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ABSTRACT

Two materials of nocturnal blood plasma samples, each representing more than 100 cows unselected with respect to health condition, showed acetoacetate variations within a wide range, overlapping with the range for animals with clinical ketosis. Within each of the two materials a statistically significant (P < 0.001) negative correlation (r = −0.30) was obtained between plasma corticosteroids and log acetoacetate.

The lowest corticosteroid and the highest acetoacetate averages were obtained for animals which were within the first month of the lactation cycle. With increasing time post-partum the two components varied inversely, a maximum in corticosteroids coinciding with a minimum in acetoacetate in cows which had calved 2½ to 3 months before the date of sampling. At this stage the mean plasma sugar was about 10 per cent higher than in early lactation.

The corticosteroid ranges for different levels of acetoacetate overlapped extensively. Still cows with acetoacetate ≤ 0.6 mg/100 ml gave significantly higher corticosteroid averages than the rest of the material. But in animals exceeding the 0.6 mg limit no relationship was found between the severity of the ketonaemia and the steroid level. Thus, no difference was obtained between cows with clinical ketosis and animals which were moderately ketonaemic.

Some change in adrenal function may be associated with the development of ketonaemic conditions in cows. But no proof has been provided of a direct adrenal involvement in the transformation of a case of subclinical ketosis to the clinical stage.

ABSTRACT

Two or three foetal lambs regularly result in a varying degree of carbohydrate shortage in mother ewes in late pregnancy. We have investigated the correlation between plasma insulin, growth hormone and energy substrate concentrations in ewes 8 and 1 weeks before lambing.

Plasma growth hormone was fairly constant (2–3 ng/ml) throughout the 24-h cycle 8 weeks before parturition. Seven weeks later higher average levels and increased diurnal fluctuations were observed in 3 out of 4 multiparous ewes. The average post-absorptive insulin levels were reduced by 50 per cent during the same interval. Simultaneously decreased post-absorptive sugar and increased acetoacetate levels were observed. It is concluded that the hormonal adaptations to the increasing carbohydrate deficit in late pregnancy, especially among multiparous ewes, include:

a) reduced post-absorptive plasma insulin levels,

b) reduced insulin responses to feeding, and

c) increased levels of growth hormone in the plasma.

ABSTRACT

Marked diurnal variations were found in plasma growth hormone (GH), insulin, acetoacetate (AcAc) and sugar in two herds (U and A) of dairy cows kept at two different levels of feeding. Seven animals from each herd were tested. The main diurnal variations were related to food intake, a significant increase in plasma insulin, and a significant decrease in plasma sugar being found. The acetoacetate level rose significantly during feeding in herd U (moderately underfed), while no significant increase was found in herd A (adequately fed). Plasma growth hormone was found to decrease (P < 0.01) only during feeding in herd U, while no change in the GH level could be detected in herd A. The mean level of GH in herd U was found to be twice the value found in herd A. There were no significant differences between the herds in plasma insulin and sugar.

Significant differences in plasma levels of GH, insulin and sugar were found between animals when analysed within the herds. Variations in the levels of insulin and acetoacetate were very small during the night. This is contrary to GH, which shows the least variation during food intake. The correlation coefficient between the plasma components was low, although in many cases significant.

ABSTRACT

Plasma progesterone concentration at different stages of pregnancy was measured in the blood obtained from the uterine artery (6 goats), the uterine vein (6 goats), and the ovarian vein (11 goats). Progesterone concentration was also measured in the peripheral venous blood before and after extirpation of the ovaries and the uterus (16 goats).

The concentration of progesterone was found to rise gradually in the peripheral and ovarian vein blood to reach a maximum at 90 days of pregnancy. This was followed by a gradual decline with consistent low values of about 7 ng prog./ml 3–4 days before parturition. A significant decrease in peripheral progesterone concentration was found 10 minutes after removing the ovaries and the uterus.

In two goats sampled before and after parturition, the plasma progesterone concentration was found to decrease before parturition and to remain low for at least three days after parturition.

ABSTRACT

Plasma growth hormone (GH) of eight young, sexually mature, pedigree bulls, observed at hourly intervals, varied during the day in a manner indicating intermittent secretion in peaks or bursts. The diurnal GH averages were about 10 ng/ml.

GH averages for 2–3 h intervals showed minima following or during the periods of morning and afternoon feeding. A third minimum occurred between 10 and 12 p.m. Peak activity, estimated by the frequency of GH values greater than 10 ng/ml was significantly reduced during two of these low-GH-periods (afternoon and late night).

The minima in GH followed after (morning) or coincided with (afternoon) maxima in plasma insulin (two materials, GH/insulin, 11 a. m.-10 p. m.: r=−0.31 and −0.34, P < 0.01). This means that the two hormones behaved after food intake much in the same ways as in man in spite of the fact that plasma sugar decreased after feeding (GH/sugar, 11 a. m.-10 p.m.: r = 0.27, two materials combined, P < 0.001).

The possibility of GH involvement in the hour-to-hour metabolic homoeostasis of the animals is discussed.

ABSTRACT

Nocturnal blood plasma samples from about 190 indoor-fed cows at varying stages of the lactation cycle showed wide variations in the concentrations of sugar (43–88 mg/100 ml) and acetoacetate (0.12–8.7 mg/100 ml). Plasma immunoreactive insulin decreased and acetoacetate increased with decreasing sugar.

Plasma growth hormone (GH) was significantly correlated to insulin (r = −0.24, P < 0.001) and to sugar (r = −0.15, P < 0.05), but not to acetoacetate (r = +0.13).

Since the plasma level of GH in bovines is known to vary widely from hour to hour, individual cows are poorly represented by single determinations of the hormone. However, in accordance with the results from the correlation tests, different GH averages, about 11 and 9 ng/ml, were found for groups of animals with plasma sugar respectively below and above 70 mg/100 ml. By subgrouping according to insulin levels within sugar ranges, categories could be singled out with GH averages as different as 12.7 ng/ml (low sugar - low insulin) and 8.3 ng/ml (high sugar - high insulin).

The findings are consistent with the view that GH is involved in the regulation of energy metabolism in bovines. But no support has been provided for the hypothesis of GH hypersecretion as a cause of ketosis in cows.

ABSTRACT

The pregnant ewe compensates the reduced carbohydrate availability in late pregnancy by increased fat combustion. The purpose of the present study was to examine the adaptation of plasma growth hormone (GH) and insulin levels to this change in energy substrate metabolism. Two groups of ewes were bled in the post-absorptive state at different stages of pregnancy. One group (7 animals) was fed adequately throughout pregnancy, while the other received a maintenance ration for non-pregnant sheep (28 animals).

Plasma GH increased from averages from 2–3 to 8–14 ng/ml during the last month before lambing. Shearing of the wool combined with a cold stress resulted in a clearly detectable peak in plasma GH in the underfed sheep. No significant difference in plasma GH attributable to differences in diet could be detected in late pregnancy.

Plasma insulin decreased steadily the last 5 weeks towards lambing, most in mothers with 3 lambs. Plasma free fatty acid levels (FFA) increased the last 2 months of pregnancy, most in the underfed sheep. GH and FFA were positively correlated (r = 0.50 and 0.30 in the two groups).

It is concluded that the adaptation of the maternal metabolism to reduced carbohydrate - and eventually energy-availability in late pregnancy included lowering of insulin and enhancement of plasma GH levels. These adaptations were detectable under the present conditions the last 5–6 weeks before term.