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Effects of zinc-methionine on performance of Angora goats
Small Ruminant Research 33 (1999) 1±8
Effects of zinc-methionine on performance of Angora goats R. Puchalaa, T. Sahlua,*, J.J. Davis1,a a
E (Kika) de la Garza Institute for Goat Research, P. O. Box 730, Langston, OK 73050, USA Accepted 25 November 1998
Abstract Effects of supplementation with zinc-methionine (Zn-Met), a source of potentially rumen protected methionine and zinc (Zinpro 40, Edina, MN), on mohair growth, BW gain and blood metabolites were investigated in Angora goats. Forty yearling Angora goats (20 wethers and 20 doelings) were offered a basal diet (11.2% CP, 22 ppm Zn, 2.3 Mcal/kg DM) at 4% BWof DM for 120 days. The treatments (1±5) were: 1, 3 and 5 g/day of Zn-Met, 150 mg/day of zinc oxide and control (no supplementation). Supplementation of the diet with Zn-Met (1, 3 and 5 g/day of Zn-Met) increased (P < 0.07) ADG (65.5 versus 55.9 g/day for control). ADG for goats receiving ZnO was lower (P < 0.04) than for goats receiving a similar amount of Zn from 3 g/d Zn-Met (50.5 versus 62.9 g/day), although Zn-Met inclusion in the diet numerically (P 0.13) increased clean mohair production, which also changed quadratically (P < 0.09) as Zn-Met level increased (1.59, 1.51, 1.62, 1.60 and 1.59 kg in 120 days) for treatments 1, 2, 3, 4 and 5, respectively. Supplementation of the diet with Zn-Met increased (P < 0.03) plasma Zn concentration (0.92 versus 0.72 mg/l for control); there were no differences in plasma Zn concentration between goats receiving the ZnO supplement and goats receiving a similar amount of Zn from Zn-Met (0.87 versus 0.92 mg/l; P > 0.56). Plasma methionine concentration was not affected by Zn-Met supplementation (P > 0.53). In summary, supplementation of a Zn-adequate diet with Zn-Met increased ADG by yearling Angora goats regardless of level of Zn-Met added. Supplementation of 1 g Zn-Met may have positive effect on ADG and mohair growth when diet contains about 20 ppm Zn. # 1999 Elsevier Science B.V. All rights reserved. Keywords: Angora goats; Zinc-methionine; Mohair
1. Introduction The essential amino acids lysine, methionine (Met) and cyst(e)ine stimulate wool and mohair growth (Sahlu and Fernandez, 1992; Reis and Sahlu, 1994; Puchala et al., 1995). Reis and Tunks (1978); Reis et al. (1990), using dietary mixtures of amino acids, found that omission of Met reduced wool growth *Corresponding author. Tel.: +1-405-466-3836; fax: +1-405466-3138; e-mail: [email protected] 1 Institute for Integrated Agricultural Development (IIAD) RMB 1145, Rutherglen, Victoria 3685, Australia.
and decreased both length growth rate and diameter. Skin and ®ber (wool, mohair) impose heavy demands on the utilization of circulating sulfur amino acids. Black and Reis (1979) predicted that 80% of the total free blood pool of combined cysteine and Met would be used for ®ber growth. Being responsible for the initiation of protein synthesis, Met is important in ®ber growth. Met can be converted by transulfuration to cystine mainly in the liver (Cobon et al., 1988), but also to some extent in other tissues (Radclife and Egan, 1978; Benevenga et al., 1983). Supplementation with speci®c amino acids has in¯uenced mohair growth in Angora goats. Sahlu
0921-4488/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 4 8 8 ( 9 8 ) 0 0 1 9 4 - 1
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R. Puchala et al. / Small Ruminant Research 33 (1999) 1±8
and Fernandez (1992) evaluated responses to intraperitoneal administration of amino acids in Angora wethers fed a 13% CP diet. Infusion of 1 g/day of Met increased clean mohair yield from 7.6 to 8.0 g/ 100 cm2 of skin. Assuming that the average percentage of methionine in protein is 2%, 1 g of Met substitutes for 50 g of protein. Considering the feed intake of animals used by Sahlu and Fernandez (1992), infused Met of 1 g/day was equivalent to increasing the dietary protein level from 13 to 18%. It may be cost effective to increase absorption of most limiting amino acids such as Met through dietary supplementation of speci®c amino acids, rather than increasing absorption of a large number of amino acids through increase of the total dietary CP level. Apart from the major nutrients such as protein, many vitamins and trace elements are essential for ®ber growth. Zinc (Zn) functions directly in the process of wool growth; thus, Zn de®ciencies can seriously affect wool growth (Reis, 1989). Zinc is needed for the functions of over 100 enzymes, and essential for DNA, RNA, protein synthesis and, as such, cell division. White et al. (1994) suggested that primary impact of Zn de®ciency on wool growth is through impaired protein synthesis. Commercially available Zn-Met complexes provide both Zn and Met. Heinrichs and Conrad (1983) reported that Met from a Zn-Met complex was not utilized by mixed ruminal inoculum in vitro, implying passage to the small intestine without microbial alteration. Hempe and Cousins (1989) suggested that ZnMet and Cu-Lys complexes are transported intact from the intestinal lumen into mucosal cells. If Zn-Met is absorbed and transported without modi®cation, the complex may provide a means of increasing tissue supply of Met, which should increase animal productivity when Met is limiting. Therefore, objectives of this study were to investigate effects of dietary supplementation with Zn-Met (Zinpro 40, Edina, MN) or zinc oxide on mohair growth, BW gain and concentrations of blood metabolites in Angora goats. 2. Materials and methods Forty yearling Angora goats (BW 24.5 2.0 kg, twenty wethers and twenty doelings) were adapted to a basal diet (Table 1) fed at 4% BW (DM basis). The
Table 1 Composition of experimental diet Item
Concentration (%)
Ingredient Cottonseed hulls Ground corn Soybean meal Trace mineral salta Calcium carbonate Vitamin premixb Dicalcium phosphate
46.0 45.0 7.0 1.0 0.5 0.2 0.3
Nutrients CP TDN
11.2 64.2
a
Containing (in percentages) NaCl, 94 to 95; Mn, >0.2; ferrous Fe, >0.16; ferric Fe, >0.14; Cu, >0.033; Zn, >0.10; I, >0.007; Co, >0.005. b Each gram contained 2200 IU of vitamin A, 2200 IU of vitamin D, and 0.2 IU of vitamin E.
