Nature, nurture and vegetation management: studies with sheep and goats

Authors: WALKER, JOHN - Texas A&M University; Kronberg, Scott

Submitted to: Animal-The International Journal of Animal Biosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2022
Publication Date: 1/1/2022
Citation: Walker, J.W., Kronberg, S.L. 2022. Nature, nurture and vegetation management: studies with sheep and goats. Animal-The International Journal of Animal Biosciences. 16. Article 100434. https://doi.org/10.1016/j.animal.2021.100434.
DOI: https://doi.org/10.1016/j.animal.2021.100434

Interpretive Summary: Invasive plants are a global problem that have a multibillion-dollar impact in the U.S alone. Many problem plant species such as the noxious weed leafy spurge contain phytotoxins that cause livestock to avoid grazing them and give them a competitive advantage over more palatable plants. Targeted grazing by livestock is an environmentally sustainable and effective method to reduce the abundance of invasive plants. The effectiveness of targeted grazing as a control method is dependent upon animals’ preference for eating a problem plant species and defoliating it relative to common desirable plant species to place the targeted species at a competitive disadvantage (plants compete for nutrients and sunlight). Foraging preferences for plant species are determined by genetic and environmental factors. To enhance the effectiveness of targeted grazing, livestock species such as goats and sheep with the greatest innate preference for the target plant species should be raised in an environment that provides experience grazing the target plant at a young age.

Technical Abstract: Diet selection and preference by grazing animals are determined by genetic and environmental factors (i.e., nature and nurture) that interact and affecting their efficacy for managing vegetation as targeted grazers. The objective of this study was to determine the relative contribution of genetics and environment on diet selection by sheep and goats. We hypothesized that although rearing environment will affect preference for chemically defended plants that the inherent ability to detoxify or eliminate phytotoxins will limit an animal’s preference for chemically defended plants. The effect of rearing environment on the consumption of leafy spurge (Euphorbia esula) by sheep and goats was investigated. Sheep were raised on leafy spurge infested pastures by either their ewe dam (S) or a goat doe (SF) on which they were fostered within 24 hours of birth and parturition of lamb and doe. Does that were fostered on also raised their own goat offspring (G) such that the SF and G animals were raised by the same doe. The effect of rearing environment on consumption of leafy spurge was tested the following growing season by simultaneously grazing all animals on the same leafy spurge infested rangeland and estimating percentage leafy spurge in their diet with either fecal near-infrared spectroscopy (f.NIR) or bite count. Goats consumed more leafy spurge as determined by either f.NIR (62.8%, P<0.06) or bite count (71.9%, P<0.01) than FS (35.2%, 39.3%) or S (10.1%, 18.2%). The FS sheep consumed over twice as much leafy spurge and were numerically intermediate to G and S for leafy spurge consumption but not significantly different from the S sheep, most likely because one of the FS sheep did not eat leafy spurge during the evaluation period. Because leafy spurge is aversive to sheep but not goats, higher leafy spurge consumption by FS sheep is hypothesized to result from inoculation of their rumen microflora with microbes from the does capable of denaturing aversive phytotoxins in leafy spurge (or not making phytotoxins more toxic). The higher consumption of leafy spurge by G compared to FS shows that genetically determined physiological differences influence an animal’s ability to ameliorate phytotoxins and will determine the upper limit of an animal’s preference for a chemically defended plant. It also indicated that in addition to the genome of the animal the genome of an animal’s microbiome, which may be influenced by the mother, can play an important role in diet selection.