CASE STUDY: Production of silage containing biennial canola and peas for use as forage in a dairy ration

Biodiesel production has increased demand for oilseeds such as canola, which can be grown in crop rotation with wheat and barley. Winter canola, when seeded in spring or early summer, will grow as a biennial crop that allows for a forage crop to be harvested in yr 1. The aim of this experiment was to evaluate biennial canola as a dryland forage for silage production and to incorporate the silage into a TMR for lactating cattle. A mixture of peas (113 kg/ha) and canola (5 kg/ha) was planted in early July, and 70 d later the standing forage was cut and ensiled into an air-tight plastic silo bag. The harvested forage contained 31% DM and yielded about 5,391 kg of DM/ha. The ensiled canola-pea forage contained 13.3% CP, 29.8% NDF, 24.1% ADF, 38.6% NFC, 0.31% S, 6.92% lactic acid, 1.97% acetic acid, and no detectable butyric acid and had a pH of 4.3. The nitrate-N concentration in the preensiled forage (139 mg/kg nitrate-N) was reduced about 80% (28 mg/kg nitrate-N) in the ensilage; the nitrate presumably was converted to nitrous oxide and emitted. The estimated NEl value of the canola-pea silage was 1.56 Mcal/kg (DM basis). A feeding study was conducted using 36 multiparous Holstein cows in which cows were group fed either a control TMR or a TMR that contained 9% canola-pea silage (DM basis). In the TMR, the canola-pea silage replaced a portion of the alfalfa hay and corn silage such that CP and NDF percentages were similar between treatments. After 21 d the canola-pea silage was increased to 15% (DM basis) of the TMR. Neither daily milk yield nor milk composition was affected (P > 0.05) by the partial substitution of canola-pea silage for alfalfa hay and corn silage in the TMR. The intercrop of canola and peas yielded an ensilage that was palatable in a TMR and had good feeding value as indicated by the chemical composition, in vitro digestibility, and results of the feeding study with lactating cows. Thus, biennial forage canola appears to be a viable option in crop rotation systems in dryland areas to diversify crop production and obtain forage for ruminants.