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Productive performance and carcass characteristics of lambs fed finishing ration containing various forage levels
Small Ruminant Research 43 (2002) 283±288
Productive performance and carcass characteristics of lambs fed ®nishing ration containing various forage levels H. Fimbresa, G. HernaÂndez-Vidala, J.F. PicoÂn-Rubioa, J.R. Kawasa, C.D. Lub* a
Departamento de NutricioÂn y Metabolismo Animal, Facultad de Medicina Veterinaria y Zootecnia, Universidad AutoÂnoma de Nuevo LeoÂn, LaÂzaro CaÂrdenas 4600, Monterrey 66470, N.L., Mexico b School of Agriculture and Natural Resources, State University of New York, Morrisville, NY 13408, USA Accepted 16 December 2001
Abstract This study was conducted to determine the effect of forage level in the ®nishing ration on productive performance and carcass characteristics in lambs. Twenty male Pelibuey lambs, weighing 24 kg, were assigned to one of the four groups according to a completely randomized design. Each group received one of the four treatments with hay levels at 0, 10, 20 or 30%. Lambs were individually con®ned to 1.5 m2 metabolic cages. Dry matter (DM) intake was 48.9% greater for the 30% hay ration than for ration without hay during the entire 60-day-period, as compared to a 56.6% increase during the ®rst 30 days. However, greater hay levels in the ration were associated with lower weight gain. Period differences were also noted, with an average daily gain of 268 g during the ®rst 30 days, and a much lower P < 0:01 average daily gain of 149 g during the last 30 days. It appeared that the more days the lambs stayed on feed, the less was their weight gain. Feed ef®ciency of the lambs during the ®rst 30 days (5.0) was greater than during the last 30 days (10.1). Cold and hot carcass weights (kg) decreased (linear, P < 0:05) as the level of hay in the ration increased. Full gastrointestinal tract weight tended to increase with an increase in the hay level of the ration. However, there was no treatment effect on the weight of empty gastrointestinal tracts. Hay level in the ration did not affect marbling score, degree of ®nishing, external fat or longissimus muscle (ribeye) area. No effect of hay level in the ration was observed on weight of skin, liver, lungs, testicles or blood. First and second yield carcass grade reduced (linear, P < 0:001) as the level of hay in the ration increased. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Lambs; Finishing ration; Forage; Carcass; Weight gain
1. Introduction Recently, lamb feedlot research has focused on reducing the forage level of the ration as a mean of reducing the energetic cost of gain. However, since forage is needed for rumen function, small quantities *
Corresponding author. Tel.: 1-315-684-6083; fax: 1-315-684-6125. E-mail address: [email protected] (C.D. Lu).
should be included in the diet (Bartle and Preston, 1992). In a study by Kawas et al. (1991), maximum growth and heavier carcass weights of Santa Ines Morada Nova lambs were observed when hay levels were minimal. Several studies on the ef®ciency of various forages and their effects on feedlot performance of lambs have been conducted (Haskins et al., 1969; McCartor et al., 1972; Moore et al., 1990; Mader et al., 1991). Bartle and Preston (1991, 1992) demonstrated the economic
0921-4488/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 4 8 8 ( 0 2 ) 0 0 0 1 4 - 7
284
H. Fimbres et al. / Small Ruminant Research 43 (2002) 283±288
bene®t of reducing the forage content of feedlot rations. Scarce information on feedlot performance of lambs is available, especially of hair breeds. The purpose of this study is to examine the effect of ®ber level in the ration of Pelibuey lambs, on feedlot performance and carcass characteristics. 2. Materials and methods 2.1. Animals, diets and sampling procedures Twenty male Pelibuey lambs, with an average weight of 23.9 kg, were randomly assigned to one of the four treatments according to a completely randomized design. Treatments were experimental rations consisted of four forage levels: 0, 10, 20 or 30% hay. Lambs were con®ned to individual metabolic cages (1.5 m2) equipped with water and feed troughs. Rations were formulated to be isonitrogenous and contain 15% crude protein. The ionophore, sodium lasalocid (30 g/t), was included in all rations as a nonnutritive additive to improve feed ef®ciency. Ingredients and chemical composition of experimental rations is presented in Table 1. Rations were offered three times daily at 8 a.m., 1 and 5 p.m. Feed offered was based on the intake of the previous day plus an additional 10% in order to reduce selection of food components. The production trial lasted for 75 days, including a 15-day adaptation period and 60-day data collection period. After adapting to the metabolic cages and experimental diets, lambs were weighed on two consecutive days to provide baseline weights. Average weight of lambs on day 30 and 60 was obtained by averaging weights obtained on day 29 and 30, and day 59 and 60, respectively. Feed and orts samples were dried in a 60 8C air-draft oven and ground through a 1 mm sieve in a Willey Mill, before analysis. Dry matter (DM) content was determined at 105 8C (AOAC, 1997). Ash content was determined after sample combustion in a muf¯e furnace at 550 8C for 3 h. At the end of the experiment the lambs were transported to a slaughterhouse, where they were weighed before sacri®ce. Hot carcass weight and dressing percentage (carcass weight as a percent of
