Corticosteroids in nocturnal blood plasma of cows in the field related to stage of lactation and plasma acetoacetate

Prefeeding plasma acetoacetate and glucose in healthy, lactating heifers. Variations related to milk yield, metabolic balances and stage of lactation

When measured before morning feeding plasma acetoacetate (ACAC) increased and glucose (GL) decreased significantly with increasing milk yield (fat corrected, FCM) within 2 groups of half-sister related heifers which did not suffer from clinical ketosis. The groups received respectively A: 7 kg and B: 4 kg/d of concentrates in addition to grass silage ad libitum (each group 88 animals). Correlation coefficients of the same magnitude between the 3 variables mentioned were obtained in the 1st and 3rd month of lactation in spite of a narrowing of the ACAC range from 0.024-0.66 to 0.019-0.16 mmol/l. Reproducibility of differences between animals in milk yield and in the plasma components was evidenced by significant correlations between measurements in the 1st and 3rd month. The B-animals produced 2.4 kg/d less FCM than the better fed A group (A, 1st month of lactation 19.8 +/- 3.1 kg/d) while the mean values for ACAC and GL remained practically unaffected by the difference in feeding. B cows gave consistently 5-6% lower GL means (p < 0.01) than A animals with identical yields. Animals which showed marked ACAC increment during the first 5-6 weeks of lactation produced 3-4 kg more FCM/d than equally fed animals with constantly low ACAC levels. The estimated energy deficit of this ketonaemic, high-producing category corresponded to the production of 4.5-6 kg FCM/d from body reserves. Low ACAC values (< 0.05 mmol/l) were reproduced with a standard deviation of +/- 4% with the automated nitroprusside method described.

Etiology of acetonemia in Norwegian cattle. 2. Effect of butyric acid, valeric acid, and putrescine

A feeding experiment was performed on 16 cows in order to test the effect of naturally occurring substances in silage on forage intake, ketonemia, and milk yield. The cows were divided into a control group and three experimental groups. The cows in the three experimental groups were fed 100 g/d of putrescine, 200 g/d of valeric acid, or 200 g/d of butyric acid through a ruminal tube for 3 d. Butyric acid increased plasma acetoacetate; the effect was largest in high yielding cows. Putrescine influenced both milk yield and forage intake and may possibly be a contributory factor, alone or combined with other amines, for the development of ketonemia. Valeric acid did not influence feed intake or plasma acetoacetate concentration. A rapid method for acetoacetate analysis also is described.

Etiology of acetonemia in Norwegian cattle. 1. Effect of ketogenic silage, season, energy level, and genetic factors

Plasma acetoacetate concentration in the 1st mo of lactation and its relation to BW change, milk yield, DMI, and BW postpartum were studied in 361 first lactation cows during 6 yr. The cows were fed concentrate at 6 and 3 kg/d. Calvings took place from August to December. Single observations for all cows were fitted by a multitrait animal model that accounted for all genetic relationships. Heritability for acetoacetate was .11 with a genetic correlation of .87 for milk yield, -.65 for weight change, and -.13 for BW postpartum. Acetoacetate was higher at 3 kg/d of concentrate than at 6 kg/d, and calving after 3 to 4 mo of indoor feeding was related to higher acetoacetate than was calving shortly after the pasture season. Acetoacetate was related to weight loss postpartum, but at a different degree in different years. In some years, compounds of the silage caused strongly elevated plasma concentrations of acetoacetate after feeding. Experiments were performed to compare hay with silages of different qualities. Rumen concentration of different amines 3 h postfeeding was taken as an index of the amine load of the cow. The concentration of several amines in rumen fluid were high after feeding ketogenic silage.

Ketosis treatment and milk yield in dairy cows related to milk acetoacetate levels

Milk yield and milk acetoacetate (M-acac) were measured weekly for the first 6 weeks of lactation in 5 herds with a ketosis problem. Ketosis treatments and the corresponding ketotest score, were also recorded. The treatment rate was highest 7-16 days after calving. Most of these early cases were associated with low ketone levels in milk, whereas the treatment rate for cows with high ketone levels was highest 17-31 days after calving. Nearly half of the treated cows were low-ketone animals. They were classified as ketosis cases in the cow health card records, although probably suffering from other post partum disturbances in many instances. About 40% of the cows with high ketone levels recovered spontaneously. Reduction in milk yield associated with peak M-acac levels was transient and moderate. It was concluded that health card statistics overestimates the severity of the ketosis problem in Norway.

Plasma glucose, ketone bodies, insulin, glucagon and enteroglucagon in cows: diurnal variations related to ketone levels before feeding and to the ketogenic effects of feeds

Ingestions of a moderately ketogenic silage twice daily were followed by transient increments in plasma insulin and ketone bodies and decreases in plasma glucose. Ketone bodies and glucose were negatively correlated throughout the day, but the insulin elevations culminated before the maximal effects on ketone bodies and glucose were established. Cows with varying glucose levels before morning feeding reacted to a highly ketogenic silage by decreasing their glucose level uniformly to about 3 mmol/l, in spite of a widely varying feeding-induced insulin increment. Hay-feeding caused insulin increments of the same magnitude as silage-feeding, but the glucose decrease and the ketone increment was much smaller. The results indicate some direct action of ketone bodies on blood sugar regulation, in addition to effects mediated by insulin. The role of ketone bodies as the insulinotropic factor was not confirmed. The insulin level after feeding seems to be determined by the carbohydrate status of the animal before feeding. No significant changes in plasma glucagon were observed after feeding, and no consistent differences in plasma levels of this hormone were found when non-ketonemic, ketonemic, and clinically ketotic cows were compared. The plasma level of enteroglucagon (GLI) was positively correlated to the relative amount of concentrates consumed, but no relation to plasma glucose was found.

