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Carcass traits of Kheri lambs maintained on different system of feeding management
MEAT SCIENCE Meat Science 76 (2007) 395–401 www.elsevier.com/locate/meatsci
Carcass traits of Kheri lambs maintained on different system of feeding management S.A. Karim a
a,*
, Kuldeep Porwal
a,b
, Suresh Kumar a, V.K. Singh
a
Division of Animal Nutrition, Central Sheep and Wool Research Institute, Avikanagar 304 501, Rajasthan, India b P.O. Bhartana, District Etawah, UP, India Received 6 October 2005; received in revised form 17 March 2006; accepted 5 June 2006
Abstract The study was conducted on 6-month-old finisher lambs of the Kheri breed raised under extensive range management (G1), grazing with ad libitum concentrate supplementation (G2) or intensive feeding (G3) to assess dressing yield, cutability of standard cuts, composition of the carcass and the efficiency of mutton production from the three defined systems. The weaning weight of the lambs in the three groups was similar while the finishing weight, total body weight gain in the experiment, average daily gain and the percent feed conversion efficiency were higher (P < 0.01) in G2 and G3 than G1. The pre slaughter weight (PSW), empty live weight (ELW), hot carcass weight and hot carcass weight with edible offal was higher (P < 0.01) in G2 and G3 fed on a high plane of nutrition than G1 raised under extensive range management. The dressing percent in terms of live weight (LW) and empty live weight (ELW) was also higher in G2 and G3 than G1. The loin eye area as an index of muscle growth was also higher in G2 and G3 than G1. Although the weights of standard cuts were generally higher in G2 and G3 due to higher PSW, as proportions of half carcass they were similar in the three groups, except the rack cut, which was higher in G2 and G3. The cut proportions pooled for the three groups averaged 33.2%, 12.3%, 13.3%, 24.9% and 16.3% of half carcass for leg, loin, rack, neck and shoulder and breast and fore shank, respectively. The depot fat (Caul and kidney fat) accretion was higher in G2 and G3 than G1. The composition of the half carcass indicated that lean percent was higher (P < 0.01) in G1 and G2 than G3 while sub cutaneous and intra muscular fat content were generally higher (P < 0.01) in G2 and G3 and KOH bone percent was higher (P < 0.05) in G1 and G2 than G3. The results indicated that the growth performance was better, feed conversion efficiency, carcass yield and dressing percentage higher in lambs maintained under grazing with supplementation and intensive feeding than extensive range management. The carcass separable fat content was 8% under extensive range management while it was 12% and 16% in semi intensive and intensive system of feeding management indicating that the carcass was of acceptable quality. The loin eye area reflected the trends of pre slaughter weight and was higher in intensive and semi intensive than extensive range management. 2006 Elsevier Ltd. All rights reserved. Keywords: Carcass traits; Extensive; Feeding management; Intensive; Lambs; Semi intensive
1. Introduction Earlier sheep were reared for wool while presently mutton has replaced wool as the primary product of sheep in India. Moreover, it is also a fact that 70% of the value of a sheep is from its meat (Riyazuddin & Karim, 2001). India
*
Corresponding author. Tel.: +91 1437 28143; fax: +91 1437 28163. E-mail address: [email protected] (S.A. Karim).
0309-1740/$ - see front matter 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2006.06.008
has about 58 million sheep and 18.5 million are slaughtered annually. The average carcass weight of Indian sheep is 10 kg (Kondaiah & Agnihotri, 1995) hence 1850 m kg mutton is contributed to Agricultural Gross Domestic Production in the country and selling at Rs. 120/kg contributed and Rs. 222 trillion to GNP from meat alone. Carcass evaluation is essential in growth studies to determine the relative efficiency of the animals in converting feed to animal tissue. The slaughter traits, in turn, are modulated by heredity, feeding regimen and prevailing
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rearing environment. In practice different primal cuts do not fetch variable market prices therefore, the western concept of meat grading is not practiced. Consumers usually prefer meat with desired marbling, whereas once the fat content exceeds more than 20%; even Indian consumers do not like it. Moreover higher fat deposition reduces the feed conversion efficiency and increases the cost of feed input/kg gain in live weight and hence, is uneconomical (Karim, 2004). Dressing percentage is an important trait for carcass evaluation which is affected by age, sex, plane of nutrition and whether castrated or intact (Devendra & Burns, 1983). The dressing yield of 6-month-old animals was reported to range from 48% to 50% in shorn lambs (Karim, Santra, & Verma, 2002; Prasad, Charyulu, Shreenivas, Rao, & Munirathnam, 1991) while it ranged from 40% to 42% in unshorn sheep (Sen, Karim, & Santra, 2000a, 2000b). Cutability of standard cuts remained relatively constant in these studies with cut proportion ranging between 32–35%, 9–15%, 8–14%, 20–25% and 15–23% of half carcass, respectively, for leg, loin, rack, neck and shoulder and breast and fore shank (Karim, 2004). The native breed lambs in farmers field have a 50–60 g average daily gain (ADG) in active phases of growth (Kaushish, Rawat, & Sharma, 1990) whereas under organized feeding management such lambs have attained 170 g ADG (Karim & Rawat, 1996). Various systems of feeding management are practiced over the world whereas the dominant extensive range management and developed intensive and semi intensive system has practical relevance in India. Although the nutrient requirement for desirable carcass traits of growing lambs under improved system of feeding management have been studied extensively (CSWRI, 1998) such information on lambs under extensive range management and grazing with supplementation are scanty. The reported study was therefore undertaken on finisher lambs raised under either extensive range management, or grazing with ad libitum concentrate supplementation or intensive feeding to assess dressing yield, cutability of standard cuts, composition of the carcasses and the efficiency of meat production from the three systems of feeding management. 2. Materials and methods 2.1. Location and environmental variables The experiment was conducted at the Central Sheep and Wool Research Institute, Avikanagar, India located at 7228 0 E longitude and 2617 0 N latitude, 320 m above mean sea level. The climate of the region is typically semiarid with yearly mean minimum and maximum temperature of 8 C and 41 C, respectively, and 257 mm annual precipitation of which 93% is distributed between June and September and remaining 7% in form of short showers from January to March. The experiment was initiated towards the middle of October and continued till January 2003.
