Abstract
ObjectiveAn experiment was conducted to determine the effect of reduced energy density of close-up diets on metabolites, lipolysis and gluconeogenesis in cows during the transition period.MethodsThirty-nine Holstein dry cows were blocked and assigned randomly to three groups, fed a high energy density diet (HD, 1.62 Mcal of net energy for lactation [NEL]/kg dry matter [DM]), a medium energy density diet (MD, 1.47 Mcal NEL/kg DM), or a low energy density diet (LD, 1.30 Mcal NEL/kg DM) prepartum; they were fed the same lactation diet to 28 days in milk (DIM). All the cows were housed in a free-stall barn and fed ad libitum.ResultsThe reduced energy density diets decreased the blood insulin concentration and increased nonesterified fatty acids (NEFA) concentration in the prepartum period (p<0.05). They also increased the concentrations of glucose, insulin and glucagon, and decreased the concentrations of NEFA and β-hydroxybutyrate during the first 2 weeks of lactation (p<0.05). The plasma urea nitrogen concentration of both prepartum and postpartum was not affected by dietary energy density (p>0.05). The dietary energy density had no effect on mRNA abundance of insulin receptors, leptin and peroxisome proliferator-activated receptor-γ in adipose tissue, and phosphoenolpyruvate carboxykinase, carnitine palmitoyltransferase-1 and peroxisome proliferator-activated receptor-α in liver during the transition period (p>0.05). The HD cows had higher mRNA abundance of hormone-sensitive lipase at 3 DIM compared with the MD cows and LD cows (p = 0.001). The mRNA abundance of hepatic pyruvate carboxykinase at 3 DIM tended to be increased by the reduced energy density of the close-up diets (p = 0.08).ConclusionThe reduced energy density diet prepartum was effective in controlling adipose tissue mobilization and improving the capacity of hepatic gluconeogenesis postpartum.
Highlights
The transition period, from 21 d before to 21 d after parturition, is the most stressful time in the production cycle of dairy cows because of depressed dry matter intake (DMI) and marked changes in metabolism that support late gestation, parturition and the onset of milk synthesis [1,2,3]
Blood metabolites and hormones The blood glucose concentration both prepartum and on the day of calving was not affected by the dietary energy density (p>0.05; Table 3)
The plasma urea nitrogen (PUN) concentration both prepartum and postpartum was not affect by dietary energy density (p>0.05)
Summary
The transition period, from 21 d before to 21 d after parturition, is the most stressful time in the production cycle of dairy cows because of depressed dry matter intake (DMI) and marked changes in metabolism that support late gestation, parturition and the onset of milk synthesis [1,2,3]. The DMI rather than milk yield is the major driver of NEB [4]. Nutritional management during the transition period designed to increase postpartum DMI may be a potential strategy to alleviate the negative effect of NEB on performance, as well as related metabolic disorders. Efficient gluconeogenesis is the major pathway used by dairy cows to maintain an adequate glucose supply to the mammary gland [5,6]. Mobilization of body fat reserves is the main way used to www.ajas.info
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