Curvas de lactancia e identificación QTLs asociados a características productivas en ganado Holando y cruza Holando por Jersey
The general objective of this thesis was the modeling of lactation curves to estimate milk production traits applied to the identification of chromosomal regions and genes associated with these traits, in Holstein and crossbred HolsteinxJersey cows from the central dairy region of the province of Sa...
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| Formato: | Tesis doctoral acceptedVersion |
| Lenguaje: | Español |
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Facultad de Ciencias Veterinarias
2022
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| Acceso en línea: | http://repositoriouba.sisbi.uba.ar/gsdl/cgi-bin/library.cgi?a=d&c=avaposgra&cl=CL1&d=HWA_6337 http://repositoriouba.sisbi.uba.ar/gsdl/collect/avaposgra/index/assoc/HWA_6337.dir/6337.PDF |
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| Sumario: | The general objective of this thesis was the modeling of lactation curves to estimate milk production traits applied to the identification of chromosomal regions and genes associated with these traits, in Holstein and crossbred HolsteinxJersey cows from the central dairy region of the province of Santa Fe, Argentina.\nIn Chapter 2, descriptive statistics for fertility and survival were generated to ensure that the estimation\nof productive parameters were reliable, consistent and adequate with the production system under study and avoid distortions in the results of subsequent analyzes. The average age at the first service was 20?3\nmonths (average ? standard deviation), the age at the first conception was 21?4 months and the age at\nthe first calving was 30?4 months. The interval from calving to conception interval had an average\nduration of 139?92 days and the interval between services was 44?32 days. The gestation period had an\naverage duration of 265?49 days and the calving interval was 398?108 days. The average lactation\nlength was 301?129 days and the average longevity of the animals under study was 5.6?2.x years. In Chapter 3, a series of mathematical models to describe the lactation curve for the five productive variables: milk production (PL), protein percentage (PP), protein production (ProdP), fat percentage (PG) and daily fat production (ProdG), were compared. The results showed that the model of random regression using a Legendre polynomial of sixth grade was the best method to model the lactation curves\nfor the five variables evaluated. In Chapter 4, estimates for the production of milk, fat and protein\naccumulated at 305 days and fat and protein content were obtained from the random regression model\nusing a sixth-grade Legendre polynomial. In general, milk production traits were affected by proportion of Holstein, lactation number, and year and season of calving.\nWith these phenotypes, in Chapter 5, a complete genome association study was conducted using 50,000\nSNPs distributed in the bovine genome using mixed linear models, considering the factors that affect\nthe traits studied, population structure and genetic relationships. In this strict context of correction of\nmodels and using the adjustment by multiple comparisons of Bonferroni at genome level, no statistically\nsignificant SNPs were found associated with any of the productive characteristics considered. However,\nusing a less conservative level of significance and inspecting the Quantil-Quantil graphs, 15 SNPs\nassociated with the productive characters evaluated were identified. The analysis made possible to calculate the proportion of phenotypic variance captured by the SNPs, being 0,16 for PL305 and\nProdP305, 0,11 for ProdG305, 0,03 for PGm and 0.09 for PPm. The search for nearby genes was performed according to the gene annotation of the bovine genome corresponding to the UMD3.1 assembly and taking into account the calculated linkage disequilibrium (r2 = 0.22 ± 0.27 at an inter-SNP\ndistance of 25-50Kb). It was found that 11 of the genes identified were associated in previous studies\nwith dairy productive traits (IRS2, VEGFA, TCF7L2, RF00100, DCDC2 and OCA2) and with different\naspects of the mammary gland such as metabolism (IRS2, LIN28A), the development (VEGFA,\nTCF7L2), tissue (LOC525599) and the central ligament (PKHD1). Other genes were associated with |
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