The impact of intensification process on environmental and productive parameters during growing and finishing phase of beef cattle raised in palisadegrass grazing system

Author(s)

Laís de Oliveira Lima

• Document type: Master's Dissertation
• Press: Jaboticabal. 2021-06-17.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2021-05-12
• Advisor: Euclides Braga Malheiros; Márcia Helena Machado da Rocha Fernandes

Abstract

Due to the concern arising from the environmental impacts caused by beef cattle, this study aimed to identify the environmental and productive impact of the beef cattle intensification process in order to develop a comprehensive set of indicators for the sustainable intensification of beef cattle chain. The experimental area consisted of 24 ha of Urochloa brizantha Hochst ex A. Rich Stapf cv. Marandu divided into 12 paddocks of approximately 2 ha each. Were used 48 tester Nellore young bulls with an average weight of 273.7 ± 7.6 and regulating animals were used to maintain the canopy height at 25 cm, using a grazing method in continuous stocking and the “put and take” technique with variable stocking. The treatments were of different intensification levels: low (0 nitrogen [N] ha-1) intermediate (75 kg N ha-1) and high (150 kg N ha-1) in a completely randomized with three treatments design with four replications (paddocks). The fertilization was with ammonium nitrate (32% N). At backgrounding, all animals received a mineral mixture ad libitum. At the finishing phase, the animals of the low level of intensification were supplemented with 2% of body weight in the pasture, while the animals of intermediate and high intensification were finished in feedlot. Animals from all treatments received only human-inedible feed during the entire experimental period. Pasture evaluation included the determination of forage mass and the determination of nutritional components of forage. Animal response variables include, performance, intake and digestibility of nutrients, emission of enteric methane (CH4), nitrogen balance (N), carbon footprint and net protein contribution (NPC). Crude protein (CP) intake and N balance increased linearly with the intensification levels (P < 0.05). Crude protein digestibility increased at a decreasing rate (quadratic effect, P < 0.05) with increasing intensification. In addition, N fertilization resulted in a linear increase in SR and average daily gain (ADG) from 1.75 animal unit (AU = 450 kg) ha-1 and 0.62 kg d-1 (0 kg N ha-1) to 3.75 AU ha-1 and 0.82 kg d-1 (150 kg N ha-1), respectively. Individual CH4 emissions were not affected by treatment (P > 0.05). Carcass production increased with the intensification levels (P < 0.05), however GHG emissions intensity (kg CO2e kg carcass-1) also increased with the intensification levels (P < 0.05). Enteric methane was the main contributor to total greenhouse gases (GHG) emissions in all systems in both phases. Conversion efficiency of beef cattle (HePCE) was similar for all systems in all phases (P > 0.05). Net protein contribution (NPC) was above 1 for all systems and phases, indicating each system was positively contributing to supply human protein requirements. Improvements in grazing management is a powerful tool to mitigate environmental impact of grazing systems and the beef production system is a net contributor to the human protein supply without competing for food. (AU)

• FAPESP's process: 18/26492-0 - Environmental and productive impact of the process of intensification of the of growth and finishing phase of beef cattle managed in marandu grass
• Grantee: Laís de Oliveira Lima
• Support Opportunities: Scholarships in Brazil - Master