Mvs. Komaragiri et Ra. Erdman, FACTORS AFFECTING BODY TISSUE MOBILIZATION IN EARLY LACTATION DAIRY-COWS .1. EFFECT OF DIETARY-PROTEIN ON MOBILIZATION OF BODY-FAT AND PROTEIN, Journal of dairy science, 80(5), 1997, pp. 929-937
Twenty Holstein cows were fed diets that were formulated with 16 or 19
% crude protein (CP) that contained, respectively, 6 and 9% ruminally
undegradable protein (RUP) (dry matter basis) to study the effect of i
ncreased RUP on tissue mobilization and production parameters. Cows we
re enrolled in the study from -14 to 114 d postpartum Body composition
measurements using the D2O dilution technique were made at -2, 5, and
12 wk postpartum Maximum loss of body tissue occurred between wk 2 pr
epartum and wk 5 postpartum during which time cows fed both treatments
mobilized a mean of 54 kg of body fat and 21 kg of body protein. Cows
continued to mobilize 18 kg of body fat through wk 12 postpartum, but
the amount of body protein was unchanged. One unit of change in body
condition score corresponded to about 40 kg of empty body fat. Partiti
oning of empty body energy between empty body fat and protein indicate
d that, for each unit of change in body energy, 93% was lost or gained
as body fat, and body protein accounted for only 7%. Increasing RUP i
n the diet had no effect on the postpartum amounts of empty body prote
in, empty body fat, or empty body energy. Milk production was 39.8 kg
for cows fed the 16% CP diet and 42.4 kg for cows fed the 19% CP diet.
There was an interaction of treatment by week postpartum Both dry mat
ter intake and milk production were lower during the first 6 wk postpa
rtum but were greater thereafter for cows fed the 19% CP diet than for
cows fed the 16% CP diet. Milk CP percentage was higher (3.08% vs. 2.
89%), and milk CP yield tended to be greater (1.29 vs. 1.15 kg/d), for
cows fed the 19% CP diet.