Nebraska Sandhills subirrigated meadow pastures were used to measure the effects of grazing on forage nutrient content in summer pastures. Non-grazed pastures had greater diet CP content than grazed pastures early in the grazing season. By late July, grazed vs. non-grazed pastures did not differ in diet CP content. Non-grazed pastures had greater in vitro organic matter disappearance compared with grazed pastures from late July through September; however, early summer pastures were not affected. Observed results indicate the greatest differences in nutrient content between grazed and non-grazed meadow pastures occur early and late in the grazing season when the majority of cool-season grass species growth occurs

Jenkins, Karla H.

Judy, Jared V.

Klopfenstein, Terry J.

Musgrave, Jacki A.

Stalker, L. Aaron, Stalker

English

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University of Nebraska - Lincoln
DigitalCommons@University of Nebraska - Lincoln
Nebraska Beef Cattle Reports Animal Science Department
2015
Effects of Grazing on Nebraska Sandhills Meadow
Forage Nutrient Content
Jared V. Judy
University of Nebraska-Lincoln, jjudy2@unl.edu
Jacki A. Musgrave
University of Nebraska-Lincoln, jmusgrave1@unl.edu
L. Aaron Stalker Stalker
University of Nebraska-Lincoln, stalkera@byui.edu
Karla H. Jenkins
University of Nebraska-Lincoln, kjenkins2@unl.edu
Terry J. Klopfenstein
University of Nebraska-Lincoln, tklopfenstein1@unl.edu
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Judy, Jared V.; Musgrave, Jacki A.; Stalker, L. Aaron Stalker; Jenkins, Karla H.; and Klopfenstein, Terry J., "Effects of Grazing on
Nebraska Sandhills Meadow Forage Nutrient Content" (2015). Nebraska Beef Cattle Reports. 828.
http://digitalcommons.unl.edu/animalscinbcr/828
© The Board of Regents of the University of Nebraska.  All rights reserved. 2015 Nebraska Beef Cattle Report  — Page 51 
Effects of Grazing on Nebraska Sandhills Meadow Forage 
Nutrient Content
Jared V. Judy
Jacki A. Musgrave
L. Aaron Stalker
Karla H. Jenkins
Terry J. Klopfenstein1
Summary
 Nebraska Sandhills subirrigated 
meadow pastures were used to measure 
the effects of grazing on forage nutri-
ent content in summer pastures. Non-
grazed pastures had greater diet CP 
content than grazed pastures early in 
the grazing season. By late July, grazed 
vs. non-grazed pastures did not differ in 
diet CP content. Non-grazed pastures 
had greater in vitro organic matter dis-
appearance compared with grazed pas-
tures from late July through September; 
however, early summer pastures were 
not affected. Observed results indicate 
the greatest differences in nutrient con-
tent between grazed and non-grazed 
meadow pastures occur early and late in 
the grazing season when the majority of 
cool-season grass species growth occurs. 
Introduction
Nebraska  Sandhills subirrigated 
meadows are an excellent resource for 
grazing cattle. Most are dominated by 
cool-season grass species which have 
greatest growth during early spring. 
However, as temperatures increase by 
mid-summer, forage quality decreases 
due to increased maturation of the 
plant (1997 Nebraska Beef Cattle 
Report , pp. 3-5). Previous research 
has shown changes in forage nutri-
ent composition throughout the year, 
but how grazing affects the nutrient 
composition of Sandhills subirrigated 
meadows has not been documented. 
Therefore, the objective of this 
research was to determine the differ-
ence in forage quality between grazed 
pastures vs. non-grazed pastures 
and IVOMD using the Tilley and 
Terry method with the modification 
of adding 1 g of urea to the buffer and 
ashing the residue to calculate organic 
matter, then adjusted to in vivo 
