|Abstract or Summary
- Ninety-six mature pregnant Hereford cows were allotted to three
replications with four treatments. Pregnancy was determined by rectal
palpation prior to the initiation of the study. The cows were
artificially inseminated the previous spring, beginning the end of
May, over a period of 42 days to a single Angus sire. Hereford
cleanup bulls followed for 21 days.
The cows were stratified by breeding date, weight, condition
score and the previous year's adjusted weaning weights and randomly
assigned to treatments. Replications were by calving date.
Monensin treatments consisted of 0, 50, 200 and 300 mg/hd/day
and was provided in ground barley. Controls received .45 kg of barley/
head/day with the monensin treatments receiving their doses in
like amounts of barley.
The basic feed was native meadow hay containing 9.5% crude
protein. Hay was weighed in daily and refusals out weekly. Throughout
the study hay was adjusted to maintain equal weight gain or loss
Initially the control cows were fed hay free choice and consumed
13.4 kg/head/day. The initial monensin treatment levels were 95% of
the control's diet for the 50 mg level and 90% each for the 200 and
300 mg groups. Hay consumption for the entire confinement period was
92, 89 and 90% of the control group's diet for the 50, 200 and 300 mg
Rumen samples were taken twice during the study, once prior
to calving and another postpartum. An esophageal hose connected to
a vacuum pump was utilized on four cows per pen for a total of 48
samples. On the morning samples were taken the cows were fed at
one-half hour intervals to allow ample time for sampling. All cows
were sampled three to four hours after supplemental feeding. Volatile
fatty acid concentration results show rumen acetic acid production
was reduced and propionic increased with the 200 and 300 mg
Cow weights were obtained every 28 days prior to calving and
were used to adjust hay intake. Cows and calves were also weighed 24
hours postpartum, treatment termination and weaning.
Initial cow weights for the control, 50, 200 and 300 mg treatments
were 455, 447, 456 and 457 kg, respectively, with prepartum
gains of .34, .38, .38 and .37 kg. Weight loss during the calving
and postpartum periods were similar with the exception of the 300 mg
group, which lost more weight.
At or near time of calving cows were removed from their pens
and taken to a calving shed. Hay fed was adjusted accordingly so the
cows remaining in the pens received the proper level. Cows that lost
calves or had health problems were eliminated from subsequent data.