diet was formulated to be adequate in CP, energy, vitamins and minerals for these classes of goats. Following the adaptation period goats were blocked by BW and sex and randomly assigned to one of ®ve dietary supplements: 1 g Zn-Met (40 mg Zn, 100 mg Met) 14 mg CuO (12 mg Cu); 3 g Zn-Met (120 mg Zn, 300 mg Met) 45 mg CuO (36 mg Cu); 5 g ZnMet (200 mg Zn, 500 mg Met) 75 mg CuO (60 mg Cu); 150 mg ZnO (120 mg Zn) 45 mg CuO (36 mg Cu); control (no supplement). Cu is considered to be a major Zn antagonist and, hence, was provided together with Zn supplementation to avoid Cu de®ciency (Rojas et al., 1995). The basal diet contained 22 ppm of Zn and 5.3 ppm of Cu. Supplementation of 150 mg ZnO and 3 g of Zn-Met provided a similar amount of supplemental Zn (120 mg/day). Goats were housed in individual crates with expanded metal ¯oors. Animals were fed once daily at 08:00 hours and had free access to water; treatments were applied for 120 days. Intake was calculated at 4% BW and adjusted weekly after weighing. All goats were shorn at the beginning and end of the experiment. A mid-side sample was collected from each ¯eece for staple length and mohair diameter analyses. On days 30, 60, 90 and 120 blood was obtained via jugular venipuncture at 2 h postprandial. Blood was collected into four 7 ml tubes containing potassium oxalate± sodium ¯uoride, K3 EDTA or sodium heparin (Becton
R. Puchala et al. / Small Ruminant Research 33 (1999) 1±8
Dickinson, Vacutainer systems Rutherford, NJ). The tubes were immediately chilled in an ice bath, transported to the laboratory and centrifuged at 1500 g at 48C for 20 min. Plasma aliquots were stored at ÿ558C until analyses. Ruminal ¯uid samples were obtained using a stomach tube immediately after blood sampling. In the last week of the experiment, feces and urine were collected daily for 5 days from each wether. Each fecal and urine sample was mixed and a 10% subsample from each collection was bulked over the 5day period. The total amounts of feed offered and refused by the animals were recorded and subsamples bulked for subsequent analyses. Samples of feed ingredients, feed refusals and feces were dried in a forced-air oven (608C), ground to pass a 2 mm screen and analyzed for DM, total N, gross energy and ADF. Samples of urine were freeze-dried prior N to analysis. Plasma for amino acid estimation (0.45 ml) was deproteinized using 0.05 ml of 50% (w/v) 5-sulfosalicylic acid with added internal standards (sarcosine and norvaline). The mixture was vortexed, centrifuged (1500 g; 48C; 10 min) and placed in sample vials. Degreased mohair samples (20 mg) were prepared for amino acid analysis by adding dithiodipropionic acid solution (to convert cystine to S-(2-carboxyethyltio)L-Cysteine), norvaline and sarcosine (internal standards) and digested in 6N HCl using a microwave digestion system (MDS 2000; CEM Corp., Matthews, NC). Amino acid analyses were performed on an AminoQuant system (Hewlett Pacard, San Fernando, CA) using precolumn derivatization with o-phthalaldehyde and 9-¯uorenylmethylchloroformate and UV detection. Plasma Zn, Mg, Fe and Cu concentrations were determined using plasma emission spectroscopy (Applied Research Laboratories, Inc., Dearborn, MI), according to the method of Seeley and Kinsey (1982). Plasma glucose concentrations were analyzed colorimetrically using a Sigma glucose diagnostic kit (Catalog No. 315; Sigma Diagnostic, St. Louis, MO). A kit using an enzymatic method was used to quantify NEFA (Catalog No 990-75401; Wako Pure Chemical Industries, Osaka, Japan). Sigma kits (Sigma Diagnostic, St. Louis, MO) were used to determine plasma creatinine and total protein concentrations. Plasma urea N was determined as described by Chaney and Marbach (1962). VFA were analyzed by adding 1 ml of 25% (w/v) metaphosphoric acid to 5 ml of ruminal
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¯uid. The solution was allowed to stand for 30 min and then centrifuged for 20 min at 10 000 g. Aliquots of the supernatant were subjected to gas chromatography (Hewlett Packard Co., Avondale, PA) utilizing a 1.98 4 mm i.d. glass column packed with 15% SP-1200 plus 1% H3PO4 on 100/120 Chromosorb W AW (Supelco, Bellefonte, PA). Staple length and greasy and clean mohair yields were determined according to ASTM Standards (American Society for Testing and Materials, 1988). Fiber diameter was determined using the Peyer FDA 200 System (Wallerau, Switzerland). The general linear models procedure of SAS (1990) was used to analyze data. Data were analyzed as a completely randomized design with the treatment, sex and their interaction in the model for feed intake, performance and mohair growth and characteristics. There were no effects of sex or the sex treatment interaction (P > 0.05). Blood measurements were ®rst analyzed as a split-plot in time, although time effects and time treatment interactions were nonsigni®cant (P > 0.05). Contrasts were conducted for dietary adition of Zn-Met, linear and quadratic effects of nonzero dietary Zn-Met level and for Zn-Met versus 3 g ZnMet (Steel and Torrie, 1980). 3. Results Initial BW and feed intake were similar among treatments (P > 0.1; Table 2). Supplementation of the diet with Zn-Met (1, 3 and 5 g/day Zn-Met) increased (P < 0.07) ADG (65.5 versus 55.9 g/day for control). ADG for goats receiving the ZnO (120 mg/day Zn) supplement was lower (P < 0.04) than for goats receiving a similar amount of Zn from Zn-Met (50.5 versus 62.9 g/day). Zn-Met treatments had quadratic effects (P < 0.09) on greasy and clean mohair production (Table 2). Mohair diameter was similar among groups (P > 0.1); however, staple length was lower for ZnO than for 3 g/day Zn-Met (9.5 versus 10.5 cm; P < 0.03). Plasma glucose and urea concentrations were not affected (P > 0.1) by dietary treatment Table 3). Supplementation of the diet with Zn-Met treatments (1, 3 and 5 g/day ZnMet) increased (P < 0.03) plasma Zn concentration (0.92 versus 0.72 mg/l for control), however no difference in plasma Zn concentration was seen between
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R. Puchala et al. / Small Ruminant Research 33 (1999) 1±8
Table 2 Initial weight, feed intake, ADG and mohair production and quality for Angora goats supplemented with Zn-Met complex or ZnO for 120 days Item
Initial weight (kg) Feed intake (kg/day) ADG (g/day) Greasy mohair (kg) Clean mohair (kg) Diameter (mm) Length (cm)
Treatmenta
SEM
Control
1 Zn-Met
3 Zn-Met
5 Zn-Met
ZnO
24.0 0.78 55.9 1.84 1.57 29.0 10.3
24.2 0.92 67.0 1.89 1.59 29.8 10.0
24.4 0.85 62.9 1.83 1.51 30.3 10.5
24.0 0.88 66.7 1.94 1.62 29.5 10.0
24.6 0.80 50.5 1.90 1.60 30.0 9.5
1.3 0.06 4.1 0.05 0.04 0.9 0.3
Treatment contrast, P value Zn-Met, addition
Zn-Met, linear
Zn-Met, quadratic
3 Zn-Met vs ZnO
0.87 0.52 0.07 0.13 0.13 0.46 0.66
0.86 0.97 0.22 0.90 0.80 0.73 0.47
0.86 0.59 0.49 0.09 0.09 0.28 0.14
0.96 0.69 0.04 0.43 0.21 0.48 0.03
a
54% concentrate basal diet fed at 4% BW; control no added Zn-Met, ZnO or CuO, 1 Zn-Met 1 g Zn-Met (40 mg Zn, 100 mg Met) 14 mg CuO, 3 Zn-Met 3 g Zn-Met (120 mg Zn, 300 mg Met) 45 mg CuO, 5 Zn-Met 5 g Zn-Met (200 mg Zn, 500 mg Met) 75 mg CuO, ZnO 150 mg ZnO (120 mg Zn) 45 mg CuO.
