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Growth performance by Alpine, Angora, Boer and Spanish wether goats consuming 50 or 75% concentrate diets
Small Ruminant Research 55 (2004) 149–158
Growth performance by Alpine, Angora, Boer and Spanish wether goats consuming 50 or 75% concentrate diets M. Urge a,b , R.C. Merkel b , T. Sahlu b , G. Animut a , A.L. Goetsch b,∗ a
b
Animal Science Department, Alemaya University, Dire Dawa, Ethiopia E (Kika) de la Garza American Institute for Goat Research, Langston University, P.O. Box 730, Langston, OK 73050, USA Received 12 May 2003; received in revised form 23 December 2003; accepted 13 February 2004
Abstract Forty-five weaned wether goats (12 Alpine, 12 Angora, 10 Boer (87.5%) and 11 Spanish) were used to determine effects on growth performance of consumption of a 75% concentrate diet (DM basis) for 24 weeks (75C) or for 12 weeks subsequent to 12 weeks of feeding a 50% concentrate diet (50C). Initial BW was 20.2, 12.2, 20.7 and 19.2 kg (S.E. = 0.73) for Alpine, Angora, Boer and Spanish, respectively, and age was 4 months when the experiment began. There were no interactions between genotype and dietary treatment in DM intake, ADG or gain efficiency in weeks 1–12 or 13–24. DM intake in weeks 1–12 ranked Alpine and Boer > Spanish > Angora (703, 689, 567 and 436 g per day; P < 0.05) and in weeks 13–24 was significantly greater for Alpine and Boer versus Angora and Spanish (712, 702, 515 and 456 g per day; P < 0.05). DM intake was similar between dietary treatments. In week 8, OM digestibility was 79.3 and 71.3% (S.E. = 1.57) and NDF digestibility was 54.2 and 52.1% (S.E. = 3.46) for 75C and 50C, respectively. Total VFA concentration was similar between diets; the acetate:propionate ratio was greater (P < 0.05) for 50C versus 75C (4.12 versus 2.56). ADG in weeks 1–12 was greatest (P < 0.05) for Boer (59, 59, 90 and 49 g per day for Alpine, Angora, Boer and Spanish, respectively); in weeks 13–24 ADG was lowest (P < 0.05) for Spanish (25 g per day) and tended to be greater (P < 0.10) for Boer versus Alpine (82 versus 58 and 63 g per day). Gain efficiency (ADG:DM intake) was greater (P < 0.05) for Angora and Boer than for Alpine and Spanish in weeks 1–12 (132 and 127 versus 85 and 85 g/kg), and in weeks 13–24 was lower (P < 0.05) for Spanish than for Angora and Boer (80, 121, 104 and 51 g/kg for Alpine, Angora, Boer and Spanish, respectively). ADG and gain efficiency were greater (P < 0.05) for 75 versus 50% dietary concentrate in weeks 1–12 (ADG: 73 and 55 g per day; gain efficiency: 122 and 92 g/kg), and tended to be greater (P < 0.11) for 50C than for 75C in weeks 13–24 (ADG: 49 and 65 g per day; gain efficiency: 77 and 101 g/kg for 75C and 50C, respectively). In conclusion, differences in growth performance among Alpine, Angora, Boer and Spanish wether goats were similar with 50 and 75% concentrate diets, and the genotypes responded similarly to the change in dietary concentrate level from 50 to 75%. © 2004 Elsevier B.V. All rights reserved. Keywords: Goat; Growth performance; Dietary concentrate level
1. Introduction
∗ Corresponding author. Tel.: +1-405-466-3836; fax: +1-405-466-3138. E-mail address: [email protected] (A.L. Goetsch).
There are many different types of goats in the world used for a variety of purposes. In the US a logical and common categorization of goats is one bred for high milk production (e.g., Alpine), mohair fiber growth
0921-4488/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.smallrumres.2004.02.004
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(e.g., Angora) or meat production (e.g., Boer), as well as one that has not been intensively selected (e.g., Spanish) but that nonetheless serves useful purposes such as supplying meat and cashmere and vegetation management. How these different types of goats respond to various feeding management practices, such as dietary concentrate level, is not well understood. After a low or moderate plane of nutrition, when placed on a higher plane the level and/or efficiency of growth by cattle and sheep is often greater than expected based on nutrients consumed, which is known as compensatory growth. General factors responsible for compensatory growth are increased feed intake relative to BW and more efficient energy and/or protein metabolism (Drouillard et al., 1991). Compensatory growth does occur in goats (e.g., Havrevoll et al., 1995; Wuliji et al., 2003; Joemat et al., 2004), but potential differences in responses among genotypes have not been extensively studied. Knowledge of the capacity of goats for compensatory growth is necessary to achieve desired levels of performance while maximizing use of typically abundant and inexpensive forages. Therefore, objectives of this experiment were to determine effects of moderate and high dietary levels of concentrate (i.e., 50 and 75%, respectively) and a high level subsequent to a moderate one on growth performance by Alpine, Angora, Boer and Spanish wether goats. 2. Materials and methods 2.1. Experimental design and treatments The treatment arrangement was a 4 × 2 factorial, with four genotypes and two dietary treatments. Twelve Alpine, 12 Angora, 10 Boer (87.5% Boer and 12.5% Spanish) and 12 Spanish wether goats were used, with five (Boer) or six of each assigned to the two dietary treatments for similar mean BW and variation in BW within genotype. Wethers were approximately 4 months of age when the experiment began, having been weaned 1–2 months earlier. Housing was individually in 1.1 m × 1.2 m pens with plastic-coated expanded metal floors and free access to nipple waterers. Wethers were treated for internal parasites (Valbazen® ; SmithKline Beecham Animal Health, West Chester, PA) at the start of the experiment. The experiment was 24 weeks in length, divided into two
Table 1 Composition of diets for growing Alpine, Angora, Boer and Spanish wether goats Item
Ingredient composition (%DM) Coarsely ground prairie hay Ground corn Soybean meal Blood meal Fish meal Feather meal Dried molasses product Trace mineralized salta Vitamin premixb Deccoxc Limestone Dicalcium phosphate Chromic oxide Salt Chemical composition (%DM) Offered Ash CP NDF Consumed Phase 1 Ash CP NDF Phase 2 Ash CP NDF Calculatedd ME (Mcal/kg DM) TDN (%DM) CP (%DM)
Diet (%concentrate, DM basis) 75
50
25.00 55.98 6.06 2.07 2.56 2.07 3.00 0.75 0.50 0.05 1.06 0.10 0.30 0.50
50.00 29.40 6.82 2.50 3.20 2.50 3.00 0.75 0.50 0.05 0.63 0.10 0.30 0.25
6.1 18.6 25.6
7.1 17.5 38.8
4.6 15.9 25.1
6.0 15.6 37.8
4.0 13.4 25.6 2.70 71.0 17.0
2.37 62.4 17.0
a Contained 95–98% NaCl and at least 0.24% Mn, 0.24% Fe, 0.05% Mg, 0.032% Cu, 0.011% Co, 0.007% I and 0.005% Zn. b Contained 2200 IU/g vitamin A, 1200 IU/g vitamin D and 3 2.2 IU/g vitamin E. c Rhˆ one Poulenc, Atlanta, GA; 6% decoquinate. d Based on Preston (2000).
