Calf Crop Percentage may be the most important production calculation that a cow/calf producer can record. The reason for this statement is that Calf Crop Percentage has both an input and output component. Inputs include genetic selection, nutrition and management, management during the breeding season, management during the calving season and management from calving to weaning. The output component is reproduction and reproduction impacts total pounds of weight that is available to sell at weaning.
Percentage calves weaned of females exposed is the number of calves weaned based on the females that were exposed to the bulls to produce the calves that are being weaned. Mathematically it is the number of calves weaned (numerator) divided by the number of females exposed to produce that calf crop (denominator) and this number times 100 to get it to a percentage [(# calves weaned/# cows exposed) x 100].
Sometimes the challenge is that the numbers needed to do the calculation are collected over a year apart so good records are needed. For females that wean a calf in October of 2015, the number of females exposed would be the number of females exposed to a bull during the breeding season in 2014.
As an example, 300 cows were exposed to the bull and 255 cows weaned a calf. Calf Crop Percent is 85% ((255 calves weaned/300 cows exposed to the bull) x 100 = 85%). Records indicate 37 cows had no calving records, 6 calves lost at calving, and 2 calves were lost between calving and weaning. It is assumed the 37 head did not get pregnant during the breeding season because there was no record that they aborted.
Using this information, more information can be extracted from these records so that “weak links” in the production system can be identified.
- Pregnancy percentage is 87.7% ([(300 - 37)/300) x 100] = (263/300) x 100)].
- Calving percentage is 97.7% [(263 - 6)/263) x 100) = (257/263) x 100].
- Weaning percent is 99.2% [(257 - 2)/257) x 100 = (255/263) x 100].
Multiplying pregnancy percent x calving percent x weaning percent should be close to 85% (.877 x .977 x .992 = .8499).
Cow reproductive performance can be evaluated by age group using the process described above. Some of the challenge is in how to account for pregnant females that enter and leave the herd during the production cycle. There are Standard Performance Analysis (SPA) guidelines that outline how to calculate production measures for the cow herd and how to account for pregnant females that enter and leave the herd. For more information, please see the SPA Calculations & Worksheet available on the National Cattlemen's Beef Association website.
The greatest loss of calves to wean is due to cows not getting pregnant during the breeding season. Managing body condition so that spring-calving cows are in a body condition score of 5 is critical and impacts rebreeding performance during the next breeding season. Pregnancy rates for mature cows managed for body condition at calving should result in pregnancy rates of at least 90% or greater.
The reason for this discussion is that the equation for calculating breakeven cost equals total costs in the numerator over (weaning weight x percent calf crop weaned) in the denominator.