Date of Graduation

12-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level

Graduate

Department

Poultry Science

Advisor/Mentor

Anthony, Nicholas B.

Committee Member

Wing, Terry

Second Committee Member

Dridi, Sami

Third Committee Member

Maxwell, Charles V.

Fourth Committee Member

Bottje, Walter G.

Keywords

FCR; Feed Efficiency; Quail; Regression; RFI

Abstract

The concept of feed efficiency (FE), one unit of feed required to improve one unit of desired output, is relatively simple. However multiple outputs are desired in a commercial poultry breeding program, resulting in the need for nutrients to be partitioned in a particular manner. At the broadest level, nutrients are partitioned between production and maintenance requirements. The requirements for production and maintenance varies between birds. It is the poultry breeder’s responsibility to select individuals most aligned with the breeding objective. Irrespective of the breeding objective, various related and non-related traits influence a bird’s FE. To effectively improve FE, the breeder must be aware of the relationship between FE and the other traits in the breeding program to understand the advantages and consequences that will result from FE selection.

Over several decades, poultry researchers and breeders have developed different FE strategies to consolidate and simplify the relationship between feed intake and biological functions necessary for life and growth. However, current FE strategies are still unable to account for large portions of the variation in feed intake and do not give the poultry breeder the ability to select for production and maintenance components separately. The objective of this set of experiments was to first develop four independent sublines of Japanese coturnix quail through the selection of 4 different FE strategies. Prior to this study, the Japanese quail underwent long term selection for high 4-week body weight making them an appropriate model for the commercial broiler. Two of the FE strategies, feed conversion ratio (FCR) and residual feed intake (RFI), are widely used in commercial farming. The remaining two FE strategies have been tested in simulations and provide an alternative to traditional RFI. These alternative RFI models were developed to allow the breeder to identify bird specific growth and maintenance efficiencies through random regression in concert with population parameters to explain variation in feed intake. After four generations of selection, genetic and phenotypic parameters for each FE strategy and their component traits were evaluated and compared between lines. We hypothesize different genetic and phenotypic relationships will be present between FE strategies and their FE components such as bodyweight, weight gain, and feed intake. These differences should indicate if certain FE strategies are more suitable for improving production efficiency over maintenance efficiency or vice versa.

In trials 2 and 3 we included the random bred control line (RBC) that each of the four sub-lines originated, allowing for comparisons to be made between FE selected lines and a non-selected FE line. The objective of these two trials were to evaluate growth and development characteristics between lines. Trial 2 involved evaluating the development of supply and demand organs in each line to determine how each FE strategy influenced the way nutrients were partitioned between the different types of organs. Feed efficiency strategies superior at promoting growth efficiency, are likely to have higher weights for demand organs such as breast and leg meat. Whereas, feed efficiency strategies promoting maintenance efficiency will likely result in smaller relative weights of visceral organs known to account for large maintenance costs in proportion to their size. In addition to evaluating the development of supply and demand organs, the second trial focused on phenotypic differences in the component traits of FE during FE testing between 14 and 28 days of age. This two-week period served as the testing period during the development and selection of the four lines. This information will help to confirm the genetic and phenotypic relationships found in trial 1.

In the third trial, growth curves were developed for all FE lines and the RBC. Selection for FE affects a variety of growth traits. Researchers and poultry breeders are most commonly interested in feed efficiency’s association with weight gain and ending body weight. However, additional insight can be gained by evaluating the growth curve. Measuring growth curve parameters identifies the weight and age a bird is expressing its most rapid weight gain along with the weight of maturity. Identifying these parameters in each line shows how selection for different FE strategies shifts the growth due to changes in inflection point and asymptote values.

The purpose of this set of experiments was to test the practicality of newly proposed FE strategies and investigate how these along with traditional FE strategies influence production related traits during the grow out period. Providing this knowledge to poultry breeders will allow them to choose the FE strategy most appropriate for their breeding objective.

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