Performance of a Tetraploid Vs. a Diploid Cultivar of Annual Ryegrass Pastures Under Grazing.

Tetraploid annual ryegrass (Lolium multiflorum Lam.) is expected to have greater digestibility and water soluble carbohydrates than diploids. A 2‑yr study was conducted at Raymond, MS to evaluate the potential of a tetraploid (‘Maximus’) vs. a diploid cultivar (‘Marshall’).  Three stocking rates (SR), 3.75, 5, or 7.5 animals ha^-1, were imposed on the two cultivars in a 3 × 2 factorial of a completely randomized design experiment with two replications. Angus cross-bred heifers (initial BW = 240 kg) were used. In both years of the study, there was no cultivar effect or any interactions (P > 0.10) on ADG or herbage mass (HM).  In Year 1, both ADG (1.22 kg d^-1 at low SR to 0.98 kg d^-1 at high SR) and HM (3.8 Mg ha^-1 at low SR to 2.5 Mg ha^-1 at high SR) had a linear response (P = 0.001) to SR. There was no effect of cultivar (P > 0.10) or SR (P > 0.10) on WSC concentration (150 g kg^-1) or IVTD (775 g kg^‑1). In the second year, there was a trend for a linear response of ADG (1.31 kg d^-1at low SR to 1.08 kg d^-1 at high SR) to SR (P = 0.051). Also, HM (4.4 Mg ha^-1 at low SR to 3.8 Mg ha^-1 at high SR) showed a linear response to SR (P = 0.028).  Contrary to first year results, WSC was different (P = 0.012) between Marshall (117.0 g kg^-1) and Maximus (139.0 g kg^-1) annual ryegrass, but there was no SR effect (P = 0.378). Also, IVTD was different (P = 0.01) between Marshall (671.6 g kg^-1) and Maximus (696.1 g kg^‑1). The results of this study suggest that animal performance and HM were not different between the diploid and tetraploid cultivars but were influenced only by SR.