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Effects of dietary protein sources on mohair growth and body weight of yearling Angora doelings
Small Ruminant Research 38 (2000) 29±35
Effects of dietary protein sources on mohair growth and body weight of yearling Angora doelings A.J. Litherland, T. Sahlu*, C.A. Toerien, R. Puchala, K. Tesfai, A.L. Goetsch E (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK 73050, USA Received 25 April 1999; accepted 1 February 2000
Abstract Fifty-one yearling Angora doelings (200.6 kg initial body weight (BW)) were used to determine effects of different dietary protein sources on BW change and mohair growth. Diets consisted of approximately 40% roughage and 18±19% CP (DM basis), of which two-thirds was supplied by corn gluten meal (CG), cottonseed meal (CT), hydrolyzed feather meal (FT) or menhaden ®sh meal (FI); DM intake was restricted at approximately 0.7 kg/day. During the 94-day experiment, ¯eece-free ADG was greatest (P<0.05) for FI (35, 33, 35 and 50 g), whereas greasy ¯eece weight was greatest (P<0.05) for CG (4.4, 3.6, 3.4 and 3.4 kg for CG, CT, FT and FI, respectively). Likewise, mohair growth rate was greatest among treatments (P<0.05) for CG in each of the three 31- or 32-day periods. Ruminal ¯uid ammonia N concentration was 8, 11, 6 and 13 mg/dl (S.E. 1) immediately before feeding; 10, 18, 11 and 23 mg/dl (S.E. 2) at 2 h after feeding; 8, 15, 10 and 18 mg/dl (S.E. 2) at 4 h after feeding; and 4, 6, 5 and 8 mg/dl (S.E. 1) at 6 h after feeding for CG, CT, FT and FI, respectively. Total VFA concentration in ruminal ¯uid was similar among treatments (P>0.05) at 4 and 6 h, but was generally lower for CG and FT than for CT and FI immediately before feeding (29, 33, 26 and 37 mM; S.E. 2) and at 2 h after feeding (44, 57, 45 and 51 mM for CG, CT, FT and FI, respectively; S.E. 3). In conclusion, the different protein supplements had dissimilar effects on ADG (greatest for FI) and mohair growth (greatest for CG). Factors responsible for these results are unclear, and the range of experimental or production conditions under which comparable ®ndings might occur are unknown and deserve further study. # 2000 Elsevier Science B.V. All rights reserved. Keywords: Angora goats; Mohair; Protein supplements
1. Introduction Angora goat farming in the US occurs in areas such as Texas, where cottonseed meal is the supplemental protein source of choice, but also in regions where other protein sources are available and relatively inexpensive. In comparison with cottonseed meal, protein sources such as hydrolyzed feather meal, corn *
Corresponding author. Tel.: 1-405-466-3836; fax: 1-405-466-3138. E-mail address: [email protected] (T. Sahlu)
gluten meal and ®sh meal are more resistant to ruminal degradation and contain high concentrations of sulfur amino acids. The US Angora goat, on a body weight (BW) basis, is one of the highest ¯eece-producing ruminants (Litherland and Sahlu, 1997). Mohair growth requires little energy but much protein is needed. In particular, requirements for the sulfur-containing amino acids cysteine and methionine are high (Reis and Sahlu, 1994). Based on amino acid concentrations, ruminal microbial protein cannot supply suf®cient sulfur amino acids for mohair growth (Qi et al., 1994).
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A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35
0.18; shorn on 22 February) and 26.6 mm ®ber diameter (S.E. 0.29), were used in the experiment. For allocation to treatments, ®rst animals were ranked or strati®ed by BW, then randomly allocated within BW grouping to the four treatments. After this initial allocation, means and S.D. for each treatment were calculated for BW, ¯eece weight and ®ber diameter. Some changes in treatment allocation were made to achieve similar means and variation within treatments for these variables. There were three treatments with 13 animals and one with 12. Once the four treatment groups had been formed, they were randomly assigned to the dietary treatments. Dietary treatments were different supplemental protein sources: cottonseed meal (CT; 41% CP, DM basis), corn gluten meal (CG; 73% CP, DM basis), hydrolyzed feather meal (FT; 90% CP, DM basis) and Menhaden ®sh meal (FI; 66% CP, DM basis). The protein sources composed between 10 and 24% of dietary DM and supplied 65±70% of total dietary CP (Table 1). Diets were formulated to be 65% total digestible nutrients and 18% CP (DM basis). The experiment commenced on 28 March and was 94 days in length. Doelings were housed individually, subjected to ambient temperature and natural photoperiod and had ad libitum access to water. Feed was offered once daily at a constant level, which was
Feeding protein sources with high concentrations of sulfur amino acids, which are generally resistant to ruminal degradation, can alter postruminal amino acid supply (Cecava et al., 1990). When additional sulfur amino acids have been supplied postruminally to the Angora goat, mohair growth increases (Sahlu and Fernandez, 1992). However, the array of amino acids needed for ¯eece-free BW gain is different from that needed for ®ber growth. Thus, diets containing supplemental protein sources promoting high BW gain may not necessarily do so for ®ber growth, which would be of special importance for growting, ®berproducing ruminants, such as yearling Angora doelings typically bred for kidding at 2 years of age. Therefore, objectives of this study were to determine if different common supplemental dietary protein sources have similar effects on live weight and mohair growth in yearling Angora doelings. 2. Materials and methods 2.1. Animals and experiment design Fifty-one 1-year-old Angora doelings, averaging 20 kg BW (S.E. 0.6), 3.0 kg ¯eece weight (S.E. Table 1 Diet composition (% dry matter) Item Ingredient composition Cottonseed hulls Ground corn Corn gluten meal Cottonseed meal Feather meal Fish meal Calcium carbonate Trace mineral premixb Vitamin premixc Chemical composition Crude protein Neutral detergent fiber Acid detergent fiber Ash a