12-week phases. Dietary treatments consisted of offering 75 or 50% (DM basis) concentrate diets (75C and 50C, respectively; Table 1) in phase 1, followed by the 75% concentrate diet in phase 2. On the first day of the diet change, the amount of feed offered was decreased by approximately 10%, with gradual
M. Urge et al. / Small Ruminant Research 55 (2004) 149–158
increases in the first week. Concentrate and coarsely ground hay were weighed into feeding containers separately and then were hand-mixed. Feed was offered at approximately 110% of consumption on the preceding few days. There was one meal daily at 09:00 h, subsequent to removal and weighing of feed refusals. In a 2-week period before the experiment, the dietary concentrate level for all goats was gradually increased to 75%. No digestive upsets were noted during the experiment, and there were no observations of abnormal appearance of feces. 2.2. Measures and samples Wethers were weighed every 3 weeks. DM intake and ADG in the four 3-week periods of each phase were averaged to determine phase means. Phase means for DM intake and ADG were employed to estimate gain efficiency (ADG:DM intake (g/kg)). Diets and feed refusals were sampled daily and used to form composite samples for each phase. During week 8 of phase 1, wire screens were placed under pen floors to allow for once daily sampling of most feces excreted to form composite samples. Ruminal fluid was obtained via stomach tube on the last day of week 8 in both phases; 5 ml was placed into a tube containing 1 ml of 25% (w/v) metaphosphoric acid for later analysis of volatile fatty acids (Lu et al., 1990) and 3 ml was dispensed into another tube that had 2 ml of 3N HCl for determining ammonia N concentration (Broderick and Kang, 1980). Diet, feed refusal and fecal samples were first dried at 55 ◦ C for determination of partial DM concentration. Thereafter, samples of hay, feed refusals and feces were ground to pass a 1 mm screen, followed by analysis of these samples and concentrates for DM (100 ◦ C), ash, Kjeldahl N (AOAC, 1990) and NDF (filter bag technique; ANKOM Technology Corp., Fairport, NY). Chromium concentration was determined (Williams et al., 1962) in diet, refusal and fecal samples; chromium was used as an inert, external marker to determine digestibility (Cochran and Galyean, 1994). 2.3. Statistical analyses Data from one Spanish wether that experienced urinary calculi problems in the later part of the ex-
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periment were omitted from statistical analyses. DM intake, ADG and ADG:DM intake were initially analyzed as a split-plot in time via mixed model analysis (Littell et al., 1996), with a repeated measure of phase and random effect of animal. Interactions involving phase were noted (P < 0.01) in DM intake as g per day (genotype × phase), ADG (dietary treatment × phase) and ADG:DM intake (dietary treatment × phase). Therefore, data were analyzed by phase with general linear models procedures of SAS (1990), with a model consisting of genotype, dietary treatment and the genotype × dietary treatment interaction. Main effect means were presented when the interaction was nonsignificant. Differences among means were determined by least significant difference with a protected F-test (P < 0.05). In order to facilitate possible use of these data by future researchers combining data from several experiments, dietary treatment × genotype interaction means were presented regardless of significance of the interaction (JAS, 2002).
3. Results 3.1. Diet composition Diets were formulated to be 17% CP (DM basis). Slightly greater concentrations of CP in DM offered may have been because of greater than expected CP levels in some ingredients or inconsistencies in diet mixing or sampling (Table 1). The concentration of CP in DM consumed was less than in DM offered, suggesting selection against high-CP feedstuffs perhaps of low palatability such as blood, feather and fish meals. Concentrations of NDF in DM consumed were similar to those in DM offered, reflecting little selection for or against prairie hay. 3.2. DM intake DM intake as g per day in phase 1 ranked (P < 0.05) Alpine and Boer > Spanish > Angora (Table 2). In phase 2, DM intake as g per day was significantly greater for Alpine and Boer versus Angora and Spanish. Dietary treatment did not affect DM intake in phase 1 or 2. DM intake as %BW in phase 1 was similar among genotypes. In phase 2, DM intake as %BW ranked (P < 0.05) Alpine and Angora > Boer >
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Table 2 Effects of dietary concentrate level (%) on DM intake, BW, ADG and ADG:DM intake by growing Alpine, Angora, Boer and Spanish wether goatsa Item
DM intake (g per day)
12-week phaseb
Diet (%)
1
BW (kg)
Angora
Boer
Spanish
75 50 Mean
659 746 703 c
474 398 436 a
656 721 689 c
585 550 567 b
45.0
75 50 Mean
688 736 712 b
494 636 515 a
643 761 702 b
447 466 456 a
42.7
1
75 50 Mean
2.87 3.33 3.10
3.00 2.92 2.96
2.56 3.01 2.79
2.61 2.73 2.67
0.165
2
75 50 Mean
2.44 2.80 2.62 c
2.36 2.88 2.62 c
2.00 2.43 2.22 b
1.72 2.07 1.90 a
0.123
75 50 Mean
20.0 20.3 20.2 b
12.6 11.8 12.2 a
21.2 20.2 20.7 b
19.8 18.7 19.2 b
1.03
75 50 Mean
25.7 24.5 25.1 b
18.6 15.7 17.2 a
28.8 27.7 28.3 c
24.9 21.7 23.3 b
1.16
2, end
75 50 Mean
30.7 29.4 30.0 b
22.8 22.0 22.4 a
34.2 36.1 35.2 c
26.8 24.0 25.4 a
1.53
1
75 50 Mean
68 50 59 a
72 46 59 a
91 90 90 b
62 36 49 a
10.9
75 50 Mean
59 57 58 b
50 75 63 b
64 100 82 b
22 28 25 a
13.9
1
75 50 Mean
103 67 85 a
148 115 132 b
133 121 127 b
105 64 85 a
14.3
2
75 50 Mean
82 78 80 ab
99 142 121 b
83 126 104 b
43 59 51 a
21.0
Initial
1, end
ADG (g)
2
ADG:DM intake (g/kg)
S.E.
Alpine
2
DM intake (%BW)
Genotype
31.9
30.2
0.117
0.087
0.73
0.82
1.08
7.7
9.6
10.1
14.8
Dietc
S.E.
75
50
593
604
22.6
568
625
21.4
2.76 a
3.00 b
0.083
2.13 a
2.54 b
0.062
18.4
17.8
0.52
24.5 b
22.4 a
0.58
28.6
27.9
0.77
73 b
55 a
5.5
49
65
6.8
122 b
92 a
7.2
77
101
10.5
Means within a mean row without a common letter differ (P < 0.05). a n = 6, 6, 5 and 5 or 6 (per dietary treatment) for Alpine, Angora, Boer and Spanish, respectively. b Wether goats on both diets received the 75% concentrate diet in phase 2. c 75 = 75% concentrate; 50 = 50% concentrate.
Spanish, and in phases 1–2 was significantly greatest among treatments for Alpine and Angora and tended to be greater (P < 0.07) for Boer versus Spanish. In both phases and the entire experiment, DM intake as %BW was significantly greater for 50C than for 75C.
3.3. BW, ADG and ADG: DM intake Initial BW was significantly lowest among treatments for Angora (Table 2). BW at the end of phase 1 ranked Boer > Spanish and Alpine > Angora. The
M. Urge et al. / Small Ruminant Research 55 (2004) 149–158
genotype ranking at the end of phase 2 was similar, Boer > Alpine > Angora and Spanish (P < 0.05), although BW tended (P < 0.10) to be greater for Spanish versus Angora. BW was significantly greater for 75 versus 50% concentrate after phase 1 but was similar between dietary treatments at the beginning and end of the experiment. In phase 1, Boer wethers gained significantly faster than other genotypes, which were similar (Table 2). In phase 2, ADG of Spanish goats was significantly
153
lowest, and Boer wethers tended (P < 0.07) to gain BW more rapidly than Alpines. ADG in phase 1 was significantly greater for the 75 versus 50% concentrate diet, although there was a tendency (P < 0.10) for greater ADG in phase 2 for 50C than for 75C. Gain efficiency (ADG:DM intake) was significantly greater for Angora and Boer than for Alpine and Spanish in phase 1 (Table 2). In phase 2, gain efficiency was significantly lower for Spanish than for Angora and Boer, with that for Alpine being intermediate (P >
Table 3 Effects of dietary concentrate level on intake and digestion by growing Alpine, Angora, Boer and Spanish wether goatsa Item
Diet (%)
Genotype
S.E.
Alpine
Angora
Boer
Spanish
75 50
637 bc 769 c
558 b 422 a
697 bc 769 c
573 b 557 ab
50.0
75 50
608 bcd 728 d
534 b 397 a
667 cd 726 d
552 bc 526 b
46.5
75 50 Mean
75.1 69.7 72.4
79.4 69.3 74.3
79.2 72.7 76.0
83.6 73.6 78.6
75 50 Mean
468 502 485 bc
425 272 349 a
525 524 524 c
459 388 423 b
37.3
75 50
169 abc 307 d
127 a 141 ab
179 bc 299 d
147 ab 222 c
16.2
Digestibility (%)
75 50 Mean
48.6 52.5 50.6
50.3 42.7 46.5
55.0 55.7 55.4
62.7 57.3 60.0
Digested (g per day)
75 50 Mean
87 159 123 b
67 59 63 a
98 166 132 b
91 128 110 b
Intake (g per day)
75 50 Mean
15.9 17.1 16.5 b
14.3 11.1 12.7 a
17.0 17.8 17.4 b
12.9 12.3 12.6 a
1.93
Digestibility (%)
75 50 Mean
57.5 60.5 59.0
70.0 60.7 65.4
68.2 65.0 66.6
73.5 61.0 67.3
4.41
75 50 Mean
10.0 10.1 10.1
10.0 6.8 8.4
11.4 11.4 11.4
9.4 7.6 8.5
1.43
DM intake (g per day) OM Intake (g per day) Digestibility (%)
Digested (g per day)
NDF Intake (g per day)
Dietb
S.E.
