Abstract :
A database of 622 treatment mean observations of the dietary concentration of CP and apparently digestible CP (DCP) from
146 publications was used to estimate true digestibility of CP and metabolic fecal CP (MFCP) in goats. A regression of DCP
against CP with the entire database yielded the equation: DCP = 0.8566×CP (%DM)−2.697 (r2 = 0.851, root mean square
error= 1.58). There were some observations with lower than predicted DCP, some of which were with diets containing browse.
Therefore, observations with residuals<1.58 were deleted, resulting in the equation:DCP = 0.8831×CP (%DM)−2.67 (r2 =
0.952, root mean square error = 0.86; n = 562); estimates of MFCP and true CP digestibility were considered the Y intercept
and slope, respectively. To address variables of the entire database with less than expected DCP, the database was split into
a subset to develop equations (60% of observations), with inclusion of additional variables such as DM intake and dietary
concentrations of forage and browse, and one to evaluate. However, multiple regression equations did not greatly improve
prediction, with lower than predicted DCP appearing a consequence of depressed true CP digestibility rather than increased
MFCP. In conclusion, for goats consuming diets without browse, 0.88 and 2.67% DM appear appropriate estimates of true
CP digestibility and MFCP, respectively, similar to values for other ruminant species.
© 2004 Elsevier B.V. All rights reserved.
