Abstract
Abstract The objectives of the present study were to examine the fatty acid (FA) profiles in serum and in the follicular fluid (FF) and the association between polyunsaturated fatty acid level (PUFA) and follicular growth dynamics following induced luteolysis in dairy cows. A total of 29 dairy cows (CL>25mm, follicle≈15mm) at d0 (start of the experiment) were submitted to ultrasound guided transvaginal follicular aspiration for FF collection from the largest follicle and were injected with 500 μg of cloprostenol. The cows were subdivided into Group A1 (n=11) and Group A2 (n=8) resuming follicular growth either from a secondary follicle less than or larger than 8.5mm, respectively, present at the moment of aspiration and Group A0 (n=10) not resuming follicular growth. Follicular development was monitored daily by ultrasonography until the next dominant follicle reached ≈15mm and was subsequently punctured in Group A1 and A2 (d1). Serum and FF samples for FA determination were taken at d0 from all cows and at d1 in Group A1 and A2. No differences were observed between the FA profile in serum nor in FF between sampling days. Regarding the PUFA levels, the serum linoleic acid (C18:2n6) levels at d0 and d1 were significantly higher than in FF, while alpha linolenic acid (C18:3n3) was lower in the serum than in FF, both at d0 and d1. At d0, a tendency for negative correlation between serum and the FF C18:2n6 with subsequent daily follicular growth rate was observed, while, at d1 there was a strong negative correlation between the serum C18:2n6 and daily growth rate (r=−0.71; p=0.0006). The present study revealed similarities of the FA profiles in the serum and in the FF and association between serum and FF PUFA content with the follicular dynamics after induced luteolysis.
Highlights
In the last decades, an intensive genetic selection for higher milk production has inevitably contributed to declining fertility in dairy cows [1]
The current study aimed to examine the correlation between FA profiles in the serum and the follicular fluid in cows fed a lactation diet without any fat supplementation and to investigate if the polyunsaturated fatty acid level (PUFA) fatty acid concentrations (C18:2n6 and C18:3n3) are associated with the follicular growth dynamics in dairy cattle after a single PGF2α injection
The results of the present study show that linoleic acid (C18:2n6) was the principal fatty acid constituting about half of the total amount of fatty acids in the serum and about a third of the total fatty acid concentration in the follicular fluid followed by palmitic acid, stearic acid and oleic acid, respectively
Summary
An intensive genetic selection for higher milk production has inevitably contributed to declining fertility in dairy cows [1]. Several studies have shown a strong negative relationship between high milk production and fertility [2, 3]. Any alterations in the components of the plasma and granulosa and theca layers will be reflected in the follicular fluid [16]. In this respect, it has been shown that alterations in the diet that increase the serum FA, especially PUFA levels, cause considerably greater infiltration of these FA into the follicular fluid [17]. Increased PUFA concentrations (C18:3n3) have been shown to decrease PGF synthesis [19], which
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