Mathematical Modeling for Hatchability of Chicken Eggs
Kuurman, Willem Wiecher
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https://hdl.handle.net/2142/83541
Description
Title
Mathematical Modeling for Hatchability of Chicken Eggs
Author(s)
Kuurman, Willem Wiecher
Issue Date
2002
Doctoral Committee Chair(s)
Grossman, Michael
Department of Study
Animal Sciences
Discipline
Animal Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Biostatistics
Language
eng
Abstract
Assessment of the probability for failure to hatch, due to either infertility or embryonic mortality during incubation, is important to evaluate reproductive efficiency in poultry. The main objective of this thesis, therefore, was to develop or improve mathematical models that describe probabilities of fertility (the complement of infertility) and embryonic mortality. Appropriate statistical procedures to estimate model parameters were proposed. Data sets used to validate the developed models were of eggs from inseminated hens, broken open to determine fertility; number of spermatozoa captured in the perivitelline layer (Nsperm); and day of mortality during incubation. Three models were developed to assess fertility. First, Nsperm decreased exponentially with time after insemination. Results indicated that Nsperm increased as dose of spermatozoa inseminated was increased four- to eightfold, if an egg was oviposited within one day after the previous egg, and that a relatively large proportion of variation was variation among individual hens. Second, number of spermatozoa that have to be captured to fertilize an oocyte was distributed as log-normal. Results indicated that as time after insemination increased more spermatozoa might have to be captured to fertilize an oocyte. Third, probability of fertility was described by a normal sigmoidal function of time after insemination. To assess the distribution for time of embryonic mortality a model developed previously was improved. Two of the improvements were that the distribution was modeled by a diphasic Weibull distribution, instead of a diphasic logistic distribution and that model parameters were estimated from noncumulative proportions of mortality, instead of cumulative proportions of mortality. Results showed that time of embryonic mortality was influenced by hatch and by number of days that eggs were stored before incubation. To estimate parameters, the method of maximum likelihood was appropriate for most models. The models developed here to describe probabilities of fertility and of embryonic mortality can help to assess factors that affect reproduction, so as to improve reproductive efficiency. These models might be improved further, by including random effects for individual birds. Alternative statistical procedures to estimate parameters for these mixed models, such as Bayesian analysis, should be studied.
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