Evaluating Beef Production Parameters Through Backgrounding Steers by Swath-Grazing Monocrop Cereals and a Complex Forage Mixture During Winter in Alberta
Date
2025-06-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0009-0009-2889-7626
Type
Thesis
Degree Level
Masters
Abstract
This 3-yr study was a field assessment of the effects of grazing either (i) a polycrop mixture (PC) comprised of CDC SO1 oat (Avena sativa L.), Golden Globe turnip (Brassica rapa L.), Hunter turnip (Brassica rapa L.), Goliath forage rape (Brassica napus L.) and 4010 forage pea (Pisum sativum L.) or (ii) a monocrop of CDC SO1 oat (OM) on dry matter yield (DM), nutrient composition, soil characterization, forage utilization, estimated DM intake (DMIestimated), beef cattle performance and economics in a winter swath grazing system. A 12-ha field was sub-divided into six, 2-ha paddocks. Each paddock was randomly assigned to 1 of 2 replicated (n=3) forage systems, seeded in June at the seeding rate of 157 kg ha-1 for OM while PC was 45 kg ha-1 (oat), 11 kg ha-1 (forage pea) and 6 kg ha-1 (brassica). Forage systems were sampled at soft dough (SD), hard dough (HD), post-hard dough (PHD), and regrowth (RG) stages. At hard dough stage, forages were swathed into windrows for grazing, except for a 9-m strip in each PC paddock, which was cut approximately 31 d later. Crossbred beef steers (n=42, yr 1; n=60, yr 2; n=54, yr 3; BW=267.4 ± 14.1 kg) were stratified by body weight (BW) and, randomly allocated to forage systems which were grazed for an average of 84 d over the 3 yr study. Soil samples were collected prior to seeding in yr 1 and after grazing in yr three. Effect of maturity stage on DM yield (P = 0.02) showed an additional 1140 kg ha-1 DM of OM at HD compared to soft dough yield. Oat monocrop yielded greater (P < 0.01) DM compared to the PC, regardless of stage of maturity. Deferring swathing of the PC to the PHD stage yielded similar (P = 0.85) DM yield and similar nutritive values compared to SD and HD stages of maturity. No effect of stage of maturity (P = 0.07) or forage system on crude protein content was observed (P = 0.61). Forage systems had an effect (P < 0.05) on NDF, starch, sugar, fat, calcium, phosphorus and sulphur levels. The NDF decreased by 5.9%, starch increased by 36.8%, TDN increased by 2.5%, and sugar decreased by 37.1% as forages matured from SD to HD stage. No difference (P > 0.05) was observed for final BW, ADG, DMIestimated and rib-fat change of steers grazing OM or PC systems. A higher (P = 0.03) residual soil nitrate level was observed in the PC paddocks compared to the OM paddocks. This may suggest a supply of nitrogen generated by the N-fixing pea in the polycrop mixture. No difference (P = 0.38) in swath cost per kg steer gain ($0.56 vs. $0.69 kg⁻¹) of the forages was observed while cost per head per day for PC ($0.45 hd⁻¹ d⁻¹) tended (P = 0.07) to be greater compared to OM ($0.38 hd⁻¹ d⁻¹) system. These results suggest that both OM and PC swathgrazing are cost-effective methods for winter backgrounding weaned steers. However, PC can potentially enhance soil nitrogen.
Description
Keywords
beef cattle, polycrop, winter swath-grazing, forage, dry matter intake
Citation
Degree
Master of Science (M.Sc.)
Department
Animal and Poultry Science
Program
Animal Science