on factors that determine live lamb value. - Can I Make the Marketing Decision by Using Only a Scales? The use of a scales will.be helpful in making the decision, particularly if you are one of the many new lamb producers. However, relying only on the scales is not sufficient as some types of lamb reach market finish at 85 pounds whereas others would weigh 115 pounds or more. On page 2, Figure 1, the body outline of three different types of lambs is presented along with the slaughter data on each. Genetics or breeding determines the scale or frame size of lambs and the weight at which they are correctly finished. Breeding also determines the amount of muscling. The ration fed and the length of time on feed determines the amount of fat. It is of interest to note the increase in average liveweight of lambs slaughtered under Federal Meat Inspection over time in Figure 2. Lamb producers are responsible for the increase in slaughter weight. As costs of production increased, producers needed to market more pounds of lamb per ewe. A change to marketing heavier lambs was achieved more easily and quickly than increasing the number of lambs marketed per ewe. The increase in weight had a major influence on the popularity of breeds. The ram that sired the 80 pound slaughter lamb could not sire a trimly—finished 110 pound lamb. Determining the Amount of Finish Increasing fatness reduces the percent of boneless meat which is trimmed of excess fat. Fat does not encourage consumption. However, some fat is necessary to package the delicate lean in shipment and handling. Slaughter lambs should have a minimum of 0.10 inch of external fat over the center of the rib-eye muscle. This may be slightly fatter than the carcass you might prefer for your freezer. Figure 3, demonstrates where measurements are taken on the carcass. Figure 1. Liveweight - 85# Ext. Fat - 0.2 in. Rib Eye - 2.1 Sq. in. Grade - Prime‘ Y1e1d Grade - 2.4 Lamb No. 1" Small-Framed Lamb. Grading Prime' at 85 Pounds. Liveweight - 103# Ext. Fat - 0.1 in. Rib Eye - 2.5 Sq. in. Grade - Choice+ Yield Grade - 1.4 Liveweight - 102# Ext. Fat — 0.35 in. Rib Eye - 1.8 Sq. in. Grade - Choice° Yier Grade - 3.9 Lamb No. 3. Ta11, Light-Musc1ed and Uverfat. Should Have Been S1aughtered At 85#. Figure 2. Average Liveweight of Slaughter Lambs (1920-1980). 120 110 100 Pounds 90 80 70 1920 '30 '40 'so '60 '7of“'ao Year Lambs are fatter down over the ribs and it is usual for a carcass with 0.1 inch ' over the rib eye to have 0.3 inch of external fat measured two inches away from the end of the eye muscle. Figure 3. Cross Section of a Lamb Carcass Cut Between the 12th and 13th Ribs. Handling Lambs for Finish By keeping the fingers together and using the bulbs of the fingers, the lamb is handled where bone underlies the skin. A lamb with 0.15 inches of fat will have the following handling characteristics. Variations for thinner and fatter are included with each body region being handled. 1. The ribs definitely can be felt. The fat cover over the ribs is consistently thicker than over the back. If ribs cannot be palpated, the lamb is grossly overfat. If the ribs are sharp and feel like grandma's washboard, the lamb is too thin to be marketed. 4 The spinal processes of the backbone are easily located. An under- finished lamb gives an impression of sharpness. As the lamb.fattens, the processes become more blunt and will be cushioned with fat. If individual processes cannot be felt, the lamb will have at least 0.25 inches of fat. In spanning the width of loin, the ends of the transverse processes can be felt. The individual processes cannot be felt with increasing fatness. The loin becomes wider and deeper at the loin edge with additional fat. The hip bones are slightly prominent. The point of the shoulder is hard and not cushioned with fat. Overfat lambs have a "groove" along the backbone over the rump and dock area formed by fat building up on each side of the bone. When handling, fat is soft and does not retain shape. Muscle is firm and rounded. Bone is hard. For example, palpate the inside muscling of the leg. The muscle is firm and its shape can be determined. The fat in the twist is soft and does not interfere with feeling the muscle. Extreme depth of twist is due to fat. Visual Appraisal of Fatness With some practice, your eyes can observe differences in the amount of finish as fattening changes the conformation. Referring to the outlines on page 2 will be an excellent supplement to the following discussion: 1. Correctly finished lambs will be wider through the rump and shoulder than in the back and loin. Fattening widens the back and loin and in light-muscled lambs can become as wide as the rump and shoulder. Grossly overfinished lambs will be wider in front and narrow up to the rear. Adding fat changes the contour