goats receiving the ZnO or goats receiving a similar amount of Zn from Zn-Met (0.87 versus 0.92 mg/l; P > 0.10).PlasmaCuconcentrationsweresimilaramong all treatments. Plasma-essential amino acid concentrations were not affected by dietary treatment (P > 0.1; values not shown). There were no diet effects on concentrations of other analyzed blood and ruminal constituents or DM and N digestibilities (P > 0.1; values not shown), and the amino acid pro®le of mohair was unaffected by treatment (P > 0.1; values not shown). 4. Discussion 4.1. Zn-Met and ZnO In the present experiment dietary supplementation of Zn-Met increased ADG. This result is supported by
similar reports of improved animal performance with Zn-Met supplementation. Spears (1989) reported that heifers fed a corn-based diet (25 ppm of Zn) supplemented with 25 mg Zn as Zn-Met had higher ADG than controls. Aguilar and Jordan (1990) and Kellogg et al. (1989) noted increased milk production by lactating dairy cows as result of dietary Zn-Met supplementation. Although, in some studies Zn-Met has not altered animal performance. Martin et al. (1987) using steers and Stobart et al. (1987) using lambs did not observe differences in ADG or feed ef®ciency between animals fed Zn-Met and those fed control diets. Similarly, Greene et al. (1988) found similar ADG and feed ef®ciencies for steers consuming diets with or without Zn-Met, but this may have involved a relatively high Zn level in the control diet (i.e., 81 ppm Zn). Our group receiving ZnO gained BW at the rate fairly similar to that for Zn-Met treatments up to 80
Table 3 Plasma metabolites concentration for Angora goats supplemented with Zn-Met complex or ZnO for 120 days Item
Glucose (mg/dl) Urea N (mg/dl) Zn (mg/l) Cu (mg/l) a
Treatmenta
SEM
Control
1 Zn-Met
3 Zn-Met
5 Zn-Met
ZnO
48.0 10.2 0.72 0.53
49.0 10.3 0.87 0.57
49.7 9.6 0.92 0.65
46.2 8.6 0.97 0.64
49.2 9.6 0.87 0.48
1.1 1.1 0.06 0.05
Treatment contrast, P value Zn-Met, addition
Zn-Met, linear
Zn-Met, quadratic
3 Zn-Met vs ZnO
0.70 0.30 0.03 0.13
SNNN0.36 0.42 0.92 0.33
0.47 0.33 0.15 0.16
0.96 0.91 0.56 0.24
54% concentrate basal diet fed at 4% BW, Control no added Zn-Met, ZnO or CuO, 1 Zn-Met 1 g Zn-Met (40 mg Zn, 100 mg Met) 14 mg CuO, 3 Zn-Met 3 g Zn-Met (120 mg Zn, 300 mg Met) 45 mg CuO, 5 Zn-Met 5 g Zn-Met (200 mg Zn, 500 mg Met) 75 mg CuO, ZnO 150 mg ZnO (120 mg Zn) 45 mg CuO.
R. Puchala et al. / Small Ruminant Research 33 (1999) 1±8
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Fig. 1. Body weight of Angora goats fed 54% concentrate diet supplemented with: (*) 1 g Zn-Met (40 mg Zn, 100 mg Met) 14 mg CuO, (*) 3 g Zn-Met (120 mg Zn, 300 mg Met) 45 mg CuO, (r) 5 g Zn-Met (200 mg Zn, 500 mg Met) 75 mg CuO, (~) 150 mg ZnO (120 mg Zn) 45 mg CuO, (&) no added Zn-Met, ZnO or CuO.
days of the experiment (Fig. 1). However, ADG for the subsequent 40 days was relatively low and resulted in lower overall ADG for the ZnO versus 3 g/day ZnMet treatment. This suggests different metabolism of ZnO and Zn-Met in the body. It is possible that ZnO elicited a nutrient imbalance that impacted ADG only during the last 40 days of the experiment. In this regard, Spears (1989) reported that in lambs fed a semi-puri®ed diet, urinary excretion of Zn tended to be lower and plasma Zn decreased to pre-dosing baseline values at a slower rate for lambs fed a Zn-Metsupplemented diet compared with a diet supplemented with ZnO. There were no differences in feed intake as a result of supplementation either with Zn-Met or ZnO. In contrast, Hat®eld et al. (1992, 1995) noticed a tendency for feedlot wethers and pregnant ewes given diets high in Zn-Met to consume more feed than animals given a control diet. Feed intake in the present experiment was set at 4% BW, and this allowed most animals to leave a small amount of feed each day. This feeding regime should have unlimited opportunities for full expression of dietary treatment effects on feed intake, however, there was no effect of treatments on feed intake.
4.2. Met Zn-Met addition to the diet only numerically increased greasy and clean mohair production, and mohair production decreased and then increased as dietary level of Zn-Met was raised. It was expected that Zn-Met supplementation would signi®cantly increase mohair production and(or) ADG due to increased methionine absorption. Heinrichs and Conrad (1983) reported that Zn-Met is resistant to ruminal degradation and Hempe and Cousins (1989) reported that Zn-Met can be transported intact from the intestinal lumen into mucosal cells. Therefore, animals in the present experiment supplemented with Zn-Met would have had 14, 30 and 45% more Met available for utilization compared with control animals, assuming complete ruminal escape and intestinal mucosal cell entry. In a recent study using skin perfusion in Angora goats, Puchala et al. (1995) demonstrated that a 17% increase in the supply of Met to the skin increased mohair growth. Also, Sahlu and Fernandez (1992) increased ®ber production by infusing Met interperitoneally. Supplementation with Zn-Met did not increase plasma Met concentration, despite presumed large
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R. Puchala et al. / Small Ruminant Research 33 (1999) 1±8
increases in Met absorption with Zn-Met supplementation. The lack of increase in plasma Met implies that potential for tissue utilization of Met was not exceeded, assuming high or complete ruminal escape and intestinal absorption of Met supplied by Zn-Met. Based on observations of Puchala et al. (1995); Sahlu and Fernandez (1992), it can be concluded that dietary Zn-Met inclusion was not as effective as Met provided by skin perfusion or interperitoneal infusion in increasing mohair production. 4.3. Zn Effects of dietary Zn supplementation, regardless of form, depend on the animal's nutrient status, particularly of minerals and protein. For example, increasing the dietary Zn concentration from 4.8 to 26.5 mg/kg increased daily wool growth from 0.74 to 1.3 mg/cm3 when the dietary CP concentration was increased from 6.3 to 18.8% but not with the dietary CP level held constant at 12.2% (Masters, 1984). Thus, the ®xed dietary CP concentration in the present experiment may have limited the opportunity for effects of increasing dietary Zn on ®ber growth. The NRC (1981) states that the marginal dietary level of Zn for goats is 20±33 mg/kg, as compared with 22 mg/kg of Zn in the control diet of the present experiment. However, reports such as of Masters (1984); White et al. (1994) suggest a lower Zn requirement than given by NRC (1981). For example, White et al. (1994) noted similar feed intake and growth rate among Merino sheep consuming diets containing 10, 17 or 27 mg/kg Zn, although, wool growth rate was the lowest for the 10 mg/kg Zn diet. Overall, it appears that Zn concentration in the control diet of present experiment was at least marginal or adequate, which could have minimized potential for responses in ADG or mohair growth due to change in Zn status. In accordance, supplementation with Zn increased its concentration in plasma regardless of form of added Zn (1, 3, 5 g/day Zn-Met or ZnO). Likewise, Grace and Lee (1992) found that high Zn intake had no effect on ¯eece weight, ®ber strength or ®ber diameter. Moreover, White et al. (1994) suggested that a plasma Zn concentration of 0.5 mg/l supports normal wool growth in Merino sheep, whereas the mean plasma concentration of Zn in control animals of the present experiment was above value recommended by cited
