Further comparisons of energy and protein sources for growing cattle

Abstract

SummarySpring-barley straw or maize silage were the major components in mixed diets of compound and forage fed to yearling dairy heifers. With straw, rolled barley was fed either alone or with fishmeal, soya-bean meal, protected soya-bean meal, whey + urea or Ewoplua (a product made from whey and rich in lactosyl urea). With maize silage the rolled barley was fed either alone or with fishmeal, whey + urea or Ewoplus.When straw was included in the diet fishmeal and protected soya-bean meal increased live-weight gain, and all the supplements increased nitrogen retention. When maize silage was fed, only fishmeal increased live-weight gain although all the supplements increased digestibility. Concentrations of rumen NH3-N were increased by all the supplements, when fed with straw, and also by maize silage when fed without an N supplement or with fishmeal. Small changes were noted in total and molar proportions of VFA.Calculated ME intakes suggested a more efficient use of energy for growth from maize silage than from straw, except when the straw diet was supplemented with fishmeal.