Linear regressions accounted for 33-66% of the variation in nutritive components of legumes and broadleaf weeds based on measuring the same components in grass. Legumes contained higher crude protein than grass and broadleaf weeds, while neutral detergent fiber and acid detergent fiber were lower in legumes and broadleaf weeds compared to grass. Total digestible nutrients were similar among all three forage classes. The results suggest implications for predicting animal performance based on botanical pasture composition.

1. Correlating nutritional values of grasses, legumes, and broadleaf weeds
Shockey, W.L. 1; Rayburn, E.B.2; Basden, T 3; Seymore, D.A.4; Smith, B.D.5
1Extension
Agent, West Virginia University, Kingwood, WV, 26537
2Forage Extension Specialist, West Virginia University, Morgantown, WV, 26506
3Nutrient Management Extension Specialist, West Virginia University, Morgantown, WV, 2650
4Extension Agent, West Virginia University, Franklin, WV, 26807
646 5Extension Agent, West Virginia University, Petersburg, WV, 26847
ABSTRACT INTRODUCTION
Most pastures contain grasses (gr), legumes (leg), and Climatic conditions in West Virginia are good for forage growth, CP NDF
broadleaf weeds (blw). Each class of forage has unique which can then be used as feed for ruminant livestock. Most
30 CPleg = 0.73CPgra + 11.40 70
nutritional characteristics both in terms of plant pastures contain grasses, legumes, and broadleaf weeds as primary NDFleg = 0.53NDFgra + 8.02
R2 = 0.44, SDreg = 2.8
composition and animal utilization. In the Appalachian forage species. Each of these forage classes has unique nutritional 60 R2 = 0.33, SDreg = 4.2
25
region, gr are the dominant forage species. The growth characteristics both in terms of plant composition and animal
% NDF, Leg or Blw
stage of most gr, which can give an indication of its utilization. 50
% CP, Leg or Blw
20 Leg Leg
nutritive value, is easily identified. Experiments were
In the Appalachian region of the United States grasses are the 40
conducted to measure the correlation of nutritive 15 Gra Gra
dominant forage species. The readily identifiable growth stage of
components of gr compared to leg and blw at similar 30
grasses can give an indication of its nutritive value. To apply this Blw Blw
stages of re-growth. Sixteen pastures were sampled 10 NDFblw = 0.67NDFgra + 2.83
principle to swards containing mixed classes of forage, experiments 20
between May and November during a three-year period. Linear (Leg) R2 = 0.33, SDreg = 5.3 Linear (Leg)
were conducted to measure the relationship between the nutritive CPblw = 1.10CPgra + 0.19
After clipping, 40 samples were hand-separated 5
components of grasses to legumes and broadleaf weeds at similar R2 = 0.66, SDreg = 2.7 10
according to botanical composition then analyzed for Linear (Blw) Linear (Blw)
stages of re-growth.
crude protein (CP), neutral detergent fiber (NDF), acid 0 0
detergent fiber (ADF), and total digestible nutrients Development of a model that regresses nutritive components of 0 5 10 15 20 25 30 40 50 60 70
(TDN). Correlations between gr and leg or between gr different classes of forage at similar stages of re-growth for a given
% Crude Protein, Gra % NDF, Gra
and blw for each parameter were time and space may provide a way for ranchers and researchers to
CPleg = -0.09CPgr 2 + 3.31CPgr -6.88, R2 = 0.52; predict how the different classes of plants respond to the unique
environmental conditions caused by their particular grazing Figure 1 Figure 2
CPblw = 1.10 CPgr + 0.19, R2 = 0.66; management strategy.
NDFleg = 0.53NDFgr + 8.02, R2 = 0.33;
NDFblw = 0.67NDFgr + 2.83, R2 = 0.33; ADF TDN
ADFleg = 0.89ADFgr – 1.62, R2 = 0.54;
MATERIALS AND METHODS 45
ADFblw = 0.75ADFgra + 7.16
75 TDN = 1.20TDN – 12.50
leg gra
40 R2 = 0.52, SDreg = 3.3 70 R2 = 0.45, SDreg = 3.2
Sixteen pastures which were located on farms in several regions of
ADFblw = 0.75ADFgr + 7.16, R2 = 0.52; 35
% TDN, Leg or Blw
WV were managed to measure effects of weather, fertilizer, and
% ADF, Leg or Blw
65
management strategies on a variety of parameters, including 30 Leg Leg
TDNleg = 1.27TDNgr – 16.31, R2 = 0.45; and 60
botanical composition of the swards. A series of samples was 25
Gra Gra
collected by clipping 1 foot square, randomly selected areas 20
TDNblw = 1.17TDNgr – 11.16, R2 = 0.36. 55 TDNblw = 1.17TDNgra – 11.20
between May and November during a three-year period. Blw Blw
15 R2 = 0.36, SDreg = 3.7
Thirty-three to 66% of the variation in the nutritive ADFleg = 0.89ADFgra – 1.62 50
After clipping, 40 samples were hand-separated according to 10 R2 = 0.54, SDreg = 3.7 Linear (Leg) Linear (Leg)
components in leg and blw was accounted for by
botanical composition as grass (gra), legume (leg), and broadleaf 45
measuring the measurements in gr at the same stage of 5 Linear (Blw) Linear (Blw)
weed (blw). Separated samples were sent to the analytical
re-growth. Results suggest implications for assessing 0 40
laboratories of Dairy One, Cornell, NY and analyzed for crude protein
the nutritive value of pasture swards by analysis of the
(CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and 10 20 30 40 50 55 60 65 70
gr only.
total digestible nutrients (TDN) by Near Infrared Reflective (NIR) % ADF, Gra % TDN, Gra
analysis.
For each parameter, regressions between grasses and legumes and
between grasses and broadleaf weeds were calculated by least
Figure 3 Figure 4
squares regression techniques.
RESULTS AND DISCUSSION
SUMMARY
Linear regressions between grass and legume or between grass and broadleaf weeds for each nutritional component are depicted in figures 1-4.
Linear regressions accounted for 33 to 66% of the variation (with a standard
Legumes contained higher concentrations of CP than both the grasses and broadleaf weeds (Figure 1). It was also noted that changes in the concentration of CP in the
deviation about the regression of 2.7 to 5.3 units) in the nutritive components
grasses were more closely related to changes in the broadleaf weeds compared to legumes.
in legumes and broadleaf weeds by inputting the components in grass over
NDF was lower in both legumes and broadleaf weeds compared to grasses and were positively regressed (Figure 2). ADF levels were lower in legumes compared to grasses the same range of re-growth. These results suggest implications for
and broadleaf weeds (Figure 3). predicting animal performance based on the botanical components of
pasture swards. A larger and more comprehensive database could improve
TDN was similar over the range measured among all the 3 classes of forage (Figure 4). This supports the concept of a similar energy value across all classes of forages with
the precision of regressions between botanical composition and animal
performance parameters being more closely related to intake than utilization. This observation is consistent with the results of Weiss, W.P. and Shockey, W.L. (1992.
performance and provide criteria for pasture managers to maximize forage
Orchardgrass can be a good forage for dairy cows. Hoard's Dairyman, 137(5) , p 204) who noted that the performance of lactating dairy cows was similar for cows
utilization.
consuming orchardgrass vs alfalfa because the NDF was more digestible in the grass compared to the legume.