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Comparing Three Forage Types for Use in Swath Grazing: Effects on Cow Performance, Ruminal Fermentation, and Digestibility

B.W. Neville1, G.P. Lardy1, P.E. Nyren2 and K.K. Sedivec1

1Department of Animal and Range Sciences, North Dakota State University, Fargo, ND, and 2Central Grasslands Research Extension Center, Streeter, ND.


This paper reports findings from two studies. The objective of the first study was to evaluate cow performance in a swath grazing system on three different forages. The objective of the second study was to determine intake, ruminal fermentation, and digestibility of the treatment forages. A year-by-treatment interaction occurred for average daily gain (ADG) and body condition score (BCS) change. No differences were found in 2005, but cows grazing foxtail millet had lower ADG and lower BCS change in 2006. However, foxtail millet had greater intake rates and increased digestibility compared to other forages.

Summary

The objective of the first study was to evaluate cow performance in a swath grazing system on three different forages: crested wheatgrass (Agropyron cristatum), big bluestem (Andropogon gerardii), and foxtail millet (Setaria italica), in a split plot design. Grazed native range was the control treatment. The objective of the second study was to determine intake, ruminal fermentation, and digestibility of these forages in a 5 x 5 Latin square design. For each of the swath grazing treatments, non-irrigated pasture (30 acres) was divided into three paddocks (10 acres each). Three native range pastures (40 acres each) were used as the non-swath-grazed control. A cooked molasses block supplement was included with the big bluestem due to the low crude protein (CP) content of the forage. Cow performance was similar between treatments in 2005; however, swath grazed big bluestem and crested wheatgrass cows increased in BCS, while cows grazing foxtail millet maintained body condition (BC) in 2006.

In the second study, foxtail millet-fed steers consumed more dry matter (DM) and organic matter (OM) compared to big bluestem, crested wheatgrass, and native range-fed steers. Total tract OM, neutral detergent fiber (NDF), and acid detergent fiber (ADF) digestibilities were greater in foxtail millet compared to the other forages. Therefore, we conclude that swath grazing is an acceptable alternative to grazing native range for wintering beef cows in south-central North Dakota.

Introduction

Many comparisons of swath grazing versus baled-forage feeding have been completed with varying results (Turner and Angell, 1987; Munson et al., 1999; Volesky et al., 2002). However, to our knowledge no direct comparison of a cool-season perennial, a warm-season perennial, and a warm-season annual exists in published literature. Volesky et al. (2002) reported calves swath grazing windrows on sub-irrigated meadows had greater weight gains than bale-fed calves in the first year of a two-year study. However, in the second year, the two groups had similar gains. Schleicher et al. (2001) reported windrow-fed cows on flood-irrigated meadows were 32 lbs heavier and had a greater BCS than bale-fed cows. Turner and Angell (1987) reported similar results in a study that compared hay-fed, standing forage-fed, and rake bunch-fed cows on flood-irrigated meadow. In their study, rake bunch-fed cows were 22 lbs heavier than the hay-fed group at the conclusion of the study. Munson et al. (1999) detected no differences in weight gain or BCS when heifers grazed windrowed foxtail millet compared to bale-fed foxtail millet. In contrast, Nayigihugu et al. (2002) reported cows grazing standing corn forage had greater ADG than cows grazing windrowed corn forage. Turner and Angell (1987) reported cows grazing standing flood-irrigated meadow maintained weight but had lower BCS then bale- or windrow-fed cows.

Materials and Methods

All animal care and handling procedures were approved by the NDSU Institutional Animal Care and Use Committee prior to the initiation of these studies, which were conducted at NDSU’s Central Grasslands Research Extension Center (CGREC), six miles northwest of Streeter, ND.

Study 1. One-hundred-forty-four beef cows (2005) and 102 beef cows (2006) were used in a split plot design. Cows grazed one of four treatments: 1) grazed native range; 2) swath grazed crested wheatgrass (Agropyron cristatum); 3) swath grazed big bluestem (Andropogon gerardii); or 4) swath grazed foxtail millet (Setaria italica). All swath grazing treatment pastures were contiguous and the native range treatment pastures were one mile south on similar soil types. Grazing occurred from 19 October through 15 December 2005 and from 17 October through 1 December 2006. Two-day individual body weights (BW) and body condition scores (BCS) were taken at the beginning and end of the trial.

Swath grazing treatment pastures were swathed on approximately 15 September of each year. The crested wheatgrass and big bluestem pastures were first cut with a sickle mower then raked into windrows. The foxtail millet pasture was swathed using a hay conditioner. Each treatment pasture, except native range, was divided into three, 10 ac paddocks using electric fence, providing three (10 ac) replications for each swath grazing treatment. Electric cross fencing was used to limit access in an attempt to increase forage utilization and decrease waste. Nine to 10 days of forage was provided at each fence move. The first area grazed was immediately adjacent to a water source, and cross fences were moved to allow access to water and previously grazed areas. Native range treatment groups were allowed to graze an entire pasture to simulate a typical fall-winter management scenario. The supplement for big bluestem treatment consisted of a 40% CP cooked molasses block (Ridley, Inc., Mankato, MN). All treatments were provided with trace mineral salt blocks (Cutler-Magner Co., Duluth, MN) on an ad libitum basis.

