RESPONSES OF BROILER CHICKS TO DIFFERENT LEVELS OF LYSINE AND METHIONINE

Abstract

The three studies were designed to determine the deficiency of essential amino acids, mainly lysine and methionine used in local Sudanese broiler diets, and the effect of completion of the diet with synthetic lysine or/methionine on the performance of broiler chicks and their economic impact. The first experiment was carried out during winter season. In this experiment, a hundred one day-old unsexed broiler chicks were used, to determine the deficiencies of amino acids in the local diet used. Five experimental diets, (A, B, C, D and E), based on cereal grains were formulated. The local diet used (A) was deficient in both lysine (4.36%), and methionine (6.52%) and phosphorus (19.16%), diet (B) supplemented with phosphorus, diet (C) supplemented with methionine (0.49%), diet (D) supplemented with lysine only (1.2%) and diet (E) supplemented with both lysine and methionine (1.2, 0.49%). All diets had similar crude protein (22%) and methabolizable energy (2300kcal). Chicks fed on diets E and D showed significant (P<0.05) differences compared to control diet (A) in average live body weight gain throughout the study duration the study period, chicks in group (C) showed significant more difference (P<0.05) with group (A) during the 3rd and 6th weeks and other groups showed no significant (P>0.05) differences compared to control (A). Feed intake for group (A) showed significant (P<0.05) different with D, E and C, other groups showed no significant difference (P>0.05) . The treatment groups did not differ significantly (P>0.05) on hot and cold carcass dressing percentages, commercial cuts (breast, drumstick and thigh), meat percentage of these selected cuts and non- xiii carcass body components (liver, heart, head and gizzard). The average subjective meat quality scores (colour, tenderness, flavour, juiciness) did not differ significantly (P>0.05) among dietary treatments. Scores given were above moderate acceptability level. Four hundred day-old unsexed broiler chicks were used in the second experiment to determine the optimum level of lysine and methionine in broiler diet under Sudan condition. Chicks were randomly distributed to five treatments with eight replicates with ten chicks per each. Five iso caloric (3100kcal), isonitrogenous (22%) were formulated. Diet (A) was the best diet in the first experiment (1.2% lysine+ 0.49meth) used as control, diet (B) similar to diet (A) but without broiler supper concentrate, diet C (1.3 lysine+ 0.56meth), diet (D) (1.4 lysine + 0.6%meth), and diet (E) (1.5% lysine + 0.63%meth). Results obtained revealed that group (E) differ significantly (P<0.05) with other groups in feed intake, and group (D) was significant (P<0.05) with group (A). Groups E, D, C and B showed significant difference (P<0.05) with group (A) where as no significance (P>0.05) between them in average live body weight. The slaughter data showed that as the level of lysine and methionine increased, eviscerated carcass weight, hot and cold dressing percentages and the yield of commercial cuts (breast, drumstick and thigh) increased significantly (P<0.05) compared to the control diet. The average meat yield from the commercial cuts increased significantly (P<0.05) with the increase of the synthetic lysine and methionine levels. The carcass chemical composition showed no significant difference (P>0.05). The marginal profit obtained from chicks fed on-diet (E) recorded (1154-32S.D) as the highest followed by group D (1074.67SD) and diet (A) (373.46S.D) as the lowest marginal profile. xiv 200 chicks were selected from 1500 chicks after a week of adaptation, for the third experiment, to determine if the addition of both synethetic lysine and methionine could replace the broiler supper concentrate, so to decrease feed cost and keep or increase broiler chicks growth. Five experimental diets (A, B, C, D and E) were formulated. Increasing levels of L-lysine and DL-methionine were supplemented without broiler supper. Concentrate for diets A (1.2 lysine+ 0.49%meth) B(1.3%lysine+ 0.56%meth), C (1.4 lysine+ 0.59% meth) and D (1.5% lysine+0.63%meth), diet E (1.5% lysine+ 0.63%meth) with super- concentrate. Results obtained showed that group (E) recorded significant difference (P<0.05) with groups D, C, B and A, also groups D, C showed significant differences with groups B and A in feed intake, average final body weight and average body weight gain. In feed conversion ratio group (A) (3.45) significantly differ (P<0.05) with groups C (2.85), E (2.67) and D (2.6). Also group B (3.27) significantly differ (P<0.05) with group E and D as overall. Level of synthetic lysine and methionine without supper-concentrate did not affect significantly (P>0.05) on non- carcass components (heart, liver, gizzard, head and legs), hot eviscerated carcass, commercial cuts (breast, drumstick and thigh), the three selected cuts meat yield percentages. Also the average subjective meat quality scores (colour, tenderness, flavour and juiciness) did not differ significantly (P>0.05) among the dietary tested groups. The economical study for this experiment indicated that treatment E (690.05S-D/kg) recorded the highest value of marginal profit followed by treatment D (485.9S.D/kg) (192.57S.D/kg) as the lowest value.