by Dr. Jimmy T (Gunny) LaBaume
Reasonable goals are: 1) conception rate of 95% in a 60 day breeding season; 2) 75% of cows should calve in the first 20 days of calving; and 3) 90% or more of the cows that are palpated pregnant should wean a calf.
More lies are told about conception rates than anything else in ranching. However, this is likely not intentional but due to the fact that there is no standard way of calculating true reproductive performance. The best measure of reproduction is number of calves weaned per 100 breeding animals. This is called the breeding index and is akin to the reproductive index discussed in Part I but not exactly the same. It is calculated as the sum of:
Breeding Bulls _______
+ Young Bulls _______
+ Mature Cows _______
+ Two-year-old heifers _______
+ Yearling heifers _______
Equals: Total Breeding Animals _______
Number of calves weaned the following year _______ (calves weaned as a result of the previous year’s breeding)
Reproduction Index = Calves Weaned divided by Total Breeding Animals X 100
A breeding animal is defined as any animal kept for breeding purposes. Be honest with yourself, if the animal is kept with the possible intention of breeding, it should be considered a breeding animal. In other words, decide how many heifers are true stockers and call the rest breeding heifers.
What is a good breeding index number? The best (theoretical) is about 73 when heifers are bred to calve at two-years old. If bred to calve at three, that drops to about 55. Most fall between 35 and 60.
Also, there are some other things you need to know for each herd or age group: 1) The number exposed to the bull; Then, of those exposed; What percentage conceived (conception rate); 3) How many calved (calving rate); 4) How many had a calf that was branded (branding rate); and 5) How many weaned a calf (weaning rate).
Divide each of these numbers by the number exposed and multiply by 100 to get the rates.
Furthermore, knowing the percentage of cows that calve each week and how many calve at intervals through the calving period is useful in making decisions on how to reduce the length of the breeding season and in projecting conception rates. There are several ways to determine the time of calving. For example, you can tag the calves with number or color coded tags at regular intervals. Or you can count the number of calves weekly. Or you can estimate at palpation when the cow will calve.
This sounds like a lot of extra work but it is really not all that much, especially when you consider the potential improvement in profits that will make it worthwhile. Furthermore, it is hard because you haven’t done it before. Once you get things are sorted out, a lot less work is needed. It is always the beginning that is the hard part.
After: Parsons, Stanly D. Putting Profit into Ranching
Dr. Jimmy T (Gunny) LaBaume (send him mail) is President & CEO, Land & Livestock International, Inc. providing a complete line of management & consulting services to the range livestock industry.