75
50
79.3 b
71.3 a
469
421
54.2
52.1
3.46
86 a
128 b
8.1
15.0
14.6
0.97
67.3
61.8
2.21
10.2
9.0
0.72
3.14 2.22
26.6
1.57
18.7
6.92 4.90 16.3 11.5
N
Digested (g per day)
Means for 75 and 50% diets or within a mean row without a common letter differ (P < 0.05). a Determined in week 8 of the 12-week phase 1. b 75 = 75% concentrate; 50 = 50% concentrate.
1.37
3.12
1.00
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M. Urge et al. / Small Ruminant Research 55 (2004) 149–158
Table 4 Effects of dietary concentrate level on ruminal VFA and ammonia N concentrations in growing Alpine, Angora, Boer and Spanish wether goats Weeka
Item
Diet (%)
Genotype Alpine
Angora
Boer
Spanish
8
Total VFA (mM/l)
75 50 Mean
64.7 71.1 67.9
63.6 68.8 66.2
60.4 67.8 64.1
59.6 71.6 65.6
5.61
75 50 Mean
63.7 72.1 67.9 c
53.3 64.1 58.7 a
60.0 66.9 63.5 b
57.7 70.2 64.0 b
1.88
Propionate (mol%)
75 50
20.5 a 17.1 a
32.0 b 20.6 a
20.9 a 18.3 a
27.8 b 16.1 a
1.82
Isobutyrate (mol%)
75 50 Mean
0.51 0.17 0.34
0.24 0.22 0.23
0.49 0.34 0.42
0.49 0.21 0.35
0.086
Butyrate (mol%)
75 50 Mean
12.4 9.6 11.0 a
11.9 13.6 12.8 ab
16.2 13.1 14.7 b
11.9 12.5 12.2 ab
1.26
Isovalerate (mol%)
75 50 Mean
1.69 0.43 1.06
1.42 0.92 1.17
1.22 0.51 0.86
1.01 0.39 0.70
0.315
75 50 Mean
1.23 0.63 0.93
1.16 0.62 0.89
1.22 0.77 0.99
1.06 0.58 0.82
0.151
75 50 Mean
3.42 4.24 3.83
1.71 3.31 2.51
3.00 3.79 3.40
2.12 5.16 3.64
0.579
Ammonia (mg/dl)
75 50 Mean
12.1 12.2 12.2 c
10.5 11.1 10.8 bc
6.2 6.3 6.3 a
7.7 6.4 7.0 ab
2.04
Total VFA (mM/l)
75 50 Mean
40.5 42.3 41.3
38.3 42.5 40.4
37.9 44.4 41.1
39.2 43.4 41.3
3.93
75 50 Mean
57.7 54.2 56.0
51.6 59.4 55.5
55.7 57.3 56.5
47.1 56.5 51.8
4.25
Propionate (mol%)
75 50 Mean
23.6 28.3 26.0
25.8 24.0 24.9
22.5 26.9 24.7
31.6 24.7 28.1
3.91
Isobutyrate (mol%)
75 50 Mean
0.55 0.83 0.68
0.54 0.61 0.58
0.60 0.61 0.60
0.73 0.64 0.68
0.126
75 50 Mean
12.2 13.2 12.7
18.4 12.8 15.6
15.6 11.2 13.4
15.0 12.6 13.8
3.38
75 50 Mean
4.17 2.01 3.09
2.15 1.82 1.98
3.33 2.49 2.91
3.37 3.31 3.34
1.051
Acetate (mol%)
Valerate (mol%)
Acetate:propionate
20
Acetate (mol%)
Butyrate (mol%)
Isovalerate (mol%)
S.E.
3.97
1.33
0.061
0.89
0.223
0.107
0.410
1.45
2.78
3.01
2.77
0.089
2.392
0.740
Dietb
S.E.
75
50
62.1
69.8
2.81
58.7 a
68.3 b
0.94
0.43 b
0.24 a
0.043
13.1
12.2
0.63
1.33 b
0.56 a
0.158
1.17 b
0.65 a
0.076
2.56 a
4.12 b
0.290
9.2
9.0
1.02
38.9
43.2
1.97
53.0
56.8
2.13
25.9
26.0
1.96
0.60
0.67
0.063
15.3
12.4
1.69
3.26
2.41
0.526
M. Urge et al. / Small Ruminant Research 55 (2004) 149–158
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Table 4 (Continued ). Weeka
Item
Diet (%)
Genotype
S.E.
Alpine
Angora
Boer
Spanish
75 50 Mean
1.76 1.42 1.59
1.50 1.41 1.46
2.31 1.57 1.94
2.13 2.27 2.20
0.481
Acetate:propionate
75 50 Mean
2.76 2.36 2.56
2.17 2.68 2.43
2.72 2.58 2.65
1.75 2.40 2.08
0.450
Ammonia (mg/dl)
75 50
10.6 abc 6.1 a
9.8 abc 9.9 abc
7.1 ab 14.2 c
5.8 a 11.5 bc
1.94
Valerate (mol%)
0.340
0.319
Dietb
S.E.
75
50
1.93
1.67
0.241
2.35
2.51
0.225
Means within a row without a common letter differ (P < 0.05). a The two phases were 12 weeks in length. 50 and 75% diets were fed in phase 1 and all wether goats received the 75% diet in phase 2. b 75 = 75% concentrate; 50 = 50% concentrate.
0.10). Gain efficiency was significantly greater for 75C than for 50C in phase 1, with an opposite numerical difference in phase 2. 3.4. Digestibility There were significant interactions between genotype and dietary treatment in intake of DM, OM and NDF during week 8 of phase 1 when digestibilities were determined (Table 3). Although a comparable interaction in DM intake during all of phase 1 was not significant, numerically interaction means were similar. DM intake in week 8 of phase 1 was similar among genotypes with 75% concentrate, but with 50% concentrate DM intake was significantly greatest among genotypes for Alpine and Boer. Within genotypes, DM intake was similar between diets for Alpine, Boer and Spanish but was significantly lower for 50 versus 75% concentrate for Angora. Similar differences existed in OM intake. NDF intake was significantly greater for 50% concentrate than for 75% for Alpine, Boer and Spanish but for Angora was similar between diets. Apparent total tract OM digestibility was similar among genotypes and significantly greater for 75 versus 50% concentrate (Table 3). OM digestibilities were slightly greater than expected based on calculated TDN concentration, suggesting greater digestibility of prairie hay than the assumed literature value. Digestible OM intake was lowest among genotypes (P < 0.05) for Angora and significantly greater for Boer versus Spanish, with that for Alpine intermediate (P > 0.10) to values for Boer and Spanish.
Total tract NDF digestibility was similar among genotypes and between diets (Table 3). Among genotypes, digestible NDF intake was significantly lowest among genotypes for Angora and was significantly greater for 50 versus 75% concentrate. Apparent total tract N digestibility and digestible N intake were similar among genotypes and between dietary concentrate levels. 3.5. Ruminal fluid VFA and ammonia N The concentration of total VFA in ruminal fluid in phase 1 was similar among genotypes and between diets (Table 4). The molar percentage of acetate ranked (P < 0.05) Alpine > Boer and Spanish > Angora and was significantly greater for 50 versus 75% concentrate. There was a significant interaction between genotype and dietary concentrate level in molar percentage of propionate, which was significantly greater for Angora and Spanish than for Alpine and Boer with 75% dietary concentrate but similar among genotypes with 50%. The acetate:propionate ratio was similar among genotypes and significantly greater for 50% dietary concentrate than for 75%. The molar percentage of butyrate was significantly greater for Boer than for Alpine. Genotype did not affect molar percentages of isobutyrate, isovalerate or valerate, which were significantly greater for 75 versus 50% concentrate. Ammonia N concentration in phase 1 was significantly greater for Alpine than for Boer and Spanish and significantly greater for Angora versus Boer.
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In phase 2, there were no differences among genotypes or between dietary treatments in ruminal VFA measures (Table 4). However, a significant interaction between genotype and dietary treatment occurred in ammonia N concentration. Ammonia N concentration was significantly greater with the 50 versus 75% dietary concentrate treatment for Boer and Spanish but was similar between dietary treatments for Alpine and Angora. 4. Discussion 4.1. Genotype Greater ADG by growing Boer than Spanish and Angora goats agrees with results of other studies involving full-blood or crossbred Boer goats (Casey and Van Niekirk, 1988; Van Niekirk and Casey, 1988; Waldron et al., 1995, 1996; Lewis et al., 1997; Luo et al., 2000; Prieto et al., 2000; Cameron et al., 2001; Joemat et al., 2004), although similar comparisons of Boer goats and dairy goat breeds such as Alpine and of full-blood Angora versus Spanish are not available. Greater overall ADG by Angora than Spanish wethers in the present experiment may reflect little genetic selection of Spanish goats for growth performance and breeding of Angoras for high mohair fiber growth. However, a similar difference in ADG between Angora and Spanish goats does not seem likely with a limited nutritional plane that would restrict fiber growth and/or result in appreciable partitioning of nutrients by Angora goats for fiber growth at the expense of other peripheral tissues (Cronjé, 2000; Joemat et al., 2003). The lack of interaction in ADG between genotype and dietary treatment in phase 1 implies that level of concentrate in moderate- to high-quality diets impacts early postweaning growth similarly regardless of genotype. Conversely, in some cases greater growth potential of crossbred Boer goats compared with indigenous or local genotypes has only been realized with high-quality diets or has been expressed to a greater extent with high-quality versus low- or moderate-quality diets (Huston and Waldron, 1996; Roeder et al., 1997; Negesse et al., 2001; Joemat et al., 2004). This was not observed in the present experiment perhaps because the 50% concentrate level was above a diet quality threshold.
