EFFECTS OF NUTRIENT SUPPLEMENTATION IN BEEF-COWS OF POOR BODY CONDITION FED SNAKEWEED (GUTIERREZIA SPP)

Two replicate trials determined the effects of dietary supplementation on snakeweed toxicity in beef cows of poor body condition. Cows were stratified by weight and randomly assigned to 3 dietary treatments. Di etary treatments were control (n 3/trial; medium quality hay, 9.49% cr ude protein), corn supplementation (n = 3/trial; control diet + 628 g cracked corn), and protein supplementation (n 3/trial; control diet 800 g 42% protein supplement). Corn and protein dietary treatments wer e fed to be isocaloric. Each trial consisted of 2 phases (68 days/phas e). Phase 1 consisted of dietary treatments without snakeweed. In phas e 2 dietary treatments contained snakeweed as 10% of the dry matter. P hase 1 and 2 dietary treatments were isocaloric/isonitrogenous. Dry ma tter intake of the control diet was limited to 1.3%, of body weight/d. Body condition score and back fat were measured on days 0, 21 and 68 of each phase. Serum samples were collected at the onset of each trial and on days 28, 42 and 56 of each phase. Serum bromosulphthalein (BSP ) elimination half life (t(1/2)) was estimated during week 6 of each p hase. Serum BSP elimination t(1/2) was higher for the control diet ver sus corn and protein treatments. Increased blood urea nitrogen (BUN) w as found by day 28 of phase 2. Serum total bilirubin increased by day 28 in phase 2 compared to baseline for the control and corn dietary tr eatments. Additionally, serum indirect bilirubin was higher by day 28 in phase 2. Likewise, serum direct bilirubin increased during phase 2 on day 28 in the corn diet, but decreased by day 28 for the protein di et. Alkaline phosphatase levels were higher (p<0.05)in the controls by day 28, but lower in the protein treatment by day 28 in phase 2. Chan ges were noted during phase 2 for some of the serum clinical profiles; however, these changes appear due to dietary restriction. In contrast , changes during phase 2 point to possible hepatotoxic and renal toxic effects of snakeweed. Phase 2 data suggest a benefit of protein suppl ementation for improving animal tolerance to snakeweed.