A BETTER UNDERSTANDING OF BIRTH WEIGHT TO PERFORMANCE RELATIONSHIP
A BETTER UNDERSTANDING OF BIRTH WEIGHT TO PERFORMANCE RELATIONSHIP
University studies in Wyoming and data from Montana and Colorado lend credence to the following conclusion
1. |
The birth weight itself influences calving ease by 65 %. |
2. |
The female has 60-70 % influence on birth weight of her calf. |
3. |
The bull has 30-40 % influence on birth weight of his progeny. |
4. |
Pelvic measurement and angle, as well as the shape of the calf have 35-40 % |
influence on calving ease. |
5. |
Length of gestation greatly affects birth weight. A fetus can gain over one |
pound per day in the last days of gestation. |
6. |
Weather and temperature the last 30 days affect the length of gestation. |
7. |
Size and maturity of the cow influence calving ease. |
If you are not physically recording birth weights, guessing is as accurate as driving with a broken speedometer— what’ s thought to be 55 MPH may in fact be 65 of 70 MPH, and what’ s thought to be 70-80 lbs may actually be 80-90 lbs. Remember, everything is relative. Increased growth, frame and performance will increase BW. A longer bodied calf will weigh more. If a calf is expected to have genetics for growth, it will display this prior to birth as well as after. As a rule of thumb, it takes a calf weighing 86 lbs at birth to finish at 1200-1250 lbs. A cow should easily give birth to a calf weighing 8 % of her own body weight. Thus a 1200 lbs cow should give birth to a 96 lbs calf with ease. Continued selection for low birth weight will ultimately reduce the mature sizes and performance of your cattle.
22