Stocking rates were determined at swathing and were based on estimated forage production. Estimated forage production was multiplied by an 80% harvesting efficiency and an 80% swath utilization. Sub-samples of crested wheatgrass, big bluestem, and foxtail millet swaths were collected for analysis. Swath samples were taken as random grab samples on each day cross fences were moved. Forage samples from native range were collected by clipping 0.25m2 plots on each day the cross fence was moved.

Study 2. Five ruminally and duodenally cannulated beef steers (1166 + 71 lbs) were used in a 5 x 5 Latin square design to determine intake and digestion of forages from a companion swath grazing study. Treatments were 1) big bluestem; 2) big bluestem with protein supplement; 3) crested wheatgrass; 4) foxtail millet; and 5) native range. Steers were offered ad libitum access to the treatment forages, and for supplemented big bluestem, a protein supplement (40% CP cooked molasses block; Hubbard Feeds Inc., Mankato MN) was offered (0.16% BW). All forages were harvested from the swath grazing trial pastures except for native range forage, which was harvested from a site with typical mixed-grass prairie plant species at the same time the swath grazed forages were baled. Total fecal collections and orts were collected for seven days to obtain intake and total tract digestibility data.

Results and Discussion

Study 1. Crude protein content of foxtail millet and native range both decreased quadratically throughout the grazing season (P = 0.04 and P = 0.03, respectively; Table 1). However, big bluestem and crested wheatgrass CP content did not change during the grazing season. A year-by-treatment interaction (P < 0.001) was observed for ADG. Cattle grazing big bluestem gained less weight (P ≤ 0.07; Table 2) than cattle grazing native range in 2006. However, crested wheatgrass and native range were similar (P = 0.32). Cattle grazing foxtail millet lost weight (P < 0.001). Cattle grazing big bluestem and crested wheatgrass had no change in BW (ADG = 0 lb/day; P = 0.46) in 2005, but gained (P < 0.01) weight (0.7 and 0.9 lb/day) in 2006. Average daily gain of cows grazing swathed foxtail millet decreased from (0.2 lb/day) in 2005 to (-1.3 lb/day) in 2006. Cattle grazing native range gained weight in 2005 (0.2 lb/day) and 2006 (1.1 lb/day). There was a year-by-treatment interaction for change in BCS (P = 0.04). In 2005, there was no difference in BCS change (P = 0.12). However, in 2006 cows grazing foxtail millet lost BCS while cows grazing the other treatments increased in BC but did not differ from one another.


Table 1. Crude protein content (%, DM basis) of swathed big bluestem, crested wheatgrass, and foxtail millet compared to standing native range at CGREC in Streeter, ND 2006.

 

Treatment1

 

P-value2

Day

BBS

CWG

FM

NR

SE

Trt

1

8.02a

13.69 b

12.64 b

11.32 b

1.24

0.02

8

7.01 a

14.60 b

9.32 c

  7.97 ac

0.81

<0.001

16

8.86 a

15.45 b

9.23 a

8.54 a

1.29

0.005

24

7.71 a

14.28 b

9.24 c

 8.16 ac

0.57

<0.001

31

7.91 a

12.97 b

7.92 a

7.68 a

0.53

<0.001

37

7.16 a

14.16 b

8.53 a

8.32 a

0.94

0.001

SE

0.65

0.78

0.70

0.66

   

P-value (date)

0.45

0.40

0.01

0.03

   

Linear

0.63

0.59

0.002

0.01

   

Quadratic

0.40

0.34

0.04

0.03

   

Cubic

0.52

0.11

0.28

0.22

   

a,b,c Means within row having differing superscripts differ P < 0.10.

1 Treatment abbreviations BBS = big bluestem, CWG = crested wheatgrass, FM = foxtail millet, and NR = native range.

2 P < 0.10 are considered significant.

 

Table 2. Average daily gain and change in body condition score of cows under swath grazing and native range grazing management at CGREC in Streeter, ND in 2005 and 2006.

Treatment1

P-value2

Item

BBS

CWG

FM

NR

SE

Trt

Yr x Trt

2005 ADG, lbs/d

0.0

0.0

0.2

0.2

0.20

0.46

<0.001

2006 ADG, lbs/d

  0.7 a

  0.9 ab

-1.3 c

1.1 b

0.24

<0.001

SE

1.3

0.2

0.1

0.2

P-value (Year)

0.12

0.12

0.02

  0.10

2005 ABCS

0.2

0.0

0.0

-0.1

0.12

0.12

0.04

2006 ABCS

  0.5 a

  0.7 a

  0.1 b

   0.7 a

0.21

0.05

SE

0.14

0.13

0.05

0.12

P-value (Year)

0.27

0.11

0.53

0.01

a,b,c Means within row having differing superscripts differ P < 0.10.

