الفهرس 
Effect of sulfur supplementation on animal performanceOnly 14 pages are availabe for public view
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Abstract
Sulfur (S) is known to be an essential element for ruminants for more than 60 years. Sulfide, the reduce form of sulfur, is needed for the synthesis of the amino acids cysteine and methionine (Block et al., 1951; Thomas et al., 1951), a diet deficient in sulfur results in decreased microbial protein synthesis. Since that time the role of S in ruminant nutrition has been intensively studied. Sulfur in the form of sulfate controls the cation-anion balance and blood pH, it is important in dairy cattle (high producers). Sulfur also increases the efficiency of N utilization and decreases the N loss and reduces the environmental pollution. Sulfur was usually used in different forms i.e., organic (S-amino acids), inorganic or high-S forage. Numerous papers have been published on the effect of S-supplementation on nutrient utilization, digestibility, nutritive value, N and S balances (Chichaeva, 1980; Ben-Ghedalia and Miron, 1984; Morrison et al., 1985; Walli and Mudgal, 1985; Gangwar and Sharma, 2001; Rakesh and Sharma, 2001) indicating that the almost all nutrient digestibility was significantly higher with ration supplemented with S than the control. In an in vitro study, Oshea and Baldwin (1986) obtained an improvement in digestibility from 45 to 80% when barley straw was incubated for 4 days at a sulfur dioxide concentration of 62.6g/kg DM. This improvement was attained over a DM content range 46-75% and reaction temperature range 60-70ºC. The improvement in straw in vivo digestibility measured was of the order of 11%. Ahmad et al (1995) reported that S fertilization increased apparent digestibility of DM, NDF and hemi-cellulose (P<0.05), apparent absorption and retention of S, N, P, K, Mg and Mn (P<0.01), and apparent absorption of calcium. Zinn et al (1997) showed that rumen digestion of ADF and starch was slightly lower and post-rumen digestion of ADF and starch was correspondingly greater (quadratic effect, P<0.05) with supplemental S. It is obvious that S-supplementation improved the microbial activity in the rumen of the experimental sheep. Judkins (1994) reported that added S in the form of methionine to the ration of 8 rumen-cannulated Suffolk ewes did not affect rumen pH. Zinn et al. (1997) came to the same conclusion. Al- Dobeeb (2004) used 4 mature fistulated Naeimi rams in a 4x4 and fed a control diet without or supplemented with urea or sulfur or both. The pH values of rumen liquor (before feeding) did not differ between the 4 diets used. At 2 h after feeding, a sharp DROP in pH values was observed in ureasulfur- diet. Saini et al. (2005) evaluated the effect sulfur supplemented wheat straw diet on rumen metabolic profile. They reported that ruminal pH was high with control group in comparison to treatment groups. Lundquist et al. (1985) reported high production of butyric, isobutyric and isovaleric acids in the rumen as a result of feeding methionine. Quispe et al. (1991) obtained higher acetate and iso-acids in the rumen of S-fed sheep. Chamberlain and Thomas (1983) reported that ruminal infusion of 7g methionine and 6.7g sodium sulfate had no effect on the concentration of total or individual volatile fatty acids (VFA) in the rumen fluid. Kumar and Bhatia (1984) and Judkins (1994) came to the same conclusion. As a result of the improvement in nutrient utilization due to Sulfur supplementation, it is expected that animal performance to increase. Boiko and Gorshkov (1981) found that animals fed S-supplements gained an average daily 11.6% more weight and ate 0.96 less feed units to gain a kg than those fed the basal diet alone. Erdinc (1982) supplemented lamb-ration containing 3% urea was with 0, 0.45, 0.9 or 1.8% sodium sulfate. Ratio of nitrogen to sulfur was 22.8, 11.7 or 5.7:1. Weight gain increased nonsignificantly and feed was utilized more efficiently. Many other experiments came to the same conclusion (Jones et al., 1982; Winks et al., 1982; Boiko, 1984; Kapil and Sharma, 1998; Saddick and Ahmed, 1991a). However, others found no effect of S supplementation on animal performance. Nair et al. (2004) showed that addition of sodium sulfate did not have any positive effect on the animal performance. Some blood plasma parameters have been used as indicators for the determination of dietary S status (Erdinc, 1982; Winks et al., 1982; Hill et al., 1985; Lee and Williams, 1993; Delaquis and Block, 1995; Eryavuz et al., 2003; Saini et al., 2005). Wool is a high-S-protein, therefore, many studies have been carried out to investigate the effect of dietary S-supplementation on wool production. Almost all results have indicated that control rations usually need more S supplementation in order to obtain better wool production of best quality (Boominathan et al., 1983; Modyanov et al., 1984; Radcliffe et al., 1985; Reis and Gillespie, 1985; Patkowska and Sokoa, 1990). Qi and Lupton (1994) reported that supplements of sulfur-containing amino acids increase wool production and the sulfur content of wool. However, when sheep are selected for increased wool production, the sulfur content of wool decreased. Hill (1985) studied the carcass characteristics of feed lot steers as affected by dietary S. Fifty six crossbred Brahman steers were given 2 levels of energy without or with elemental S added to the maize silage-based diet. Sulfur was given at 0.25 of the dietary DM to half of the steers on each of energy treatment. Results indicated that carcass traits were not significantly affected by dietary energy and S supplementation. Others have reported that S improved carcass traits (Zinn et al., 1997; Lee et al., 2008). The present study was carried out in order to test the effect of Ssupplementation at different levels to correct N:S ratios on performance of growing lambs, digestibility, nutritive values, N and S balances, wool production and characteristics as well as carcass traits. Rumen microbial activity was also studied.