الفهرس 
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Abstract
Mohamed Soliman Moselhy Mousa. Estimation of genetic parameters for measures of calf survival, health measures, growth and their associations with subsequent performance in first lactation. Unpublished Doctoral of Science thesis, Assiut University, Faculty of Agriculture, Department of Animal Production, 2015.
The objective of this study was to estimate heritabilities of fitness and health traits of Holstein calves. Studied traits were measured on 6,072 AI sire-identified Holstein heifer calves reared at University of Minnesota, SROC facility. Calves were picked-up at 2 - 4 d old from 3 Minnesota commercial dairy farms during the period from April 2003 to May 2012. Fitness traits measured were arrival body weight (ABW); weaning weight (WWT); weaning hip height (WHH); weight gained from arrival to weaning (WG1); weight adjusted to 200 days of age (W200); height adjusted to 200 days of age (HH200); weight gained from weaning to adjusted 200 days (WG2); and height gained from weaning to adjusted 200 days of age (HG3). All these fitness traits were analyzed using multiple trait animal models via remlf90 software package. Health traits were coded relative to number of incidences that required treatment during the first 56d of age (0, 1, 2 treatment incidences). Health traits were fitted as binary traits (1= no disease, and 2 = disease incidence) with Bayesian procedures implemented in the THRGIBBS1F90 package software. The Proc MIXED procedure of SAS 9.1 was used to estimate variance components with sire fitted as a random variable. Significant fixed effects (P < 0.01) in the model were herd, yr of birth, month of birth, yr of birth x month of birth, previous nutritional experiment, and serum protein level fit as a covariate.
Heritability estimates for fitness traits ranged from 0.09 for (HG3) to 0.41 for (ABW). Heritability estimates for fitness traits tend to lower down as animal aged, which indicates that management and environmental factors may have effective influence than genetics on fitness traits as animal aged. Heritability estimates for health traits (Sc and RD) were low from both linear and threshold model.
Healthy, productive herd replacements are the result of good management before the calves are conceived and continue to the time when they enter the milking herd. Accurate records must be kept so a sound breeding program can be followed. The total process ensures that genetically superior animals will enter the herd. Once calves are born, they should be provided with a healthy environment including proper facilities, water, high quality feeds, daily observations, and health care. This kind of attention should extend beyond the baby calves. A carefully managed, well-planned facility enables dairy farmers to efficiently use their time and labor while rearing healthy replacements that freshen at 24 months of age.
Due to the low heritability estimate of AFC reported in this study (0.07) it seems that this trait is more controlled by environmental and management practices rather that genetically practices, it will be beneficial to add calf-hood fitness and Sc traits (according to their high significance) to the selection indices to reach the target AFC according to each farm strategies.
KEY WORDS: Calf-hood fitness traits, Calf-hood health traits, Holstein calves, heritability, genetic correlation, Age at first calving