Effect of Different Levels of Dicalcium Phosphate on Growing Male Lambs

This experiment was carried out to investigate the effects of different level of dicalcium phosphate on growth, digestibility, rumen fermentation and some blood parameters. Eighteen growing local breed male lambs (about 3 months old) with an average weight of 23.61 ±0.58 Kg were divided randomly into three feeding groups for 150 days, fed on: Ration one ( R1) : CFM contained1% dicalcium phosphate+ rice straw . Ration two ( R2 ) : CFM contained 2% dicalcium phosphate + rice straw . Ration three ( R3 ): CFM contained 3% dicalcium phosphate + rice straw . Three metabolism trails were conducted to evaluate the nutritive value of the experimental rations with sheep at 90% of ad libitum intake. Rumen liquor samples were taken using stomach tubes at 0,3 and 6 hours post feeding to determine pH values, ammonia – N (NH3-N) and total volatile fatty acids (TVFA’ s) concentration. The main results showed that the digestibility of dry matter (DM), crude protein (CP) and crude fiber (CF) for R 3 were significantly (P<0.05) higher than R 1. While ether extract (EE), organic matter (OM) and nitrogen free extract (NFE) digestibility for the rations had no significantly differences. The best value of total digestible nutrients (TDN) observed with R3 followed by R2 and the lowest value was reported for R1. The same trend was noticed with digestible J. Agric. & Env. Sci. Alex. Univ., Egypt. Vol. 2 ( 1 ) 2003 41 crude protein (DCP)% which recorded 9.72, 10.21 and 10.77% for R1, R2 and R3, respectively. The highest ruminal fermentation values obtained with R3 in comparison with other rations. Whereas, NH3-N concentration and TVFA’ s significantly (P<0.05) increased at 3 hours after feeding with R3 but ruminal pH values were unaffected. Blood total protein, albumin, asparate aminotransferase (AST), and triiodothyronine (T3) were significantly (P<0.05) higher for groups 2 and 3 which fed 2% and 3% of dicalcium phosphate (R2 and R3) compared with the group fed on 1% dicalcium phosphate (R1) . Blood serum globulin alanine amino – transferase (ALT), calcium, phosphorus and tetraiodothyronine(T4) levels were not affected by dicalcium phosphate levels . The average daily gain (ADG) , daily intake and feed conversion (Kg DM/Kg gain) were improved with R2 and R3 which were nearly equal ,while feed conversion in terms of Kg TDN /Kg gain or Kg DCP/Kg gain was not different among groups . It could be concluded that 3% dicalcium phosphate can be used for growing lambs, which are given the best growth performance. INTRODUCTION Most grains have deficient level of calcium while legumenus contain high level of calcium in excess of ruminant requirements . Adequate calcium and phosphorus nutrition depends not only on sufficient total dietary supplies, but also on the chemical forms in which they occur in the diets. The main sources of inorganic calcium added to rations are limestone, dicalcium phosphate and bone meal (McDowell et al ., 1983 ) . The dietary calcium: phosphorus ratio also can be important. Most animals require fairly narrow calcium to phosphorus ratio usually no wider than 2:1; however, ruminants can tolerate wider ratios than monogestric animals providing the phosphorus level J. Agric. & Env. Sci. Alex. Univ., Egypt. Vol. 2 ( 1 ) 2003 41 adequate. Vitamin D was important in absorption of calcium from the intestine. An inadequate intake of Ca may cause weakened bones slow growth, and tetany . While, signs of phosphorus deficiencies are not easily recognized These two elements (calcium and phosphorus) are discussed together because they are closely associated with each other in metabolism. Also, they occur in the body combined with each other for the most part and an inadequate supply of either in the diet limits the nutritive value of both ( Hegsted , 1973 ). Objectives of this study were to evaluate the effect of dicalcium phosphate on growth performance of male lambs, rumen fermentation and biochemical blood serum parameters. MATERIALS AND METHODS Eighteen growing male lambs (impure local breed) about three months old were randomly selected from the experimental farm project in Nuclear Research Center, Atomic Energy Authority at Inshas , Egypt . Animals were then, divided into three groups on body weight basis (23.89, 24.44 and 22.50 Kg for 1 st , 2 nd and 3 rd groups, respectively). Animals of each group were kept in separate shaded pen, where they were groups fed on one of the three tested rations. Ration one ( R1 ) : CFM contained 1% dicalcium phosphate + rice straw . Ration two ( R2 ) : CFM contained 2% dicalcium phosphate + rice straw . Ration three ( R3 ) : CFM contained 3% dicalcium phosphate + rice straw . Rice straw and concentrate feed mixture (CFM) at the ratio of 25:75, respectively, the tested rations were given according to NRC (1985) allowances for growing lambs. The chemical analysis, dry matter (DM), organic matter (OM), crude protein (CP), crude fiber (CF), and ash for concentrate feed mixtures and rice straw were conducted according to A.O.A.C. (1990), which present in table 1. The required amounts of rations were offered in two equal meals twice daily at 8 a.m. and 3 p .m, feed consumption was recorded