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Master Thesis

Analyse et modélisation des formes de courbes de lactation des caprins en France

Abstract : Currently goats are selected on the total quantity of milk produced during lactation. The selection does not take into account changes in the quantity of milk produced daily that forms the curve of lactation. It can be divided into three phases: a rising phase, followed by a peak that can sometimes maintain, and a descending phase. The degree of continued production peak is called persistence. Persistence is interesting because at the same level of total lactation production, persistent goat will have its energy deficit less marked and needs lower inputs. The objective of this study is to analyze the shapes of lactation curves and model them for genetic evaluation, especially to assess the genetic part of persistency. The study is based on analysis of test-day from 213,000 goats, made by French test program. The influence of environmental factors (rank of lactation, region, race, age at calving, month of calving, drying time, stage of gestation) were tested on lactation curve. All have an effect on the level of the curve and / or its shape. A classification was used to study the diversity of lactation curve shape. Seven different profiles were observed and some at high production levels. Different models present in literature (parametric models, semi-parametric and non-parametric) were then tested according to the rank of lactation. Including the different environmental factors (modeled with Ali and Schaeffer model) and the impact of Herd Test Day (HTD), a satisfactory model were obtained with a good adjustment to the data and a reduced number of parameters to estimate.
Document type :
Master Thesis
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https://dumas.ccsd.cnrs.fr/dumas-01400860
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Submitted on : Tuesday, November 22, 2016 - 3:38:56 PM
Last modification on : Monday, July 6, 2020 - 3:38:21 PM
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  • HAL Id : dumas-01400860, version 1

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Mathieu Arnal. Analyse et modélisation des formes de courbes de lactation des caprins en France. Sciences agricoles. 2016. ⟨dumas-01400860⟩

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