Pj. Eppard et al., EFFECT OF EXOGENOUS SOMATOTROPIN ON HEMATOLOGICAL VARIABLES OF LACTATING COWS AND THEIR OFFSPRING, Journal of dairy science, 80(8), 1997, pp. 1582-1591
Eighty-two lactating Holstein cows in their first, second, or third la
ctation received either one, three, or five concurrent i.m. injections
of a unit dose (0.6 g) of zinc methionyl bovine somatotropin (bST) or
five doses of the vehicle. Injections were administered at 14-d inter
vals from GO +/- 3 d postpartum until the end of lactation or until ne
cropsy. Thirty-eight cows were continued on the treatment for a 2nd yr
. Blood samples were collected at wk -2, -1, 3, anti 7 relative to the
start of treatment and then every 8 wk (yr 1) or 4 wk (yr 2) thereaft
er. Untreated cows that were included in a survey of the resident herd
were bled at wk 7 or 8, wk 10 or II, and wk 13 or 14 of lactation and
every 4 or 8 wk thereafter. Calves were bled within 72 h of birth and
at approximately 5 wk Of age. Most parameters associated with erythro
cytes were decreased mildly in cows that were treated with bST. Howeve
r, data remained within generally accepted reference ranges, and chang
es were not of clinical importance. Decreased hematocrit was not assoc
iated with increased hemolysis, hemodilution, or clinical anemia. No m
orphological lesions related to treatment were noted in the bone marro
w or spleen; bST did not affect the incidence of immature cell types.
Energy and protein balances did Hot significantly affect the hematolog
ical results of the cows. Calves generally were unaffected by bST trea
tment of the dam, but heavier calves had higher parameters associated
with erythrocyte and lymphocyte counts than did calves with lower body
weight. Exogenous bST treatment caused predictable changes in hematol
ogical parameters of dairy cows.