Metabolic Effects of Abomasal l-Carnitine Infusion and Feed Restriction in Lactating Holstein Cows

Abstract

L-Carnitine is required for mitochondrial fatty acid oxidation, but the effects of carnitine supplementation on nutrient metabolism during dry matter intake depression have not been determined in dairy cows. Studies in other species have revealed responses to L-carnitine that may be of specific benefit to dairy cows during the periparturient period. Eight lactating Holstein cows (132 +/- 36 d in milk) were used in a replicated 4 x 4 Latin square experiment with 14-d periods. Treatments were factorial combinations of abomasal infusion of either water or L-carnitine (20 g/d; d 5 to 14) and either ad libitum or restricted intake (50% of previous 5-d dry matter intake; d 10 to 14) of a balanced lactation diet. Liver and muscle biopsies were obtained on d 14 of each period. Feed restriction induced negative balances of energy and metabolizable protein. In feed-restricted cows, carnitine infusion increased 3.5% fat-corrected milk yield compared with those infused with water. Total carnitine concentration in liver was increased in feed-restricted cows infused with carnitine but not in feed-restricted cows infused with water. Carnitine infusion stimulated in vitro oxidation of [1-(14)C] palmitate to acid-soluble products and decreased the proportion of [1-(14)C] palmitate that was converted to esterified products by liver slices. Feed-restricted cows infused with carnitine had lower liver total lipid concentration and tended to have decreased triglyceride accumulation compared with feed-restricted cows infused with water. Plasma nonesterified fatty acid concentration was not altered by carnitine infusion but was increased by feed restriction; serum beta-hydroxybutyric acid was increased by carnitine infusion in feed-restricted cows. In cows fed for ad libitum intake, carnitine infusion affected beta-hydroxybutyric acid, insulin, and urea N in serum, liver glycogen concentration, and in vitro alanine oxidation by liver slices, suggesting that hepatic and peripheral nutrient metabolism was influenced. L-Carnitine infusion effectively decreased liver lipid accumulation during feed restriction as a result of greater capacity for hepatic fatty acid oxidation. Further research examining dietary supplementation of L-carnitine during the periparturient period is warranted.

Composition of major proteins in cow milk differing in mean protein concentration during the first 155 days of lactation and the influence of season as well as short-term restricted feeding in early and mid-lactation

“…As intended, feed restriction during early and mid-lactation led to a reduced energy intake, but resulted in no significant change in energy balance in both LP-and HP-cows. Milk yield was slightly lower compared to previous results after a 50% restriction of DMI over 5 days in mid-lactation (-11 kg;Carlson et al, 2006) and a 40% nutrient restriction during 4 days (-10 kg; Bjerre-Harpøth et al, 2012). In LP-cows, the decrease in milk yield was significant due to higher milk yields before the restricted feeding in early and mid-lactation.…”

Liver fat content and lipid metabolism in dairy cows during early lactation and during a mid-lactation feed restriction

“…However, data on fatty liver in mid-and late-lactating dairy cows can be rarely found in the literature. Contrary to our findings, feed-restricted dairy cows (around 132 DIM) in the study of Carlson et al (2006) had an increase in liver TG content. Those authors found that feed restriction did not affect the rate of palmitate oxidation or the proportion of palmitate oxidized.…”

“…Nevertheless, cows mobilized body reserves to a comparable extent to early lactation, as indicated by a decrease in BCS and back fat thickness (Gross et al, 2011a). In the later lactational stage, dairy cows seem to react less intensely to a NEB regarding NEFA and BHBA concentration, as shown in feed-restricted mid-lactation dairy cows (Carlson et al, 2006). The lower BHBA concentrations in period 2 can be explained as a consequence of the lower plasma NEFA levels.…”

Feed restriction, but not l-carnitine infusion, alters the liver transcriptome by inhibiting sterol synthesis and mitochondrial oxidative phosphorylation and increasing gluconeogenesis in mid-lactation dairy cows

“…Therefore, the main objective of this study was to determine the extent to which abomasal l-carnitine infusion and acute DMI restriction alter gene expression patterns in liver and how those alterations are linked with in vitro rates of lipid metabolism. Other portions of data from the animals used for the current study have already been reported (Carlson et al, 2006).…”

“…The activity and expression of carnitine palmitoyltransferase-I (CPT-I), the mitochondrial enzyme for which l-carnitine serves as a cofactor, increases around parturition to facilitate oxidation of mobilized NEFA Loor et al, 2005). Supplemental l-carnitine has shown potential to decrease or prevent liver triacylglycerol (TAG) accumulation in feedrestricted dairy cows (Carlson et al, 2006) and laboratory animals (Bykov et al, 2003;Spaniol et al, 2003).…”