Angora wethers were as efficient in converting dietary energy into mass of tissue plus mohair fiber as Boer goats were into tissue mass, although rate of gain by Angoras was relatively low. The lower gain efficiency for Alpine compared with Angora and Boer, and greatest DM intake as g/kg BW0.75 in the 24-week experiment for Alpine suggest a higher MEm (i.e., 19%) of growing dairy goats than of other breeds (Luo et al., 2004). However, Luo et al. (2004) also estimated an MEg requirement of growing indigenous goats 14% lower than for dairy goats or ones with 50% or more Boer breeding. This disparity may be partially reconciled by lowest DM intake as g/kg BW0.75 for Spanish, which would have resulted in a large proportion of energy consumed being used for maintenance and little for growth. 4.2. Dietary treatment The difference between dietary concentrate levels in total tract OM digestibility was expected because of greater digestibility of concentrate than forage. Also, greater DM intake as %BW for 50 than 75% concentrate suggests shorter digest retention in the rumen for 50% concentrate, which may have lessened the difference in digestion relative to a set level of intake. Greater ADG for 75% dietary concentrate than for 50% in phase 1 was anticipated based on findings with other ruminant species as well as with young Alpine doelings (Goetsch et al., 2003). Although, ADG for both dietary treatments was slightly less than expected based on forage composition and levels of dietary concentrate. The feeding protocol employed, to minimize feed refusals, may have resulted in DM intake and ADG less than with a greater feeding rate. Nonetheless, these results differ somewhat from findings of Morand-Fehr and Sauvant (1978) that with lactating dairy goats there is little or no production advantage in use of dietary concentrate levels above 50%, as generally occurs with dairy and beef cattle. Overall, results of the present experiment indicate that growth of young goats consuming offered diets for minimal feed refusals can be enhanced by increases in dietary concentrate level up to at least 75%, not because of increased feed intake but rather via greater efficiency of use of ME from concentrate versus forage. Compensatory growth in phase 2 was partially a function of greater DM intake relative to BW and
M. Urge et al. / Small Ruminant Research 55 (2004) 149–158
BW0.75 . However, the tendency for greater gain efficiency in phase 2 with 50C versus 75C, resulting in similar overall gain efficiency in the 24-week experiment, also indicates more efficient energy metabolism such as via decreased MEm in the early weeks of compensation (Silanikove, 2000). The lack of interaction between genotype and dietary treatment in phase 2 DM intake, ADG and gain efficiency do not suggest appreciable differences among genotypes in compensatory growth potential. These results are in slight contrast to those of Joemat et al. (2004). In that study a low nutritional plane (prairie hay without supplemental concentrate) for 56 days restricted ADG by yearling Boer × Spanish doelings but not by Spanish, resulting in compensation only by Boer × Spanish. Thus, conditions such as animal age, as affecting nutrient needs, and degree and length of nutrient restriction will influence the existence and magnitude of compensatory growth by goats. It is common in beef cattle production systems to take advantage of compensatory growth, such as with wintering on low-quality forage preceding consumption of high-quality spring forage or placement in feedlots with high-concentrate diets after backgrounding on forage-based diets. Such strategies are designed in part to maximize reliance on typically abundant and relatively inexpensive forages and minimize use of more costly concentrate feedstuffs. In this regard, during the entire experiment total concentrate and forage DM intake was 73.2 and 24.4 kg for 75C and 64.8 and 38.5 kg for 50C, respectively. Hence, 8.4 kg less concentrate and 14.1 kg more forage per animal were consumed by 50C versus 75C wethers, with the end result of similar final BW. In terms of feed costs, for the 50C treatment to be economically advantageous, the expense of forage would need to be less than 60% (i.e., 8.4 kg concentrate/14.1 kg forage) of that of concentrate.
5. Summary and conclusions These results indicate that differences in growth performance among Alpine, Angora, Boer and Spanish wether goats are not influenced by dietary concentrate level in the range 50–75%. With growth limited by use of a 50% dietary level of concentrate, capacity for compensatory growth by growing Alpine, Angora,
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Boer and Spanish wether goats appears similar when shifted to a 75% concentrate diet.
Acknowledgements This research was supported by the Institutional Development Partnership Program of the United Negro College Fund/United States Agency for International Development and the resulting partnership between Langston University, Langston, OK, and Alemaya University, Dire Dawa, Ethiopia. Appreciation is expressed to farm and laboratory personnel of the E (Kika) de la Garza American Institute for Goat Research for their assistance. References AOAC, 1990. Official Methods of Analysis, 15th ed. Association of Official Analytical Chemists, Washington, DC. Broderick, G.A., Kang, J.H., 1980. Automated simultaneous determination of ammonia and total amino acids in rumen fluid and in vitro media. J. Dairy Sci. 63, 64–75. Cameron, M.R., Luo, J., Sahlu, T., Hart, S.P., Coleman, S.W., Goetsch, A.L., 2001. Growth and harvest traits of Boer × Spanish, Boer × Angora, and Spanish goats consuming a concentrate-based diet. J. Anim. Sci. 79, 1423–1430. Casey, N.H., Van Niekirk, W.A., 1988. The Boer goat. I. Origin, adaptability, performance testing, reproduction and milk production. Small Rum. Res. 1, 291–295. Cochran, R.C., Galyean, M.L., 1994. Measurement of in vivo forage digestion by ruminants. In: Fahey Jr., G.C. (Ed.), Forage Quality, Evaluation, and Utilization. Am. Soc. Agron., Crop Sci. Soc. Am., Soil Sci. Soc. Am., Madison, WI, pp. 613–643. Cronjé, P.B., 2000. Nutrient–gene interactions: future potential and applications. In: Cronjé, P.B. (Ed.), Ruminant Physiology. Digestion, Metabolism, Growth and Reproduction. CABI Publishing, New York, NY, pp. 409–422. Drouillard, J.S., Klopfenstein, T.J., Britton, R.A., Bauer, M.L., Gramlich, S.M., Wester, T.J., Ferrell, C.L., 1991. Growth, body composition, and visceral organ mass and metabolism in lambs during and after metabolizable protein or net energy restrictions. J. Anim. Sci. 69, 3357–3375. Goetsch, A.L., Detweiler, G., Sahlu, T., Hayes, J., Puchala, R., 2003. Effects of separate offering of forage and concentrate on feed intake and growth of Alpine doelings. Small Rum. Res. 48, 209–216. Havrevoll, Ø., Rajbhandari, S.P., Eik, L.O., Nedkvitne, J.J., 1995. Effects of different energy levels during indoor rearing on performance of Norwegian dairy goats. Small Rum. Res. 15, 231–237. Huston, J.E., Waldron, D.F., 1996. Comparative growth rates of Angora, Spanish, and Boer cross kids fed various
