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The Cow-Calf Manager

Livestock Update, May 2002

John B. Hall, Extension Animal Scientist, Beef, VA Tech

Right Time for Calving in Virginia - Not Summer

The last few calving seasons have been mild and dry, but several times storms or rapid drops in temperature made for tough conditions. Memories of even worse calving seasons may have producers considering a change in calving season. Then here comes the glossy magazine with the story of how switching to late spring and summer calving results in tremendous benefits for Great Plains beef producers. Sounds good - lower feed costs, more cows breeding back, higher weaning weights - what could be wrong with that? As many of you reminded me in my early years here "Buddy, this is Virginia".

Calving systems need to be regionalized to meet the forage, environment and market aspects of that location. What's right for the Great Plains cattlemen may not be right for Virginia producers. Here are a few reasons why.

  1. Fescue. Fescue is the predominate forage throughout Virginia. Fescue is hardy, drought tolerant and productive. It supplies a majority of the nutrient needs of cow/calf operations in Virginia. As beef producers know, the endophyte or fungus in fescue decreases cow and calf performance. The negative effects of fescue are most evident during the summer and early fall. Strategies to reduce fescue toxicosis include increasing the legume content of the pasture and reducing reliance on fescue during the summer months.

  2. Climate. Although it may seem cold in Virginia sometimes, the climate is really relatively mild year-round. Below zero days and severe blizzards are very rare in the state. Western producers regularly face "calf killing" blizzards and severe cold. For example, in 1996 and 1997 producers in the Great Plains faced several late spring blizzards that came in March and April, the middle of calving season. Losses were 35 to 40% of the entire calf crop on some ranches. These high calf losses are reasons that those producers started looking for a different calving time. Heat stress is more of a problem than cold in Virginia because of the high humidity coupled with high temperatures in the summer.

  3. Forage availability and quality. Peak forage availability for cool season grasses (ie fescue, orchardgrass) are April - June and September - October. Add stockpiled fescue to the mix and forage availability is extended from October - January or February. Forage quality is highest during these periods as well.

  4. Cow and Calf Nutritional needs. Cow nutritional needs are highest from 60 days prior to calving to the end of the breeding season. Calves' nutritional needs continue to increase, as they grow older. In addition, less of the calves' nutrition comes from milk (Figure 1). Also, as calves get bigger and older they can handle feeds of slightly lower quality. So from birth to 4 months of age nutrition is needed to support milk production by the cow. By 5 months of age the calf needs most of its nutrition from pasture.

    Figure 1. Percentage of nutrients needed by the calf supplied by milk or forage from birth to weaning.

  5. Reproductive rates. In the humid Mid-Atlantic and Southern States, reproductive rates of cows decrease during the summer months. High daytime temperatures with little nighttime cooling create heat stress on cattle. Heat stressed cows have decreased pregnancy rates. Fewer pregnancies are principally a result of increased early embryonic mortality, but other problems such as failure in sperm transport or lowered ova quality may be involved. This is especially true on fescue pastures where the effects of the endophyte toxins prevent animals from properly dissipating heat. As a result, body temperatures of 104 to 106° F are not uncommon. Considerable research in both dairy and beef cows indicate these high body temperatures are not compatible with successful reproduction.

    Bulls can also be affected by high temperatures, but heat stress does not influence fertility in bulls until 30 to 60 days after the incident. Heat stress causes abnormalities of the sperm at specific stages of development. Sperm that are earlier or later in their development are not affected. Therefore, heat stressed bulls are fertile for several weeks after heat stress only to have decreased fertility later in the breeding season.

  6. Calf performance. Both forage quality and ambient temperature influence calf performance. High temperatures cause calves to expend energy to keep cool which results in lower gains. In addition, heat stress lowers feed intake. Again, fescue pastures make the problem worse. Not only do the endophyte toxins increase heat stress, but they directly decrease feed intake. As a result, calves grazing fescue during the hot part of the year have reduced gains. As the summer progresses, forage quality decreases with poorest quality and lowest availability in July, August and early September.

  7. Marketing. In Virginia, calf prices are traditionally highest in March, April, and May. Prices are usually lowest in October and November when a glut of calves is on the market. Calving systems, which allow calves to be ready for sale at times of high prices, may increase income. Strategies other than calving season alone will be needed to maximize value per calf. However, remember calf value is a function of price and weight. So calving systems should emphasize maximum calf value not just price. These may include backgrounding, vaccination programs and load-lot groups.

So when is the best time to calve in Virginia? When forage availability and quality, climate, biology of the cow, development of the calf and feed costs are all considered, the traditional calving seasons normally used are the best. Although fescue causes some problems, it is better to manage around the problems than try to do away with our most predominate pasture forage.

For commercial producers, calving in late February, March and early April is the best spring calving season. This system minimizes feed costs by matching early lactating cows to the best forage quality of the year. In addition, cows are bred in May and June before temperatures become extremely hot. Most producers will still have bulls out in July, but by this time most of the cows should be pregnant. Calf performance is good even though gains may be reduced in July and August. By backgrounding the calves until November or December, compensatory weight gain and higher calf prices will off-set any summer slump. Using stockpiled fescue will allow cows to regain body condition before calving and further reduce feed costs.

Fall calving continues to increase in popularity, especially east of the Blue Ridge Mountains. Fall calving cows enter the September to November calving season in excellent body condition. Stockpiled fescue along with mild winters greatly decreases feed costs while providing excellent nutrition for cows and calves. Pregnancy rates appear to be 5 to 10% higher in fall calving herds compared to spring calving herds. Most likely, this is a combination of better precalving nutrition and no heat stress during breeding season. Older calves are ready to utilize spring forage for high rates of gain. Marketing heavy calves in July and early August allows producers with fall calving herds to hit a high point in the market.

Winter calving (December - February) is an option best used by purebred producers. High feed costs for this calving system coupled with poor weather conditions make this a dubious option for commercial producers. For purebred producers, the advantage of having older heavier bulls to sell to commercial producers outweighs the disadvantages. In addition, intensive management and use of higher energy feeds usually associated with purebred operations compensates for the lack of grazable forage and poor weather.

Summer calving is definitely not a option for Virginia. High temperatures and poor forage quality at breeding time result in poor pregnancy rates. In addition, the time of rapid calf growth coincides with times of limited grazable forage. So if you're thinking about delaying breeding this year and moving to late spring or summer calving - DON'T. You'll save yourself a lot of trouble.

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