Feeding, feed-seeking behavior, and reproductive performance of broiler breeders under conditions of relaxed feed restriction

Zukiwsky, N. M., M. Afrouziyeh, F. E. Robinson, and M. J. Zuidhof. 2021. Feeding, feed-seeking behavior, and reproductive performance of broiler breeders under conditions of relaxed feed restriction. Poultry Science 100:119-128. doi https://doi.org/10.1016/j.psj.2020.09.081

body weight, broiler breeder, hunger, peer-reviewed, Precision Feeding, Publication, Research Showcase 2021, sexual maturity, unrestricted feed intake

PIP Author(s)

About

Publication Metrics

Broiler breeders are feed restricted to control BW throughout their life cycle. Feed restriction leads to poor welfare. However, unrestricted feed intake can lead to health issues related to rapid growth and obesity, which is also considered to be a welfare issue. The objective of this study was to implement a variety of BW trajectories using a precision feeding system (PF) to evaluate the effect of varying degrees of relaxed feed restriction on feeding, feed-seeking behavior and reproductive performance of broiler breeders.

Approach

Ross 708 female broiler breeders (n = 36) were fed using a precision feeding system from 2 to 42 wk of age. Ten BW trajectories were created from a multiphasic Gompertz growth model that increased growth from 0 to 22.5% in the prepubertal and pubertal phases of growth, in 2.5% increments. Six unrestricted birds were not limited to a maximum BW. All birds had access to 2 PF stations 24 h per day and ad libitum access to water throughout the experiment. Station visit frequency, average daily feed intake (ADFI), the number of meals, and meal size were derived from records in the PF system database. A single RFID-equipped nest box (8 nesting sites) and trap nest box (10 nesting sites) were introduced to the chamber at 14 wk of age so that pullets could familiarize themselves with the nests before the onset of lay. Each RFID nesting site was equipped with an RFID reader which identified a hen with each egg that was laid. Eggs were collected, weighed, and assigned to individual hens daily.

Analysis of Results

Body weight increased as trajectory-specific BW targets increased from 6 to 28 wk of age. Differences of BW between BW trajectories decreased during the laying period, which was a result of individual bird variation within BW trajectories. Station visit frequency decreased per kilogram increase in BW for all birds during rearing and lay, and within feed-restricted birds during lay only. The number of meals and ADFI increased with age, which reflected nutrient intake to support maintenance, growth, and reproductive requirements. Mean egg weight (EW) of all birds increased by 0.72 g per kilogram increase in BW from 22 to 41 wk of age. From 22 to 29 wk of age, mean EW of feed-restricted birds increased by 2.78 g per kilogram increase in BW. For every kilogram increase in BW, age at first egg comparing all birds decreased by 10.83 d. Two unrestricted birds came into lay before photostimulation. In contrast with the hypotheses, BW increased up to 22.5% above the recommended target did not reduce feeding and feed-seeking behavior, or negatively impact reproductive performance.

Application

BW increased up to 22.5% above the recommended target did not reduce feeding and feed seeking behavior, or negatively impact reproductive performance. Thus, there is potential to increase broiler breeder BW targets and reduce the degree of feed restriction without reducing reproductive performance. The BW results of the present study indicated that optimal BW trajectories may strongly depend on the individual broiler breeder.

Abstract

Broiler breeders are feed restricted to optimize reproductive performance. A randomized controlled study was conducted to investigate the effect of increasing female broiler breeder BW on feeding, feed-seeking behavior, and reproductive performance. It was hypothesized that a greater BW would decrease feeding and feed-seeking behavior, and reduce reproductive performance. Ross 708 female broiler breeders (n = 36) were fed using a precision feeding system from 2 to 42 wk of age. Ten BW trajectories were created from a multiphasic Gompertz growth model that increased growth from 0 to 22.5% in the prepubertal and pubertal phases of growth, in 2.5% increments. Six unrestricted birds were not limited to a maximum BW. Body weight was evaluated as a 2-way ANOVA. Two linear regression analyses were conducted, one which included all birds and one which excluded the unrestricted birds. For the regression analyses, BW at photostimulation (22 wk of age) was used as the continuous independent variable to represent the degree of variation between trajectories. Differences were reported at P ≤ 0.05. Body weight increased as trajectory-specific BW targets increased from 6 to 28 wk of age. Differences of BW between BW trajectories decreased during the laying period, which was a result of individual bird variation within BW trajectories. Station visit frequency decreased per kilogram increase in BW for all birds during rearing and lay, and within feed-restricted birds during lay only. The number of meals and ADFI increased with age, which reflected nutrient intake to support maintenance, growth, and reproductive requirements. Mean egg weight (EW) of all birds increased by 0.72 g per kilogram increase in BW from 22 to 41 wk of age. From 22 to 29 wk of age, mean EW of feed-restricted birds increased by 2.78 g per kilogram increase in BW. For every kilogram increase in BW, age at first egg comparing all birds decreased by 10.83 d. Two unrestricted birds came into lay before photostimulation. In contrast with the hypotheses, BW increased up to 22.5% above the recommended target did not reduce feeding and feed seeking behavior, or negatively impact reproductive performance.