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Growth and carcass characteristics of lambs in relation to plasma IGF-I and some histological traits of Longissimus lumbarum and Biceps femoris as affected by breed and age at slaughter
Livestock Science 124 (2009) 9–14
Contents lists available at ScienceDirect
Livestock Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / l i v s c i
Growth and carcass characteristics of lambs in relation to plasma IGF-I and some histological traits of Longissimus lumbarum and Biceps femoris as affected by breed and age at slaughter A.H. Barkawi a, Amal K. El-Asheeri a, Y.M. Hafez a,⁎, M.A. Ibrahim a, M.M. Ali b a b
Animal Production Department, Faculty of Agriculture, Cairo University, Giza, Egypt Academy of Scientific Research and Technology, Cairo, Egypt
a r t i c l e
i n f o
Article history: Received 29 January 2008 Received in revised form 26 July 2008 Accepted 25 August 2008 Keywords: Lambs Rahmani Ossimi Age at slaughter Chemical characteristics IGF-I Skeletal muscles and histological traits
a b s t r a c t Ten male lambs of each of Rahmani (R) and Ossimi (O) were used to study the growth and carcass characteristics within their first year of age (360 days). After suckling period (4 months), lambs were fed on the regular ration. During the course of the experiment, body weight (BW) was recorded monthly accompanied by blood sampling to determine IGF-I. Four lambs from each breed were slaughtered at 270 and 360 days of age, and Longissimus lumbarum (L. lumbarum) at the 9th, 10th and 11th ribs and Biceps femoris (B. femoris) muscles were separated to be used for chemical analysis and histological study. Breed had no effect on the growth curve of the two studied breeds. Chemical analysis indicated that (O) had higher fat (0.9%, P b 0.0001) and lower (0.3%, P b 0.01) moisture compared to (R), with no difference in protein and ash contents. The concentration of IGF-I was almost similar in both breeds up to day 270 of age, and then it was higher in (R). Number of fibers per bundle was higher (P b 0.05) in (O) than in (R) by 6.1%, while, the other histological traits were similar in the two studied breeds. Chemical analysis indicated that lambs slaughtered at 360 days of age had lower (0.7%, P b 0.0006) moisture and higher fat (17.3%, P b 0.0001) compared to day 270. Up to day 270 of age, IGF-I concentration was b500 ng/ml before increasing to N500 ng/ml up to the end of the experiment. No effect of age was observed on the studied histological traits. L. lumbarum muscle contained higher protein (4.2%, P b 0.0001), fat (104%, P b 0.0001) and ash (10%, P b 0.001), while moisture was less (5.6%, P b 0.0001) compared to B. femoris muscle. B. femoris muscle was higher (P b 0.0001) in number and diameter of fibers, bundle and stroma sectional areas relative to L. lumbarum by 38.2, 78.8, 53.2 and 23.8%, respectively. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Growth is a complicated process influenced mainly by age (Hassan and El-Feel, 1991), sex (Aboul-Naga et al., 1980), genotype (Aboul-Naga et al., 1980; Hassan, 1993), level of feeding (Awadalla et al., 1997), and castration process of males (Darwish et al., 1973), these are in addition to the levels of metabolic hormones. Muscle development is an output of the rate of protein synthesis and degradation as controlled by IGF-I action (Gatford ⁎ Corresponding author. E-mail address: [email protected] (Y.M. Hafez). 1871-1413/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2008.08.018
et al., 1996; Oksbjerg et al., 2004). IGF-I is involved in postnatal growth (McGuire et al., 1992), through mediating the anabolic actions of growth hormone (Jones and Clemmons, 1995; Liu and LeRoith, 1999). Also, it increases muscle mass via its action on muscle hypertrophy (Beermann et al., 1987; Mathison et al., 1998) and stimulating muscle cells uptake of amino acids, and protein synthesis (Shimizu et al., 1986). Hence, determination of plasma IGF-I concentration in growing lambs may provide a physiological interpretation of growth feature (Medrano and Bradford, 1991; Gatford et al., 1996, 1997; Whisnant et al., 1997). Studying growth feature in relation to some physiological measures may have a particular importance for understanding factors controlling muscle growth,
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thus modifying carcass composition through increasing the rate of lean tissue deposition (Wolf et al., 2001). Egyptian sheep were slaughtered usually around 12 months of age (pubertal age, Karam, 1957; Hamdon et al., 2006) when a considerable change in carcass (Lawrence and Fowler, 1998) and chemical composition of meat (Hassan and El-Feel, 1991; Hassan, 1993; Awadalla et al., 1997) occurs. Rahmani and Ossimi are native fat tailed breeds reared mainly in the north of Egypt. These breeds represent the majority of sheep population and consequently the main source of mutton. Many trials were conducted to describe growth performance and chemical composition of meat of these two breeds either from birth to weaning (Swidan et al., 1979; Aboul-Naga et al., 1980) or from 6 to 12 months of age (Hassan and El-Feel, 1991; Awadalla et al., 1997). However, no data are available describing their growth curve over their first year of age. In the light of the previous facts, the objectives of the present study were to; a) describe the growth features of Rahmani and Ossimi lambs in relation to plasma IGF-I concentration and the histological characteristics some skeletal muscles, and b) determine the effect of age at slaughter on the physical and chemical characteristics of the meat. 2. Materials and methods This study was carried out on two equal groups of Rahmani and Ossimi male lambs (n = 10 each), which were born between October and November 2004. Lambs were kept with their dams for four months post-lambing (suckling period) and afterward they were kept free in semi-shaded open yards. Lambs were fed according to their live body weight (NRC, 1985) on concentrate feed mixture in addition to the Egyptian clover (Trifolium alexandrinum) from October to April or its hay from May to September. Drinking water and mineral blocks were made available all the daytime. Body weight (BW) was recorded every 30 days (±3 d) starting from birth. Lambs were prevented to suckle their dams or prevented from feeding 12 h before weighing. After weighing 5 ml blood samples were collected in heparinized tubes from the jugular vein to determine IGF-I. Blood samples
