Effects of rearing feeding programs in protein accretion, heat production, and body composition of broiler breeder pullets

The objective of this study was to evaluate the effects of two different rearing programs on protein accretion (PA), heat production (HP), and body composition (BC) of broiler breeder pullets. 240-day old pullets were reared in 6 pens on 2 feeding schedules from 0-20 wks. Pullets were reared following the Cobb 500FF parent stock recommended growth curve. All treatments were fed the same Breeder 1 diet from 0-20 wks. The pullets were feed restricted with two rearing programs -skip a day (SD) and everyday (ED) with SD fed twice the amount of ED and weighed weekly with feed allotment adjusted to achieve desired body weight. At 16 wks, 6 birds from each feeding program were selected every 4 hours for sampling. This was done for a 24-hour period for the ED birds and for 48 hours for the SK birds. A CRD was employed with 2 treatments and 13 and 7 time periods for SK and ED respectively. 15N-phenylalanine (Phe) (150mM, 40% atom percent excess (APE)) was given to each selected bird by an intravenous flooding-dose of 10 ml/kg. After 10 min, birds were sacrificed by CO2 inhalation and Pectoralis major and excreta were sampled for protein turnover (PT) determination. 15N-Phe enrichment and 3-methyl histidine quantitation were determined in skeletal tissue and 3-methyl histidine was quantified in excreta using GC-MS. Fractional protein synthesis (FSR) and fractional degradation rate (FDR) were determined as %/h. The HP was measured every 2 wks from 6 -18 wks using respiratory chambers. Volumes of oxygen (VO2) and carbon dioxide (VCO2) were measured, and HP calculated using HP (kcal) = 3.872*VO2 (L/d) + 1.195 VCO2 (L/d) (Farrell, 1974). Body composition (BC) was measured every 2 wk from 6-20 wks by dual energy X-ray absorptiometry. ANOVA was performed using JMP software. Results showed that FDR was higher for SD (1.53%) in comparison to ED (0.48%) (P <0.05). PA was lower for SK than ED (P <0.05) at 12 and 24 hr post feeding (P <0.05). HP was higher in SK than ED pullets from 6-18 wk (P <0.01). SK pullets had a lower lean mass, protein mass, and higher fat mass g/kg BW at 6 wk (P <0.05) in comparison to ED pullets. Findings suggest that pullets mobilize body protein with SK feeding program in an attempt to sustain energy status in comparison to ED during the rearing period.

Key Words: Protein Accretion, Heat Production, Body Composition, Broiler Breeders.

Abstract presented at the International Poultry Scientific Forum during IPPE 2020.