authors. In available literature there is no information concerning in¯uence of Zn on either mohair or cashmere growth; therefore, it was assumed that data concerning wool growth can be used for comparison and reference. By analyzing both ADG and mohair growth data it can be suggested that supplementation of 1 g Zn-Met may offer little potential to improve animal production. In this experiment bene®cial effects of Zn-Met was probably due to form of Zn provided rather than changes in Met metabolism. It was observed by Sahlu and Fernandez (1992); Puchala et al. (1995); Pierzynowski et al. (1997) that Met signi®cantly increased mohair production when Angora goats were fed diets similar to those used in the present experiment. In this experiment there was no linear response in ADG or mohair production due to Met provided in the form of Zn-Met and the response of mohair growth to Zn-Met was relatively low compared to that observed with Met supplementation (Sahlu and Fernandez, 1992; Puchala et al., 1995). 4.4. Cu and Zn Purser (1979) presented evidence that both Cu and Zn are required directly in the process of ®ber growth, and de®ciencies of these minerals can have dramatic effects on wool growth. Rojas et al. (1995) reported that supplementation of a sheep diet with different Zn sources (Zn-Met, Zn-Lys, ZnS04 and ZnO) decreased serum Cu concentration; therefore, it was decided to include a small amount of CuO in supplements in the present experiment. In our experiment Cu concentration in the basal diet was low (5.3 ppm) compared with 70 ppm of Cu in basal diet used by Rojas et al. (1995) which exclude Cu as a possible cause of low ef®ciency of Zn-Met supplementation. Plasma Cu concentration was not affected by treatment, which indicates that added Cu did not affect goat metabolism. 5. Conclusions Dietary inclusion of supplemental Zn-Met, regardless of level, increased ADG in yearling Angora goats, but only numerically increased mohair production with a basal diet adequate in Zn. ADG was greater for goats supplemented with the same quantity of Zn
R. Puchala et al. / Small Ruminant Research 33 (1999) 1±8
in the form of Zn-Met versus ZnO, even though plasma Zn concentration was similar. In conclusion, with a 11.2% CP, Zn-adequate diet, 1 g Zn-Met may offer little potential to improve ®ber production by Angora goats. Acknowledgements This research was supported by CSREES Project No. OKLX 2000-01. Authors wish to thank the farm crew at the E (Kika) de la Garza Institute for Goat Research for animal care and the Central Laboratory Unit for help in laboratory analyses. References Aguilar, A.A., Jordan, C.D., 1990. Effects of zinc methionine supplementation in high producing Holstein cows early in lactation. Proc. 29th Annual Meeting National Mastitis Council, p. 187. American Society for Testing and Materials, 1988. Annual Book of ASTM Standards. Standard Test Method D2130. Wool Content of raw wool laboratory scale, Philadelphia, PA. Benevenga, N.J., Radcliffe, B.C., Egan, A.R., 1983. Tissue metabolism of methionine in sheep. Aust. J. Biol. Sci. 36, 475±485. Black, J.L., Reis, P.J., 1979. Speculation on the control of nutrient partition between wool growth and other body functions. In: Black, J.L., Reis, P.J. (Eds.), Physiological and Environmental Limitations to Wool Growth et al. Environmental Limitations to Wool Growth, University of New England, Armidale, pp. 269± 293. Chaney, A.L., Marbach, E.P., 1962. Modified reagents for determination of urea and ammonia. Clin. Chem. 8, 130±136. Cobon, D.H., Suter, G.R., Connelly, P.T., Shepherd, R.K., Hopkins, P.S., 1988. The residual effects of methionine supplementation on the wool growth performance in grazing sheep. Proc. Aust. Soc. Anim. Prod. 17, 383±389. Grace, N.D., Lee, J., 1992. Influence of high zinc intakes, season, and staple site on the elemental composition of wool and fleece quality in grazing sheep. N. Z. J. Agric. Res. 35, 367±373. Greene, L.W., Lunt, D.K., Byers, F.M., Chirase, N.K., Richmond, C.E., Knutson, R.E., Schelling, G.T., 1988. Performance and carcass quality of steers supplemented with zinc oxide or zinc methionine. J. Anim. Sci. 66, 1818±1823. Hatfield, P.G., Snowder, G.D., Glimp, H.A., 1992. The effects of chelated zinc methionine on feedlot lamb performance, cost of gain and carcass characteristics. Sheep. Res. J. 8, 1±9. Hatfield, P.G., Snowder, G.D., Head Jr, W.A., Glimp, H.A., Stobart, R.H., Besser, T., 1995. Production by ewes rearing single or twin lambs: effects of dietary crude protein percentage and supplemental zinc methionine. J. Anim. Sci. 73, 1227±1238.
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Hempe, J.M., Cousins, R.J., 1989. Effect of EDTA and zincmethionine complex on zinc absorption by rat intestine. J. Nutr. 119(8), 1179±1187. Heinrichs, A.J., Conrad, H.R., 1983. Rumen solubility and breakdown of metal proteinate compounds. J. Dairy Sci. 66 (Suppl. 1) 147. Kellogg, D.W., Rakes, J.M., Gliedt, D.W., 1989. Effect of zinc methionine supplementation on performance and selected blood parameters of lactating dairy cows. Nutr. Rep. Int. 40, 1049±1055. Martin, J.J., Strasia, C.A., Gill, D.R., Hicks, R.A., Ridenour, K., Dolezal, D., Owens, F.N., 1987. Effect of zinc methionine on live performance and carcass merit of feedlot steers. J. Anim. Sci. 65 (Suppl. 1) 500. Masters, D.G., 1984. Zinc in wool and the assessment of zinc nutrition in sheep. Proc. Nutr. Soc. Aust. 9, 184±187. NRC, 1981. Nutrient Requirements of Goats. Natl. Acad. Sci., Washington, DC, pp. 2±12. Pierzynowski, S.G., Puchala, R., Sahlu, T., 1997. Effects of dipeptide administered to a perfused area of the skin in Angora goats. J. Anim. Sci. 75, 3052±3056. Puchala, R., Pierzynowski, S.G., Sahlu, T., 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. Purser, D.B., 1979. Effects of minerals upon wool growth. In: Black, J.L., Reis, P.J. (Eds.), Physiological and Environmental Limitations to Wool Growth, University of New England, Armidale, pp. 243±255. Radclife, B.C., Egan, A.R., 1978. The effect of diet and of methionine loading on activity of enzymes in the transulfuration pathway in sheep. Aust. J. Biol. Sci. 31, 105±114. Reis, P.J., 1989. The influence of absorbed nutrients on wool growth. In: Rogers, G.E., Reis, P.J., Ward, K.A., Marshall, R.C. (Eds.), The Biology of Wool and Hair, Chapman and Hall, London, pp. 185±203. Reis, P.J., Sahlu, T., 1994. The nutritional control of the growth and properties of mohair and wool fibres: a comparative review. J. Anim. Sci. 72, 1899±1906. Reis, P.J., Tunks, D.A., 1978. Effect on wool growth of the infusion of mixtures of amino acids into the abomasum of sheep. J. Agric. Sci. 90, 173±182. Reis, P.J., Tunks, D.A., Munro, S.G., 1990. Effects of the infusion of amino acids into the abomasum of sheep, with emphasis on the relative value of methionine, cystine and homocysteine for wool growth. J. Agric. Sci. 114, 59±67. Rojas, L.X., McDowell, L.R., Cousins, R.J., Martin, F.G., Wilkinson, N.S., Johnson, A.B., Velasquez, J.B., 1995. Relative bioavailability of two organic and two inorganic zinc sources fed to sheep. J. Anim. Sci. 73, 1202±1207. 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±3194. SAS, 1990. SAS User's Guide, Release 6.03 ed. SAS Institute, Cary, NC, pp. 210±264. Seeley, R.C., Kinsey, W.J., 1982. The determination of trace elements in whole blood by DC plasma emission spectroscopy. Spectra Metrics/Beckman Instruments, Haverhill, MA, pp. 2±15.
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performance, carcass characteristics and serum profiles of lambs. J. Anim. Sci. 65 (Suppl. 1) 500. White, C.L., Martin, G.B., Hynd, P.I., Chapman, R.E., 1994. The effect of zinc deficiency on wool growth and skin and wool follicle histology of male Merino lambs. Br. J. Nutr. 71, 425± 435.