Dieta CG
CT
FT
FI
43.20 41.00 14.00
36.90 37.20
40.80 47.10
40.60 43.50
0.65 1.00 0.20 18.2 49 31 4
23.80 0.90 1.00 0.20 18.9 44 24 6
10.10 0.80 1.00 0.20 19.4 48 28 6
14.50 0.25 1.00 0.20 18.6 46 31 5
CG: corn gluten meal; CT: cottonseed meal; FT: hydrolyzed feather meal; FI: ®sh meal. Contained 94±95% NaCl and greater than 0.2% Mn, 0.16% ferrous Fe, 0.14% ferric Fe, 0.033% CU, 0.10% Zn, 0.007% I and 0.005% Co. c Contained 220,000 IU/g Vitamin A, 2200 IU/g Vitamin D and 0.2 IU/g Vitamin E. b
A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35
calculated based on individual BW and assuming 0.119 M cal ME/kg0.75 BW required for BW maintenance and mohair growth and an additional 0.007 M cal ME/kg ADG for 100 g ADG (NRC, 1981), since at approximately 1 year of age the doelings still had growth potential and would need to increase in BW for kidding at 2 years of age. 2.2. Measures Doelings were weighed before feeding at 2 weeks intervals. Every 31 or 32 days, ®ber regrowth rate and ®ber diameter were estimated by clipping a 12 cm 12 cm square on the right mid-side. At the end of the experiment, doelings were shorn, ¯eece weight was measured and a grab sample was removed from the left mid-side for determination of ®ber diameter, stretched staple length and kemp. Greasy and clean mohair weights were determined according to ASTM (1988). Fiber diameter, percentage of kemp ®bers and diameter of kemp ®bers (patch samples) were determined on 3000±4000 snippets using an optical ®ber distribution analyzer (OFDA 100; Zellweger Uster, Inc., Charlotte, NC, USA). Feed ef®ciencies were calculated for ¯eece-free BW and ¯eece mass. On Days 45 and 90 of the experiment, ruminal ¯uid was sampled at 0, 2, 4 and 6 h after feeding. Concentrations of amino acids in protein supplements were determined as described by Puchala et al. (1995) using an AminoQuant system (Hewlett Packard, San Fernando, CA) and precolumn derivatization with ophthalaldehyde and 9-¯uorenylmethyl-chloroformate and UV detection. Ruminal ¯uid was sampled by stomach tube, acidi®ed with HCl, frozen at ÿ208C and later assayed for ammonia N by the phenolhypochlorite procedure of Broderick and Kang (1980) and VFA by gas chromatography (Hewlett Packard, Avondale, PA) as described by Lu et al. (1990). Daily samples of diets and feed refusals were used to form composites for three 31- or 32-day periods. Composite samples were ground to pass a 1 mm screen and analyzed for ash, CP (AOAC, 1984), NDF and ADF (Goering and Van Soest, 1970). 2.3. In situ N disappearance Three mature, ruminally cannulated Angora wethers were fed a diet composed of equal parts of
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the four diets with different protein sources at 120% of the ME requirement for BW maintenance. After a 2 weeks adaptation period, duplicate dacron bags (14 cm9 cm bags; 50 mm pore size) containing 3.1 g (DM) of the protein sources (ground to pass a 2 mm screen) were incubated in the rumen for 2, 4, 8, 12, 24 or 48 h. Bags were emersed in tap water before incubation. Also, loss through solubilization and washout through bag pores (i.e. 0 h disappearance) was estimated by soaking in water for 20 min. After removal of bags from the rumen, bags were immediately emersed in cold water then washed in cold water in a washing machine for 10 min, dried for 24 h at 558C and analyzed for N. Extent of ruminal N disappearance was calculated as described by érskov (1990) assuming a ruminal digesta passage rate of 0.05/h. 2.4. Statistical analyses Single time-point measures were analyzed with treatment in the model by general linear models procedures of SAS (1990), and differences among means were determined by least signi®cant difference and a protected F-test (P<0.05). Patch sample measures, including clean mohair growth rate, were analyzed separately for each 31- or 32-day period. Ruminal ¯uid measures with different days and times of sampling were analyzed by repeated measures analysis and the Wilks' Lambda test of signi®cance. 3. Results 3.1. Diet composition The dietary CP concentration was similar to that formulated for (Table 1), and NDF concentration did not differ greatly among treatments. The extent of in situ ruminal N disappearance was 38, 61, 33 and 51% for corn gluten, cottonseed, feather and ®sh meals, respectively. 3.2. ADG and ¯eece As expected, the quantity of feed refusals was relatively small, averaging 3.51% of DM intake. In accordance, DM intake was similar among treatments
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A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35
Table 2 Effects of dietary protein source on dry matter intake, average daily gain and ¯eece measures in yearling Angora doelingsa Dietb
Item
S.E.
CG
CT
FT
FI
DM intake (kg/day) Final body weight (with fleece; kg) Fleece-free ADG (g) Greasy fleece weight (kg) Fleece-free ADG:DM intake Greasy fleece weight:DM intake
0.71 25 35 b 4.4 a 49 b 44 a
0.69 24 33 b 3.6 b 47 b 35 b
0.72 24 35 b 3.4 b 50 b 34 b
0.71 26 50 a 3.4 b 69 a 34 b
0.02 1 4 0.1 5 2
Day 94 whole fleece measures Fiber diameter (mm) Stretched staple length (cm) Kemp (%)
31.6 10.2 0.28
29.9 10.1 0.14
29.9 9.0 0.18
29.6 9.1 0.20
0.7 0.4 0.03
Patch sample measures Clean mohair growth rate (mg cmÿ2 per day) Day 1±31 Day 32±62 Day 63±94 Fiber diamter (mm) Day 1±31 Day 32±62 Day 63±94 Kemp (%) Day 1±31 Day 32±62 Day 63±94 Kemp fiber diameter (mm) Day 1±31 Day 32±62 Day 63±94 a b
1.46 a 1.66 a 1.55 a 30.4 31.8 33.7 0.20 0.32 0.46 59 63 74
1.23 b 1.39 b 1.32 b 29.0 30.1 31.9 0.18 0.22 0.18 60 61 66
1.23 b 1.27 b 1.26 b 29.6 30.4 31.8 0.22 0.29 0.29 57 59 65
1.25 b 1.35 b 1.27 b 29.0 30.4 31.7 0.21 0.28 0.30 59 62 64
0.06 0.08 0.08 0.6 0.7 0.7 0.04 0.05 0.05 3 3 5
Within a row, means without a common letters differ (P<0.05). CG: corn gluten meal; CT: cottonseed meal; FT: hydrolyzed feather meal; FI: ®sh meal.