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diets. In: Proceedings of the Southeast Regional Meat Goat Production Symposium. Florida A&M University, Tallahassee, FL, pp. 21–23. JAS, 2002. Journal of Animal Science Style and Form (Revised 2002). J. Anim. Sci. 80, 279–293. Joemat, R., Goetsch, A.L., Horn, G.W., Sahlu, T., Puchala, R., Min, B.R., Luo, J., 2004. Growth of yearling meat goat doelings with changing plane of nutrition. Small Rum. Res., doi:10.1016/S0921-4488(03)00252-9, in press. Joemat, R., Goetsch, A.L., Wuliji, T., Horn, G.W., Sahlu, T., Puchala, R., Merkel, R.C., Soto-Navarro, S., 2003. Effects of frequency of supplementation with soybean meal and litter size on performance of Angora does consuming low quality forage in late gestation and early lactation. J. Anim. Feed Sci. 12, 707–722. Lewis, S.J., May, B.J., Engdahl, G.R., Waldron, D.F., Scott, C.B., Shelby, D.R., 1997. Feedlot performance and carcass traits of Boer goat crosses and Spanish male kids. J. Anim. Sci. 7540 (Suppl. 1), 40. Littell, R.C., Milliken, G.A., Stroup, W.W., Wolfinger, R.D., 1996. SAS System for Mixed Models. SAS Institute Inc., Cary, NC. Lu, C.D., Potchoiba, M.J., Sahlu, T., Fernandez, J.M., 1990. Performance of dairy goats fed isonitrogenous diets containing soybean meal or hydrolyzed feather meal during early lactation. Small Rum. Res. 3, 425–434. Luo, J., Goetsch, A.L., Sahlu, T., Nsahlai, I.V., Johnson, Z.B., Moore, J.E., Galyean, M.L., Owens, F.N., Ferrell, C.L., 2004. Prediction of metabolizable energy requirements for maintenance and gain of preweaning, growing, and mature goats. Small Rum. Res., PII: S0921-4488(04)00027-6, doi:10.1016/j.smallrumres.2004.01.003, in press. Luo, J., Sahlu, T., Cameron, M., Goetsch, A.L., 2000. Growth of Spanish, Boer × Angora and Boer × Spanish goat kids fed milk replacer. Small Rum. Res. 36, 189–194. Morand-Fehr, P., Sauvant, D., 1978. Nutrition and optimum performance of dairy goats. Livest. Prod. Sci. 5, 203–213. Negesse, T., Merkel, R.C., Tolera, A., Goetsch, A.L., Sahlu, T., Puchala, R., Gipson, T.A., Dawson, L.J., 2001. Feed intake and
growth by Spanish and Boer×Spanish doelings consuming diets with different levels of broiler litter. J. Anim. Sci. 79 (Suppl. 1), 448. Preston, R.L., 2000. Typical composition of feeds for cattle and sheep. Beef 36 (10), 10–20. Prieto, I., Goetsch, A.L., Banskalieva, V., Cameron, M., Puchala, R., Sahlu, T., Dawson, L.J., Coleman, S.W., 2000. Effects of dietary protein concentration on postweaning growth of Boer crossbred and Spanish goat wethers. J. Anim. Sci. 78, 2275– 2281. Roeder, B.W., Ramsey, W.S., Hafley, B., Miller, R.L., Davis, E., Machen, R., 1997. Differences in growth, carcass, and sensory characteristics of young goats of different genotypes. J. Anim. Sci. 75 (Suppl. 1), 271. SAS, 1990. SAS User’s Guide, Version 6, vol. 2, 4th ed. SAS Inst. Inc., Cary, NC. Silanikove, N., 2000. The physiological basis of adaptation in goats to harsh environments. Small Rum. Res. 35, 181–194. Van Niekerk, W.A., Casey, N.H., 1988. The Boer goat. II. Growth, nutrient requirements, carcass and meat quality. Small Rum. Res. 1, 355–368. Waldron, D.F., Huston, J.E., Thompson, P., Willingham, T.D., Oman, S., Savell, J.W., 1995. Growth rate, feed consumption and carcass measurements of Spanish and Boer×Spanish goats. J. Anim. Sci. 73, 253. Waldron, D.F., Willingham, T.D., Thompson, P.W., Huston, J.E., 1996. Growth rate and feed efficiency of Boer × Spanish compared to Spanish goats. In: Sheep and Goats, Wool and Mohair. Research Rep. No. CPR-5257. Texas Agric. Exp. Sta., College Station, TX, pp. 12–15. Williams, C.H., David, D.J., Iismaa, O., 1962. The determination of chromic oxide in faeces samples by atomic absorption spectrophotometry. J. Agric. Sci. 59, 381–389. Wuliji, T., Goetsch, A.L., Sahlu, T., Puchala, R., Soto-Navarro, S., Merkel, R.C., Detweiler, G., Gipson, T., 2003. Effects of different quality diets consumed continuously or after a lower quality diet on characteristics of growth of young Spanish goats. Small Rum. Res. 50, 83–96.
Growth performance by Alpine, Angora, Boer and Spanish wether goats consuming 50 or 75% concentrate diets M. Urge a,b , R.C. Merkel b , T. Sahlu b , G. Animut a , A.L. Goetsch b,∗ a
b
Animal Science Department, Alemaya University, Dire Dawa, Ethiopia E (Kika) de la Garza American Institute for Goat Research, Langston University, P.O. Box 730, Langston, OK 73050, USA Received 12 May 2003; received in revised form 23 December 2003; accepted 13 February 2004
Abstract Forty-five weaned wether goats (12 Alpine, 12 Angora, 10 Boer (87.5%) and 11 Spanish) were used to determine effects on growth performance of consumption of a 75% concentrate diet (DM basis) for 24 weeks (75C) or for 12 weeks subsequent to 12 weeks of feeding a 50% concentrate diet (50C). Initial BW was 20.2, 12.2, 20.7 and 19.2 kg (S.E. = 0.73) for Alpine, Angora, Boer and Spanish, respectively, and age was 4 months when the experiment began. There were no interactions between genotype and dietary treatment in DM intake, ADG or gain efficiency in weeks 1–12 or 13–24. DM intake in weeks 1–12 ranked Alpine and Boer > Spanish > Angora (703, 689, 567 and 436 g per day; P < 0.05) and in weeks 13–24 was significantly greater for Alpine and Boer versus Angora and Spanish (712, 702, 515 and 456 g per day; P < 0.05). DM intake was similar between dietary treatments. In week 8, OM digestibility was 79.3 and 71.3% (S.E. = 1.57) and NDF digestibility was 54.2 and 52.1% (S.E. = 3.46) for 75C and 50C, respectively. Total VFA concentration was similar between diets; the acetate:propionate ratio was greater (P < 0.05) for 50C versus 75C (4.12 versus 2.56). ADG in weeks 1–12 was greatest (P < 0.05) for Boer (59, 59, 90 and 49 g per day for Alpine, Angora, Boer and Spanish, respectively); in weeks 13–24 ADG was lowest (P < 0.05) for Spanish (25 g per day) and tended to be greater (P < 0.10) for Boer versus Alpine (82 versus 58 and 63 g per day). Gain efficiency (ADG:DM intake) was greater (P < 0.05) for Angora and Boer than for Alpine and Spanish in weeks 1–12 (132 and 127 versus 85 and 85 g/kg), and in weeks 13–24 was lower (P < 0.05) for Spanish than for Angora and Boer (80, 121, 104 and 51 g/kg for Alpine, Angora, Boer and Spanish, respectively). ADG and gain efficiency were greater (P < 0.05) for 75 versus 50% dietary concentrate in weeks 1–12 (ADG: 73 and 55 g per day; gain efficiency: 122 and 92 g/kg), and tended to be greater (P < 0.11) for 50C than for 75C in weeks 13–24 (ADG: 49 and 65 g per day; gain efficiency: 77 and 101 g/kg for 75C and 50C, respectively). In conclusion, differences in growth performance among Alpine, Angora, Boer and Spanish wether goats were similar with 50 and 75% concentrate diets, and the genotypes responded similarly to the change in dietary concentrate level from 50 to 75%. © 2004 Elsevier B.V. All rights reserved. Keywords: Goat; Growth performance; Dietary concentrate level
1. Introduction
∗ Corresponding author. Tel.: +1-405-466-3836; fax: +1-405-466-3138. E-mail address: [email protected] (A.L. Goetsch).
