Nutrition, Metabolism, and Fertility in Dairy Cows: 2. Dietary Fatty Acids and Ovarian Function

• Published in: Journal of dairy science Vol. 91; no. 10; pp. 3824 - 3833
• Main Authors: Garnsworthy, P.C., Lock, A., Mann, G.E., Sinclair, K.D., Webb, R.
• Format: Journal Article
• Language: English
• Published: Savoy, IL Elsevier Inc 01.10.2008; American Dairy Science Association; Am Dairy Sci Assoc
• Subjects: Animal Nutritional Physiological Phenomena; Animal productions; Animals; Biological and medical sciences; blood plasma; Body Weight - physiology; Cattle - metabolism; Cattle - physiology; dairy cow; dairy cows; Diet - veterinary; dietary fat; Dietary Supplements; Eating - physiology; energy balance; experimental diets; fatty acid; fatty acids; Fatty Acids - metabolism; Feeding. Feeding behavior; Female; female fertility; Fertility - physiology; Fundamental and applied biological sciences. Psychology; glucagon; hormone secretion; Hormones - blood; insulin; Lactation - physiology; metabolism; Milk - secretion; milk yield; nutrition physiology; ovarian follicles; ovarian function; ovaries; Ovary - physiology; plasma insulin to glucagon ratio; Random Allocation; Regression Analysis; ruminant nutrition; Terrestrial animal productions; Vertebrates; Vertebrates: anatomy and physiology, studies on body, several organs or systems; fatty acid; dairy cow; insulin; ovarian function; Farming animal; Nutrition; Dairy cattle; Lipids; Metabolism; Fatty acids; Insulin; Vertebrata; Mammalia; Fertility; Dairy industry; Artiodactyla; Ungulata
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2008-1032

Plasma insulin has important implications for ovarian function in dairy cows. Previous work demonstrated that plasma insulin increased with increasing dietary starch and decreasing dietary fatty acid concentrations. The objective of this experiment was to investigate hormonal and ovarian responses to dietary fatty acid content with no change in other dietary components. Thirty cows were fed a standard diet from calving until 40 d in milk (DIM) and then 6 cows were transferred to each of 5 diets containing 0, 8, 15, 23, and 30 g/kg of dry matter (DM) of calcium salts of palm fatty acids (CaPFA; Megalac) until 70 DIM. Estrus was synchronized at 60 DIM. Between 60 and 70 DIM, energy intake, milk yield, and energy balance were similar among diet groups. Plasma insulin decreased when dietary concentration of CaPFA exceeded 15 g/kg of DM (insulin: 0.46, 0.41, 0.46, 0.33, 0.28±SE 0.034 ng/mL for diets containing 0 to 30g of CaPFA/kg of DM, respectively). Maximum plasma insulin to glucagon ratio was observed with 15g of CaPFA/kg of DM (ratios: 3.99, 4.33, 4.67, 3.45, 2.89±SE 0.156 for diets containing 0 to 30g of CaPFA/kg of DM, respectively). Plasma concentrations of growth hormone, insulin-like growth factor-I and leptin did not vary between diets. The number of small (<5mm) ovarian follicles was negatively related to plasma insulin concentration (r = −0.328) and was stimulated by CaPFA supplementation at all rates tested compared with cows receiving zero CaPFA (small follicles preovulation: 6.7, 11.2, 11.5, 11.3, 11.9±SE 1.48 for diets containing 0 to 30g of CaPFA/kg of DM, respectively). The number of medium-sized follicles, and diameters of the ovulatory follicles and corpora lutea, were not affected by CaPFA supplementation. It is concluded that dietary total fat concentration should be below 50 g/kg of DM to avoid depressing plasma insulin concentration in cows at the start of the breeding period.