PERFORMANCE AND CARCASS TRAITS OF DOCKED AND INTACT FAT-TAILED NAJDI LAMBS
M. A. Abouheif, M. S. Kraidees and R. A. Shatat
Animal Production Department, College of Agriculture, King Saud University, Riyadh 11451, Saudi Arabia
Summary
Twelve intact and 12 docked Najdi lambs of equal numbers of males and females were utilized in the experiment. All lambs were raised under similar conditions until they attained 40 kg shorn and shrunk body weight. Thereafter, lambs were individually fed ad libitum on a diet formulated to contain 11.20 MJ ME/kg and slaughtered after 60 days feeding period. The results showed that Najdi rams averaged 6.14 kg more total gain (p < .05), required 6.80 kg less feed (p <.05) per kg of gain and produced 3.2and 3.07 kg more (p< .05)carcass and salablecuts weights over the feedingperiod than comparable ewes. Body wall thickness and kidney and pelvic fat weight were greater (p <
-05) for ewes than for rams； dressing percent, longissimus area and fat thickness were not significantly influenced by sex of lambs. Docked lambs kept for 60 days on feed required 1.80 kg less feed (p <
.05) per kg of gain and produced 2.21 kg more (p <.05) salable wholesale cuts weight than intact lambs. Docking was not a significant source of variation for total gain, carcass weight, dressing percent, longissimus dorsi area, body wall thickness and fat thickness.
(Key Words : Docking, Fat-Tailed Lambs, Feeding Performance, Carcass Traits)
Introduction Materials and Methods
Local sheep of Saudi Arabia are fat-tailed and typical of those found in the range areas of the Middle East. Coop (1982) stated that some breeds of sheep which evolved in arid region are pr이le to the development of excessive fat tail.
Fat tail in Najdi sheep was accounted for 9.2%
of the cold carcass weight (Abouheif et al., 1988). However, the urgency of improving effici
ency of sheep production by reducing the total carcass fat necessitates production of sheep with minimal levels of trimmable fat (Berg and Butt
erfield, 1976). It is assumed that docking fat-tailed lambs early in life wo니d improve the efficiency of growth by eliminating the deposition of large amounts of fat in the tail and thus a greater fraction of the absorbed nutrients seem available for body gain. Therefore, this study was intended to investigate the effect of docking on feeding performance and carcass traits of male and female Najdi lambs.
'Address reprint requests to Dr. M. A. Abouheif, Animal Production Department, College of Agriculture, P. O.Box2460, King SaudUniversity, Riyadh 11451, Saudi Arabia.
Received April 18, 1992 Accepted November 14, 1992
Twenty four single Najdi lambs representing equal numbers of male and female were utilized in this experiment. Of those lambs, twelve (6 males and 6 females) were chosen at random and docked between the second and third caudal vertebrae before they were three days of age using the rubber-ring elastrator. Lambs were raised under similar environmental, nutritional and management conditions. Lambs had access to alfalfa hay and high-energy creep feed (18% crude protein and 12.54 MJ ME/kg) until they were weaned at approximately 8 weeks of age. After weaning, all lambs were fed together in one pen from self feeders. They received a diet formulated to contain 11.40 MJ ME/kg and consisted of 50% alfalfa hay and 50% commercial concentrate.
When the lambs averaged 40 kg shorn and shrunk body weight, they were then placed individually in pens; the diet fed during the first five days was gradually changed to the desired experimental diet. Thenafter, lambs were fed ad libitum on an experimental diet formulated to contain 11.2 MJ ME/kg and slaughtered after 60 days feeding period. Composition of diet used during feeding period is presented in table 1.
Initial and final shorn live body weights were
135 AJAS 1993 Vol. 6 (No. 1) 135-138
ABOUHEIF ET AL.
taken after a 16-hr shrink without feed. Individual feed consumption for each lamb during the 60 days feeding trial was recorded.
TABLE 1. COMPOSITION OF EXPERIMENTAL DIET
Ingredient % as dry
matter
Yellow corn 49
Alfalfa hay 20
Wheat Straw 14
Barley 10
Soybean meal 6
Dicalcium phosphate 0.5
Salt 0.5
Trace mineral premix® 0.02
Vitamin premixb 0.01
Crude protein, % MJ ME/kg
12.81 11.20 a Contained 10% Mn, 10% Fe, 10% Zn, 1% Cu, .3%I and .1% Co. Calcium carbonate used as carrier.
b Contained 30,000 JU vitamin A/gm, 6,000 IU vitamin D/gm and 7.5 IU vitamin E/gm.
The lambs were slaughtered at the university abattoir. Hot carcass weight 30 to 45 min after slaughter was recorded. Each carcass was allowed to chill for 36 hr at 10t!. The kidney and pelvic fat and the tail fat in the intact lambs were removed and their weights recorded. Thereafter, carcass was split down the center of the backbone into two sides, and the right side was ribbed between the 12th and 13th ribs. After ribbing, an acetate tracing was made of the longissimus dorsi muscle, and a planimeter was used to deteiinine the area. Fat thickness over the center
of the longissimus dorsi muscle, and body wall thickness (11 cm lateral to the midline between the 12th and 13th ribs) were also measured. Right side of the carcass was then fabricated into six standard wholesale cuts by the procedure described by Romans et al. (1985) and the total wholesale cuts weight (salable weight) was record
ed.