There are many different types of goats in the world used for a variety of purposes. In the US a logical and common categorization of goats is one bred for high milk production (e.g., Alpine), mohair fiber growth
0921-4488/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.smallrumres.2004.02.004
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(e.g., Angora) or meat production (e.g., Boer), as well as one that has not been intensively selected (e.g., Spanish) but that nonetheless serves useful purposes such as supplying meat and cashmere and vegetation management. How these different types of goats respond to various feeding management practices, such as dietary concentrate level, is not well understood. After a low or moderate plane of nutrition, when placed on a higher plane the level and/or efficiency of growth by cattle and sheep is often greater than expected based on nutrients consumed, which is known as compensatory growth. General factors responsible for compensatory growth are increased feed intake relative to BW and more efficient energy and/or protein metabolism (Drouillard et al., 1991). Compensatory growth does occur in goats (e.g., Havrevoll et al., 1995; Wuliji et al., 2003; Joemat et al., 2004), but potential differences in responses among genotypes have not been extensively studied. Knowledge of the capacity of goats for compensatory growth is necessary to achieve desired levels of performance while maximizing use of typically abundant and inexpensive forages. Therefore, objectives of this experiment were to determine effects of moderate and high dietary levels of concentrate (i.e., 50 and 75%, respectively) and a high level subsequent to a moderate one on growth performance by Alpine, Angora, Boer and Spanish wether goats. 2. Materials and methods 2.1. Experimental design and treatments The treatment arrangement was a 4 × 2 factorial, with four genotypes and two dietary treatments. Twelve Alpine, 12 Angora, 10 Boer (87.5% Boer and 12.5% Spanish) and 12 Spanish wether goats were used, with five (Boer) or six of each assigned to the two dietary treatments for similar mean BW and variation in BW within genotype. Wethers were approximately 4 months of age when the experiment began, having been weaned 1–2 months earlier. Housing was individually in 1.1 m × 1.2 m pens with plastic-coated expanded metal floors and free access to nipple waterers. Wethers were treated for internal parasites (Valbazen® ; SmithKline Beecham Animal Health, West Chester, PA) at the start of the experiment. The experiment was 24 weeks in length, divided into two
Table 1 Composition of diets for growing Alpine, Angora, Boer and Spanish wether goats Item
Ingredient composition (%DM) Coarsely ground prairie hay Ground corn Soybean meal Blood meal Fish meal Feather meal Dried molasses product Trace mineralized salta Vitamin premixb Deccoxc Limestone Dicalcium phosphate Chromic oxide Salt Chemical composition (%DM) Offered Ash CP NDF Consumed Phase 1 Ash CP NDF Phase 2 Ash CP NDF Calculatedd ME (Mcal/kg DM) TDN (%DM) CP (%DM)
Diet (%concentrate, DM basis) 75
50
25.00 55.98 6.06 2.07 2.56 2.07 3.00 0.75 0.50 0.05 1.06 0.10 0.30 0.50
50.00 29.40 6.82 2.50 3.20 2.50 3.00 0.75 0.50 0.05 0.63 0.10 0.30 0.25
6.1 18.6 25.6
7.1 17.5 38.8
4.6 15.9 25.1
6.0 15.6 37.8
4.0 13.4 25.6 2.70 71.0 17.0
2.37 62.4 17.0
a Contained 95–98% NaCl and at least 0.24% Mn, 0.24% Fe, 0.05% Mg, 0.032% Cu, 0.011% Co, 0.007% I and 0.005% Zn. b Contained 2200 IU/g vitamin A, 1200 IU/g vitamin D and 3 2.2 IU/g vitamin E. c Rhˆ one Poulenc, Atlanta, GA; 6% decoquinate. d Based on Preston (2000).
12-week phases. Dietary treatments consisted of offering 75 or 50% (DM basis) concentrate diets (75C and 50C, respectively; Table 1) in phase 1, followed by the 75% concentrate diet in phase 2. On the first day of the diet change, the amount of feed offered was decreased by approximately 10%, with gradual
M. Urge et al. / Small Ruminant Research 55 (2004) 149–158
increases in the first week. Concentrate and coarsely ground hay were weighed into feeding containers separately and then were hand-mixed. Feed was offered at approximately 110% of consumption on the preceding few days. There was one meal daily at 09:00 h, subsequent to removal and weighing of feed refusals. In a 2-week period before the experiment, the dietary concentrate level for all goats was gradually increased to 75%. No digestive upsets were noted during the experiment, and there were no observations of abnormal appearance of feces. 2.2. Measures and samples Wethers were weighed every 3 weeks. DM intake and ADG in the four 3-week periods of each phase were averaged to determine phase means. Phase means for DM intake and ADG were employed to estimate gain efficiency (ADG:DM intake (g/kg)). Diets and feed refusals were sampled daily and used to form composite samples for each phase. During week 8 of phase 1, wire screens were placed under pen floors to allow for once daily sampling of most feces excreted to form composite samples. Ruminal fluid was obtained via stomach tube on the last day of week 8 in both phases; 5 ml was placed into a tube containing 1 ml of 25% (w/v) metaphosphoric acid for later analysis of volatile fatty acids (Lu et al., 1990) and 3 ml was dispensed into another tube that had 2 ml of 3N HCl for determining ammonia N concentration (Broderick and Kang, 1980). Diet, feed refusal and fecal samples were first dried at 55 ◦ C for determination of partial DM concentration. Thereafter, samples of hay, feed refusals and feces were ground to pass a 1 mm screen, followed by analysis of these samples and concentrates for DM (100 ◦ C), ash, Kjeldahl N (AOAC, 1990) and NDF (filter bag technique; ANKOM Technology Corp., Fairport, NY). Chromium concentration was determined (Williams et al., 1962) in diet, refusal and fecal samples; chromium was used as an inert, external marker to determine digestibility (Cochran and Galyean, 1994). 2.3. Statistical analyses Data from one Spanish wether that experienced urinary calculi problems in the later part of the ex-
151
periment were omitted from statistical analyses. DM intake, ADG and ADG:DM intake were initially analyzed as a split-plot in time via mixed model analysis (Littell et al., 1996), with a repeated measure of phase and random effect of animal. Interactions involving phase were noted (P < 0.01) in DM intake as g per day (genotype × phase), ADG (dietary treatment × phase) and ADG:DM intake (dietary treatment × phase). Therefore, data were analyzed by phase with general linear models procedures of SAS (1990), with a model consisting of genotype, dietary treatment and the genotype × dietary treatment interaction. Main effect means were presented when the interaction was nonsignificant. Differences among means were determined by least significant difference with a protected F-test (P < 0.05). In order to facilitate possible use of these data by future researchers combining data from several experiments, dietary treatment × genotype interaction means were presented regardless of significance of the interaction (JAS, 2002).
3. Results 3.1. Diet composition Diets were formulated to be 17% CP (DM basis). Slightly greater concentrations of CP in DM offered may have been because of greater than expected CP levels in some ingredients or inconsistencies in diet mixing or sampling (Table 1). The concentration of CP in DM consumed was less than in DM offered, suggesting selection against high-CP feedstuffs perhaps of low palatability such as blood, feather and fish meals. Concentrations of NDF in DM consumed were similar to those in DM offered, reflecting little selection for or against prairie hay. 3.2. DM intake DM intake as g per day in phase 1 ranked (P < 0.05) Alpine and Boer > Spanish > Angora (Table 2). In phase 2, DM intake as g per day was significantly greater for Alpine and Boer versus Angora and Spanish. Dietary treatment did not affect DM intake in phase 1 or 2. DM intake as %BW in phase 1 was similar among genotypes. In phase 2, DM intake as %BW ranked (P < 0.05) Alpine and Angora > Boer >
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Table 2 Effects of dietary concentrate level (%) on DM intake, BW, ADG and ADG:DM intake by growing Alpine, Angora, Boer and Spanish wether goatsa Item
DM intake (g per day)
12-week phaseb
Diet (%)
1
BW (kg)
Angora
Boer
Spanish
75 50 Mean
659 746 703 c
474 398 436 a
656 721 689 c
585 550 567 b
45.0
75 50 Mean
688 736 712 b
494 636 515 a
643 761 702 b
447 466 456 a
42.7
1
75 50 Mean
2.87 3.33 3.10
3.00 2.92 2.96
2.56 3.01 2.79
2.61 2.73 2.67
0.165
2
75 50 Mean
2.44 2.80 2.62 c
2.36 2.88 2.62 c
2.00 2.43 2.22 b
1.72 2.07 1.90 a
0.123
75 50 Mean
20.0 20.3 20.2 b
12.6 11.8 12.2 a
21.2 20.2 20.7 b
19.8 18.7 19.2 b
1.03
75 50 Mean
25.7 24.5 25.1 b
18.6 15.7 17.2 a
28.8 27.7 28.3 c
24.9 21.7 23.3 b
1.16
2, end
75 50 Mean
30.7 29.4 30.0 b
22.8 22.0 22.4 a
34.2 36.1 35.2 c
26.8 24.0 25.4 a
1.53
1
75 50 Mean
68 50 59 a
72 46 59 a
91 90 90 b
62 36 49 a
10.9
75 50 Mean
59 57 58 b
50 75 63 b
64 100 82 b
22 28 25 a
13.9
1
75 50 Mean
103 67 85 a
148 115 132 b
133 121 127 b
105 64 85 a
14.3
2
75 50 Mean
82 78 80 ab
99 142 121 b
83 126 104 b
43 59 51 a
21.0
Initial
1, end
ADG (g)
2
ADG:DM intake (g/kg)
S.E.
Alpine
2
DM intake (%BW)
Genotype
31.9
30.2
0.117
0.087
0.73
0.82
1.08
7.7
9.6
10.1
14.8
Dietc
S.E.