(P>0.10; Table 2). Fleece-free ADG was greatest (P<0.05) among treatments for FI, whereas greasy ¯eece weight was greatest (P<0.05) for CG. In part because of greatest ADG and grease ¯eece weight for FI and CG, respectively, ®nal BW was similar among treatments (P>0.10). Treatment differences in ratios of ¯eece-free ADG and grease ¯eece weight to DM intake were similar to those in ADG and grease ¯eece weight. Fiber diameter, stretched staple length and percentage of kemp ®ber were similar among treatments (P>0.10). Clean ®ber yield averaged 81% of grease ¯eece weight. In agreement with greatest grease ¯eece weight for CG, clean mohair growth rate was greatest
(P<0.05) among treatments for CG (Table 2). In general, the magnitude of difference was similar among 31- or 32-day periods. Other period measures (®ber diameter, percentage kemp and kemp ®ber diameter) were not affected by treatment (P>0.10). 3.3. Ruminal ¯uid ammonia N and VFA concentrations Day effects and interactions were nonsigni®cant (P>0.05) for ruminal ¯uid ammonia N and VFA concentrations. Interactions between time after feeding were signi®cant (P<0.05) for ruminal ¯uid concentrations of ammonia N and total VFA, but not for
A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35 Table 3 Effects of dietary protein source on ruminal ¯uid ammonia N and volatile fatty acid and concentrationsa Item
Dietb CG
S.E. CT
FT
Ammonia N (mg/dl) 0h 8b 2h 10 b 4h 8c 6h 4b
11 18 15 6
Total VFA (mM) 0h 2h 4h 6h
33 ab 57 a 50 48
29 bc 44 b 41 42
a a ab ab
6 11 10 5
FI b b bc ab
26 c 45 b 44 47
VFA molar percentages Acetate 61 63 62 Propionate 27 27 27 Butyrate 9.5 a 7.4 b 8.3 b Valerate 1.17 1.04 1.17 Isovalerate 0.9 b 1.0 b 1.0 b Isobutyrate 0.44 b 0.45 b 0.55 a Acetate:propionate 2.5 2.4 2.4
13 23 18 8
a a a a
1 2 2 1
37 a 51 ab 46 50
2 3 3 3
64 26 7.3 b 1.11 1.6 a 0.53 a 2.7
1 1 0.4 0.07 0.1 0.02 0.3
a
Within a row, means without a common letters differ (P<0.05). CG: corn gluten meal; CT: cottonseed meal; FT: hydrolyzed feather meal; FI: ®sh meal. b
molar VFA percentages. In general, ruminal ammonia N concentration was greater for CT and FI than for CG and FT, with differences at 6 h of lesser magnitude than at other times (Table 3). In general, differences among treatments and trends for differences in total VFA concentration were similar to those in ammonia N concentration. Molar percentages of acetate and propionate and the acetate to propionate ratio were similar among treatments (P>0.05). The butyrate molar percentage was greatest among treatments for CG (P<0.05). 4. Discussion 4.1. Ruminal protein disappearance and nitrogenous compounds Extents of ruminal disappearance of supplement protein estimated in situ were within ranges reported for other ruminant species of 15±55% for CG, 30±70% for FI, 29±40% for FT and 46±68% for CT (NRC,
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1985; Titgemeyer et al., 1989; Calsamiglia et al., 1995; Yoon et al., 1996; Piepenbrink and Schingoethe, 1997). Values for FI, FT and CT fell within four percentage units of mean values presented by NRC (1985), although the estimate for CG was seven percentage units less than that given by NRC (1985). The in situ ruminal protein disappearance estimates agree with differences among diets in ruminal ammonia N concentration. Ruminal ammonia N concentrations were low considering the relatively high dietary CP level, which can be at least partially explained by the high level of dietary inclusion of the protein sources, some of which were low in ruminal degradability, and moderate to high level of ground corn. Ruminal ammonia N concentrations at 6 h post-feeding were near the level of 2±5 mg/dl, often considered required for normal microbial growth (Satter and Slyter, 1974). Therefore, at later times after feeding ruminal availability of nitrogenous compounds might have limited microbial activity, particularly for CG and FT as suggested by their lower ruminal ammonia N levels at earlier times. In support, total VFA concentrations at 0 and 2 h were lower for CG and FT compared with CT and FI, and total VFA concentration at 4 and 6 h was numerically lowest among treatments for CG. Thus, energy availability for CG doelings may have been lowest among treatments, and restricted microbial protein synthesis is possible as well. In accordance, in a separate Latin square experiment with adult Angora wethers fed the same diets (our unpublished observations), ADF digestibility was lowest among treatments for CG (34, 39, 44 and 48% for CG, CT, FT and FI, respectively). Similarly, in other instances supplementation of diets high in protein sources not extensively degraded in the rumen with urea or protein highly degradable in the rumen has increased ruminal microbial growth, digestibility and (or) ruminant performance (Church et al., 1982; Aderibigbe and Church, 1983; Cecava et al., 1990; Lu et al., 1990; Sahlu et al., 1992). 4.2. ADG and ®ber growth In general, nutritional plane has affected ®ber growth and ADG similarly (Reis and Sahlu, 1994); however, such effects may depend on the nature of diets and animal characteristics. For example, in some
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A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35
instances an increased dietary level of ruminally undegraded protein has increased ¯eece growth without change in ADG (Sahlu et al., 1992; Huston et al., 1993). Likewise, in Merino sheep fed a roughagebased diet, FT supported a more rapid rate of wool growth than did CT but lower ADG (Neutze, 1990). 4.2.1. CG and ®ber growth Factors responsible for greatest clean mohair growth rate for doelings consuming the CG diet, yet greatest ADG for FI doelings are unlcear. Although, a plausible explanation for greatest ®ber growth by CG doelings was alluded to earlier. Perhaps ruminal availability of nitrogenous compounds limited VFA production and, thus, energy absorption to the greatest extent among treatments for CG. The amount of energy required by skin for ®ber growth is much less than that for peripheral muscle protein synthesis and maintenance (Harris and Lobley, 1991). In sheep, near maximal rates of wool growth can be sustained with use of a quantity of energy less than 5% of the basal metabolic rate (Black, 1987). Therefore, an energy limitation for CG that restricted nutrient use in peripheral muscle and(or) fat accretion may have caused nutrient partitioning to skin and increased ®ber growth (Harris and Lobley, 1991). The response to CG in ¯eece weight growth implies that the pro®le of available amino acids was suitable for use in ®ber growth. In accordance, greater ®ber growth for CG than for FT could relate to a more favorable array of amino acids available for use in ®ber growth, such as suggested by high supplemental protein source intakes of leucine and methionine for CG (leucine: 10.9, 3.8, 5.2 and 4.9 g/day; methionine: 1.7, 1.1, 0.7 and 1.9 g/day for CG, CT, FT and FI, respectively). Also, intestinal availability of amino acids in the protein supplements is unknown. Nonetheless, in the separate Latin square experiment referred to earlier (our unpublished observations), apparent total tract CP digestibility was 77, 71, 62 and 79% for CG, CT, FT and FI, respectively. This suggests lowest intestinal digestibility among protein supplements for FT, which is in agreement with ®ndings of Calsamiglia et al. (1995). 4.2.2. FI and ADG Ruminal ammonia N and VFA concentrations for FI do not indicate that ruminal microbial growth or digestion was restricted or limited by ruminal avail-
ability of nitrogenous compounds to the same degree as with CG. Thus, energy absorption might have been greater for FI versus CG and FT, and microbial protein synthesis may have differed as well. Greater energy availability could have allowed increased nutrient partitioning to ADG relative to conditions with CG and FT. Also, it is possible that the pro®le of absorbed amino acids elicited by dietary inclusion of FI was more favorable for ADG than that for CT, as indicated by relatively high supplemental protein source intakes for ®sh meal of lysine (0.9, 2.5, 1.5 and 4.6 g/day for CG, CT, FT and FI, respectively) and methionine. 5. Conclusions Results of this experiment indicate that dietary characteristics promoting high growth or BW gain may not be those most conducive to high mohair growth. In this particular instance, a diet with supplemental ®sh meal resulted in greater ADG than diets with feather, corn gluten or cottonseed meals, whereas corn gluten meal yielded greatest mohair growth. Further research is necessary to fully understand how dietary properties and nutrient status affects BW gain and mohair growth by yearling Angoras. Acknowledgements This research was supported by Project No. OKLX2000-01.
