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G. Scaglia, 051 The Effect of Stocking Rate on Steer Performance Grazing ‘Nelson’ Ryegrass, Journal of Animal Science, Volume 95, Issue suppl_1, December 2016, Page 25, https://doi.org/10.2527/ssasas2017.051
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Abstract
‘Nelson’ annual ryegrass (Lolium multiflorum, Lam.) is a tetraploid cultivar developed for high forage production; hence, it may support greater stocking rates than diploid cultivars. Annual ryegrass has proven to be a reliable high nutritive value winter annual forage for stocker cattle in the deep south. On three consecutive years, 78 crossbred steers (272.9 ± 6.2 kg) were weighed and allotted to 4 fixed stocking rates (SR): 3.76 (SR1), 4.51 (SR2), 5.26 (SR3), and 6.01 (SR4) steers per hectare in a complete randomized design with 3 replicates. Steers were weighed and forage data collected on d 0 and every 15 d thereafter. Data were analyzed using PROC REG to determine the effect of SR on the response variables. The correlation between forage allowance (FA) and ADG was determined by a nonlinear minimization procedure using PROC NLP. There was a linear effect (P < 0.0001) of SR on ADG (1.14, 0.98, 0.72, and 0.51 kg), gain/ha (403, 371, 254 and 187 kg/ha), and grazing days (94, 85, 68, and 62 d) for SR1, SR2, SR3, and SR4, respectively; however, steer grazing d-1 was similar (P = 0.68) between treatments (354, 381, 360, and 371 d for SR1, SR2, SR3, and SR4 respectively). Forage mass (2.432, 1.541, 1.091, and 719 kg DM/ha, respectively) linearly decreased (P = 0.002) as SR (SR1 to SR4) increased. By design, FA on d 0 decreased linearly (P = 0.001) across treatments (2.57, 2.26, 1.89, and 1.69 kg DM/kg BW for SR1, SR2, SR3, and SR4, respectively). On average, grazing was terminated when forage height and mass were 7.5 ± 1.5 cm and 800 ± 164 kg DM/ha, respectively. Final FA also decreased linearly (P < 0.01) as SR increased (0.70, 0.52, 0.42 and 0.40 kg DM/kg BW for SR1, SR2, SR3, and SR4, respectively). Average daily gain increased with increasing FA up to 2.1 kg DM/kg BW and remained constant at approximately 0.96 kg when FA was greater than 2.1 kg DM/kg BW. This relationship supports the fact that the major factor affecting gains at high SR was forage mass. Lesser SR allowed for greater ADG and gain/ha although steer grazing d-1 did not differ among SR. Further research comparing diploids and tetraploids cultivars of annual ryegrass is warranted.
