Nutrition Research at Fort Keogh:
The free-roaming animal provides a unique challenge to the researcher attempting to assess plant-animal interactions. Diet diversity, large grazing areas, nutrient costs associated with grazing, and environmental stresses all interact to influence nutrient intake and utilization as well as requirements. Nutritionists working with grazing animals have had to develop unique techniques to assess diet quality and intake under extensive conditions. Researchers at Fort Keogh have taken advantage of the laboratory's unique resources to study the nutrition of cattle under extensive management conditions. This has involved development of new techniques and validation of routine techniques for use under conditions in the Northern Great Plains. Despite the difficulties in this type of research, scientists at Fort Keogh have gained recognition for their evaluation of the nutritional status of grazing cattle. Much of the work has focused on protein and energy supplementation of grazing cattle as well as environmental factors affecting grazing behavior and intake and nutritional factors affecting reproduction of beef cows.
The range cattle nutrition program at Fort Keogh formally began in 1971. However, research into the nutrition of beef cattle and other species of livestock and poultry has taken place at Fort Keogh since its inception as a research station in 1924. Research into nutritional factors involved in optimal production of livestock under Northern Great Plains range conditions, the role of nutrition in regulation of physiological mechanisms, and nutritional factors affecting expression of genetic traits have been important components of Fort Keogh's research program since the 1920's.
Early Studies (1924 - 1970)
Initial nutrition studies included sheep, swine, horses, and turkeys in addition to beef cattle. Many studies were initiated in the 1920's to evaluate local feedstuffs for livestock and poultry production. This included evaluation of alfalfa hay, corn silage, wheatgrass hay, barley, and wheat mill screenings.
Sheep studies included testing the value of feeding grain to ewes on winter range. Corn and cottonseed cake were compared for supplemental winter feeding, and evaluations were made on bone meal for ewe lambs and corn silage and wheat mill screenings as feed sources for fattening lambs.
Corn and barley for swine were first compared in feeding trials on the station in 1925. These studies were conducted with pigs pastured on dry land alfalfa. The effect of these two grain sources on subsequent gains in the feedlot was also evaluated. Studies on the relative value of corn and barley diets for swine continued into the 1980's until the swine research program was moved from Fort Keogh to Bozeman. Other feedstuffs for hogs were tested, including tankage, wheat, safflower meal, and linseed meal.
Little horse nutrition work was conducted at Fort Keogh. However, range forage for growth and maintenance of working horses was examined during the 1920's. In 1926, feed and work records of 46 horses and mules were kept for evaluating the feed cost per horse per day of labor. At that time it required 484 per horse work day. Horses averaged 137 days of work per year.
Turkey studies conducted from 1929 to 1939 included developing rations for maximum growth with low mortality. Fort Keogh was one of the first research stations to publish information on improving the hatchability of turkey eggs. Some of this information was nutritional in nature and was readily adapted by turkey growers and feed companies.
Early nutrition work involving beef cattle included evaluating combinations of alfalfa hay, corn silage, and cottonseed cake for wintering calves; comparing alfalfa and western wheatgrass hays for replacement heifers; and testing the value of supplying protein (cottonseed cake) to beef cows wintering on range.
Beef Cattle Research
Environmental effects on nutritional demands. The struggle with environment and its effect on nutritional demands has always been a topic of interest in the Northern Great Plains. Studies on winter supplementation have shown variable response that is related to the severity of weather conditions. Studies were conducted during the 1970 and 80's on the effect of environment on intake and grazing behavior of cattle. Grazing time, forage intake, and digestibility have been found to be reduced as average daily temperature decreases. This, coupled with an increased energy demand for maintenance, can have profound effects on weight gain and body composition of wintering cows and their response to supplementation.Protein and energy supplementation. The value of protein for wintering beef cows has been a recurring theme in the nutrition research at Fort Keogh, beginning in 1929 and continuing through today. In the winters of 1929 through 1934, protein supplementation for Hereford cows wintered on range was evaluated. Response to protein supplementation depended upon the previous summer's rainfall and the amount of snow cover. In years of good forage with little snow cover, protein supplementation was of no economic benefit although supplemented cows came through the winter in better body condition. In years of poor forage because of summer drought or when heavy snow cover was present, most cows fed cottonseed cake survived the winter on the range while nonsupplemented cows had to be moved to the drylot and fed hay. A similar situation was observed in the mid-1970's when response to winter protein supplement was dependent upon forage quality and availability. Forage intake and digestibility were not affected by either protein or grain supplementation during the first, relatively mild winter. However, during the second winter with heavy snow and extended periods of cold weather, forage intake was increased by feeding soybean meal at a rate of 1.5 lbs/d every 2 to 3 days. Total dry matter digestibility was also increased by feeding protein. Cows fed cracked barley during this period had similar forage intake and total dry matter digestibility to those not fed any supplement but forage digestibility was depressed by grain feeding. Body weight and condition score changes were not affected by either supplement.
