Intake, digestive parameters and behavior of beef steers on Tanzania grass (Panicum maximum Jacq. cv. Tanzania) pasture, supplemented with energy or protein sources

Author(s)

Ricardo Pereira Manzano

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2002-04-10
• Advisor: Luiz Gustavo Nussio

Abstract

The aim of this study was to evaluate the effect of energy or protein supplementation on the feeding behavior and digestiva parameters of grazing steers, under two forage allowances in the summer. Eight Nelore steers on a rotational system in Tanzania pasture were utilized, under two levels of green dry matter (GDM) residues, obtained after the animais withdrawal (R1 = 1,000 and R2 = 4,000 kg day-1 GDM). Four animais were placed on each one of the post grazing residue. Four sources of supplements (WO - no supplement; CC- 2.24 kg day-1 cracked corn; SFC - 2.24 kg day-1 steam flaked corn; and SBM - 0.7 kg.day-1 soybean meal) were used in a Latin square design. Grazing cycles presented 33 days of rest and 3 days of grazing. There was an increase on grazing and ruminating times (470.63 vs. 354.28 and 408.48 vs. 319.06 minutes day-1, respectively), as well as on forage dry matter intake (P < .05) along with increase on GDM allowances. Time spent resting was increased when reducing dry matter allowance (P < .05). Higher total dry and organic matter intakes were observed for animais receiving supplementation (P < .05). Supplementation reduced rumination time, ruminal pH, acetic: propionic ratio, and increased molar concentration of propionic acid in ruminal fluid (P < .05). Animals managed under lower GDM post grazing residue presented higher VFA total concentration (P < .05). Forage allowance resulted in no significant effects on nutrients digestibility (P > .05), excepting CP. Cracked corn increased fiber digestibility, while steam flaked com stimulated starch digestibility (P<0.05). Supplementation and forage allowance did not alter TDN and parameters of dry matter ruminai degradability (P > .05). Degradability parameters of ADF and NDF fractions were not altered by supplementation (P > .05). GDM post grazing residue influenced insoluble and potentially degradable fractions of ADF and NDF, which were superior for R1 (P < .05); and the fractional rate of NDF degradation was lower for R1 (P < .05). ADF potential degradability was higher for R1 (P < 0.05). Forage allowance, linked to higher post-grazing residue, exerted stronger influence than supplementation on the evaluated parameters. (AU)