References AOAC, 1984. Of®cial Methods of Analysis, 14th Edition. Association of Of®cial Analytical Chemists, Arlington, VA, pp. 129±130. Aderibigbe, A.O., Church, D.C., 1983. Feather and hair meals for ruminants. 1. Effect of degree of processing on utilization of feather meal. J. Anim. Sci. 56, 1198±1207. ASTM, 1988. D584-90 Standard Test Method for Wool Content of Raw Wool-Laboratory Scale. Annual Book of ASTM Standards, Method D2720-77. American Society for Testing and Materials, Philadelphia, PA. Black, J.L., 1987. Mechanisms controlling the rate of growth, composition and morphology of wool. In: McGuirk, B.J. (Ed.), Merino Improvement Programs in Australia. Australian Wool Corporation, Melbourne, Australia, pp. 457±480.
A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35 Broderick, G.A., Kang, J.H., 1980. Automated simultaneous determination of ammonia and total amino acids in ruminal ¯uid and in vitro media. J. Dairy Sci. 63, 64±75. Calsamiglia, S., Stern, M.D., Firkins, J.L., 1995. Effects of protein source on nitrogen metabolism in continuous culture and intestinal digestion in vitro. J. Anim. Sci. 73, 1819±1827. Cecava, M.J., Merchen, N.R., Berger, L.L., Fahey, G.C., 1990. Intestinal supply of amino acids in sheep fed alkaline hydrogen peroxide-treated wheat straw-based diets supplemented with soybean meal or combinations of corn gluten meal and blood meal. J. Anim. Sci. 68, 467±477. Church, D.C., Daugherty, D.A., Kennick, W.H., 1982. Nutritional evaluation of feather and hair meals as protein sources for ruminants. J. Anim. Sci. 54, 337±344. Goering, H.K., Van Soest, P.J., 1970. Forage Fiber Analyses (Apparatus, Reagents, Procedures and Some Applications). Agric. Handbook No. 379. ARS, USDA, Washington, DC, pp. 1±12. Harris, P.M., Lobley, G.E., 1991. Amino acid and energy metabolism in the peripheral tissues of ruminants. In: Tsuda, T., Sasaki, Y., Kawashima, R. (Eds.), Physiological Aspects of Digestion and Metabolism in Ruminants. Academic Press, London, UK, pp. 201±230. Huston, J.E., Taylor, C.A., Lupton, C.J., Brooks, T.D., 1993. Effects of supplementation on intake, growth rate and ¯eece production by female Angora kid goats grazing rangeland. J. Anim. Sci. 71, 3124±3130. Litherland, A.J., Sahlu, T., 1997. A review of factors leading to high ¯eece production in Angora compared to down-producing goats. Sheep Goat Res. J. 12 (3), 99±104. 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 Rumin. Res. 3, 425±434. NRC, 1981. Nutrient Requirements for Goats: Angora, Dairy and Meat Goats in Temperate and Tropical Countries. National Academy of Science, Washington, DC, pp. 2±9.
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NRC, 1985. Ruminant Nitrogen Usage. National Academy of Science, Washington, DC, p. 33. érskov, E.R., 1990. Protein Nutrition in Ruminants, 2nd Edition. Academic Press, New York, pp. 43±93. Piepenbrink, M.S., Schingoethe, D.J., 1997. Ruminal degradation, amino acid composition and estimated intestinal digestibilities of four protein supplements. J. Anim. Sci. 75 (Suppl. 1), 95 (Abstr.). Puchala, R., Sahlu, T., Pierzynowski, S.G., Hart, S.P., 1995. Effects of amino acids administered to a perfused area of the skin in Angora goats. J. Anim. Sci. 73, 565±570. Qi, K., Lupton, C.J., Owens, F.N., 1994. A review of amino acid requirements for ®ber growth of sheep and Angora goats. Sheep Goat Res. J. 10 (3), 160±166. Reis, P.J., Sahlu, T., 1994. The nutritional control of the growth and properties of mohair and wool ®bers. A comparative review. J. Anim. Sci. 72, 1899±1907. Sahlu, T., Fernandez, J.M., 1992. Effect of intraperitoneal administration of lysine and methionine on mohair yield and quality in Angora goats. J. Anim. Sci. 70, 3188±3193. Sahlu, T., Hart, S.P., Fernandez, J.M., 1992. Nitrogen metabolism and blood metabolites of three goat breeds fed increasing amounts of protein. Small Rumin. Res. 10, 281±292. SAS, 1990. SAS User's Guide: Statistics Version 6, 4th Edition. SAS Inst. Inc., Cary, NC, pp. 891±996. Satter, L.D., Slyter, L.L., 1974. Effect of ammonia concentration on rumen microbial protein production in vitro. Br. J. Nutr. 32, 199±208. Titgemeyer, E.C., Merchen, N.R., Berger, L.L., 1989. Evaluation of soybean meal, corn gluten meal, blood meal and ®sh meal as sources of nitrogen and amino acids disappearing from the small intestine of steers. J. Anim. Sci. 67, 262±275. Yoon, I.K., Lindquist, K.J., Hogerholt, D.D., Stern, M.D., Crooker, B.A., Short, K.D., 1996. Variation in menhanden ®sh meal characteristics and their effects on ruminal protein degradation as assessed by various techniques. Anim. Feed Sci. Technol. 66, 13±19.