75
50
593
604
22.6
568
625
21.4
2.76 a
3.00 b
0.083
2.13 a
2.54 b
0.062
18.4
17.8
0.52
24.5 b
22.4 a
0.58
28.6
27.9
0.77
73 b
55 a
5.5
49
65
6.8
122 b
92 a
7.2
77
101
10.5
Means within a mean row without a common letter differ (P < 0.05). a n = 6, 6, 5 and 5 or 6 (per dietary treatment) for Alpine, Angora, Boer and Spanish, respectively. b Wether goats on both diets received the 75% concentrate diet in phase 2. c 75 = 75% concentrate; 50 = 50% concentrate.
Spanish, and in phases 1–2 was significantly greatest among treatments for Alpine and Angora and tended to be greater (P < 0.07) for Boer versus Spanish. In both phases and the entire experiment, DM intake as %BW was significantly greater for 50C than for 75C.
3.3. BW, ADG and ADG: DM intake Initial BW was significantly lowest among treatments for Angora (Table 2). BW at the end of phase 1 ranked Boer > Spanish and Alpine > Angora. The
M. Urge et al. / Small Ruminant Research 55 (2004) 149–158
genotype ranking at the end of phase 2 was similar, Boer > Alpine > Angora and Spanish (P < 0.05), although BW tended (P < 0.10) to be greater for Spanish versus Angora. BW was significantly greater for 75 versus 50% concentrate after phase 1 but was similar between dietary treatments at the beginning and end of the experiment. In phase 1, Boer wethers gained significantly faster than other genotypes, which were similar (Table 2). In phase 2, ADG of Spanish goats was significantly
153
lowest, and Boer wethers tended (P < 0.07) to gain BW more rapidly than Alpines. ADG in phase 1 was significantly greater for the 75 versus 50% concentrate diet, although there was a tendency (P < 0.10) for greater ADG in phase 2 for 50C than for 75C. Gain efficiency (ADG:DM intake) was significantly greater for Angora and Boer than for Alpine and Spanish in phase 1 (Table 2). In phase 2, gain efficiency was significantly lower for Spanish than for Angora and Boer, with that for Alpine being intermediate (P >
Table 3 Effects of dietary concentrate level on intake and digestion by growing Alpine, Angora, Boer and Spanish wether goatsa Item
Diet (%)
Genotype
S.E.
Alpine
Angora
Boer
Spanish
75 50
637 bc 769 c
558 b 422 a
697 bc 769 c
573 b 557 ab
50.0
75 50
608 bcd 728 d
534 b 397 a
667 cd 726 d
552 bc 526 b
46.5
75 50 Mean
75.1 69.7 72.4
79.4 69.3 74.3
79.2 72.7 76.0
83.6 73.6 78.6
75 50 Mean
468 502 485 bc
425 272 349 a
525 524 524 c
459 388 423 b
37.3
75 50
169 abc 307 d
127 a 141 ab
179 bc 299 d
147 ab 222 c
16.2
Digestibility (%)
75 50 Mean
48.6 52.5 50.6
50.3 42.7 46.5
55.0 55.7 55.4
62.7 57.3 60.0
Digested (g per day)
75 50 Mean
87 159 123 b
67 59 63 a
98 166 132 b
91 128 110 b
Intake (g per day)
75 50 Mean
15.9 17.1 16.5 b
14.3 11.1 12.7 a
17.0 17.8 17.4 b
12.9 12.3 12.6 a
1.93
Digestibility (%)
75 50 Mean
57.5 60.5 59.0
70.0 60.7 65.4
68.2 65.0 66.6
73.5 61.0 67.3
4.41
75 50 Mean
10.0 10.1 10.1
10.0 6.8 8.4
11.4 11.4 11.4
9.4 7.6 8.5
1.43
DM intake (g per day) OM Intake (g per day) Digestibility (%)
Digested (g per day)
NDF Intake (g per day)
Dietb
S.E.
75
50
79.3 b
71.3 a
469
421
54.2
52.1
3.46
86 a
128 b
8.1
15.0
14.6
0.97
67.3
61.8
2.21
10.2
9.0
0.72
3.14 2.22
26.6
1.57
18.7
6.92 4.90 16.3 11.5
N
Digested (g per day)
Means for 75 and 50% diets or within a mean row without a common letter differ (P < 0.05). a Determined in week 8 of the 12-week phase 1. b 75 = 75% concentrate; 50 = 50% concentrate.
1.37
3.12
1.00
154
M. Urge et al. / Small Ruminant Research 55 (2004) 149–158
Table 4 Effects of dietary concentrate level on ruminal VFA and ammonia N concentrations in growing Alpine, Angora, Boer and Spanish wether goats Weeka
Item
Diet (%)
Genotype Alpine
Angora
Boer
Spanish
8
Total VFA (mM/l)
75 50 Mean
64.7 71.1 67.9
63.6 68.8 66.2
60.4 67.8 64.1
59.6 71.6 65.6
5.61
75 50 Mean
63.7 72.1 67.9 c
53.3 64.1 58.7 a
60.0 66.9 63.5 b
57.7 70.2 64.0 b
1.88
Propionate (mol%)
75 50
20.5 a 17.1 a
32.0 b 20.6 a
20.9 a 18.3 a
27.8 b 16.1 a
1.82
Isobutyrate (mol%)
75 50 Mean
0.51 0.17 0.34
0.24 0.22 0.23
0.49 0.34 0.42
0.49 0.21 0.35
0.086
Butyrate (mol%)
75 50 Mean
12.4 9.6 11.0 a
11.9 13.6 12.8 ab
16.2 13.1 14.7 b
11.9 12.5 12.2 ab
1.26
Isovalerate (mol%)
75 50 Mean
1.69 0.43 1.06
1.42 0.92 1.17
1.22 0.51 0.86
1.01 0.39 0.70
0.315
75 50 Mean
1.23 0.63 0.93
1.16 0.62 0.89
1.22 0.77 0.99
1.06 0.58 0.82
0.151
75 50 Mean
3.42 4.24 3.83
1.71 3.31 2.51
3.00 3.79 3.40
2.12 5.16 3.64
0.579
Ammonia (mg/dl)
75 50 Mean
12.1 12.2 12.2 c
10.5 11.1 10.8 bc
6.2 6.3 6.3 a
7.7 6.4 7.0 ab
2.04
Total VFA (mM/l)
75 50 Mean
40.5 42.3 41.3
38.3 42.5 40.4
37.9 44.4 41.1
39.2 43.4 41.3
3.93
75 50 Mean
57.7 54.2 56.0
51.6 59.4 55.5
55.7 57.3 56.5
47.1 56.5 51.8
4.25
Propionate (mol%)
75 50 Mean
23.6 28.3 26.0
25.8 24.0 24.9
22.5 26.9 24.7
31.6 24.7 28.1
3.91
Isobutyrate (mol%)
75 50 Mean
0.55 0.83 0.68
0.54 0.61 0.58
0.60 0.61 0.60
0.73 0.64 0.68
0.126
75 50 Mean
12.2 13.2 12.7
18.4 12.8 15.6
15.6 11.2 13.4
15.0 12.6 13.8
3.38
75 50 Mean
4.17 2.01 3.09
2.15 1.82 1.98
3.33 2.49 2.91
3.37 3.31 3.34
1.051
Acetate (mol%)
Valerate (mol%)
Acetate:propionate
20
Acetate (mol%)
Butyrate (mol%)
Isovalerate (mol%)
S.E.
3.97
1.33
0.061
0.89
0.223
0.107
0.410
1.45
2.78
3.01
2.77
0.089
2.392
0.740
Dietb
S.E.
75
50
62.1
69.8
2.81
58.7 a
68.3 b
0.94
0.43 b
0.24 a
0.043
13.1
12.2
0.63
1.33 b
0.56 a
0.158
1.17 b
0.65 a
0.076
2.56 a
4.12 b
0.290
9.2
9.0
1.02
38.9
43.2
1.97
53.0
56.8
2.13
25.9
26.0
1.96
0.60
0.67
0.063
15.3
12.4
1.69
3.26
2.41
0.526
M. Urge et al. / Small Ruminant Research 55 (2004) 149–158
155
Table 4 (Continued ). Weeka
Item
Diet (%)
Genotype
S.E.
Alpine
Angora
Boer
Spanish
75 50 Mean
1.76 1.42 1.59
1.50 1.41 1.46
2.31 1.57 1.94
2.13 2.27 2.20
0.481
Acetate:propionate
75 50 Mean
2.76 2.36 2.56
2.17 2.68 2.43
2.72 2.58 2.65
1.75 2.40 2.08
0.450
Ammonia (mg/dl)
75 50
10.6 abc 6.1 a
9.8 abc 9.9 abc
7.1 ab 14.2 c
5.8 a 11.5 bc
1.94
Valerate (mol%)
0.340
0.319
Dietb
S.E.