During the study period the ambient temperature and black globe temperature of experimental site at morning (0730 h) ranged from 4 C to 16 C (average 8.8 C) and 2.0–38.0 C (average 14.9 C) while corresponding temperature at peak hot period (1430 h) was 12.5–29.0 C (average 21.7 C) and 14–55 C (average 43.3 C). The relative humidity (RH) ranged from 57% to 94% (average 84%) at 0730 h and 57% to 88% (average 80%) at 1430 h. The sunshine ranged from 4.0 to 9.7 h/day with an average of 8.0 h/day. 2.2. Animals and management Sixty Kheri male weaner (3-months-old) lambs with an average body weight of 16.44 ± 0.442 kg were used for the study. The lambs were treated for internal and external parasites using Zycloz and vaccinated against Enterotoxemia and Sheep pox. One week after the lambs were acquired they were randomly divided in to three equal groups viz. extensive (G1), semi intensive (G2) and intensive (G3). The G1 and G2 were allowed 9 h of grazing (0800–1700 h) under supervision of a shepherd followed by herding in separate enclosures, as groups, in an open side dirt floored, asbestos roofed animal shed overnight while the G3 was maintained in the shed throughout the study period. During the study, all the lambs had access to clean drinking water twice daily, in the morning (0800 h) before taking the animals out for grazing/feed offer and in the after noon (1700 h), on their return from grazing area. 2.3. Feeds and feeding of the experimental lambs The G1 were grazed simulating the sheep farmer’s traditional management practices in the region while the G2 were grazed as per G1 but with ad libitum concentrate (Barley 62, mustard cake 18, groundnut cake 17, mineral mixture 2 and common salt 1 parts) supplementation. The G2 lambs after grazing as in G1 were segregated and housed in a separate enclosure during the night and offered the ad libitum concentrate. The G3 lambs were maintained on intensive feeding using a complete feed containing 60:40 concentrate (Barley 37, mustard cake 10, groundnut cake 10, mineral mixture 2 and common salt 1 parts with Vitablend 20 g/100 kg feed) and roughage (Lopped and dried Khejri ‘Prosopis cineraria’ leaves) in mash form. The complete feed was offered ad libitum (20% in excess of previous day’s intake) at 0800 h and the feed residue, if any, of the previous day was weighed next day morning and discarded before the fresh feed offer. Daily feed intake of the lambs was recorded throughout the experiment and percent feed conversion efficiency was calculated as: % Feed conversion efficiency ¼ Total BW gain in the experiment 100=Total feed consumed
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2.4. Slaughter and carcass evaluation After termination of the feeding experiment six each of 6- months-old finisher lambs from the three groups were shorn. The lambs were fasted for 18 h with free access to water prior to slaughter. Pre slaughter weights were recorded and the animals were slaughtered in the experimental abattoir by the Halal method. After slaughter, the head was removed at the atlanto-occipital joint and fore and hind feet were removed at the carpal and tarsal joints, respectively. The animals were partially skinned lying on their back on the floor then suspended by the hind leg (Achilles tendon) for further skinning. Carcass and noncarcass components were separated and weighed immediately after slaughter. Non-carcass component included head, skin, liver, lungs, heart, kidney, spleen, digestive tract, gall bladder, testes, caul fat and kidney fat. Weight of the ingesta (digestive content) was computed as the difference between full and empty digestive tract. After skinning and evisceration, the carcass was split into fore and hindquarters at the intersection of 12th and 13th vertebrae. The loin eye area (cm2) was measured by a planimeter on the cut surface of Longissimus dorsi muscle at the interface of 12th and 13th ribs on both side of the carcass. Thereafter, the carcass was split along the mid line and the left half was disjointed as per the ISI (1963) specification into standard cuts viz. leg, loin, rack, neck and shoulder and breast and fore shank and chilled overnight at 4 C in a refrigerator. Next day the chilled cuts were manually dissected into lean, bone, subcutaneous fat and inter muscular fat. The percent compositions of the cuts were calculated on the basis of chilled carcass weight. The dissected bone of each cut was then boiled separately for 1 h in 2% KOH solution and KOH bone weight was recorded. The Longissimus dorsi muscle, dissected lean and fat were sampled and subjected to chemical analysis (AOAC, 1995) to assess the effect of plane of nutrition on carcass accretion profile of the experimental animals. 3. Results and discussion 3.1. Growth and feed conversion efficiency The weaning weight of the lambs in the three groups was similar while the finishing weight, total body weight gain in
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the experiment and average daily gain was higher (P < 0.01) under G2 and G3 than G1 (Table 1). The percent feed conversion efficiency was also higher in G2 and G3 than G1. The results indicated that better plane of nutrition in G2 and G3 was reflected in their better growth rate and improved feed conversion efficiency. Both breed and production system can affect slaughter weight and traits (Kemp, Mahyuddin, Ely, Fox, & Moody, 1981) while increasing the slaughter weight can affect organoleptic characteristics of meat (Hawkins et al., 1985) as was observed in the present study. A positive relationship between live weight gain and dietary concentrate intake (as in semi intensive and intensive system of feeding management) was also reported by many workers (Murphy, Loerch, & Smith, 1994; Nachtomi, Halevi, Bruckental, & Amir, 1991; Santra & Pathak, 1999; Santra, Karim, & Chaturvedi, 2002). 3.2. Carcass characteristics The pre slaughter weight (PSW), empty live weight (ELW) and hot carcass weight and hot carcass weight with edible offal was higher (P < 0.01) in G2 and G3 fed on higher planes of nutrition than G1 (Table 2) which was a reflection of pre slaughter weight in these groups. The dressing percent in terms of live weight (LW) and empty live weight (ELW) was also higher in G2 and G3 than G1 due to the higher PSW as well as a better plane of nutrition. The average dressing percentages in terms of PSW (48.2%) and ELW (55.0%) were similar to earlier reports published for intensively fed lambs under different agro climatic conditions and feed combinations (Karim & Patnayak, 1998; Prasad et al., 1991; Singh, Sankhyan, & Prasad, 2004). The higher dressing yields in G2 and G3 than G1 was due to a higher level of feeding which agrees with the findings of Katiyar, Hasan, Ranjhan, and Bhat (1974), Krishnamohan and Charyalu (1983), and Sen, Karim, and Santra (2000b). The loin eye area as an index of muscle growth was also higher in G2 and G3 than G1. The higher loin area in G2 and G3 was due to their better plane of nutrition and higher PSW. Moreover, the published information indicated that the loin eye area linearly increased with increase in PSW and hence higher PSW of G2 and G3 was reflected in greater loin eye area. The loin eye area
Table 1 Growth performance of lambs maintained on different system of feeding management Attributes
Extensive (G1)
Semi intensive (G2)
Intensive (G3)
Pooled
Initial body weight (kg) Final body weight (kg) Total body weight gain (kg) Average daily gain (g) Total feed intake (kg) Percent feed efficiency
16.80 ± 0.802 23.34A ± 0.899 6.54A ± 0.486 72.6A ± 5.40 117.28A ± 4.605 5.64A ± 0.415
16.56 ± 0.892 31.04B ± 1.367 14.48C ± 0.947 160.9C ± 10.52 153.86B ± 6.898 9.43B ± 0.418
16.34 ± 0.738 28.57B ± 1.012 12.23B ± 0.676 135.9B ± 7.51 138.68B ± 5.356 8.91B ± 0.505
16.55 ± 0.462 27.90 ± 0.768 11.35 ± 0.611 126.1 ± 6.79 137.70 ± 3.845 8.14 ± 0.339
Means with unlike superscript in rows differ significantly (P < 0.01).
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Table 2 Carcass characteristics of finisher lambs Traits
G1
G2 A
G3 B
Pooled B
Pre slaughter weight (kg) Empty live weight (kg) Hot carcass weight (kg) Hot carcass weight with edible offal (kg) Edible offal weight (kg) Edible offal% on PSW Dressing% on LW Dressing% on ELW Half carcass cut weights (kg)
23.0 ± 0.84 19.3A ± 0.72 10.3A ± 0.38 11.4A ± 0.44 1.0A ± 0.08 4.4A ± 0.25 44.9A ± 0.99 53.6a ± 1.26 5.04A ± 0.17
29.7 ± 0.86 26.6B ± 0.94 14.5B ± 0.44 16.1B ± 0.50 1.6B ± 0.08 5.3B ± 0.17 48.8B ± 0.77 54.4ab ± 0.81 7.24B ± 0.29
28.0 ± 0.78 25.0B ± 0.76 14.3B ± 0.51 15.9B ± 0.51 1.6B ± 0.04 5.8B ± 0.24 50.9B ± 0.86 57.0b ± 0.46 6.97B ± 0.27
26.9 ± 0.82 23.7 ± 0.88 13.0 ± 0.52 14.4 ± 0.59 1.4 ± 0.08 5.2 ± 0.19 48.2 ± 0.56 55.0 ± 0.60 6.42 ± 0.27
Primary cuts (% of half cut weight) Leg Loin Rack Neck and shoulder Breast and fore shank Loin eye area (cm2)
34.1 ± 0.63 11.9 ± 0.09 12.6a ± 0.49 24.9 ± 0.57 16.6 ± 0.71 10.5A ± 0.52
33.3 ± 0.45 12.6 ± 0.38 12.9a ± 0.59 24.7 ± 0.51 16.4 ± 0.34 14.0B ± 0.29
32.3 ± 0.69 12.3 ± 0.38 14.5b ± 0.44 25.1 ± 0.72 15.8 ± 0.43 13.7B ± 0.61
33.2 ± 0.37 12.3 ± 0.19 13.3 ± 0.34 24.9 ± 0.33 16.3 ± 0.29 12.8 ± 0.47
0.39 ± 0.15 0.40A ± 0.09 4.12 ± 0.26 8.92 ± 0.17 6.86B ± 0.14 25.02B ± 0.88 15.97B ± 0.76 1.90B ± 0.09 0.46 ± 0.01 0.34 ± 0.01 0.51 ± 0.07 1.96 ± 0.05
0.54 ± 0.05 1.11B ± 0.11 4.65 ± 0.27 8.87 ± 0.35 6.31A ± 0.24 19.63A ± 0.95 10.54A ± 0.97 2.05B ± 0.08 0.45 ± 0.02 0.30 ± 0.02 0.53 ± 0.06 2.08 ± 0.08
0.69 ± 0.06 1.65C ± 0.13 4.68 ± 0.12 9.36 ± 0.24 6.32A ± 0.08 19.04A ± 1.22 10.65A ± 1.27 1.62A ± 0.05 0.47 ± 0.02 0.30 ± 0.01 0.72 ± 0.12 1.99 ± 0.04
0.54 ± 0.06 1.05 ± 0.14 4.49 ± 0.14 9.05 ± 0.15 6.50 ± 0.09 21.23 ± 0.86 12.39 ± 0.83 1.86 ± 0.06 0.46 ± 0.01 0.31 ± 0.01 0.59 ± 0.05 2.01 ± 0.03
Tissue weight (as % of pre slaughter weight) Kidney fat Caul fat Blood Skin Head GI tract Ingesta Liver Heart Kidney Testes Pluck
Means with unlike superscript in rows differ significantly; capital letter (P < 0.01) and small letter (P < 0.05).
