Close your eyes and envision this — lush, green fields heavy with grass and loaded with nutrition. If that's what you see without closing your eyes, count your blessings. But in areas where drought seems the norm, brown grass blankets miles and miles of pasture. Getting every pound of production possible from marginal fields is essential.
Compared with the $178-$180 it might cost to feed a 500-lb. steer to 700 lbs. over a 70-day period, grazing the steer to the same weight would make a pasture worth $12-$38/acre, depending on the forage quality and rate of gain, says Bruce Carpenter, Texas AgriLife Extension livestock specialist in Fort Stockton.
“The value of gain on grass tracks with the value of gain on feed,” he says. “With higher corn prices, grass is increasing in value as a feedstuff relative to corn. Capturing its value depends on management that assures sustainability of the resource while also allowing grazing animals to maximize voluntary forage intake and digestion.”
It starts with not overstocking to provide good “harvest efficiency,” Carpenter says.
Harvest efficiency is the proportion of the total annual forage production consumed by grazing livestock. But it doesn't quite go with the old adage, “take half, leave half,” he says.
On typical rangeland, one might think that allowing 50% of the total forage ungrazed would maintain rangeland health. Not necessarily.
“Forage disappearance from insects, trampling, weathering and other factors is an ongoing process,” Carpenter says. “That further limits the amount of forage available for grazing. So harvest efficiency by livestock on rangelands can only be about 25-30% under moderate stocking.”
This rangeland usage rate can double, even triple, the effectiveness of rainfall. It not only sustains the forage, but also assures that animals are able to meet their daily dry matter intake requirements, about 2.5% of their body weight.
Getting it digested
While it's important that cattle be able to fill up on forage, they must also be able to digest it. Carpenter says, at a minimum, 7% dietary crude protein (CP) is needed to make sure rumen microbial populations remain high enough to maintain healthy microflora, which promotes forage digestion. If the CP can't be provided by the forage, then a supplement is needed.
“Supplemental protein is required for dry cows when CP in forage is less than 7-8% and below 12% for lactating cows,” Carpenter says. “A sound strategy for optimizing roughage is to assure that animals have a plentiful supply, and if its quality is low, the diet is supplemented by a relatively small amount of high-quality protein feed.”
Too much starch in the ration can detour digestion. “Starch provides energy, like other carbohydrates,” he says. “But unlike cellulose, it forms lactic acid in the rumen. When those levels get too high, rumen pH is altered and microflora populations shift away from roughage digestion and toward starch digestion.
“Since most dietary starch comes from supplemental grain, too much grain in the diet can interfere with effective roughage digestion. A typical grain supplement program should limit the amount to 3 lbs./head/day.”
When grass is in short supply and energy supplements are needed, they should be fed frequently. “Supplements high in grain should be fed daily,” Carpenter says.
Supplements using digestible fiber as an energy source could be delivered less frequently, around three times a week. High-protein supplements of 30% CP or higher can be delivered much less frequently, twice a week or even just once a week.
As an example, for animals that need 0.5 lbs. of supplement protein/head/day, Carpenter says that translates to a daily ration of 1.25 lbs./head/day for a 40% CP supplement and 2.5 lbs. for a 20% cube.
“The 20% cube has relatively more starch than the 40% cube, but relatively less starch than grain,” he says. “It could probably be fed on alternative days at 5 lbs./head, but not any less frequently or in any higher amount.
“The 40% cube could be fed as infrequently as once a week at 8.75 lbs./head without interfering with forage intake. Remember, less frequent feeding encourages better grazing distribution and also lowers labor and equipment costs.”
Timely supplemental feeding includes the time of day it's provided.
“Normal grazing is in early morning,” notes Carpenter. “If you feed supplement then, it disrupts their grazing pattern. So it's best to feed in the middle of the day.
“Also, if you see animals grazing at midday, that often indicates they have to work overtime to meet their dry matter intake requirements and that forage may be in short supply.”
Larry Stalcup is a freelance writer based in Amarillo, TX.
Test your herd's digestive rate
A service offered by Texas A&M University (TAMU) can help producers measure their herd's digestible organic matter and other nutritional factors.
TAMU's Grazingland Animal Nutrition (GAN) Lab allows producers to submit fecal samples for analysis to gauge digestive capabilities. The cost is about $25/analysis.
After registering for the service, participants receive a GAN starter kit, which includes an ice pack and Styrofoam packaging to submit samples. The lab analyzes a representative fecal sample from pastures to determine the quality of the forage.
Using decision-support software, producers can determine if animals are on a positive or negative nutritional plane and the most cost-effective feeding option if supplements are needed. Over time, regular monthly monitoring provides information that brings greater confidence to the nutrition decision-making process.
To learn more, go to http://cnrit.tamu.edu/ganlab/.