Table 1 Feed composition of ®nishing rations with various levels of forage fed to the lambs Item
Forage (%) 0
10
20
30
Ingredient (%) Klein grass hay Sorghum graina Soybean meal Molasses Premixb
± 83.3 9.7 5.0 2.0
10.0 72.8 10.2 5.0 2.0
20.0 62.3 10.7 5.0 2.0
30.0 51.8 11.2 5.0 2.0
Chemical composition NEm (Mcal/kg)c NEg (Mcal/kg)c Crude protein (%) Bypass protein (%) Calcium (%) Phosphorus (%) Potassium (%) Crude fiber (%)
2.00 1.36 15.0 7.3 0.52 0.41 0.72 2.9
1.93 1.28 15.0 6.9 0.58 0.40 0.85 6.3
1.85 1.20 15.0 6.5 0.63 0.38 0.98 9.7
1.70 1.11 15.0 6.1 0.68 0.36 1.10 13.1
a
50% whole and 50% ground. Containing trace minerals, vitamins A and E, sodium lasalocid (30 g/t) and urea (20.9%). c NEm, net energy for maintenance; NEg, net energy for gain (NRC, 1985). b
live weight) were recorded. Height to the cross length, and thoracic circumference (from scapula±humeral to the coxo-femoral tuberosities) were measured. Weights of skin, kidney, lungs, testicles and blood were recorded. Carcasses were hanged and refrigerated for 24 h at 3±5 8C, then evaluated after cutting between 12th and 13th ribs. 2.2. Statistical analysis DM intake, weight gain and feed ef®ciencies were analyzed with an analysis of variance of a completely randomized design with a 2 4 factorial arrangement of treatments (feeding period and hay level in the ®nishing rations). Treatment effects on slaughter weight, hot and cold carcass weights, hot and cold dressing percentages, full and empty gastrointestinal tract (GIT), empty body weight (EBW) and DM intake (g/kg EBW) were analyzed using the GLM procedure of a completely randomized design. All variables were analyzed for linear and quadratic responses to hay level using orthogonal contrasts (Steel and Torrie, 1980).
H. Fimbres et al. / Small Ruminant Research 43 (2002) 283±288
3. Results 3.1. DM intake, live weight gain and feed ef®ciency Period and treatment means of DM intake, BW gain and feed ef®ciency (kg of feed per kg gain) of lambs are presented in Table 2. Initial body weight of lambs (averaging 23.9 kg) did not differ P > 0:05 among treatments (Table 2). The level of hay in the ®nishing rations had a signi®cant effect on DM intake P < 0:01. Effect of period on DM intake was not signi®cant (Table 2). DM intake increased by 48.9% in lambs that consumed 30% hay in their ration, in comparison with those consuming the ration without hay P < 0:05. During the ®rst 30 days, DM intake increased linearly P < 0:01, approximately 56.6%, as the level of hay in the ration increased from 0 to 30%. Level of hay in the ration P < 0:01 and period P < 0:001 affected weight gain. There was an interaction between period and hay level (Table 2). Increased level of hay in the ration reduced live weight gain P < 0:05. During the ®rst 30 days of the study, live weight gained averaged 268 g/day. Live weight gain was lower P < 0:01 during the second 30 days of the trial, averaging 149 g/day. Lambs gained 209 g/ day over the 60-day-period. Weight gain decreased with the number of days that the animal was on feed. Weight gain of lambs during the ®rst 30 days decreased linearly P < 0:01 by 56.6%, as hay level increased from 0 to 30%. During this period, live weight gains were 332, 265, 263 and 212 g/day for 0, 10, 20 and 30% hay diet, respectively. During the second period (31±60 days), live weight gain decreased linearly P < 0:01, however, only by 25.2%. During this period, weight gains were 169,
285
150, 144 and 135 g/day for 0, 10, 20 and 30% hay diet, respectively. 3.2. Feed ef®ciency Feed ef®ciency (Table 2) of lambs was in¯uenced P < 0:01 by both period of the study and hay level. Feed ef®ciency expressed as kg feed/kg daily weight gain was 5.0 during the ®rst 30 days, and was 10.1 during the last 30 days. During the ®rst period, feed energy may have been used primarily for muscular synthesis, whereas during the second period, more energy was used for fat deposition. Feed ef®ciency was inversely related to P < 0:01 the level of hay in the ration, 4.9, 7.1, 7.6 and 10.3 kg of feed per kilogram of weight gain for 0, 10, 20 and 30% hay diets, respectively. 3.3. Carcass weights and dressing percentage The effects of the level of hay in the ration on carcass weight and dressing percent are presented in Table 3. Hot and cold carcass weights decreased as the level of hay in the ration increased P < 0:05. Hay levels of 0, 10, 20 and 30% in the ration were associated with hot carcass weights of 21.5, 19.6, 19.2 and 18.5 kg and cold carcass weights of 21.1, 19.3, 18.9 and 18.1 kg, respectively. Hot and chilled dressing percentages were not affected P > 0:05 by the level of hay in the ration. 3.4. GIT ®ll and EBW Level of hay in the ®nishing rations did not affect P > 0:05 full and empty GIT weights and EBW (Table 4). However, full GIT weight tended to increase
Table 2 Intake, weight gain and feed ef®ciency of lambs fed ®nishing rations with various levels of forage Item
Period (days)
DM intake (g) Weight gain (g/day) Feed efficiency (intake/gain) a b
S.E.M.
0±30
31±60
0±60
1227 268 5.0
1257 149 10.1
1242 209 7.5
Probability. Period forage interaction.
38 12 0.9
Forage (%)
S.E.M.