were centrifuged at 3000 rpm for 20 min and the harvested plasma was kept at − 20 °C till the time of hormonal assay. The concentration of IGF-I was assessed by RIA technique using ready-coated tube kit (Bio-Source Europe, Nivelles, Belgium), with intra- and inter-assay coefficients were 9.2 and 5.6%, respectively. The standard curve ranged from 0.0 to 5000 ng IGF-1/ml. Cross-reaction of the IGF-I antibody was reported by the manufacturer to be 100% for IGF-I, 0.7% for IGF-II, and b0.1% for insulin and growth hormones. At 270 and 360 days of age, four lambs per age per breed were chosen randomly to be slaughtered at the experimental abattoir of Faculty of Agriculture, Cairo University, Giza, Egypt, after 18 h of fasting. Lambs were weighed (kg) then slaughtered using a sharp knife by cutting the jugular veins with no stunning. After complete bleeding, carcass was skinned and eviscerated before weighing and afterward it was sectioned down through the vertebral column to right and left sides. The Longissimus lumbarum (L. lumbarum) at the 9th, 10th and 11th ribs (rib cut) as representing carcass composition and Biceps femoris (B. femoris) as representing high price cut in sheep (Wolf et al., 2001) muscles were separated from the right side of the carcass to be used for chemical analysis (AOAC, 2000) and histological study. Area (cm2) of the fresh sections of L. lumbarum muscle (between the 8th and 9th ribs) was recorded by a planimeter before separating rib cut into lean, fat and bone. The monthly BW was used to draw the growth curve from birth to 360 days old. The growth curve was divided into three phases: P I, from birth to weaning (120 days), P II, from weaning to the expected age of puberty (240 days, Karam, 1957) and P III, from expected age at puberty to 360 days. Dressing percentage was calculated as the hot carcass weight divided by the BW at slaughter multiplied by 100. The histological sections were prepared according to Bancroft et al. (1996) and stained by Haematoxylin and Eosin solutions (5%). Slides were examined microscopically (×100) and digitally photographed. Two digital photocopies were taken, the first of the tissue section in three replicates, and the second of the Haemocytometer. By Auto Cad® (2004) software all histological measures (n = 470 ± 20) were calculated using two layers of digital photos; the digital image of the
Fig. 1. The growth curve of Rahmani and Ossimi lambs during the first year of age.
A.H. Barkawi et al. / Livestock Science 124 (2009) 9–14
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Table 1 Slaughter weight, dressing percentage, average daily gain and physical components of the 9th, 10th and 11th ribs (rib cut) and area of L. lumbarum as affected by breed and age at slaughter. Traits
Breed Rahmani
Slaughter wt (kg) Dressing (%) Average daily gain (g) Boneless meat (%) Rib cut (g) Lean (%) Fat (%) Bone (%) L. lumbarum area (cm2)
P value Ossimi
31.4 ± 2.3 49.1 ± 1.0
46.0 ± 2.6 49.8 ± 1.0
68.6 ± 1.2 372.5 ± 28.6 57.1 ± 1.3 11.5 ± 1.3 31. 4 ± 1.2 19.1 ± 1.5
71.2 ± 1.2 288.9 ± 28.6 53.9 ± 1.3 17.4 ± 1.3 28. 8 ± 1.2 17.5 ± 1.5
0.14 0.06 0.12 0.01 0.14 0.44
66.6 ± 1.1 252.3 ± 26.5 59.2 ± 1.2 7.4 ± 1.2 33.4 ± 1.1 17.3 ± 1.4
73.2 ± 1.2 409.1 ± 30.6 51.7 ± 1.4 21.5 ± 1.3 26.8 ± 1.2 19.3 ± 1.6
Yijk = μ + xi + aj + mk + ðxamÞijk + eijkl where: experimental observation, overall mean, effect of breed (i, 1 = Rahmani, 2 = Ossimi), age at slaughter (j, 1 = 270 days, 2 = 360 days), effect of type of muscle (k, 1 = L. lumbarum, 2 = B. femoris) interaction effects, between breed, age and muscle type, random error.
The interactions between breed and age, breed and type of muscle and age and type of muscle were insignificant. Model (2) for physical components of rib cut, and body weight at slaughter: Yijk = μ + xi + aj + ðxaÞij + eijk where: Yij µ xi
360
0.26 0.42
Data of physical components of the rib cut and chemical composition were analyzed using the General Linear Model (GLM) procedure (SAS, 2000). Differences between means were assessed by t test. Data in percentages were transformed to the arcsine square-root to normalize variance before analysis, using the following models (repeated measures): Model (1) for the chemical analysis and histological traits
eijkl
270
36.6 ± 2.4 50.0 ± 1.1
1. Fiber diameter (µm)= Fiber diameter (µm) (1st layer) × 0.2 divided by the corresponding area (µm) (2nd layer) 2. Bundle cross-sectioned area (mm2)=Bundle area (µm2)× 0.04 divided by the corresponding area (µm2) (2nd layer) multiplied by 10− 6.
xamijk
P value
40.8 ± 2.4 48.9 ± 0.9
muscle section as first layer and the second was a transparent digital image of the Haemocytometer slide area. The dimension of each square in the Haemocytometer slide (0.2 × 0.2 mm) was used as a standard to measure the histological traits (number of muscle fibers/bundle, fibers diameter, bundle cross-sectional area, and bundle:stroma ratio) according to Ashmore et al. (1974) using the following equations:
Yij µ xi aj mk
Age (day)
experimental observation, overall mean, effect of breed (i, 1 = Rahmani, 2 = Ossimi),
aj (xa)ij eijk
0.001 0.62 0.002 0.003 0.002 0.0001 0.002 0.34
age at slaughter (j, 1 = 270 days, 2 = 360 days), interaction effects, random error.
