A comparison of various methods of estimating digestibility, voluntary intake or average daily gains for beef cattle fed mixed rations
Dissertation Abstracts B, The Sciences and Engineering 28: 3942-3943
ISSN/ISBN: 0420-073X Accession: 014309795
For 43 mixed feeds given to cattle there were close correlations between digestible dry matter (DM) and organic matter, total digestible nutrients (TDN) and energy of digested feed estimated by total collection. Digestible DM estimated in vitro and acid-insoluble lignin were closely related to digestible DM, digestible organic matter and TDN estimated in vivo but solubility of DM was not. Voluntary intake was not generally related to the measurements of digestibility in vitro. Nutritive value index could be estimated from digestible DM in vitro and acid-insoluble lignin. Weight gain was not significantly correlated with estimates of digestibility in vivo or with voluntary intake. Partial correlations of average daily gain with digestible DM estimated in vitro and with acid-insoluble lignin were significant. For estimation of voluntary intake there was little improvement when values for duration of feeding, protein content of the feed and proportion of concentrates were included in a multiple regression. About 50% of the variation in average daily gain could be accounted for in a multiple regression equation embodying voluntary intake per unit metabolic weight (W0.75), digestible DM estimated in vivo, proportion of concentrate in the feed, duration of feeding, acid-insoluble lignin and crude protein content. A regression relating gain to digestible DM estimated in vitro and length of feeding, which accounted for 45.6% of the variation, is presented.