Mathematical linkage of total-tract digestion of starch and neutral detergent fiber to their fecal concentrations and the effect of site of starch digestion on extent of digestion and energetic efficiency of cattle

Abstract

Published regression equations relating digestibility of starch to fecal starch concentration have slopes that differ by over 5-fold. Hence, nutritionists have questioned their legitimacy. Total-tract starch digestibility and concentration of starch in feces are interlocked mathematically by 2 factors-starch content of the diet and digestibility of diet DM. Digestibility data compiled from the published literature including 201 diets fed to lactating dairy cows and 191 diets fed to feedlot cattle were employed to reexamine the relationships of digestibility to fecal concentrations of starch and NDF. Regression analyses and plots clearly illustrated imprecision of this relationship when diet starch content and digestibility of diet DM were ignored. Furthermore, because fecal starch and diet digestibility are related inversely, mathematics implies that starch digestibility is related curvilinearly to fecal starch concentration. Effects of site of starch digestion on extent of digestion and energetic efficiency also were examined. Direct digestibility measurements for nutrients and energy can preclude errors involved with in vitro availability assays, prove more economical than laboratory procedures to predict nutrient digestibility, and provide more applicable data concerning energy availability when compared with summing tabular means for feedstuffs from publications or from computerized diet formulation programs. When combined with DMI, direct digestibility measurements should markedly improve precision for quantifying amounts of nutrients and energy available for maintenance and performance by productive ruminants in dairies or feedlots. As with all analytical procedures, accurate digestibility measurement requires representative sampling and proper analysis of diets and feces.

Predictability of growth performance in feedlot cattle using fecal near infrared spectroscopy

“…Validation of the calibration included not only samples from the current study but also from other feedlot studies as described in Jancewicz et al (2017a). Fecal starch, NDF, and ADL were selected as the key nutrients of interest based on results from regression models (described below) and previous studies (Jancewicz et al 2017b;Owens et al 2016). Reference analysis consisting of wet chemistry for OM, starch, N, NDF, ADF, ADL, and EE (AOAC 2005) was conducted on a subset of fecal samples from each feedlot (24 from the current study) and the samples of which neighborhood distance (ND) was above a certain threshold (0.60) were used to expand the original calibration.…”

“…Cereal grains are a major ingredient in diets for finishing cattle, and given the high proportion of starch in grains, predictions have been developed to rapidly estimate starch digestibility using fecal starch concentration (Zinn et al 2002;Corona et al 2005;Zinn et al 2007). Research by Owens and Zinn has shown that the accuracy of starch digestibility predictions can be improved by including additional variables such as fecal N (Zinn et al 2011), dry matter (DM) or organic matter (OM) digestibility, and starch intake (Owens et al 2016). Methods to predict other nutrient digestibilities, particularly neutral detergent fiber (NDF), from their fecal concentrations have been examined (Fredin et al 2014;Jancewicz et al 2016;Owens et al 2016), as well as indirect relationships between OM digestibility and fecal crude protein (CP) (Lukas et al 2005).…”

“…Research by Owens and Zinn has shown that the accuracy of starch digestibility predictions can be improved by including additional variables such as fecal N (Zinn et al 2011), dry matter (DM) or organic matter (OM) digestibility, and starch intake (Owens et al 2016). Methods to predict other nutrient digestibilities, particularly neutral detergent fiber (NDF), from their fecal concentrations have been examined (Fredin et al 2014;Jancewicz et al 2016;Owens et al 2016), as well as indirect relationships between OM digestibility and fecal crude protein (CP) (Lukas et al 2005). Because fecal samples contain information relevant to feed digestion, monitoring how efficiently cattle are utilizing nutrients could directly benefit the efficiency and profitability of feedlot cattle production.…”

Effect of ensiling time on apparent total tract starch digestibility in Southern Brazilian dairy herds

“…Moreover, Owens et al (2016), when evaluating published regression equations, concluded that the relationship of starch digestibility and fecal starch must be curvilinear, not linear. According to the authors, although these two variables are mathematically linked, additional factors are essential for an accurate relationship: (a) daily fecal output, which varies with the indigestibility of dietary DM; and (b) starch intake, which varies with its dietary concentration and dry matter intake.…”

Effect of the addition of essential oils, enzymes, ionophores and combinations of feed additives in finishing cattle diets

“…for starch digested in the rumen, small intestine, and large intestine as estimated by Huntington et al (2006), the point and extent to which efficiency of use of energy from digested starch can be calculated as outlined by Owens et al (2016).…”