of the top from side to side. Overfat lambs tend to be flat, properly-finished lambs are rounded in their turn of top. Thin lambs, particularly light muscled lambs, will have a V—shaped turn. The V will obviously be upside down. A properly finished lamb is cut up in its rear flank and may give the impression of lacking depth. Increasing fatness adds depth to the breast, foreflank, rear flank and twist. Fat increases the percentage of the cheaper cuts of meat (the breast and flank). The breast increases in depth, width and fullness (prominence) as fattening increases. Desirably finished lambs are trim and clean in the breast. The point of the elbow can be easily seen on a trim lamb. Rib fat on a fat lamb will fold down around the elbow. A trim lamb will be cut up in its twist and the muscle shape can be seen. Increasing fatness deepens the twist and covers up the muscle shape. 5 Visual Signs of Muscling When a judge states that one lamb has more muscle than another, it means that the muscular lamb will display more square inches of red meat in the rib-eye. With lamb carcasses weighing 50 to 60 pounds, more muscle is necessary to produce a satisfactory lamb chop. It is of greater importance in lamb than in pork or beef as those species are slaughtered at heavier weights; thus, their size automatically produces a greater lean surface area in the retail cut. A larger rib-eye area of lamb is associated with the following characteristics: 1. More width through the lower legs as viewed from the rear. There is little or no fat at that location so the width is red meat. The lamb should be thickest at this location. 2. Width of rump and shoulder. Heavy muscled lambs are wider through the rump and shoulder than through the back and loin. 3. Muscling on the inside of the hind leg can be observed as it has curve to it. A flat muscled lamb lacks thickness. Also more inside muscle causes the lamb to stand wider apart on its hind legs. 4. The turn of top associated with width of top. Muscular lambs have wider backs and loins and when correctly finished the topline has curve to it from one side over the backbone to the other side. Flat, wide loins are achieved with too much fat. 5. The forearm and lower stifle are the last places to be covered with fat. Therefore, a bulging forearm and prominent stifle are indicators of more muscling. 6. On the average the wholesale cut of leg is 40% of the carcass value. Long rumps, length from stifle joint to muscling on the back of the leg and length from hip to hock all contribute to a higher percent of leg. Increasing fatness decreases percentage of leg. 7. Short heavy bone is associated with short, bulging muscle. However, a short-legged, short-bodied lamb is more likely to reach market finish at a lighter weight than a longer muscled lamb with more scale. Pricing Slaughter Lambs at the Market The lamb buyer arrives at live lamb prices by starting with the price being received for carcasses, estimating quality grade and dressing percent, adding in by-product value and deducting the cost of processing. The variation in value per cwt. of live lambs is determined by the quality grade, dressing percent and discounts of overfat, wasty lambs. Quality Grades The quality grades of slaughter lambs are Prime, Choice, Good, and Utility. Quality grades are an estimate of the eating qualities of tenderness, juiciness and flavor. In the live lamb the amount of finish provides the estimate of. eating quality. The fatter lamb has more quality except that exce551ve finish is no advantage. Another factor used in determining quality grade is conforma- tion. A higher conformation grade means more muscling. The standards permit 6 increasing fatness to compensate for a deficiency in muscling. For example, "A carcass with quality of average choice may have a conformation grade of high good and be graded low Choice.“ Young lambs are more tender than old lambs. Therefore, the carcass quality standard permits young, milk fat, spring lambs to grade Choice with less finish than older lambs coming out of the feedlots at 7 months to a year of age. Thus, feedlot lambs must be fatter to grade choice than spring lambs. Lamb carcass quality grade is also based on flank streaking and flank fullness and firmness as well as conformation and maturity. Flank streaking is intra- muscular fat on the surfaces of the primary and secondary flank muscles. Flank streaking is usually more extensive in the secondary flank than in the primary flank muscles. ' ‘Flank fullness and firmness is generally assessed in the flank region of the carcass by using the hand to check fullness and firmness. Flank fullness and firmness is highly influenced by carcass fatness, thus the fattest lambs have the fullest—firmest flanks and very thin lambs have the thinnest-softest