0
10
20
30
960 250 4.9
1200 207 7.1
1377 203 7.6
1429 174 10.3
44 14 0.9
Pa Period
Forage
P Fb
0.855 <0.001 <0.001
<0.001 0.003 0.005
0.508 0.763 0.990
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H. Fimbres et al. / Small Ruminant Research 43 (2002) 283±288
Table 3 Hot and cold carcass weight and dressing percentage of lambs fed ®nishing rationa with various forage levels Carcass traits
Slaughter weight (kg) Hot carcass weight (kg) Chilled carcass weight (kg) Hot dressing (%) Chilled dressing (%)
S.E.M.a
Forage (%) 0
10
20
30
39.0 21.5 21.1 55.0 53.9
36.3 19.6 19.3 54.1 53.0
36.5 19.2 18.9 52.5 51.5
31.1 18.5 18.1 54.2 53.1
1.0 0.80 0.8 1.8 1.7
Pb Lc
Qd
0.006 0.017 0.017 0.610 0.610
0.760 0.490 0.490 0.490 0.480
a
Standard error of mean. Probability. c Linear effect. d Quadratic effect. b
Table 4 Full and empty GIT weight, EBW and DM intake of lambs fed ®nishing rations with various forage levels Item
Full GIT (kg) Empty GIT (kg) EBW (kg) DM intake (g/kg EBW)
S.E.M.a
Forage (%) 0
10
20
30
6.6 2.0 31.9 29.0
7.1 1.9 31.8 29.0
7.4 2.2 31.5 37.8
7.9 2.2 30.5 41.0
Pb Lc
Qd
0.6 0.2 2.3 2.2
0.150 0.200 0.670 0.001
1.000 0.610 0.850 0.470
S.E.M.a
Pb
a
Standard error of mean. Probability. c Linear effect. d Quadratic effect. b
Table 5 Carcass characteristics of lambs fed ®nishing rations with various forage levels Item
Marblinge Degree of finishingf Fat thickness (mm) Longissimus muscle area (cm2) KPH fat (%)g First grade cuts (%)h Second grade cuts (%)i a
Forage (%) 0
10
20
30
4 1 0.07 1.9 3.3 54.2 74.2
4 1 0.11 1.8 3.5 53.2 72.2
3 1 0.08 2.0 2.9 52.2 70.2
5 2 0.11 2.0 2.5 51.2 68.2
Standard error of mean. Probability. c Linear effect. d Quadratic effect. e 1, Slightly abundant; 2, moderate; 3, modest; 4, small; 5, slight and 6, traces. f 1, Supreme; 2, select. g Kidney, pelvic and heart fat. h Percent expected cuts of the rack, loin and leg. i Percent expected cuts of the shoulder, neck and breast. b
0.7 0.2 0.01 0.1 0.4 0.1 0.3
Lc
Qd
0.470 0.110 0.260 0.270 1.100 0.001 0.001
0.120 0.350 0.700 0.850 0.450 1.000 1.000
H. Fimbres et al. / Small Ruminant Research 43 (2002) 283±288
287
Table 6 Body measurements and weight of visceral organs of lambs fed ®nishing rations with various forage levels Item
0 Height to the cross (cm) Length of tuberosities (cm) Thoracic circumference (cm) Weight of visceral organs (g) Skin Liver Lungs Testicles Blood
S.E.M.a
Forage (%) 10 61.2 62.6 78.7 3340 690 546 479 1587
60.4 58.6 80.9 3940 648 627 544 1493
20
30 66.8 59.7 81.8
3920 761 597 523 1577
63.0 63.2 79.8 3460 729 543 555 1473
3.2 1.9 2.6 421 65 38 67 127
Pb Lc
Qd
0.420 0.730 0.720
0.640 0.060 0.430
0.850 0.430 0.820 0.490 0.650
0.220 0.940 0.090 0.800 0.960
a
Standard error of mean. Probability. c Linear effect. d Quadratic effect. b
P > 0:05 with the level of hay in the ration. DM intake expressed as g/kg EBW increased as the level of the hay in the ®nishing ration increased (linear, P < 0:001) from 29 to 41. 3.5. Carcass characteristics The level of hay in the ®nishing rations did not affect marbling score, degree of ®nishing, fat thickness, ribeye area and organ fat (Table 5). Percentages of ®rst and second grade cuts decreased as the level of the hay in the ®nishing ration increased (linear, P > 0:001). 3.6. Body measurements and visceral organ weights Height to the cross, length of tuberosities and thoracic circumference were not affected (linear and quadratic, P > 0:05) by the level of the hay in the ®nishing ration (Table 6). Weights of skin, liver, lungs, testicles and blood were not affected by the hay level as well. 4. Discussion 4.1. Body weight gain An increase in live weight gain observed in lambs was associated with greater concentrate level (Petit et al., 1997) or higher energy density in the diet
(Mahgoub et al., 2000). The increase in DM intake as a result of feeding higher percentage of hay can be attributed to the regulatory effect of dietary energy intake. When lambs were fed ®nishing rations, particle size of forage was small enough so that physical ®ll was not the dominant factor in the regulation of intake. Similar observations had been reported (Lu and Potchoiba, 1990). Difference in live weight gain between periods can be attributed to differential energy requirements for fat deposition vs. muscle growth. Fluharty and McClure (1997) fed lambs ad libitum or with restriction (85% of ad libitum intake) in two periods. During the ®rst period, lambs fed ad libitum had signi®cantly greater DM intake and reached the desired weight in a shorter time. They concluded that during the second period, lambs gained less weight since a great amount of the energy of the diet was utilized to deposit fat, requiring more energy in comparison with gain during the ®rst period. 4.2. Feed ef®ciency Increased hay level in the ration resulted in higher ®ber and lower energy density. Offering feed with higher grain content resulted in an increase in live weight gain of growing lambs (Petit and Castonguay, 1994), as was observed in the present study. Petit et al. (1997) reported that feed ef®ciency was similar for lambs fed two types of hay, since weight gain and DM intake were similar.
