Study of thermal equilibrium associate with CH4 emission in Nelore cattle managed in the field during a period of 24 hours

Author(s)

Cíntia Carol de Melo Costa

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2018-04-10.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2018-02-26
• Advisor: Alex Sandro Campos Maia; Telma Teresinha Berchielli

Abstract

Given the current global climate scenario becomes important to understand what the impacts of a warmer atmosphere on the thermal balance in livestock. Quantifying the emission of greenhouse gases of these animals also becomes important because this activity has a positive impact on the national economy, however, the environmental point of view the impact is negative, because of the contribution of methane emission by enteric fermentation. Therefore, the aim of this work is study the influence of meteorological condition on thermoregulation of Nellore cattle associated with the emission of methane throughout the day. For this, it was done a study at the Animal Biometeorology Laboratory of the São Paulo State University, Jaboticabal, Brazil (21.25° S, 601 m altitude) in December of 2016. Six Nellore cattle with similar weight, age and body condition were assigned in a Latin Square experimental design (24 classes of hours (1-2h; 3-4h; …; 23 - 24h; 24 -1h) during twelve days). Evaluations were performed with animals protected from direct solar radiation and rain overnight. Respiratory parameters as percentage of oxygen (O2; %), carbon dioxide (CO2; %), methane emission (CH4, %), water vapor pressure (PS{TEXP}; kPa), respiratory rate (RR, breaths min-1 ) and ventilation (VE; L s -1 ) were quantified using an indirect calorimetry system; furthermore, hair coat surface (TS, °C), skin (TEP, °C) and rectal temperature (TR, °C) were recorded with thermocouple. Metabolic heat production (q”met), sensible heat flow (q”sens), heat loss from respiratory tract (q”er) and cutaneous evaporation (q”es) and methane emission (eCH4, g h-1 ) were calculated. Meteorological conditions were measure at regular one-minute intervals during each day with a portable weather station. Volumes (L h - 1 ) of O2 and CO2 changed moderately throughout the 24 hours, which resulted in an average metabolic heat production of 151.45 ± 13.60 W m-2 . At the largest thermal gradient (TS - TA; from 24:00 h to 7:00 h), heat transferred by sensible mechanisms corresponded near to 60 % of the metabolism, but at 11:00 h until 17:00 h, when TA was elevated, the cutaneous evaporation represented approximately 53 % of total heat losses. From 20 to 30 °C, thermoregulatory responses of Nellore cattle remained relatively stable over the 24 hours when protected from direct solar radiation and rain, which seems to be a good indicative of lower energy expenditure for body thermal regulation. Enteric methane emission of housed 30-mo-old Nellore cattle fed at requirement maintenance on DM basis is approximately 33 g day-1 animal-1 . Circadian variation of enteric methane emission was clearly associated to the feed time, being not related with meteorological conditions. The open indirect calorimetry system using a non-ventilated facial device provided valuable details on daily pattern of enteric CH4 production of Nellore cattle and its association with O2 consumption and CO2 output. So, this work evaluated the thermal equilibrium of adult Nellore cattle, besides to describe the circadian variation of methane emission, as well as the relationship of these variables with tropical meteorological conditions. Thereby, this work has relevant contributions with inedit results and inovation. (AU)

• FAPESP's process: 14/11170-7 - Study of thermal equilibrium associate with CH4 emission in Nelore cattle managed in the field during a period of 24 hours
• Grantee: Cíntia Carol de Melo Costa
• Support Opportunities: Scholarships in Brazil - Doctorate