The effect of different dietary levels of energy and protein on the production and body composition of broiler breeders

[摘要] ENGLISH ABSTRACT:A flock of 500 Hybro broiler breeders were employed to study the effect of different levelsof protein and energy on production and body composition. The daily lysine intake of thebirds were 900, 1050, 1200 and 1350 mg respectively, each fed in diets with a daily energyintake of 1800 and 2000 kJ ME to provide a 4 x 2 factorial design. Lysine was used as thereference amino acid in the experiment and all other amino acids were kept in a constantratio in every experimental diet. The total production was divided into 3 periods of 13 weekseach (week 23 - 35; week 36 - 48 and week 49 - 61) to determine the effect of the treatmentsover time. Production was evaluated by hen day production; egg weight (g/egg); egg mass(g/day); fertility; hatchability; chicks/hen/week; feed conversion and day old chick weight.Hen day production was significantly (P < 0,05) lower at the high energy intake for periodweek 49 to 61. Energy and protein levels significantly increased egg weight. Effect ofprotein was consistent during all three periods of production. Egg mass output had asignificant (P < 0,05) response to increasing levels of protein for the total period ofproduction. The birds on the high energy diet produced a significant higher egg mass per henduring the first period of production (week 23 - 35). Hatchability was reduced (P < 0,05) bythe higher energy intake for the total period of production and this effect was very significant(P < 0,01) during the final period of production. Similar to hen day production, the higherenergy had a significant (P < 0,05) negative effect on the amount of chicks produced. Thewell-known correlation between egg weight and chick weight was confirmed with theregression equation: Chick weight = 10,5 + 1,22 x Egg weight. Both energy and protein hada significant (P < 0,01) positive effect on chick weight. The feed conversion was lower atincreasing levels of amino acid intake (P < 0,01). Higher energy intake significantly(P < 0,05) increased hen weight and protein had a very significant effect during the firstperiod of production (P < 0,01).The isotope dilution technique (tritiated water) was used to estimate the body composition ofthe breeders. This was done at 5 different periods (week 27, 35, 43, 52 and 61) of theproduction period to establish changes in requirements over time. Significant correlationwere found between carcass moisture and waterspace (R2 = 0,76); fat % and carcass moisture(R2 = 0,78); protein % and waterspace (R2 = 0,35) and fat % and waterspace (R2 = 0,46). Theregression equations obtained from these correlation were employed to determine excessenergy and lysine consumed at different ages. Energy requirements were calculatedaccording to the effective energy (EE) system and the conventional ME system. Accordingto effective energy the lower energy intake was not sufficient and the maximum requirementwas calculated to be 1942 kj EE/day. The metabolizable energy calculations indicatedsufficient intakes at every treatment with the maximum requirement 1746 kj ME/day. Thelysine requirement was found to be in excess of 1050 mg lysine per day. Therecommendation for daily lysine intake is 1200 mg/day and the energy intake of breedersshould be 1900 to 2000 kj ME/day from week 23 to 35 and can be reduced to 1800 kjME/day in the final period of production.

[发布机构] Stellenbosch University