Impact of dietary protein amount and rumen undegradability on intake, peripartum liver triglyceride, plasma metabolites, and milk production in transition dairy cattle
Rb. Greenfield et al., Impact of dietary protein amount and rumen undegradability on intake, peripartum liver triglyceride, plasma metabolites, and milk production in transition dairy cattle, J DAIRY SCI, 83(4), 2000, pp. 703-710
Feeding strategies of transition dairy cows contribute to the risk factors
associated with metabolic disorders that limit production in the ensuing la
ctation. To investigate the effects of prepartum dietary crude protein (CP)
concentration and amount of rumen-undegradable protein (RUP) on postpartum
health and production, 44 multiparous Holstein cows were blocked by expect
ed calving date and assigned to one of four isoenergetic prepartum rations
beginning 28 d prior to expected calving date. Prepartum rations were: 12%
CP and 26% RUP, 16% CP and 26% RUP, 16% CP and 33% RUP, or 16% CP and 40% R
UP on a dry matter basis. All cows were fed the same postpartum diet (18% C
P, 40% RUP) from 1 to 56 d in milk (DIM). Prepartum dry matter intake (DMI)
was not different among dietary treatments. Mean postpartum intakes (kg/d)
were higher through 56 DIM (P < 0.05) for cows fed the 12% CP:26% RUP diet
prepartum compared with any of the 16% CP diets (21.8 vs 19.8, 18.6 and 18
.6; 12% CP:26% RUP vs. 16% CP:26% RUP, 16% CP:33% RUP and 16%, CP:40% RUP).
There was a DIM x prepartum diet interaction (P < 0.05) with the greatest
effect of the 12% CP:26% RUP diet evident during the first 35 DIM. Cows fed
the 12% CP:26% diet during the transition period tended to produce more mi
lk (kg/d) (P = 0.08) than did cows fed any of the 16% CP diets (40.8 versus
37.8, 38.7, and 37.4; 12% CP:26% RUP vs. 16% CP:26% RUP, 16% CP:33% RUP, a
nd 16% CP:40% RUP). Additional protein (12 vs. 16% CP) in the prepartum die
t tended to decrease milk protein (P = 0.10) and milk fat yield (P = 0.08)
but did not alter percent milk fat, percent milk protein, or MUN. Liver tri
glyceride (TG) expressed as milligrams of TG per microgram of DNA or percen
tage of dry matter (DM) on d -28, -14, +1, +28, and +56 relative to calving
were not significantly different among treatments. Maximal (P < 0.05) infi
ltration of TG in liver was observed on +1 d when expressed as a percentage
of DM and on +28 d when expressed as milligrams of TG per microgram of DNA
. Plasma glucose, calcium, urea nitrogen, beta-hydroxybutyrate, and noneste
rified fatty acids were not different (P < 0.05) among treatments. The data
indicate carryover effects of prepartum dietary protein on postpartum inta
ke and milk production, pointing to beneficial effects of maintaining dieta
ry protein for dairy cows in late gestation at 12% CP.