recorded in present investigation was also within the range of earlier report (Karim et al., 2002; Sen et al., 2000b). Greater loin eye area in G2 than G1 observed in present investigation was similar to findings of Singh et al. (2004) in sheep maintained on grazing alone as well as grazing with progressively increased levels of concentrate supplementation. The pre-slaughter weight had a positive significant relationship with dressing% on pre slaughter weight (r = 0.49*), loin eye area (r = 0.87**), caul fat (r = 0.58*) and kidney fat (r = 0.51*). The pre slaughter weight was also positively related with total sub cutaneous fat (r = 0.63**) and total fat content of HCW indicating that irrespective of feeding regimen the lambs with higher pre slaughter weight invariably had higher carcass fat content. The fat content was, however, negatively related (r = 0.54*) with lean content of HCW (*P < 0.05; **P < 0.01). It was evident that animals with higher pre slaughter weight had undesirable tissue accretion in form of bone and fat hence the ideal slaughter weight has to be established for each breed for harvesting quality meat. However, under certain situations there are benefits in animals having a reasonable fat content to better resist physical stresses and a small increase in bone content is a small price to pay for a surviving sheep.
3.3. Cutability of standard cuts The cut weights of standard cuts were higher in G2 and G3, due to higher PSW, whereas in terms of cut proportions of half carcass they were similar in the three groups except rack cut, which was higher in G2 and G3 (Table 3). The cut proportions pooled for the three groups averaged 33.2%, 12.3%, 13.3%, 24.9% and 16.3% of the half carcass for leg, loin, rack, neck and shoulder and breast and fore shank, respectively. The proportions of standard cuts observed in the present investigation were within the range of earlier reports published for intensively fed lambs (Karim & Verma, 2001; Karim et al., 2002; Sen et al., 2000b; Sen, Karim, & Sharma, 2003). 3.4. Organ weights The GI tract and ingesta weights as a percentage of PSW were higher (P < 0.01) in G1 than G2 and G3 (Table 2). The lambs under G1 had access to only roughage with a low digestibility, which was reflected in the observed response. The caul fat weight, and caul fat as proportion of PSW were greater (P < 0.01) in G2 and G3 because of their greater weight resulting from higher plane of nutrition (Karim & Patnayak, 1998; Singh et al., 2004). Likewise the
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Table 3 Dissected lean, fat and bone contents of the standard cuts (%) Traits
G1
G2
G3
Pooled
Leg Lean Sub cutaneous fat Intra muscular fat KOH bone
69.22 ± 1.59 2.54a ± 0.20 2.41A ± 0.60 15.31 ± 1.10
68.93 ± 1.73 3.83ab ± 0.54 3.88A ± 0.47 13.67 ± 1.09
66.15 ± 1.16 4.78b ± 0.62 6.56B ± 0.64 12.90 ± 0.45
68.10 ± 0.89 3.72 ± 0.35 4.28 ± 0.52 13.96 ± 0.54
Loin Lean Sub cutaneous fat Intra muscular fat KOH bone
60.47 ± 1.50 13.11 ± 1.83 6.20A ± 1.83 10.33b ± 0.69
55.56 ± 2.65 13.88 ± 1.15 11.55B ± 1.88 9.21ab ± 0.95
53.27 ± 2.23 16.64 ± 2.50 13.32B ± 3.60 7.45a ± 0.31
56.43 ± 1.39 14.54 ± 1.10 10.36 ± 1.58 9.00 ± 0.476
Rack Lean Sub cutaneous fat Intra muscular fat KOH bone
57.57 ± 2.78 4.49 ± 0.32 3.12A ± 0.41 17.40 ± 1.78
56.97 ± 1.82 6.36 ± 0.80 6.04A ± 1.35 14.83 ± 1.02
56.18 ± 1.31 7.35 ± 1.87 11.03B ± 2.32 14.57 ± 0.95
56.90 ± 1.13 6.07 ± 0.71 6.73 ± 1.16 15.60 ± 0.77
Neck and shoulder Lean Sub cutaneous fat Intra muscular fat KOH bone
64.69 ± 1.71 3.34a ± 0.68 3.61 ± 0.42 15.03ab ± 0.60
61.18 ± 1.67 5.64ab ± 1.22 5.06 ± 0.62 16.43b ± 1.40
62.52 ± 1.89 7.06b ± 0.63 5.88 ± 0.93 12.19a ± 0.80
62.80 ± 0.91 5.35 ± 0.61 4.85 ± 0.44 14.55 ± 0.69
Breast and fore shank Lean Sub cutaneous fat Intra muscular fat KOH bone
56.01B ± 1.70 5.92 ± 0.65 5.57a ± 0.96 17.86b ± 0.63
57.09B ± 1.15 6.93 ± 1.49 4.37a ± 0.85 15.72ab ± 0.94
48.19A ± 1.52 9.28 ± 1.59 10.41b ± 2.53 13.46a ± 1.16
53.76 ± 1.25 7.38 ± 0.79 6.78 ± 1.09 15.68 ± 0.67
Composition of half car carcass Lean Sub cutaneous fat Intra muscular fat Total separable fat KOH bone
63.40B ± 0.730 4.77A ± 0.293 3.74A ± 0.418 8.52A ± 0.464 15.32b ± 0.726
61.85B ± 0.817 6.38B ± 0.476 5.46A ± 0.527 11.84B ± 0.953 14.24ab ± 0.810
59.34A ± 0.574 7.83C ± 0.573 8.47B ± 0.850 16.29C ± 1.245 12.34a ± 0.336
61.53 ± 0.562 6.33 ± 0.393 5.89 ± 0.583 12.22 ± 0.927 13.96 ± 0.465
Means with unlike superscript in rows differ significantly; capital letter (P < 0.01) and small letter (P < 0.05).
