Evaluation of alfalfa and birdsfoot trefoil under intensive rotational grazing.

M.B. Tomecek, and R.H. Leep

Research Technician and Professor, W.K. Kellogg Biological Station

Justification and Objectives:

Farmers’ interest in the practice of managed intensive rotational grazing (MiG) is due to its lower input costs, lower capital investments, reduced labor requirements, improved quality of family life, and reduced environmental impacts.  Our grazing study attempted to address some of the biological questions associated with MiG.  The objective of our  study was to evaluate the performance of pastures planted with alfalfa and birdsfoot trefoil while being grazed by Holstein steers. 

Methods and Procedures:

Holstein steers were grazed in the legume+grass pastures for the fourth year.  The two legumes being evaluated are Alfagraze alfalfa and Norcen birdsfoot trefoil interseeded with Citadel perennial ryegrass.  Grazing began when the forage was approximately six inches tall.   Additional steers referred to as grazers, were placed in the pastures to keep the forage evenly grazed.  They were removed after the spring flush of growth.  No supplementation other than minerals were given.  Grazer and tester steers were weighed each of two consecutive days when there was insufficient forage to support them.  The experimental design is a randomized complete block with three replications.

Results:

Tester Steer Performance:

	Alfalfa+Grass	Birdsfoot Trefoil+Grass
Initial wt (lb)	514	512
Grazing Days	103	103
Stocking Rate (hd/acre)	1.5	1.4
ADG (lb)	2.3	2.5
total gain/steer (lb)	233	259
total gain/acre (lb)	350	318
deaths due to bloat	0	0
deaths due to pneumonia	0	2

Forage Values:

	Alfalfa+Grass	Birdsfoot Trefoil+Grass
Apr-May Grazing Period (lb/A)	2762.9	1761.3
May-Jun Grazing Period (lb/A)	4983.2	4101.9
Jul-Aug Grazing Period (lb/A)	3592.4	3109.6
Aug-Sep Grazing Period (lb/A)	2231.5	3338.7
Total for Season (tons/A)	6.78	6.16
Stem counts (alfalfa or trefoil) stems/sq ft.	19	10
% alfalfa or birdsfoot trefoil in sward	9	16
% clover in sward	3	3
% grass in sward	86	75
% other in sward	2	6

Precipitation data:

Month	30 year average (inches)	1998 (inches)
January	1.8	3.6
February	1.5	2.1
March	1.9	4.0
April	3.5	4.7
May	3.1	1.4
June	4.1	2.5
July	3.4	4.5
August	3.5	1.9
September	3.0	1.8
October	2.8	2.8
November	2.8	1.8
December	2.4	1.0
Yearly total	34	32

Discussion:

The grazing season for legume pastures in southwestern Michigan is estimated to be 150 days or until there is insufficient forage to support animals.  In 1998, the months of  May, June, August and September had less than half the normal precipitation.  Steers were removed for most of  July and fed corn silage and/or alfalfa hay in nearby pastures.  They were placed back in the legume+grass pastures in August but were removed by the first of September once again due to lack of sufficient forage.  The grazing season ended with a total of 103 grazing days. 

Individual steer performance, as measured by average daily gain and total gain per steer, was greater for those steers in the birdsfoot trefoil+grass pastures.  However, since stocking rates are higher in the alfalfa+grass pastures, these pastures produced more gain per acre.  No deaths due to bloat which wasn’t any concern this year due to the high grass component in the pastures.  Two steers died of pneumonia probably infected on their truck ride to Michigan from one of the southern states where they originated. 

The alfalfa+grass pastures consistently had higher yields throughout the grazing periods with the exception of the last period when trefoil+grass pastues had more forage.   This reflected the seasonal yields where alfalfa+grass pastures produced more forage than birdsfoot trefoil+grass pastures (6.8 T/A  and  6.2 T/A, respectively).  The high percentage of grass (86%) in the alfalfa+grass pastures probably contributes to the higher yields.  The trefoil+grass pastures have a higher ‘other’ component than the alfalfa+grass pastures but clover content is the same for both pastures.  Alfalfa and birdsfoot trefoil plants continue to decline in numbers.  Stem counts for alfalfa in the alfalfa+grass pastures was 19 stem/ft².  In the birdsfoot trefoil+grass pastures, stem counts for birdsfoot trefoil were 10 stems/ft².

After four years of grazing, our research has found that dry matter production and herd gain per acre are greater on the alfalfa+grass  than on birdsfoot trefoil+grass pastures.  Citadel perennial ryegrass continues to persist with little winter kill and by reseeding.  The reduction of  the legume component in these pastures continues.  Ways to increase their percentage of the forage sward will be addressed in the future.  We anticipate grazing the replacement dairy heifers from the Kellogg Dairy for the 1999 season.

Funding

Michigan Agricultural Experiment Station;

USDA Sustainable Agriculture Special Grant: Management Systems for Sustainably Integrating Soil, Plants and Steers.

Michigan Department of  Agriculture Groundwater Stewardship Program