Volume 29, 2014 - December Effects of Breed of Sheep and Dietary Onions on Bitterweed (Hymenoxys odorata DC) Toxicity E. S. Campbell1,3, T. R. Whitney2, C. A. Taylor, Jr.1, N. E. Garza1 1 Texas A&M AgriLife Research Center, Sonora, TX 76950 2 Texas A&M AgriLife Research and Extension Center, San Angelo, TX 76901 3 Corresponding author: [email protected] ACKNOWLEDGMENT Partial support for the research was provided by the Texas Food and Fiber Commission/ Texas Department of Agriculture, Austin, TX. Summary isonitrogenous diets consisted of alfalfa elicited a breed effect (P< 0.05) for pellets to provide 32 g DM/kg BW per serum measurements reflective of bitter- Bitterweed (Hymenoxys odorata day. Animals were group-fed onions for a weed toxicity; bilirubin, gamma-glu- DC) toxicity is a major cause of death 10-d preconditioning period, then tamyltransferase (GGT) and AST con- losses in Rambouillet sheep. This study penned and fed individually for study. centrations were greater (P ≤ 0.001) for compared the susceptibility of two Individual onion feeding commenced on DBBs than for Rambouillets. The AST, breeds [Rambouillet and Dorper × Bar- d 0 and continued through d 7. On d 3 of bilirubin, creatinine, GGT, and SUN bados Blackbelly (DBB)], of wool and onion feeding, lambs were dosed with an were clinically high for all treatments, hair sheep lambs to bitterweed toxicosis; aqueous slurry of dried bitterweed (0.25 including controls, indicating acute tox- and the potential for cull onions (Allium percent of BW, DM-basis) daily through icity. Feed refusals did not differ among cepa) to mitigate bitterweed toxicity. d 7. Blood samples were taken on d 3 and treatments or by breed (P> 0.10). In this Onions contain high concentrations of d 8 and analyzed for serum constituents study, dietary onions did not prevent naturally occurring thiols, thus offering indicating onion- or bitterweed-induced pathological changes in serum the opportunity for the introduction of a pathologies, respectively. Dry-matter chemistries following bitterweed dosing, diversionary substrate for the principle intake and percentage of feed refusals and had no influence on feed refusals. toxin, hymenoxyn, in a palatable feed- were measured daily. In response to Both breeds exhibited clinical signs of source. Weanling Rambouillet (n = 12; onion diets, serum urea nitrogen (SUN) bitterweed toxicosis, with DBB sheep LS means ± SE = 22.7 kg ± 1.3 kg BW) decreased linearly (P< 0.001). Concen- exhibiting greater abnormal deviation in and DBB (n = 12; LS means ± SE = 22.5 trations of albumin, aspartate amino- serum chemistries than Rambouillets. kg ± 0.8 kg BW) ram lambs were transferase (AST), glucose, hematocrit assigned randomly to one of four treat- and total serum protein (TSP) were Keywords: Bitterweed, Onions, ments: 0 percent (control), 25 percent, greater in DBB lambs than in Rambouil- Hair Sheep, Dorper, Barbados 50 percent, and 75 percent onions in let lambs (P < 0.01), but remained clin- Blackbelly, Rambouillet, Toxicosis diet (DM basis). The remainder of the ically normal. The bitterweed challenge ©2014, Sheep & Goat Research Journal Sheep & Goat Research Journal, Volume 29, 2014 - December 28 Introduction unpalatability (Calhoun et al., 1986) Animals and particle chemistry (Poage et al., Weaned Rambouillet (n = 12; LS Noxious plants increase financial 2000). mean BW ± SE = 22.7 ± 1.3 kg) and risks of ranching, especially on western Cull-onions are an inexpensive and rangelands. Bitterweed is a noxious Dorper x Barbados (DBB) ram lambs (n commercially available food source for = 12; LS mean BW ± SE = 22.5 ± 0.8 weed common in the semiarid range livestock (Frederickson et al., 1995), areas from southwest Kansas through kg) were used to evaluate if onions have that may be adapted for ruminant vet- potential to reduce bitterweed toxicity central and western Texas into Mexico, erinary therapies. Onions and other Arizona, New Mexico, and southeastern in sheep and if the breeds differed in sus- Allium species contain high concentra- ceptibility. Full-blooded wool sheep California (Kingsbury, 1964). In Texas, tions of naturally occurring thiosulfi- (Rambouillet) were selected, based upon bitterweed has led to a loss in economic nates, to which many medicinal proper- 100 years of breeding for dual-purpose returns from sheep production in the ties have been attributed (Lanzotti, production and survival in West Texas. Edwards Plateau and Trans-Pecos 2006). Feeding cull-onions to bitter- DBB lambs were selected as a viable regions since the early 1900s and has weed-exposed sheep may provide the alternative breed, suited for a low-input contributed to a 50 percent reduction in opportunity to successfully introduce management environment. Lambs sheep production in the region (Ueckert therapeutic thiol compounds in a palat- resulted from cross breeding Dorper et al., 1980; Conner et al., 1988). able feedsource. rams, for meat characteristics (Burke et Historically, West Texas ranchers The objective of this study was to al., 2003), to