Diet Experiment

Researcher

Michel Wattiaux, International Agriculture Program, CALS, U WI Madison

Description

This experiment (Wattiaux, Combs and Shaver 1994) involved 60 cows initially, although some were lost during the study. The cows were randomly assigned to one of 6 diets and followed for a number of weeks. Diets were begun after the third week, allowing the animals some initial time to adjust to their new environment. Interest focuses on the effect of diet on the average dry matter intake (dmi), the amount of food eaten by each cow. The data you have are a baseline value (covar = dmi for week 3), average dmi during subsequent weeks, the number of subsequent weeks. In addition there are cow and block identifiers. The experiment was a randomized block design. That is, cows were blocked by time, the first 6 cows were randomly assigned among the 6 diets, and so on. ``Proper'' analysis should take account of this, along with the initial capacity of each animal (its covariate of dry matter intake at 3 weeks) and possibly weighting by the number of weeks each cow was on trial.

Reference

Wattiaux MA, Combs DK and Shaver RD (1994) ``Lactational responses to ruminally undegradable protein by dairy cows fed diets based on alfalfa silage'', J Dairy Science 77, 1604-1617.

Data & Setup

diet.dat

cow trt block covar dmi weeks

diet.s

read data, various analysis of variance

diet.sas

SAS code for reading and analysis

Book Figures

dietcov.s

F: Diet Adjusted for Initial Capacity