values . Results were analyzed using 
the PROC MIXED procedure of SAS 
(SAS Institute , Inc., Cary, N.C.) with 
experimen tal unit being cow. 
Results
Greater CP was observed in non-
grazed pastures on June 17, July 2, 
July 11, July 18, July 26, and Sept. 27 
than grazed pastures (P < 0.10, Table 
1). This suggests less difference in 
protein content during August and 
early September between grazed and 
non-grazed pastures. Non-grazed pas-
tures had greater IVOMD on July 15, 
July 31, Aug. 7, Aug. 22, and Sept. 27 
than grazed pastures (P < 0.10). Non-
grazed pastures tended to be greater 
in IVOMD on June 17 (P = 0.12) and 
Aug. 12 (P = 0.11) than grazed pas-
tures. Non-grazed pastures had lower 
NDF on July 2 (P < 0.10) than grazed 
pastures and tended to be lower on 
June 17 (P = 0.15), July 11 (P = 0.13), 
and July 22 (P = 0.11). No other sta-
tistical differences were observed on 
all other sampling dates for NDF. 
These data suggest grazing, and most 
specifically grazing pressure, have the 
most impact on diet quality both early 
and late in the grazing season when 
the majority of new growth occurs. In 
the previous year of this study, simi-
lar results were observed in that diet 
quality was most affected by grazing 
early in the growing season; however, 
samples were not taken as late in the 
season (2014 Nebraska Beef Cattle 
Report , pp. 50-51). 
 Early in the growing season 
when cattle are first introduced into 
a pasture, they consume the highest 
quality forage available. When the 
in Nebraska Sandhills subirrigated 
meadows.
Procedure
A total of twenty-six subirrigated 
meadow pastures (262 ac ± 114 ac) in 
the Nebraska Sandhills were used. 
The meadow was divided into mul-
tiple pastures to allow rotational graz-
ing. Of the 26 sampled pastures, two 
adjacent pastures were sampled on 
one of 13 dates throughout the 2013 
grazing season: June 17, June 26, July 
2, July 11, July 15, July 18, July 22, 
July 26, July 31, Aug. 7, Aug. 12, Aug. 
22, Sept. 6, or Sept. 27. Of the two 
adjacent pastures sampled each date, 
one pasture was not previously grazed 
during the season (non-grazed), while 
the other pasture had been grazed 
the previous four days. On each sam-
pling date the non-grazed pasture 
was sampled prior to introduction of 
cattle to the pasture and the grazed 
pasture was sampled after the allotted 
grazing had occurred. Grazing pres-
sure ranged from 2.0 to 18.9 animal 
units per ton of available forage (Table 
1). Three esophageally fistulated cows 
were used to sample each pasture on 
each date to determine forage quality. 
Prior to each diet sample collection, 
cows were withheld from feed, but 
not water, for 12 hours, then trans-
ported to pastures where diets were 
to be collected. Cows were fitted with 
solid bottom bags after removal of the 
esophageal plug, and introduced to 
the pasture, then allowed to graze for 
about 20 minutes. 
Samples were separated into a 
liquid and fibrous portion for lab 
analysis. Immediately after separa-
tion, diet samples were frozen and 
stored at -20ºC. Fibrous samples were 
lyophilized, ground to pass a 1-mm 
screen in a Wiley mill. Samples were 
analyzed for CP, NDF content using 
the Van Soest et al., (1991) method, (Continued on next page)
Page 52 — 2015 Nebraska Beef Cattle Report  © The Board of Regents of the University of Nebraska.  All rights reserved.
highest quality forage is consumed, 
cattle consume lower quality forage, 
which creates a change in diet qual-
ity over time independent of change 
in nutrient content of the forage. The 
lower quality forage could result from 
consuming more stem or consum-
ing growth from the previous year. 