Effects of dietary protein sources on mohair growth and body weight of yearling Angora doelings A.J. Litherland, T. Sahlu*, C.A. Toerien, R. Puchala, K. Tesfai, A.L. Goetsch E (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK 73050, USA Received 25 April 1999; accepted 1 February 2000
Abstract Fifty-one yearling Angora doelings (200.6 kg initial body weight (BW)) were used to determine effects of different dietary protein sources on BW change and mohair growth. Diets consisted of approximately 40% roughage and 18±19% CP (DM basis), of which two-thirds was supplied by corn gluten meal (CG), cottonseed meal (CT), hydrolyzed feather meal (FT) or menhaden ®sh meal (FI); DM intake was restricted at approximately 0.7 kg/day. During the 94-day experiment, ¯eece-free ADG was greatest (P<0.05) for FI (35, 33, 35 and 50 g), whereas greasy ¯eece weight was greatest (P<0.05) for CG (4.4, 3.6, 3.4 and 3.4 kg for CG, CT, FT and FI, respectively). Likewise, mohair growth rate was greatest among treatments (P<0.05) for CG in each of the three 31- or 32-day periods. Ruminal ¯uid ammonia N concentration was 8, 11, 6 and 13 mg/dl (S.E. 1) immediately before feeding; 10, 18, 11 and 23 mg/dl (S.E. 2) at 2 h after feeding; 8, 15, 10 and 18 mg/dl (S.E. 2) at 4 h after feeding; and 4, 6, 5 and 8 mg/dl (S.E. 1) at 6 h after feeding for CG, CT, FT and FI, respectively. Total VFA concentration in ruminal ¯uid was similar among treatments (P>0.05) at 4 and 6 h, but was generally lower for CG and FT than for CT and FI immediately before feeding (29, 33, 26 and 37 mM; S.E. 2) and at 2 h after feeding (44, 57, 45 and 51 mM for CG, CT, FT and FI, respectively; S.E. 3). In conclusion, the different protein supplements had dissimilar effects on ADG (greatest for FI) and mohair growth (greatest for CG). Factors responsible for these results are unclear, and the range of experimental or production conditions under which comparable ®ndings might occur are unknown and deserve further study. # 2000 Elsevier Science B.V. All rights reserved. Keywords: Angora goats; Mohair; Protein supplements
1. Introduction Angora goat farming in the US occurs in areas such as Texas, where cottonseed meal is the supplemental protein source of choice, but also in regions where other protein sources are available and relatively inexpensive. In comparison with cottonseed meal, protein sources such as hydrolyzed feather meal, corn *
Corresponding author. Tel.: 1-405-466-3836; fax: 1-405-466-3138. E-mail address: [email protected] (T. Sahlu)
gluten meal and ®sh meal are more resistant to ruminal degradation and contain high concentrations of sulfur amino acids. The US Angora goat, on a body weight (BW) basis, is one of the highest ¯eece-producing ruminants (Litherland and Sahlu, 1997). Mohair growth requires little energy but much protein is needed. In particular, requirements for the sulfur-containing amino acids cysteine and methionine are high (Reis and Sahlu, 1994). Based on amino acid concentrations, ruminal microbial protein cannot supply suf®cient sulfur amino acids for mohair growth (Qi et al., 1994).
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A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35
0.18; shorn on 22 February) and 26.6 mm ®ber diameter (S.E. 0.29), were used in the experiment. For allocation to treatments, ®rst animals were ranked or strati®ed by BW, then randomly allocated within BW grouping to the four treatments. After this initial allocation, means and S.D. for each treatment were calculated for BW, ¯eece weight and ®ber diameter. Some changes in treatment allocation were made to achieve similar means and variation within treatments for these variables. There were three treatments with 13 animals and one with 12. Once the four treatment groups had been formed, they were randomly assigned to the dietary treatments. Dietary treatments were different supplemental protein sources: cottonseed meal (CT; 41% CP, DM basis), corn gluten meal (CG; 73% CP, DM basis), hydrolyzed feather meal (FT; 90% CP, DM basis) and Menhaden ®sh meal (FI; 66% CP, DM basis). The protein sources composed between 10 and 24% of dietary DM and supplied 65±70% of total dietary CP (Table 1). Diets were formulated to be 65% total digestible nutrients and 18% CP (DM basis). The experiment commenced on 28 March and was 94 days in length. Doelings were housed individually, subjected to ambient temperature and natural photoperiod and had ad libitum access to water. Feed was offered once daily at a constant level, which was
Feeding protein sources with high concentrations of sulfur amino acids, which are generally resistant to ruminal degradation, can alter postruminal amino acid supply (Cecava et al., 1990). When additional sulfur amino acids have been supplied postruminally to the Angora goat, mohair growth increases (Sahlu and Fernandez, 1992). However, the array of amino acids needed for ¯eece-free BW gain is different from that needed for ®ber growth. Thus, diets containing supplemental protein sources promoting high BW gain may not necessarily do so for ®ber growth, which would be of special importance for growting, ®berproducing ruminants, such as yearling Angora doelings typically bred for kidding at 2 years of age. Therefore, objectives of this study were to determine if different common supplemental dietary protein sources have similar effects on live weight and mohair growth in yearling Angora doelings. 2. Materials and methods 2.1. Animals and experiment design Fifty-one 1-year-old Angora doelings, averaging 20 kg BW (S.E. 0.6), 3.0 kg ¯eece weight (S.E. Table 1 Diet composition (% dry matter) Item Ingredient composition Cottonseed hulls Ground corn Corn gluten meal Cottonseed meal Feather meal Fish meal Calcium carbonate Trace mineral premixb Vitamin premixc Chemical composition Crude protein Neutral detergent fiber Acid detergent fiber Ash a
