Agricultural Research Service

Northwest Irrigation & Soils Research Laboratory

Revised May 2002

Clues on Cues Used by Grazing Ruminants

by

H.F. (Hank) Mayland and Others

We have conducted a series of soil-plant-animal studies on the etiology of grass tetany, a magnesium deficiency in ruminants. One study led to the development of 'HiMag' tall fescue grass (Festuca arundinacea) which offers a greatly reduced risk of causing grass tetany in grazing animals compared with other tall fescues. During the process of evaluating forage quality of HiMag, we obtained information on animal preference among eight tall fescue cultivars. This led us to study chemical and physical components that relate to grazing ruminant preference and possibly serve as Cues to the Grazing Animal. I then wished to assess animal preference for these tall fescue varieties when cut and fed as hay. Since it was necessary to cut the fescue cultivars over a period of time, I was concerned how cutting time might have affected sugar levels and in turn affected animal preference. Details on diurnal cycling of total nonstructural carbohydrates and their affect on animal preference had not been documented. Studying animal responses to diurnal changes in forage quality has been most rewarding. Technical reports and a brief summary of results are given below for each of these studies.

Mayland, H.F. and D.A. Sleper. 1993. Developing a Tall Fescue for Reduced Grass Tetany Risk. p. 1096. In: Proc. XVII Intl' Grassland Congress. 8-21 February 1993. Palmerston North, New Zealand. HiMag contained 18% more Mg and Ca than its Kentucky-31 and Missouri-96 parents. Authors expect about 75% reduction in grass tetany risk when cattle graze HiMag compared with other varieties.

Crawford, R.J. Jr., M.D. Massie, D.A. Sleper, and H.F. Mayland. 1998. Use of an experimental high-magnesium tall fescue to reduce grass tetany in cattle. J. Prod. Agric. 11:409-410, 491-496. Cows, cow-calf pairs and steers grazed four endophyte-free tall fescues, including HiMag, in southwestern Missouri. HiMag contained 22% more Mg than other cultivars. Blood serum Mg was higher in animals grazing HiMag than for those grazing other varieties. Authors suggested that HiMag, compared with other cultivars, would pose a greatly reduced risk of causing grass tetany.

Sleper, D.A., H.F. Mayland, R.J. Crawford, Jr., G.E. Shewmaker, and M.D. Massie. 2002. Registration of 'HiMag' tall fescue germplasm. Crop Sci. 42:318-319. 2002. HiMag tall fescue (Festuca arundinacea Schreb.) is a forage type selected for increased calcium and magnesium uptake and reduced grass tetany risk to grazing animals. It is tolerant of both acid and alkaline soils and foliage contains about 20% more calcium and magnesium than other varieties. The foliage and cured hay have average to mid-high palatability to livestock. Blood serum magnesium levels are higher for some classes of animals grazing HiMag than other fescue varieties. We conclude that HiMag is a good germplasm source for altering certain mineral concentration in tall fescue. Small quantities of seed are available from D.A. Sleper, Dept Agron. Univ. Missouri-Columbia, MO 65211.

Grazing Preference -- Experimental Design:

The experiment, to test grazing preference, consisted of four pastures, each of which contained three replicates of eight plant cultivars in a randomized complete block design. Pasture 4 was used at the beginning of each grazing trial to condition animals and experimenters to the test pastures and procedures. Pastures 1, 2, and 3 were used to test cattle preference. Each plot (cultivar) was composed of six rows 56 cm apart and 6.7 m long, having an area of 22.5 m². Grasses were seeded in rows to facilitate irrigation and utilization scoring. Findings from this study were reported in:

Shewmaker, G.E., H.F. Mayland, and S.B. Hansen. 1997. Border Effects on Cattle Grazing Preference. In: B;.R. Christie (Chm). Proc. XVIII Int'l Grassland Congress 8-19 June 1997., Winnipeg, Manitoba and Saskatoon, Saskatchewan. CD-ROM. We found that grazing cattle require 2-m border on plots to avoid confusion by visuals or aromas of different cultivars on adjacent plots.

Shewmaker, G.E., H.F. Mayland, and S.B. Hansen. 1995. Determining Animal Preference for Grasses: Methods and Error Analysis. Proc. V Int'l. Rangeland Congress. p. 508. 223-28 July 1995. Salt Lake City, Utah. Three methods 1) clipping and weighing before and after grazing (CW), 2) selection ratio (SR), and 3) preference score (PS) were compared. SR was the utilization of given cultivar relative to total forage available as calculated from clipped forage mass. PS was visually determined with score of 0 to 10, where 0 = no evidence of grazing, 10 = all available forage eaten. The coefficients of variation were 96, 52, and 20% for SR, CW, and PS methods, respectively. The ranking of preference was similar for CW, SR, and PS methods. The PS method was done in 6% of the time and with less error than CW and SR and was non destructive.