kidney fat weight as well as its expression as proportion of PSW was also higher in G2 and G3 than G1. Moreover, liver fat content increase enormously during short periods of feed deprivation, as in G1, resulting in higher liver weight as compared well fed animals. The liver weight expressed in term of PSW was greater (P < 0.01) in G1 and G2 than G3. The higher liver weight of the animal exposed to grazing on rangeland (G1 and G2) was possibly due to their wider choice of vegetation probably containing some deleterious factor, detoxification of which led to hyperplasia of liver tissue and higher weight. 3.5. Composition of half carcass Manual dissection of standard cuts indicated that lean percent of different primal cuts was similar except for breast and fore shank, wherein it was higher (P < 0.01) in G1 and G2 than G3 (Table 3). However, the composition of the half carcasses indicated that lean percent was higher (P < 0.01) in G1 and G2 than G3. The sub cutaneous and intra muscular fat were generally higher (P < 0.01) in G2 and G3 while KOH bone percent was higher
(P < 0.05) in G1 and G2 than G3. Borton, Loerch, McClure, and Wulf (2005) also observed higher fat content in concentrate fed lambs. The higher fat content in G2 and G3 was due to their better plane of nutrition. It is established that carcass fat content is influenced by carcass weight as well as plane of nutrition in tropical environment. The lambs under G2 and G3 had diets with 54:46 and 40:60 R:C while it was 100:00 R:C in G1 which was reflected in the observed differences. Prasad, Singh, and Bapna (1981) also observed that lambs fed ration with R:C 30:70 deposited more (27%) fat/kg feed consumed than lambs fed ration with R:C 50:50. Karim and Patnayak (1998) also reported a similar finding of lambs maintained on a high plane of nutrition. Composition of half carcass pooled for the primal cuts also indicated that in general, lean per cent was higher in G1 and G2 than G3 while total separable fat content was higher in G2, more so in G3 than G1. The KOH bone content followed a trend opposite to lean and fat content. Karim and Verma (2001) and Singh, Karim, Sankhyan, and Verma (2003) also reported higher fat content of half carcass in finisher lambs maintained under intensive feeding than animals under grazing with supplementation.
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Table 4 Chemical composition (%) of dissected meat, fat and Longissimus dorsi muscle lambs Traits
G1
G2
G3
Pooled
Dissected meat Dry matter Crude protein Ether extract Total ash
29.96 ± 0.87 82.81b ± 2.03 12.90A ± 2.05 4.30b ± 0.20
32.40 ± 0.78 69.51a ± 4.90 22.36B ± 2.22 3.63a ± 0.12
31.81 ± 0.88 72.26a ± 2.23 24.04B ± 2.36 3.70a ± 0.17
31.39 ± 0.52 74.86 ± 2.28 19.77 ± 1.69 3.88 ± 0.12
Dissected fat Dry matter Crude protein Ether extract Total ash
81.83A ± 1.59 6.27B ± 0.56 93.06A ± 0.58 0.67C ± 0.05
88.46B ± 2.01 4.30A ± 0.37 95.21B ± 0.38 0.49B ± 0.06
93.32C ± 0.75 3.28A ± 0.37 96.44B ± 0.40 0.29A ± 0.03
87.87 ± 1.42 4.62 ± 0.38 94.90 ± 0.42 0.48 ± 0.05
Longissimus dorsi muscle Dry matter Crude protein Ether extract Total ash
32.36A ± 0.65 84.06 ± 2.17 10.89a ± 2.13 5.05 ± 0.12
33.03A ± 0.84 78.01 ± 3.26 17.07b ± 3.17 4.92 ± 0.25
36.07B ± 0.80 76.66 ± 3.68 18.56b ± 3.78 4.78 ± 0.21
33.82 ± 0.57 79.58 ± 1.85 15.51 ± 1.87 4.92 ± 0.11
Means with unlike superscript in rows differ significantly; capital letter (P < 0.01) and small letter (P < 0.05).
Chemical analysis of dissected meat, fat and Longissimus dorsi muscle (as an index of carcass chemical composition) also indicated that crude protein (CP) and total ash content were higher (P < 0.05) in G1 than G2 and G3 while ether extract content followed a reverse trend. The dissected fat had 95% ether extract indicating that the manual dissection was effective in separating meat and fat (Table 4). The purchase price of weaner lambs was Rs. 40/kg live weight and the investment on this account was Rs. 672, 664 and 652/animal, respectively, in G1, G2 and G3. During the study period of 92 days other expenditure on account of grazing charge (Rs. 60/animal) and health coverage (Rs. 5/animal) was similar in G1 and G2 while in G2 additional expenditure was incurred in terms of cost of concentrate input (Rs. 276.23/animal). In G3 the cost of complete feed, labor charge and health coverage was Rs. 264, 20 and 5/animal, respectively. Accordingly the total expenditure for rearing lamb to marketable age was Rs. 737, 1005 and 941/animal, respectively, in G1, G2 and G3. The total receipt from disposal of finisher lambs through slaughter was higher (P < 0.01) in G2 (Rs. 2184) and G3 (Rs. 2176) than G1 (Rs. 1604) with net profit of Rs. 867, 1179 and 1235 in G1, G2 and G3, respectively. 4. Conclusion The results indicated that the carcass yield and dressing percentage were higher in lambs maintained under grazing with supplementation and intensive feeding than extensive range management. The carcass separable fat content was 8% under extensive range management while it was 12% and 16% in semi intensive and intensive system of management, indicating that the carcass was of acceptable quality. The loin eye area reflected the trends of pre- slaughter weight and was higher in intensive and semi intensive than extensive range management.
Acknowledgements The authors are grateful to the Director of the institute for providing facilities. Technical assistance rendered by Mr. Nassimuddin T-5 in slaughter is gratefully acknowledged. Financial support to Principal Investigator by Jaivigyan NATP project in conduct of the study is also acknowledged. References AOAC (1995). Official methods of analysis (16th ed.). Washington, DC: Association of Official Analytical Chemists. Borton, R. J., Loerch, S. C., McClure, K. E., & Wulf, D. M. (2005). Comparison of characteristics of lambs fed concentrate or grazed on ryegrass to traditional or heavy slaughter weights. I. Production, carcass, and organoleptic characteristics. Journal of Animal Science, 83, 679–685. CSWRI. (1998). 35 Years of Research, Central Sheep and Wool Research Institute, Avikanagar. Devendra, C., Burns, M. (1983). Goat Production in the Tropics (pp. 60) (Technical communication no. 19). Commonwealth Agricultural Bureaux. Farnham House, Farmham Royal Slough SL2 3BN, UK. Hawkins, R. R., Kemp, J. D., Ely, D. G., Fox, J. D., Moody, W. G., & Vimini, R. J. (1985). Carcass and meat characteristics of crossbred lambs born to ewes of different genetic types and slaughtered at different weights. Livestock Production Science, 12, 241–250. ISI (1963). Indian standard specifications for mutton and goat flesh. Fresh, chilled and frozen (IS 2536). New Delhi, India: Bureau of Indian Standard Institution. Karim, S. A., & Rawat, P. S. (1996). Growth performance of native and crossbred weaner lambs under intensive feeding. Indian Journal of Animal Sciences, 66, 830–832. Karim, S. A., & Patnayak, B. C. (1998). Carcass characteristics of finisher lambs raised on varying levels of energy under heat exposure. Indian Journal of Animal Sciences, 68, 276–278. Karim, S. A., & Verma, D. L. (2001). Growth performance and carcass characteristics of finisher lambs maintained on intensive feeding and grazing with supplementation. Indian Journal of Animal Sciences, 71, 959–961. Karim, S. A. (2004). Nutrition and feeding management of sheep for mutton production. In Proceedings of the national seminar on opportunities and challenges in nutrition and feeding management of sheep,
S.A. Karim et al. / Meat Science 76 (2007) 395–401 goat and rabbits for sustainable production (Lead paper, 10–12 February) (pp. 88–99). Avikanagar: Central Sheep and Wool Research Institute. Karim, S. A., Santra, A., & Verma, D. L. (2002). Growth, feed conversion efficiency and carcass characteristics of Malpura and Malpura · Awassi crossbred lambs in a hot semi arid environment. Asian-Australian Journal of Animal Science, 15, 377–381. Katiyar, R. C., Hasan, Q. Z., Ranjhan, S. K., & Bhat, P. N. (1974). Growth responses in Muzzafarnagri lambs on rations with varying energy concentration in relation to intensive mutton production. Indian Journal of Animal Sciences, 44, 683–691. Kemp, J. D., Mahyuddin, M., Ely, D. G., Fox, J. D., & Moody, W. G. (1981). Effect of feeding system, slaughter weight and sex on organoleptic properties and fatty acid composition of lamb. Journal of Animal Science, 51, 321–330. Kaushish, S. K., Rawat, P. S., & Sharma, S. C. (1990). Performance of native sheep (Malpura) and its crosses with Avikalin under semi arid condition. World Review of Animal Production, 25, 44–46. Kondaiah, N., & Agnihotri, M. K. (1995). Strategies for processing and marketing of meat from small ruminants. Proceedings of the third national seminar on Sheep and goat production and utilization (Lead paper, 8–10 April) (pp. 50–71). Avikanagar: Central Sheep and Wool Research Institute. Krishnamohan, D. V. G., & Charyalu, E. K. (1983). Growth, nutrient utilization and carcass characteristics in lambs fed rations having different proportions of concentrate to roughage. Indian Journal of Animal Sciences, 53, 1228–1232. Murphy, T. A., Loerch, S. C., & Smith, F. E. (1994). Effect of feeding high concentrate diet at restricted intakes on digestibility and nitrogen metabolism in growing lambs. Journal of Animal Science, 72, 1583–1590. Nachtomi, E. L., Halevi, A., Bruckental, I., & Amir, S. (1991). Energy protein intake and its effect on blood metabolism of high producing dairy cows. Canadian Journal of Animal Science, 71, 401–407. Prasad, R. D. D., Charyulu, E. K., Shreenivas, D., Rao, T. M., & Munirathnam, D. (1991). Carcass characteristics of Mandya, Nellore
