Studies on hepatic lipidosis and coinciding health and fertility problems of high-producing dairy cows using the "Utrecht fatty liver model of dairy cows". A review.

Fatty liver or hepatic lipidosis is a major metabolic disorder of high-producing dairy cows that occurs rather frequently in early lactation and is associated with decreased health, production and fertility. A background section of the review explores reasons why high-producing dairy cows are prone to develop fatty liver post partum. Hepatic lipidosis and coinciding health and fertility problems seriously endanger profitability and longevity of the dairy cow. Results from a great number of earlier epidemiological and clinical studies made it clear that a different approach was needed for elucidation of pathogenesis and etiology of this complex of health problems. There was a need for an adequate animal model in which hepatic lipidosis and production, health and fertility problems could be provoked under controlled conditions. It was hypothesized that overconditioning ante partum and feed restriction post partum might induce lipolysis in adipose tissue and triacylglycerol accumulation in the liver following calving. This consideration formed the basis for the experiments, which resulted in the "Utrecht fatty liver model of dairy cows". In this model, post partum triacylglycerol-lipidosis as well as the whole complex of health and fertility problems are induced under well-controlled conditions. The experimental protocol based on this hypothesis produced in all cases (10 feeding trials with over 150 dairy cattle) the intended result, i.e. all experimental cows developed post partum higher hepatic triacylglycerol concentrations than did control cows. The model was evaluated in biochemical, clinical pathology, immunological, clinical and fertility terms. It turned out that in this model, post partum triacylglycerol-lipidosis as well as the whole complex of health and fertility problems were induced under well-controlled conditions.

Associations between energy metabolism, LH pulsatility and first ovulation in early lactating cows.

This study was designed to elucidate associations between energy metabolism and LH pulsatility characteristics in early lactation, and days to first ovulation, in order to explain the relationship between energy balance and fertility observed in epidemiological studies. To this end, 10 multiparous HF cows were monitored during lactation, after the application of two different feeding strategies during the dry period. Days to first ovulation was assessed using blood progesterone measurements and LH pulsatility was measured in 8-h windows in the third week postpartum. The association between depth of negative energy balance and days to ovulation was confirmed. However, this study does not support the idea that LH pulsatility characteristics in early lactation are predictive for the interval between parturition and first ovulation.

Unrestricted feed intake during the dry period impairs the postpartum oxidation and synthesis of fatty acids in the liver of dairy cows.

The purpose of this study was to determine the activities of key hepatic enzymes of fatty acid synthesis and oxidation in cows that had excessive body fat at parturition. Dairy cows were allocated to either an experimental group or a control group. All cows were offered a total mixed ration with an energy content of 6.6 MJ of net energy for lactation per kilogram of dry matter and consisting of corn silage, beet pulp, rapeseed meal, and soybean meal. Control cows were restricted to 6.8 kg/dry matter of the mixed ration in the dry period. Experimental cows had unrestricted access to the mixed ration during the dry period to increase body fat and induce fatty liver postpartum. Blood and liver samples were collected 1 wk before and 1, 2, and 4 wk after parturition. Before parturition, neither the serum nonesterifled fatty acids nor the hepatic triacylglycerol concentrations differed between experimental and control cows. After parturition, the values for these variables were greater in experimental cows than in control cows. Plasma 3-hydroxybutyrate increased sharply after parturition in the experimental group. In liver, the activity of acetyl-CoA carboxylase was already significantly lower in the experimental group before parturition. After parturition, the activities of acetyl-CoA carboxylase and fatty acid synthase dropped in the experimental group. The activity of 3-hydroxy-acyl-CoA dehydrogenase in liver was less in experimental cows following parturition. Hepatic citrate synthase activity increased only in the control group after parturition. Unrestricted feed intake before parturition reduces de novo fatty acid synthesis as well as fatty acid oxidation after parturition. The reduction in fatty acid oxidation following parturition may contribute to postpartum accumulation of triacylglycerol in the livers of cows with unrestricted access to feed during the dry period.

[Serum gammaglobulin titer in goat kids after colostrum administration: effect of commercial colostrum replacers]. / Serumgammaglobulineconcentratie van geitenlammeren als maat voor biestvoorziening: effect van commerciële biestvervangers.