Effects of zinc-methionine on performance of Angora goats R. Puchalaa, T. Sahlua,*, J.J. Davis1,a a
E (Kika) de la Garza Institute for Goat Research, P. O. Box 730, Langston, OK 73050, USA Accepted 25 November 1998
Abstract Effects of supplementation with zinc-methionine (Zn-Met), a source of potentially rumen protected methionine and zinc (Zinpro 40, Edina, MN), on mohair growth, BW gain and blood metabolites were investigated in Angora goats. Forty yearling Angora goats (20 wethers and 20 doelings) were offered a basal diet (11.2% CP, 22 ppm Zn, 2.3 Mcal/kg DM) at 4% BWof DM for 120 days. The treatments (1±5) were: 1, 3 and 5 g/day of Zn-Met, 150 mg/day of zinc oxide and control (no supplementation). Supplementation of the diet with Zn-Met (1, 3 and 5 g/day of Zn-Met) increased (P < 0.07) ADG (65.5 versus 55.9 g/day for control). ADG for goats receiving ZnO was lower (P < 0.04) than for goats receiving a similar amount of Zn from 3 g/d Zn-Met (50.5 versus 62.9 g/day), although Zn-Met inclusion in the diet numerically (P 0.13) increased clean mohair production, which also changed quadratically (P < 0.09) as Zn-Met level increased (1.59, 1.51, 1.62, 1.60 and 1.59 kg in 120 days) for treatments 1, 2, 3, 4 and 5, respectively. Supplementation of the diet with Zn-Met increased (P < 0.03) plasma Zn concentration (0.92 versus 0.72 mg/l for control); there were no differences in plasma Zn concentration between goats receiving the ZnO supplement and goats receiving a similar amount of Zn from Zn-Met (0.87 versus 0.92 mg/l; P > 0.56). Plasma methionine concentration was not affected by Zn-Met supplementation (P > 0.53). In summary, supplementation of a Zn-adequate diet with Zn-Met increased ADG by yearling Angora goats regardless of level of Zn-Met added. Supplementation of 1 g Zn-Met may have positive effect on ADG and mohair growth when diet contains about 20 ppm Zn. # 1999 Elsevier Science B.V. All rights reserved. Keywords: Angora goats; Zinc-methionine; Mohair
1. Introduction The essential amino acids lysine, methionine (Met) and cyst(e)ine stimulate wool and mohair growth (Sahlu and Fernandez, 1992; Reis and Sahlu, 1994; Puchala et al., 1995). Reis and Tunks (1978); Reis et al. (1990), using dietary mixtures of amino acids, found that omission of Met reduced wool growth *Corresponding author. Tel.: +1-405-466-3836; fax: +1-405466-3138; e-mail: [email protected] 1 Institute for Integrated Agricultural Development (IIAD) RMB 1145, Rutherglen, Victoria 3685, Australia.
and decreased both length growth rate and diameter. Skin and ®ber (wool, mohair) impose heavy demands on the utilization of circulating sulfur amino acids. Black and Reis (1979) predicted that 80% of the total free blood pool of combined cysteine and Met would be used for ®ber growth. Being responsible for the initiation of protein synthesis, Met is important in ®ber growth. Met can be converted by transulfuration to cystine mainly in the liver (Cobon et al., 1988), but also to some extent in other tissues (Radclife and Egan, 1978; Benevenga et al., 1983). Supplementation with speci®c amino acids has in¯uenced mohair growth in Angora goats. Sahlu
0921-4488/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 4 8 8 ( 9 8 ) 0 0 1 9 4 - 1
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and Fernandez (1992) evaluated responses to intraperitoneal administration of amino acids in Angora wethers fed a 13% CP diet. Infusion of 1 g/day of Met increased clean mohair yield from 7.6 to 8.0 g/ 100 cm2 of skin. Assuming that the average percentage of methionine in protein is 2%, 1 g of Met substitutes for 50 g of protein. Considering the feed intake of animals used by Sahlu and Fernandez (1992), infused Met of 1 g/day was equivalent to increasing the dietary protein level from 13 to 18%. It may be cost effective to increase absorption of most limiting amino acids such as Met through dietary supplementation of speci®c amino acids, rather than increasing absorption of a large number of amino acids through increase of the total dietary CP level. Apart from the major nutrients such as protein, many vitamins and trace elements are essential for ®ber growth. Zinc (Zn) functions directly in the process of wool growth; thus, Zn de®ciencies can seriously affect wool growth (Reis, 1989). Zinc is needed for the functions of over 100 enzymes, and essential for DNA, RNA, protein synthesis and, as such, cell division. White et al. (1994) suggested that primary impact of Zn de®ciency on wool growth is through impaired protein synthesis. Commercially available Zn-Met complexes provide both Zn and Met. Heinrichs and Conrad (1983) reported that Met from a Zn-Met complex was not utilized by mixed ruminal inoculum in vitro, implying passage to the small intestine without microbial alteration. Hempe and Cousins (1989) suggested that ZnMet and Cu-Lys complexes are transported intact from the intestinal lumen into mucosal cells. If Zn-Met is absorbed and transported without modi®cation, the complex may provide a means of increasing tissue supply of Met, which should increase animal productivity when Met is limiting. Therefore, objectives of this study were to investigate effects of dietary supplementation with Zn-Met (Zinpro 40, Edina, MN) or zinc oxide on mohair growth, BW gain and concentrations of blood metabolites in Angora goats. 2. Materials and methods Forty yearling Angora goats (BW 24.5 2.0 kg, twenty wethers and twenty doelings) were adapted to a basal diet (Table 1) fed at 4% BW (DM basis). The
Table 1 Composition of experimental diet Item
Concentration (%)
Ingredient Cottonseed hulls Ground corn Soybean meal Trace mineral salta Calcium carbonate Vitamin premixb Dicalcium phosphate
46.0 45.0 7.0 1.0 0.5 0.2 0.3
Nutrients CP TDN
11.2 64.2
a
Containing (in percentages) NaCl, 94 to 95; Mn, >0.2; ferrous Fe, >0.16; ferric Fe, >0.14; Cu, >0.033; Zn, >0.10; I, >0.007; Co, >0.005. b Each gram contained 2200 IU of vitamin A, 2200 IU of vitamin D, and 0.2 IU of vitamin E.