Dieta CG
CT
FT
FI
43.20 41.00 14.00
36.90 37.20
40.80 47.10
40.60 43.50
0.65 1.00 0.20 18.2 49 31 4
23.80 0.90 1.00 0.20 18.9 44 24 6
10.10 0.80 1.00 0.20 19.4 48 28 6
14.50 0.25 1.00 0.20 18.6 46 31 5
CG: corn gluten meal; CT: cottonseed meal; FT: hydrolyzed feather meal; FI: ®sh meal. Contained 94±95% NaCl and greater than 0.2% Mn, 0.16% ferrous Fe, 0.14% ferric Fe, 0.033% CU, 0.10% Zn, 0.007% I and 0.005% Co. c Contained 220,000 IU/g Vitamin A, 2200 IU/g Vitamin D and 0.2 IU/g Vitamin E. b
A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35
calculated based on individual BW and assuming 0.119 M cal ME/kg0.75 BW required for BW maintenance and mohair growth and an additional 0.007 M cal ME/kg ADG for 100 g ADG (NRC, 1981), since at approximately 1 year of age the doelings still had growth potential and would need to increase in BW for kidding at 2 years of age. 2.2. Measures Doelings were weighed before feeding at 2 weeks intervals. Every 31 or 32 days, ®ber regrowth rate and ®ber diameter were estimated by clipping a 12 cm 12 cm square on the right mid-side. At the end of the experiment, doelings were shorn, ¯eece weight was measured and a grab sample was removed from the left mid-side for determination of ®ber diameter, stretched staple length and kemp. Greasy and clean mohair weights were determined according to ASTM (1988). Fiber diameter, percentage of kemp ®bers and diameter of kemp ®bers (patch samples) were determined on 3000±4000 snippets using an optical ®ber distribution analyzer (OFDA 100; Zellweger Uster, Inc., Charlotte, NC, USA). Feed ef®ciencies were calculated for ¯eece-free BW and ¯eece mass. On Days 45 and 90 of the experiment, ruminal ¯uid was sampled at 0, 2, 4 and 6 h after feeding. Concentrations of amino acids in protein supplements were determined as described by Puchala et al. (1995) using an AminoQuant system (Hewlett Packard, San Fernando, CA) and precolumn derivatization with ophthalaldehyde and 9-¯uorenylmethyl-chloroformate and UV detection. Ruminal ¯uid was sampled by stomach tube, acidi®ed with HCl, frozen at ÿ208C and later assayed for ammonia N by the phenolhypochlorite procedure of Broderick and Kang (1980) and VFA by gas chromatography (Hewlett Packard, Avondale, PA) as described by Lu et al. (1990). Daily samples of diets and feed refusals were used to form composites for three 31- or 32-day periods. Composite samples were ground to pass a 1 mm screen and analyzed for ash, CP (AOAC, 1984), NDF and ADF (Goering and Van Soest, 1970). 2.3. In situ N disappearance Three mature, ruminally cannulated Angora wethers were fed a diet composed of equal parts of
31
the four diets with different protein sources at 120% of the ME requirement for BW maintenance. After a 2 weeks adaptation period, duplicate dacron bags (14 cm9 cm bags; 50 mm pore size) containing 3.1 g (DM) of the protein sources (ground to pass a 2 mm screen) were incubated in the rumen for 2, 4, 8, 12, 24 or 48 h. Bags were emersed in tap water before incubation. Also, loss through solubilization and washout through bag pores (i.e. 0 h disappearance) was estimated by soaking in water for 20 min. After removal of bags from the rumen, bags were immediately emersed in cold water then washed in cold water in a washing machine for 10 min, dried for 24 h at 558C and analyzed for N. Extent of ruminal N disappearance was calculated as described by érskov (1990) assuming a ruminal digesta passage rate of 0.05/h. 2.4. Statistical analyses Single time-point measures were analyzed with treatment in the model by general linear models procedures of SAS (1990), and differences among means were determined by least signi®cant difference and a protected F-test (P<0.05). Patch sample measures, including clean mohair growth rate, were analyzed separately for each 31- or 32-day period. Ruminal ¯uid measures with different days and times of sampling were analyzed by repeated measures analysis and the Wilks' Lambda test of signi®cance. 3. Results 3.1. Diet composition The dietary CP concentration was similar to that formulated for (Table 1), and NDF concentration did not differ greatly among treatments. The extent of in situ ruminal N disappearance was 38, 61, 33 and 51% for corn gluten, cottonseed, feather and ®sh meals, respectively. 3.2. ADG and ¯eece As expected, the quantity of feed refusals was relatively small, averaging 3.51% of DM intake. In accordance, DM intake was similar among treatments
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A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35
Table 2 Effects of dietary protein source on dry matter intake, average daily gain and ¯eece measures in yearling Angora doelingsa Dietb
Item
S.E.
CG
CT
FT
FI
DM intake (kg/day) Final body weight (with fleece; kg) Fleece-free ADG (g) Greasy fleece weight (kg) Fleece-free ADG:DM intake Greasy fleece weight:DM intake
0.71 25 35 b 4.4 a 49 b 44 a
0.69 24 33 b 3.6 b 47 b 35 b
0.72 24 35 b 3.4 b 50 b 34 b
0.71 26 50 a 3.4 b 69 a 34 b
0.02 1 4 0.1 5 2
Day 94 whole fleece measures Fiber diameter (mm) Stretched staple length (cm) Kemp (%)
31.6 10.2 0.28
29.9 10.1 0.14
29.9 9.0 0.18
29.6 9.1 0.20
0.7 0.4 0.03
Patch sample measures Clean mohair growth rate (mg cmÿ2 per day) Day 1±31 Day 32±62 Day 63±94 Fiber diamter (mm) Day 1±31 Day 32±62 Day 63±94 Kemp (%) Day 1±31 Day 32±62 Day 63±94 Kemp fiber diameter (mm) Day 1±31 Day 32±62 Day 63±94 a b
1.46 a 1.66 a 1.55 a 30.4 31.8 33.7 0.20 0.32 0.46 59 63 74
1.23 b 1.39 b 1.32 b 29.0 30.1 31.9 0.18 0.22 0.18 60 61 66
1.23 b 1.27 b 1.26 b 29.6 30.4 31.8 0.22 0.29 0.29 57 59 65
1.25 b 1.35 b 1.27 b 29.0 30.4 31.7 0.21 0.28 0.30 59 62 64
0.06 0.08 0.08 0.6 0.7 0.7 0.04 0.05 0.05 3 3 5
Within a row, means without a common letters differ (P<0.05). CG: corn gluten meal; CT: cottonseed meal; FT: hydrolyzed feather meal; FI: ®sh meal.
