|Abstract or Summary
- A four months continuous feeding trial was conducted
to evaluate Canola meal as a single protein supplement in
complete dairy rations. Thirty high producing Holstein
cows in the second week of lactation were randomly alloted
in groups of ten to one of three isonitrogenous (15% CP)
and isocaloric (1.6 Mcal/kg of NE lactation) rations,
containing either Canola meal (38% CP), Soybean meal (46%
CP) or Cottonseed meal (41% CP). Productive and physiological
parameters were analysed.
Milk production, both actual and 4% FCM, did not
differ (P>.05) among diets. However, Canola meal fed
cows tended to produce more milk than animals in other
treatments. No differences (P>.05) were found for milk
protein, fat, total solids nor solids not fat percentages.
Milk solids not fat yield was the only milk component
produced in different (P=.024) amounts between diets and
was mainly influenced by milk production.
Canola meal glucosinolates, tannins and phytate did
not impair feed intake, however animals in this group
showed lower feed conversion.
Rumen total volatile fatty acid content was higher
(P=.031) for Canola meal and Soybean meal groups. No
significant differences (P>.05) were found for rumen
volatile fatty acid composition, acetic:propionic ratio,
ammonia nitrogen or pH.
Urea nitrogen, total protein and albumin plasma
concentrations were not different (P>.05) among diets,
suggesting that Canola, Soybean and Cottonseed meals were
equal as protein supplements.
White blood cells was the only hematological parameter
(packed cell volume, red blood cells, white blood
cells and hemoglobin were analysed) that significantly
differed (P=.011) among diets. Soybean meal fed cows
showed higher white blood cell count, which is believed to
have a physiological origin.
Triiodothyronine uptake values were significantly
higher (P=.015) in Soybean meal fed cows. However,
Triiodothyronine uptake as well as Tetraiodothyronine
concentration and Free Thyroxine Index correspond to
euthyroid values, indicating that Canola meal glucosinolates
did not affect the thyroid metabolism of the
Results indicate that Canola meal may be used as a
single protein supplement in rations for high producing
cows, to satisfactorily replace traditional sources of
protein such as Soybean meal and Cottonseed meal.