Winter Hangover
All parts of the Commonwealth have experienced more winter weather (snow & cold) than we are accustomed to. The snowfall depth and persistent ground cover have provided challenges to both man and bovine in supplying and consuming winter feed.
As we optimistically look ahead to milder weather and spring calving be prepared to deal with and counter the impact of a winter hangover or the carryover effects of this past winter. The most visible impact of the winter would be the body condition score of cows (BCS). Cow BCS at calving is one of the tools that has been shown to be a better measurement of cow condition and reproductive performance than weight. Cows and heifers in thin body condition at calving time are slower to rebreed, produce less colostrum, and may not have sufficient nutrient reserves for maximum milk production.
Prolonged periods of cold weather in many areas has increased the amount of energy intake being directed toward maintenance and away from body reserves and fetal development. Table 1 contains the impact of hair coat on the lower critical temperature where a cow will need additional energy for maintenance. Table 2 displays the amount of additional hay or grain to make up the difference.
| Table 1. Estimated Lower Critical Temperatures for Beef Cattle | |
| Coat Description | Critical Temperature |
| Wet or summer coat | 59 °F |
| Dry fall coat | 45 °F |
| Dry winter coat | 32 °F |
| Dry heavy winter coat | 18 °F |
Table 2. Effect of Temperature on Energy Needs a | |||
Effective | % Increase | Amount of Extra Hay Needed | or Extra Grain Needed |
50 F | 0 | 0 | 0 |
30 °F | 0 | 0 | 0 |
10 °F | 20 | 3.5 - 4 | 2 -2.5 |
-10 °F | 40 | 7 - 8 | 4- 5 |
| a Assumes a dry winter coat, Marston et al (1998) | |||
While the majority of this type of weather may be a memory, understanding these relationships should provide some explanation of your cow herd’s current body condition as they exit winter and begin spring calving. The relationship between BCS and reproductive performance are well documented. The following table relates cow condition at calving to post-partum return to estrus and conception rate. While the majority of our spring calving cows are too far along to change condition score, it clearly shows that nutrition will be critical to assuring a timely return to estrus and maintaining your current average calving date.
| Table 3. Effect of Body Condition at Calving on Postpartum Interval and Conception Rate | ||
Body Condition Score* | Postpartum Interval (days) | Conception Rate (%) |
3.5-4.0 | 88.5 | 70 |
4.5 | 69.7 | 80 |
5.0 | 59.4 | 94 |
5.5-6.0 | 51.7 | 100 |
6.5 | 30.6 | 100 |
| * Condition scores converted to 1-9 system. Houghton,P.L. et.al. 1990 | ||
Producers also need to be on their guard for other possible winter hangover effects in calving thin cows. Spring calving cows which receive inadequate nutrition and lose body condition during the winter months tend to produce less colostrum of lower quality which results in weaker calves that are more susceptible to disease. Additionally, cows calving in thin body condition are likely to produce lighter weight, weaker calves.
Bottom-line is that it has been a tough winter in Virginia; to avoid a disappointing spring calving season, evaluate the body condition of your cows and make the necessary nutritional adjustments. The BCS system is relatively easy to learn and can be implemented in any farm situation. The Virginia Cooperative Extension publication Body Condition Scoring Beef Cows can be picked up at your local Extension office or on the web (http://pubs.ext.vt.edu/400/400-795/400-795.html#L4).
Rights
Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Publisher
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Alan L. Grant, Dean, College of Agriculture and Life Sciences; Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Jewel E. Hairston, Administrator,1890 Extension Program, Virginia State, Petersburg.
Date
March 3, 2010