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and their halfbred with Dorset under feedlot. Indian Journal of Animal Sciences, 61, 226–227. Prasad, V. S. S., Singh, R. N., & Bapna, D. L. (1981). Carcass composition of native and crossbred lambs maintained on two different rations. Indian Journal of Animal Genetics and Breeding, 3, 25–30. Riyazuddin & Karim, S. A. (2001). Economics of mutton/chevon production: the Indian scenario. Proceedings of the national seminar on scope and strategies for increasing meat production from small ruminants and rabbits in new millennium (Lead paper, 9–11 November) (pp. 106–110). Coimbatore, Tamil Nadu: Indian Society of Sheep Goat Production and Utilization. Santra, A., & Pathak, N. N. (1999). Nutrient utilization and compensatory growth in crossbred (Bosindicus · Bostaurus) calves. AsianAustralasian Journal of Animal Science, 8, 1285–1290. Santra, A., Karim, S. A., & Chaturvedi, O. H. (2002). Effect of concentrate supplementation on nutrient intake and performance of lambs of two genotypes grazing a semiarid rangeland. Small Ruminant Research, 44, 37–45. Sen, A. R., Karim, S. A., & Santra, A. (2000a). Effect of defaunation on carcass and meat characteristics of finisher lambs. Indian Journal of Animal Sciences, 70, 659–661. Sen, A. R., Karim, S. A., & Santra, A. (2000b). Carcass characteristics of finisher lambs maintained on grazing with supplementation. Indian Journal of Animal Sciences, 70, 988–990. Sen, A. R., Karim, S. A., & Sharma, R. C. (2003). Mutton production potential and meat quality traits of cross-bred wool strains. Indian Veterinary Journal, 80, 1149–1152. Singh, N. P., Karim, S. A., Sankhyan, S. K., & Verma, D. L. (2003). Carcass characteristics of finisher lambs maintained under intensive and semi intensive system of feeding. Indian Journal of Small Ruminant, 9, 142–143. Singh, N. P., Sankhyan, S. K., & Prasad, V. S. S. (2004). Effect of supplementary concentrate on growth and carcass characteristics in crossbred sheep of dual purpose. Indian Journal of Animal Sciences, 74, 73–76.
Carcass traits of Kheri lambs maintained on different system of feeding management S.A. Karim a
a,*
, Kuldeep Porwal
a,b
, Suresh Kumar a, V.K. Singh
a
Division of Animal Nutrition, Central Sheep and Wool Research Institute, Avikanagar 304 501, Rajasthan, India b P.O. Bhartana, District Etawah, UP, India Received 6 October 2005; received in revised form 17 March 2006; accepted 5 June 2006
Abstract The study was conducted on 6-month-old finisher lambs of the Kheri breed raised under extensive range management (G1), grazing with ad libitum concentrate supplementation (G2) or intensive feeding (G3) to assess dressing yield, cutability of standard cuts, composition of the carcass and the efficiency of mutton production from the three defined systems. The weaning weight of the lambs in the three groups was similar while the finishing weight, total body weight gain in the experiment, average daily gain and the percent feed conversion efficiency were higher (P < 0.01) in G2 and G3 than G1. The pre slaughter weight (PSW), empty live weight (ELW), hot carcass weight and hot carcass weight with edible offal was higher (P < 0.01) in G2 and G3 fed on a high plane of nutrition than G1 raised under extensive range management. The dressing percent in terms of live weight (LW) and empty live weight (ELW) was also higher in G2 and G3 than G1. The loin eye area as an index of muscle growth was also higher in G2 and G3 than G1. Although the weights of standard cuts were generally higher in G2 and G3 due to higher PSW, as proportions of half carcass they were similar in the three groups, except the rack cut, which was higher in G2 and G3. The cut proportions pooled for the three groups averaged 33.2%, 12.3%, 13.3%, 24.9% and 16.3% of half carcass for leg, loin, rack, neck and shoulder and breast and fore shank, respectively. The depot fat (Caul and kidney fat) accretion was higher in G2 and G3 than G1. The composition of the half carcass indicated that lean percent was higher (P < 0.01) in G1 and G2 than G3 while sub cutaneous and intra muscular fat content were generally higher (P < 0.01) in G2 and G3 and KOH bone percent was higher (P < 0.05) in G1 and G2 than G3. The results indicated that the growth performance was better, feed conversion efficiency, carcass yield and dressing percentage higher in lambs maintained under grazing with supplementation and intensive feeding than extensive range management. The carcass separable fat content was 8% under extensive range management while it was 12% and 16% in semi intensive and intensive system of feeding management indicating that the carcass was of acceptable quality. The loin eye area reflected the trends of pre slaughter weight and was higher in intensive and semi intensive than extensive range management. 2006 Elsevier Ltd. All rights reserved. Keywords: Carcass traits; Extensive; Feeding management; Intensive; Lambs; Semi intensive
1. Introduction Earlier sheep were reared for wool while presently mutton has replaced wool as the primary product of sheep in India. Moreover, it is also a fact that 70% of the value of a sheep is from its meat (Riyazuddin & Karim, 2001). India
*
Corresponding author. Tel.: +91 1437 28143; fax: +91 1437 28163. E-mail address: [email protected] (S.A. Karim).
0309-1740/$ - see front matter 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2006.06.008
has about 58 million sheep and 18.5 million are slaughtered annually. The average carcass weight of Indian sheep is 10 kg (Kondaiah & Agnihotri, 1995) hence 1850 m kg mutton is contributed to Agricultural Gross Domestic Production in the country and selling at Rs. 120/kg contributed and Rs. 222 trillion to GNP from meat alone. Carcass evaluation is essential in growth studies to determine the relative efficiency of the animals in converting feed to animal tissue. The slaughter traits, in turn, are modulated by heredity, feeding regimen and prevailing
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rearing environment. In practice different primal cuts do not fetch variable market prices therefore, the western concept of meat grading is not practiced. Consumers usually prefer meat with desired marbling, whereas once the fat content exceeds more than 20%; even Indian consumers do not like it. Moreover higher fat deposition reduces the feed conversion efficiency and increases the cost of feed input/kg gain in live weight and hence, is uneconomical (Karim, 2004). Dressing percentage is an important trait for carcass evaluation which is affected by age, sex, plane of nutrition and whether castrated or intact (Devendra & Burns, 1983). The dressing yield of 6-month-old animals was reported to range from 48% to 50% in shorn lambs (Karim, Santra, & Verma, 2002; Prasad, Charyulu, Shreenivas, Rao, & Munirathnam, 1991) while it ranged from 40% to 42% in unshorn sheep (Sen, Karim, & Santra, 2000a, 2000b). Cutability of standard cuts remained relatively constant in these studies with cut proportion ranging between 32–35%, 9–15%, 8–14%, 20–25% and 15–23% of half carcass, respectively, for leg, loin, rack, neck and shoulder and breast and fore shank (Karim, 2004). The native breed lambs in farmers field have a 50–60 g average daily gain (ADG) in active phases of growth (Kaushish, Rawat, & Sharma, 1990) whereas under organized feeding management such lambs have attained 170 g ADG (Karim & Rawat, 1996). Various systems of feeding management are practiced over the world whereas the dominant extensive range management and developed intensive and semi intensive system has practical relevance in India. Although the nutrient requirement for desirable carcass traits of growing lambs under improved system of feeding management have been studied extensively (CSWRI, 1998) such information on lambs under extensive range management and grazing with supplementation are scanty. The reported study was therefore undertaken on finisher lambs raised under either extensive range management, or grazing with ad libitum concentrate supplementation or intensive feeding to assess dressing yield, cutability of standard cuts, composition of the carcasses and the efficiency of meat production from the three systems of feeding management. 2. Materials and methods 2.1. Location and environmental variables The experiment was conducted at the Central Sheep and Wool Research Institute, Avikanagar, India located at 7228 0 E longitude and 2617 0 N latitude, 320 m above mean sea level. The climate of the region is typically semiarid with yearly mean minimum and maximum temperature of 8 C and 41 C, respectively, and 257 mm annual precipitation of which 93% is distributed between June and September and remaining 7% in form of short showers from January to March. The experiment was initiated towards the middle of October and continued till January 2003.