Grazing Preference Study:

Shewmaker, G.E., H.F. Mayland, and S.B. Hansen. 1997. Cattle Grazing Preference Among Eight Endophyte-Free Tall Fescue Cultivars. Agron. J. 89:695-701. Over four grazing periods and two years, the order of heifer cattle preference for tall fescue varieties was Kenhy > KY- 31 > HiMag = Barcel = C-1 = Stargrazer > MO96 = Mozark.

Relationship of Chemical and Physical Cues to Grazing Preferences:

Mayland, H.F., R.A. Flath, and G.E. Shewmaker. 1997. Volatiles from fresh and air-dried vegetative tissues of tall fescue (Festuca arundinacea Schreb.): Relationship to cattle preference. J. Agric.Food Chem. 45:2204-2210. Fresh forage contained 50 identifiable volatile compounds, three of which accounted for 97% of the variability in grazing preference.

Mayland, H.F., P.H. Harrison, G.E. Shewmaker, and N.J. Chatterton. 2000. Nonstructural Carbohydrates in Tall Fescue Cultivars: Relationship to Animal Preference. Agron. J. 92:1203-1206. Grazing cattle preferred those tall fescue cultivars containing the highest concentrations of soluble sugars.

Mayland, H.F., S.A. Martin, J. Lee, and G.E. Shewmaker. 2000. Malate, Citrate, and Amino Acids in Tall Fescue Cultivars: Relationship to Animal Preference. Agron. J. 92:206-210. Malate and citrate concentrations were not different among varieties. Eighteen amino acids acounted for 75% of total N. Total N concentration was used as covariate in the ANOVA. Kenhy contained higher concentrations of eight amino acids than other cultivars. Neither malate, citrate, nor amino acid concentrations in tall fescue cultivars were related to animal grazing preference.

Shewmaker, G.E, H.F. Mayland, C.A. Roberts, P.A. Harrison, and D.A. Sleper. Daily carbohydrate accumulations in tall fescue accessions. Submit to Agron. J. Concentrations of TNC increased linearly from approximately 7am to 7pm. TNC accumulation rates were the same for the 8 cultivars, but the intercept values were different. The most preferred cultivar had the highest concentration of TNC and the least preferred cultivar had the lowest concentration of TNC. A sampling period of <1 hr was suggested to maintain experimental error <5%.

Burns, J.C., H.F. Mayland, and D.S. Fisher. 1998. Preference by Sheep and Goats Among Hay of Eight Tall Fescue Cultivars. Preference ranking of eight tall fescue cultivar hays was similar to ranking of cultivars when grazed by cattle.

Mayland, et al. Fiber, Crude Protein, and Agronomic Characteristics in Tall Fescue Cultivars: Relationship to Animal Preference. In preparation

MacAdams, J. and H.F. Mayland. The relationship of leaf strength to animal preference in tall fescue cultivars. Submitted to Agron. J. Preference decreased as shear strength increased.

Mayland, H.F., R.A. Flath. J. Roitman, D.S. Fisher, J.C. Burns. 1999. Forage volatiles as cues for ruminants. Satellite Symposium: Emerging techniques for studying the nutrition of free ranging berbivores. Hugh Dove and S.W. Coleman (Ed.) April 10-11, 1999 San Antonio, TX (CD-ROM). Grazing preference was positively related to methyl-5-hepten-2-one and negatively related to (Z)-3-hexenyl propionate and acetic acid. This 3-factor multiple regression had an r-2 =0.97 and P>0.002. If verified in future testing trials, plant breeders could include some of these aromatics in their selection program while animal nutritionists might add them directlly to feed rations to affect dry matter intake.

Diurnal Cycling in Forage Quality

Sundown (PM) Versus Sunup (AM) Cutting of Forages

On 5 August 1996, Mayland was interpreting soluble-carbohydrate data measured in the 'Grazing Preference Study' noted above and reconciling them with published values. A check of literature available at the lab and a call to J.C. Burns, Raliegh, NC showed a general increase in sugars during the daylight hours and a suggested diurnal cycling of sugars in the plant. No information was found then about effects of diurnal cycling of sugars on grazing behavior or animal choices of variously cut hays. An experimental protocol was developed to evaluate animal response to sundown- (PM) versus sunup- (AM) harvested hay. Vegetatively growing HiMag tall fescue was harvested on a PM/AM schedule 20-22 Aug. and 20-21 Sept. 1996 at Kimberly, Idaho. Hay was field cured, baled, and trucked to Raleigh, NC where it was fed in a preference trial. Results from that first study, summarized below, were very exciting and led to other studies evaluating the potential application of this technology. As information becomes available it will be presented in technical meetings and publications, as news releases and by word of mouth. *It is very important that the PM-harvest occur the night before the AM-harvest so that both have the same conditions for sugar accumulation.*

