Abstract
ABSTRACT: Genetic disorders in Holstein cattle are a health problem that has grown worldwide in recent years, compromising the sustainability of modern dairy production. In Uruguay, Holstein-based milk production is one of the most important sectors of the country’s economy, but high levels of inbreeding have decreased the breed’s fertility in recent decades. This study investigated the presence and diffusion of lethal and semi-lethal alleles causing embryo death, abortions, fetal malformations, and neonatal diseases in Holstein calves. Using the GeneSeek® Genomic Profiler™ Bovine 50K BeadChip, we genotyped 383 calves (1-30 days-old) from 27 farms located in the main dairy region of Uruguay. Results showed a high prevalence of farms (85%) and carrier calves (21%), including one or more of the following semi-lethal or lethal alleles: Syndactylism (4.18%), brachyspina (3.39%), cholesterol deficiency haplotype (2.61%), complex vertebral malformation (2.09%), bovine leukocyte adhesion deficiency (1.04%s), and Holstein haplotypes HH1 (4.44%), HH3 (3.13%), HH4 (1.04%), and HH5 (0.26%). Most of these alleles had not been recognized previously in Uruguay. We concluded that lethal and semi-lethal mutations are widespread in the Holstein breed in Uruguay. More studies are required to determine their impact on dairy cattle fertility.
Highlights
The global use of closely related HolsteinFriesian sires, mainly of North American origin, selected mainly for high milk yield and without taking into account reproductive traits or health indicators, has resulted in a worldwide inbreeding level and reduced the genetic diversity and survival traits of the breed
The national dairy stock has decreased mainly due to a drastic fall in pregnancy rate (20– 30%), increased calving-conception interval (MEIKLE et al, 2013), and high birth-to-weaning calf mortality, averaging 18% (SCHILD et al, 2020). Another contributing factor could be the predominance of North American Holstein-Friesian genetics in the national herd (90%), a breed in which most recessive mutations affecting reproductive efficiency and health traits have been discovered in recent years
The information generated by the 50K BeadChip included most of the lethal and semi-lethal mutations recognized in beef and dairy cattle
Summary
The global use of closely related HolsteinFriesian sires, mainly of North American origin, selected mainly for high milk yield and without taking into account reproductive traits or health indicators, has resulted in a worldwide inbreeding level and reduced the genetic diversity and survival traits of the breed This loss of natural genetic resistance to diseases and the decreased fertility, vigor, and longevity of the breed, is compromising the sustainability of modern dairy production (Rodríguez-Martínez et al, 2008). The national dairy stock has decreased mainly due to a drastic fall in pregnancy rate (20– 30%), increased calving-conception interval (from 131 to 175 days between 1997 and 2011) (MEIKLE et al, 2013), and high birth-to-weaning calf mortality, averaging 18% (SCHILD et al, 2020) Another contributing factor could be the predominance of North American Holstein-Friesian genetics in the national herd (90%), a breed in which most recessive mutations affecting reproductive efficiency and health traits have been discovered in recent years
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