|Estell, Richard - Rick|
Submitted to: Small Ruminant Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/5/2003
Publication Date: 9/1/2004
Citation: Animut, G., Goetsch, A.L., Estell, R.E., Merkel, R.C., Dawson, L.J., Puchala, R., Sahlu, T. 2004. Effects of methods of exposure to eastern red cedar foliage on cedar consumption by Boer crossbred wether goats. Small Ruminant Research. 54(3):197-212. Interpretive Summary: Invasive shrub species such as Eastern red cedar (Juniperus virginiana) are a problem for livestock producers in many areas in the United States. These shrubs are usually not eaten by livestock, often because they contain noxious chemicals. Proliferation of invasive shrubs results in reduced forage production for livestock and wildlife. Methods of shrub removal are presently costly or inefficient. Browsing by goats may be an alternative to mechanical removal for some shrub species. Goats have been found to consume Eastern red cedar to a limited extent, depending on stocking rate, season and availability of other forage. Exposure of ruminants to unpalatable plants, particularly at a young age, may increase consumption later in life. The objective of this study was to examine the effectiveness of two methods of exposure on later intake of Eastern red cedar by goats (gradual, stepwise increase in exposure compared to a constant amount in the diet). Boer goats were fed a mixed diet containing Eastern red cedar introduced either at a constant level (25% of diet) for 8 weeks or in incremental increases (0, 1.25, 2.5, 5, 10, 15, 20, and 25% of diet) during the same timeframe. Goats were placed on pasture for 6 weeks then fed diets containing 25% red cedar for 2 weeks, either with or without free choice hay. Cedar intake was greater for the stepwise than for the constant treatment when no hay was offered. When hay was offered, cedar intake was not different regardless of phase 1 treatment and was not different than the stepwise treatment without hay. No negative effects on growth rate or health were observed due to consumption of cedar at 25% of diet for up to 8 weeks. Gradual introduction of unpalatable shrubs into the diet of goats may be a mechanism to increase future consumption of undesirable plant species.
Technical Abstract: Twenty-four crossbred Boer yearling wethers (23.5 ± 2.31 kg initial BW) were used to determine effects of stepwise increases in dietary level of Eastern red cedar (Juniperus virginiana) foliage (CF), compared with a constant relatively high level and subsequent availability of low-quality forage, on present and later consumption of CF. Animals were penned individually in Phases 1 (8 wk) and 3 (2 wk), and during Phase 2 (6 wk) wethers were kept in a pasture not containing cedar trees and were fed wheat hay. In Phase 1, a concentrate-based diet (CBD, 12.6% CP and 35.5% NDF) was offered at approximately 85% of the maintenance energy requirement alone (Control) or with weekly stepwise (Step) increases in level of substitution of CF for CBD (0, 1.25, 2.5, 5, 10, 15, 20, and 25% in wk 1-8, respectively; DM basis) or substitution of 25% CF in wk 2-8 (Set). In Phase 3 (2 wk), all wethers were offered the diet of 75% CBD and 25% CF as previously, without or with separate free-choice access to low-quality grass hay. CF was harvested weekly, refrigerated and hand-mixed with CBD prior to feeding. In Phase 1, intake of CF as a percentage of that offered was greater (P < 0.05) for Step vs. Set in wk 3-8 (wk 3: 86 and 48; wk 4: 89 and 56; wk 5: 90 and 71; wk 6: 96 and 81; wk 7: 93 and 63; wk 8: 96 and 84), although CF intake as g/day was greater (P < 0.05) for Set vs. Step in all but wk 7 and 8. In Phase 3, CBD intake was similar among treatments, and hay intake when offered averaged 149, 134 and 124 g/day for Step, Set and Control, respectively. For wethers not receiving hay, CF intake as g/day for Step was greatest among treatments (P < 0.05) but was not different from treatments with offered hay (67, 37, 30, 55, 53 and 56 g/day for Step, Set and Control without and with hay, respectively; SE = 7.1). Similarly, CF intake as a percentage of that offered ranked (P < 0.05) Step > Set > Control without hay, but was not different between Step without hay and treatments with hay (78, 41, 34, 61, 57 and 60% for Step, Set and Control without and with hay, respectively; SE = 7.6). Concentrations of various blood constituents at the end of Phases 1 and 3 did not indicate adverse health effects of CF consumption. In conclusion, gradual increases in dietary level of CF deserve further research as a potential means to elevate present and future CF consumption with attention also directed to effects of type and level of other feedstuffs offered.