3. Results 3.1. Growth, carcass and chemical characteristics 3.1.1. Growth curve Growth curve of Rahmani and Ossimi lambs during the experimental period (360 days) had a curvilinear shape and it was similar in both breeds. The growth curve during P I and P II had a concave shape, before having a linear one up to the end of P III (Fig. 1). 3.1.2. Carcass characteristics and physical components of rib cut Except fat percentage out of the rib cut, which was higher (P b 0.01) in Ossimi than in Rahmani, breed had no effect on slaughter weight, dressing percentage and the other physical components of the rib cut (Table 1). On the other hand, age affected significantly all the traits shown in Table 1 except the area of L. lumbarum, however, it was larger at 360 days of age by 11.6%. 3.1.3. Chemical composition of meat Ossimi had higher (P b 0.0001) fat and lower (P b 0.01) moisture percentages compared to Rahmani. Lambs slaughtered at 360 days of age had lower (P b 0.0006) moisture and higher
Table 2 Chemical composition (%) of lambs as affected by breed, age and type of muscle based on the fresh matter. Effect
Moisture
Protein
Fat
Ash
Breed Rahmani Ossimi P value
75.7 ± 0.2 75.2 ± 0.2 0.01
18.7 ± 0.1 18.9 ± 0.1 0.25
3.3 ± 0.1 4.2 ± 0.1 0.0001
1.1 ± 0.0 1.1 ± 0.0
Age (days) 270 360 P value
75.8 ± 0.1 75.1 ± 0.2 0.0006
18.9 ± 0.1 18.6 ± 0.1 0.11
3.3 ± 0.1 4.2 ± 0.1 0.0001
1.1 ± 0.0 1.1 ± 0.0
Type of muscle L. lumbarum B. femoris P value
74.5 ± 0.1 78.9 ± 0.1 0.0001
19.4 ± 0.1 18.2 ± 0.1 0.0001
5.1 ± 0.1 2.5 ± 0.1 0.0001
1.1 ± 0.0 1.0 ± 0.0 0.0001
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Fig. 2. Concentration (ng/ml) of IGF-1 in blood plasma of Rahmani and Ossimi lambs affected by age.
Fig. 3. Histological sections of two types of skeletal muscles in two sheep breeds.
A.H. Barkawi et al. / Livestock Science 124 (2009) 9–14
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Table 3 Histological parameters of lamb muscles as affected by breed, age at slaughter and type of muscle. Effect
No of fibers/bundle
Fiber diameter (µm)
Bundle area (Mm2)
Stroma area (mm2)
Bundle: stroma area
Breed Rahmani Ossimi P value
63.6 ± 1.4 67.5 ± 1.3 0.05
75.3 ± 2.2 78.2 ± 2.2 0.35
0.188 ± 0.80 0.191 ± .79 0.81
0.023 ± .04 0.024 ± .04 0.73
8.2:1 8.0:1 0.23
Age (day) 270 360 P value
65.4 ± 1.3 65.6 ± 1.5 0.91
75.4 ± 2.0 78.1 ± 2.3 0.38
0.189 ± .74 0.191 ± .85 0.85
0.024 ± .03 0.023 ± .04 0.47
7.9:1 8.3:1 0.21
Type of muscle L. lumbarum B. femoris P value
55.0 ± 1.4 76.0 ± 1.4 0.0001
55.1 ± 2.2 98.5 ± 2.2 0.0001
0.171 ± .80 0.262 ± .80 0.0001
0.021 ± .04 0.026 ± .04 0.0001
8.0:1 10:1 0.0001
(P b 0.0001) fat percentages compared to those slaughtered at day 270 of age (Table 2). Ash and protein contents were neither affected by breed nor by age at slaughter. L. lumbarum muscle contained higher percentages of protein (P b 0.0001), fat (P b 0.0001) and ash (P b 0.001), while moisture was less (P b 0.0001) compared to B. femoris muscle. The high content of fat in L. lumbarum is most probably due to the high content in intramuscular fat. 3.2. Concentration of IGF-I IGF-I concentration was almost similar in both breeds throughout the experimental period. During P I and P II of the growth curve, IGF-I concentration fluctuated within a range of b500 ng/ml. At the beginning of P III, IGF-I concentration increased to N500 ng/ml, with a temporary drop at day 300 of age. The concentration of plasma IGF-I in Rahmani was relatively higher than that in Ossimi within P III (Fig. 2). 3.3. Histological traits The lean meat incorporates several skeletal muscles; each is composed, mainly, of muscle fibers. These fibers are gathered in adjacent bundles, the Fascicles, (F, Fig. 3) of different sizes. Each bundle is surrounded by connective tissue, the Perimesium (P, Fig. 3). These connective tissue septa furnish the stroma which connects the muscular tissue in compact structure. Fig. 3 shows cross-sections in lean meat of L. lumbarum and B. femoris of Rahmani and Ossimi lambs at 270 and 360 days of age. It is clear in Fig. 3 that L. lumbarum has thinner fibers, with no distinct breed differences, in accordance with Table 3. Number of fibers per bundle was higher (P b 0.05) in Ossimi than in Rahmani lambs. Meanwhile, fiber diameter, bundle area, stroma area and bundle:stroma area are similar in the two studied breeds. Age at slaughter has no effect on all the studied histological traits. On the other hand, type of muscle had significant effects on all the studied traits, which was less (P b 0.05) in L. lumbarum muscle compared to B. femoris (Table 3). Number of fibers/bundle, fiber diameter and bundle cross-sectional area was increased by 38.2, 78.8 and 53.2% in B. femoris compared to L. lumbarum, respectively.
