Breast meat yield in broilers affected by lighting and dietary energy levels in starter and finisher phases.

Abstract

The increased demand in poultry products has prompted researchers to investigate opportunities and methods which may streamline the production of valuable commodities. Two experiments were conducted in this study. Both experiments were conducted to determine whether breast meat yield (BMY) would be enhanced in broilers reared under short daylengths of 8 and 16 h if higher levels of dietary metabolisable energy (ME) were fed. In each experiment, 1000 as hatched broilers were reared in four light tight rooms, each room divided into two pens which were populated with 125 chicks in each. Within each room two levels of dietary ME were fed resulting in a 2 × 2 factorial experimental design with the main effects being daylength and dietary ME. The first experiment focused on the starter phase of 1 to 10 d. The dietary treatments consisted of a control starter ration formulated to represent the nutrient levels of a standard commercial ration and a treatment ration which was similar to the control ration however contained 15% higher ME. Live weight and performance parameters of body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR) were measured at 7 and 10 d. At 10d, three birds from each pen were randomly selected and slaughtered for body part analysis. Lighting and dietary treatment had no effect on live weight, BWG, FI and FCR at 7 or 10d. Body part analysis showed that BMY, thigh yield and drumstick yield were unaffected by lighting and dietary ME as main effects. A significant interaction between dietary ME and daylength occurred where BMY and thigh yield were reduced when broilers were fed a 15% higher ME diet and reared on 8 h daylengths. The second experiment focused on the finisher phase of 25 to 35d. Lighting treatments remained the same as the first experiment but dietary treatments differed slightly as the treatment diet contained only 10% higher ME than the control diet which was formulated to the nutrient levels of a standard broiler finisher. At 35 d performance parameters of live weight, BWG, FI and FCR were measured. It was observed that live weight and FI were reduced in broilers fed a diet containing 10% higher ME from 25 to 35d. At 35d, body part analysis from 3 broilers slaughtered from each pen revealed no significant differences in BMY, thigh yield and drumstick yield from dietary ME and daylength. Breast meat yield in broilers within the starter and finisher phase was not improved on short daylengths of 8 and 16 h through the addition of dietary ME in higher levels than that conventionally used.