|Estell, Richard - Rick|
Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2008
Publication Date: 2/19/2009
Citation: Utsumi, S.A., Cibils, A.F., Estell, R.E., Soto-Navarro, S.A., Van Leeuwen, D. 2009. Seasonal changes in one seed juniper intake by sheep and goats in relation to dietary protein and plant secondary metabolites. Small Ruminant Research. 81:152-162.
Interpretive Summary: Shrub encroachment on rangelands is a serious problem in arid and semiarid regions throughout the world. Shrubs contain secondary metabolites that negatively affect their consumption by livestock. Amounts of these chemicals in shrubs vary over the season. Supplemental nutrients may reduce the negative effects of secondary chemicals on intake of shrubs such as one-seed juniper by ruminants. Intake of freshly harvested juniper branches was measured for sheep and goats fed either ruminally degradable protein or ruminally undegradable protein supplements and compared to animals fed an unsupplemented control diet during summer, fall, winter, and spring. Juniper intake was greater for goats than sheep, and twice as high for supplemented compared to control animals across season. Juniper intake in the fall, when concentrations of plant secondary metabolites were highest, was 41, 58, and 52% lower than for summer, winter, and spring, respectively. Seasonal variation in secondary chemistry can affect juniper intake by small ruminants. Supplemental protein may increase voluntary intake of one-seed juniper by sheep and goats during seasons when plant secondary metabolite levels are low, but had little effect during the fall when secondary metabolites were high.
Technical Abstract: Seasonal variation in plant secondary metabolites (PSM) can influence voluntary intake levels of one-seed juniper (Juniperus monosperma Englem. Sarg.) of sheep and goats. Supplemental nutrients could mitigate the deterrent effects of juniper PSM. We determined the concentration of mono-and sesqui- terpenes, total phenolics and condensed tannins in one-seed juniper leaves in summer, fall, winter, and spring, and tested their effects on juniper intake of 12 Western White Face ewes (74.9 ± 1.23 kg) and 12 Boer-Spanish does (46.7 ± 1.25 kg) fed isoenergetic diets (1.6% BW) with no supplemental protein (Control, 5% CP) or with addition of a rumen degradable (RDP, 12.5% CP) or undegradable (RUP, 12.5% CP) protein supplement. Animals were fed unrestricted amounts of freshly harvested juniper branches for 30 min and short-term juniper intake was determined for 10 d per season. Total terpenes, total phenolics, and condensed tannins varied across seasons (P<0.05), and were positively correlated to each other (P<0.05). Juniper intake was greater for goats than sheep (P<0.05), and twice as high for supplemented vs. control animals (P<0.05). Juniper intake in the fall, when levels of plant secondary metabolites were highest, was 41, 58, and 52% less than in summer, winter, and spring (P<0.05), respectively. Supplements with RDP and RUP promoted different patterns of juniper intake among seasons (P<0.05), herbivores (P<0.05), and individual animals (P<0.05). This study suggests that supplemental protein can increase voluntary intake of one-seed juniper of small ruminants during seasons when plant secondary metabolite levels are low. Proteins of different degradability appear to affect seasonal patterns of juniper intake differently.