4. Discussion The obtained results indicated that the growth curve, weight at slaughter and carcass traits of these two breeds (Fig. 1 and Table 1) of Rahmani and Ossimi lambs are similar under sheep production systems of Egypt. The transformation of growth curve from concave shape to liner one during P II and P III may be due to the greatest relative growth rate (Lawrence and Fowler, 1998) during these two phases. The obtained concentration of IGF-I during P I and P II (105–300 ng/ml) in the two breeds is close to that reported by Medrano and Bradford (1991). The noticeable increase in IGF-I concentration during P III is due to approaching adulthood of the lambs (Jones and Clemmons, 1995; Oksbjerg et al., 2004) as reported by Hamdon et al. (2006). Low separable fat (P b 0.0001) in Rahmani rib cut (Table 1) and low inter-muscular fat (Table 2); as determined by chemical analysis; may be due to that Rahmani is late mature breed relative to Ossimi (Ashmawy, 1985). This gives Rahmani meat an advantage from the consumer's point of view. The increase in fiber diameter in Ossimi than in Rahmani (Table 3) may be due to the accumulation of the protein (Carpenter et al., 1996), which resulted in an increase in protein content in Ossimi meat however, insignificant (Table 2). Increase (P b 0.001) in slaughter weight and increase in boneless meat (P b 0.002) indicated that slaughtering lambs at 360 days of age resulted more meat relative to age of 270 days (Table 1). The decrease (P b 0.002) in lean and an increase (P b 0.0001) in fat percentages (Table 1) of lambs slaughtered at 360 days of age indicated the nutritive quality of lambs slaughtered at 270 days. This suggestion is supported by the lower (P b 0.0001) fat and higher (P b 0.001) protein contents of meat by 3 and 3.5%, respectively (Table 2). The increase in fiber diameter and bundle area with age progress may be attributed to the increase in IGF-I between days 270 and 360 of age, which acts on muscle hypertrophy (Mathison et al., 1998) and increase protein synthesis (Shimizu et al., 1986). The comparison between L. lumbarum and B. femoris muscles indicated the good nutritive quality of L. lumbarum. This is shown by the better judgmental chemical characteristics of L. lumbarum than B. femoris, low moisture and higher (P b 0.0001) contents of protein and fat (Table 2). Histological
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study supports this suggestion through the thinner fiber diameter, the lower stroma area and bundle:stroma ratio (Table 3). This conclusion comes in agreement with the findings of Carpenter et al. (1996) who reported that lamb muscles histology is closely related to the chemical characteristics of these muscles. References Aboul-Naga, A.M., Afifi, E.A., El-Shobokshy, A.S.,1980. Early weaning of Rahmani, Ossimi and Barki local lambs. Egyptian Journal Animal Production 20 (2), 137–146. AOAC, 2000. Official Method of Analysis 17th ED Association of Official Analytical Chemists International. Maryland, USA. Ashmawy, G., 1985. Sheep and Goat Production (in Arabic). Madani Press, Cairo, Egypt. Ashmore, C.R., Parker, W., Stokes, H., Doerr, L., 1974. Comparative aspects of muscle fiber type in fetuses of normal and double muscle cattle. Growth 38, 501 Auto cad® 2004. License ACD-2004-0F-42600. Auto cad® 2004. License ACD-2004-0F-42600. Awadalla, I.M., Mohamed, M.I., Ibrahim, M.A.M., Amal, El Asheeri K., 1997. Efficiency of using groundnut hay in rations of Rahmani lambs. Egyptian Journal Animal Production 34 (2), 125–134. Bancroft, J.A., Stevens, A., Turner, D.R., 1996. Theory and practice of histological techniques, Chapter 6 by Alan Steven and Ian Eilson Pearson Professional limited, 4th ed. Churchill Livingstone, NY, USA. Beermann, D.H., Butler, W.R., Hogue, D.E., Fishell, V.K., Dalrymple, R.H., Ricks, C.A., Scanes, C.G., 1987. Cimaterol induced muscle hypertrophy and altered endocrine status in lambs. Journal of Animal Science 65, 1514–1524. Carpenter, C.E., Rice, O.D., Cockett, N.E., Snowder, G.D., 1996. Histology and composition of muscles from normal and callipyge lambs. Journal of Animal Science 74, 388–393. Darwish, M.Y.H., El-Samman, S., Abou-Hussein, E.R.M., 1973. Meat production from Rahmai lambs. Egyptian Journal Animal Production 13 (1), 35–48. Gatford, K.L., Fletcher, T.P., Clarke, I.J., Owens, P.C., Guinn, K.J., Walton, P.E., Grant, P.A., Hosking, B.J., Egan, A.R., Ponnampalam, E.N., 1996. Sexual dimorphism of circulating somatotropin, insulin-like growth factor I and II, insulin-like growth factor binding protein and insulin: relationship to growth rate and carcass characteristics in growing lambs. Journal of Animal Science 74, 1314–1325. Gatford, K.L., Guinn, K.J., Walton, P.E., Grant, P.A., Hosking, B.J., Egan, E.R., Owens, P.C., 1997. Ontogenic and nutritional changes in circulating Insulin-like growth factor (IGF)-I and IGF-II and IGF-binding protein in growing ewe and ram lambs. Journal of Endocrinology 155, 47–54.
