PS8-7. Swathgrazing Polycrops to Build Cow-Calf Resilience and Profitability in Alberta.

Abstract The cow-calf industry in Alberta accounts for over 40% of Canada’s beef breeding stock; therefore, evaluating factors that improve the sustainability and profitability of the cow-calf sector will positively impact Canada’s economy. Swathgrazing is a management practice in which annual forage crops are cut and left in windrows for livestock to graze during the fall or winter. This study assessed animal performance, mineral supplement intake, and carbon dioxide (CO2) and methane (CH4) emissions from cow-calf pairs. The study was laid out in a randomized complete block design with two treatments and three replicates (6 paddocks in total measuring 12-ha (213.4 x 625 m)). Treatments were either a monocrop system of CDC-SO1 oats (Avena sativa L.) or a polycrop forage system (oats, forage peas (Pisum sativum L.), turnips (Brassica rapa L.), and rape (Brassica napus L.)). Eighteen cow-calf pairs were stratified by body weight, and three pairs were allocated to each paddock of 2-ha and dimensions of 35.6 x 625 m. Animals grazed for 72 days and had ad libitum access to an automatic feeding unit to collect individual mineral intake. Greenhouse gas (GHG) emissions were tracked using a Greenfeed Emissions Monitoring System. Animals were weighed at the start (SOT) and end (EOT) of the trial, and every 21 days during the trial. Backfat ultrasound scans were collected at SOT (day 0) and EOT (day 72) of the trial. Statistical analyses of animal performance, mineral intake, and CO2 and CH4 emissions data were performed using PROC MIXED in SAS. Fixed effects included treatments (oats and polycrops), animal class (calves and cows), and their interaction, with paddock as a random effect in the analyses of mineral intake and GHG emissions. There was a Treatment × Class interaction (P = 0.02) for average daily gain (ADG). The calves gained 0.89 kg/day under the oats monocrop system and 0.92 kg/day under the polycrop system. In contrast, the cows gained 0.33 kg/day under the oats monocrop system and lost 0.09 kg/day under the polycrop system. Pairwise comparisons showed that oats significantly improved ADG in cows compared with polycrop (P = 0.003), whereas no significant difference between treatments was observed in calves (P = 0.83). Mineral intake was influenced by animal class (P = 0.01), with cows consuming more than calves. The GHG emissions were also affected by animal class (P < 0.01). Cows produced more CO2 and CH4 than calves in both treatments. The results showed that calves’ ADG increased regardless of the treatment, and the cows benefited more from oats. There was no difference in GHG emissions between the treatments.