(P>0.10; Table 2). Fleece-free ADG was greatest (P<0.05) among treatments for FI, whereas greasy ¯eece weight was greatest (P<0.05) for CG. In part because of greatest ADG and grease ¯eece weight for FI and CG, respectively, ®nal BW was similar among treatments (P>0.10). Treatment differences in ratios of ¯eece-free ADG and grease ¯eece weight to DM intake were similar to those in ADG and grease ¯eece weight. Fiber diameter, stretched staple length and percentage of kemp ®ber were similar among treatments (P>0.10). Clean ®ber yield averaged 81% of grease ¯eece weight. In agreement with greatest grease ¯eece weight for CG, clean mohair growth rate was greatest
(P<0.05) among treatments for CG (Table 2). In general, the magnitude of difference was similar among 31- or 32-day periods. Other period measures (®ber diameter, percentage kemp and kemp ®ber diameter) were not affected by treatment (P>0.10). 3.3. Ruminal ¯uid ammonia N and VFA concentrations Day effects and interactions were nonsigni®cant (P>0.05) for ruminal ¯uid ammonia N and VFA concentrations. Interactions between time after feeding were signi®cant (P<0.05) for ruminal ¯uid concentrations of ammonia N and total VFA, but not for
A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35 Table 3 Effects of dietary protein source on ruminal ¯uid ammonia N and volatile fatty acid and concentrationsa Item
Dietb CG
S.E. CT
FT
Ammonia N (mg/dl) 0h 8b 2h 10 b 4h 8c 6h 4b
11 18 15 6
Total VFA (mM) 0h 2h 4h 6h
33 ab 57 a 50 48
29 bc 44 b 41 42
a a ab ab
6 11 10 5
FI b b bc ab
26 c 45 b 44 47
VFA molar percentages Acetate 61 63 62 Propionate 27 27 27 Butyrate 9.5 a 7.4 b 8.3 b Valerate 1.17 1.04 1.17 Isovalerate 0.9 b 1.0 b 1.0 b Isobutyrate 0.44 b 0.45 b 0.55 a Acetate:propionate 2.5 2.4 2.4
13 23 18 8
a a a a
1 2 2 1
37 a 51 ab 46 50
2 3 3 3
64 26 7.3 b 1.11 1.6 a 0.53 a 2.7
1 1 0.4 0.07 0.1 0.02 0.3
a
Within a row, means without a common letters differ (P<0.05). CG: corn gluten meal; CT: cottonseed meal; FT: hydrolyzed feather meal; FI: ®sh meal. b
molar VFA percentages. In general, ruminal ammonia N concentration was greater for CT and FI than for CG and FT, with differences at 6 h of lesser magnitude than at other times (Table 3). In general, differences among treatments and trends for differences in total VFA concentration were similar to those in ammonia N concentration. Molar percentages of acetate and propionate and the acetate to propionate ratio were similar among treatments (P>0.05). The butyrate molar percentage was greatest among treatments for CG (P<0.05). 4. Discussion 4.1. Ruminal protein disappearance and nitrogenous compounds Extents of ruminal disappearance of supplement protein estimated in situ were within ranges reported for other ruminant species of 15±55% for CG, 30±70% for FI, 29±40% for FT and 46±68% for CT (NRC,
33
1985; Titgemeyer et al., 1989; Calsamiglia et al., 1995; Yoon et al., 1996; Piepenbrink and Schingoethe, 1997). Values for FI, FT and CT fell within four percentage units of mean values presented by NRC (1985), although the estimate for CG was seven percentage units less than that given by NRC (1985). The in situ ruminal protein disappearance estimates agree with differences among diets in ruminal ammonia N concentration. Ruminal ammonia N concentrations were low considering the relatively high dietary CP level, which can be at least partially explained by the high level of dietary inclusion of the protein sources, some of which were low in ruminal degradability, and moderate to high level of ground corn. Ruminal ammonia N concentrations at 6 h post-feeding were near the level of 2±5 mg/dl, often considered required for normal microbial growth (Satter and Slyter, 1974). Therefore, at later times after feeding ruminal availability of nitrogenous compounds might have limited microbial activity, particularly for CG and FT as suggested by their lower ruminal ammonia N levels at earlier times. In support, total VFA concentrations at 0 and 2 h were lower for CG and FT compared with CT and FI, and total VFA concentration at 4 and 6 h was numerically lowest among treatments for CG. Thus, energy availability for CG doelings may have been lowest among treatments, and restricted microbial protein synthesis is possible as well. In accordance, in a separate Latin square experiment with adult Angora wethers fed the same diets (our unpublished observations), ADF digestibility was lowest among treatments for CG (34, 39, 44 and 48% for CG, CT, FT and FI, respectively). Similarly, in other instances supplementation of diets high in protein sources not extensively degraded in the rumen with urea or protein highly degradable in the rumen has increased ruminal microbial growth, digestibility and (or) ruminant performance (Church et al., 1982; Aderibigbe and Church, 1983; Cecava et al., 1990; Lu et al., 1990; Sahlu et al., 1992). 4.2. ADG and ®ber growth In general, nutritional plane has affected ®ber growth and ADG similarly (Reis and Sahlu, 1994); however, such effects may depend on the nature of diets and animal characteristics. For example, in some
34
A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35
instances an increased dietary level of ruminally undegraded protein has increased ¯eece growth without change in ADG (Sahlu et al., 1992; Huston et al., 1993). Likewise, in Merino sheep fed a roughagebased diet, FT supported a more rapid rate of wool growth than did CT but lower ADG (Neutze, 1990). 4.2.1. CG and ®ber growth Factors responsible for greatest clean mohair growth rate for doelings consuming the CG diet, yet greatest ADG for FI doelings are unlcear. Although, a plausible explanation for greatest ®ber growth by CG doelings was alluded to earlier. Perhaps ruminal availability of nitrogenous compounds limited VFA production and, thus, energy absorption to the greatest extent among treatments for CG. The amount of energy required by skin for ®ber growth is much less than that for peripheral muscle protein synthesis and maintenance (Harris and Lobley, 1991). In sheep, near maximal rates of wool growth can be sustained with use of a quantity of energy less than 5% of the basal metabolic rate (Black, 1987). Therefore, an energy limitation for CG that restricted nutrient use in peripheral muscle and(or) fat accretion may have caused nutrient partitioning to skin and increased ®ber growth (Harris and Lobley, 1991). The response to CG in ¯eece weight growth implies that the pro®le of available amino acids was suitable for use in ®ber growth. In accordance, greater ®ber growth for CG than for FT could relate to a more favorable array of amino acids available for use in ®ber growth, such as suggested by high supplemental protein source intakes of leucine and methionine for CG (leucine: 10.9, 3.8, 5.2 and 4.9 g/day; methionine: 1.7, 1.1, 0.7 and 1.9 g/day for CG, CT, FT and FI, respectively). Also, intestinal availability of amino acids in the protein supplements is unknown. Nonetheless, in the separate Latin square experiment referred to earlier (our unpublished observations), apparent total tract CP digestibility was 77, 71, 62 and 79% for CG, CT, FT and FI, respectively. This suggests lowest intestinal digestibility among protein supplements for FT, which is in agreement with ®ndings of Calsamiglia et al. (1995). 4.2.2. FI and ADG Ruminal ammonia N and VFA concentrations for FI do not indicate that ruminal microbial growth or digestion was restricted or limited by ruminal avail-
ability of nitrogenous compounds to the same degree as with CG. Thus, energy absorption might have been greater for FI versus CG and FT, and microbial protein synthesis may have differed as well. Greater energy availability could have allowed increased nutrient partitioning to ADG relative to conditions with CG and FT. Also, it is possible that the pro®le of absorbed amino acids elicited by dietary inclusion of FI was more favorable for ADG than that for CT, as indicated by relatively high supplemental protein source intakes for ®sh meal of lysine (0.9, 2.5, 1.5 and 4.6 g/day for CG, CT, FT and FI, respectively) and methionine. 5. Conclusions Results of this experiment indicate that dietary characteristics promoting high growth or BW gain may not be those most conducive to high mohair growth. In this particular instance, a diet with supplemental ®sh meal resulted in greater ADG than diets with feather, corn gluten or cottonseed meals, whereas corn gluten meal yielded greatest mohair growth. Further research is necessary to fully understand how dietary properties and nutrient status affects BW gain and mohair growth by yearling Angoras. Acknowledgements This research was supported by Project No. OKLX2000-01.
