Protein or energy supplementation of growing cattle grazing tropical pastures

Author(s)

Térssio Roger Angelelli Ramalho

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2006-03-30

Examining board members

Flavio Augusto Portela Santos; Moacyr Corsi; Ricardo Andrade Reis

• Advisor: Flavio Augusto Portela Santos

Abstract

The objectives of this trial were to compare the performance of growing cattle grazing tropical pastures without (CONT) or with energy (ENER) or protein (PROT) supplementation. Also, the effects of supplementation during the grazing period on the feedlot finishing period were evaluated. Seventy-five crossbred (Braunvieh x F1 Angus x Nelore) bull calves, averaging 8 months old and 200 kg BW, grazed 22 ha of Guinea grass (Panicum maximum) from December 2004 through may 2005. Pasture area contained 8 paddocks managed on a rotational grazing system, with a variable resting period. Pastures were fertilized with 45 kg of N/ha/grazing cycle. Cattle grazed the pastures as a single group. Every morning, animals were separated according to the 3 experimental treatments, to be fed the respective supplements. The CONT animals were moved back to the pastures while ENER and PROT animals were fed their respective supplements at 0.6% of BW (as fed). ENER supplement (6.4% CP) contained dried citrus pulp and a mineral mix with monensin. PROT supplement (19% CP) contained citrus pulp, cottonseed meal and mineral mix with monensin. Daily weight gain was higher (P<0.05) for ENER (0.908 kg.animal-1) and PROT (0.967kg.animal-1 ) compared to CONT animals (0.74 kg.animal-1). Type of supplement did not affect cattle daily gain (P>0.05). After the 158 days of the grazing period, animals were feedlot finished. All animals were fed the same ration (82% concentrate and 18% corn silage). Average daily gains were 1.38, 1.51 and 1.45 kg.animal-1 for CONT, ENER and PROT treatments respectively and were different (P<0.05). Animals fed energy supplement (ENER) during the grazing period, gained faster (P<0.05) during the feedlot period than no supplemented animals (CONT). Animals not supplemented during the grazing period (CONT) did not present compensatory gain compared to supplemented ones (ENER or PROT) during the feedlot period. Compared to the CONT performance, the extra weight of supplemented animals (ENER or PROT), gained during the grazing period, was maintained or increased during the finishing period. (AU)