Performance and methane emissions of Nellore steers grazing tropical pasture supplemented with lipid sources

Revista Brasileira de Zootecnia © 2016 Sociedade Brasileira de Zootecnia ISSN 1806-9290 www.sbz.org.br R. Bras. Zootec., 45(12):760-767, 2016 Performance and methane emissions of Nellore steers grazing tropical pasture supplemented with lipid sources Isabela Pena Carvalho de Carvalho1, Giovani Fiorentini1, Alexandre Berndt2, Pablo de Souza Castagnino1, Juliana Duarte Messana1, Rosa Toyoko Shiraishi Frighetto3, Ricardo Andrade Reis1,4, Telma Teresinha Berchielli1,4 1 Universidade Estadual Paulista, Faculdade de Ciências Agrárias e Veterinárias, Jaboticabal, SP, Brazil. Embrapa Pecuária Sudeste, São Carlos, SP, Brazil. 3 Embrapa Meio Ambiente, Jaguariúna, SP, Brazil. 4 Researcher CNPq/Member of INCT-CA. 2 ABSTRACT - The objective of this study was to evaluate the effect of lipid sources on voluntary intake, digestibility, performance, and CH4 emission of Nellore steers grazing Brachiaria brizantha cv. Xaraés forage in the dry season. Forty-five Nellore steers with average weight of 442±34 kg were alloted into one of the five treatments: without additional fat; with palm oil; with linseed oil; with protected fat; and with whole soybeans. The supplements were provided daily and quantities were adjusted to 1% of body weight and diets were formulated in accordance with the Cornell Net Carbohydrate and Protein System. The experimental design was completely randomized with five treatments and two replications. There were no effects on dry matter, organic matter, and neutral detergent fiber intake with the inclusion of lipids in the diet. The neutral detergent fiber showed decreased digestibility in animals receiving linseed oil and palm oil treatments compared with animals receiving the diet without additional fat. The linseed oil treatment reduced CH4 emissions by 38% when expressed in mg/d/kg BW and tended to reduce the emission in g/d/kg BW0.75. Lipid sources did not affect the weight gain of the animals. The intake and performance of grazing Nellore steers supplemented at 1% body weight with lipid sources were not modified. However, fiber digestibility was reduced with palm or linseed oil addition. Linseed oil reduced enteric CH4 emissions. Linseed oil has the potential to reduce enteric CH4 emissions in continuous tropical grazing systems based on B. brizantha grass. Key Words: linseed oil, palm oil, protected fat, supplementation, whole soybeans Introduction The production of beef cattle in tropical countries is generally associated with grazing cultivated pastures and low production costs. However, increased competitions in feed prices for better meat quality as well as the growing concern about emissions of greenhouse gases are causing changes in the beef production system in Brazil and in the world. Methane (CH4) and CO2 are natural byproducts of microbial fermentation of carbohydrates and, to a lesser extent, aminoacids in the rumen and the hindgut of farm animals (Hristov et al., 2013). Methane emissions represent a loss of about 5 to 7% of dietary gross energy (to as low as Received February 11, 2016 and accepted August 4, 2016. Corresponding author: http://dx.doi.org/10.1590/S1806-92902016001200005 Copyright © 2016 Sociedade Brasileira de Zootecnia. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 3% in cattle fed high-grain diets) and are about 16 to 26 g/kg of dietary dry matter intake (DMI) (could be lower with diets containing very high proportions of grain) (Hristov et al., 2013). Various strategies can be used to reduce enteric CH4 production (Hristov et al., 2013), highlighting the inclusion of dietary lipids (Martin et al., 2010). The addition of lipids to ruminant diets has also been recommended, as it similarly increases energy efficiency and hence reduces methanogenesis. Although greater concentrations of fats substantially decrease methane production, they often exert detrimental effects on fiber digestion and, consequently, on animal performance (Patra, 2013). Supplementation of unsaturated fatty acids (UFA) exerts deleterious effects on methanogens and protozoa and reduces the acetate:propionate ratio in the rumen (Macmüller et al., 1998). In this manner, there is a reduction in production of ruminal enteric CH4 and the intensity in which this inhibition occurs is determined by the degree of fat saturation and the supplemented amount (Fievez et al., 2003). These disturbances are attributed mainly to modifications in the rumen microbial ecosystem (Doreau and Chilliard, 1997). Although polyunsaturated 761 Carvalho et al. fatty acids (PUFA) may decrease protozoa and promote cellulolysis (Doreau and Ferlay, 1995), the prevailing action is the modification of microbial membrane permeability, causing metabolic disorders, mainly in cellulolytic flora (Maia et al., 2007). Many products with different fatty acid profiles can be used as fat sources in diets for ruminants (Fiorentini et al., 2014; Neto et al., 2015). However, there are few studies that assess the effect of lipids upon CH4 emission mitigation and upon performance of zebu cattle grazing tropical pasture. Furtheremore, diets rich in fiber could result in increased rates of lipolysis and hydrogenation (Jenkins, 1993) and cause less toxicity to microorganisms due to reduction in the level of dietary PUFA (Broudiscou et al., 1994). We hypothesized that the inclusion of lipids in supplements for grazing cattle reduces CH4 emissions without affecting performance and that more unsaturated sources would cause greater reductions. In this manner, this work aimed to evaluate intake, digestibility, performance, and emission of enteric CH4 in Nellore steers supplemented with lipid sources and grazing Brachiaria brizantha cv. Xaraés forage during dry season. Material and Methods The study was carried out in Jaboticabal, SP, Brazil, located at 21°15'22" S latitude, 48º18'58" W longitude and 595 m altitude. According to the Köppen classification, the climate of Jaboticabal is tropical, Awa type, with rainy summers and dry winters. The protocol used on this experiment was in accordance with the COBEA (Colégio Brasileiro de Experimentação Animal) guidelines and was approved by the CEBEA (Comissão de Ética e Bem Estar Animal) of the FCAV-UNESP - Jaboticabal campus (case no. 012799). Forty-five castrated Nellore steers with average initial body weight of 442±34 kg and eight months of age were used. The animals were kept in 1.9-ha paddocks of Brachiaria brizantha cv. Xaraés pasture under continuous grazing system with a variable stocking rate (put and take), maintaining a sward height of 35 cm. The animals were distributed in a completely randomized design (five animals per paddock and two paddocks per treatment) with two replicates per treatment. The formulations of diets were specified using RLM/ E (...truncated)