Lipid metabolism in finishing bulls and steers implanted with oestradiol-17 β-dipropionate

Abstract

ABSTRACTTwenty bull calves were assigned to one of four treatment groups: 1) intact bulls; 2) intact bulls implanted with oestradiol dipropionate; 3) steers, and 4) steers implanted with oestradiol dipropionate. Subcutaneous adipose tissue was obtained by biopsy 5 months after implantation. Experimental treatment did not alter (P> 0·05) mean adipose cell volume, diameter or cell number per g adipose tissue. Soluble protein content of adipose cells from bulls was increased by implantation, but not in steers.In vitrorates of fatty acid synthesis were higher in oestrogen-implanted cattle compared with nonimplanted cattle when expressed per g adipose tissue, but not when expressed per cell. Maximal activities of the lipogenic-related enzymes, acetyl coenzyme A carboxylase, adenosine triphosphate-citrate lyase, aconitate hydratase and NADP-isocitrate dehydrogenase were higher in implanted compared with nonimplanted cattle when the activities were expressed per g tissue and acetyl coenzyme A carboxylase and aconitase were also higher when expressed per adipose cell. Bulls and steers had the same basal and stimulated lipolytic rates and implantation of oestradiol dipropionate had no effect on either basal or stimulated lipolytic rate. In this experiment, the oestrogenic implant appeared to have a stimulatory effect onin vitroestimates of lipogenesis.