During the study period the ambient temperature and black globe temperature of experimental site at morning (0730 h) ranged from 4 C to 16 C (average 8.8 C) and 2.0–38.0 C (average 14.9 C) while corresponding temperature at peak hot period (1430 h) was 12.5–29.0 C (average 21.7 C) and 14–55 C (average 43.3 C). The relative humidity (RH) ranged from 57% to 94% (average 84%) at 0730 h and 57% to 88% (average 80%) at 1430 h. The sunshine ranged from 4.0 to 9.7 h/day with an average of 8.0 h/day. 2.2. Animals and management Sixty Kheri male weaner (3-months-old) lambs with an average body weight of 16.44 ± 0.442 kg were used for the study. The lambs were treated for internal and external parasites using Zycloz and vaccinated against Enterotoxemia and Sheep pox. One week after the lambs were acquired they were randomly divided in to three equal groups viz. extensive (G1), semi intensive (G2) and intensive (G3). The G1 and G2 were allowed 9 h of grazing (0800–1700 h) under supervision of a shepherd followed by herding in separate enclosures, as groups, in an open side dirt floored, asbestos roofed animal shed overnight while the G3 was maintained in the shed throughout the study period. During the study, all the lambs had access to clean drinking water twice daily, in the morning (0800 h) before taking the animals out for grazing/feed offer and in the after noon (1700 h), on their return from grazing area. 2.3. Feeds and feeding of the experimental lambs The G1 were grazed simulating the sheep farmer’s traditional management practices in the region while the G2 were grazed as per G1 but with ad libitum concentrate (Barley 62, mustard cake 18, groundnut cake 17, mineral mixture 2 and common salt 1 parts) supplementation. The G2 lambs after grazing as in G1 were segregated and housed in a separate enclosure during the night and offered the ad libitum concentrate. The G3 lambs were maintained on intensive feeding using a complete feed containing 60:40 concentrate (Barley 37, mustard cake 10, groundnut cake 10, mineral mixture 2 and common salt 1 parts with Vitablend 20 g/100 kg feed) and roughage (Lopped and dried Khejri ‘Prosopis cineraria’ leaves) in mash form. The complete feed was offered ad libitum (20% in excess of previous day’s intake) at 0800 h and the feed residue, if any, of the previous day was weighed next day morning and discarded before the fresh feed offer. Daily feed intake of the lambs was recorded throughout the experiment and percent feed conversion efficiency was calculated as: % Feed conversion efficiency ¼ Total BW gain in the experiment 100=Total feed consumed
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2.4. Slaughter and carcass evaluation After termination of the feeding experiment six each of 6- months-old finisher lambs from the three groups were shorn. The lambs were fasted for 18 h with free access to water prior to slaughter. Pre slaughter weights were recorded and the animals were slaughtered in the experimental abattoir by the Halal method. After slaughter, the head was removed at the atlanto-occipital joint and fore and hind feet were removed at the carpal and tarsal joints, respectively. The animals were partially skinned lying on their back on the floor then suspended by the hind leg (Achilles tendon) for further skinning. Carcass and noncarcass components were separated and weighed immediately after slaughter. Non-carcass component included head, skin, liver, lungs, heart, kidney, spleen, digestive tract, gall bladder, testes, caul fat and kidney fat. Weight of the ingesta (digestive content) was computed as the difference between full and empty digestive tract. After skinning and evisceration, the carcass was split into fore and hindquarters at the intersection of 12th and 13th vertebrae. The loin eye area (cm2) was measured by a planimeter on the cut surface of Longissimus dorsi muscle at the interface of 12th and 13th ribs on both side of the carcass. Thereafter, the carcass was split along the mid line and the left half was disjointed as per the ISI (1963) specification into standard cuts viz. leg, loin, rack, neck and shoulder and breast and fore shank and chilled overnight at 4 C in a refrigerator. Next day the chilled cuts were manually dissected into lean, bone, subcutaneous fat and inter muscular fat. The percent compositions of the cuts were calculated on the basis of chilled carcass weight. The dissected bone of each cut was then boiled separately for 1 h in 2% KOH solution and KOH bone weight was recorded. The Longissimus dorsi muscle, dissected lean and fat were sampled and subjected to chemical analysis (AOAC, 1995) to assess the effect of plane of nutrition on carcass accretion profile of the experimental animals. 3. Results and discussion 3.1. Growth and feed conversion efficiency The weaning weight of the lambs in the three groups was similar while the finishing weight, total body weight gain in
397
the experiment and average daily gain was higher (P < 0.01) under G2 and G3 than G1 (Table 1). The percent feed conversion efficiency was also higher in G2 and G3 than G1. The results indicated that better plane of nutrition in G2 and G3 was reflected in their better growth rate and improved feed conversion efficiency. Both breed and production system can affect slaughter weight and traits (Kemp, Mahyuddin, Ely, Fox, & Moody, 1981) while increasing the slaughter weight can affect organoleptic characteristics of meat (Hawkins et al., 1985) as was observed in the present study. A positive relationship between live weight gain and dietary concentrate intake (as in semi intensive and intensive system of feeding management) was also reported by many workers (Murphy, Loerch, & Smith, 1994; Nachtomi, Halevi, Bruckental, & Amir, 1991; Santra & Pathak, 1999; Santra, Karim, & Chaturvedi, 2002). 3.2. Carcass characteristics The pre slaughter weight (PSW), empty live weight (ELW) and hot carcass weight and hot carcass weight with edible offal was higher (P < 0.01) in G2 and G3 fed on higher planes of nutrition than G1 (Table 2) which was a reflection of pre slaughter weight in these groups. The dressing percent in terms of live weight (LW) and empty live weight (ELW) was also higher in G2 and G3 than G1 due to the higher PSW as well as a better plane of nutrition. The average dressing percentages in terms of PSW (48.2%) and ELW (55.0%) were similar to earlier reports published for intensively fed lambs under different agro climatic conditions and feed combinations (Karim & Patnayak, 1998; Prasad et al., 1991; Singh, Sankhyan, & Prasad, 2004). The higher dressing yields in G2 and G3 than G1 was due to a higher level of feeding which agrees with the findings of Katiyar, Hasan, Ranjhan, and Bhat (1974), Krishnamohan and Charyalu (1983), and Sen, Karim, and Santra (2000b). The loin eye area as an index of muscle growth was also higher in G2 and G3 than G1. The higher loin area in G2 and G3 was due to their better plane of nutrition and higher PSW. Moreover, the published information indicated that the loin eye area linearly increased with increase in PSW and hence higher PSW of G2 and G3 was reflected in greater loin eye area. The loin eye area
Table 1 Growth performance of lambs maintained on different system of feeding management Attributes
Extensive (G1)
Semi intensive (G2)
Intensive (G3)
Pooled
Initial body weight (kg) Final body weight (kg) Total body weight gain (kg) Average daily gain (g) Total feed intake (kg) Percent feed efficiency
16.80 ± 0.802 23.34A ± 0.899 6.54A ± 0.486 72.6A ± 5.40 117.28A ± 4.605 5.64A ± 0.415
16.56 ± 0.892 31.04B ± 1.367 14.48C ± 0.947 160.9C ± 10.52 153.86B ± 6.898 9.43B ± 0.418
16.34 ± 0.738 28.57B ± 1.012 12.23B ± 0.676 135.9B ± 7.51 138.68B ± 5.356 8.91B ± 0.505
16.55 ± 0.462 27.90 ± 0.768 11.35 ± 0.611 126.1 ± 6.79 137.70 ± 3.845 8.14 ± 0.339
Means with unlike superscript in rows differ significantly (P < 0.01).
