To evaluate the effects of molybdenum
(Mo)- and sulfur (S)- induced copper (Cu)
deficiency, 99 prepubertal heifers were
allotted into two groups. Treated heifers (n =
72) were fed a grass hay naturally high in Mo
(Mo = 8 ppm and Cu = 3.2 ppm). Sulfur
was supplemented to achieve a dietary level of
.3%. Control heifers (n = 27) received a
grass hay with normal levels of Mo (Mo =
.47 ppm and Cu = 1.5 ppm). Copper was
supplemented to achieve a dietary level of 8
ppm. Diets were fed for a period of 163 d.
Liver samples were collected and analyzed for
total Cu. Copper-containing enzyme activity
(ceruloplasmin and Cu,Zn-superoxide
dismutase [Cu,Zn-SOD]), and progesterone
were measured in blood serum. Heifers in the
treated group had lower concentrations of liver
Cu and decreased ceruloplasmin activity, with
no differences noted in Cu,Zn-SOD activity or
onset of puberty. No difference was detected
in first-service conception rate following
artificial insemination (AI). Overall AI
pregnancy rate tended to be higher for control
heifers.