Hamdon, H., Abd El Ati, M.N., Zenhom, M., Allam, F., 2006. Reproductive development of Farafra and Chios lambs in south Egypt. Egyptian Journal of Animal Production 43, 53–63 Supplemental Issue. Hassan, H.A., 1993. The effect of crossing Chios rams with Ossimi and Saidi ewes on growth performance and viability of lambs. Egyptian Journal of Animal Production 30 (1), 39–53. Hassan, H.A., El-Feel, F.M.R., 1991. The effect of breed, level of feeding, age and slaughter weight on performance and carcass traits of lambs. Egyptian Journal of Animal Production, 28 (2), 225-168. Jones, J.I., Clemmons, D.R., 1995. Insulin like growth factor and their binding proteins: biological action. Endocrinology Review 16, 33–39. Karam, H.A., 1957. Multiple birth sex ratio in Rahmani sheep. Journal Animal Science, 16, 990. Lawrence, T.L.H., Fowler, V.R., 1998. Growth of Farm Animals, 2nd edition. CAB International, UK. Chapter 6. Liu, J.L., LeRoith, D., 1999. Insulin-like growth factor I is essential for postnatal growth in response to growth hormone. Endocrinology, 140, 5178–5184. Mathison, B.D., Mathison, B.A., McNamara, J.P., Dodson, M.V., 1998. Insulinlike growth factor I receptor analysis of satellite cell-derived myotube membranes established from two lines of Targhee ram selected for growth rate. Domestic Animal Endocrinology 6, 191–201. McGuire, M.A., Bauman, D.E., Miller, M.A., Hartnell, G.F., 1992. Response of somatomedins (IGF-I and IGF-11) in lactating cows to variations in dietary energy and protein and treatment with recombinant n-methiony l bovine somatotropin. Journal of Nutrition 122:128. Medrano, J.F., Bradford, G.E., 1991. Growth performance and plasma insulin like growth factor 1 concentration in sheep selected for high weaning weight. Journal of Animal Science 69, 1991-1918. NRC, 1985. Nutrient Requirement of Sheep. National Research Council. 6th National Academy Press, Washington D. C., USA. Oksbjerg, N., Gondret, F., Vestergaard, M., 2004. Basic principle of muscle development and growth in meat-producing mammals as affected by the insulin-like growth factor (IGF) system. Domestic Animal Endocrinology 27, 219–240. SAS, 2000. SAS Users Guide. Version 6.12. SAS Institute, Cary. NC, USA. Shimizu, M., Webster, C., Morgan, D.O., Blau, H.M., Roth, R.A., 1986. Insulin and insulin-like growth factor receptors and responses in cultured human muscle cells. American Journal of Physiology 251, 611–615. Swidan, F., Aboul-Naga, A.M., El-Shobokshy, A.S., Abbas, A.M.,1979. Performance of Rahmani male-lambs weaned at six or eight weeks of age. Egyptian Journal Animal Production 19 (2), 159–168. Whisnant, C.S., Kline, R.S., Branum, J.C., Zaunbrecher, G.M., Khan, M.Z., Jackson, S.P., 1997. Hormonal profile of callipyge and normal sheep. Journal of Animal Science 76, 1443–1447. Wolf, B.T., Jones, D.A., Owen, M.G., 2001. Carcass composition, conformation and muscularity in Texel lambs of different breeding history, sex and leg sheep score. Animal Science 72, 465–n475.
Contents lists available at ScienceDirect
Livestock Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / l i v s c i
Growth and carcass characteristics of lambs in relation to plasma IGF-I and some histological traits of Longissimus lumbarum and Biceps femoris as affected by breed and age at slaughter A.H. Barkawi a, Amal K. El-Asheeri a, Y.M. Hafez a,⁎, M.A. Ibrahim a, M.M. Ali b a b
Animal Production Department, Faculty of Agriculture, Cairo University, Giza, Egypt Academy of Scientific Research and Technology, Cairo, Egypt
a r t i c l e
i n f o
Article history: Received 29 January 2008 Received in revised form 26 July 2008 Accepted 25 August 2008 Keywords: Lambs Rahmani Ossimi Age at slaughter Chemical characteristics IGF-I Skeletal muscles and histological traits
a b s t r a c t Ten male lambs of each of Rahmani (R) and Ossimi (O) were used to study the growth and carcass characteristics within their first year of age (360 days). After suckling period (4 months), lambs were fed on the regular ration. During the course of the experiment, body weight (BW) was recorded monthly accompanied by blood sampling to determine IGF-I. Four lambs from each breed were slaughtered at 270 and 360 days of age, and Longissimus lumbarum (L. lumbarum) at the 9th, 10th and 11th ribs and Biceps femoris (B. femoris) muscles were separated to be used for chemical analysis and histological study. Breed had no effect on the growth curve of the two studied breeds. Chemical analysis indicated that (O) had higher fat (0.9%, P b 0.0001) and lower (0.3%, P b 0.01) moisture compared to (R), with no difference in protein and ash contents. The concentration of IGF-I was almost similar in both breeds up to day 270 of age, and then it was higher in (R). Number of fibers per bundle was higher (P b 0.05) in (O) than in (R) by 6.1%, while, the other histological traits were similar in the two studied breeds. Chemical analysis indicated that lambs slaughtered at 360 days of age had lower (0.7%, P b 0.0006) moisture and higher fat (17.3%, P b 0.0001) compared to day 270. Up to day 270 of age, IGF-I concentration was b500 ng/ml before increasing to N500 ng/ml up to the end of the experiment. No effect of age was observed on the studied histological traits. L. lumbarum muscle contained higher protein (4.2%, P b 0.0001), fat (104%, P b 0.0001) and ash (10%, P b 0.001), while moisture was less (5.6%, P b 0.0001) compared to B. femoris muscle. B. femoris muscle was higher (P b 0.0001) in number and diameter of fibers, bundle and stroma sectional areas relative to L. lumbarum by 38.2, 78.8, 53.2 and 23.8%, respectively. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Growth is a complicated process influenced mainly by age (Hassan and El-Feel, 1991), sex (Aboul-Naga et al., 1980), genotype (Aboul-Naga et al., 1980; Hassan, 1993), level of feeding (Awadalla et al., 1997), and castration process of males (Darwish et al., 1973), these are in addition to the levels of metabolic hormones. Muscle development is an output of the rate of protein synthesis and degradation as controlled by IGF-I action (Gatford ⁎ Corresponding author. E-mail address: [email protected] (Y.M. Hafez). 1871-1413/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2008.08.018