diet was formulated to be adequate in CP, energy, vitamins and minerals for these classes of goats. Following the adaptation period goats were blocked by BW and sex and randomly assigned to one of ®ve dietary supplements: 1 g Zn-Met (40 mg Zn, 100 mg Met) 14 mg CuO (12 mg Cu); 3 g Zn-Met (120 mg Zn, 300 mg Met) 45 mg CuO (36 mg Cu); 5 g ZnMet (200 mg Zn, 500 mg Met) 75 mg CuO (60 mg Cu); 150 mg ZnO (120 mg Zn) 45 mg CuO (36 mg Cu); control (no supplement). Cu is considered to be a major Zn antagonist and, hence, was provided together with Zn supplementation to avoid Cu de®ciency (Rojas et al., 1995). The basal diet contained 22 ppm of Zn and 5.3 ppm of Cu. Supplementation of 150 mg ZnO and 3 g of Zn-Met provided a similar amount of supplemental Zn (120 mg/day). Goats were housed in individual crates with expanded metal ¯oors. Animals were fed once daily at 08:00 hours and had free access to water; treatments were applied for 120 days. Intake was calculated at 4% BW and adjusted weekly after weighing. All goats were shorn at the beginning and end of the experiment. A mid-side sample was collected from each ¯eece for staple length and mohair diameter analyses. On days 30, 60, 90 and 120 blood was obtained via jugular venipuncture at 2 h postprandial. Blood was collected into four 7 ml tubes containing potassium oxalate± sodium ¯uoride, K3 EDTA or sodium heparin (Becton
R. Puchala et al. / Small Ruminant Research 33 (1999) 1±8
Dickinson, Vacutainer systems Rutherford, NJ). The tubes were immediately chilled in an ice bath, transported to the laboratory and centrifuged at 1500 g at 48C for 20 min. Plasma aliquots were stored at ÿ558C until analyses. Ruminal ¯uid samples were obtained using a stomach tube immediately after blood sampling. In the last week of the experiment, feces and urine were collected daily for 5 days from each wether. Each fecal and urine sample was mixed and a 10% subsample from each collection was bulked over the 5day period. The total amounts of feed offered and refused by the animals were recorded and subsamples bulked for subsequent analyses. Samples of feed ingredients, feed refusals and feces were dried in a forced-air oven (608C), ground to pass a 2 mm screen and analyzed for DM, total N, gross energy and ADF. Samples of urine were freeze-dried prior N to analysis. Plasma for amino acid estimation (0.45 ml) was deproteinized using 0.05 ml of 50% (w/v) 5-sulfosalicylic acid with added internal standards (sarcosine and norvaline). The mixture was vortexed, centrifuged (1500 g; 48C; 10 min) and placed in sample vials. Degreased mohair samples (20 mg) were prepared for amino acid analysis by adding dithiodipropionic acid solution (to convert cystine to S-(2-carboxyethyltio)L-Cysteine), norvaline and sarcosine (internal standards) and digested in 6N HCl using a microwave digestion system (MDS 2000; CEM Corp., Matthews, NC). Amino acid analyses were performed on an AminoQuant system (Hewlett Pacard, San Fernando, CA) using precolumn derivatization with o-phthalaldehyde and 9-¯uorenylmethylchloroformate and UV detection. Plasma Zn, Mg, Fe and Cu concentrations were determined using plasma emission spectroscopy (Applied Research Laboratories, Inc., Dearborn, MI), according to the method of Seeley and Kinsey (1982). Plasma glucose concentrations were analyzed colorimetrically using a Sigma glucose diagnostic kit (Catalog No. 315; Sigma Diagnostic, St. Louis, MO). A kit using an enzymatic method was used to quantify NEFA (Catalog No 990-75401; Wako Pure Chemical Industries, Osaka, Japan). Sigma kits (Sigma Diagnostic, St. Louis, MO) were used to determine plasma creatinine and total protein concentrations. Plasma urea N was determined as described by Chaney and Marbach (1962). VFA were analyzed by adding 1 ml of 25% (w/v) metaphosphoric acid to 5 ml of ruminal
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¯uid. The solution was allowed to stand for 30 min and then centrifuged for 20 min at 10 000 g. Aliquots of the supernatant were subjected to gas chromatography (Hewlett Packard Co., Avondale, PA) utilizing a 1.98 4 mm i.d. glass column packed with 15% SP-1200 plus 1% H3PO4 on 100/120 Chromosorb W AW (Supelco, Bellefonte, PA). Staple length and greasy and clean mohair yields were determined according to ASTM Standards (American Society for Testing and Materials, 1988). Fiber diameter was determined using the Peyer FDA 200 System (Wallerau, Switzerland). The general linear models procedure of SAS (1990) was used to analyze data. Data were analyzed as a completely randomized design with the treatment, sex and their interaction in the model for feed intake, performance and mohair growth and characteristics. There were no effects of sex or the sex treatment interaction (P > 0.05). Blood measurements were ®rst analyzed as a split-plot in time, although time effects and time treatment interactions were nonsigni®cant (P > 0.05). Contrasts were conducted for dietary adition of Zn-Met, linear and quadratic effects of nonzero dietary Zn-Met level and for Zn-Met versus 3 g ZnMet (Steel and Torrie, 1980). 3. Results Initial BW and feed intake were similar among treatments (P > 0.1; Table 2). Supplementation of the diet with Zn-Met (1, 3 and 5 g/day Zn-Met) increased (P < 0.07) ADG (65.5 versus 55.9 g/day for control). ADG for goats receiving the ZnO (120 mg/day Zn) supplement was lower (P < 0.04) than for goats receiving a similar amount of Zn from Zn-Met (50.5 versus 62.9 g/day). Zn-Met treatments had quadratic effects (P < 0.09) on greasy and clean mohair production (Table 2). Mohair diameter was similar among groups (P > 0.1); however, staple length was lower for ZnO than for 3 g/day Zn-Met (9.5 versus 10.5 cm; P < 0.03). Plasma glucose and urea concentrations were not affected (P > 0.1) by dietary treatment Table 3). Supplementation of the diet with Zn-Met treatments (1, 3 and 5 g/day ZnMet) increased (P < 0.03) plasma Zn concentration (0.92 versus 0.72 mg/l for control), however no difference in plasma Zn concentration was seen between
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Table 2 Initial weight, feed intake, ADG and mohair production and quality for Angora goats supplemented with Zn-Met complex or ZnO for 120 days Item
Initial weight (kg) Feed intake (kg/day) ADG (g/day) Greasy mohair (kg) Clean mohair (kg) Diameter (mm) Length (cm)
Treatmenta
SEM
Control
1 Zn-Met
3 Zn-Met
5 Zn-Met
ZnO
24.0 0.78 55.9 1.84 1.57 29.0 10.3
24.2 0.92 67.0 1.89 1.59 29.8 10.0
24.4 0.85 62.9 1.83 1.51 30.3 10.5
24.0 0.88 66.7 1.94 1.62 29.5 10.0
24.6 0.80 50.5 1.90 1.60 30.0 9.5
1.3 0.06 4.1 0.05 0.04 0.9 0.3
Treatment contrast, P value Zn-Met, addition
Zn-Met, linear
Zn-Met, quadratic
3 Zn-Met vs ZnO
0.87 0.52 0.07 0.13 0.13 0.46 0.66
0.86 0.97 0.22 0.90 0.80 0.73 0.47
0.86 0.59 0.49 0.09 0.09 0.28 0.14
0.96 0.69 0.04 0.43 0.21 0.48 0.03
a
54% concentrate basal diet fed at 4% BW; control no added Zn-Met, ZnO or CuO, 1 Zn-Met 1 g Zn-Met (40 mg Zn, 100 mg Met) 14 mg CuO, 3 Zn-Met 3 g Zn-Met (120 mg Zn, 300 mg Met) 45 mg CuO, 5 Zn-Met 5 g Zn-Met (200 mg Zn, 500 mg Met) 75 mg CuO, ZnO 150 mg ZnO (120 mg Zn) 45 mg CuO.