Feeding performance and carcass traits data were analyzed statistically by GLM, fixed-model procedures (SAS, 1986). The independent variables in the model included main effects of sex, docking treatment and 나leir two-way interactions. Initial shorn and shrunk body weight was included in the model as a continuous variate. Treatment means were separated by Duncan's multiple range test. In this experiment, all significant interactions were caused by a change in magnitude not a change in rank, thus we only considered the main effects.
Results and Discussion
Least squares means for feeding performance data are presented in table 2. Najdi rams aver
aged 6.14 kg more total gain (p < .05) during the 60 days feeding period than Najdi ewes.
Average daily gain and average daily dry matter intake also favored the Najdi rams. Rams grew faster (p < .05) and gained 103 g/day more than comparable ewes. Feed efficiency (kilograms dry matter feed required per kilogram body gain) greatly (p < .05) favored rams. In this regard, rams required 6.80 kg less feed per kilogram of gain than Najdi ewes. Disadvantages of ewes as compared with rams in growth rate and efficiency of growth have been established. Shelton and
TABLE 2. LEAST-SQUARES MEANS AND STANDARD ERRORS (SE) FOR PERFORMANCE DATA OF NAJDI LAMBS ADJUSTED TO 40 KG SHORN AND SHRUNK INITIAL BODY W티GHT
Trait - Sex Treatment
Ram Ewe Docked Intact SE
No. of lambs 12 12 12 12
Final wt. (kg) 50.06a 43.92b 47.17 46.81 .97
Daily gain (kg) 0.168& 0.065b 0.120 0.114 .02
Daily dry matter intake (kg) 1.393a 0.98 lb 1.112b 1.262a .07
Kg dry matter/kg gain 8.29b 15.09a 9.27b H.07a 1.88
a,b Means in the same row within aneffect, bearing different superscripts are different (p< .05),
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PERFORMANCE OF DOCKED AND INTACT LAMBS
Carpenter (1972), Crouse et al. (1978) and Dehaan et al. (1987) reported that average daily gain and gain-to-feed ratio were superior for rams than for ewes. This suggested that some of the sex differences in daily gain and efficiency of growth were attributable to sex hormones (Everitt and Jury, 1966). Another explanation for these sex differences is that ewe lambs are physiologically more mature than comparable ram lambs at 40 kg body weight. This weight corresponded to a degree of maturity in terms of size of approximately 68% and 54.5% of the weight of a mature ewe and ram, respectively (Abouheif, 1990). Therefore, ewe lambs seem that they approached close to the top of their growth curve and became a slow and less efficient grower (Butterfield et al.» 1983).
Docking treatment was not a significant source of variation for total gain during the 60 days feeding period. Daily dry matter intake, however, was higher (p < .05) for the intact Jambs than
for docked lambs. The feed efficiency significantly (p < .05) favored the docked lambs. Docked Iambs kept for 60 days on feed required 1.80 kg less feed per kilogram of body gain than those intact lambs. Abouheif et al. (1992) reported that docked lambs produced more lean weight in their carcasses than the comparable intact lambs.
Therefore, the superiority of docked lambs to consume less feed combined with their ability to grow more efficiently over the time on feeding probably could lead to the conclusion that dock
ing altered the partitioning of growing tissues in favor of lean.
Least squares means for carcass traits data are presented in table 3. Hot carcass weight and total wholesale cuts weight were greater (p <
.05) for rams than for ewes. The Najdi rams produced 3.2 kg and 3.07 kg more carcass and salable wholesale cuts weights, respectively, over the 60 days feeding period than comparable ewes.
Jacobs et al. (1972) and Shelton and Carpenter
TABLE 3. LEAST-SQUARES MEANS AND STANDARD ERRORS (SE) FOR CARCASS TRAITS DATA OF NAJDI LAMBS AS INFLUENCED BY SEX AND DOCKING TREATMENT
Trait Sex Treatment
Ram Ewe Docked Intact SE
No. observations 12 12 12 12
Hot carcass (kg) 26.97a 23.77b 25.83 24.90 .55
Dressing (%) 53.9 54.1 54.8 53.2 .78
Salable cuts (kg) 24.44a 21.37b 24.0 la 21.80b .51
Longissimus area (cm2) 13.37 13.29 13.71 12.96 .80
Body wall thickness (cm) 1.81b 2.09a 2.02 1.88 .12
Fat thickness (cm) 0.58 0.58 0.59 0.58 .10
Kidney and Pelvic fat (kg) 0.91b 1.63a 1.45a 1.09b .11
a,b Means in the samerow within an effect, bearing different superscript are different (p < .05).