and feed conversion was calculated. J. Agric. & Env. Sci. Alex. Univ., Egypt. Vol. 2 ( 1 ) 2003 41 Lambs were weighed at the beginning of the experimental and thereafter at three weeks intervals till the end of the experiment, which lasted for 150days. At the end of experimental period, four animals from each group were used to evaluate the digestibility and nutritive value of the three experimental rations. Three digestibility trails were contacted on rams kept individually in metabolic cages; animals were fed ad libitum from the tested rations, which were offered two times daily. The intake was measured first during the preliminary period and was restricted to 90% of voluntary intake during the collection period to avoid any feed refusals. During this period animals were offered concentrate feed mixtures in the morning followed by rice straw in the noon. Residual concentrate feed mixtures and rice straw, if any, was collected next morning before offering fresh concentrate feed mixtures. Water was available for animals ad libitum. Feces and urine voided by animals were collected manually and suitable aliquot of 24 hourly collections was taken for chemical analysis. Wet feces samples were preserved with dilute sulphuric acid for crude protein estimation by micro – Kjeldahl method. The daily feces was firstly dried at 60c o over night then finally dried at 105c o for 3 hours. Feed residue, feces and urine were analyzed according to the procedures of A.O.A.C. (1990). Rumen liquor samples were taken from the three animals of each group at two consequence days following the collection periods of metabolism trails. The samples were taken by a rubber stomach tube at 0,3,6 hrs post feeding. The pH values for collected rumen liquor samples were measured immediately by using pH meter model 211digital, then filtered through two layers of cheese for determination of total volatile fatty acids (TVFA ‘s) as described by Warner (1964) and ammonia– N(NH3-N) concentration according to A.O.A.C. (1990). Blood samples were taken from the jugular vein of growing lambs once monthly during the experimental period. Blood serum was tested for total protein according to Weichselbaum TE.,(1946) Stanbio laboratory and albumin according to Doumas,et al. (1971) Stanbio J. Agric. & Env. Sci. Alex. Univ., Egypt. Vol. 2 ( 1 ) 2003 41 laboratory . 2930 East Houston street . San Antonio, Texas 78202. Globulin was calculated by the different between total protein and albumin. Serum levels of asparate amino –transferase(AST) and alanine amino – transferase (ALT) were determined according to Reitman and Frankel (1957) Quimica Clinica Aplicada S.A. E43870 Amposta / Spain. Calcium was determined by using atomic absorption ( Buck scientific 210 VGP) . Phosphorus was determined by using spectrophotometer (carry – 3EUV–visible ) .Triiodothyronine (T3) and iodothyronine (T4) levels were estimated by RIA technique using solid phase coated tubes and the tracer was labeled with 125 I (Diagnostic Products Corporation , 5700 West 96 th street, Los Angeles, CA 90045-5597, USA). Statistical analysis of obtained data was carried out according to one way analysis of variance, using the general linear model procedure, while the differences among means were tested using Duncan’s multiple range test (Duncan, 1955). RESULTS AND DISCUSSION Digestibility Trails: The daily dry matter intake expressed as gram DM / head / day, digestibility%, nutritive value and balance studies with sheep were presented in table2. Dry matter intake for R1, R2 and R3 ranged between 964.7 and 1000.8 gram/day . Dry matter intake tended to increase by increasing level of dicalcium phosphate. These results are inagreement with Erdman et al .,(1980) reported that , addition of calcium from 0.50 to 1.03 % for lactating cows significantly ( P< 0.05) increased feed intake by 1.3 Kg /day. Also, it could be observed that the R3 had the best values in digestibility of most nutrients. Digestion coefficients of dry matter, crude protein and crude fiber for R 3 were significantly (P<0.05) higher than R 1, being 70.75, 68.6 0and 57.50% respectively. Ether extract, organic matter and nitrogen free extract digestibility for the rations had no significantly differences. These results agree with those obtained by Zinn and Shen (1996) indicated J. Agric. & Env. Sci. Alex. Univ., Egypt. Vol. 2 ( 1 ) 2003 41 that supplemental calcium did not influence (P<0.05) digestibility of organic matter, nitrogen free extract and fatty acids. The nutritive value of the experimental rations in terms of total digestible nutrients (TDN) values were 66.83, 69.06 and 70.11% for R 1, R 2 and R 3, respectively. The same trend was noticed with digestible crude protein (DCP)% which recorded 9.72, 10.21 and 10.77% for R1, R2 and R3, respectively. Results of the dietary N retention shown in table 2 , indicated that positive N balance for all rations . The best value of N balance was recorded for rams fed R3 .It may be due to higher digestibility of crude protein for this ration containing 3% of dicalcium phosphate. Significantly higher positive balances of calcium and phosphorus (P<0.05) were noticed with R2 and R3 than with R1. This may be due to high dicalcium phosphate intake on these rations.