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Three experiments were conducted to compare sugarcane condensed molasses solubles (CMS), sugarcane molasses or a CMS—molasses mixture as ingredients in steer finishing diets, and to determine the effect of monensin in combination with CMS on ruminal volatile fatty acid production. In Experiments 1 and 2, 40 yearling steers were fed on a dry basis 0 or 5% CMS, 5% molasses or 5% of a CMS—molasses mixture (50% w/w fresh basis) for 67 and 96 days, respectively. Steers in Experiment 2 were all fed 33 g/metric ton of monensin. Average daily gain and dry feed conversion rate were, respectively, 0.89 kg and 9.61 in Experiment 1, and 1.28 kg and 6.14 in Experiment 2, with no differences among treatments. There were no treatment effects on carcass characteristics. Experiment 3 was a 2 × 2 factorial arrangement with 0 or 33 g monensin/metric ton fed to 40 yearling beef steers, in combination with 0 or 10% CMS (dry basis), for 134 days. In Experiment 3, 10% CMS decreased gain (P

Changes in mammary gland histology, dry weights, nucleic acids and in vitro rates of substrate oxidation in incorporation into lipid were measured in mammary biopsies of three gilts each on d 30, 45, 60, 75, 90, 105 and 112 of pregnancy, and d 1 and 4 of lactation. Histological changes noted were progressive duct growth early in pregnancy followed by rapid lobulo-alveolar development between d 75 and 90 to complete mammogenesis. Colostrum and lipid were evident by d 105 with marked distension of alveolar lumina on d 112. Complete differentiation of the secretory process was apparent on the day of parturition. Concentrtion of dry, fat-free tissue (DFFT) and DNA changed little before d 60 but increased fourfold between d 75 and 90. No further increases in DFFT or DNA were noted. RNA concentrations paralleled DNA through d 90, after which they steadily increased. Rates of acetate and glucose oxidation increased transiently during midpregnancy then declined and remained low until initiation of lactogenesis. Substrate incorporation into lipid increased slightly at midpregnancy and again at d 105, after which it increased markedly. Collectively, results indicate that mammogenesis is complete by d 90, after which lactogenesis is initiated in a two-stage process. Metabolic rates expressed on a DNA basis indicated considerable rates of oxidation, but not of lipogenesis by proliferating mammary tissue. Preferential metabolism of acetate vs glucose near parturition suggests coordination of metabolism between the mammary gland and other maternal tissues.