Variations in parameters of liver function and plasma progesterone related to underfeeding and ketosis in a dairy herd

Twenty-eight Norwegian Red Cattle dairy cows were fed silage ad libitum and restricted amounts of concentrates. Blood samples were collected before morning feeding, once or twice weekly, from 2 weeks before to 12 weeks after calving. Parameters of liver function, carbohydrate status and fertility were recorded in order to assess their interrelationships. Eight cows were treated for clinical ketosis. Four of these had to be treated 2 or 3 times. Aspartate aminotransferase and bilirubin showed the highest within-animal coefficients of correlation with acetoacetate. Analysis of variance revealed a significant effect of carbohydrate status (indicated by plasma acetoacetate levels) on the levels of aspartate aminotransferase, glutamate dehydrogenase and sorbitol dehydrogenase, though only a small part of the total variation was explained by this factor. The estimated volume density of liver fat in the 4th week of lactation averaged 6.0 +/- 6.4% (+/- SD) ranging from 0.1-25.1%. Liver fat content at this stage of lactation was not significantly correlated with other indicators of liver function or carbohydrate status. Cows treated for clinical ketosis had significantly lower plasma progesterone values at the time of first ketosis treatment than untreated multiparous cows. The frequency of high progesterone values (greater than 3 ng/ml) being significantly lower in treated than in untreated cows during the period from 3-5 weeks post partum, though not at later stages. In conclusion, the results revealed a significant relationship between carbohydrate status and liver function, and also between clinical ketosis and luteal function.

Diurnal and individual variations in bile acids in the plasma of normal dairy cows

Blood samples were collected every 2 h during a 24 h period from 6 cows of one herd and 10 cows of another herd. In a third herd 9 cows were sampled every 2 h from 6 a.m. to 8 p.m. Concentrations of total bile acids, acetoacetate, glucose and free fatty acids were determined in blood plasma. A marked difference in individual bile acid concentrations and patterns of diurnal variation was found. For most cows the highest bile acid values were observed between 2 and 6 a.m. (overall mean (+/- SD) at 6 a.m.: 104 +/- 84 mumol/l, range: 20-307 mumol/l). Fourteen cows with a bile acid value greater than 90 mumol/l at 6 a.m. ("high BA") were characterized as a group by showing a pronounced decrease in the mean bile acid concentration after morning feeding. In the group of 11 cows with a 6 a.m. bile acid value less than 90 mumol/l ("low BA") the time of day did not contribute significantly to the bile acid variation. For the "high BA" group a nearly synchronous variation between the mean values of the 3 feeding dependent parameters (acetoacetate, glucose and free fatty acids) and the mean values of bile acids was found. The within animal coefficients of correlation between bile acids and the feeding dependent parameters were significantly higher in the "high BA" group than in the "low BA" group. No direct connection was found between bile acid levels and the quantity of concentrates fed or the individual milk yield.

Insulin secretion in lactating cows: responses to glucose infused intravenously in normal, ketonemic, and starved animals

Changes in insulin concentrations of blood plasma were studied in lactating cows during and after a 1-h intravenous glucose infusion in 5 spontaneously ketonemic, 10 nonketonemic (normal), and 4 starved cows. A biphasic increase in insulin with a maximum 10 to 20 min after the start of the glucose infusion was followed by a sustained (1 to 2 h) elevation in the normal and ketonemic animals. In starved cows only the later phase was detectable. Insulin was higher in normal than in starved and ketonemic cows during both phases of the insulin secretion in spite of approximately identical glucose. Differences between starved and ketonemic cows were not major. Average rates of decline in sugar concentrations after the end of the infusion were higher in normal and ketonemic [half times 143 +/- 23 (standard deviation) and 166 +/- 22 min] than in starved cows (281 +/- 47 min). The low basal insulin of plasma and poor responses of insulin secretion following glucose infusions indicate sluggish beta-cell function in ketonemic cows.

Maintenance of lactose secretion during acute insulin deficiency in lactating goats

Induction of alloxan diabetes in 5 lactating goats resulted in reduced milk yields in 3 of the animals, while the yield was unchanged in two. After treatment of the diabetic goats with insulin for 4--5 days--the last 24 h intravenously--lactose secretion returned to the control values before alloxan administration provided that normoglycemia developed. In 2 experiments infusion of a large dose of insulin caused hypoglycemia and a 20--30 per cent reduction in lactose secretion rates. In the course of 1 h after withdrawal of the insulin infusion, patent signs of insulin deficiency developed as evidenced by steadily increasing plasma glucose concentrations. Nevertheless, lactose secretion continued at the same rate as during insulin infusion for the 4 h studied after discontinuation of the insulin infusion. In the goats where lactose secretion was reduced due to insulin-induced hypoglycemia, lactose secretion returned to control values when following discontinuation of insulin infusion the plasma glucose concentrations increased into normal and diabetic ranges. It is concluded that during insulin deficiency of short term duration, mammary lactose secretion was maintained at a normal rate. Since lactose is the major product of mammary glucose utilization, it is suggested that glucose uptake in the mammary gland was not reduced by short term insulin deficiency.