1 Treatment abbreviations BBS = big bluestem, CWG = crested wheatgrass, FM = foxtail millet, and NR = native range.

2 P < 0.10 are considered significant.

 

Study 2. Dry matter intake was less for cattle fed big bluestem (P 0.06; Table 3) compared to cattle fed supplemented big bluestem, foxtail millet, or native range. Total tract organic matter (OM) digestibility was greater (P 0.006) for foxtail millet than for all other forages. Total tract crude protein (CP) digestibility was lowest (P 0.09) for big bluestem; however, big bluestem was similar (P = 0.19) to native range. Total tract neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibilities were similar for big bluestem, supplemented big bluestem, crested wheatgrass, and native range. However, total tract NDF and ADF digestibilities of foxtail millet were greater than for the other forages tested.

 

Table 3. Intake and total tract digestion of swathed big bluestem, crested wheatgrass, and foxtail millet compared to native range forage.

Treatment1

P-value2

Item3

BBS

BBS/S

CWG

FM

NR

SE

Trt

DMI, lb/d

11.2a

16.7 b

13.2 ac

20.2 d

15.0 bc

1.3

<0.001

OMI, lb/d

10.1 a

15.2 b

12.5 ab

18.7 c

13.6 b

1.1

<0.001

CPI, lb/d

0.5 a

1.1 b

0.9 bc

1.7 d

0.8 c

0.1

<0.001

ADFI, lb/d

4.6 a

6.6 ab

6.6 ab

9.5 b

6.4 ab

1.1

0.03

NDFI, lb/d

8.1 a

11.4 b

9.7 ab

14.1 c

10.6 ab

0.7

<0.001

TTOMD, %

48.6 a

51.4 a

48.1 a

66.5 b

52.4 a

4.2

<0.001

TTCPD, %

26.5 a

43.9 bc

43.1 bc

58.2 c

40.5 ab

6.0

0.003

TTADFD, %

45.5 a

46.2 a

43.7 a

66.9 b

47.9 a

5.6

0.004

TTNDFD, %

48.2 a

49.2 a

45.7 a

66.8 b

50.6 a

5.1

0.001

1Treatment abbreviations BBS = big bluestem, BBS/S = big bluestem with supplement, CWG = crested wheatgrass, FM = foxtail millet, and NR = native range.

2 Significance P-value 0.10.

3 Abbreviations DMI = dry matter intake, OMI = organic matter intake, CPI = crude protein intake, ADFI = acid detergent fiber intake, NDFI = neutral detergent fiber intake, TTOMD = total tract organic matter digestibility, TTCPD = total tract crude protein digestibility, TTADFD = total tract acid detergent fiber digestibility, TTNDFD = total tract neutral detergent fiber digestibility.

a,b,c Means within row having differing superscripts differ P < 0.10.

Implications

Swath grazing is a viable option for producers to winter beef cows in south-central North Dakota. Attention should be paid to forage quality at the initiation of grazing. There are intake and digestibility advantages to using annual forages. If forage quality is too low to support maintenance of cows, supplementation may be required and will directly affect the overall economic feasibility of this type of management.

Present Progress

Cattle grazing turnips on the creep grazing study at CGREC in 2007.

Cattle grazing turnips on the creep grazing study at CGREC in 2007.

A new study was implemented in 2007 to evaluate livestock performance and economic feasibility of grazing annual forages in a standing crop program. Three treatments were implemented on the same land base and compared with a native range treatment. Treatments included foxtail millet, turnips, and a cafeteria mix (foxtail millet, turnips, sunflower, soybeans, cow peas, and forage radish). The annuals were seeded July 13, with a planned grazing season of 15 October to 15 December using a limit grazing strategy. The new study is ongoing.


Literature Cited

Munson, C. L., J. C. Whittier, D. N. Schutz, and R. L. Anderson. 1999. Reducing annual cow cost by grazing windrowed millet. Prof. Anim. Sci. 15:40-45.

Nayigihugu, V., B. W. Hess, D. W. Koch, and J. W. Flake. 2002. Effect of windrow grazing versus baled hay on forage quality and animal performance. Proc. West. Sect. Amer. Soc. Anim. Sci. 53:366-369.

Schleicher, A. D., B. W. Hess, D. W. Koch, J. W. Flake, and L. J. Held. 2001. Windrow grazing versus feeding baled hay. Univ. Wyoming, Agric. Exp. Sta. Prog. Rep. 55-83.

Turner, H. A., and R. F. Angell. 1987. Systems for reducing dependency on harvested forage for wintering cows. Proc. West. Sect. Amer. Soc. Anim. Sci. 38:197-200.

Volesky, J. D., D. C. Adams, and R. T. Clark. 2002. Windrow grazing and baled-hay feeding strategies for wintering calves. J. Range Manag. 55:23-32.


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