Weaning time and the collection of weaning weight is the last piece of data needed to complete 2012 SPA (standardized performance analysis) production measures. Data in Table 1 below is an example of the primary information and calculations needed. Percent calf crop or weaning percentage is a function of the number of cows exposed for breeding, so for a spring 2012 calf crop, this would be cows exposed in 2011. Weaning weight per cow exposed adjusts weaning weight for all the reproductive and management losses that occur from breeding one season to weaning the next.
A good way to use this information is to compare to previous years data for the same herd or to some benchmark data set. The 2011 CHAPS™ database average shows a percent calf crop of 91, where as the Southwest database (long-term summary; NM, OK, TX) has a value of 79 percent. Weaning weight per cow exposed for the example herd is 378 pounds compared to the benchmark values of 503 and 418 pounds for CHAPS and Southwest, respectively. The example herd has a higher calf death loss than either database and a higher pregnancy loss than the CHAPS average. The percentage values in the top part of Table 2 and calving distribution information are all useful for comparison for the sample herd.
Data shown here can be used in a number of ways. If the example herd wanted to improve calf crop percentage, emphasis could be placed on understanding why cows failed to conceive and/or causes for calf death loss. Information on pregnancy rate, pregnancy loss and calf death loss pin point the timing of losses so that producers know where to consider changes.
Another use of this data would be to estimate the change in management needed to improve pregnancy rate say 3% (i.e. more feed pre-calving). Then determine if the increase in pounds weaned per cow exposed would be sufficient to pay for the management change.
Measuring and monitoring reproductive loses over time is key to finding and correcting problems before they become even bigger problems. The example shown in Table 1 is simplified as some herds would need to adjust the cows exposed number based on females that move in or out of the herd, particularly in a drought year. There are SPA guidelines for doing so and spreadsheet options available to help with calculations. Contact Sandy Johnson for assistance getting started at firstname.lastname@example.org or 785-462-6281 .
Source: Sandy Johnson, livestock specialist