The effect of two different routes of administration of oxytocin on peripheral plasma prostaglandin F(2α) metabolite levels in early post-partum dairy cows.

Various parenteral treatment forms of oxytocin, as often used under praxis circumstances, may act differently on contractility of the uterus during the first days of the puerperium. Various patterns of such induced uterotonic responses may lead to alterations in the emptying characteristics of the uterine lumen, thus influencing, as a late consequence, the process of involution. Therefore, this study was designed to test whether two different parenteral administration forms of oxytocin induce changes in peripheral plasma concentrations of 15-ketodihydro-prostaglandin F(2α) (PGF(2α) metabolite) in early post-partum cows. Between 13 and 15 h after uncomplicated calving, healthy dairy cows without retained foetal membranes were treated with 50 IU oxytocin, either intramuscularly (OT-IM group; n = 15) or intravenously (OT-IV group; n = 16). Saline solution was administered intramuscularly as controls (CON group; n = 15). Jugular blood samples were taken at 10-min intervals from 1 h before to 2 h after treatment. Plasma PGF(2α) metabolite levels were measured by radioimmunoassay. No significant differences in peripheral plasma PGF(2α) metabolite concentrations occurred in the OT-IM and CON groups, but mean values significantly increased in the OT-IV group, peaking at 20 min after treatment and reaching pre-treatment baseline values again at 120 min. Although the source of prostaglandins was not investigated in this study, our results suggest that exogenous oxytocin may enhance secretion of prostaglandins by the uterus during the first day after normal calving. These prostaglandins might contribute, by an endocrine or paracrine route, to the stimulation of myometrial contractility when exogenous oxytocin is given during this early post-partum stage.

Effects of a non-starch polysaccharidase enzyme preparation from Thermomyces lanuginosus on energy and protein metabolism and milk yield of dairy cattle.

Non-starch polysaccharides (NSPs) form an integral part of the cell walls in plants and represent considerable available energy when degraded into absorbable mono-, di-, tri- and oligosaccharides. The ruminal microflora hydrolyses a good part of NSPs, however, recently there have been attempts to enhance the rate of utilisation by using external polysaccharidase enzymes. In the present study the effects of an enzyme preparation (Rumino-Zyme) high in xylanase activity were studied on ruminal volatile fatty acid (VFA) concentration, parameters of energy and protein metabolism, milk yield, feed conversion ratio (FCR) and body condition score of high-yielding dairy cows. A lignolytic enzyme preparation produced by the thermophilic fungus Thermomyces lanuginosus was applied in the present experiment and fed to dairy cows at 34 g/day dosage in the period between calving and the 110th day of lactation. This preparation increased VFA concentration in the rumen from about 32 days after calving and onward. Increased VFA concentration was followed by an about 5 to 10% increase in milk production and an almost 0.1% increase in butterfat production. Increased VFA concentration produced more balanced energy metabolism in the experimental cows as indicated by the lower incidence rate of hyperketonaemia, and lower acetoacetic acid and non-esterified fatty acid (NEFA) concentration in the blood of the experimental cows. Aspartate aminotransferase (AST) activity was tendentiously higher in the control group and the proportion of cows that had AST activity higher than 100 U/l was also higher in the control group. Both control and experimental cows showed balanced protein and acid-base metabolism throughout the experiment. Enhanced VFA concentration contributed to an improvement in energy balance in the experimental cows with a resultant improvement of feed intake and feed utilisation. Due to the more balanced energy metabolism postparturient body condition loss of the treated cows was reduced.

Comparison of blood ionized calcium and acid-base variables in samples obtained from different sampling sites in dairy cows.

Ionized calcium (Ca2+) concentrations, pH, blood gas tensions (pCO2 and pO2), base excess (BE), and bicarbonate (HCO3-) concentrations were determined and standard ionized calcium (stCa2+) concentrations were calculated (Ca2+ corrected to pH 7.4) for the blood withdrawn from the jugular vein, the coccygeal vein or coccygeal artery and the milk vein in 29 clinically healthy post-partum dairy cows. The blood withdrawal site had no significant effect on the blood ionized calcium and standard ionized calcium (mean differences among the blood samples varied between 0.01 and 0.05 mmol/l), or on bicarbonate concentrations or base excess. pH, pCO2 and pO2 were significantly lower or higher in samples taken from the coccygeal vein compared to other venous blood samples.

Correlation between thyroid hormone level and blood pH in cows and in their offspring.

Thyroid hormone levels in the plasma and blood pH were compared in 38 newborn calves and their dams immediately at parturition, then 24 and 72 h thereafter. Both thyroid hormone levels and pH exhibit much higher variation in calves than in cows. Applying a linear model at different sampling times, a weak (r = -0.112 to -0.397) but significant (P less than 0.05) negative correlation was found between thyroid hormone levels and blood pH in calves 24 and 72 h postpartum. At birth, when no correlation was found with linear approach, a polynomial regression model showed curvilinear relationship between thyroid hormone levels and blood pH in calves. Since these correlations could not be substantiated by comparing data of different sampling times, one can conclude that the possible relationship of thyroid hormone levels and blood pH is a complex one. Revealing the underlying mechanism of the above observations requires further study.