288
H. Fimbres et al. / Small Ruminant Research 43 (2002) 283±288
4.3. Carcass weight and dressing percent
References
Results of this study on carcass weight and dressing percentage are similar to those reported by Petit et al. (1997) who found no effect of ration on carcass dressing percentage. However, energy concentration of their feed was lower compared to that in the present study.
AOAC, 1997. Of®cial methods of analysis (16th ed.). Association of of®cial analytical chemists, Washington, DC. Bartle, S.J., Preston, R.L., 1991. Dietary roughage regimen for feedlot steers: reduced roughage level (2%) during the mid®nishing period. J. Anim. Sci. 69, 3461±3466. Bartle, S.J., Preston, R.L., 1992. Roughage level and limited maximum intake regimens for feedlot steers. J. Anim. Sci. 70, 3293. Burrin, D.G., Britton, R.A., Ferrel, C.L., Bauer, M.L., 1992. Level of nutrition and visceral organ protein synthetic capacity and nucleic acid content in sheep. J. Anim. Sci. 70, 1137. Ferrel, C.L., Jenkins, T.J., 1985. Cow type and the nutritional environment: nutritional aspects. J. Anim. Sci. 61, 725. Ferrel, C.L., Koong, L.J., Nienaber, J.A., 1986. Effects of previous nutrition on body composition and maintenance energy costs of growing lambs. Br. J. Nutr. 56, 595. Fluharty, F.L., McClure, K.E., 1997. Effects of dietary energy intake and protein concentration on performance and visceral organ mass in lambs. J. Anim. Sci. 75, 604±610. Haskins, B.R., Wise, M.B., Craig, H.B., Blumer, T.N., Barrick, E.R., 1969. Effects of adding low levels of roughage or roughage substitutes to high energy rations for fattening steers. J. Anim. Sci. 29, 345. Kawas, J.R., Guimaraes, W., Selton, J.M., Lu, C.D., 1991. Effect of varying concentrations of energy and protein in pelleted diets of Santa Ines and Morada Nova hair sheep on intake, digestion and growth. In: Shephan Wildeus (Ed.), Proceedings of Hair Sheep Research Symposium. University of the Virgin Islands, St. Croix, Virgin Islands, US. Lu, C.D., Potchoiba, M.J., 1990. Feed intake and weight gain of growing goats fed diets of various energy and protein levels. J. Anim. Sci. 68, 1751±1759. Mader, T.L., Dahlquist, J.M., Schmidt, L.D., 1991. Roughage sources in beef cattle ®nishing diets. J. Anim. Sci. 69, 462. Mahgoub, D., Lu, C.D., Early, R.J., 2000. Effects of dietary energy density on feed intake, body weight gain and carcass chemical composition of Omani growing lambs. Small Rumin. Res. 37, 35±42. McCartor, M.M., England, M.W., He¯ey, H.M., 1972. Effects of various roughages in high concentrate beef cattle diets on animal performance and carcass characteristics. J. Anim. Sci. 34, 142. Moore, J.A., Poore, M.H., Swingle, R.S., 1990. In¯uence of roughage source on kinetics of digestion and passage, and on calculated extents of ruminal digestion in beef steers fed 65% concentrate diets. J. Anim. Sci. 68, 3412. NRC, 1985. Nutrient Requirements of Sheep, 6th Edition. National Academy Press, Washington, DC. Petit, H.V., Castonguay, F., 1994. Growth and carcass quality of proli®c crossbred lambs fed silage with ®sh meal or different amounts of concentrate. J. Anim. Sci. 72, 1849. Petit, H.V., Tremblay, G.F., Savoie, 1997. Performance of growing lambs fed two levels of concentrate with conventional or macerated timothy hay. J. Anim. Sci. 75, 598±603. Steel, R.G.D., Torrie, J.H., 1980. Principles and Procedures of Statistics: A Biometrical Approach, 2nd Edition. McGraw-Hill, New York.
4.4. GIT ®ll and EBW Heavier full GIT weight of lambs fed ®nishing ration containing hay could be attributed to the higher ®ber content which has a greater capacity to retain water. DM intake per kilogram EBW was 41.4% greater in lambs fed the ration with 30% hay, than with the ration without hay. This ®nding may be due to the fact that the increase in the weight of visceral organs is associated with cellular hypertrophy, and not with an increase in number of cells (Burrin et al., 1992). 4.5. Effect on the size of internal organs Our results on the weights of skin, liver, lungs, testicles and blood coincide with those reported by Fluharty and McClure (1997), who did not ®nd differences in body weight or hot or cold carcass weight. Apparently, these organs are more related to the size of the animals than to the growth and weight of the visceral organs. Visceral organs, especially the liver and the GIT, appear to be associated with high rates of tissue protein synthesis (Ferrel and Jenkins, 1985). A greater proportion of the total protein synthesis occurred in the GIT (19±23%), liver, kidney and pancreas (16±17%), and striated muscle (24±28%). The metabolic activity of the visceral organs can depend on the activity and the size of the organ (Ferrel et al., 1986).
5. Conclusions Energy dilution as a result of including hay in the ®nishing ration did result in an increase in DM intake in lambs. Nevertheless, it did not improve productive performance or carcass characteristics.
