De. Grum et al., PRODUCTION, DIGESTION, AND HEPATIC LIPID-METABOLISM OF DAIRY-COWS FEDINCREASED ENERGY FROM FAT OR CONCENTRATE, Journal of dairy science, 79(10), 1996, pp. 1836-1849
Eight Holstein cows ((X) over bar = 52 DIM) were used in a replicated
Latin square design (28-d periods) to determine the effects of source
and amount of dietary energy on hepatic lipid metabolism. Diets were 1
) low concentrate without supplemental fat (1.6 Mcal of NE(I)/kg), 2)
low concentrate with supplemental fat (1.7 Mcal/kg), 3) high concentra
te without supplemental fat (1.7 Mcal/kg), and 4) high concentrate wit
h supplemental fat (1.8 Mcal/kg). Intakes of DM and digestible energy
were greatest for diets 2 and 3. Milk production, efficiency, and milk
CP production were not different among diets. Milk fat percentage and
production were increased by supplemental fat and decreased by high c
oncentrate. Contents of CP, true protein, and casein in milk were decr
eased by supplemental fat and increased by high concentrate, Digestibi
lity of fatty acids was decreased by either supplemental fat or high c
oncentrate. Concentrations of NEFA and somatotropin in plasma were inc
reased, and concentration of IGF-I was decreased, by supplemental fat;
NEFA, BHBA, and IGF-I were decreased by high concentrate. In vitro ra
tes of peroxisomal beta-oxidation and esterification of palmitate and
concentrations of total lipid and triglycerides in liver were not diff
erent among diets, but glycogen content was increased by high concentr
ate, The rate of total beta-oxidation of palmitate in liver slices ten
ded to be increased by supplemental fat; total metabolism of palmitate
was increased by supplemental fat and tended to be increased by high
concentrate. Supplemental fat may affect hepatic lipid metabolism in d
airy cows; effects of dietary fat during the periparturient period des
erve investigation.