BACKGROUND: Omega-3 fatty acids can be conducive toreducing the harmful effects of physiological stress through reducing the stimulatory activity of glutamatergic neurons.OBJECTIVES: The aim of this study was to investigate the effects of omega-3 fatty acids on performance, blood parameters, and the profile of fatty acids in the egg yolks of laying hen under stress.METHODS: This study was performed using 96 LSL-Lite laying hens in a 2 × 3 factorial experiment with 2 factors, namely stress (no dexamethasone and 1.5 mg/kg of diet dexamethasone) and omega-3 fatty acids (the levels of 0, 0.24 and 0.48 % of diet), in a completely randomized design for 70 days from 35 to 44 weeks of age.RESULTS: Physiological stress reduced the feed intake, the percentage of egg production, and egg mass in laying hens (P<0.05). Omega-3 fatty acid supplements had no effects on these traits. The groups receiving 0.48 % of omega-3 fatty acids had the lowest heterophil:lymphocytes (P<0.05), and there was no difference between stressed and non-stressed groups. The ratio of omega-6 to omega-3 fatty acids was higher in birds previously affected by stress (P<0.05). Feeding with omega-3 fatty acids in birds increased omega-3 fatty acids in egg yolk and reduced the ratio of omega-6 fatty acids to omega-3 in laying hens (P<0.05).CONCLUSIONS: Based on the results of this experiment, physiological stress had a negative effect on performance traits, and the use of omega-3 fatty acids in laying hens under stress had no effect on performance traits. Physiological stress altered the profile of fatty acids and increased the proportion of omega-6 to omega-3 fatty acids in egg yolk. The use of omega-3 fatty acids reduced the negative effects of stress and improved the profile of fatty acids in egg yolk.

BACKGROUND: Application of different sources of fatty acids and their effect on ovarian performance is a current issue in animal science and research centers. OBJECTIVES: The purpose of this study was to determine the effect of different fatty acids in close-up period on population and size of follicles and measuring blood parameters related to the energy state of the body after calving of lactating dairy cows. METHODS: In this study 15 Holstein cows were selected by expected date of parturition (around 30 days before calving) and assigned them randomly within treatments diets. The diets were formulated to be isonitrogenous. Cows were fed 1) control (carbohydrate source), 2) Rumen-protected fat (RF) (saturated fatty acids) and 3) Roasted Soybean (RS) (unsaturated fatty acids). Blood sample was collected at 7 day intervals in -21, -14, -7, 1, 7, 14, 21 periods of calving. Also dry matter intake and body condition score cows were recorded. Ovarian activity was monitored by daily transrectal ultrasound scanning from 30 to 40 and 61 to 70 DIM. RESULTS: Average plasma glucose and cholesterol concentration were significantly different among treatment groups. Numerically, follicular classes were higher in cows, fed with fat diet compared with control group. CONCLUSIONS: According to the results of this experiment, it seems that application of polyunsaturated fatty acids, to improve the energy and ultimately the function of the ovaries, has more advantage than saturated fatty acids.