With 15 million tons in 2018, sheep meat represented 4.5% of the total animal protein produced in the world, and sheep farming represents an important global socioeconomic activity, especially in developing countries. Despite the increase in sheep meat consumption in Brazil, this scenario was not accompanied by production, placing the country in a prominent position in the importation of sheep meat in the international market. In the production of confined lambs, food is the main factor responsible for the success in the activity, and must meet the requirements of the category so that the animals can express their full development potential. In addition, it represents the highest operational cost of the activity, reaching 70% of all production costs. The use of cheaper components in the diet composition and the selection and maintenance of more efficient herds of animals can be strategies to reduce costs and increase production. The ability to transform the ingested feed into meat, milk or wool is defined as feed efficiency that allows selecting more productive animals and possibly producing less excrement and lower greenhouse gas emissions in their production cycle. Thus, improving the efficiency of a herd, by selecting more efficient animals, becomes extremely important. The lack of studies involving traits of economic importance, such as feed efficiency in sheep breeding programs, as well as the little knowledge generated about the phenotypes that would be associated with this important trait, constitute the problem to be addressed in this project. The objective of the project is to characterize sheep of different phenotypes for feed efficiency, mainly residual feed intake and residual consumption and gain, and to evaluate the effects of sheep selection by feed efficiency measures on the rate of passage and emission of enteric methane (CH4) and , later, evaluating these characteristics in their lambs, plus carcass and meat characteristics, associating the results with thermography data. The experiment will be conducted at the Institute of Animal Science (IZ/APTA, Nova Odessa, SP) in partnership with the Center for Nuclear Energy in Agriculture (CENA/USP, Piracicaba, SP). Data on feed efficiency measures (performance, feed conversion, residual feed intake - RFI and consumption and residual gain - CGR) will be obtained with the help of the Intergado® system, in animals of two categories: empty females and, later, with their lambs. The test, with duration of 80 days (15 of adaptation and 65 of data collection) will be carried out with 40 ewes (8±1 months), for the ranking of the ewes in relation to RFI and CGR. On the final days of the test, through markers, the rate of passage of food will be evaluated. Subsequently, these animals will be placed in semi-open respirometric chambers for the evaluation of enteric CH4 emission. During the entire experimental period, thermographic photos will be taken from different pre-fixed points on the animals for later correlation with the other characteristics. At the end of the first phase of the experimental period, the females will be synchronized and inseminated, using semen from a single sire. Lambs born from these ewes will be divided into males and females and, after weaning (90±10 days) will undergo the same tests previously performed on ewes (RFI, CGR, passage rate, methane and thermography) added to the slaughter to evaluate the characteristics of carcass and meat. The results of this project will contribute to the improvement of the parameters of selection of feed efficiency of sheep, seeking to reduce the environmental impact and generating financial return in a sustainable production system, guaranteeing the competitiveness of this sector in the face of the challenges of producing products of animal origin that meet the demands.
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