Medycyna Wet. 62 (6), 632-636, 2006
Nowak W., Jaśkowski J., Wylegała S. |
Effects of nutrition in the transition period on the fertility of milking cows |
The transition period, which begins 3 weeks before calving and continues until the 2nd week of lactation, is characterized by dramatic changes in the physiological, metabolic and endocrine status of dairy cows. The most important nutritional parameter affecting reproductive performance is the energy status of the cow during this period. A negative energy balance may influence endocrine status by decreasing the growth hormone (GH), insulin, insulin-like growth factor (IGF-I) and luteinizing hormone (LH) concentration in blood plasma which affects the development and function of follicles and corpora lutea. During the beginning of lactation dairy cows mobilize their fatty acids reserves, which increase the concentration of nonsterified fatty acid (NEFA) in the blood. Postpartum metabolic disorders during the transition period have been positively related to NEFA concentration in plasma. Lipid metabolism in the liver may contribute to health disorders and affect the fertility of high yielding dairy cows. Glucose synthesized in the liver from propionates and amino acids, plays a fundamental role in the metabolic status of transition cows. Glucose is the most important source of energy for reestablishing ovarian activity after calving. Adequate carbohydrate nutrition in the transition period focusing on increasing the availability of glucose and decreasing NEFA concentration is the main factor affecting the well being of dairy cows and influencing the profitability of milk production. Administrating feed additives during the transition period: propylene glycol, propionate, by-pass starch and ionophores, may increase the availability of glucose for cows during this time. |
Keywords: cows, transition period, NEFA, glucose, carbohydrates |