With greater grazing pressure, the 
new growth may become less available 
more rapidly, expediting the con-
sumption of old growth. This would 
account for the decline in CP that was 
observed earlier in the growing sea-
son. As the growing season progress-
es, ample forage becomes available 
and grazing pressure may not have 
as great an impact on diet quality, so 
averaging the values of the pastures 
before grazing and after grazing may 
be practical. For example, on July 22 
there was less than 1 percentage unit 
Table 1. CP, NDF, and IVOMD values of masticate samples from Sandhills meadow between non-grazed and grazed pastures.
Date2
CP  NDF IVOMD
Grazing 
Pressure3Non-grazed Grazed SEM1 Non-grazed Grazed SEM1 Non-grazed Grazed SEM1
17-Jun
26-Jun
2-Jul
11-Jul
15-Jul
18-Jul
22-Jul
26-Jul
31-Jul
7-Aug
12-Aug
6-Sep
27-Sep
14.8a
10.2a
16.2a
10.9a
9.6a
8.8a
6.7a
8.3a
8.3a
8.0a
7.9a
8.2a
9.0a
10.5b
9.9a
8.0b
8.9b
7.8a
7.7b
6.5a
6.5b
6.4a
9.1a
8.3a
9.7a
6.7b
0.93
0.38
1.12
0.59
0.60
0.39
0.29
0.34
0.63
0.63
0.41
0.60
0.45
55.1a
67.5a
51.9b
65.9a
68.4a
69.9a
68.9b
67.4a
66.5a
68.9a
64.1a
60.5a
63.3a
63.7a
68.6a
66.4a
76.3a
73.6a
71.6a
75.3a
67.4a
75.3a
66.4a
67.2a
64.7a
67.0a
2.63
2.23
3.04
2.90
1.68
2.98
2.04
1.72
3.03
3.05
3.22
3.07
3.16
68.9a
69.2a
60.0a
62.1a
68.3a
66.3a
64.8a
66.8a
63.7a
65.2a
62.8a
52.3b
61.2a
65.4a
66.3a
64.1a
62.2a
60.9b
67.0a
65.7a
64.6a
55.7b
56.4b
55.2a
61.8a
52.3b
0.94
1.98
2.93
3.03
1.30
1.78
1.49
1.85
1.70
1.74
1.90
2.22
1.62
2.0
7.1
18.9
4.5
2.2
3.9
3.6
2.6
3.0
6.4
3.9
6.1
7.9
a,bDifferent subscript between ungrazed and grazed signifies a significant difference within nutrient analysis with a P-value < 0.10.
1Standard error of the least squares mean.
2Date pasture was sampled using esophageally fistulated cattle.
3Grazing pressure expressed as animal units per ton of available forage.
difference between the grazed and 
the ungrazed pastures TDN averaging 
about 65%, which is relatively high 
and would meet the energy require-
ments of a 1,200 lb cow. However, 
the average of the CP is about 6.6% 
which would result in a supply of 
DIP of about 4.6% which is below the 
required amount of 8.45% DIP. Later 
in the growing season, as regrowth of 
the cool-season grass species occurs 
and higher quality diet may become 
more available, grazing pressure may 
once again impact the duration that 
the new growth is available, and cattle 
are once again forced to eat older 
growth.
It is likely stocking rate plays a 
role in differences in nutrient content 
between grazed and ungrazed 
pastures (2015 Nebraska Beef Cattle 
Report , pp. 48-50). In this study, cattle 
were rotated to new pastures relatively 
quickly, resulting in light stocking 
rates and lower grazing pressures. If 
the same study were to be conducted 
under normal or heavy stocking 
rate conditions, larger differences in 
nutrient content of grazed compared 
with ungrazed pastures would be 
expected. By mid-summer with low 
protein values, supplementation may 
be needed, especially in a May calving 
system. 
1Jared V. Judy, graduate student; Jacki A. 
Musgrave, research technician; L. Aaron Stalker, 
associate professor, University of Nebraska–
Lincoln (UNL) West Central Research and 
Extension Center, North Platte, Neb.; Karla H. 
Jenkins, assistant professor, UNL Panhandle 
Research and Extension Center, Scottsbluff, 
Neb.; Terry Klopfenstein, Professor, UNL 
Department of Animal Science, Lincoln, Neb.


Effects of Grazing on Nebraska Sandhills Meadow Forage Nutrient Content

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Effects of Grazing on Nebraska Sandhills Meadow Forage Nutrient Content

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