Growth and cashmere production by Spanish goats consuming ad
libitum diets differing in protein and energy levels
D.S. Ivey
a, F.N. Owens
b, T. Sahlu
a,*, T.H. Teh
a, P.L. Claypool
c, A.L. Goetsch
a aE (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK 73050, USAbAnimal Science Department, Oklahoma State University, Stillwater, OK 74078, USA cDepartment of Statistics, Oklahoma State University, Stillwater, OK 74078, USA
Accepted 11 June 1999
Abstract
Thirty-six Spanish goat wethers (19612.9 days of age and 17.54.60 kg BW at experiment initiation) from a herd previously selected for cashmere growth were used to determine effects and interactions of ad libitum consumption of diets differing in concentrations of CP (10% and 15%) and ME (2.00, 2.35 and 2.70 Mcal/kg; DM basis) on growth and cashmere ®ber production in an 84-day, fall-season experiment. DM intake was greater (P< 0.05) for diets with 15% vs. 10% CP (736 vs. 655 g/day) but similar among ME concentrations (P> 0.10). ADG was greater (P< 0.02) for 15% vs. 10% CP (79 vs. 53 g/ day) and increased linearly (P< 0.10) as dietary ME level increased (58, 62 and 78 g/day for 2.00, 2.35 and 2.70 Mcal/kg ME, respectively). Total ¯eece weight at the end of the experiment was similar (P> 0.10) between CP levels but increased linearly (P< 0.03) as ME concentration in the diet increased (197, 239 and 227 g/day). Guard hair weight was not affected by dietary treatments (P> 0.10); cashmere length was similar among treatments (P> 0.10); and cashmere ®ber diameter was not altered by dietary ME level (P> 0.10) but was greater (P< 0.05) for 15% vs. 10% CP (16.92 vs. 16.06mm). Cashmere weight was
in¯uenced by an interaction between CP and ME levels (P< 0.05); cashmere ®ber weight with 10% CP was 92, 82 and 95 g, and with 15% CP was 63, 115 and 99 g for 2.00, 2.35 and 2.70 Mcal ME/kg diets, respectively (SE10.2). However, the ranking of treatment means for initial cashmere ®ber weight was similar to that at the end of the experiment, although differences at the beginning were non-signi®cant and of lesser magnitude than at the end. In conclusion, further research with in¯uences of concentrations of CP and ME in diets consumed ad libitum on cashmere ®ber growth of growing US Spanish wether goats is required, and animal numbers and allocation to treatments deserve careful consideration in studies of cashmere ®ber production.#2000 Elsevier Science B.V. All rights reserved.
Keywords:Cashmere; Goat; Energy; Protein
1. Introduction
Research with Australian feral goats, of unknown breed origin and unselected for cashmere ®ber growth, has shown little or no effects of plane of nutrition on cashmere ®ber production with basal nutritional *Corresponding author. Tel.: 466-3836; fax:
+1-405-466-3138.
E-mail address:sahlu@mail.luresext.edu (T. Sahlu).
planes adequate for BW maintenance (Ash and Norton, 1984, 1987a,b; KloÈren et al., 1993). Responses in total ¯eece production, when noted, have been attributable to hair growth by primary follicles. How-ever, it is unclear if such ®ndings are of similar applicability to other breeds or types of goats that grow cashmere ®ber or with other production condi-tions.
Most non-Angora breeds or types of goats in the USA grow cashmere ®ber (Litherland and Sahlu, 1997). The type of goat used for cashmere ®ber production most frequently in the USA is the Spanish. The Spanish goat herd of Langston University was selected for cashmere growth for several years pre-ceding this experiment and, therefore, might differ from Australian feral goats in responses to dietary variations. In addition, interactions between dietary protein and energy levels with ad libitum feed intake in effects on cashmere ®ber growth have not been extensively investigated. Ash and Norton (1984) stu-died interactions between protein and energy intakes in cashmere ®ber growth in young Australian feral goats; however, energy intake was varied through ad libitum vs. restricted consumption of a pelleted diet. Moreover, the proportion of ingested ME available to non-visceral tissues may differ between restricted intake of a particular diet and ad libitum consumption of diets varying in ingredient composition and between pelleted and other diet physical forms (Goetsch, 1998). Thus, the objective of the present experiment was to evaluate the effects and interactions of ad libitum consumption of diets differing in CP and ME concentrations on growth and cashmere ®ber production by young/growing US Spanish wether goats.