A 26% protein soybean meal-barley pellet (1.75 lbs/d) was fed to ruminally cannulated steers with or without a monensin ruminal delivery device to evaluate the effects on intake and digestive function during the winter. Protein supplementation increased ruminal ammonia concentrations and organic matter digestibility while decreasing gastrointestinal tract fill and particulate passage rate. Cattle having a monensin delivery device and receiving additional protein had an even greater particulate passage rate. Forage intake was not affected by either protein or monensin. The increase in forage digestibility is a means to provide added nutrients to cattle grazing winter range.
Studies on the timing, type, and amount of protein have been conducted to more firmly define the conditions under which protein supplementation is most profitable. Alfalfa cubes or cottonseed meal-barley pellets were fed on an equal protein basis and evaluated as a fall/winter protein supplement for pregnant cows. Supplemented cows gained weight and gained or maintained body condition while unsupplemented cows lost weight and condition. Performance among cows fed the 2 supplements was similar.
Supply of specific amino acids may be a means of meeting protein requirements of cattle. The feeding of methionine hydroxy analog (MHA) to beef cows was tested in the early 1970's. Cows fed this amino acid analog at a rate of 15 g/head/d from 30 d before until 60 d after calving produced 1.8 lbs/d more milk with .8% more butterfat than cows not receiving MHA. This translated into increased average daily gain and weaning weight of calves from dams receiving the MHA at 15 g/head/d. Cows receiving 5 g/head/d were intermediate in milk production and butterfat content.
Other studies have shown that while protein supplementation during the winter may improve intake and digestibility of range forage, grain (energy) supplements may lower intake of forage. One study showed that the negative effects that energy supplementation may have on changes in weight and body condition can be lessened by feeding grain on a daily rather than on an alternate day basis.
Level of forage intake was found to affect many ruminal characteristics such as Ph and ammonia concentrations. Liquid dilution rates increased linearly and liquid volume decreased as forage intake increased from 1.4 to 2.4% of body weight. Diet quality and ruminal characteristics of yearling steers were followed throughout 1 growing season. As the season advanced, ruminal ammonia concentrations and fluid dilution rates decreased whereas fluid volume and liquid turnover increased. Volatile fatty acid patterns were more favorable for steer weight gain early in the season. These patterns suggest that protein supplements or buffers may be useful late in the growing season to improve forage digestibility.
A study in which monensin and/or rolled barley were evaluated for their effect on digestive kinetics of steers grazing summer range showed that ruminal propionate concentrations could be increased by either of these means. This could be favorable to weight gain in growing cattle grazing summer range. A study with steers grazing fall pasture showed that the time of day at which an energy supplement was fed had important effects on nutrient intake. Steers fed in the morning (7:30 a.m.) ate less feed and had a lower digestible energy intake than steers fed in the afternoon (1:30 p.m.). This difference was related to the interruption of normal grazing behavior.
A study was conducted to evaluate diets for early weaned calves. Calves were weaned at about 84 days of age and fed free-choice alfalfa hay with either whole barley, rolled barley, or whole oats fed free-choice. The results showed that calves fed barley gained weight at a faster rate (2.1 lbs/d) than those fed oats (1.8 lbs/d). Rolling the barley did not show any real advantage over feeding whole barley (2.2 vs 2.0 lbs/d, respectively) for calves of this age. This study did show that calves that must be weaned from their dams can be raised on commonly available feedstuffs with a minimum input of resources. Mineral nutrition. Interest in the mineral nutrition of cattle first came to light at Fort Keogh during the dry summer of 1934 when cattle were observed to consume over twice as much salt as in the more normal rainfall year of 1933. Subsequent studies showed that annual salt consumption was positively correlated with total May and June precipitation. It was hypothesized that this could be due to leaching of minerals from forages during heavy rainfall. Salt consumption was found to be greatest in August, September, and October. Results showed also that salt consumption was not influenced by stocking rate.
During the late 1940's and early 1950's, grazing studies were being conducted at the Hogback/Lone Pine units, and additional information was gathered on the mineral and vitamin status of the cattle grazing those pastures. Calcium, magnesium, and phosphorus concentrations of the range forage where measured throughout the year and blood samples collected to evaluate mineral status of the cattle grazing the area. In the summary of that study, published in 1959, it was stated: "that, in general, it may be expected that breeding cattle can be run on the range in the Northern Great Plains without protein, vitamin, or mineral supplements with satisfactory productive performance and without developing nutritional deficiencies; provided that the range is not overstocked, and realizing that there may be areas within the plains region in which nutritional deficiencies may occur."
