Role of insulin in the development of metabolic and reproductive malfunctions of periparturient dairy cows
Year: 2009
Type: dissertation
Abstract: In dairy cows selected for high milk production theperiparturient insulin resistance \n(IR) may play a pivotal role both in adaptation to the energy demands of milk synthesis \nand in the pathogenesis of some metabolic malfunctions and organic diseases related to \nthe negative energy balance (NEB). Insulin is the most important anabolic hormone with \nsignificant functions in carbohydrate, lipid and protein metabolism, which acts to \nmaintain body depots and to prevent ketogenesis. Moreover, insulin is one of the key \nmetabolic molecules which mediate the crosstalk between the hypothalamic-ovarian axis \nand the body energy state. In humans the release ofcytokines, that occurs in association \nwith obesity and inflammatory diseases (especially in those with endotoxemia), and the \nrelease of non esterified fatty acids plays an important role in the development of IR. In \ndairy cow inflammatory diseases with intensive endotoxin/cytokine release (puerperal \nmastitis and metritis, clinical endometritis) are frequent complications in the puerperal \nphase. Our understanding on the relationship between periparturient metabolic disorders, \ninsulin resistance and the poor reproductive performance in the modern dairy cow is \nlimited, yet. \nOur goal was to investigate the periparturient insulin pattern and IR in high lactating \ndairy cows in relation with some metabolic and reproductive malfunctions and to improve \npostpartum ovarian function through energy supplementations in cows under different \nmanagement systems. \nWe showed that pancreatic ß-cell function and the biological potency of insulin is \nimpaired in cows with long-term hyperketonemia. Short-term elevations in plasma free \nfatty acids and ketone bodies may not potentially induce further increase in peripheral \ntissue insulin resistance in the early lactation. However, severe inflammatory diseases like \npuerperal metritis may potentially further depress insulin secretion of the pancreatic ß-cells and the whole body insulin responsiveness of dairy cows, with long-term effects on \nmetabolism and reproduction. Furthermore we also found that the revised quantitative \ninsulin sensitivity check index (RQUICKI) as was assessed earlier only in healthy \nanimals should be applied with cautions in the assessment of insulin sensitivity in dairy \ncows in different physiological and disease states (Exp. 1). We found that top-dressing of \npulverized propylene glycol (PGL) on the total mixed ration from d 14 before calving till \nd 10 after calving was not effective in improving metabolic profile, insulin sensitivity, the \ntime of first postpartum ovulation and pregnancy rate. Most probably the relatively good \nenergy balance of the animals involved in our studylimited the effectiveness of the \nsupplement. However, the method of allocation and the absorbent incorporated for the \nPGL product used in the present study contributed to the inefficacy (Exp. 2). In contrast, \nin lean cows, which were kept under pasture condition, the pre-partum supplementation \nwith cracked corn grain improved the energy balance, peripheral insulin concentrations \nand decreased the time to the first pp ovulation. (Exp. 3).It is obvious that the \neffectiveness of periparturient energy supplementation is greatly dependent on the initial \nenergy state of the animals. \nWe hope that our results contribute to our understanding on dairy cow physiology and \nhelp to choose appropriate dietary tools in improving metabolic and reproductive \nperformance.
Source: Hungarian Veterinary Archive
Author: Ágnes Mónika Kerestes
Language: English
Subfield: Animal Science and Zoology
Domain: Life Sciences
Open Access status: green
Funder: Szent István Egyetem
OpenAlex ID: W2301292673