Mohammad Afrouziyeh | ALES Graduate Seminar

Date(s) - 24/06/2021
8:00 am - 9:00 am

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES PhD Final Exam Seminar by Mohammad Afrouziyeh. This seminar is open to the general public to attend.

Meeting ID: 984 0531 0752
Passcode: 920174
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Meeting ID: 984 0531 0752
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Thesis Topic: Metabolic status and reproduction in broiler breeders: A view on the impact of growth trajectories

PhD with Dr. Martin Zuidhof.

Seminar Abstract:

Broiler breeders are subjected to feed restriction programs to control excessive growth. However, current levels of feed restriction are becoming so severe that raises welfare and suboptimal reproductive performance concerns in underfed breeders. To circumvent the issue, I studied new strategic growth curves in this thesis. Birds in all studies were fed using a precision feeding (PF) system. First study investigated the effect of minor feed restriction on feed efficiency in two heritage lines of chickens. The growth data of the birds were fit to a mixed Gompertz model with bird-specific random coefficients for mature BW, rate of maturing, and both to evaluate the effects of random terms on the fitting and predictive performance of the models. The model with both random coefficients was determined to be the most parsimonious model, which improved traditional Gompertz growth model. Minor feed restriction increased production efficiency, but this was not confirmed for New Hampshire strain in the current study. The second study was conducted with 40 broiler breeder pullets reared on one of ten target growth trajectories, which were designed with 2 levels of the amount of prepubertal growth (Standard g1 and High g1) and 5 levels of pubertal growth timing (I2). Analysis of covariance showed that for every week of earlier I2, 24 wk body fat increased by 0.38%; pullets came to lay earlier by 0.49 day; egg production and egg mass increased by 0.33 egg/hen/d and 0.916 g/d in the High g1 treatment but decreased by 0.27 egg/hen/d and 0.29 g/d in the Standard g1 treatment, respectively. Increasing g1 reduced feeding motivation index by 1.6 and 0.8 visits/meal during rearing and laying phase, respectively. The next study investigated effects of the growth trajectories on energy efficiency of birds. It also tested the effects of chunking data into different sizes and inclusion of random terms associated with individual maintenance ME and ADG requirements on fitting and predictive performance of ME partitioning models. A model with inclusion of random term associated with individual maintenance requirement in a 3wk chunk size was chosen as the most parsimonious based on greater fitting and predictive performance among the models. Standard g1 treatment had lower residual heat production compared to the High g1 treatment, indicating greater efficiency in utilizing the ME consumed. The fourth experiment was conducted in extension of the second experiment to evaluate the intergenerational effects of a reduced degree of maternal pre-pubertal phase growth restriction and earlier maternal pubertal phase growth on offspring growth and development. Two replicated broiler studies were conducted that varied in maternal age (35 and 42 wk). Overall, relaxed growth restriction during pre-pubertal and earlier pubertal growth increased male offspring growth by 2.2% and produced more efficient female broilers by reducing FCR by 0.017. The fifth study evaluated some metabolic biomarkers that gave clues to the metabolic shifts resulting from sexual maturation. A total of 36 broiler breeder pullets were used, of which 30 were randomly assigned to one of 10 unique growth trajectories, and 6 were assigned to an unrestricted group. The growth trajectories varied in total gain in the prepubertal and pubertal growth phases ranging from the breeder-recommended target BW to 22.5% higher, in 2.5% increments. Increasing prepubertal and pubertal BW gains by more than 15% of the breeder-recommended target BW triggered fat metabolism and yolk precursor synthesis, which consequently advanced sexual maturity. We concluded that certain metabolic signatures can be used to predict the metabolic status linked to the bird’s maturity. The sixth experiment was conducted in extension of the fifth experiment to determine correlation between plasma concentrations of corticosterone measured by ELISA and LC-MS/MS methods and to investigate the effects of the high and low photostimulation BW on plasma corticosterone levels. Plasma corticosterone levels were not affected by photostimulation BW, indicating same welfare status between the precision fed high and low BW groups. Concentrations of plasma corticosterone measured using ELISA method were highly correlated (r = 0.95) with values measured using LC-MS/MS method. In conclusion the current breeder-recommended target BW is low for optimal reproductive performance. Increasing prepubertal BW gain by 10% and advancing the pubertal growth phase by 20% could increase margin over feed and chick cost for hatching egg producer and supply chain sectors.