Barbados Blackbelly ewes, have used the Rambouillet breed of evaluate hair and wool breed lambs’ sus- for parasite resistance (Yazwinski et al., sheep for food and fiber production. In ceptibility to bitterweed. In addition, we 1979, 1980) and fertility (Shelton, 1983; recent years, hair sheep have gained in investigated whether feeding onions at Wildeus, 1997). All lambs were pasture- popularity due to the development of a 25 percent, 50 percent and 75 percent of born to ewes native to the site, removing viable ethnic market for lighter weight lambs’ diets could reduce bitterweed the influence of behavioral conditioning lambs, and shortages of labor and skilled toxicity and whether further research on dietary preferences. All lambs were treated with an anthelmintic prior to the shearers. was warranted. While susceptibility of Rambouillet study. sheep to bitterweed has been studied Feeding Treatments extensively, the effect of bitterweed and Materials and Methods other poisonous plants on hair sheep has All procedures involving animals Lambs were assigned randomly to 1- yet to be evaluated scientifically. Given were approved by the Texas A & M Uni- control and 3-treated groups: 0 percent, the increase in numbers of hair sheep in versity Institutional Agricultural Ani- 25 percent, 50 percent, or 75 percent the United States, it is important to bet- mal Care and Use Committee under pro- onions (percentage of diet calculated on ter understand their tolerance and/or sus- tocol, AUP 2006-179. a DM basis). There were three animals ceptibility to poisonous-plant exposure. per breed fed on each treatment. Lambs Study site were limit-fed to provide a baseline of 32 Research aimed at preventing bit- g DM/kg BW per day over the entire terweed toxicity in sheep has focused on The Barnhart Research Station is trial [100 percent of maintenance supplementation with dietary compo- located (30 57’N, 101 07’W) on the northwest edge of the Edwards Plateau, requirements and slight growth (NRC, nents that can inactivate hymenoxon, a 2007)]. Control animals received a diet sesquiterpene lactone (Kim et al. 1975), Texas. The environment is semi-arid; mean-annual precipitation is 453 mm of 100 percent alfalfa pellets. To provide the principle toxin in bitterweed. Some an isonitrogenous diet across treatment experimental success has been achieved with peak precipitation during May and September. The study site is an open groups, treated animals were supple- with thiol-containing compounds, such savanna dominated by a graminoid mented with alfalfa pellets at a level cal- as L-cysteine (Kim et al., 1974; Rowe et mosaic of tobosa grass [Hilaria mutica culated to provide total dietary protein al., 1980), that provide a diversionary (Buckl.) Benth.] and the shortgrasses, (CP onion + CP alfalfa) isonitrogenous substrate for the toxic alkylating effects curly mesquite [Hilaria belangeri (Steud.) with the control diet. Lambs were pen- of hymenoxon. However, cysteine is Nash] and buffalograss [Buchloe dacty- fed by diet group for a 10-d precondi- unlikely to be used as a viable commer- loides (Nutt.) Engelm.]. The scattered tioning period to incrementally adapt cial antidote to bitterweed poisoning in woody overstory consists of honey animals to the onions before the study sheep due to its cost and instability mesquite (Prosopis glandulosa Torr.; began. (Calhoun et al., 1989). Ethoxyquin Mihlbachler, 1990). Major forb species On August 8, lambs were placed in (Kim et al., 1982) and activated char- include annual broomweed [Xantho- individual feeding pens and fed onions at coal (Dollahite et al., 1973; Poage et al., cephalum dracunculoides (DC.) Nutt.], their specific treatment percentage for 3 2000) also mitigated bitterweed toxicity perennial broomweed [Gutierrezia d to acclimate them to confinement. On in research trials, due to antioxidant sarothae (Prush) Britt. and Rugsby], August 11, d 0 of the study, data collec- activity and non-selective binding, Nutall’s milkvetch [Astragalus nuttallian- tion began. Animals were fed treatment respectively. Field application potential uas (DC.) Nutt.], and bitterweed percentages of onions d 0 to d 7. Lambs of these compounds is limited due to [Hymenoxys odorata (DC.)]. were weighed on d 0, d 3, and d 8. Bitter- 29 Sheep & Goat Research Journal, Volume 29, 2014 - December ©2014, Sheep & Goat Research Journal weed dosing began on d 3 and continued Statistical Analysis serum collection periods during the daily through d 7. Feed refusals were study. As this effect was not treatment- weighed d 1 to d 8 to determine intake. Days 1 to d 3, when lambs were fed (P> 0.10) or breed- (P> 0.10) related, Cull-onions were obtained from onions, were considered period 1 for it will not be discussed further. J&D Produce, Inc. (Deming, N.M.) and analysis. Days 4 to d 8, when lambs were As percentage of onions increased stored at 4° C to maintain freshness. fed onions and challenged with bitter- in Rambouillet and DBB lambs’ diets, Onions were fed fresh, and onion DM weed, were considered period 2.