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A.J. Litherland et al. / Small Ruminant Research 38 (2000) 29±35 Broderick, G.A., Kang, J.H., 1980. Automated simultaneous determination of ammonia and total amino acids in ruminal ¯uid and in vitro media. J. Dairy Sci. 63, 64±75. Calsamiglia, S., Stern, M.D., Firkins, J.L., 1995. Effects of protein source on nitrogen metabolism in continuous culture and intestinal digestion in vitro. J. Anim. Sci. 73, 1819±1827. Cecava, M.J., Merchen, N.R., Berger, L.L., Fahey, G.C., 1990. Intestinal supply of amino acids in sheep fed alkaline hydrogen peroxide-treated wheat straw-based diets supplemented with soybean meal or combinations of corn gluten meal and blood meal. J. Anim. Sci. 68, 467±477. Church, D.C., Daugherty, D.A., Kennick, W.H., 1982. Nutritional evaluation of feather and hair meals as protein sources for ruminants. J. Anim. Sci. 54, 337±344. Goering, H.K., Van Soest, P.J., 1970. Forage Fiber Analyses (Apparatus, Reagents, Procedures and Some Applications). Agric. Handbook No. 379. ARS, USDA, Washington, DC, pp. 1±12. Harris, P.M., Lobley, G.E., 1991. Amino acid and energy metabolism in the peripheral tissues of ruminants. In: Tsuda, T., Sasaki, Y., Kawashima, R. (Eds.), Physiological Aspects of Digestion and Metabolism in Ruminants. Academic Press, London, UK, pp. 201±230. Huston, J.E., Taylor, C.A., Lupton, C.J., Brooks, T.D., 1993. Effects of supplementation on intake, growth rate and ¯eece production by female Angora kid goats grazing rangeland. J. Anim. Sci. 71, 3124±3130. Litherland, A.J., Sahlu, T., 1997. A review of factors leading to high ¯eece production in Angora compared to down-producing goats. Sheep Goat Res. J. 12 (3), 99±104. 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 Rumin. Res. 3, 425±434. NRC, 1981. Nutrient Requirements for Goats: Angora, Dairy and Meat Goats in Temperate and Tropical Countries. National Academy of Science, Washington, DC, pp. 2±9.
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NRC, 1985. Ruminant Nitrogen Usage. National Academy of Science, Washington, DC, p. 33. érskov, E.R., 1990. Protein Nutrition in Ruminants, 2nd Edition. Academic Press, New York, pp. 43±93. Piepenbrink, M.S., Schingoethe, D.J., 1997. Ruminal degradation, amino acid composition and estimated intestinal digestibilities of four protein supplements. J. Anim. Sci. 75 (Suppl. 1), 95 (Abstr.). Puchala, R., Sahlu, T., Pierzynowski, S.G., Hart, S.P., 1995. Effects of amino acids administered to a perfused area of the skin in Angora goats. J. Anim. Sci. 73, 565±570. Qi, K., Lupton, C.J., Owens, F.N., 1994. A review of amino acid requirements for ®ber growth of sheep and Angora goats. Sheep Goat Res. J. 10 (3), 160±166. Reis, P.J., Sahlu, T., 1994. The nutritional control of the growth and properties of mohair and wool ®bers. A comparative review. J. Anim. Sci. 72, 1899±1907. Sahlu, T., Fernandez, J.M., 1992. Effect of intraperitoneal administration of lysine and methionine on mohair yield and quality in Angora goats. J. Anim. Sci. 70, 3188±3193. Sahlu, T., Hart, S.P., Fernandez, J.M., 1992. Nitrogen metabolism and blood metabolites of three goat breeds fed increasing amounts of protein. Small Rumin. Res. 10, 281±292. SAS, 1990. SAS User's Guide: Statistics Version 6, 4th Edition. SAS Inst. Inc., Cary, NC, pp. 891±996. Satter, L.D., Slyter, L.L., 1974. Effect of ammonia concentration on rumen microbial protein production in vitro. Br. J. Nutr. 32, 199±208. Titgemeyer, E.C., Merchen, N.R., Berger, L.L., 1989. Evaluation of soybean meal, corn gluten meal, blood meal and ®sh meal as sources of nitrogen and amino acids disappearing from the small intestine of steers. J. Anim. Sci. 67, 262±275. Yoon, I.K., Lindquist, K.J., Hogerholt, D.D., Stern, M.D., Crooker, B.A., Short, K.D., 1996. Variation in menhanden ®sh meal characteristics and their effects on ruminal protein degradation as assessed by various techniques. Anim. Feed Sci. Technol. 66, 13±19.