Seven commercially available colostrum replacers were tested for their ability to substitute for goat colostrum as a source of gammaglobulin for goat kids. One hundred kids were fed with goat colostrum or colostrum replacer after separation from their mothers at birth. Blood samples were taken from ten kids at birth, and from all kids at 48 hours after birth. Samples were used to measure the total protein content and gammaglobulin concentration of serum. Kids fed with goat colostrum had higher gammaglobulin concentrations than newborn kids or kids fed with replacer. For three replacers, the gammaglobulin concentrations were the same as those of newborn kids. For three other replacers, the gammablobulin concentrations were similar but higher than those of newborn kids. For one replacer, the levels of gammaglobulin were higher than those of in newborn kids and higher than those measured after feeding of the other replacers. None of the replacers was an adequate substitute for goat colostrum as a source of gammaglobulins.

Apparent fat digestibility in rats fed different diets is negatively correlated with faecal bile acid excretion.

Seventy-two rats were fed one out of 9 diets differing as to protein source and calcium concentration. For the individual rats apparent fat digestibility and faecal bile acid excretion were negatively correlated. It is suggested that a high solubility of bile acids in the small intestinal digesta, which is associated with little loss of bile acids with faeces, stimulates the process of fat digestion.

High density lipoprotein cholesteryl ester metabolism in the pony, an animal species without plasma cholesteryl ester transfer protein activity: transfer of high density lipoprotein cholesteryl esters to lower density lipoproteins and the effect of the amount of fat in the diet.

The metabolism of high density lipoprotein cholesteryl esters (HDL CE) was studied in the pony, an animal species without plasma cholesteryl ester transfer protein (CETP) activity. Studies were done in ponies fed a low- (1.5% fat, w/w) and a high-fat diet (11.5%, w/w fat). The ponies fed the high-fat diet had higher plasma HDL CE concentrations (1.08+/-0.15 vs. 0.84+/-0.11 mmol/l, mean+/-S.D., n=6, P<0.01) and plasma lipoprotein lipase (LPL) activities (14.3+/-4.0 vs. 5.7+/-3.4 micromol free fatty acids (FFA)/ml per h, P<0.05) than those on the low-fat diet. Plasma triacylglycerol (TAG) concentrations were lower on the high-fat diets (0.129+/-0.043 vs. 0.180+/-0.050 mmol/l), but these differences were not statistically significant. There was a negative correlation between the levels of plasma TAG (r=0.598, P<0.05) and VLDL CE (r=0.658, P<0.05) on the one hand and the HDL CE concentrations on the other hand. The transport rates of HDL CE were not significantly different between ponies fed high-fat (0.029+/-0.008 mmol HDL CE/h per l plasma) and those fed low-fat diets (0.024+/-0.004). HDL CE were transferred to low density lipoproteins (LDL) and we calculated that the percentage of LDL CE derived from HDL was 0.69+/-0.13 in the ponies fed the low-fat diet and 0.53+/-0.05 in the ponies fed the high-fat diet (P<0.05). The results of these in vivo studies suggest that in ponies, similarly as reported in rats and pigs, HDL CE can be transferred to LDL despite the absence of plasma CETP activity, and that the magnitude of this transfer is related to the levels of HDL CE as induced by the amount of fat in the diet.

Altered functional and immunophenotypical properties of neutrophilic granulocytes in postpartum cows associated with fatty liver.

The intention of the study was to analyze the relationship between liver triacyl glycerol content (liver TAG content) and immunophenotypical and functional properties of polymorphonuclear neutrophilic granulocytes (PMN) of dairy cows in the peripartum period. We investigated characteristics of bovine PMN from the blood and uterus of clinically healthy cows in the periparturient period. The numbers of circulating leukocytes and segmented granulocytes continuously increased until parturition and declined afterwards to starting values. This was independent of the liver TAG content and mainly affected neutrophils. The liver TAG content exceeded 40 mg/g liver, the reference value, in 12 of 19 cows in the first two weeks postpartum. Increased liver TAG content, > 40 mg/g, went in parallel with a reduced expression of function-associated surface molecules on blood neutrophils (e.g. CD11b/CD18 = CR3 and CD11c/CD18 = CR4). Moreover, in cows with high liver TAG levels the antibody-independent and -dependent cellular cytotoxicity (AICC, ADCC) of blood PMN was markedly reduced. PMN also were less capable of ROS generation after stimulation with Phorbol Myristate Acetate (PMA). In comparison with contemporarily harvested blood PMN, neutrophils recovered from the uterine lumen showed a decreased expression of 4/6 examined surface structures. Only the expression densities of CR3 molecules and those detected by mAb IL-A110 were enhanced on uterine PMN. The cytotoxic capacity and the ROS generation were significantly lower for uterine PMN than for blood PMN. The results suggest that increased liver TAG content in the first and second week after calving is associated with decreased functional capacities of PMN derived from blood and uterus. This may help to explain why cows who are too fat at calving (who therefore have an increased liver TAG content) have a higher incidence of infectious diseases such as endometritis

Using serum amyloid A to screen dairy cows for sub-clinical inflammation.

