Embryo

Impact of Dietary Fatty Acids on Oocyte Quality and Development in Lactating Dairy Cows

Abstract
The purpose of this study was to examine the effects of level of rumen inert fatty acids on developmental competence of oocytes in lactating dairy cows. Estrous cycles were synchronized in 20 cows on a silage-based diet supplemented with either Low (200g/d) or High (800g/d) Fat. A total of 1051 oocytes were collected by ultrasound guided ovum pick up (OPU) in 7 sessions/cow at 3-4 day intervals. Oocytes were matured, fertilized and cultured to the blastocyst stage in vitro. Embryo quality was assessed by differential staining of day-8 blastocysts. The High Fat diet reduced numbers of small and medium-sized follicles. There was no effect on the quality of oocytes (grades 1-4) or cleavage rate. However, High Fat significantly improved blastocyst production from matured (P<0.005) and cleaved (p<0.05) oocytes. Blastocysts from the High Fat group had significantly more total, inner cell mass and trophectoderm cells than the Low Fat group (P<0.05). Regression analysis showed negative effects of milk yield (P<0.001), dry matter intake (P<0.001), metabolisable energy intake (P<0.005) and starch intake (P<0.001) on blastocyst production in the Low Fat group, but not in the High Fat group. Within the Low Fat group, blastocyst production was negatively related to GH (P<0.05) and positively related to leptin (P<0.05). The Low Fat group had higher NEFA than the High Fat group (P<0.05). In conclusion, higher milk yields were associated with reduced developmental potential of oocytes in cows given a Low Fat diet. Provision of a High Fat diet buffered oocytes against these effects, resulting in significantly improved developmental potential.

Key words: Embryo • Follicular development • Lactation • Oocyte development • Ovum pick-up / transport

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