et al., 1996; Oksbjerg et al., 2004). IGF-I is involved in postnatal growth (McGuire et al., 1992), through mediating the anabolic actions of growth hormone (Jones and Clemmons, 1995; Liu and LeRoith, 1999). Also, it increases muscle mass via its action on muscle hypertrophy (Beermann et al., 1987; Mathison et al., 1998) and stimulating muscle cells uptake of amino acids, and protein synthesis (Shimizu et al., 1986). Hence, determination of plasma IGF-I concentration in growing lambs may provide a physiological interpretation of growth feature (Medrano and Bradford, 1991; Gatford et al., 1996, 1997; Whisnant et al., 1997). Studying growth feature in relation to some physiological measures may have a particular importance for understanding factors controlling muscle growth,
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thus modifying carcass composition through increasing the rate of lean tissue deposition (Wolf et al., 2001). Egyptian sheep were slaughtered usually around 12 months of age (pubertal age, Karam, 1957; Hamdon et al., 2006) when a considerable change in carcass (Lawrence and Fowler, 1998) and chemical composition of meat (Hassan and El-Feel, 1991; Hassan, 1993; Awadalla et al., 1997) occurs. Rahmani and Ossimi are native fat tailed breeds reared mainly in the north of Egypt. These breeds represent the majority of sheep population and consequently the main source of mutton. Many trials were conducted to describe growth performance and chemical composition of meat of these two breeds either from birth to weaning (Swidan et al., 1979; Aboul-Naga et al., 1980) or from 6 to 12 months of age (Hassan and El-Feel, 1991; Awadalla et al., 1997). However, no data are available describing their growth curve over their first year of age. In the light of the previous facts, the objectives of the present study were to; a) describe the growth features of Rahmani and Ossimi lambs in relation to plasma IGF-I concentration and the histological characteristics some skeletal muscles, and b) determine the effect of age at slaughter on the physical and chemical characteristics of the meat. 2. Materials and methods This study was carried out on two equal groups of Rahmani and Ossimi male lambs (n = 10 each), which were born between October and November 2004. Lambs were kept with their dams for four months post-lambing (suckling period) and afterward they were kept free in semi-shaded open yards. Lambs were fed according to their live body weight (NRC, 1985) on concentrate feed mixture in addition to the Egyptian clover (Trifolium alexandrinum) from October to April or its hay from May to September. Drinking water and mineral blocks were made available all the daytime. Body weight (BW) was recorded every 30 days (±3 d) starting from birth. Lambs were prevented to suckle their dams or prevented from feeding 12 h before weighing. After weighing 5 ml blood samples were collected in heparinized tubes from the jugular vein to determine IGF-I. Blood samples
were centrifuged at 3000 rpm for 20 min and the harvested plasma was kept at − 20 °C till the time of hormonal assay. The concentration of IGF-I was assessed by RIA technique using ready-coated tube kit (Bio-Source Europe, Nivelles, Belgium), with intra- and inter-assay coefficients were 9.2 and 5.6%, respectively. The standard curve ranged from 0.0 to 5000 ng IGF-1/ml. Cross-reaction of the IGF-I antibody was reported by the manufacturer to be 100% for IGF-I, 0.7% for IGF-II, and b0.1% for insulin and growth hormones. At 270 and 360 days of age, four lambs per age per breed were chosen randomly to be slaughtered at the experimental abattoir of Faculty of Agriculture, Cairo University, Giza, Egypt, after 18 h of fasting. Lambs were weighed (kg) then slaughtered using a sharp knife by cutting the jugular veins with no stunning. After complete bleeding, carcass was skinned and eviscerated before weighing and afterward it was sectioned down through the vertebral column to right and left sides. The Longissimus lumbarum (L. lumbarum) at the 9th, 10th and 11th ribs (rib cut) as representing carcass composition and Biceps femoris (B. femoris) as representing high price cut in sheep (Wolf et al., 2001) muscles were separated from the right side of the carcass to be used for chemical analysis (AOAC, 2000) and histological study. Area (cm2) of the fresh sections of L. lumbarum muscle (between the 8th and 9th ribs) was recorded by a planimeter before separating rib cut into lean, fat and bone. The monthly BW was used to draw the growth curve from birth to 360 days old. The growth curve was divided into three phases: P I, from birth to weaning (120 days), P II, from weaning to the expected age of puberty (240 days, Karam, 1957) and P III, from expected age at puberty to 360 days. Dressing percentage was calculated as the hot carcass weight divided by the BW at slaughter multiplied by 100. The histological sections were prepared according to Bancroft et al. (1996) and stained by Haematoxylin and Eosin solutions (5%). Slides were examined microscopically (×100) and digitally photographed. Two digital photocopies were taken, the first of the tissue section in three replicates, and the second of the Haemocytometer. By Auto Cad® (2004) software all histological measures (n = 470 ± 20) were calculated using two layers of digital photos; the digital image of the
Fig. 1. The growth curve of Rahmani and Ossimi lambs during the first year of age.
