Effects of supplement or fertiliser on forage quality, and performance of stocker cattle grazing warm-season pastures

Abstract

Crossbred (Bos taurus × Bos indicus) beef steers (BW = 232.8 ± 14.6 kg; n = 90) were used over 3 years to examine the efficacy of N fertiliser compared with feed supplementation on forage quality, and animal production. Each year a new group of steers were weighed (unshrunk), and assigned to graze mixed warm-season perennial pastures (Cynodon dactylon and Paspalum notatum Flugge). Paddocks were randomly assigned to one of three treatments: no fertiliser and no supplement (NONE); supplement of 1.1 kg of dried distillers grains with solubles (DDGS) per steer (DM basis) and no fertiliser (DDGS); or fertiliser (134 kg/ha of N applied in split applications) and no supplement (FERT). Cattle were individually weighed at Days 0, 56, 84, and at Day 126, Day 140, Day 93 for Years 1, 2 and 3, respectively). Data were analysed as a mixed model, treatment being used as a fixed effect, year and block as random effects and pasture as the experimental unit. No differences were noted in BW at any point of the study. Greater total average daily gain (ADG) for the grazing period was noted with FERT and DDGS having greatest ADG compared with NONE. Input costs differed (P = 0.001) among all treatments with FERT having the highest input costs, followed by DDGS and NONE. A tendency (P = 0.11) for lowest return was noted with steers in the FERT group returning the least amount of money. No differences (P > 0.10) were noted in forage biomass (kg/ha) at any point of the study. At Day 56, FERT had least ADF (P = 0.03), greatest (P = 0.01) crude protein, and the greatest (P = 0.01) total digestible nutrients (TDN) compared with DDGS and NONE. At Day 84, similar effects existed with FERT having greater crude protein and TDN compared with DDGS and NONE (P ≤ 0.04). No effects (P > 0.10) existed for the last day of sampling for ADF and TDN, however there was a tendency increase in final crude protein (P = 0.07) associated with FERT and DDGS compared with NONE. Results indicate that similar beef cattle performance might be expected if either DDGS or FERT were used, with FERT increasing forage quality at variable points within the study.