03781naa a2200265 a 450000100080000000500110000800800410001902200140006002400380007410000200011224501170013226000090024950008670025852020880112565300230321365300200323665300180325665300220327470000200329670000180331670000190333470000230335370000190337677301200339510628092022-12-02       2022    bl uuuu     u00u1 u    #d  a1871-14137 a10.1016/j.livsci.2022.1048892DOI1 aSILVEIRA, F. A.  aResidual feed intake for Australian Merino sheep estimated in less than 42 days of trial.h[electronic resource]  c2022  aArticle history: Received 16 August 2021, Revised 18 February 2022, Accepted 28 February 2022, Available online 3 March 2022, Version of Record 8 March 2022. --  Corresponding author: Fernando Amarilho-Silveira, mailto: fernando@proagovina.com.br  -- This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. Thank the Instituto Nacional de Investigación Agropecuaria (INIA - UY) for the conduction of the field work in the data collection, which received funding from the European Union’s Horizon 2020 research and innovation program under the Grant Agreement n°772787 (Smarter) and from the Instituto Nacional de Investigación (INIA_CL_38: Rumiar). -- LICENSE: This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).  aABSTRACT.- The evaluation of sheep feed intake (FI) in feed efficiency tests is expensive. Decreasing the test period could be a resource-saving tool by reducing the cost of evaluating each animal and allowing to test a greater number of animals per year. For this reason, the objective of this research was to explore residual feed intake (RFI) models and to decreasing the test duration. Data was collected from 286 Australian Merino sheep of three performed trials, the test period consisted of 56 days (14 days of feed and facilities adaptation and 42 days of FI and average daily gain (ADG) evaluation). Two models were used to calculate RFI, Model 1 (based on Koch et al. (1963) linear model) and Model 2 (repeated measures, weekly model). Model 1 included ADG and FI estimates in a linear regression. The second model included weekly average FI as repeated measure and the weekly ADG. The increase in body weight during the test period was not perfectly linear, presenting a marked variance increase in two of the three tests while FI presented a tendency to increase throughout of the evaluation period, however presenting a high variance per day. In the 42-days tests, Pearson and Spearman correlations between models for ADG were of 0.89 and 0.87, respectively. The best correlations were detected for FI between 42 and 35-days models, presenting Pearson and Spearman correlations of 0.95 and 0.94 in the linear model, and 0.96 and 0.95 in the weekly model. When considering RFI, the correlations between linear and weekly 42-days models were from 0.93 to 0.92, respectively. The 35-days RFI length models (linear and weekly) presented a Pearson and Spearman correlations greater than 0.98 with the 42-days models. Therefore, the RFI models 35-days of duration allowed to decrease seven days of the FI test while maintaining accuracy and explaining 75.3% of the FI in the linear model, and 63.6% of the weekly model. Reducing seven days of testing would provide a greater data collection into a year of phenotypic evaluation. © 2022 The Authors. Published by Elsevier B.V.  aAverage daily gain  aFeed efficiency  aGenetic model  aRepeated measures1 aDE BARBIERI, I.1 aCOBUCI, J. A.1 aMARQUES, C. B.1 aFERREIRA, G. F. DE1 aCIAPPESONI, G.  tLivestock Science, 2022, Volume 258, Article 104889. OPEN ACCESS. doi: https://doi.org/10.1016/j.livsci.2022.104889