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Performance Of Broilers On Diets Having Different Levels Of Protein While Possessing Adequate Amount Of Critical Amino Acids

By: Mirza Yousaf Baig | Prof.Dr.Talat Naseer Pasha.
Contributor(s): Dr. Nisar Ahmed Mian | Dr.Muhammed.
Material type: materialTypeLabelBookPublisher: 1996Subject(s): Department of Animal NutritionDDC classification: 0488,T Dissertation note: This experiment was designed to study the effects of different protein levels while maintaining the level of critical amino acids adequate as per requirement. Six broiler starter diets SA, SB, SC, SD. SE & SP containing crude protein 22, 21.5, 21, 20.5, 20 or 19.5%, respectively and metabolizable energy 3100 kcal/kg and six broiler finisher diets PA, Fl3, FC. FD, Fl & FF containing crude protein 19. 18.5, 18, 17.5, 17 or 16.5%, respectively and metabolizable energy 3200 kcal/kg were prepared. The critical amino acids (lysine, methiomne + cystine, tryptophan, arginine & threonine) in all rations were kept at least at recommended level. 240 clay old Hubbard broiler chicks of approximately similar weight were randomly (livided into six equal groups A, B, C, D, E & F. Each group was subdivided into four replicates, each comprising of 10 chicks. These groups were fed ad libitum on above mentioned starter diets from 0 to 4th week and on finisher diets during 5th and 6th week. The results showed that feed consumption was increased (P<0.05) during finisher phase, 4th and 5th week at lower protein levels in feed. There was no difference (P>0.1) of feed consumption among various groups during the rest of experimental period. Weight gain of all groups from 0 to 6th week was similar (P>0.23). However, during first week the chicks fed on 22% protein level gained more weight (P<0.05). During second week results were inconsistent while (luring fourth week the chicks fed on Iower protein level gained similar weight as compared to the higher protein groups. The FCR of groups A, 13, C & F during starter phase and A, 13, ( I) & E during finisher phase was not different (P>O.05) which Shows that crude protein level in starter and finisher diet could he reduced to 19.5 & 17%, respectively while maintaining the critical amino acid level as per requirement. However, during first week the FCR of chicks fed on 22% protein was lower (P<O.05) than that of others, which indicate (hat during first week protein level should not be lower than 22%. The protein intake and protein efficiency ratio were not different (P>O.O5) among different groups during starter and finisher phases. Dressing percentage of different groups was not different (P>O.29). Percentages of gizzard, liver and heart weight were also similar (P>O.22) among different groups. Mortality rate during total experimental period was less than 3% and no significant difference of mortality was observed among the different groups. The economic appraisal proved that during starter phase net cash flow increased at lower protein diets while during finisher phase the net cash flow decreased greatly in the last two group E & F'. It revealed that in finisher ration reduction of crude protein level below 17.5% on which group E & F were maintained was not economical. Theses results were confirmed by realistic feed cost values.
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This experiment was designed to study the effects of different protein levels while maintaining the level of critical amino acids adequate as per requirement. Six broiler starter diets SA, SB, SC, SD. SE & SP containing crude protein 22, 21.5, 21, 20.5, 20 or 19.5%, respectively and metabolizable energy 3100 kcal/kg and six broiler finisher diets PA, Fl3, FC. FD, Fl & FF containing crude protein 19. 18.5, 18, 17.5, 17 or 16.5%, respectively and metabolizable energy 3200 kcal/kg were prepared. The critical amino acids (lysine, methiomne + cystine, tryptophan, arginine & threonine) in all rations were kept at least at recommended level. 240 clay old Hubbard broiler chicks of approximately similar weight were randomly (livided into six equal groups A, B, C, D, E & F. Each group was subdivided into four replicates, each comprising of 10 chicks. These groups were fed ad libitum on above mentioned starter diets from 0 to 4th week and on finisher diets during 5th and 6th week.

The results showed that feed consumption was increased (P<0.05) during finisher phase, 4th and 5th week at lower protein levels in feed. There was no difference (P>0.1) of feed consumption among various groups during the rest of experimental period. Weight gain of all groups from 0 to 6th week was similar (P>0.23). However, during first week the chicks fed on 22% protein level gained more weight (P<0.05). During second week results were inconsistent while (luring fourth week the chicks fed on Iower protein level gained similar weight as compared to the higher protein groups.

The FCR of groups A, 13, C & F during starter phase and A, 13, ( I) & E during finisher phase was not different (P>O.05) which Shows that crude protein level in starter and finisher diet could he reduced to 19.5 & 17%, respectively while maintaining the critical amino acid level as per requirement. However, during first week the FCR of chicks fed on 22% protein was lower (PO.O5) among different groups during starter and finisher phases.

Dressing percentage of different groups was not different (P>O.29). Percentages of gizzard, liver and heart weight were also similar (P>O.22) among different groups. Mortality rate during total experimental period was less than 3% and no significant difference of mortality was observed among the different groups.

The economic appraisal proved that during starter phase net cash flow increased at lower protein diets while during finisher phase the net cash flow decreased greatly in the last two group E & F'. It revealed that in finisher ration reduction of crude protein level below 17.5% on which group E & F were maintained was not economical. Theses results were confirmed by realistic feed cost values.

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