Hardee Rancher
Beef and Forage Newsletter
Hardee County Extension Service
507 Civic Center Drive
Wauchula, Florida 33873
(863) 773-2164
Fax (863) 773-6861
E-mail Lgary@ifas.ufl.edu
Fall 2001
- Infertility of Cattle
-
Lockie Gary Hardee County Extension Director
What percent calf crop do you usually achieve? The national average is about
85%. However, on South Florida ranches the calf crop weaned has been recently estimated
at 68%. The reasons for these losses are many. Let's look at some of the more obvious.
Hormonal causes of infertility
Cystic ovaries result from hormonal imbalance and are most common in high
producing cows. They can cause irregular estrous cycles, continuous estrus
(chronic buller) or anestrous (no heat) depending on the type of cyst.
Retained corpus luteum persists on the ovary as a result of infection
of the uterus following abortion or early fetal death and the cow does not
come into heat.
Silent heat allows ovulation to occur but there is little or no sign of heat.
This occurs mainly because of poor nutrition.
Inactive ovaries (or anestrous) is the result of poor nutrition, lower body condition
or sickness. Such cows may have inactive ovaries and fail to come into heat.
Nutritional Causes of Infertility
Nutritional causes include under feeding (which causes inactive ovaries),
overfeeding, Vitamin A deficiency (also causing difficult calving, abortions, retained
afterbirth and infertility) and Vitamin E/selenium deficiency (causing retained
afterbirth and infertility).
The predominant cause of long calving intervals in South Florida is loss of
body condition caused by poor nutrition and disease, which causes anestrous or
failure to come into heat.
One of the most important practical points of management in
seasonal rainfall areas such as South Florida is for the postpartum cow to become
pregnant again before grass growth declines in quality and quantity in the dry season.
If reconception does not
occur, the cow is prone to become anestrous and not to cycle again until the new
grass growth with the following rains. This results in intervals between
calving of two years and ranchers cannot afford this scenario.
Pay attention to your bulls
Bulls should be in peak health and in excellent body condition just prior to the breeding
season. Bulls should not be overworked. If a bull has been ill
it should be rested and allowed to fully recover. Arthritis of
the spine of hips may cause pain and prohibit the bull from servicing (mounting
the cow), as may painful hoof conditions. High environmental temperatures may
reduce libido. Bulls need shade!
Fertility Records
Ranchers need good records of events in a cow's life to assist in cattle management.
No one can remember everything. Important dates such as calving and breeding
dates as well as immunizations or treatments for ill health need to be recorded.
A field notebook can be used from the pickup truck and transferred to a permanent
record. If you are one of those who thinks you can remember it all without
writing it down for the record, try forgetting your spouse's birthday. It's
a painful learning experience. I know. I've been there.
STAFF CONTRIBUTORS
Lochrane A.
Gary - County Extension Director
Mary Alderman
- Administrative Secretary