Nikica Prvanović

The influence of late pregnancy and lactation on bone metabolism in mares.

Pregnancy and lactation are periods of significant influence on bone metabolism that has not been investigated in equines. To examine the influence of late pregnancy and lactation on bone metabolism in mares, the changes in the blood serum/plasma total calcium (Ca), inorganic phosphates (Pi), pyridinoline (Pyd) and 17beta-estradiol (E2) concentration and the bone alkaline phosphatase (BAP) activity were investigated. The samples were taken from 11 mares on 60+/-10 and 20+/-10 days before foaling, and 20+/-10 and 60+/-10 days after foaling. The concentration/activity of Ca, Pi, Pyd and BAP increased significantly in early lactation, but the Pyd than decreased in the 4th period. A significant correlation was observed between the E2 and bone metabolism parameters. The results indicate low maintenance of normocalcaemia with reduced bone synthesis in late pregnancy and prove the role of estradiol in bone metabolism in mares during pregnancy and lactation.

Serum fructosamine concentrations in relation to metabolic changes during late pregnancy and early lactation in mares.

The changes in blood serum fructosamine concentrations as indicators of glycaemia during a longer period of time were investigated in mares during late pregnancy and early lactation, as well as their relationship to the changes in the concentration of biochemical indicators of energetic status. The samples were taken from eleven mares on 60 +/- 10 and 20 +/- 10 days before foaling, and 20 +/- 10 and 60 +/- 10 days after foaling. Concentrations of serum fructosamine, non-esterified fatty acids and triglycerides were higher during late pregnancy (from P < 0.05 to P < 0.0005), while the concentrations of beta- hydroxybutyrate increased significantly (P < 0.00001) during early lactation. A significant correlation between the concentrations of fructosamine and metabolic parameters was observed. The results indicate a relationship between energetic status and serum fructosamine in mares. Higher concentrations of fructosamine are related to the adaptation to late pregnancy. Therefore, the measurement of the serum fructosamine concentrations could serve as an indicator of energetic status of mares during pregnancy and lactation.

The influence of age on bone metabolism in mares during late pregnancy and lactation.

The concentrations of carboxyterminal cross-linked telopeptide of type I collagen (CTx), osteocalcin (OCN), parathyroid hormone (PTH) and insulin-like growth factor (IGF-I) were measured in the blood serum of two age groups of mares during late pregnancy (70-50 days before foaling), during early lactation and at the peak of lactation (10-30 and 55-80 days after foaling, respectively). During late pregnancy, the PTH was higher in older (8-19 years old), compared to younger animals (3.5-4 years old) (P < 0.05). The OCN was higher in younger group during late pregnancy (P < 0.05). IGF-I was higher in the younger group during early lactation, in comparison to late pregnancy and the peak of lactation (P < 0.05). IGF-I did not differ between two age groups of mares. The results indicate on the differences in adaptation of bone metabolism to late pregnancy and lactation in older animals, in comparison to younger animals, reflected by elevated PTH secretion.

Progesterone and Insulin-Like Growth Factor I Levels in Blood of Boer Goats During Puerperium Out-of-Season in a Mild Climate Region

The aims of this study were to compare insulin-like growth factor-I (IGF-I) and progesterone concentrations as indicators of cycle activity in the blood of Boer goats during puerperium out-of-season in mild climate conditions and to investigate the influence of parity and litter size on the concentration of IGF-I and progesterone in serum during the study period. Twenty Boer (8 primiparous and 12 pluriparous) goats were examined in this study. Blood samples were taken every 4 days starting on the 3rd day and up to the 40th day of puerperium. IGF-I and progesterone (P4) blood levels were determined using radio immune assay (RIA). Results indicated cyclic ovarian activity outside the breeding season in 18 of 20 Boer goats. IGF-I levels in blood sera followed oestrus and cyclic ovarian activity. IGF-I concentrations correlated significantly with P4 concentrations. The IGF-I peak preceded the P4 peak by approximately 8 days in cycling goats. IGF-I and P4 blood levels were not influenced by parity or litter size. Changes in blood serum P4 and IGF-I concentrations levels during puerperal period can assist in the evaluation of reproductive status of goats.

The efficacy of milk ejection induced by luteal oxytocin as a method of early pregnancy diagnostics in cows

The aim of this research was to determine the accuracy and reliability of early diagnosis of pregnancy in cows using PGF2α analogue. Namely in the case of corpus luteum (CL) presence, the release of luteal oxytocin is induced by intravenous administration of a non luteolytic dose of PGF2α. The research was performed in 30 lactating cows, 18-22 days after insemination, and three hours prior to evening milking. A teat cannula is placed in the left fore-teat. When the cisternal milk flow ceased, Dinoprost (256 μg Dinolytic) was injected in the v. jugularis. If CL was present, the alveolar milk flow (559.4±83.7 mL) started 189±18 s later and early pregnancy could be presumed. If CL was no longer functional, the milk flow did not start again and the cow was considered not pregnant. Seventeen out of 30 cows were confirmed pregnant 35 days after insemination by ultrasound and 13 were found not pregnant. The accuracy of positive results is 100% and is identical to that obtained by ELISA of milk progesterone used as a reference method. The accuracy of negative results was lower (46.1% vs. 84.6%) (p<0.05), because seven out of 13 non pregnant cows has responded to the milk ejection test. In spite of this disadvantage, the test approved as being inexpensive, rapid, and easy to interpret and is therefore very applicable, especially under field conditions. It can be applied i.e. 20 days after insemination. Progesterone rapid test from milk or by milk ejection test can be used with similar accuracy.