Dairy Selection Flashcards
Traits of Importance
Milk Production
Fertility
% Fat
Type
Temperament
Calving ease
Milk Production
h2 = 0.35
* Milk yield - 305 days after calving
* Type traits - weak positive correlation
* Fat yield - high positive correlation
* % fat = negative correlation
Fertility traits
Heifer pregnancy
First service conception
Days open
Rebreeding rate
Stayability
Type traits
Stature
Strength
Body depth
Dairy form
Rump angle and width
Edder clept
Frontal teat placement
Teat length
Feet and leg composition
Crossbreeding
Not much
Some interest to improve reproduction, but main objective is milk production
Source of genetic improvement in dairy
Mainly based on sire (due to quicker progeny production)
National Dairy Herd Improvement Association
DHIA
System of records of performance to account for sources of variation
Ultimate success of dairy industry
Utilization of record system based on comparisons of contemporaries on a similar bases
(Limited number of traits selected)
bST (Bovine Somatotropin)
Naturally occurring hormone in cows that is the major regulator of milk production
Genomics
The large scale use of DNA information to estimate the genetic merit of cattle
Genetic maps of what traits animal inherited from each of its parents is available and summarized into genomic evaluations
SNP
single nucleotide polymorphism
Genetic Disease
disease that can be passed from generation to generation
Cervical Vertebral Malfunction
Caused by a missense mutation in the bovine SLC35A3
Bovine Brachyspina Syndrome
Monogenic Autosomal recessive hereditary disorder
Main phenotype seen is shortening of spine
Caused by 3.3 kb deletion in chromosome 21
Bovine Leukocyte Adhesion Deficiency (BLAD)
Autosomal recessive disorder
Phenotype - recurring infection of soft tissue, fever, low appetite, chronic pneumonia, and diarrhea
Single point mutation at position 383 of CD18 gene
Syndactyly (Mule Foot)
Autosomal recessive with variable penetrance
Phenotype - Animals have fusion of two digits causing animals to have only one claw on at least one foot (Front feet most commonly affected)
[Carriers associated with super milk and fat]
Two indep. mutation in the bovine LRP4 gene
Bovine Progressive Degenerative Myeloencephalopathy (Weaver)
In Brown Swiss breed
Autosomal recessive disorder
Phenotype - Animal shows bilateral hind leg weakness between 6-18 months, resulting in weaving gate
Caused by BTA 4: 46-56 mb missing bases