2. Materials and methods
2.1. Animals and treatments
Thirty-six cashmere-producing Spanish wether goats were housed individually in 1.2 m1.2 m pens during an 84-day experiment following a 3-wk pre-liminary period (September±January). Wethers were from the Spanish goat herd of Langston University, which had been selected for cashmere ®ber production for the preceding several years. Room temperature
was held constant at 218C with 9 h of light and 15 h of dark, with light beginning at 0800 h. BW was mea-sured on two consecutive days and goats were sheared at the beginning and end of the experiment. Initial age and BW were 19612.9 days and 17.54.60 kg, respectively. During the preliminary period, goats consumed ad libitum a diet with 10% CP and 2.35 Mcal/kg ME (DM basis). Thereafter, animals were blocked into six initial BW groups and assigned randomly within group to the six treatments.
The treatment arrangement was a 23 factorial. Diets were formulated to be 10% or 15% CP and 2.00, 2.35 or 2.70 Mcal/kg ME (DM basis; Table 1). Soy-bean meal replaced rolled oats and a small amount of ground corn to vary the CP concentration, and ground corn substituted for cottonseed hulls to derive different ME concentrations. Diets were completely mixed (Weigh-Tronix, Fairmont, MN) and offered once daily (0900 h) at approximately 110% of consumption on the preceding few days. Feeders were emptied and orts weighed twice weekly; feed and ort samples were collected once weekly and composited by 28-day period.
2.2. Samples and analyses
Feed and ort samples were dried for 48 h at 658C, allowed to air equilibrate and ground in a Wiley mill to pass a 1 mm screen. Samples were analyzed for DM (AOAC, 1990), N (Technicon, Tarrytown, NY), GE (adiabatic bomb calorimeter; Parr Instrument, Moline, IL), ADF and NDF (Goering and Van Soest, 1970). Ort composition (data not shown) was similar to that of diets offered and, therefore, not used for correction.
2.3. Statistical analyses
Data were analyzed with the GLM procedure of SAS (1985) as a randomized complete block design (Cochran and Cox, 1957). The model included CP level, ME level, CPME level interaction, BW block
and residual error, with effects tested by residual error. When the CPME level interaction was non-signif-icant (P> 0.10), orthogonal contrasts were conducted for linear and quadratic effects of level of ME. Initial variable means were similar (P> 0.10) among treat-ments (Table 2) and initial values included as covari-Table 1
Composition of diets consumed by growing Spanish wethers
Item Diet (%DM)
Ground corn 6.21 30.11 61.22 5.13 15.49 47.09
Cottonseed hulls 55.35 39.75 18.19 57.13 38.86 18.65
Rolled oats 24.31 17.68 9.99 5.02 18.19 7.37
Soybean meal 7.55 8.13 6.20 24.67 23.00 20.98
Alfalfa meal 3.64 1.96 2.00 5.02 2.02 3.68
Limestone 0.58 0.47 0.47 0.60 0.48 0.44
Dicalcium phosphate 1.16 0.93 0.95 1.19 0.96 0.88
Trace mineral salta 0.58 0.47 0.47 0.60 0.48 0.44
Vitamin premixb 0.62 0.50 0.51 0.64 0.52 0.47
Nutrient composition
DM (% as-fed) 91.0 90.0 90.3 91.2 90.5 90.8
CP (% DM) 9.71 9.57 9.99 14.83 14.87 15.19
ADF (% DM) 39.8 31.1 16.4 38.6 25.8 17.9
Ash (% DM) 4.64 3.72 3.80 5.25 4.50 4.18
ME (Mcal/kg)c 2.01 2.34 2.71 2.04 2.34 2.70
S(% DM)c 0.15 0.15 0.14 0.17 0.18 0.18
N:Sratioc 19.5 17.0 15.3 25.0 20.2 18.2
a95±98.5% NaCl and >0.24% Mn, 0.24% Fe, 0.05% Mg, 0.032% Cu, 0.011% Co, 0.007% I and 0.005% Zn. b2200 IU vitamin A, 1200 IU vitamin D
3and 2.2 IU vitamin E/g. cME andSwere calculated from NRC (1981).
Table 2
Initial measures for growing Spanish wethers consuming ad libitum diets differing in concentrations of CP and ME
Item Diet SE
Age (days) 213 210 204 211 210 211 2.0
BW (kg) 17.5 19.6 21.1 20.5 18.0 17.5 1.37
Fleece weight (g) 168 166 158 166 171 163 11.5
Guard hair (g) 119 126 116 127 117 118 10.5
Cashmere (g) 48.9 39.8 42.6 39.5 54.6 45.7 8.35
% of total fleece
Guard hair 71.0 75.7 73.3 76.4 67.4 73.9 6.48
Cashmere 29.0 24.3 26.7 23.6 32.6 26.1 4.58
ates did not have signi®cant effects (P> 0.10), sug-gesting acceptable allocation to treatments.