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Table 1 Slaughter weight, dressing percentage, average daily gain and physical components of the 9th, 10th and 11th ribs (rib cut) and area of L. lumbarum as affected by breed and age at slaughter. Traits
Breed Rahmani
Slaughter wt (kg) Dressing (%) Average daily gain (g) Boneless meat (%) Rib cut (g) Lean (%) Fat (%) Bone (%) L. lumbarum area (cm2)
P value Ossimi
31.4 ± 2.3 49.1 ± 1.0
46.0 ± 2.6 49.8 ± 1.0
68.6 ± 1.2 372.5 ± 28.6 57.1 ± 1.3 11.5 ± 1.3 31. 4 ± 1.2 19.1 ± 1.5
71.2 ± 1.2 288.9 ± 28.6 53.9 ± 1.3 17.4 ± 1.3 28. 8 ± 1.2 17.5 ± 1.5
0.14 0.06 0.12 0.01 0.14 0.44
66.6 ± 1.1 252.3 ± 26.5 59.2 ± 1.2 7.4 ± 1.2 33.4 ± 1.1 17.3 ± 1.4
73.2 ± 1.2 409.1 ± 30.6 51.7 ± 1.4 21.5 ± 1.3 26.8 ± 1.2 19.3 ± 1.6
Yijk = μ + xi + aj + mk + ðxamÞijk + eijkl where: experimental observation, overall mean, effect of breed (i, 1 = Rahmani, 2 = Ossimi), age at slaughter (j, 1 = 270 days, 2 = 360 days), effect of type of muscle (k, 1 = L. lumbarum, 2 = B. femoris) interaction effects, between breed, age and muscle type, random error.
The interactions between breed and age, breed and type of muscle and age and type of muscle were insignificant. Model (2) for physical components of rib cut, and body weight at slaughter: Yijk = μ + xi + aj + ðxaÞij + eijk where: Yij µ xi
360
0.26 0.42
Data of physical components of the rib cut and chemical composition were analyzed using the General Linear Model (GLM) procedure (SAS, 2000). Differences between means were assessed by t test. Data in percentages were transformed to the arcsine square-root to normalize variance before analysis, using the following models (repeated measures): Model (1) for the chemical analysis and histological traits
eijkl
270
36.6 ± 2.4 50.0 ± 1.1
1. Fiber diameter (µm)= Fiber diameter (µm) (1st layer) × 0.2 divided by the corresponding area (µm) (2nd layer) 2. Bundle cross-sectioned area (mm2)=Bundle area (µm2)× 0.04 divided by the corresponding area (µm2) (2nd layer) multiplied by 10− 6.
xamijk
P value
40.8 ± 2.4 48.9 ± 0.9
muscle section as first layer and the second was a transparent digital image of the Haemocytometer slide area. The dimension of each square in the Haemocytometer slide (0.2 × 0.2 mm) was used as a standard to measure the histological traits (number of muscle fibers/bundle, fibers diameter, bundle cross-sectional area, and bundle:stroma ratio) according to Ashmore et al. (1974) using the following equations:
Yij µ xi aj mk
Age (day)
experimental observation, overall mean, effect of breed (i, 1 = Rahmani, 2 = Ossimi),
aj (xa)ij eijk
0.001 0.62 0.002 0.003 0.002 0.0001 0.002 0.34
age at slaughter (j, 1 = 270 days, 2 = 360 days), interaction effects, random error.
3. Results 3.1. Growth, carcass and chemical characteristics 3.1.1. Growth curve Growth curve of Rahmani and Ossimi lambs during the experimental period (360 days) had a curvilinear shape and it was similar in both breeds. The growth curve during P I and P II had a concave shape, before having a linear one up to the end of P III (Fig. 1). 3.1.2. Carcass characteristics and physical components of rib cut Except fat percentage out of the rib cut, which was higher (P b 0.01) in Ossimi than in Rahmani, breed had no effect on slaughter weight, dressing percentage and the other physical components of the rib cut (Table 1). On the other hand, age affected significantly all the traits shown in Table 1 except the area of L. lumbarum, however, it was larger at 360 days of age by 11.6%. 3.1.3. Chemical composition of meat Ossimi had higher (P b 0.0001) fat and lower (P b 0.01) moisture percentages compared to Rahmani. Lambs slaughtered at 360 days of age had lower (P b 0.0006) moisture and higher
Table 2 Chemical composition (%) of lambs as affected by breed, age and type of muscle based on the fresh matter. Effect
Moisture
Protein
Fat
Ash
Breed Rahmani Ossimi P value
75.7 ± 0.2 75.2 ± 0.2 0.01
18.7 ± 0.1 18.9 ± 0.1 0.25
3.3 ± 0.1 4.2 ± 0.1 0.0001
1.1 ± 0.0 1.1 ± 0.0
Age (days) 270 360 P value
75.8 ± 0.1 75.1 ± 0.2 0.0006
18.9 ± 0.1 18.6 ± 0.1 0.11
3.3 ± 0.1 4.2 ± 0.1 0.0001
1.1 ± 0.0 1.1 ± 0.0
Type of muscle L. lumbarum B. femoris P value
74.5 ± 0.1 78.9 ± 0.1 0.0001
19.4 ± 0.1 18.2 ± 0.1 0.0001
5.1 ± 0.1 2.5 ± 0.1 0.0001
1.1 ± 0.0 1.0 ± 0.0 0.0001
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Fig. 2. Concentration (ng/ml) of IGF-1 in blood plasma of Rahmani and Ossimi lambs affected by age.