goats receiving the ZnO or goats receiving a similar amount of Zn from Zn-Met (0.87 versus 0.92 mg/l; P > 0.10).PlasmaCuconcentrationsweresimilaramong all treatments. Plasma-essential amino acid concentrations were not affected by dietary treatment (P > 0.1; values not shown). There were no diet effects on concentrations of other analyzed blood and ruminal constituents or DM and N digestibilities (P > 0.1; values not shown), and the amino acid pro®le of mohair was unaffected by treatment (P > 0.1; values not shown). 4. Discussion 4.1. Zn-Met and ZnO In the present experiment dietary supplementation of Zn-Met increased ADG. This result is supported by
similar reports of improved animal performance with Zn-Met supplementation. Spears (1989) reported that heifers fed a corn-based diet (25 ppm of Zn) supplemented with 25 mg Zn as Zn-Met had higher ADG than controls. Aguilar and Jordan (1990) and Kellogg et al. (1989) noted increased milk production by lactating dairy cows as result of dietary Zn-Met supplementation. Although, in some studies Zn-Met has not altered animal performance. Martin et al. (1987) using steers and Stobart et al. (1987) using lambs did not observe differences in ADG or feed ef®ciency between animals fed Zn-Met and those fed control diets. Similarly, Greene et al. (1988) found similar ADG and feed ef®ciencies for steers consuming diets with or without Zn-Met, but this may have involved a relatively high Zn level in the control diet (i.e., 81 ppm Zn). Our group receiving ZnO gained BW at the rate fairly similar to that for Zn-Met treatments up to 80
Table 3 Plasma metabolites concentration for Angora goats supplemented with Zn-Met complex or ZnO for 120 days Item
Glucose (mg/dl) Urea N (mg/dl) Zn (mg/l) Cu (mg/l) a
Treatmenta
SEM
Control
1 Zn-Met
3 Zn-Met
5 Zn-Met
ZnO
48.0 10.2 0.72 0.53
49.0 10.3 0.87 0.57
49.7 9.6 0.92 0.65
46.2 8.6 0.97 0.64
49.2 9.6 0.87 0.48
1.1 1.1 0.06 0.05
Treatment contrast, P value Zn-Met, addition
Zn-Met, linear
Zn-Met, quadratic
3 Zn-Met vs ZnO
0.70 0.30 0.03 0.13
SNNN0.36 0.42 0.92 0.33
0.47 0.33 0.15 0.16
0.96 0.91 0.56 0.24
54% concentrate basal diet fed at 4% BW, Control no added Zn-Met, ZnO or CuO, 1 Zn-Met 1 g Zn-Met (40 mg Zn, 100 mg Met) 14 mg CuO, 3 Zn-Met 3 g Zn-Met (120 mg Zn, 300 mg Met) 45 mg CuO, 5 Zn-Met 5 g Zn-Met (200 mg Zn, 500 mg Met) 75 mg CuO, ZnO 150 mg ZnO (120 mg Zn) 45 mg CuO.
R. Puchala et al. / Small Ruminant Research 33 (1999) 1±8
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Fig. 1. Body weight of Angora goats fed 54% concentrate diet supplemented with: (*) 1 g Zn-Met (40 mg Zn, 100 mg Met) 14 mg CuO, (*) 3 g Zn-Met (120 mg Zn, 300 mg Met) 45 mg CuO, (r) 5 g Zn-Met (200 mg Zn, 500 mg Met) 75 mg CuO, (~) 150 mg ZnO (120 mg Zn) 45 mg CuO, (&) no added Zn-Met, ZnO or CuO.
days of the experiment (Fig. 1). However, ADG for the subsequent 40 days was relatively low and resulted in lower overall ADG for the ZnO versus 3 g/day ZnMet treatment. This suggests different metabolism of ZnO and Zn-Met in the body. It is possible that ZnO elicited a nutrient imbalance that impacted ADG only during the last 40 days of the experiment. In this regard, Spears (1989) reported that in lambs fed a semi-puri®ed diet, urinary excretion of Zn tended to be lower and plasma Zn decreased to pre-dosing baseline values at a slower rate for lambs fed a Zn-Metsupplemented diet compared with a diet supplemented with ZnO. There were no differences in feed intake as a result of supplementation either with Zn-Met or ZnO. In contrast, Hat®eld et al. (1992, 1995) noticed a tendency for feedlot wethers and pregnant ewes given diets high in Zn-Met to consume more feed than animals given a control diet. Feed intake in the present experiment was set at 4% BW, and this allowed most animals to leave a small amount of feed each day. This feeding regime should have unlimited opportunities for full expression of dietary treatment effects on feed intake, however, there was no effect of treatments on feed intake.
4.2. Met Zn-Met addition to the diet only numerically increased greasy and clean mohair production, and mohair production decreased and then increased as dietary level of Zn-Met was raised. It was expected that Zn-Met supplementation would signi®cantly increase mohair production and(or) ADG due to increased methionine absorption. Heinrichs and Conrad (1983) reported that Zn-Met is resistant to ruminal degradation and Hempe and Cousins (1989) reported that Zn-Met can be transported intact from the intestinal lumen into mucosal cells. Therefore, animals in the present experiment supplemented with Zn-Met would have had 14, 30 and 45% more Met available for utilization compared with control animals, assuming complete ruminal escape and intestinal mucosal cell entry. In a recent study using skin perfusion in Angora goats, Puchala et al. (1995) demonstrated that a 17% increase in the supply of Met to the skin increased mohair growth. Also, Sahlu and Fernandez (1992) increased ®ber production by infusing Met interperitoneally. Supplementation with Zn-Met did not increase plasma Met concentration, despite presumed large
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increases in Met absorption with Zn-Met supplementation. The lack of increase in plasma Met implies that potential for tissue utilization of Met was not exceeded, assuming high or complete ruminal escape and intestinal absorption of Met supplied by Zn-Met. Based on observations of Puchala et al. (1995); Sahlu and Fernandez (1992), it can be concluded that dietary Zn-Met inclusion was not as effective as Met provided by skin perfusion or interperitoneal infusion in increasing mohair production. 4.3. Zn Effects of dietary Zn supplementation, regardless of form, depend on the animal's nutrient status, particularly of minerals and protein. For example, increasing the dietary Zn concentration from 4.8 to 26.5 mg/kg increased daily wool growth from 0.74 to 1.3 mg/cm3 when the dietary CP concentration was increased from 6.3 to 18.8% but not with the dietary CP level held constant at 12.2% (Masters, 1984). Thus, the ®xed dietary CP concentration in the present experiment may have limited the opportunity for effects of increasing dietary Zn on ®ber growth. The NRC (1981) states that the marginal dietary level of Zn for goats is 20±33 mg/kg, as compared with 22 mg/kg of Zn in the control diet of the present experiment. However, reports such as of Masters (1984); White et al. (1994) suggest a lower Zn requirement than given by NRC (1981). For example, White et al. (1994) noted similar feed intake and growth rate among Merino sheep consuming diets containing 10, 17 or 27 mg/kg Zn, although, wool growth rate was the lowest for the 10 mg/kg Zn diet. Overall, it appears that Zn concentration in the control diet of present experiment was at least marginal or adequate, which could have minimized potential for responses in ADG or mohair growth due to change in Zn status. In accordance, supplementation with Zn increased its concentration in plasma regardless of form of added Zn (1, 3, 5 g/day Zn-Met or ZnO). Likewise, Grace and Lee (1992) found that high Zn intake had no effect on ¯eece weight, ®ber strength or ®ber diameter. Moreover, White et al. (1994) suggested that a plasma Zn concentration of 0.5 mg/l supports normal wool growth in Merino sheep, whereas the mean plasma concentration of Zn in control animals of the present experiment was above value recommended by cited