3. Results
The CPME level interaction was non-signi®cant (P> 0.10) for DM intake, ADG and ADG : DM intake (feed conversion ratio). DM intake was similar (P> 0.10) among ME levels but greater (P< 0.05) for 15% vs. 10% dietary CP (Table 3). Calculated ME intake was greater (P< 0.01) for 15% CP than for 10% and increased linearly (P< 0.01) with increasing diet-ary ME level, although numerically ME intake was similar between 2.00 and 2.35 Mcal/kg ME diets. ADG was greater (P< 0.02) for 15% vs. 10% dietary CP and linearly increased (P< 0.10) as ME concen-tration in the diet increased, although numerically the difference between the 2.35 and 2.70 Mcal/kg ME diets was much greater than that between diets with 2.00 and 2.35 Mcal/kg ME. Feed conversion ratio was greater (P< 0.04) for 15% CP than for 10% and increased linearly (P< 0.02) as the concentration of ME in the diet increased.
Total ¯eece weight was not in¯uenced (P> 0.10) by dietary CP concentration; ¯eece weight increased linearly (P< 0.03) as level of ME in the diet increased, although numerically ¯eece weight was similar for diets with 2.35 and 2.70 Mcal/kg ME (Table 3). Guard hair weight was not affected (P> 0.10) by dietary concentration of CP or ME. However, levels of CP and ME in the diet interacted (P< 0.05) in the percentage of cashmere in the total ¯eece and cashmere weight (Figs. 1 and 2, respectively). These interactions
appeared primarily due to change in cashmere weight as ME concentration increased with 15% CP diets, since ME level had little effect with 10% dietary CP. With 15% CP, cashmere weight increased markedly then decreased slightly as ME level increased from 2.00 to 2.35 Mcal/kg and then to 2.70 Mcal/kg ME. Cashmere weight was not affected by CP level with the 2.70 Mcal/kg ME diet, but was lower for 15% vs. 10% CP with 2.00 Mcal/kg ME diets and greater with diets containing 2.35 Mcal/kg ME. Cashmere dia-meter was greater (P< 0.05) for diets 15% in CP than Table 3
Feed intake, ADG, feed conversion ratio and fleece characteristics for growing Spanish wethers consuming ad libitum diets differing in concentrations of CP and ME for 84-days in the fall season
Item % dietary CP SE Pvalue Dietary ME (Mcal/kg) SE Pvalue
10 15 2.00 2.35 2.79 Linear Quadratic
DM intake (g/day) 655 736 27.7 0.05 746 664 676 34.0 0.49 0.29 ME intake (Mcal/day) 1.54 1.74 0.06 0.05 1.51 1.55 1.83 0.08 0.05 0.49 ADG (g/day) 53.4 78.8 7.09 0.02 58.3 61.7 78.4 8.69 0.10 0.51
ADG:DM intake (g/kg) 81 103 7.3 0.04 77 91 109 8.9 0.02 0.23
Fleece weight (g) 215 227 7.3 0.27 197 239 227 8.9 0.03 0.68
Guard hair weight (g) 125 134 7.3 0.39 119 140 130 9.0 0.46 0.15 Cashmere fiber diameter (mm) 16.06 16.92 0.29 0.05 16.05 16.86 16.56 0.36 0.56 0.71 Cashmere fiber length (mm) 32.8 31.5 1.65 0.56 30.8 33.9 31.8 2.02 0.81 0.56
for diets with 10% CP and was not in¯uenced by ME concentration (P> 0.10). Cashmere length was not affected (P> 0.10) by dietary treatments.
4. Discussion
Russel (1992) summarized that the plane of nutri-tion does not in¯uence cashmere ®ber growth when nutrients provided exceed the requirement for BW maintenance, with effects of nutrition on cashmere ®ber growth occurring only with severe nutrient restriction. Differing intakes of protein or amino acids (Johnson and Rowe, 1984; Ash and Norton, 1987a, b; McGregor, 1988 or ME (McGregor, 1988; Norton et al., 1990; KloÈren et al., 1993) above those required for BW maintenance have not signi®cantly in-creased cashmere ®ber growth. However, as noted earlier potential interactions between dietary protein and ME levels have not been extensively studied with ad libitum intake of diets differing in in-gredient composition, as was tested in the present experiment.
