Mature, crossbred beef cows (n = 87 in
1990-91, n = 84 in 1991-1992) were used to
determine the effects of protein supplementation
to cows fed ammoniated wheat straw
during late gestation. Treatments included: 1)
Control (C) - no supplement, 2) Low Protein
(LP) - 4.5 lb of a 10% crude protein (CP)
supplement, 3) Medium Protein (MP) - 4.5 lb
of a 20% CP supplement, and 4) High Protein
(HP) - 4.5 lb of a 30% CP supplement.
Supplementation increased weight gain over
controls (P<.01). HP cows gained more
(P=.05) weight than LP-supplemented cows
and tended (P=.11) to gain more weight than
MP-supplemented cows. Supplementation also
increased body condition score (BCS, 1-9
scale) over control cows (P<.01), but no
difference was noted among supplemented
groups. From the end of the feeding period
until weaning, cows previously supplemented
lost more weight (P<.01) than controls and
exhibited little change in BCS, whereas controls
increased BCS by .5 during the same
period. Calving dates, calf birth weights, calf
weaning weights, calf average daily gain,
percent of cows cycling prior to breeding, and
percent of cows pregnant did not differ
between treatments. Consequently, although
additional protein increased weight gain prior
to parturition, this response did not impact
economically important traits.