Productive performance and carcass characteristics of lambs fed ®nishing ration containing various forage levels H. Fimbresa, G. HernaÂndez-Vidala, J.F. PicoÂn-Rubioa, J.R. Kawasa, C.D. Lub* a
Departamento de NutricioÂn y Metabolismo Animal, Facultad de Medicina Veterinaria y Zootecnia, Universidad AutoÂnoma de Nuevo LeoÂn, LaÂzaro CaÂrdenas 4600, Monterrey 66470, N.L., Mexico b School of Agriculture and Natural Resources, State University of New York, Morrisville, NY 13408, USA Accepted 16 December 2001
Abstract This study was conducted to determine the effect of forage level in the ®nishing ration on productive performance and carcass characteristics in lambs. Twenty male Pelibuey lambs, weighing 24 kg, were assigned to one of the four groups according to a completely randomized design. Each group received one of the four treatments with hay levels at 0, 10, 20 or 30%. Lambs were individually con®ned to 1.5 m2 metabolic cages. Dry matter (DM) intake was 48.9% greater for the 30% hay ration than for ration without hay during the entire 60-day-period, as compared to a 56.6% increase during the ®rst 30 days. However, greater hay levels in the ration were associated with lower weight gain. Period differences were also noted, with an average daily gain of 268 g during the ®rst 30 days, and a much lower P < 0:01 average daily gain of 149 g during the last 30 days. It appeared that the more days the lambs stayed on feed, the less was their weight gain. Feed ef®ciency of the lambs during the ®rst 30 days (5.0) was greater than during the last 30 days (10.1). Cold and hot carcass weights (kg) decreased (linear, P < 0:05) as the level of hay in the ration increased. Full gastrointestinal tract weight tended to increase with an increase in the hay level of the ration. However, there was no treatment effect on the weight of empty gastrointestinal tracts. Hay level in the ration did not affect marbling score, degree of ®nishing, external fat or longissimus muscle (ribeye) area. No effect of hay level in the ration was observed on weight of skin, liver, lungs, testicles or blood. First and second yield carcass grade reduced (linear, P < 0:001) as the level of hay in the ration increased. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Lambs; Finishing ration; Forage; Carcass; Weight gain
1. Introduction Recently, lamb feedlot research has focused on reducing the forage level of the ration as a mean of reducing the energetic cost of gain. However, since forage is needed for rumen function, small quantities *
Corresponding author. Tel.: 1-315-684-6083; fax: 1-315-684-6125. E-mail address: [email protected] (C.D. Lu).
should be included in the diet (Bartle and Preston, 1992). In a study by Kawas et al. (1991), maximum growth and heavier carcass weights of Santa Ines Morada Nova lambs were observed when hay levels were minimal. Several studies on the ef®ciency of various forages and their effects on feedlot performance of lambs have been conducted (Haskins et al., 1969; McCartor et al., 1972; Moore et al., 1990; Mader et al., 1991). Bartle and Preston (1991, 1992) demonstrated the economic
0921-4488/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 4 8 8 ( 0 2 ) 0 0 0 1 4 - 7
284
H. Fimbres et al. / Small Ruminant Research 43 (2002) 283±288
bene®t of reducing the forage content of feedlot rations. Scarce information on feedlot performance of lambs is available, especially of hair breeds. The purpose of this study is to examine the effect of ®ber level in the ration of Pelibuey lambs, on feedlot performance and carcass characteristics. 2. Materials and methods 2.1. Animals, diets and sampling procedures Twenty male Pelibuey lambs, with an average weight of 23.9 kg, were randomly assigned to one of the four treatments according to a completely randomized design. Treatments were experimental rations consisted of four forage levels: 0, 10, 20 or 30% hay. Lambs were con®ned to individual metabolic cages (1.5 m2) equipped with water and feed troughs. Rations were formulated to be isonitrogenous and contain 15% crude protein. The ionophore, sodium lasalocid (30 g/t), was included in all rations as a nonnutritive additive to improve feed ef®ciency. Ingredients and chemical composition of experimental rations is presented in Table 1. Rations were offered three times daily at 8 a.m., 1 and 5 p.m. Feed offered was based on the intake of the previous day plus an additional 10% in order to reduce selection of food components. The production trial lasted for 75 days, including a 15-day adaptation period and 60-day data collection period. After adapting to the metabolic cages and experimental diets, lambs were weighed on two consecutive days to provide baseline weights. Average weight of lambs on day 30 and 60 was obtained by averaging weights obtained on day 29 and 30, and day 59 and 60, respectively. Feed and orts samples were dried in a 60 8C air-draft oven and ground through a 1 mm sieve in a Willey Mill, before analysis. Dry matter (DM) content was determined at 105 8C (AOAC, 1997). Ash content was determined after sample combustion in a muf¯e furnace at 550 8C for 3 h. At the end of the experiment the lambs were transported to a slaughterhouse, where they were weighed before sacri®ce. Hot carcass weight and dressing percentage (carcass weight as a percent of