As noted previously, measures at trial initiation were similar among treatments and not signi®cant
as covariates, which may be partially attributable to the relatively low number of observations per treat-ment and high variability in some measures such as cashmere ®ber weight. However, numerical differ-ences among treatments in initial cashmere ®ber weight resembled those at the end of the experiment. Thus, it is possible that with a greater number of animals, initial cashmere weight would have signi®-cantly in¯uenced cashmere ®ber weight at the end of the experiment and, thus, use as a covariate would have lessened or eliminated observed treatment dif-ferences in ®nal weight. Relatedly, it was not possible to obtain initial measure information soon enough for use to allot animals to treatments, as conducted by Restall et al. (1994). This alternate method of alloca-tion also may have in¯uenced treatment effects. Hence, future experimentation concerning nutritional plane effects on cashmere ®ber growth should entail usage of a greater number of animals per treatment and (or) treatment allotment based on inherent differ-ences among animals in cashmere ®ber growth. Although, it should be noted that such procedures will not eliminate such problems. For example, varia-tion among animals in seasonal changes in follicle activity might not be re¯ected by earlier cashmere ®ber growth.
Nutritional planes in the present experiment were greater than required for BW maintenance, as evi-denced by observed ADG. Hence, treatment differ-ences in cashmere ®ber weight are not clearly in agreement or disagreement with the summarization of Russel (1992), regarding no effects of nutritional planes above maintenance, although the effect of dietary CP level on cashmere ®ber diameter is notable. However, results of the present experiment do suggest the need for further study of such effects with US Spanish goats selected for cashmere ®ber growth, particularly as relating to potential for interactions between dietary energy and protein levels. For example, a plausible framework of logic for the observed interaction in cashmere ®ber production relating to use of nutrients by different tissues can be put forward.
With the 2.00 Mcal/kg ME diet, 15% CP may have increased amino acid catabolism for energy compared with 10% CP, thereby minimizing amino acids avail-able for peripheral muscle protein accretion. Simi-larly, greater DM intake and ADG for 15% vs. 10% CP Fig. 2. Cashmere weight for Spanish wethers after consuming diets
diets indicates greater nutrient absorption and hor-monally controlled nutrient partitioning for nutrient use by peripheral muscle. Amino acid catabolism for energy with 15% dietary CP should have been less with the 2.35 vs. 2.00 Mcal/kg ME diet due to greater microbial protein synthesis from increased ruminal OM fermentation. This would have increased the proportion of the added supply of absorbed amino acids available for use in protein synthesis from 15% dietary CP relative to that for 10% with 2.35 Mcal/ kg ME. These factors imply a greater quantity of amino acids available for support of ®ber growth with 2.35 Mcal/kg ME and 15% vs. 10% dietary CP, depending on use in peripheral muscle accretion. In this regard, although ADG linearly increased with increasing dietary ME concentration, numerically ADG was similar for 2.00 and 2.35 Mcal/kg ME diets. An explanation for numerically similar ADG for 2.00 and 2.35 Mcal/kg ME diets is not readily apparent. However, nutrient partitioning among various tissues does not necessarily change linearly as diet composition is varied. Relatedly, the proportion of energy used by visceral tissues in¯uences the quantity of energy available for use by non-visceral tissues. Visceral tissue energy use relative to absorbed energy is greater for forage- than for concentrate-based diets, but the pattern of change as dietary concentrate level increases has not been explored (Goetsch, 1998). Much greater ADG for diets with 2.70 Mcal/kg ME compared with diets lower in ME could re¯ect a relatively high proportion of absorbed amino acids added by use of 15% vs. 10% CP being accreted in peripheral muscle, thereby preventing effect of dietary CP concentration on cashmere pro-duction.
5. Conclusions
With growing Spanish wethers in the fall season and ad libitum consumption of diets approximately 40%, 60% and 80% concentrate, corresponding to 2.00, 2.35 and 2.70 Mcal/kg ME, respectively, cashmere ®ber diameter was greater for 15% vs. 10% dietary CP regardless of ME level. Diet composition did not impact cashmere ®ber length. Dietary concentrations of CP and ME did not alter guard hair weight but interacted in weight of cashmere ®ber. However,
similar numerical differences, although of lesser mag-nitude, among treatments in pre-experiment cashmere ®ber weight existed, suggesting need for further experimentation with greater animal numbers and (or) treatment allotment based on animal differences in most important variables.
Acknowledgements
This research was partially supported by USDA Grant No. 91-38814-6241.
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