PM/AM- Cut Tall Fescue Grass

Fisher, D.S., H.F. Mayland, and J.C. Burns. 1999. Variation in Ruminants' Preference for Tall Fescue Hays Cut Either at Sundown or at Sunup. J. Anim. Sci. 77:762-768. Cattle, Sheep, and Goats all showed a strong preference for the PM-cut hay, sometimes eating 50% more of the PM hay. This preference, indicated by dry matter intake, was associated with greater total nonstructural carbohydrate (TNC) concentrations. The TNC's accumulated during the day, diluting acid detergent fiber (ADF), and neutral detergent fiber (NDF).

Table 1.  Effect of sundown versus sunup harvests of HiMag tall fescue (endophyte-free) hay on forage quality and dry matter intake during one meal per day by steers.  Data are from D.S. Fisher, J.C. Burns, and H.F. Mayland, USDA-ARS, Raleigh, NC and Kimberly, ID.

PM/AM- Cut Alfalfa

Fisher, D.S., H.F. Mayland, and J.C. Burns. 2002. Variation in ruminants' preference for alfalfa hay cut either at sundown or sunup. Crop Sci. 42:231-237.

Like with the tall fescue, alfalfa was grown in 1997 near Kimberly, Idaho swathed on PM/AM schedule, baled, and shipped to Raleigh, NC where it was fed in 'preference' study to cattle, sheep, and goats. Hays were offered alone as meals to each animal during an adaptation phase prior to the experimental phase. In the experimental phase, each possible pair of hays (15 pairs) was presented to sheep and goats for approximately 2.5 h and to cattle for approximately 0.5 h Presentation of the pairs was randomized. In all three harvests in the three experiments, preference for PM hays was greater than for AM hays (p<.01). Shifting the mowing of alfalfa hay from morning to late afternoon was effective in increasing forage preference in these three ruminant species.

Table 2.  Effect of sundown versus sunup harvests of Germain WL 322HQ hay on forage quality and dry matter intake during one meal per day by steers.  Data are from D.S. Fisher, J.C. Burns, and H.F. Mayland, USDA-ARS, Raleigh, NC and Kimberly, ID.

PM/AM- Cut C-4 Switchgrass (Panicum virgatum L.)

Fisher, D.S., J.C. Burns, and H.F. Mayland. 1999. Diurnal Harvest Timing and Ruminant Preference for Switchgrass Hay. Am. Soc. Agron., annual meeting Oct - 5 Nov. 1999, Salt Lake City. Sheep preferred but goat varied in preference for PM vs AM-harvested switchgrass hays. This response was attributed to greater variability among the harvest treatments. This may be a climatic or genetic response.

Production Response Keyed to Diurnal Cyling of Forage Quality

Dairy Cows will eat about 8% more of a total mixed ration (TMR) containing 40% afternoon-cut alfalfa hay than one containing morning-cut alfalfa hay and will produce about 8% more milk. Adjusting schedules to cut hay in afternoon and early evening can increase feed value of hay by 15%. Kim D. 1995. Effect of plant maturity, cutting, growth stage, and harvesting time on forage quality. Ph.D. Diss. USU, Logan, UT.

Green-chopped alfalfa cut in the afternoon will have more feed value and is relished more by cows than if cut in the morning (Mayland, observation).

When making silage from alfalfa or clover hay, one can enhance the fermentation process by cutting the hay in the afternoon compared to cutting in the morning. Owens, V.N., et al. 1999. Protein degradation and fermenation characteristics of red clover and alfalfa silage harvested with varying levels of total nonstructural carbohydrates. Crop Sci. 39:1873-1880.

Orr, R.J., S.M. Rutter, P.D. Penning, and A.J. Rook. 2001. Matching grass supply to grazing patterns for dairy cows. Grass and Forage Sci. 56:352-361. Dairy cows foraging pastures under 24-h strip grazing management produced 8% more milk when fence was moved after the afternoon milking (4pm) vs after early morning milking (6am).

Increased sugars in afternoon forage may explain increased bite counts in afternoon vs. morning grazing. Mayland, H.F., J.W. MacAdam, G.E. Shewmaker, R.J. Orr, A.J. Rook, P.A. Harrison, and N.J. Chatterton. Total nonstructural carbohydrate in tall fescue leaves and sheaths after light and dark exposure. Consider J. Grass and Forage Sci.

Documenting Diurnal Cycling in Forage Quality

Daily cycling of forage quality, especially as it affects animal eating behavior and economic value, has not been researched prior to 1995. Plant physiological data on sugar accumulations rarely included entire above ground plant material grown in full canopy in the field. Unequivocal evidence of animal preference for sundown- versus sunup-harvested forage has led us to investigate and document gains and losses of soluble sugars at periodic intervals on 12 or 24-h basis.