Several changes have occurred since the 1950's that have caused us to reevaluate our previous statements regarding protein and mineral supplementation. First, livestock of the 1950's differ genetically from what we raise today. Cattle have been selected for improved performance and there has been an influx of a variety of breeds into commercial cattle operations in the Northern Great Plains. This may have resulted in larger cattle with different nutritional demands. Many pioneering statements regarding nutritional needs may not suit today's cow. Secondly, our understanding of mineral needs has gone far beyond the macroelements. In recent years, a greater emphasis has been placed on the trace element requirements of livestock. We are currently attempting to evaluate these needs in light of current production practices. Nutrition research techniques for the free-ranging animal. Research into nutritional techniques at Fort Keogh has focused on developing and evaluating research techniques for the grazing animal. During the 1980's, several unique techniques were evaluated. An automated data acquisition system was developed to collect frequent animal weights and water intake measurements without altering behavior of grazing livestock. This has facilitated our studies examining the dynamics of body weight changes in grazing cattle. Surgical techniques for esophageal cannulation of suckling calves and for attachment of esophageal bags to older animals were developed and are routinely in use today. Using these techniques, we have shown that suckling calves select a diet higher in protein and lower in fiber than mature steers through much of the summer. Such findings emphasize the importance of using cannulated cattle similar in age to other experimental animals used in nutrition studies.
Techniques to measure intake, digestibility, and rates of passage were also evaluated throughout this period. Adoption of the most promising techniques has improved the intensity and accuracy of the data we collect today on the role of nutrition in efficiency of production. We have been using a sustained release chromic oxide bolus for much of the recent intake work. The use of this bolus was validated in steers and calves. It was found, however, that some animals must be fitted with fecal bags to obtain a correction factor for the bolus release rate. The role of nutrition in reproduction. A great deal of research has been conducted at Fort Keogh on the effect of nutrition on physiological processes. The effects of energy and protein at various stages of the life cycle have been tested for their effect on pregnancy rates, calving difficulty, and onset of puberty. Studies have ranged from measurement of fall pregnancy rates related to feeding levels before and/or after calving to very detailed studies on the influence of nutrients on the very complex hormonal mechanisms affecting reproduction.
Two studies were conducted to evaluate reproduction in cows grazing seeded pastures compared to native rangeland during the prebreeding and breeding period. In the first study, pastures seeded to either crested wheatgrass-alfalfa or russian wildrye-alfalfa were compared to native range for early spring grazing. Calf crop weaned averaged 8-10 percentage points lower for cows on native range. In the second study, pastures that were evaluated included native range, pastures that had been seeded to crested wheatgrass or russian wildrye, and a pasture that had been contour furrowed and seeded with alfalfa. Grazing began on these pastures from mid-April to the first of May. Reproductive performance, as measured by calving date, time to first estrus, and fall pregnancy rate, was not affected by the use of seeded pastures. Eighty-five percent of the cows were observed in estrus before the breeding season, and fall pregnancy rates were 92.4%. It was concluded from the second study that properly managed native range was adequate for good reproductive performance.
Nutritional studies in support of research on pine needle abortion have included determining the effects of pine needle consumption on digestibility of grass hay. Digestibility of organic matter, protein, and fiber all decreased with increasing amounts of pine needles in the diet. This suggests that pine needle consumption may be detrimental to the overall nutritional status of cattle as well as having abortifacient effects. Nutrition and genetics. To set standards for bull testing in the 1930 and 1940's, studies were conducted on appropriate rations and the length of the feeding period needed to evaluate sires. A discussion was presented in a 1941 Experiment Station Bulletin on the possibility of the effect of both utilization of nutrients (feed efficiency) and/or food intake capacity on differences in growth rate among progeny. An interaction between genetics and nutrition was reported in a 1943 Experiment Station Bulletin when the susceptibility of cattle to bloat was shown to be partially genetic.
The FutureAs we look toward rangeland agriculture in the 21st century, scientists at Fort Keogh continue to contribute to nutritional research through integrated projects at the laboratory and through involvement in cooperative studies with Montana State University and other research institutes. We continue to pursue many of the same problems that were plaguing livestock producers in the 1920's: the value of protein supplementation for wintering cows, the mineral needs of grazing livestock, and the value of local feedstuffs for use in rangeland-based cattle operations. We have made improvements in the efficiency of production over the last 68 years, but we have not found solutions to all our problems. As we continue to make genetic and reproductive progress, the nutritional status of our cattle needs evaluation to ensure that we are providing the nutrients required to meet their optimal potential in their environment.
Range Cattle Nutritionists at Fort Keogh
This Historical Perspective was published as part of the 1993 Field Day Report and has not been updated.
USDA, ARS Fort Keogh Livestock and Range Research Laboratory