We investigated the composition of fatty acids in adipose tissue, serum, and liver of cows that were fed at restricted energy intake or were overfed during the dry period. Overfed cows had higher concentrations of serum nonesterified fatty acids and consequently accumulated greater amounts of triacylglycerols in the liver than did cows that were fed at restricted energy intake. The percentages of the different fatty acids present in adipose tissue were similar for both groups and did not change during sampling intervals. Before parturition, concentrations of the individual fatty acids present in serum were similar between groups. After parturition, concentrations of major fatty acids in serum, including palmitic, stearic, oleic, and linoleic acids significantly increased in both groups and were higher in overfed cows than in cows that were fed at restricted energy intake. The shift of concentrations of the different fatty acids present in the liver--as a result of increased lipolysis-was observed in palmitic, oleic, and linoleic acids but not stearic acid, suggesting that stearic acid is used by the liver (i.e., oxidation) or is considerably secreted through the milk, thereby not increasing in accumulation in the liver. In conclusion, different feeding regimens during the dry period do not influence the composition of fatty acids in adipose tissue. More intensive lipolysis results in increased concentrations of palmitic, stearic, oleic, and linoleic acids in the blood; subsequently, these fatty acids, excluding stearic acid, greatly accumulated in the liver.

-This review addresses the suggestion that the decline in dairy reproductive performance, as increasingly observed these days, may be due to a hampered process of metabolic adaptation in early lactating cows. In our opinion, adaptation to the negative energy balance is a gradual process. Because almost all cows do adapt in the long run, it is not possible to classify animals as adapted or non-adapted. The use of risk factors is more appropriate in this case and is discussed in this review. Among them are the body condition score and its derivatives, feed intake, the calculated negative energy balance, and metabolic parameters like the plasma concentration of insulin or the triacylglycerol content in the liver. Moreover, factors that play a role in the link between declined reproductive performance and the metabolic situation of the cow during the early lactating period are discussed. Among these are insulin, insulin-like growth factors, leptin, neuropeptide Y, nonesterified fatty acids, thyroïd hormones, urea, and ammonia. fertility / dairy / periparturient metabolic adaptation / physiopathology / periparturition

During the dry period, cows were either fed restricted amounts or were overfed to study lipolytic rates in adipose tissue. Higher lipolytic rates can result in greater accumulation of triacylglycerols in liver and, subsequently, hepatic lipidosis. Adipose tissue was biopsied at -1, 0.5, 1, 2, and 3 wk from parturition. The basal in vitro lipolytic rate was measured as well as the lipolytic rate as affected by the addition of noradrenaline, 3-hydroxybutyrate, or glucose. Liver was biopsied to quantify triacylglycerol concentrations. Blood was collected to determine insulin and nonesterified fatty acid concentrations. Basal in vitro lipolytic rates at -1 and 0.5 wk were lower in overfed cows. Lipolytic rate was enhanced in both groups of cows when noradrenaline was added, but rates at -1 and 3 wk tended to be higher in overfed cows than in cows that were fed restricted amounts. After the addition of 3-hydroxybutyrate or glucose in vitro, lipolytic rates tended to be higher in overfed cows. Liver triacylglycerol concentration was higher in overfed cows at 0.5 and 1 wk. Plasma insulin concentration tended to be higher in overfed cows at -1 wk. Plasma nonesterified fatty acid concentration was higher in overfed cows at 0.5 and 1 wk. Although overfeeding compared with restricted feeding did not significantly alter the in vitro lipolytic response to 3-hydroxybutyrate or glucose, adipose tissue from overfed cows tended to be less inhibited by these substances, which may contribute to higher lipolytic rates in vivo and a greater triacylglycerol accumulation in the liver after parturition.

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We investigated the activities of hepatic glycerolipid synthesizing enzymes during postpartum fatty liver development in 10 high-producing dairy cows that had free access to feed during the dry period; a parallel group of 8 control cows was fed according to recommended energy requirements. After calving, both test and control cows had free access to feed. In the period of 10-14 wk before calving, voluntary dry matter intake of the test cows was 20.6 kg/d (SEM 0.42); the restricted control cows received 7 kg/d. Postpartum triacylglycerol concentrations in liver biopsies were one- to twofold higher in the test than in the control cows. The higher plasma nonesterified fatty acid (NEFA) concentrations after parturition in the test vs. the control group were probably caused by a more negative energy balance in the test cows, which was associated with a slightly lower postpartum dry matter intake. After calving, hepatic mitochondrial glycerolphosphate acyltransferase (GPAT) activities were significantly lower in the test than in the restricted control cows. A low GPAT activity may divert fatty acids from esterification to beta-oxidation to protect the hepatocytes against further accumulation of triacylglycerols. The activities of hepatic phosphatidate phosphohydrolase, diacylglycerol acyltransferase, and cholinephosphate cytidylyltransferase were not different in the two groups. This study indicates that in cows given free instead of restricted access to feed during the dry period have a postpartum hepatic triacylglycerol accumulation that is mainly determined by a raised hepatic uptake of plasma NEFA.