Table 1 Feed composition of ®nishing rations with various levels of forage fed to the lambs Item
Forage (%) 0
10
20
30
Ingredient (%) Klein grass hay Sorghum graina Soybean meal Molasses Premixb
± 83.3 9.7 5.0 2.0
10.0 72.8 10.2 5.0 2.0
20.0 62.3 10.7 5.0 2.0
30.0 51.8 11.2 5.0 2.0
Chemical composition NEm (Mcal/kg)c NEg (Mcal/kg)c Crude protein (%) Bypass protein (%) Calcium (%) Phosphorus (%) Potassium (%) Crude fiber (%)
2.00 1.36 15.0 7.3 0.52 0.41 0.72 2.9
1.93 1.28 15.0 6.9 0.58 0.40 0.85 6.3
1.85 1.20 15.0 6.5 0.63 0.38 0.98 9.7
1.70 1.11 15.0 6.1 0.68 0.36 1.10 13.1
a
50% whole and 50% ground. Containing trace minerals, vitamins A and E, sodium lasalocid (30 g/t) and urea (20.9%). c NEm, net energy for maintenance; NEg, net energy for gain (NRC, 1985). b
live weight) were recorded. Height to the cross length, and thoracic circumference (from scapula±humeral to the coxo-femoral tuberosities) were measured. Weights of skin, kidney, lungs, testicles and blood were recorded. Carcasses were hanged and refrigerated for 24 h at 3±5 8C, then evaluated after cutting between 12th and 13th ribs. 2.2. Statistical analysis DM intake, weight gain and feed ef®ciencies were analyzed with an analysis of variance of a completely randomized design with a 2 4 factorial arrangement of treatments (feeding period and hay level in the ®nishing rations). Treatment effects on slaughter weight, hot and cold carcass weights, hot and cold dressing percentages, full and empty gastrointestinal tract (GIT), empty body weight (EBW) and DM intake (g/kg EBW) were analyzed using the GLM procedure of a completely randomized design. All variables were analyzed for linear and quadratic responses to hay level using orthogonal contrasts (Steel and Torrie, 1980).
H. Fimbres et al. / Small Ruminant Research 43 (2002) 283±288
3. Results 3.1. DM intake, live weight gain and feed ef®ciency Period and treatment means of DM intake, BW gain and feed ef®ciency (kg of feed per kg gain) of lambs are presented in Table 2. Initial body weight of lambs (averaging 23.9 kg) did not differ P > 0:05 among treatments (Table 2). The level of hay in the ®nishing rations had a signi®cant effect on DM intake P < 0:01. Effect of period on DM intake was not signi®cant (Table 2). DM intake increased by 48.9% in lambs that consumed 30% hay in their ration, in comparison with those consuming the ration without hay P < 0:05. During the ®rst 30 days, DM intake increased linearly P < 0:01, approximately 56.6%, as the level of hay in the ration increased from 0 to 30%. Level of hay in the ration P < 0:01 and period P < 0:001 affected weight gain. There was an interaction between period and hay level (Table 2). Increased level of hay in the ration reduced live weight gain P < 0:05. During the ®rst 30 days of the study, live weight gained averaged 268 g/day. Live weight gain was lower P < 0:01 during the second 30 days of the trial, averaging 149 g/day. Lambs gained 209 g/ day over the 60-day-period. Weight gain decreased with the number of days that the animal was on feed. Weight gain of lambs during the ®rst 30 days decreased linearly P < 0:01 by 56.6%, as hay level increased from 0 to 30%. During this period, live weight gains were 332, 265, 263 and 212 g/day for 0, 10, 20 and 30% hay diet, respectively. During the second period (31±60 days), live weight gain decreased linearly P < 0:01, however, only by 25.2%. During this period, weight gains were 169,
285
150, 144 and 135 g/day for 0, 10, 20 and 30% hay diet, respectively. 3.2. Feed ef®ciency Feed ef®ciency (Table 2) of lambs was in¯uenced P < 0:01 by both period of the study and hay level. Feed ef®ciency expressed as kg feed/kg daily weight gain was 5.0 during the ®rst 30 days, and was 10.1 during the last 30 days. During the ®rst period, feed energy may have been used primarily for muscular synthesis, whereas during the second period, more energy was used for fat deposition. Feed ef®ciency was inversely related to P < 0:01 the level of hay in the ration, 4.9, 7.1, 7.6 and 10.3 kg of feed per kilogram of weight gain for 0, 10, 20 and 30% hay diets, respectively. 3.3. Carcass weights and dressing percentage The effects of the level of hay in the ration on carcass weight and dressing percent are presented in Table 3. Hot and cold carcass weights decreased as the level of hay in the ration increased P < 0:05. Hay levels of 0, 10, 20 and 30% in the ration were associated with hot carcass weights of 21.5, 19.6, 19.2 and 18.5 kg and cold carcass weights of 21.1, 19.3, 18.9 and 18.1 kg, respectively. Hot and chilled dressing percentages were not affected P > 0:05 by the level of hay in the ration. 3.4. GIT ®ll and EBW Level of hay in the ®nishing rations did not affect P > 0:05 full and empty GIT weights and EBW (Table 4). However, full GIT weight tended to increase
Table 2 Intake, weight gain and feed ef®ciency of lambs fed ®nishing rations with various levels of forage Item
Period (days)
DM intake (g) Weight gain (g/day) Feed efficiency (intake/gain) a b
S.E.M.
0±30
31±60
0±60
1227 268 5.0
1257 149 10.1
1242 209 7.5
Probability. Period forage interaction.
38 12 0.9
Forage (%)
S.E.M.
