Companion Grazing Using Goats and Cattle to Control Leafy Spurge

North Dakota Agricultural Research
North Dakota State University, Fargo, ND 58105

Companion Grazing Using Goats and Cattle to Control Leafy Spurge (continued)

Abstract

Keywords

Introduction

Methodology
and Design

Results and
Discussion

Conclusion/
Implications

References

Project
Background

Results and Discussion
When cattle grazed alone, leafy spurge stem densities did not change (P>0.05) by the end of three years (Table 1.) Leafy spurge stem densities on the GO treatment were reduced 70 % (P<0.05) after three years and were reduced to 3.8 stems/1.0 ft² by 1996. Stem densities were reduced 60 % (P<0.05) after three years and were reduced to 5.3 stems/1.0 ft² by 1996 where cattle and goats grazed together (Table 1). These results are consistent with other research that showed at least two years of goat grazing were needed to reduce leafy spurge stem densities (Sedivec and Maine 1993, Sedivec et al. 1994, Lym et al. 1997).

Table 1. Leafy spurge stem density (stems/1.0 ft²) prior to livestock turnout each year at Camp Grafton South, North Dakota.

Treatment	1993	1994	1995	1996	Percent Reduction²

Cattle Only¹	13^a	12^a	13^a	11^a	16.4^a
Goats Only¹	13^a	9^a	3^b	4^b	70.3^b
Cattle/Goats¹	13^a	10^a	7^b	5^c	59.8^b

¹ Leafy spurge stem densities by treatment followed by the same letter are not different (P>0.05). ² Leafy spurge per cent stem density reduction by treatment followed by the same letter are not different (P>0.05).

Grazing cattle only or cattle and goats together had no influence (P>0.05) on production of leafy spurge by the end of three years (Table 2). However, herbage production of leafy spurge was reduced (P<0.05) from 815 lb/ac to 203 lb/ac or 75 % on the GO treatment. Hanson (1994) observed in a herding practice with angora goats that they consistently sought concentrations of leafy spurge. Goat grazing pressure stresses leafy spurge plant communities, allowing graminoids to compete and utilize soil moisture and nutrients otherwise extracted by the extensive root system of leafy spurge. The results of this study supported other research findings regarding multi-species grazing as a management tool to improve range health (Glimp 1988, Squires 1982). Flowering and seed production of leafy spurge was being controlled, stressing the plant, and clearly exhibited a decrease in percentage of herbage production when goats were present.

Table 2. Annual leafy spurge and graminoid production, and percentage change in production by treatment at Camp Grafton South, North Dakota.

Treatment	Year	Leafy spurge¹(lb/ac)	Percent Reduction²	Graminoids¹(lb/ac)	Percentage Increase²

Cattle only	1993	2,044^a		2,146^a
	1994	1,875^a		2,486^a
	1995	1,467^a	28.2^y	2,938^a	36^y
Goats only	1993	815^a		2,132^a
	1994	675^ab		4,025^b
	1995	203^b	75.1^z	4,390^b	106^z
Cattle/goats	1993	890^a		2,748^a
	1994	687^a		3,880^a
	1995	514^a	42.2^y	3,148^a	14^y

¹ Percentages followed by same letter are not different (P>0.05). ² Percentages with the same letter are not different (P>0.05).

Herbage production of all graminoids in the CO treatment did not change significantly throughout the trial (Table 2). Graminoid production increased (P<0.05) when goats only were present (Table 2). The CO and CG treatments had (P<0.05) lower graminoid production from 1993 to 1995 compared to the GO treatment. The apparent increased herbage production in 1994 compared to 1993 among all treatments may have resulted from above average precipitation during the 1994 growing season and less competition from the stressed leafy spurge community due to angora goat grazing where goats were present. No increase in graminoid production was observed on the CG treatment compared with the CO treatment.

Hanson (1994) reported that leafy spurge accounted for a large portion of the goats' diet throughout the grazing season. In the present experiments there was no (P>0.05) year effect on leafy spurge disappearance within each treatment. Leafy spurge disappearance was greater (P<0.05) on the GO and CG treatments than the CO treatment (Table 3).

Table 3. Disappearance of leafy spurge, graminoid species, and western snowberry on rangeland grazed by cattle only, goats only, and cattle and goats together at Camp Grafton South, (1993-1995).

