Spring may not seem the right time to be thinking about the virtues of fall calving, but if you live in the tall-fescue zone of the U.S., you should be thinking about it right now. Spring and early summer is when endophyte-infected fescue is at its most toxic level, and when your cows are most likely bred for spring calving.
Let's review what's going on with the cows and the fescue in a spring-calving scenario. We're going to be kind of hard on these cows and make them eat infected tall-fescue hay all winter and then go to infected pastures in the spring. This is the worst-case scenario for a cow-calf producer in the fescue region.
Pregnant cows eating toxic hay over winter will lose body condition right up to calving time. The effect of a declining body condition score (BCS) on the ability of a cow to come back to estrous and rebreed for a 365-day calving interval is well documented. They won't do it with-out extensive supplementation.
As the calves are dropped and pasture begins to grow, the poor girls are sent out on infected pastures. Bulls go in roughly 90 days after the first calf comes and the temperatures are starting to get a little warm, if not downright hot.
Tall-fescue pastures have probably gotten out of control; seedheads are exploding onto the scene by mid-spring. This is the most toxic stage of tall fescue, and you're asking your cows to regain weight, produce milk, come back into estrous and get bred. You're also asking bulls to maintain semen quality in the face of rising heat stress and increasing nutritional stress. This is what we call a lose-lose situation.
Progress made, but…
Granted, most cattlemen in the southern and central U.S. understand endophyte-infected tall fescue a lot better than 20 years ago. We see a lot more legumes and crabgrass interseeded into pastures to dilute the fescue toxicity, we've seen some pastures reseeded to other grass species, we've learned strategic supplementation to keep cows in better condition, and maybe we've even selected for more fescue-tolerant bulls.
We've made a lot of progress, but the endophyte can still rear its ugly head in a spring-calving situation and knock the heck out of conception rates, calf gains and profitability. Bottom line with fescue and spring-calving cows is, you've got the deck stacked against you.
So, why does fall calving make sense with tall fescue?
Location of the endophytic fungus and concentration of toxins in specific plant parts is one big reason. The greatest concentration of toxin is in the seedhead and stems, while the lowest concentration is in the leaf blade. Tall fescue only heads out in the spring, so once that flush of stems and seedheads is gone, toxicity is greatly reduced. In a well-grown stockpiled pasture, the fall forage is mostly leaf blade, and is much lower in ergovaline concentration than the spring forage.
Recent research by Rob Kallenbach at the University of Missouri (UM) shows the ergovaline concentration in stockpiled forage rapidly declines over winter with cold temperatures. Even pasture that starts the winter with fairly high toxicity levels becomes much safer to use by mid-January. In the summertime, the endophyte's effects keeps getting compounded by rising heat and reduced forage availability.
Aggravated heat stress is a primary symptom of fescue toxicity. With spring-calving cows, breeding almost always occurs as temperatures and stress on the cattle are increasing. With fall-calving cows, breeding takes place in late autumn or early winter, thus minimizing the possibility of heat stress. It's a lot easier to maintain tight breeding and calving seasons in the fall than in the spring and summer.
Stretching winter feed
Because tall fescue is such an excellent grass for stockpiling as standing winter pasture, we can actually feed fall-calving cows and calves very economically. If the stockpile is properly grown, it can meet the needs of a lactating cow throughout the winter.
While I was at the UM Forage Systems Research Center, we took fall-calving cows through the entire winter on stockpiled, tall fescue-legume pastures with no supplementation other than salt and minerals. The cows bred at 92% in 45-day seasons and lost less than one BCS unit over winter. Our feed cost for carrying a pair through the winter was under $50.
If you're caught up in summer slump and tough breeding conditions on fescue pastures with your spring-calving herd, take a look at shifting to a fall-calving program. It might be one of the best choices you can make to improve your bottom line.
Jim Gerrish is a grazing management consultant based in May, ID, and former lead pasture researcher at the University of Missouri's Forage Systems Research Center in Linneus. Reach him at 208-876-4067, [email protected], or visit www.americangrazinglands.com.