Body Condition at Calving is Still a Key to Reproductive Success!
We can sub-title this article: “Back to the basics.” Very often in this newsletter or other beef cow related communications, the term “body condition score” is used. It may be time for a brief refresher about this important management tool. Body condition scoring is a manner of evaluating the fatness and therefore the nutritional status of beef cows. Most small to medium sized ranching operations do not have scales to routinely weigh cattle and determine weight and body condition changes. However, everyone has the capability to visually observe cows from the pickup window or on horseback. Body condition is categorized by a scoring system based on “1” being very emaciated and “9” is extremely obese. Most commercial range cows will be in the middle three scores of 4, 5, and 6.
One of the major constraints in the improvement of reproductive efficiency of beef cows is the duration of the post-calving anestrus period. The “anestrus period” is defined as the days between calving and the return to normal heat cycles. If cows are to maintain a calving interval of 1 year they must conceive within 80 to 85 days after calving. Body condition at calving time determines to a great extent the re-breeding performance of beef cows in the subsequent breeding season. Body condition at calving tends to determine the number of days before the cow returns to heat cycles. Based on research of mature and young cows from several studies, cows that maintained body weight and therefore ample energy reserves before parturition exhibited heat cycles sooner than cows that lost considerable body weight and consequently had poor energy reserves. Therefore cows that returned to heat cycles earlier, had more opportunities for heat cycles and ovaluations during the breeding season and consequently have higher conception rates.
The chart above is a summary of numerous trials illustrating the impact of body condition score at calving on subsequent re-breeding performance in the next 60 to 90 day breeding season.
The bars show the percentage of exposed cows that became pregnant in the next breeding season. The white lines aside the bars illustrate the variation in the rebreeding performance in the trials utilized in the summary. Note a wider range of outcomes in the thinner body condition scores of 4 (or less) and the 5’s compared to the cows that were in body condition 6 or greater. This implies that post-calving influences have a greater impact on rebreeding of thin cows compared to those in body condition score 6.
Below are examples of cows in a body condition score 4, 5, and 6.
Body condition at calving greatly impacts the likelihood that the cow will rebreed in the upcoming breeding season and have another calf on time next year.
