...................................................................................................................... ii ACKNOWLEDGEMENTS ............................................................................................ iv TABLE OF CONTENTS ..................................................................................................v CHAPTER 1 1.1 Literature Review ...............

Life history theory studies the evolution of traits related to reproductive fitness. Fertility and parental investment are key life history traits which, from an evolutionary standpoint, appear strongly interrelated. The aim of this work was to analyze the genetic and environmental structure and relationship of two behaviors associated with reproductive fitness: total number of offspring and me...

Reproductive wastage was investigated over two seasons among sheep grazing non-oestrogenic pastures. The results show that approximately 25 percent of the ewes were not cycling when the rams were joined. Ovulation rates were consistently low, averaging 1.09, and fertilization rates consistently high, averaging 93 percent. Embryonic mortality varied widely between properties and years, but avera...

The analysis focused on model fitting of 2 ewe reproductive traits, litter size, and days to lambing (interval between the introduction of the ram into the flock and the subsequent parturition of the ewes). The experimental data set of the Universitat Autònoma of Barcelona flock was used, including 1,598 records of litter size and 1,699 records of days to lambing from 376 Ripollesa ewes between...

One of the main deficiencies affecting animal breeding programs in Peruvian alpacas is the low reproductive performance leading to low number of animals available to select from, decreasing strongly the selection intensity. Some reproductive traits could be improved by artificial selection, but very few information about genetic parameters exists for these traits in this specie. The aim of this...

this study was evaluated some strategies and determined the suitable selection index for afshari sheep using simulated data. the relative importance of traits was determined based on the estimated economic values and consequently, the most benefit traits were applied to selection indexes construction. the interest indexes were different combination of traits including ewe body weight (ebw), ann...

OBJECTIVE This study estimated the genetic parameters for productive and reproductive traits. METHODS The data included production and reproduction records of animals that have calved between 1979 and 2013. The genetic parameters were estimated using multivariate mixed models (DMU) package, fitting univariate and multivariate mixed models with average information restricted maximum likelihood...

The objective of this study was to assess variance components and genetic parameters for fat and protein content in Tsigai sheep using multivariate animal models in which fat and protein content in individual months of lactation were treated as different traits, and univariate models in which fat and protein content were treated as repeated measures of the same traits. Test day measurements wer...

A 4-year interdisciplinary study was performed to compare two organically managed sheep production systems, using 118 ewes and 24 ha each. The systems differed in the ewes' reproduction rhythm: one lambing per ewe per year (1L/1Y), with the aim of balancing feed self-sufficiency and lamb marketing periods v. three lambings over 2 years (3L/2Y), with the aim of maximising ewes' productivity. The...