In this study, 232 lactating dairy cows from six herds were observed for clinical signs of inflammation and simultaneously had blood samples drawn to determine whether or not Serum Amyloid A (SAA) was present. Serum protein electrophoresis and white blood cell differential count revealed inflammation in SAA+ samples but not in SAA-samples. Using positive SAA test results as the standard for presence of inflammation, clinical findings consistent with inflammation concurred with positive SAA results only 26% of the time (p<.001) while the lack of clinical signs consistent with inflammation concurred with negative SAA results 95% of the time (p<.001). There was also a significant difference (p<.005) in management styles in that cows permanently fed on wilted/cured forages and kept inside had a 26% prevalence of positive SAA blood samples whereas the overall prevalence of SAA+ samples was 16%. These findings indicate that whole herd screening using SAA can be of value to the veterinarian in helping to identify cows with inflammatory diseases. From a public health perspective, SAA testing of cows going to market can help differentiate those not needing intensive inspection from those that do.

Urinary concentration of corticoids in ponies with hyperlipoproteinaemia or hyperadrenocorticism.

The urinary corticoid:creatinine (c:c) ratio was determined in ten pony mares suffering from hyperlipoproteinaemia. The mean (+/- sd) urinary c:c ratio of these ten ponies (47 +/- 31 x 10(-6)) was not significantly different from that of twelve pony mares with a pituitary pars intermedia adenoma (31 +/- 18 x 10(-6). The correlation between the urinary concentration of corticoids and plasma total lipids, and the correlation between the urinary c:c ratio and plasma total lipids in ponies with hyperlipoproteinaemia were not significant (P > 0.05; r = 0.53 and r = 0.008, respectively). Preliminary results favour primary hyperadrenocorticism being associated with hyperlipoproteinaemia. In conclusion, the data presented here suggest that cortisol can contribute to insulin resistance in ponies with hyperlipoproteinaemia.

Interrelation of fatty acid composition in adipose tissue, serum, and liver of dairy cows during the development of fatty liver postpartum.

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.

[Serum gamma globulin concentration in goat kids after colostrum administration: effect of time of administration, volume and type of colostrum]. / Serumgammaglobulineconcentratie van geitenlammeren als maat voor biestvoorziening: effect van toedieningstijdstip, volume en biesttype.

In this study, which was performed on a Dutch dairy goat farm, several aspects of the administration of colostrum to new-born goat kids were examined. Time of colostrum administration and amount and type of colostrum administered were compared. Effectiveness was measured as total serum protein content and gamma globulin fraction. No significant differences in serum gamma globulin titre were observed between kids that received colostrum at 30 or 60-90 minutes post partum, respectively. Titres were significantly lower in kids that received 100 ml of colostrum instead of 150-200 ml. The effect of sheep colostrum replacer or cow colostrum was also examined. Gamma globulin titres were significantly high with goat colostrum than with cow colostrum or sheep colostrum replacer, and titres were higher with cow colostrum than with sheep colostrum replacer. Based on the results of this experiment, the following protocol is suggested for colostrum administration to goat kids: single administration of 150-200 ml of goat colostrum within 90 minutes of birth. Use of cow colostrum is not advised because it may lead to transmission of paratuberculosis. Use of sheep colostrum replacer as a source of passive immunity is not recommended.

High calcium intake lowers apparent digestibility of energy in veal calves.

Veal calves aged 8 weeks were fed iso-energetic amounts of milk replacers with either a low (7.1 g of calcium/kg of air-dry diet) or a high concentration of calcium (11.6 g of calcium/kg of air-dry diet) for a period of 10 weeks. The extra calcium was added in the form of calcium formiate. Final body weight of the two dietary groups was similar. Faeces were collected during the final week of the trial. The high calcium diet raised faecal dry matter output by 87% and faecal energy by 70%. The extra output of faecal dry matter was composed of 36% and 37% of crude fat and ash, respectively. The extra faecal energy output was for 75% in the form of crude fat. The high versus low calcium intake not only depressed apparent digestibility of total lipids but also that of crude protein, carbohydrates and ash. It is concluded that a high calcium intake by veal calves reduced energy availability without affecting body weight gain.

