Cattle Diagnostic Testing
BLAD – BLAD refers to a genetic disorder affecting primarily Holstein cattle known as Bovine Leukocyte Adhesion Deficiency. This genetic abnormality results in the reduced expression of the beta-2 integrin adhesion molecule on the surface of the leukocytes, preventing white blood cells from aggregating at the site of infection. Calves are born weak and will have recurrent infections or poor ability to heal. The most notable symptoms of the condition are enteritis and mouth ulcers. Usually, affected calves die within 2-4 months of age. BLAD is a recessively inherited condition; therefore mating of animals that are carriers may result in the birth of an affected calf.
CVM – CVM or Complex Vertebral Malformation, is a genetic disorder primarily occurring in the Holstein breed. CVM is a lethal condition that is inherited recessively. Animals with CVM have fused, misshaped cervical-thoracic vertebrae, contracted leg joints and dwarfed size. Calves with the defective allele do not survive to term and a majority of cows will reabsorb the fetus prior to parturition. No known live calves have been born with this condition.
SMA – Spinal Muscular Atrophy is a recessively inherited genetic abnormality most commonly occurring in Brown Swiss cattle. SMA is a lethal neurodegenerative disease that is characterized by a severe loss of motor neurons, causing progressive weakness and muscular atrophy. Calves begin to show symptoms 2 to 6 weeks after birth. They first show weakness in the hind legs, which develops into eventual difficulty standing. Finally, they are unable to get up, and will typically lie with front legs outstretched. Muscle wasting is evident. Eventually, calves will succumb to pneumonia as a result of their inability to stand up and move around.
Cattle Traits of Interest
Beta Lactoglobulin – Beta Lactoglobulin is the most predominant whey protein, contributing 59% of all whey proteins and 10% of total milk protein. Cows with the B variant of Beta Lactoglobulin produce higher fat milk with more casein and thus produce milk that is better for cheese manufacturing. However, the A variant of Beta Lactoglobulin is associated with greater milk volume. The B variant of Beta Lactoglobulin is more common and has a gene frequency that is greater than 50%.
Coat Colour – Maxxam offers testing for bovine coat colour through assessing the polymorphisms responsible for black and red colouration caused by mutations to the melanocortin 1 receptor gene. The black coat colour variant is caused by a single nucleotide polymorphism at codon 99.
The black trait is inherited dominantly, making it possible for black animals to parent red offspring; thus an awareness of the genotype of an animal can better facilitate breeding decisions in cases where coat colour is of interest. The red coat colour variant tested at Maxxam is caused by a deletion in codon 104 of the melanocortin 1 receptor gene. This red trait is inherited recessively, such that an animal carrying one black allele variant and one red allele variant will have a black coat, but may parent calves of either colour depending on the genotype of the other parent.
Freemartin – This condition causes infertility in the female calf born twin to a male. When a heifer twin shares the uterus with a bull fetus, they also share the placental membranes connecting the fetuses with the dam. A joining of the placental membranes occurs at about the fortieth day of pregnancy, and thereafter, the fluids of the two fetuses are mixed. In approximately ninety percent of such cases the female twin is completely infertile. Because of a transfer of hormones, or a transfer of cells, the heifer’s reproductive tract is severely underdeveloped and sometimes even contains some elements of a bull’s reproductive tract. A freemartin is genetically female, but has many characteristics of a male. Since a normal female genetically carries two X chromosomes (XX), while males carry one X and one Y (XY), detecting the presence of a Y chromosome in blood from the female calf confirms freemartinism. The presence of a Y chromosome is detectable in blood samples of affected females because of the transfer of cells between the fused placentas of the male and female twins. Unlike other diagnostic tests, where all sample types will yield results, in order to test for freemartinism, it is necessary to use blood samples.
Horned/Polled – Maxxam tests a DNA marker that shows high association with the presence of the polled trait in beef cattle breeds. The polled trait is expressed dominantly. An animal carrying one allele for the polled trait and one allele for the horned trait will themselves be polled but will pass along the allele for horns to half of their progeny. This makes phenotypic selection for the polled trait difficult. Breeders should implement this associated marker test on polled animals as a tool to increase the frequency of the polled trait in their herd.
Kappa Casein – Kappa Casein is one of the major milk proteins comprising 14.5% of all caseins and 12% of all milk proteins. Testing for variants of the Kappa Casein gene may be of value to dairy producers because the variants affect milk characteristics. Research has shown that cows with the BB genotype for Kappa Casein produce higher volume and more protein than cows with the AB or AA genotype. In fact, the B variant of Kappa Casein is associated with milk that is higher in energy, fat, minerals and casein proteins than the A variant. Because of this, the Kappa Casein B allele is better suited for cheese manufacturing although it is less common than the A allele with its allele frequency generally less than 30% for most breeds.