Species/year	Cattle only¹	Goats only¹	Cattle/ goats¹

Leafy spurge	--Percentage Disappearance--
1993	7.2^a	67.0^a	74.6^a
1994	4.2^a	70.4^a	67.8^a
1995	22.3^a	79.9^a	48.9^b
Mean²	11.2^y	72.4^z	63.7^z
Graminoids
1993	10.1^a	7.5^a	27.8^a
1994	6.4^a	10.4^a	19.3^a
1995	8.7^a	9.3^a	25.4^a
Mean²	8.4^x	9.1^x	24.2^y
Western snowberry
1993	17.5^a	18.9^a	31.2^a
1994	24.5^a	28.0^a	32.1^a
1995	20.0^a	41.8^a	29.2^a
Mean²	20.7^z	29.6^z	30.8^z

¹ No differences (P>0.05) occurred between years for either treatment. ² Means with the same letter are not different (P>0.05)

Angora goats graze leafy spurge by defoliating the stem (Sedivec et al. 1994). In our experiments goat grazing caused reductions in leafy spurge biomass compared to the CO treatment. Greater goat stocking rates appear to stress leafy spurge, although further research is needed to determine the extent of density reduction from various stocking rates over several years.

Lym and Kirby (1987) noted that herbage use by cattle in moderate and high density leafy spurge infestations greatly increased between mid-season and end-of-season samplings. Two major factors contributed to this alteration in grazing behavior. First, concentration of grazing in zero and in low leafy spurge density infestations for much of the grazing season resulted in limited amounts of available herbage, furthermore, leafy spurge begins to senesce in early to mid-September, and after fall frosts, the milky latex begins to disappear from the plant. Observations from Lym and Kirby (1987) indicated that cattle grazed high density leafy spurge-infested sites more readily after senescence. Cattle totally or partially avoided leafy spurge-infested sites, frequently using the non-infested sites (Lym and Kirby 1987).

Our hypothesis was graminoid disappearance on the CG treatment should be greater than the other two treatments. This hypothesis was not rejected, with greater (P<0.05) graminoid use occurring on the CG treatment than on the CO and GO treatments (Table 3).

Leafy spurge contains one or more chemicals that elicit an aversive response in cattle (Kronberg and Walker 1993). Heavy leafy spurge infestations in the CO treatment may have hindered the behavioral response of cattle grazing in heavily infested sites. Graminoid degree of use in leafy spurge infested patches was lowest in the CO treatment.

Diet preference of angora goats has primarily been browse and graminoid species, with lower utilization of broadleaf species or forbs (Bryant et al. 1979, Malechek 1970). Cattle are considered primarily grass eaters (Vallentine 1990). Therefore, it is surprising that the pastures grazed by goats showed similar degree of western snowberry use as the cattle grazed pasture (Table 3). Sedivec et al. (1994) reported excessive utilization of western snowberry by angora goats, with the shrub component reduced by over 85 % after three years of intensive grazing.

No yearly differences (P>0.05) occurred in shrub disappearance within either treatment and no difference (P>0.05) occurred among treatments. Davis et al. (1975) reported only a five per cent overlap in cattle and goat diets on southern Colorado mountain brush range which, consisted of about 50 % grass and 50 % shrubs. The low overlap in diet selection by cattle and goat reported by Davis et al. (1975) indicates a potential doubling of stocking rate compared to single-species grazing; however, the CG treatment in this trial was increased over 50 percent, without testing the upper limit.

Conclusion
Multi-species grazing exploits the complementary aspects of herbivore species while reducing the negative aspects of each by decreasing the impact of selective use of preferred plants and areas (Vallentine 1990). When a plant community is diverse, multi-species grazing can improve plant diversity. This is primarily due to diet selectivity and animal species grazing behavior. An understanding of each species' behavior when utilizing range resources allows maximum potential for animal and plant species. Multi-species grazing using angora goats with cattle reduced leafy spurge density while maintaining similar grass production after three years compared to cattle only grazing and provided more grass utilization.

Using more than one animal species could greatly increase red meat production from a given rangeland acreage containing various plant communities. An increased stocking rate may occur in future years with this grazing management practice. Proper stocking of various animal species promotes a diverse mixture of rangeland vegetation and generally increases vegetative production. This could lead to increased profitability for range managers due to diversification. Control of existing and potential noxious weeds should be realized.

Continued grazing monitoring is needed to evaluate its usefulness in reducing leafy spurge stands and allowing associated plant species to effectively compete. Stocking rates in this study were successful in minimizing leafy spurge flowering and seed production.

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