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Table 2 Carcass characteristics of finisher lambs Traits
G1
G2 A
G3 B
Pooled B
Pre slaughter weight (kg) Empty live weight (kg) Hot carcass weight (kg) Hot carcass weight with edible offal (kg) Edible offal weight (kg) Edible offal% on PSW Dressing% on LW Dressing% on ELW Half carcass cut weights (kg)
23.0 ± 0.84 19.3A ± 0.72 10.3A ± 0.38 11.4A ± 0.44 1.0A ± 0.08 4.4A ± 0.25 44.9A ± 0.99 53.6a ± 1.26 5.04A ± 0.17
29.7 ± 0.86 26.6B ± 0.94 14.5B ± 0.44 16.1B ± 0.50 1.6B ± 0.08 5.3B ± 0.17 48.8B ± 0.77 54.4ab ± 0.81 7.24B ± 0.29
28.0 ± 0.78 25.0B ± 0.76 14.3B ± 0.51 15.9B ± 0.51 1.6B ± 0.04 5.8B ± 0.24 50.9B ± 0.86 57.0b ± 0.46 6.97B ± 0.27
26.9 ± 0.82 23.7 ± 0.88 13.0 ± 0.52 14.4 ± 0.59 1.4 ± 0.08 5.2 ± 0.19 48.2 ± 0.56 55.0 ± 0.60 6.42 ± 0.27
Primary cuts (% of half cut weight) Leg Loin Rack Neck and shoulder Breast and fore shank Loin eye area (cm2)
34.1 ± 0.63 11.9 ± 0.09 12.6a ± 0.49 24.9 ± 0.57 16.6 ± 0.71 10.5A ± 0.52
33.3 ± 0.45 12.6 ± 0.38 12.9a ± 0.59 24.7 ± 0.51 16.4 ± 0.34 14.0B ± 0.29
32.3 ± 0.69 12.3 ± 0.38 14.5b ± 0.44 25.1 ± 0.72 15.8 ± 0.43 13.7B ± 0.61
33.2 ± 0.37 12.3 ± 0.19 13.3 ± 0.34 24.9 ± 0.33 16.3 ± 0.29 12.8 ± 0.47
0.39 ± 0.15 0.40A ± 0.09 4.12 ± 0.26 8.92 ± 0.17 6.86B ± 0.14 25.02B ± 0.88 15.97B ± 0.76 1.90B ± 0.09 0.46 ± 0.01 0.34 ± 0.01 0.51 ± 0.07 1.96 ± 0.05
0.54 ± 0.05 1.11B ± 0.11 4.65 ± 0.27 8.87 ± 0.35 6.31A ± 0.24 19.63A ± 0.95 10.54A ± 0.97 2.05B ± 0.08 0.45 ± 0.02 0.30 ± 0.02 0.53 ± 0.06 2.08 ± 0.08
0.69 ± 0.06 1.65C ± 0.13 4.68 ± 0.12 9.36 ± 0.24 6.32A ± 0.08 19.04A ± 1.22 10.65A ± 1.27 1.62A ± 0.05 0.47 ± 0.02 0.30 ± 0.01 0.72 ± 0.12 1.99 ± 0.04
0.54 ± 0.06 1.05 ± 0.14 4.49 ± 0.14 9.05 ± 0.15 6.50 ± 0.09 21.23 ± 0.86 12.39 ± 0.83 1.86 ± 0.06 0.46 ± 0.01 0.31 ± 0.01 0.59 ± 0.05 2.01 ± 0.03
Tissue weight (as % of pre slaughter weight) Kidney fat Caul fat Blood Skin Head GI tract Ingesta Liver Heart Kidney Testes Pluck
Means with unlike superscript in rows differ significantly; capital letter (P < 0.01) and small letter (P < 0.05).
recorded in present investigation was also within the range of earlier report (Karim et al., 2002; Sen et al., 2000b). Greater loin eye area in G2 than G1 observed in present investigation was similar to findings of Singh et al. (2004) in sheep maintained on grazing alone as well as grazing with progressively increased levels of concentrate supplementation. The pre-slaughter weight had a positive significant relationship with dressing% on pre slaughter weight (r = 0.49*), loin eye area (r = 0.87**), caul fat (r = 0.58*) and kidney fat (r = 0.51*). The pre slaughter weight was also positively related with total sub cutaneous fat (r = 0.63**) and total fat content of HCW indicating that irrespective of feeding regimen the lambs with higher pre slaughter weight invariably had higher carcass fat content. The fat content was, however, negatively related (r = 0.54*) with lean content of HCW (*P < 0.05; **P < 0.01). It was evident that animals with higher pre slaughter weight had undesirable tissue accretion in form of bone and fat hence the ideal slaughter weight has to be established for each breed for harvesting quality meat. However, under certain situations there are benefits in animals having a reasonable fat content to better resist physical stresses and a small increase in bone content is a small price to pay for a surviving sheep.