0
10
20
30
960 250 4.9
1200 207 7.1
1377 203 7.6
1429 174 10.3
44 14 0.9
Pa Period
Forage
P Fb
0.855 <0.001 <0.001
<0.001 0.003 0.005
0.508 0.763 0.990
286
H. Fimbres et al. / Small Ruminant Research 43 (2002) 283±288
Table 3 Hot and cold carcass weight and dressing percentage of lambs fed ®nishing rationa with various forage levels Carcass traits
Slaughter weight (kg) Hot carcass weight (kg) Chilled carcass weight (kg) Hot dressing (%) Chilled dressing (%)
S.E.M.a
Forage (%) 0
10
20
30
39.0 21.5 21.1 55.0 53.9
36.3 19.6 19.3 54.1 53.0
36.5 19.2 18.9 52.5 51.5
31.1 18.5 18.1 54.2 53.1
1.0 0.80 0.8 1.8 1.7
Pb Lc
Qd
0.006 0.017 0.017 0.610 0.610
0.760 0.490 0.490 0.490 0.480
a
Standard error of mean. Probability. c Linear effect. d Quadratic effect. b
Table 4 Full and empty GIT weight, EBW and DM intake of lambs fed ®nishing rations with various forage levels Item
Full GIT (kg) Empty GIT (kg) EBW (kg) DM intake (g/kg EBW)
S.E.M.a
Forage (%) 0
10
20
30
6.6 2.0 31.9 29.0
7.1 1.9 31.8 29.0
7.4 2.2 31.5 37.8
7.9 2.2 30.5 41.0
Pb Lc
Qd
0.6 0.2 2.3 2.2
0.150 0.200 0.670 0.001
1.000 0.610 0.850 0.470
S.E.M.a
Pb
a
Standard error of mean. Probability. c Linear effect. d Quadratic effect. b
Table 5 Carcass characteristics of lambs fed ®nishing rations with various forage levels Item
Marblinge Degree of finishingf Fat thickness (mm) Longissimus muscle area (cm2) KPH fat (%)g First grade cuts (%)h Second grade cuts (%)i a
Forage (%) 0
10
20
30
4 1 0.07 1.9 3.3 54.2 74.2
4 1 0.11 1.8 3.5 53.2 72.2
3 1 0.08 2.0 2.9 52.2 70.2
5 2 0.11 2.0 2.5 51.2 68.2
Standard error of mean. Probability. c Linear effect. d Quadratic effect. e 1, Slightly abundant; 2, moderate; 3, modest; 4, small; 5, slight and 6, traces. f 1, Supreme; 2, select. g Kidney, pelvic and heart fat. h Percent expected cuts of the rack, loin and leg. i Percent expected cuts of the shoulder, neck and breast. b
0.7 0.2 0.01 0.1 0.4 0.1 0.3
Lc
Qd
0.470 0.110 0.260 0.270 1.100 0.001 0.001
0.120 0.350 0.700 0.850 0.450 1.000 1.000
H. Fimbres et al. / Small Ruminant Research 43 (2002) 283±288
287
Table 6 Body measurements and weight of visceral organs of lambs fed ®nishing rations with various forage levels Item
0 Height to the cross (cm) Length of tuberosities (cm) Thoracic circumference (cm) Weight of visceral organs (g) Skin Liver Lungs Testicles Blood
S.E.M.a
Forage (%) 10 61.2 62.6 78.7 3340 690 546 479 1587
60.4 58.6 80.9 3940 648 627 544 1493
20
30 66.8 59.7 81.8
3920 761 597 523 1577
63.0 63.2 79.8 3460 729 543 555 1473
3.2 1.9 2.6 421 65 38 67 127
Pb Lc
Qd
0.420 0.730 0.720
0.640 0.060 0.430
0.850 0.430 0.820 0.490 0.650
0.220 0.940 0.090 0.800 0.960
a
Standard error of mean. Probability. c Linear effect. d Quadratic effect. b
P > 0:05 with the level of hay in the ration. DM intake expressed as g/kg EBW increased as the level of the hay in the ®nishing ration increased (linear, P < 0:001) from 29 to 41. 3.5. Carcass characteristics The level of hay in the ®nishing rations did not affect marbling score, degree of ®nishing, fat thickness, ribeye area and organ fat (Table 5). Percentages of ®rst and second grade cuts decreased as the level of the hay in the ®nishing ration increased (linear, P > 0:001). 3.6. Body measurements and visceral organ weights Height to the cross, length of tuberosities and thoracic circumference were not affected (linear and quadratic, P > 0:05) by the level of the hay in the ®nishing ration (Table 6). Weights of skin, liver, lungs, testicles and blood were not affected by the hay level as well. 4. Discussion 4.1. Body weight gain An increase in live weight gain observed in lambs was associated with greater concentrate level (Petit et al., 1997) or higher energy density in the diet
(Mahgoub et al., 2000). The increase in DM intake as a result of feeding higher percentage of hay can be attributed to the regulatory effect of dietary energy intake. When lambs were fed ®nishing rations, particle size of forage was small enough so that physical ®ll was not the dominant factor in the regulation of intake. Similar observations had been reported (Lu and Potchoiba, 1990). Difference in live weight gain between periods can be attributed to differential energy requirements for fat deposition vs. muscle growth. Fluharty and McClure (1997) fed lambs ad libitum or with restriction (85% of ad libitum intake) in two periods. During the ®rst period, lambs fed ad libitum had signi®cantly greater DM intake and reached the desired weight in a shorter time. They concluded that during the second period, lambs gained less weight since a great amount of the energy of the diet was utilized to deposit fat, requiring more energy in comparison with gain during the ®rst period. 4.2. Feed ef®ciency Increased hay level in the ration resulted in higher ®ber and lower energy density. Offering feed with higher grain content resulted in an increase in live weight gain of growing lambs (Petit and Castonguay, 1994), as was observed in the present study. Petit et al. (1997) reported that feed ef®ciency was similar for lambs fed two types of hay, since weight gain and DM intake were similar.