authors. In available literature there is no information concerning in¯uence of Zn on either mohair or cashmere growth; therefore, it was assumed that data concerning wool growth can be used for comparison and reference. By analyzing both ADG and mohair growth data it can be suggested that supplementation of 1 g Zn-Met may offer little potential to improve animal production. In this experiment bene®cial effects of Zn-Met was probably due to form of Zn provided rather than changes in Met metabolism. It was observed by Sahlu and Fernandez (1992); Puchala et al. (1995); Pierzynowski et al. (1997) that Met signi®cantly increased mohair production when Angora goats were fed diets similar to those used in the present experiment. In this experiment there was no linear response in ADG or mohair production due to Met provided in the form of Zn-Met and the response of mohair growth to Zn-Met was relatively low compared to that observed with Met supplementation (Sahlu and Fernandez, 1992; Puchala et al., 1995). 4.4. Cu and Zn Purser (1979) presented evidence that both Cu and Zn are required directly in the process of ®ber growth, and de®ciencies of these minerals can have dramatic effects on wool growth. Rojas et al. (1995) reported that supplementation of a sheep diet with different Zn sources (Zn-Met, Zn-Lys, ZnS04 and ZnO) decreased serum Cu concentration; therefore, it was decided to include a small amount of CuO in supplements in the present experiment. In our experiment Cu concentration in the basal diet was low (5.3 ppm) compared with 70 ppm of Cu in basal diet used by Rojas et al. (1995) which exclude Cu as a possible cause of low ef®ciency of Zn-Met supplementation. Plasma Cu concentration was not affected by treatment, which indicates that added Cu did not affect goat metabolism. 5. Conclusions Dietary inclusion of supplemental Zn-Met, regardless of level, increased ADG in yearling Angora goats, but only numerically increased mohair production with a basal diet adequate in Zn. ADG was greater for goats supplemented with the same quantity of Zn
R. Puchala et al. / Small Ruminant Research 33 (1999) 1±8
in the form of Zn-Met versus ZnO, even though plasma Zn concentration was similar. In conclusion, with a 11.2% CP, Zn-adequate diet, 1 g Zn-Met may offer little potential to improve ®ber production by Angora goats. Acknowledgements This research was supported by CSREES Project No. OKLX 2000-01. Authors wish to thank the farm crew at the E (Kika) de la Garza Institute for Goat Research for animal care and the Central Laboratory Unit for help in laboratory analyses. References Aguilar, A.A., Jordan, C.D., 1990. Effects of zinc methionine supplementation in high producing Holstein cows early in lactation. Proc. 29th Annual Meeting National Mastitis Council, p. 187. American Society for Testing and Materials, 1988. Annual Book of ASTM Standards. Standard Test Method D2130. Wool Content of raw wool laboratory scale, Philadelphia, PA. Benevenga, N.J., Radcliffe, B.C., Egan, A.R., 1983. Tissue metabolism of methionine in sheep. Aust. J. Biol. Sci. 36, 475±485. Black, J.L., Reis, P.J., 1979. Speculation on the control of nutrient partition between wool growth and other body functions. In: Black, J.L., Reis, P.J. (Eds.), Physiological and Environmental Limitations to Wool Growth et al. Environmental Limitations to Wool Growth, University of New England, Armidale, pp. 269± 293. Chaney, A.L., Marbach, E.P., 1962. Modified reagents for determination of urea and ammonia. Clin. Chem. 8, 130±136. Cobon, D.H., Suter, G.R., Connelly, P.T., Shepherd, R.K., Hopkins, P.S., 1988. The residual effects of methionine supplementation on the wool growth performance in grazing sheep. Proc. Aust. Soc. Anim. Prod. 17, 383±389. Grace, N.D., Lee, J., 1992. Influence of high zinc intakes, season, and staple site on the elemental composition of wool and fleece quality in grazing sheep. N. Z. J. Agric. Res. 35, 367±373. Greene, L.W., Lunt, D.K., Byers, F.M., Chirase, N.K., Richmond, C.E., Knutson, R.E., Schelling, G.T., 1988. Performance and carcass quality of steers supplemented with zinc oxide or zinc methionine. J. Anim. Sci. 66, 1818±1823. Hatfield, P.G., Snowder, G.D., Glimp, H.A., 1992. The effects of chelated zinc methionine on feedlot lamb performance, cost of gain and carcass characteristics. Sheep. Res. J. 8, 1±9. Hatfield, P.G., Snowder, G.D., Head Jr, W.A., Glimp, H.A., Stobart, R.H., Besser, T., 1995. Production by ewes rearing single or twin lambs: effects of dietary crude protein percentage and supplemental zinc methionine. J. Anim. Sci. 73, 1227±1238.
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Hempe, J.M., Cousins, R.J., 1989. Effect of EDTA and zincmethionine complex on zinc absorption by rat intestine. J. Nutr. 119(8), 1179±1187. Heinrichs, A.J., Conrad, H.R., 1983. Rumen solubility and breakdown of metal proteinate compounds. J. Dairy Sci. 66 (Suppl. 1) 147. Kellogg, D.W., Rakes, J.M., Gliedt, D.W., 1989. Effect of zinc methionine supplementation on performance and selected blood parameters of lactating dairy cows. Nutr. Rep. Int. 40, 1049±1055. Martin, J.J., Strasia, C.A., Gill, D.R., Hicks, R.A., Ridenour, K., Dolezal, D., Owens, F.N., 1987. Effect of zinc methionine on live performance and carcass merit of feedlot steers. J. Anim. Sci. 65 (Suppl. 1) 500. Masters, D.G., 1984. Zinc in wool and the assessment of zinc nutrition in sheep. Proc. Nutr. Soc. Aust. 9, 184±187. NRC, 1981. Nutrient Requirements of Goats. Natl. Acad. Sci., Washington, DC, pp. 2±12. Pierzynowski, S.G., Puchala, R., Sahlu, T., 1997. Effects of dipeptide administered to a perfused area of the skin in Angora goats. J. Anim. Sci. 75, 3052±3056. Puchala, R., Pierzynowski, S.G., Sahlu, T., 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. Purser, D.B., 1979. Effects of minerals upon wool growth. In: Black, J.L., Reis, P.J. (Eds.), Physiological and Environmental Limitations to Wool Growth, University of New England, Armidale, pp. 243±255. Radclife, B.C., Egan, A.R., 1978. The effect of diet and of methionine loading on activity of enzymes in the transulfuration pathway in sheep. Aust. J. Biol. Sci. 31, 105±114. Reis, P.J., 1989. The influence of absorbed nutrients on wool growth. In: Rogers, G.E., Reis, P.J., Ward, K.A., Marshall, R.C. (Eds.), The Biology of Wool and Hair, Chapman and Hall, London, pp. 185±203. Reis, P.J., Sahlu, T., 1994. The nutritional control of the growth and properties of mohair and wool fibres: a comparative review. J. Anim. Sci. 72, 1899±1906. Reis, P.J., Tunks, D.A., 1978. Effect on wool growth of the infusion of mixtures of amino acids into the abomasum of sheep. J. Agric. Sci. 90, 173±182. Reis, P.J., Tunks, D.A., Munro, S.G., 1990. Effects of the infusion of amino acids into the abomasum of sheep, with emphasis on the relative value of methionine, cystine and homocysteine for wool growth. J. Agric. Sci. 114, 59±67. Rojas, L.X., McDowell, L.R., Cousins, R.J., Martin, F.G., Wilkinson, N.S., Johnson, A.B., Velasquez, J.B., 1995. Relative bioavailability of two organic and two inorganic zinc sources fed to sheep. J. Anim. Sci. 73, 1202±1207. 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±3194. SAS, 1990. SAS User's Guide, Release 6.03 ed. SAS Institute, Cary, NC, pp. 210±264. Seeley, R.C., Kinsey, W.J., 1982. The determination of trace elements in whole blood by DC plasma emission spectroscopy. Spectra Metrics/Beckman Instruments, Haverhill, MA, pp. 2±15.
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performance, carcass characteristics and serum profiles of lambs. J. Anim. Sci. 65 (Suppl. 1) 500. White, C.L., Martin, G.B., Hynd, P.I., Chapman, R.E., 1994. The effect of zinc deficiency on wool growth and skin and wool follicle histology of male Merino lambs. Br. J. Nutr. 71, 425± 435.