Sample size involving multiple traits: an application to digestibility in cattle

• Autor(a) principal: Freitas, Alfredo Ribeiro de
• Data de Publicação: 1999
• Outros Autores: Manzano, Airton, Esteve, Sérgio Novita
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Pesquisa Agropecuária Brasileira (Online)
• Texto Completo: https://seer.sct.embrapa.br/index.php/pab/article/view/5547
• topic: F-distribution; minimum significative difference; Hotelling's; distribuição F; diferença mínima significativa; Hotelling

The objective of this work was to estimate minimum sample size (n) for comparison of treatments in experiments of consumption and digestibility of cattle in a multitrait analysis. Data from digestibility of 72 heifers aging approximately 18 months and with 250 kg of live weight were used. A completely randomized experiment was conducted at Embrapa-Centro de Pesquisa de Pecuária do Sudeste, São Carlos, SP, Brazil, from 1988 to 1989, considering the combination of nine treatments organized in a factorial 3 x 3 (three genetic groups: Canchim, Nellore and ½ Canchim + ½ Nellore, and three dietary levels of crude protein: 6, 10 and 13%, and eight heifers each). The end points analyzed were feed consumption (g/kg0.75), digestible energy, retained nitrogen (RN), RN (mg/kg0.75), and digestibilities of dry matter, crude protein, neutral detergent fiber and acid detergent fiber. The minimum sample size required to detect significant differences (D) between mean vectors was calculated by a SAS program considering a t-variate normal distribution with mean vector 0 and covariance matrix S, Hotelling's T2 test, F-distribution with noncentrality parameter (d2D) and combinations of type I error (a) and power of the test (1_b) and D. The calculated n ranged from 6 to 47, and was affected more by variation in D than variation in a or power of the test.