Evaluation of Swath Grazing Simple and Complex Polycrop Mixtures on Forage Biomass and Quality, Beef Cow Performance and Enteric Methane Emissions, System Economics and Soil Health Characteristics

Polycrop mixtures are of increasing interest to western Canadian beef producers as alternative forages for grazing as they may promote soil health, plant biodiversity and nutritive value. A 2-yr grazing study (2022 and 2023 for yr 1 and 2, respectively) was managed at the Livestock and Forage Center of Excellence (LFCE), Forage and Cow-Calf Research and Teaching Unit (FCCRTU) located near Clavet Saskatchewan, located in the Dark Brown soil zone. This 2-yr study evaluated the effects of swath grazing either Simple or Complex polycrop mixtures on forage yield and quality, beef cow performance and intake, methane emissions, soil characteristics and system economics. Forage treatments included (1) CDC Haymaker oat (Avena sativa) (Control); (2) CDC Haymaker oat, Goliath brassica (Brassica napus), hairy vetch (Vicia villosa), CDC Jasper pea (Pisum sativum) (Simple); (3) CDC Haymaker oat, Goliath brassica, hairy vetch, CDC Jasper pea, CDC Maverick barley (Hordeum vulgare), Red proso millet (Panicum miliaceum), Teff grass (Eragrostis tef) and Choice chicory (Cichorium intybus) (Complex). Dry pregnant beef cows (n = 90; BW = 607.2 ± 32.3 kg; BCS = 2.9 ± 0.06) blocked by body weight were randomly allocated to 1 of 9 paddocks (10 cows/paddock). Paddocks were randomly assigned to 1 of 3 replicated (n = 3) systems. Cow body condition score (BCS) was measured at start (SOT) and end (EOT) of trial. Cow body weight (BW) was recorded on 2 consecutive days at the SOT and EOT, and every 21 d during trial. Soil characteristics analyzed included organic carbon, total carbon, total nitrogen, phosphorous, potassium, sulfur, bulk density, pH, electrical conductivity, and root biomass. Over 2 yr, cows grazed for an average of 52 d from October to December (Control 51 ± 9.07 d; Simple 54 ± 9.20 d; Complex 53 ± 12.41 d). Data was analyzed as a completely randomized block design using the MIXED model of SAS (9.4). Year and paddock were included as a random effect. Forage dry matter yield (DMY) was similar (P = 0.44) among Control (4369 kg/ha), Simple (4053 kg/ha), and Complex (4245 kg/ha) treatments. Start of trial forage crude protein (CP), total digestible nutrients (TDN), and cow dry matter intake (DMI) did not differ. Methane emissions were greatest (P = 0.04) for cows grazing Simple (280.0 CH4 g/d) and Complex treatment forages (241.8 CH4 g/d) compared to monoculture oat treatment (167.6 CH4 g/d) in yr 1, while there was no significant differences between treatments in yr 2. Complex mixtures (1.21 mg C/ha) had significantly (P = 0.001) more soil organic carbon at 15-30 cm depth than the Simple (0.90 mg C/ha) and the Control (0.97 mg C/ha). Soil phosphorous was also significantly greater (P = 0.03) in the Complex (2.86 ppm) compared to the Simple (1.06 ppm) and Control (1.97 ppm) at the 15-30 cm depth. Study results suggest that Simple or Complex polycrop mixtures are suitable alternatives to monoculture oat grazing system as they produce adequate biomass and nutritive value suitable for meeting requirements of gestating beef cows. The greater root biomass, although not significant, could have contributed to the added soil carbon observed in the Complex polycrop mixtures. An economic analysis indicated that the cost to grow Simple ($ 709/ha) and Complex ($688/ha) polycrop mixtures was significantly greater (P = 0.01) than the oat monoculture ($ 634/ha). However, total feeding costs did not differ between treatments (P = 0.14).

Name thesis:degree_name

Master of Science (M.Sc.)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Animal Science

Grantor

University of Saskatchewan

Year dc:date.issued

2025

Author dc:creator

• Robinson, Shelby Marie

Advisor dc:contributor.advisor

• Lardner, Herbert (Bart) A

Committee members dc:contributor.committeemember

• Larson, Kathy A
• Ribeiro, Gabriel O
• Drewnoski, Mary E
• Brook, Ryan K

• Annual
• Cover
• Crop

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10388/17673

OAI identifier oai:identifier

oai:harvest.usask.ca:10388/17673