To determine effects of different nutritional
regimens on beef palatability and collagen characteristics,
we randomly assigned 18 Hereford
steers of similar age and nutritional background
to three treatment groups: group 1 was slaughtered
directly off pasture at about 19 to 20
months of age; group 2, composed of animals
the same age as those in group 1, was slaughtered
after being fed a high energy diet for 120 days,
and group 3, 23 to 24 months of age, was
slaughtered after 126 days on a high energy
diet. Feeding the high energy diet increased
USDA quality and yield grades. Longissimus
(LD) steaks from the three groups did not
differ in total collagen content, sarcomere
length, Warner-Bratzler shear force, cooking
loss or sensory panel ratings for tenderness,
juiciness and flavor intensity. However, LD
samples from group 3 animals had a higher
(P<.05) percentage of salt plus acid soluble
collagen and less organoleptically detectable
connective tissue than LD samples from group
1. LD samples from group 2 animals had a
higher (P<.05) percentage of salt soluble
collagen than those from group 1. Biceps
fernoris (BF) steaks from group 1 steers were
juicier than those from groups 2 and 3. Feeding
regimen did not consistently affect BF collagen
solubility, taste panel tenderness or shear force.
Beef from grass-finished cattle received acceptable
taste panel scores. The effects of the high
energy diet on plasma nonprotein hydroxyproline
content and live animal weight were
monitored in group 3. Plasma nonprotein
hydroxyproline content (an indicator of
collagen degradation) was highest at approximately
42 days on feed and corresponded well with weight gain. These results suggest that
collagen turnover is accelerated during the rapid
growth phase of cattle fed a high energy diet.
