CONTINUOUS PROFILES AND WITHIN-DAY VARIATIONS OF METABOLITES AND HORMONES IN COWS FED DIETS VARYING IN ALIMENTARY SUPPLIES BEFORE SHORT-TERM FEED DEPRIVATION
Bb. Ndibualonji et al., CONTINUOUS PROFILES AND WITHIN-DAY VARIATIONS OF METABOLITES AND HORMONES IN COWS FED DIETS VARYING IN ALIMENTARY SUPPLIES BEFORE SHORT-TERM FEED DEPRIVATION, Journal of animal science, 75(12), 1997, pp. 3262-3277
We investigated continuous profiles and within-day variations of some
metabolites and hormones in four nonpregnant, nonlactating cows fed ha
y-based diets in two equal meals. Diets supplied either too much or to
o little N (approximately 1.3 or .8 times the maintenance requirements
) and NE1 (approximately 1.2 or .8 times). Continuous collection of ru
minal liquor, blood, and urine samples was performed for 42 consecutiv
e hours, the last 16 h covering a period without feed. For twice-daily
feeding, nitrogenous and energetic underfeeding decreased average rum
inal propionate and the insulin:growth hormone ratio. However, only th
e energetic underfeeding increased plasma S-methylhistidine and urinar
y excretion of 3-methylhistidine, and decreased body weight and rumina
l acetate, butyrate, and total VFA. Conversely, only the nitrogenous u
nderfeeding decreased glycemia. Whatever the dietary level, the 42-h p
atterns of metabolites and hormones were mainly affected by the time f
rom the last meal. An energy deficit progressively took place during f
eed deprivation and the nocturnal interprandial period but not during
the diurnal interprandial period. During the feed deprivation and noct
urnal periods, glycemia was maintained despite a shortage in ruminal p
ropionate. We conclude that in twice-daily fed cattle 1) the dietary s
upply of energy is the main trigger for an energy deficit and the subs
equent muscle protein mobilization; 2) the nocturnal interprandial per
iod may be considered as short-term feed deprivation; 3) the diurnal p
atterns of metabolites and hormones are not affected by the nitrogenou
s and(or) energetic supplies of the diet.