flanks. Official lamb carcass grading is voluntary. If retail store buyers want to purchase Choice carcasses, they request the meat packer to have the federal grader grade the carcasses. As a result, the official grades are determined only for the higher grading carcasses. Secondly, lamb feeders have difficulty in finding enough lambs to feed thus they purchase lambs for feeding that would grade lower if they were slaughtered. Should you aim for the Prime grades? Probably not, as usually Prime lambs bring $1.00-2.00 per cwt. more than Choice lambs. Prime lambs have to be somewhat fatter and they also require more shape or muscling. Light-muscled lambs will not grade Prime regardless of finish. By insuring that you market Choice lambs and they have the conformation, some of them will grade Prime as you keep sorting off those that are ready for market. Dressing Percent The most valuable product derived from the live lamb is the carcass. Therefore, lamb buyers will pay more for lambs with a higher dressing percent. The three factors with the greatest influence on dressing percent are: 1. The weight of the organs removed and the amount of fill (feed contents in the digestive tract). 2. The amount of finish. 3. The weight of the pelt. Fill Lambs loaded, hauled 25 to 50 miles, unloaded and weighed will shrink 3 to 4% in liveweight. Thinner lambs willshrink more. Additionalshrinkage occurs on longer hauls. The loss in weight due to emptying the digestive tract is really no loss. A shrunk lamb brings more dollars per cwt. than a lamb weighed directly out of the feed lot because it will have a higher dressing percent. Finish Fat lambs dress higher than thinner lambs. Prime lambs (shorn) average 54%, Choice lambs (shorn) 53%, and Good lambs (shorn) 50%. Wooled lambs will yield 3 to 5% less. Too much emphasis on dressing percent leads the buyer to encouraging the marketing of lambs up to 0.3 inch of fat. However, the fatter the carcass, the more fat trim and the lower the percentage of retail cuts. A lamb producer may also arrive at a decision as to how much finish by calcu- lating the feed cost to put on a pound of gain. Kansas State University measured this relationship by feeding crossbred ewe lambs and slaughtering them at various degrees of finish. Figure 4 is an interpretation of their data based on inches of external fat. Figure 4. The Relationship of Fatness to Feed Efficiency and Rate of Gain. 18 16 IIIIIIIIIIIIIIIIIIFIIIIIIIII 0.6 - ._. ‘ Peunds Daily of 14 1 ‘\ __L_ 0.5 gain . . \ | 1 feed f . 3 per 12 f - ‘\\.. 0.4 pounds paund " _ ‘“ of 10 I -gain i 3 l \ _|o.2 6 5 \\ 0,1 . "II"— 0.2 0.3 0.4 0.6 0.8 Inches of External Fat The Kansas State lambs varied little in feed efficiency up to 0.3 inch of external fat. Beyond that point the amount of feed to put on a pound of gain zoomed upwards and the daily gain of the lambs fell rapidly. But if feed is cheap relative to the price of lambs, it is enticing to keep putting on more white meat. Therefore, the lamb producer as well as the lamb buyer must remember that overfat lambs do not attract buyers of lamb chops. Height of Pelt A producer can consider improving dressing percent by reducing the weight of pelt. Clean fleeces weigh less than muddy, taggy fleeces. Also shorn lambs dress higher than wooled lambs. Five pounds of wool on a 100 pound lamb reduces the carcass yield by 5 percent. Lambs with No. 1 pelts most of the time sell for a higher price per cwt. than full-fleeced lambs. A No. l pelt has fibers that measure 1/2 to 1 inch in length. The 1/2 inch fiber is found on the belly where fleece length is always shorter. A lamb shorn around 40 days prior to market will produce a No. 1 pelt. A fine-fleeced lamb requires more time. Creep fed, milk fat lambs do not need to be shorn but older lambs could be shorn. Xield Grading With beef, yield grading must be used whenever carcasses are quality graded. Yield grading is based on the yield of boneless leg, loin, rack and shoulder trimmed of excess finish. It is related to the percentage of edible meat in the carcass which does not include excessive fat. It is related also to the percentage of retail cuts trimmed of extra fat. The yield grade of an ovine carcass is determined on the basis of the adjusted fat thickness over the ribeye muscle between the 12th and 13th ribs. As the amount of external fat increases, the percentage of retail cuts decreases. Each 0.05 inch change in adjusted fat thickness over the ribeye changes the yield grade by one-half of a grade. ...
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This note was uploaded on 10/18/2010 for the course APSC 4414 at Virginia Tech.

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Evaluation of Slaughter Lambs - EVALUATION OF SLAUGHTER...

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