3.3. Cutability of standard cuts The cut weights of standard cuts were higher in G2 and G3, due to higher PSW, whereas in terms of cut proportions of half carcass they were similar in the three groups except rack cut, which was higher in G2 and G3 (Table 3). The cut proportions pooled for the three groups averaged 33.2%, 12.3%, 13.3%, 24.9% and 16.3% of the half carcass for leg, loin, rack, neck and shoulder and breast and fore shank, respectively. The proportions of standard cuts observed in the present investigation were within the range of earlier reports published for intensively fed lambs (Karim & Verma, 2001; Karim et al., 2002; Sen et al., 2000b; Sen, Karim, & Sharma, 2003). 3.4. Organ weights The GI tract and ingesta weights as a percentage of PSW were higher (P < 0.01) in G1 than G2 and G3 (Table 2). The lambs under G1 had access to only roughage with a low digestibility, which was reflected in the observed response. The caul fat weight, and caul fat as proportion of PSW were greater (P < 0.01) in G2 and G3 because of their greater weight resulting from higher plane of nutrition (Karim & Patnayak, 1998; Singh et al., 2004). Likewise the
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Table 3 Dissected lean, fat and bone contents of the standard cuts (%) Traits
G1
G2
G3
Pooled
Leg Lean Sub cutaneous fat Intra muscular fat KOH bone
69.22 ± 1.59 2.54a ± 0.20 2.41A ± 0.60 15.31 ± 1.10
68.93 ± 1.73 3.83ab ± 0.54 3.88A ± 0.47 13.67 ± 1.09
66.15 ± 1.16 4.78b ± 0.62 6.56B ± 0.64 12.90 ± 0.45
68.10 ± 0.89 3.72 ± 0.35 4.28 ± 0.52 13.96 ± 0.54
Loin Lean Sub cutaneous fat Intra muscular fat KOH bone
60.47 ± 1.50 13.11 ± 1.83 6.20A ± 1.83 10.33b ± 0.69
55.56 ± 2.65 13.88 ± 1.15 11.55B ± 1.88 9.21ab ± 0.95
53.27 ± 2.23 16.64 ± 2.50 13.32B ± 3.60 7.45a ± 0.31
56.43 ± 1.39 14.54 ± 1.10 10.36 ± 1.58 9.00 ± 0.476
Rack Lean Sub cutaneous fat Intra muscular fat KOH bone
57.57 ± 2.78 4.49 ± 0.32 3.12A ± 0.41 17.40 ± 1.78
56.97 ± 1.82 6.36 ± 0.80 6.04A ± 1.35 14.83 ± 1.02
56.18 ± 1.31 7.35 ± 1.87 11.03B ± 2.32 14.57 ± 0.95
56.90 ± 1.13 6.07 ± 0.71 6.73 ± 1.16 15.60 ± 0.77
Neck and shoulder Lean Sub cutaneous fat Intra muscular fat KOH bone
64.69 ± 1.71 3.34a ± 0.68 3.61 ± 0.42 15.03ab ± 0.60
61.18 ± 1.67 5.64ab ± 1.22 5.06 ± 0.62 16.43b ± 1.40
62.52 ± 1.89 7.06b ± 0.63 5.88 ± 0.93 12.19a ± 0.80
62.80 ± 0.91 5.35 ± 0.61 4.85 ± 0.44 14.55 ± 0.69
Breast and fore shank Lean Sub cutaneous fat Intra muscular fat KOH bone
56.01B ± 1.70 5.92 ± 0.65 5.57a ± 0.96 17.86b ± 0.63
57.09B ± 1.15 6.93 ± 1.49 4.37a ± 0.85 15.72ab ± 0.94
48.19A ± 1.52 9.28 ± 1.59 10.41b ± 2.53 13.46a ± 1.16
53.76 ± 1.25 7.38 ± 0.79 6.78 ± 1.09 15.68 ± 0.67
Composition of half car carcass Lean Sub cutaneous fat Intra muscular fat Total separable fat KOH bone
63.40B ± 0.730 4.77A ± 0.293 3.74A ± 0.418 8.52A ± 0.464 15.32b ± 0.726
61.85B ± 0.817 6.38B ± 0.476 5.46A ± 0.527 11.84B ± 0.953 14.24ab ± 0.810
59.34A ± 0.574 7.83C ± 0.573 8.47B ± 0.850 16.29C ± 1.245 12.34a ± 0.336
61.53 ± 0.562 6.33 ± 0.393 5.89 ± 0.583 12.22 ± 0.927 13.96 ± 0.465
Means with unlike superscript in rows differ significantly; capital letter (P < 0.01) and small letter (P < 0.05).
kidney fat weight as well as its expression as proportion of PSW was also higher in G2 and G3 than G1. Moreover, liver fat content increase enormously during short periods of feed deprivation, as in G1, resulting in higher liver weight as compared well fed animals. The liver weight expressed in term of PSW was greater (P < 0.01) in G1 and G2 than G3. The higher liver weight of the animal exposed to grazing on rangeland (G1 and G2) was possibly due to their wider choice of vegetation probably containing some deleterious factor, detoxification of which led to hyperplasia of liver tissue and higher weight. 3.5. Composition of half carcass Manual dissection of standard cuts indicated that lean percent of different primal cuts was similar except for breast and fore shank, wherein it was higher (P < 0.01) in G1 and G2 than G3 (Table 3). However, the composition of the half carcasses indicated that lean percent was higher (P < 0.01) in G1 and G2 than G3. The sub cutaneous and intra muscular fat were generally higher (P < 0.01) in G2 and G3 while KOH bone percent was higher
(P < 0.05) in G1 and G2 than G3. Borton, Loerch, McClure, and Wulf (2005) also observed higher fat content in concentrate fed lambs. The higher fat content in G2 and G3 was due to their better plane of nutrition. It is established that carcass fat content is influenced by carcass weight as well as plane of nutrition in tropical environment. The lambs under G2 and G3 had diets with 54:46 and 40:60 R:C while it was 100:00 R:C in G1 which was reflected in the observed differences. Prasad, Singh, and Bapna (1981) also observed that lambs fed ration with R:C 30:70 deposited more (27%) fat/kg feed consumed than lambs fed ration with R:C 50:50. Karim and Patnayak (1998) also reported a similar finding of lambs maintained on a high plane of nutrition. Composition of half carcass pooled for the primal cuts also indicated that in general, lean per cent was higher in G1 and G2 than G3 while total separable fat content was higher in G2, more so in G3 than G1. The KOH bone content followed a trend opposite to lean and fat content. Karim and Verma (2001) and Singh, Karim, Sankhyan, and Verma (2003) also reported higher fat content of half carcass in finisher lambs maintained under intensive feeding than animals under grazing with supplementation.
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Table 4 Chemical composition (%) of dissected meat, fat and Longissimus dorsi muscle lambs Traits
G1
G2
G3
Pooled
Dissected meat Dry matter Crude protein Ether extract Total ash
29.96 ± 0.87 82.81b ± 2.03 12.90A ± 2.05 4.30b ± 0.20
32.40 ± 0.78 69.51a ± 4.90 22.36B ± 2.22 3.63a ± 0.12
31.81 ± 0.88 72.26a ± 2.23 24.04B ± 2.36 3.70a ± 0.17
31.39 ± 0.52 74.86 ± 2.28 19.77 ± 1.69 3.88 ± 0.12
Dissected fat Dry matter Crude protein Ether extract Total ash
81.83A ± 1.59 6.27B ± 0.56 93.06A ± 0.58 0.67C ± 0.05
88.46B ± 2.01 4.30A ± 0.37 95.21B ± 0.38 0.49B ± 0.06
93.32C ± 0.75 3.28A ± 0.37 96.44B ± 0.40 0.29A ± 0.03
87.87 ± 1.42 4.62 ± 0.38 94.90 ± 0.42 0.48 ± 0.05
Longissimus dorsi muscle Dry matter Crude protein Ether extract Total ash
32.36A ± 0.65 84.06 ± 2.17 10.89a ± 2.13 5.05 ± 0.12
33.03A ± 0.84 78.01 ± 3.26 17.07b ± 3.17 4.92 ± 0.25
36.07B ± 0.80 76.66 ± 3.68 18.56b ± 3.78 4.78 ± 0.21
33.82 ± 0.57 79.58 ± 1.85 15.51 ± 1.87 4.92 ± 0.11
Means with unlike superscript in rows differ significantly; capital letter (P < 0.01) and small letter (P < 0.05).
Chemical analysis of dissected meat, fat and Longissimus dorsi muscle (as an index of carcass chemical composition) also indicated that crude protein (CP) and total ash content were higher (P < 0.05) in G1 than G2 and G3 while ether extract content followed a reverse trend. The dissected fat had 95% ether extract indicating that the manual dissection was effective in separating meat and fat (Table 4). The purchase price of weaner lambs was Rs. 40/kg live weight and the investment on this account was Rs. 672, 664 and 652/animal, respectively, in G1, G2 and G3. During the study period of 92 days other expenditure on account of grazing charge (Rs. 60/animal) and health coverage (Rs. 5/animal) was similar in G1 and G2 while in G2 additional expenditure was incurred in terms of cost of concentrate input (Rs. 276.23/animal). In G3 the cost of complete feed, labor charge and health coverage was Rs. 264, 20 and 5/animal, respectively. Accordingly the total expenditure for rearing lamb to marketable age was Rs. 737, 1005 and 941/animal, respectively, in G1, G2 and G3. The total receipt from disposal of finisher lambs through slaughter was higher (P < 0.01) in G2 (Rs. 2184) and G3 (Rs. 2176) than G1 (Rs. 1604) with net profit of Rs. 867, 1179 and 1235 in G1, G2 and G3, respectively. 4. Conclusion The results indicated that the carcass yield and dressing percentage were higher in lambs maintained under grazing with supplementation and intensive feeding than extensive range management. The carcass separable fat content was 8% under extensive range management while it was 12% and 16% in semi intensive and intensive system of management, indicating that the carcass was of acceptable quality. The loin eye area reflected the trends of pre- slaughter weight and was higher in intensive and semi intensive than extensive range management.
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