75
50
1.93
1.67
0.241
2.35
2.51
0.225
Means within a row without a common letter differ (P < 0.05). a The two phases were 12 weeks in length. 50 and 75% diets were fed in phase 1 and all wether goats received the 75% diet in phase 2. b 75 = 75% concentrate; 50 = 50% concentrate.
0.10). Gain efficiency was significantly greater for 75C than for 50C in phase 1, with an opposite numerical difference in phase 2. 3.4. Digestibility There were significant interactions between genotype and dietary treatment in intake of DM, OM and NDF during week 8 of phase 1 when digestibilities were determined (Table 3). Although a comparable interaction in DM intake during all of phase 1 was not significant, numerically interaction means were similar. DM intake in week 8 of phase 1 was similar among genotypes with 75% concentrate, but with 50% concentrate DM intake was significantly greatest among genotypes for Alpine and Boer. Within genotypes, DM intake was similar between diets for Alpine, Boer and Spanish but was significantly lower for 50 versus 75% concentrate for Angora. Similar differences existed in OM intake. NDF intake was significantly greater for 50% concentrate than for 75% for Alpine, Boer and Spanish but for Angora was similar between diets. Apparent total tract OM digestibility was similar among genotypes and significantly greater for 75 versus 50% concentrate (Table 3). OM digestibilities were slightly greater than expected based on calculated TDN concentration, suggesting greater digestibility of prairie hay than the assumed literature value. Digestible OM intake was lowest among genotypes (P < 0.05) for Angora and significantly greater for Boer versus Spanish, with that for Alpine intermediate (P > 0.10) to values for Boer and Spanish.
Total tract NDF digestibility was similar among genotypes and between diets (Table 3). Among genotypes, digestible NDF intake was significantly lowest among genotypes for Angora and was significantly greater for 50 versus 75% concentrate. Apparent total tract N digestibility and digestible N intake were similar among genotypes and between dietary concentrate levels. 3.5. Ruminal fluid VFA and ammonia N The concentration of total VFA in ruminal fluid in phase 1 was similar among genotypes and between diets (Table 4). The molar percentage of acetate ranked (P < 0.05) Alpine > Boer and Spanish > Angora and was significantly greater for 50 versus 75% concentrate. There was a significant interaction between genotype and dietary concentrate level in molar percentage of propionate, which was significantly greater for Angora and Spanish than for Alpine and Boer with 75% dietary concentrate but similar among genotypes with 50%. The acetate:propionate ratio was similar among genotypes and significantly greater for 50% dietary concentrate than for 75%. The molar percentage of butyrate was significantly greater for Boer than for Alpine. Genotype did not affect molar percentages of isobutyrate, isovalerate or valerate, which were significantly greater for 75 versus 50% concentrate. Ammonia N concentration in phase 1 was significantly greater for Alpine than for Boer and Spanish and significantly greater for Angora versus Boer.
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In phase 2, there were no differences among genotypes or between dietary treatments in ruminal VFA measures (Table 4). However, a significant interaction between genotype and dietary treatment occurred in ammonia N concentration. Ammonia N concentration was significantly greater with the 50 versus 75% dietary concentrate treatment for Boer and Spanish but was similar between dietary treatments for Alpine and Angora. 4. Discussion 4.1. Genotype Greater ADG by growing Boer than Spanish and Angora goats agrees with results of other studies involving full-blood or crossbred Boer goats (Casey and Van Niekirk, 1988; Van Niekirk and Casey, 1988; Waldron et al., 1995, 1996; Lewis et al., 1997; Luo et al., 2000; Prieto et al., 2000; Cameron et al., 2001; Joemat et al., 2004), although similar comparisons of Boer goats and dairy goat breeds such as Alpine and of full-blood Angora versus Spanish are not available. Greater overall ADG by Angora than Spanish wethers in the present experiment may reflect little genetic selection of Spanish goats for growth performance and breeding of Angoras for high mohair fiber growth. However, a similar difference in ADG between Angora and Spanish goats does not seem likely with a limited nutritional plane that would restrict fiber growth and/or result in appreciable partitioning of nutrients by Angora goats for fiber growth at the expense of other peripheral tissues (Cronjé, 2000; Joemat et al., 2003). The lack of interaction in ADG between genotype and dietary treatment in phase 1 implies that level of concentrate in moderate- to high-quality diets impacts early postweaning growth similarly regardless of genotype. Conversely, in some cases greater growth potential of crossbred Boer goats compared with indigenous or local genotypes has only been realized with high-quality diets or has been expressed to a greater extent with high-quality versus low- or moderate-quality diets (Huston and Waldron, 1996; Roeder et al., 1997; Negesse et al., 2001; Joemat et al., 2004). This was not observed in the present experiment perhaps because the 50% concentrate level was above a diet quality threshold.
Angora wethers were as efficient in converting dietary energy into mass of tissue plus mohair fiber as Boer goats were into tissue mass, although rate of gain by Angoras was relatively low. The lower gain efficiency for Alpine compared with Angora and Boer, and greatest DM intake as g/kg BW0.75 in the 24-week experiment for Alpine suggest a higher MEm (i.e., 19%) of growing dairy goats than of other breeds (Luo et al., 2004). However, Luo et al. (2004) also estimated an MEg requirement of growing indigenous goats 14% lower than for dairy goats or ones with 50% or more Boer breeding. This disparity may be partially reconciled by lowest DM intake as g/kg BW0.75 for Spanish, which would have resulted in a large proportion of energy consumed being used for maintenance and little for growth. 4.2. Dietary treatment The difference between dietary concentrate levels in total tract OM digestibility was expected because of greater digestibility of concentrate than forage. Also, greater DM intake as %BW for 50 than 75% concentrate suggests shorter digest retention in the rumen for 50% concentrate, which may have lessened the difference in digestion relative to a set level of intake. Greater ADG for 75% dietary concentrate than for 50% in phase 1 was anticipated based on findings with other ruminant species as well as with young Alpine doelings (Goetsch et al., 2003). Although, ADG for both dietary treatments was slightly less than expected based on forage composition and levels of dietary concentrate. The feeding protocol employed, to minimize feed refusals, may have resulted in DM intake and ADG less than with a greater feeding rate. Nonetheless, these results differ somewhat from findings of Morand-Fehr and Sauvant (1978) that with lactating dairy goats there is little or no production advantage in use of dietary concentrate levels above 50%, as generally occurs with dairy and beef cattle. Overall, results of the present experiment indicate that growth of young goats consuming offered diets for minimal feed refusals can be enhanced by increases in dietary concentrate level up to at least 75%, not because of increased feed intake but rather via greater efficiency of use of ME from concentrate versus forage. Compensatory growth in phase 2 was partially a function of greater DM intake relative to BW and
M. Urge et al. / Small Ruminant Research 55 (2004) 149–158
BW0.75 . However, the tendency for greater gain efficiency in phase 2 with 50C versus 75C, resulting in similar overall gain efficiency in the 24-week experiment, also indicates more efficient energy metabolism such as via decreased MEm in the early weeks of compensation (Silanikove, 2000). The lack of interaction between genotype and dietary treatment in phase 2 DM intake, ADG and gain efficiency do not suggest appreciable differences among genotypes in compensatory growth potential. These results are in slight contrast to those of Joemat et al. (2004). In that study a low nutritional plane (prairie hay without supplemental concentrate) for 56 days restricted ADG by yearling Boer × Spanish doelings but not by Spanish, resulting in compensation only by Boer × Spanish. Thus, conditions such as animal age, as affecting nutrient needs, and degree and length of nutrient restriction will influence the existence and magnitude of compensatory growth by goats. It is common in beef cattle production systems to take advantage of compensatory growth, such as with wintering on low-quality forage preceding consumption of high-quality spring forage or placement in feedlots with high-concentrate diets after backgrounding on forage-based diets. Such strategies are designed in part to maximize reliance on typically abundant and relatively inexpensive forages and minimize use of more costly concentrate feedstuffs. In this regard, during the entire experiment total concentrate and forage DM intake was 73.2 and 24.4 kg for 75C and 64.8 and 38.5 kg for 50C, respectively. Hence, 8.4 kg less concentrate and 14.1 kg more forage per animal were consumed by 50C versus 75C wethers, with the end result of similar final BW. In terms of feed costs, for the 50C treatment to be economically advantageous, the expense of forage would need to be less than 60% (i.e., 8.4 kg concentrate/14.1 kg forage) of that of concentrate.
5. Summary and conclusions These results indicate that differences in growth performance among Alpine, Angora, Boer and Spanish wether goats are not influenced by dietary concentrate level in the range 50–75%. With growth limited by use of a 50% dietary level of concentrate, capacity for compensatory growth by growing Alpine, Angora,
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Boer and Spanish wether goats appears similar when shifted to a 75% concentrate diet.
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