Feed intake is related to changes in plasma nonesterified fatty acid concentration and hepatic acetyl CoA content following feeding in lactating dairy cows

Abstract

The relationship between hepatic acetyl CoA (AcCoA) content and dry matter intake (DMI) was evaluated using 28 multiparous Holstein cows; 14 were early postpartum (PP; 12.6 ± 3.8 d in milk) and 14 were late-lactation cows (LL; 269 ± 30 d in milk). Cows were fed once daily, and DMI was determined for the first 4h after feeding. Liver and blood samples were collected before feeding and 4h after feeding. Feed intake over the 4-h period ranged from 3.7 to 9.6 kg of dry matter and was similar for the 2 stages of lactation. Before feeding, hepatic AcCoA content was greater for PP compared with LL cows (34.4 vs. 12.5 nmol/g), and decreased over the 4h after feeding for PP only (28.7 vs. 34.4 nmol/g). The range for change in AcCoA over the 4-h period was wide for both PP (-24.3 to 10.4 nmol/g) and LL (-5.7 to 16.1 nmol/g), and was related negatively to DMI at 4h for both PP (R(2) = 0.55) and LL (R(2) = 0.31). The reduction in plasma NEFA concentration over the 4-h period was greater for PP than LL cows (-681 vs. -47 µEq/L), and was related to DMI at 4h for both PP and LL (both R(2) = 0.38). Greater DMI among cows over the first 4h after feeding might have been from a sharper reduction in supply of AcCoA in the liver for oxidation during meals because of the reduction in plasma NEFA concentration. Consistent with this is that the change in AcCoA was positively related to the reduction in plasma NEFA concentration for PP cows (R(2) = 0.31). However, change in plasma NEFA concentration was not related to change in hepatic AcCoA in LL cows, indicating that the pool of AcCoA in LL cows is not as dependent on NEFA flux to the liver as that of PP cows. Further research is required to determine production and fate of AcCoA within the timeframe of meals and the effects of feeding on energy charge in hepatic tissue.

Review: Control of feed intake by hepatic oxidation in ruminant animals: integration of homeostasis and homeorhesis

“…Postprandial pulses of insulin interrupt the supply of fuels to the liver by stimulating the uptake of fuels by insulinsensitive tissues and inhibiting lipolysis in adipose issue. Consistent with this, feed intake over the first 4 h following feeding was highly variable among cows in the immediate postpartum period ranging from 3.7 to 9.6 kg and was positively related to the postprandial reduction of plasma NEFA concentrations which varied from 244 to 1158 μEq/l (Piantoni et al, 2015). Because the change in hepatic AcCoA concentrations was positively correlated with the change in plasma NEFA concentrations, the difference in DMI among cows was likely related to differences in the supply of AcCoA derived from β-oxidation of NEFA, consistent with the HOT.…”

“…Somatotropin concentrations gradually decline, decreasing milk yield and insulin resistance. Decreased milk production results in elevated plasma glucose and insulin concentrations, increasing the balance between lipogenesis and lipolysis, and decreasing plasma NEFA and hepatic AcCoA concentrations (Piantoni et al, 2015). Although NEFA is likely the dominant source of AcCoA for cows in the postpartum period when cows are in a lipolytic state, other fuels likely contribute to a greater extent when cows are in late lactation (Piantoni et al, 2015).…”

“…Decreased milk production results in elevated plasma glucose and insulin concentrations, increasing the balance between lipogenesis and lipolysis, and decreasing plasma NEFA and hepatic AcCoA concentrations (Piantoni et al, 2015). Although NEFA is likely the dominant source of AcCoA for cows in the postpartum period when cows are in a lipolytic state, other fuels likely contribute to a greater extent when cows are in late lactation (Piantoni et al, 2015). Plasma leptin concentrations increase with body condition (Bradford et al, 2006), limiting adiposity by direct effects on the CNS as well as by increasing plasma NEFA concentrations and the supply of AcCoA for hepatic oxidation (Allen, 2014).…”

Temporal effects of ruminal propionic acid infusion on feeding behavior of Holstein cows in the postpartum period

“…Meal size and frequency were not affected by rate of PA infusion in a similar experiment in our laboratory (Bradford and Allen, 2007a) likely because cows were later in lactation (51 DIM) and in a different physiological state. Propionate was more hypophagic for cows in the PP period than later in lactation (Oba and Allen, 2003b), likely because cows in the PP period are in a lipolytic state with greater availability of acetyl CoA for entry into the TCA cycle (Piantoni et al, 2015).…”

Highly fermentable starch at different diet starch concentrations decreased feed intake and milk yield of cows in the early postpartum period

“…Conflicting results of previous studies reported in the literature evaluating effects of diet starch concentration and fermentability are likely from interactions among diet starch concentration and fermentability, diet forage NDF (fNDF) concentration and duration of treatments. Propionate from ruminal fermentation of starch is a primary glucose precursor needed to restore euglycemia, but propionate can also suppress feed intake (Oba and Allen, 2003a;Bradford and Allen, 2007), especially for cows in the PP period that are in a lipolytic state (Oba and Allen, 2003a;Piantoni et al, 2015a). This suppression of feed intake has been linked to the stimulation of fuel oxidation in the liver by propionate, with hypophagic effects likely aggravated during the early PP period when cows increase mobilization of body reserves and acetyl CoA available for hepatic oxidation is increased (Oba and Allen, 2003b;Allen, 2012, 2013;Piantoni et al, 2015a).…”