Adipose tissue metabolism and production responses to calcium propionate and chromium propionate.

The objective was to determine action of calcium propionate and chromium propionate on lipogenesis and lipolysis in adipose tissue, dry matter (DM) intake, milk production and composition, and serum glucose and free fatty acids in Holstein dairy cattle treated from 21 d prepartum to 35 d postpartum. Twelve multiparous animals were assigned to each treatment: control (C), calcium propionate (CaP, 0.125 kg/d), chromium propionate (CrP, 10 mg of trivalent Cr/d), and both. All animals were switched to control at 36 days in milk (DIM) and the trial continued to 90 DIM. Biopsies of adipose tissue were taken at -7, 14, 28, and 56 d from calving. Control intake prepartum was 10.6 +/- 2 kg/d. Calcium propionate increased DM intake 11% prepartum and 13% postpartum; CrP increased DM intake 7 and 16%; and the combination treatment had no effect. Milk yield was 44.2 kg/d for controls and 46.8 kg/d for d 1 to 90 for CrP-treated cows. Adipose tissue lipogenesis in cows treated with either CaP or CrP was 1.25 to 78 times as fast as controls from 14 to 56 d and had returned to prepartum rates by 56 d. From 14 to 28 d, basal lipolysis in CaP- or CrP-treated cows ranged from 27 to 102% of control, whereas stimulated lipolysis was 61 to 113% of control. Milk fat yield was 92 to 95% of control on calcium and chromium propionate; the difference was similar to the net reduction in adipose lipolysis. Milk lactose, protein, and solids-not-fat did not differ among treatments. Providing a small amount of gluconeogenic precursors may reduce net lipolysis, allowing increased feed intake and milk production. The effect is thought to be through chromium acting to increase glucose flux into adipocytes.