245 The influence of deferment and season of use on beef cattle diet quality and composition following a rangeland wildfire

• Published in: Journal of animal science 2024-09, Vol.102 (Supplement_3), p.363-364
• Main Authors: Kluth, Janessa A, Davis, Noah G, Wyffels, Samuel, Marlow, Clayton, Vermeire, Lance, Van Emon, Megan L, Nack, Makae, Sitz, Taylre, Hamilton, Thomas, Peterson, Jeremiah, DelCurto, Timothy
• Format: Article
• Language: English
• ISSN: 0021-8812; 1525-3163
• DOI: 10.1093/jas/skae234.414

Research has shown that forage quality increases after a fire. Greater crude protein content in forage can be beneficial for livestock, and even attract herbivores to recently burned areas. However, there has been little research into how forage quality changes within the first 2 yr after a fire and how it affects livestock diet quality or composition. Therefore, this project was conducted within a burn area of an August 2020 wildfire to evaluate the effect of seasonal deferment and annual rest on diet quality, botanical composition, and foraging efficiency of beef cattle grazing burned rangeland. A randomized complete block design was used comparing June grazing versus September grazing with cow/calf pairs, and no deferment versus a 1 yr deferment of grazing. Sixteen 4-hectare pastures were used, with eight being grazed in 2021 and 2022, and eight only grazed in 2022. Pastures were grazed in either June or September by cow-calf pairs for 2 d at a time. In June, 20 cow/calf pairs were used, and 16 pairs were used in September to account for calf growth/intake. Cattle diet composition and masticate samples were collected during 20-min bite-count periods using six ruminally cannulated cows in each pasture prior to and after 2 d grazing periods. Composition of diets upon pasture entry differed among treatments (P < 0.01) with June diets in greater proportions of forbs than September diets. In addition, June diets with no deferment had greater forb composition than June diets with 1 yr deferment (P < 0.01). Crude protein in June diets were substantially greater than September diets (P < 0.01) and within the June grazing period, greatest for the non-deferred treatment (P < 0.01). June diets had decreased neutral detergent fiber (NDF) concentrations than September diets (P < 0.01) and within the June grazing treatments, the first year after burning was least in NDF content (P < 0.01). There was no difference in ash concentration for all treatments and years (P ≥ 0.07) averaging 16.46% ash content. There was no effect of grazing treatment on grams per bite (P ≥ 0.34) averaging 1.36 grams per bite for pre- and post-grazing treatments. In summary, season of use and timing of grazing following a wildfire has an impact on cattle diet composition and quality with the greatest impact in the spring following a wildfire.