EFFECT OF REDUCED DIETARY CRUDE PROTEIN SUPPLEMENTED WITH LIMITING AMINO ACIDS ON GROWTH AND CARCASS CHARACTERISTICS OF GRAMASREE MALE CHICKS
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Date
2021-12-30
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES MANNUTHY, THRISSUR
Abstract
An experiment was conducted at the Department of Poultry Science, College of
Veterinary and Animal Sciences, Mannuthy, Kerala to study the effect of reduced
dietary crude protein supplemented with limiting amino acids viz. methionine, lysine,
threonine and tryptophan on growth and carcass characteristics of Gramasree male
chicks from day-old to eight weeks of age.
Two hundred and eighty, day-old chicks were randomly allotted into five dietary
treatments with four replicates having 14 chicks each in a completely randomized
design. The different dietary treatments in this study include a control diet (T1)
formulated as per ICAR (2013) nutrient requirements for Indian improved native breeds
and their crosses with 21 per cent CP and 2800 kcal ME/kg using corn, soya bean meal,
wheat bran and de-oiled rice bran. The other treatment diets T2, T3, T4 and T5 were
prepared by reducing the CP content to 20, 19, 18, and 17 per cent, respectively with
2800 kcal ME/kg and supplementation of synthetic amino acids to meet the
requirements of first four limiting amino acids viz. methionine, lysine, threonine and
tryptophan at 0.46, 1.10, 0.70 and 0.20 per cent levels, respectively.
The results showed that, up to eight weeks of age, reducing the dietary CP level
up to 17 per cent with limiting amino acid supplementation did not affect the growth
performance of birds. The mean cumulative body weight, cumulative weight gain,
cumulative feed consumption and cumulative FCR of all the five treatments were
statistically comparable. Carcass traits like breast meat yield, giblet weight, dressing
percentage and ready to cook yield were also not affected by different dietary
treatments. However, the mean abdominal fat content in 17 and 18 per cent CP
treatments were significantly (p<0.05) higher than the other treatment groups. Livability
was 100 per cent in treatments with 20 and 19 per cent CP (T2 and T3, respectively)
and 98.21 per cent in treatments with 18 and 17 per cent CP (T4 and T5, respectively).
There was no significant effect of lowering dietary CP levels and limiting amino acid
supplementation on dry matter digestibility, crude fibre digestibility and ether extract
digestibility of the birds maintained in any treatment. The crude protein digestibility and
nitrogen retention per cent in birds increased significantly (p<0.01) with reduction in
CP level, showing highest crude protein digestibility and nitrogen retention in treatment
with highest CP reduction (T5). Nitrogen retention was improved by 10.85 per cent in
birds fed with 17 per cent CP diet compared to the control. The total feed cost per bird
as well as feed cost per kg live weight of bird was lowest in treatment with 17 per cent
CP, which saved Rs. 1.64 for every kilogram of feed formulated.
Based on the overall results of this study, it could be concluded that, the dietary
crude protein level of Gramasree male chicks can be reduced up to 17 per cent with
limiting amino acids supplementation to reduce the feed cost without affecting the
growth performance of birds for rearing up to eight weeks of age. Also, the use of
limiting amino acid supplementation to low CP diets was also effective in reducing
nitrogen excretion in birds thus to prevent environmental pollution. Further research in
Gramasree male chicks is needed to determine the level up to which CP can be reduced
using synthetic amino acids without altering their performance.
Description
Thesis submitted in partial fulfilment of the requirement for the degree of Master of Veterinary Science in Poultry Science