(1972) reported that rams had higher carcass weight and carcass cutability than ewes. Also, body wall thickness and kidney and pelvic fat weight were greater (p < .05) for Najdi ewes than for rams; dressing percent, Jongissimus dorsi area and body fat thickness were not significantly influenced by sex of lambs. Oliver et al. (1967) found that differences in body wall thickness are due entirely to differences in fat deposits over the ribs. However, ewe lambs were generally fatter than rams when compared on the basis of fat thickness measurements and kidney and pelvic
fat which agrees with the reports of Carpenter et al. (1969) and Crouse et al. (1978). On the other hand, Field et al. (1967) and Carpenter et al. (1969) found an advantage in longissimus dorsi area for ram lambs over ewe lams.
Except for salable cuts weight and kidney and pelvic fat weight, all studied carcass traits data were not significantly influenced by docking treatment. In this regard, docked lambs produced 2.21 kg and 0.36 kg more (p < .05) wholesale cuts and kidney and pelvic fat weight, respectively, over the feeding period than comparable intact
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ABOUHEIF ET AL.
lambs. Abouheif et al, (1992) found that docking treatment had no effect on kidney and pelvic fat weight in lambs slaughtered at 40 kg body weight.
Therefore, the kidney and pelvic regions in docked lambs were a favorite sites of a large amount of fat deposition during the 60 days feeding period.
According to the remits and assuming that the current market price of Najdi wholesale carcass is 20 SR per kilogram and the cost of feeding is 0.5 SR per kilogram dry matter, the production of docked lambs will cost 4.5 SR less and earns 44.2 SR more than comparable intact lambs during the studied 60 days feeding period.
Literature Cited
Abouheif, M. A., A. A. Alsobayel and S. E. Mostafa.
1988. Distribution of lean, fat and bone in the carcasses of Najdi and Naeimi ram lambs、Arab Gulf J. Sci. Res., Agric. Biol. Sci. 6:21-29.
Abouheif, M. A. 1990. Environmental and genetic causes of variation in growth patterns of Najdi sheepfrom birth to maturity. J. King Saud Univ.
2:21-32.
Abouheif, M. A., M. S. Kraidees and R. A. Shatat.
1992. Effects of docking and sex of lambs on carcass characteristics of fat-tailed Najdi sheep.
J. Appl. Anim. Res. (accepted fbr publication).
Berg, R. T. and R. M. Butterfield. 1976. New Concepts of Cattle Growth. Univ. Sydney Press, Sydney, Australia.
Butterfield, R. M., D. A. Griffith, J. M. Thompson, J. Zamora and A. M. James. 1983. Changes in body composition relative to weight and maturity in large and small strains of Australian Merino rams. Anim. Prod. 36:29-37.
Carpenter, Z. L., G. T. King, M. Shelton and O. D.
Butler 1969. Indices for estimating cutability of wether, ram and ewe lambs carcasses. J. Anim.
Sci. 28:180-186.
Coop, 1. E. 1982. Sheep and Goat Production. World Anim. Sci., C 1, Elsevier Sci. Pub. Co., New York, USA.
Crouse, J. D., R. A. Field, J. L. Chant, C. L. Ferrell, G. M. Smith and V. L. Harrison. 1978. Effect of dietary energy intake on carcass composition and palatability of different weight carcasses from ewe and ram lambs. J. Anim.Sci. 47:1207-1217.
Dehaan, K. C., L. L. Berger, D. J. Kesler, F. K.
McKeith, D. L.Thomas and T. G.Nash. 1987.
Effect of prenatal androgenization on lamb per formance, carcass composition and reproductive function. J. Anim. Sci. 65:1465-1470.
Everitt, G. C. and K. E. Jury. 1966. Effects ofsex and gonadectomy on the growth and development of Southdown X Romney cross lambs. J. Agric. Sci.
66:15-27.
Field, R. A., M. L. Riley and M. P. Botkin. 1967.
Effect of sex and ram weight on composition of lambs. Proc. Western Sect. Ain. Soc. Anim. Sci.
18:45-47.
Jacobs, J. A・，R. A. Field, M. P. Botkin, M. L. Riley and G. P. Rochrkasse. 1972. Effects of weight and castration on lamb carcass composition and quality. J. Anim. Sci. 35:926-930.
Oliver, W. M.,乙 L. Carpenter, G. T. King and J.
M. Shelton. 1967. Qualitative and quantitative characteristics of ram, wether and ewe lambs carcasses. J. Anim. Sci., 26:307-310.
Romans, J. R., K. W. Jones, W. J. Cos⑹Jo, C. W.
Carlson and P. T. Ziegler. 1985. The Meat We Eat, The Interstate Printers & Publishers, Inc.
USA.
SAS. 1986. SAS User's Guide: Statistics, SAS Inst. Inc., Cary, NC, USA.
Shelton, M. and Z. L. Carpenter. 1972. Influence of sex, stilbesterol treatment and slaughter weight on performance and carcass traits of slaughter Jambs. J. Anim. Sci. 34:203-207.
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