288
H. Fimbres et al. / Small Ruminant Research 43 (2002) 283±288
4.3. Carcass weight and dressing percent
References
Results of this study on carcass weight and dressing percentage are similar to those reported by Petit et al. (1997) who found no effect of ration on carcass dressing percentage. However, energy concentration of their feed was lower compared to that in the present study.
AOAC, 1997. Of®cial methods of analysis (16th ed.). Association of of®cial analytical chemists, Washington, DC. Bartle, S.J., Preston, R.L., 1991. Dietary roughage regimen for feedlot steers: reduced roughage level (2%) during the mid®nishing period. J. Anim. Sci. 69, 3461±3466. Bartle, S.J., Preston, R.L., 1992. Roughage level and limited maximum intake regimens for feedlot steers. J. Anim. Sci. 70, 3293. Burrin, D.G., Britton, R.A., Ferrel, C.L., Bauer, M.L., 1992. Level of nutrition and visceral organ protein synthetic capacity and nucleic acid content in sheep. J. Anim. Sci. 70, 1137. Ferrel, C.L., Jenkins, T.J., 1985. Cow type and the nutritional environment: nutritional aspects. J. Anim. Sci. 61, 725. Ferrel, C.L., Koong, L.J., Nienaber, J.A., 1986. Effects of previous nutrition on body composition and maintenance energy costs of growing lambs. Br. J. Nutr. 56, 595. Fluharty, F.L., McClure, K.E., 1997. Effects of dietary energy intake and protein concentration on performance and visceral organ mass in lambs. J. Anim. Sci. 75, 604±610. Haskins, B.R., Wise, M.B., Craig, H.B., Blumer, T.N., Barrick, E.R., 1969. Effects of adding low levels of roughage or roughage substitutes to high energy rations for fattening steers. J. Anim. Sci. 29, 345. Kawas, J.R., Guimaraes, W., Selton, J.M., Lu, C.D., 1991. Effect of varying concentrations of energy and protein in pelleted diets of Santa Ines and Morada Nova hair sheep on intake, digestion and growth. In: Shephan Wildeus (Ed.), Proceedings of Hair Sheep Research Symposium. University of the Virgin Islands, St. Croix, Virgin Islands, US. Lu, C.D., Potchoiba, M.J., 1990. Feed intake and weight gain of growing goats fed diets of various energy and protein levels. J. Anim. Sci. 68, 1751±1759. Mader, T.L., Dahlquist, J.M., Schmidt, L.D., 1991. Roughage sources in beef cattle ®nishing diets. J. Anim. Sci. 69, 462. Mahgoub, D., Lu, C.D., Early, R.J., 2000. Effects of dietary energy density on feed intake, body weight gain and carcass chemical composition of Omani growing lambs. Small Rumin. Res. 37, 35±42. McCartor, M.M., England, M.W., He¯ey, H.M., 1972. Effects of various roughages in high concentrate beef cattle diets on animal performance and carcass characteristics. J. Anim. Sci. 34, 142. Moore, J.A., Poore, M.H., Swingle, R.S., 1990. In¯uence of roughage source on kinetics of digestion and passage, and on calculated extents of ruminal digestion in beef steers fed 65% concentrate diets. J. Anim. Sci. 68, 3412. NRC, 1985. Nutrient Requirements of Sheep, 6th Edition. National Academy Press, Washington, DC. Petit, H.V., Castonguay, F., 1994. Growth and carcass quality of proli®c crossbred lambs fed silage with ®sh meal or different amounts of concentrate. J. Anim. Sci. 72, 1849. Petit, H.V., Tremblay, G.F., Savoie, 1997. Performance of growing lambs fed two levels of concentrate with conventional or macerated timothy hay. J. Anim. Sci. 75, 598±603. Steel, R.G.D., Torrie, J.H., 1980. Principles and Procedures of Statistics: A Biometrical Approach, 2nd Edition. McGraw-Hill, New York.
4.4. GIT ®ll and EBW Heavier full GIT weight of lambs fed ®nishing ration containing hay could be attributed to the higher ®ber content which has a greater capacity to retain water. DM intake per kilogram EBW was 41.4% greater in lambs fed the ration with 30% hay, than with the ration without hay. This ®nding may be due to the fact that the increase in the weight of visceral organs is associated with cellular hypertrophy, and not with an increase in number of cells (Burrin et al., 1992). 4.5. Effect on the size of internal organs Our results on the weights of skin, liver, lungs, testicles and blood coincide with those reported by Fluharty and McClure (1997), who did not ®nd differences in body weight or hot or cold carcass weight. Apparently, these organs are more related to the size of the animals than to the growth and weight of the visceral organs. Visceral organs, especially the liver and the GIT, appear to be associated with high rates of tissue protein synthesis (Ferrel and Jenkins, 1985). A greater proportion of the total protein synthesis occurred in the GIT (19±23%), liver, kidney and pancreas (16±17%), and striated muscle (24±28%). The metabolic activity of the visceral organs can depend on the activity and the size of the organ (Ferrel et al., 1986).
5. Conclusions Energy dilution as a result of including hay in the ®nishing ration did result in an increase in DM intake in lambs. Nevertheless, it did not improve productive performance or carcass characteristics.