Winter is around the corner and, hopefully, we have managed the ranch in a manner to avoid high feed costs. The most economical way to feed beef cattle is use of year-round, good quality grazing of warm- and cool-season forage that require little or no supplement.
Quantity of available forage and its nutritive value determine if nutrient supplements are needed in the diet.
The most accurate and time-consuming method of measuring forage quantity is to clip and weigh palatable forage from a representative number of small areas, average the weights, and adjust the total to a per-acre basis. A quicker, yet accurate, method is use of the Natural Resource Conservation Service measuring stick. After one of the two methods is used several times, many people learn to estimate available forage just by walking the pasture.
Grass harvested by grazing while in the vegetative stage normally will rate high in quality. In addition to grazing management, pasture quality depends on geographic location, environmental conditions and types of plants.
“During most of the year, warm-season forages are likely deficient in some minerals,” said Stephen Hammack, Texas A&M AgriLife Extension beef cattle specialist emeritus. “This is especially true with certain trace elements like copper and zinc.”
Jason Banta, Texas A&M AgriLife Extension beef cattle specialist, said, “A high calcium, low phosphorus mineral is usually the best option for the following situations:
• Introduced forage pastures,
• Native grasses in the growing stage
• Dormant native grasses with supplement (cubes, distillers grain, cottonseed meal, etc.).
“When native grasses are dormant and the rancher isn’t feeding supplement, then a mineral with similar levels of calcium and phosphorus is appropriate.”
“Vitamin A is usually low in dry or weathered forages. If a deficiency is expected, give Vitamin A injections to the cattle or feed it in mineral or other supplements. Protein content in forage varies seasonally and in certain times of the year, they are a factor in determining needs for supplements,” Hammack said.
“Warm-season forage typically has a protein deficiency in late summer and again in winter.”
“Most of the energy for grazing cattle comes from rumen digestion of forages and roughage,” said Chris Richards, Oklahoma State University beef cattle extension specialist. “With proper amounts of protein and minerals, the rumen is capable of getting energy from a wide range of feeds.
“If cows are thin, however, additional energy will be required to restore their body condition to a moderate level.
“First- and second-calf heifers require additional energy for growth until they mature at about 4 years of age.”
“The amount of available forage affects need for supplemental feed,” said Ron Gill, Texas A&M AgriLife Extension Service livestock specialist. “If limited supplies of grazing are expected, then consider reducing stocking rates to decrease the amount of needed supplement.
“As forage supply declines, opportunities for animals to selectively graze decrease, and so does diet quality. In these situations, supplementation is often required even after destocking.”
Forage quality is important
An estimate of how much forage and feed an animal will consume is essential when evaluating available grazing days in a pasture or calculating the amount and type of hay and feed needed to meet the animal’s nutrient requirements. Dry matter intake is influenced by an animal’s weight, body condition, reproduction stage and amount of milk production. Intake also depends on forage quality, amount and type of supplement or feed provided and environmental conditions.
“Intake in forage-fed cattle is generally limited by capacity of the digestive tract,” OSU’s Richards said. “Variation in dry matter intake is based on differences in forage quality and stage of production for beef cows.
“Forage digestibility values rarely exceed 70 to 74 percent of the dry matter. Calves and yearlings frequently are fed higher quantities of concentrate feeds to improve weight gain and feed conversion above what can be achieved with forage alone.
“When diet digestibility approaches 70 percent, feed intake is no longer regulated or limited by capacity of the digestive tract.”
“Poor quality forage has less than 6 to 7 percent crude protein and less than 50 percent total digestible nutrients,” said Hammack. “Because both consumption and nutrient content of poor quality forage are low, supplemental needs are high. Medium quality forage (7 to 11 percent crude protein, 50 to 57 percent total digestible nutrients) eliminates or significantly reduces need for supplementation, especially for cows.
“High quality forage (above 12 to 14 percent crude protein and 57 percent total digestible nutrients) is usually consumed in the largest amounts and there is usually no need to feed supplements. An exception is possibly high milk producing cows that are in poor body condition.”
Banta said, “Dry cows normally consume 1.5 to 2.0 percent of their body weight and lactating cows will consume 2.0 to 2.5 percent on a dry matter basis.”
Animal characteristics affecting feed consumption
“Body condition or the amount of fat on an animal is one characteristic that affects supplement needs,” livestock specialist Gill said. “Low body condition markedly increases need for supplemental nutrients. Moderate body condition significantly reduces or eliminates requirements for supplements. Fleshy cows generally need little if any supplement and daily amounts of forage can often be reduced.”
Forage consumption also is related to body size. If sufficient forage exists to satisfy consumption requirements of the larger cows, they may not need more supplement than the smaller cows. Adjustments in stocking rate, to allow adequate amounts of forage per cow, may offset differences in size but will increase maintenance cost per cow. If forage is sparse or limited, larger cows require more supplement.
“Higher milking cows can consume more forage, but not enough to completely satisfy extra needs,” Gill said. “When forage quality is inadequate, higher milking cows need more supplement.
“Young animals are still growing and require extra nutrients, but their body size is not as large as mature animals. Because of their smaller body size, growing heifers cannot consume as much forage as mature cows. For these reasons, young females require higher quality diets than mature cows and often require more and different supplements.”
Balancing the ration
Software programs such as the OSU Cowculator are found on the Web and can be used by producers to help estimate nutrient requirements and supplementation needs for different scenarios.
Banta drafted the following examples where the beef cow diet has been balanced with available resources. In these scenarios, the available resource is hay.
Assume the hay nutrient analysis shows 6 percent crud protein and 53 percent total digestible nutrients. Cattle weights are approximately 1,300 pounds. The cows are dry in late gestation. Their body condition score is okay, but needs to be maintained at the current level.
Cows in this scenario need a diet that contains approximately 8 percent crude protein and 55 percent total digestible nutrients, so supplement is needed to maintain current body condition. Three and a half pounds of a 20 percent protein cube plus 24 pounds of hay are required to meet their needs.
A 13,00-pound cow at peak lactation fed the same hay would require a daily supplement of 5.5 pounds of a 40 percent protein cube. The goal in feeding this cow is to control her weight loss to no more than 1 body condition score in 100 days. A 1,300-pound cow at peak lactation, fed hay containing 9 percent crude protein and 56 percent total digestible nutrients, needs 4.5 pounds of a 20 percent protein cube to control her weight loss to no more than 1 body condition score in 100 days.
These examples show the effects of forage nutrient content, animal body weight and production stage on the needed amount of supplemental feed. A primary opportunity to reduce feed costs is to maintain ample quantity and quality of standing forage in an economical manner.