Figure 1. Conceptual model of total nonstructural carbohydrates (TNC) as a function of time before harvest and after harvest. Curve A represents TNC level if PM-cut forage was immediately frozen, curve B represents gradual drying of PM-cut forage that would decrease the cut forage's respiration rate, curve C represents AM-cut forage immediately frozen, and curve D represents gradual drying AM-cut forage.

Shewmaker, G.E., H.F. Mayland, C.A. Roberts, P.A. Harrison, and E.A. Sleper. 1999. Carbohydrate Accumulation Rates in Tall Fescue. In preparation. Samples were taken at 2-h intervals, from sunup to sundown, from eight tall fescue cultivars, and four times during the season. Over the time period of 2-h post-sunup until 2-h pre-sundown, total nonstructural carbohydrates (TNC) increased linearly from 222, 212, 127, and 98 g TNC/kg DM in May, July, Aug, and Sept. respectively at rates of 3.2, 2.4, 3.0, and 4.4 g TNC/kg DM / hr. Tall fescue forage samples taken for TNC determination should be taken within a 1-h period for values to be within 5% of mean, otherwise sampling times should be blocked. The linear portion of TNC values were plotted by cultivar against time. The TNC slopes were not different amoung cultivars. Intercepts were different for cultivars and were proportional to animal preference. Kenhy had the highest TNC intercept and highest cattle preference while Mozark had the lowest intercept and preference.

Shewmaker, G.E., H.F. Mayland, J.C. Burns, and D.S. Fisher. 1999. Alfalfa quality and Implications for Testing. Proc. Western Crop Sci. Soc. Annual meeting Powell, WY, 28 - 30 June 1999. Forage samples were taken at 3-h intervals, around the clock for 3 to 5 days prior to swathing of each of 4 cuts of alfalfa. Diurnal variation of carbohydrates (TNC) was detected. In May the TNC increased linearly from about 9am to 9pm at 2.9 g TNC/kg DM/h (coef determination = 0.90). Fresh alfalfa forage samples taken for TNC determination should be taken within an 1-h period for values to be within 5% of mean or sampling times should be blocked.

Scientists Working on Various Phases of Carbohydrate Cycling, Cues, & Forage Quality:

Mayland, H.F. (Hank) USDA-ARS, Kimberly, ID mayland@nwisrl.ars.usda.gov

Burns, Joe C., USDA-ARS, Raliegh, NC jburns@cropserv1.cropsci.ncsu.edu

Burritt, Beth, USU, Logan, UT bethb@cc.usu.edu

Chatterton, N. Jerry, USDA-ARS, Logan, UT njchatt@cc.usu.edu

Crawford, Richard, U.MO, MountVernon,MO crawford@ext.missouri.edu

Dove, Hugh, CSIRO, Canbera, ACT 2101, Australia hugh.dove@pi.csiro.au

Fisher, Dwight.S. USDA-ARS, Watkinsville, GA Dwight_Fisher@scientist.com

Flath, Robert USDA-ARS, Albany, CA, retired raflath@ix.netcom.com

Harrison, Phil USDA-ARS, Logan, UT

Henry, David, CSIRO, Wembly, WA, Australia d.henry@ccmar.csiro.au

Hussein, H. U., UNV, Reno, NV hhussein@agnt1.ag.unr.edu

Kim, Dayoon, Systemic Formulas, Ogden, UT dkim@systemicformulas.com

Lee, Julien, CRI, Grasslands, Palmerston N., NZ leej@agresearch.cri.nz

MacAdam, Jennifer, USU, Logan, UT jenmac@cc.usu.edu

Martin, Scott Univ. GA, Athens, GA scottm@arches.uga.edu

McCaughey, W. Paul Brandon, Mannitoba pmccaughey@em.agr.ca

Owens , Vance, SDSU, Brookings, SD owensv@www.ces.sdstate.edu

Provenza, Fred, USU, Logan, UT stan@cc.usu.edu

Roberts, Craig, Univ. Mo, Columbia, MO roberts@psu.missouri.edu

Roitman, Jim, USDA-ARS, Albany, CA jnr@pw.usda.gov

Rook, Andrew, Inst. Grassland & Environmental Res. Okehampton, Devon, UK EX20 2SD aj.rook@bbsrc.ac.uk

Shewmaker, Glenn, Univ. ID, Twin Falls, ID gshew@uidaho.edu

Sleper, Dave, Univ. MO, Columbia, MO sleperd@missouri.edu

Villalba, Juan, USU, Logan, UT villalba@cc.usu.edu