Ieo. Abdelgadir et al., RUMINAL AVAILABILITIES OF PROTEIN AND STARCH - EFFECTS ON GROWTH AND RUMINAL AND PLASMA METABOLITES OF DAIRY CALVES, Journal of dairy science, 79(2), 1996, pp. 283-290
Newborn Holstein calves (n = 75) were blocked by date of birth and sex
and assigned randomly to one of eight isonitrogenous starters that co
ntained protein and starch sources of different ruminal availabilities
. Soybean meal or soybeans roasted to an exit temperature of 146 degre
es C, raw or conglomerated corn, and urea at 1% of DM or no urea were
used in a 2 x 2 x 2 factorial arrangement. The conglomeration process
consisted of grinding the grain, adding water, pelleting the mixture,
and roasting, which increased the degree of starch gelatinization five
fold. Starters were fed for ad libitum intake from 0.5 to 8 wk. Urea s
upplementation of conglomerated corn starters depressed performance, b
ut the depression was greater when conglomerated corn was used with so
ybean meal than when it was used with roasted soybeans. Ruminal NH3 an
d plasma urea increased with increased RDP in starters, but the respon
se varied according to corn type and soy protein source. Urea suppleme
ntation depressed plasma Lys, doubled plasma Cit with soybean meal and
conglomerated corn starters, but depressed plasma Cit with roasted so
ybeans and conglomerated corn starters. Conglomerated corn depressed p
lasma Val and Gly, and roasted soybeans increased plasma Phe. Performa
nce was similar when calves consumed starters containing ruminally syn
chronous or asynchronous CP and starch sources.