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Putting the Preg Check Results to Work

January 9, 2017

Pregnancy check day is one of the most important days on the ranch as it is the day when we find out what cows are pregnant and how many calves we can expect come calving season. So now that the veterinarian has left the yard and the open cows are sorted off, what’s next? Before throwing the preg check list on the dashboard never to be looked at again, try to reflect on the results. Take some time to sort through them to uncover valuable information such as breeding season management and what to expect for the upcoming calving season.

Analyzing Your Results
First start by finding the following information:

  • Number of cows at the start of breeding season
  • Start and end dates of breeding season
  • Cow death loss, culls, non-breeders

Utilizing pregnancy check results and the above information to determine the following:

Pregnancy Rate (%)
(# of cows diagnosed pregnant / # of cows exposed to breeding) x 100
Pregnancy checking can determine the overall fertility of the cowherd. If pregnancy rate is lower than desired, areas such as type of breeding program and bull-to-cow ratio should be analyzed to pinpoint where adjustments are needed. Also, evaluate pregnancy rates by sorting cows into age groups to see if a certain age group is falling out of the herd, such as 2 year olds or old cows.

Pregnancy Distribution
(number of cows that became pregnant during days 1 – 21 of the breeding season, days 22 – 42, days 43 – 63, days 64 – 84, and 85 or more days after the start of the breeding season)

Analyzing pregnancy distribution can be used as a guide to prepare for the calving season. Not only can the barn be ready by the time the first calf hits the ground, but you can also determine when the majority of the calves will be born, and adjust labor and feed resources accordingly. For example, Figure 1 shows the pregnancy distribution from a cowherd where 66% of cows became bred during the 1st 21 days of the breeding season. The strength of the cowherd in Figure 1 is that over 80% of calves will be born during a 40-day period resulting in a larger, more uniform calf crop to take to market.

Culling Rate (%)
(# of cows died, open or sold / # of cows exposed to breeding) x 100

If a greater than normal cull rate is observed, records can help identify what may have gone wrong. Start by assessing the body condition and health records as poor nutrition or sickness could be reasons for more open cows. Keeping track of culling rate will help determine the number of replacement heifers needed to maintain herd size.

In addition, if bulls become injured early in the season, more cows will likely be bred during the 2nd or 3rd cycle. Reproductive diseases such trichomoniasis (trich) can also be spread if an exposed bull is carrying the disease or if a neighboring bull with trich jumps the fence and joins the herd for a period of time. While cows can clear the infection, bulls remain positive for life and throughout the breeding season and cause loss of pregnancies. Figure 2 shows what the pregnancy distribution may look like if a bull injury went unnoticed or if a herd was exposed to trich during the breeding season.

Records such as pregnancy and cull rates are critical in that they give insight into management areas that affect reproductive and economic success of the herd. Keeping consistent records from year to year will allow benchmarks to be created unique to each herd, which can then be used for comparisons and performance analysis. If cowherd records are sparse, industry averages or benchmarks such as CHAPS can be utilized for initial comparison until more years of records are collected.

Source: Taylor Grussing, South Dakota State University, iGrow