The present study compared the hepatic fatty acid composition of cows that were fed a high energy diet during the dry period to induce fatty liver after parturition with that of control cows. Treated cows had higher concentrations of plasma nonesterified fatty acids as a result of greater lipolysis after parturition than did control cows; consequently, the treated cows accumulated greater amounts of triacylglycerols in the liver. Before parturition, treated cows had lower percentages of oleic acid and higher percentages of linoleic acid than did control cows, but percentages of other fatty acids were similar for both groups. After parturition, percentages of each fatty acid were changed substantially, particularly the four major fatty acids (palmitic, stearic, oleic, and linoleic acids). For treated cows, the percentages of palmitic and oleic acids were higher at 0.5 wk after parturition than at 1 wk before parturition; percentages of stearic and linoleic acids decreased. Unlike treated cows, the percentages of both oleic and linoleic acids in the control cows did not change during that time. Moreover, we found that when lipolysis decreased, as indicated by lower plasma nonesterified fatty acid concentrations, the percentages of each fatty acid gradually rebounded toward the concentrations measured before parturition; this observation indicates that the shift in hepatic fatty acid composition is influenced by lipolysis. The increased lipolysis after parturition led to a vast increase in the hepatic triacyglycerol concentration and to a shift in hepatic fatty acid composition.

The purpose of this study was to compare the hepatic enzyme activities of gluconeogenesis between control cows and experimental cows that had been overfed during the dry period to induce fatty liver postpartum. Blood and liver samples were collected 1 wk before and 0.5, 1, 2, and 3 wk after parturition. Before parturition, neither the serum nonesterified fatty acid nor the liver triacylglycerol concentration differed between the two groups. After parturition, these variables were higher in experimental cows than in control cows. Liver glycogen was higher at 1 wk before parturition in experimental cows; sharply decreased after parturition in both groups; and, at 1 wk after parturition, was lower in experimental cows than in control cows. In the liver, activities of phosphoenolpyruvate carboxykinase were significantly lower at 1 wk before and at 0.5 and 2 wk after parturition in experimental cows; in addition, the activities tended to be lower at 1 wk after parturition. Activities of fructose 1,6-bisphosphatase tended to be lower, but activities of glucose 6-phosphatase tended to be higher, at 0.5 wk after parturition in experimental cows than in control cows. Our results suggest that, in fatty infiltrated liver, the rate of gluconeogenesis is not optimal, which results in prolongation of lipolysis, particularly during the first weeks after parturition.

The in vitro rate of esterification of fatty acids in adipose tissue was compared between cows that were fed at restricted energy intake and cows that were overfed during the dry period. Subcutaneous adipose tissue was biopsied at -1, 0.5, 1, and 3 wk from parturition. The basal in vitro rate of esterification was quantified, as well as the rate of esterification after the addition of glucose or glucose plus insulin. The basal rate in adipose tissue from overfed cows at -1 wk was higher than in adipose tissue from cows that were fed at restricted energy intake and indicated enhanced storage of triacylglycerols in adipose tissue of overfed cows at that time. The rate of esterification after the addition of glucose or glucose plus insulin was increased in both groups at each sampling time, but the mean rates, expressed as a percentage of the basal rates, were lower for overfed cows than for cows that were fed at restricted energy intake at 0.5 and 1 wk. Although the addition of glucose or glucose plus insulin increased esterification rates in adipose tissue from both groups of cows, adipose tissue from overfed cows was less sensitive to the addition of these compounds. In conclusion, overfeeding during the dry period predisposed cows to accumulate fat in adipose tissue during the prepartum period. The smaller increase in esterification rate after the addition of glucose or glucose plus insulin in adipose tissue of overfed cows indicates a lower ability of the adipose tissue to esterify circulating fatty acids or to reesterify mobilized fatty acids, which, combined with higher rates of lipolysis postpartum, contributes to continuously elevated concentrations of circulating nonesterified fatty acids postpartum, leading to a more severe hepatic lipidosis in overfed cows.