By Gary Sliworsky
Ag rep, Emo
Calving season is right around the corner. The following is Part 1 of an article on congenital defects that can occur in cattle:
Congenital defects can cause abortion or be present at time of birth. They are uncommon, but do occur in most breeds of cattle.
Defects are abnormalities in skeleton, body form, and body functions. Abnormalities may result from genetic or environmental causes.
When the environment is the cause, adjustments can reduce further economic losses. However, genetic (inherited) causes are much more complex and difficult to correct.
Environmental or non-genetic causes have the same economic results as genetic causes, but are far easier to rectify. Simply correcting the environment will remove the problem.
There are many environmental factors, including disease and diet.
Certain conditions show that an abnormality is likely to be environmental in nature:
•the abnormality coincided with an environmental factor and was absent upon removal of the factor;
•the abnormality occurred in groups of non-related individuals; and/or
•the symptoms are similar to those of an abnormality known to result from environmental factors.
Chromosomes inherited from parents determine an animal’s genetic make-up. There are many genes in each chromosome.
Genetic abnormalities occur when genes are missing, in excess, mutated, or in the wrong location (translocation).
A few genes directly can cause an abnormality, however, these are rare. Usually, these genes are recessive, meaning two must be present to cause an abnormality.
Both parents must be carriers of the gene for a calf to be abnormal.
In this case, only one of every four offspring will be abnormal. Two will be carriers and one will be normal.
Certain conditions show that an abnormality is likely to have a genetic origin:
•the abnormality is more common in a group of related animals; and/or
•the symptoms are similar to those of an abnormality identified through test matings.
Study of an animal’s chromosomes using blood samples can identify several genetic defects.
Next week’s article will go through some of the more common genetic defects that can occur in cattle.
Dates to remember
•Jan. 12—“Vaccination strategies to maximize herd health,” featuring guest speaker Dr. Les Byers, 7 p.m., Millennium Hall in Stratton;
•Jan. 19–Rainy River Cattlemen’s Association annual meeting, 7 p.m., Our Lady of the Way School in Stratton;
•Jan. 26—General on-farm procedures owners often can do, presented by the Nor-West Animal Clinic veterinarians, 7 p.m., Millennium Hall in Stratton (note the date change); and
•Jan. 27–Grower pesticide safety course (call 1-800-652-8573 to register).