Fig. 3. Histological sections of two types of skeletal muscles in two sheep breeds.
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Table 3 Histological parameters of lamb muscles as affected by breed, age at slaughter and type of muscle. Effect
No of fibers/bundle
Fiber diameter (µm)
Bundle area (Mm2)
Stroma area (mm2)
Bundle: stroma area
Breed Rahmani Ossimi P value
63.6 ± 1.4 67.5 ± 1.3 0.05
75.3 ± 2.2 78.2 ± 2.2 0.35
0.188 ± 0.80 0.191 ± .79 0.81
0.023 ± .04 0.024 ± .04 0.73
8.2:1 8.0:1 0.23
Age (day) 270 360 P value
65.4 ± 1.3 65.6 ± 1.5 0.91
75.4 ± 2.0 78.1 ± 2.3 0.38
0.189 ± .74 0.191 ± .85 0.85
0.024 ± .03 0.023 ± .04 0.47
7.9:1 8.3:1 0.21
Type of muscle L. lumbarum B. femoris P value
55.0 ± 1.4 76.0 ± 1.4 0.0001
55.1 ± 2.2 98.5 ± 2.2 0.0001
0.171 ± .80 0.262 ± .80 0.0001
0.021 ± .04 0.026 ± .04 0.0001
8.0:1 10:1 0.0001
(P b 0.0001) fat percentages compared to those slaughtered at day 270 of age (Table 2). Ash and protein contents were neither affected by breed nor by age at slaughter. L. lumbarum muscle contained higher percentages of protein (P b 0.0001), fat (P b 0.0001) and ash (P b 0.001), while moisture was less (P b 0.0001) compared to B. femoris muscle. The high content of fat in L. lumbarum is most probably due to the high content in intramuscular fat. 3.2. Concentration of IGF-I IGF-I concentration was almost similar in both breeds throughout the experimental period. During P I and P II of the growth curve, IGF-I concentration fluctuated within a range of b500 ng/ml. At the beginning of P III, IGF-I concentration increased to N500 ng/ml, with a temporary drop at day 300 of age. The concentration of plasma IGF-I in Rahmani was relatively higher than that in Ossimi within P III (Fig. 2). 3.3. Histological traits The lean meat incorporates several skeletal muscles; each is composed, mainly, of muscle fibers. These fibers are gathered in adjacent bundles, the Fascicles, (F, Fig. 3) of different sizes. Each bundle is surrounded by connective tissue, the Perimesium (P, Fig. 3). These connective tissue septa furnish the stroma which connects the muscular tissue in compact structure. Fig. 3 shows cross-sections in lean meat of L. lumbarum and B. femoris of Rahmani and Ossimi lambs at 270 and 360 days of age. It is clear in Fig. 3 that L. lumbarum has thinner fibers, with no distinct breed differences, in accordance with Table 3. Number of fibers per bundle was higher (P b 0.05) in Ossimi than in Rahmani lambs. Meanwhile, fiber diameter, bundle area, stroma area and bundle:stroma area are similar in the two studied breeds. Age at slaughter has no effect on all the studied histological traits. On the other hand, type of muscle had significant effects on all the studied traits, which was less (P b 0.05) in L. lumbarum muscle compared to B. femoris (Table 3). Number of fibers/bundle, fiber diameter and bundle cross-sectional area was increased by 38.2, 78.8 and 53.2% in B. femoris compared to L. lumbarum, respectively.
4. Discussion The obtained results indicated that the growth curve, weight at slaughter and carcass traits of these two breeds (Fig. 1 and Table 1) of Rahmani and Ossimi lambs are similar under sheep production systems of Egypt. The transformation of growth curve from concave shape to liner one during P II and P III may be due to the greatest relative growth rate (Lawrence and Fowler, 1998) during these two phases. The obtained concentration of IGF-I during P I and P II (105–300 ng/ml) in the two breeds is close to that reported by Medrano and Bradford (1991). The noticeable increase in IGF-I concentration during P III is due to approaching adulthood of the lambs (Jones and Clemmons, 1995; Oksbjerg et al., 2004) as reported by Hamdon et al. (2006). Low separable fat (P b 0.0001) in Rahmani rib cut (Table 1) and low inter-muscular fat (Table 2); as determined by chemical analysis; may be due to that Rahmani is late mature breed relative to Ossimi (Ashmawy, 1985). This gives Rahmani meat an advantage from the consumer's point of view. The increase in fiber diameter in Ossimi than in Rahmani (Table 3) may be due to the accumulation of the protein (Carpenter et al., 1996), which resulted in an increase in protein content in Ossimi meat however, insignificant (Table 2). Increase (P b 0.001) in slaughter weight and increase in boneless meat (P b 0.002) indicated that slaughtering lambs at 360 days of age resulted more meat relative to age of 270 days (Table 1). The decrease (P b 0.002) in lean and an increase (P b 0.0001) in fat percentages (Table 1) of lambs slaughtered at 360 days of age indicated the nutritive quality of lambs slaughtered at 270 days. This suggestion is supported by the lower (P b 0.0001) fat and higher (P b 0.001) protein contents of meat by 3 and 3.5%, respectively (Table 2). The increase in fiber diameter and bundle area with age progress may be attributed to the increase in IGF-I between days 270 and 360 of age, which acts on muscle hypertrophy (Mathison et al., 1998) and increase protein synthesis (Shimizu et al., 1986). The comparison between L. lumbarum and B. femoris muscles indicated the good nutritive quality of L. lumbarum. This is shown by the better judgmental chemical characteristics of L. lumbarum than B. femoris, low moisture and higher (P b 0.0001) contents of protein and fat (Table 2). Histological
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