This study aimed to evaluate the effect of different phases of feed restriction on the
metabolism and placental indices of growing heifers inseminated with sexed semen of one
bull and on the birth weights of their calves. Red-Holstein heifers were randomly divided
into three groups. C-group animals (N = 17) daily received recommended energy and crude
protein (standard diet). ER-Group animals (N = 14) were fed 60% of recommended energy
and crude protein for the first two pregnancy months followed by the standard diet. LRgroup
animals (N = 13) were provided with the standard diet throughout the first seven
months and with 60% energy and crude protein for the last two months of pregnancy.
Blood metabolites and weights of dams were assessed regularly during pregnancy. Placenta
weight, area of placentomes and calves’ birth weights were examined directly after birth.
The physiological levels of blood metabolites varied in C-group animals during the different
pregnancy stages. Both restriction periods resulted in reduced weight gain of the dams.
ER-group animals showed a marked compensatory growth during mid-pregnancy. Serum
glucose, cholesterol and beta-hydroxybutyrate were lower in ER-group animals compared
with C-group animals during early restriction. During late restriction, only non-esterified
fatty acids increased in LR-group animals. Placental parameter and calves’ birth weights
did not differ between groups. Results indicate only minor effects of a 40% energy and protein
restriction during early or late pregnancy in growing heifers on maternal metabolic
and placental indices as well as on foetal development, but further studies might show
long-term consequences of offspring.
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