Insulin resistance: the link between metabolic disorders and cystic ovarian disease in high yielding dairy cows?

A preliminary investigation was performed to examine whether insulin resistance is a factor in the pathogenesis of cystic ovarian disease (COD) in high-yielding dairy cows. In total 30 cows, of which 15 were diagnosed as suffering from COD based on the anamnesis and clinical examination, and the other 15 served as matched controls, were subjected to an intravenous glucose tolerance test (IVGTT). The aim of the study was to investigate whether insulin activity was altered in COD cows. Differences in glucose clearance between the COD cows and their controls were analyzed comparing the fractional turnover rate (k), the glucose half-time (T1/2), and the area under the curve (AUC) 60 and 120 min after infusion. Differences in insulin response were analyzed comparing the insulin increment, the insulin peak concentration, and the AUC 60 and 120 min after glucose infusion. Although insulin resistance, attended by a secondary hyperinsulinemia, is stated to directly contribute to the ovarian abnormalities that characterize the polycystic ovary syndrome (PCOS) in human medicine, this was not observed in COD cows. On the contrary, COD cows appeared to have a low insulin response following an intravenous glucose load as compared with their matched controls. This was illustrated by significantly lower insulin increments (P = 0.04) and lower insulin peak concentrations (P = 0.04). As COD cows had a significantly lower insulin response to a standard glucose load, it was concluded that insulin could be a factor in the pathogenesis of COD in dairy cows.

Effect of overfeeding during the dry period on the rate of esterification in adipose tissue of dairy cows during the periparturient period.

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.

Relationship between overfeeding and overconditioning in the dry period and the problems of high producing dairy cows during the postparturient period.

In dairy cows, overfeeding during the dry period leads to overcondition at calving and to depression of appetite after calving. As a consequence, at calving overconditioned high-producing dairy cows inevitably go into a more severe negative energy balance (NEB) postpartum than cows that have a normal appetite. During the period of NEB, the energy requirements of the cow are satisfied by lipolysis and proteolysis. Lipolysis results in an increased concentration of non esterified fatty acids (NEFA) in the blood. In the liver, these NEFA are predominantly esterified to triacylglycerols (TAG) that are secreted in very low density lipoproteins (VLDL). In early lactation in cows with a severe NEB, the capacity of the liver to maintain the export of the TAG in the form of VLDL in balance with the hepatic TAG production is not always adequate. As a result, the excess amount of TAG accumulates in the liver, leading to fatty infiltration of the liver (hepatic lipidosis or fatty liver). The NEB and/or fatty liver postpartum are frequently associated with postparturient problems. In general, a severe NEB induces changes in biochemical, endocrinological, and metabolic pathways that are responsible for production, maintenance of health, and reproduction of the postparturient dairy cow. These changes include a decrease in blood glucose and insulin concentrations, and an increase in blood NEFA concentrations. High NEFA concentrations caused by intensive lipolysis are accompanied by impairment of the immune system, making the cows more vulnerable to infections. Metabolic diseases such as ketosis, milk fever, and displaced abomasum are related to overcondition at calving. The changes in biochemical, endocrinological, and metabolic pathways are associated with delay of the first visible signs of oestrus, an increase in the interval from calving to first ovulation, a decrease in conception rate, and a prolonged calving interval. It is possible that the increased blood NEFA concentration directly impairs ovarian function.

Reduced lymphoid response to skin allotransplants in cows with hepatic lipidosis.

The immune responsiveness of cows with hepatic lipidosis (fatty liver) in comparison to control cows with a normal liver fat content was tested by applying skin allotransplants to the skin of the back of cows on day 3 after parturition. Immunoreactivity was determined by semiquantitative counting of the number of infiltrating lymphocytes in the recipient skin adjacent to the allotransplants during a period of 21 days. There were more invading lymphocytes in samples from control cows than there were in samples from cows with hepatic lipidosis. It was concluded that cows with hepatic lipidosis have a reduced lymphoid response to skin allotransplants.

Effect of fatty liver on hepatic gluconeogenesis in periparturient dairy cows.

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.