Twenty-four-hour patterns of hormones and metabolites in week 9 and 19 of lactation in high-yielding dairy cows fed triglycerides and free fatty acids.

Effects of feeding crystalline triglycerides (TGA), free fatty acids (FFA), and a starch-rich ration (STA) on metabolite and hormone concentrations in blood plasma were studied in high-yielding dairy cows over a 24-h period in week 9 and 19 of lactating. Energy-corrected milk production in the three groups was similar, but was lower in week 19 than in week 9. Energy and protein intakes were greater in week 9 than in week 19, but energy and protein balances in the three groups and in weeks 9 and 19 were similar. Plasma glucose and triglyceride concentrations were lower in week 9 than in week 19. In cows fed FFA, glucose concentrations were highest in week 9. Plasma triglyceride, phospholipid and cholesterol concentrations were highest, whereas beta-hydroxybutyrate concentrations were lowest in FFA-fed cows in weeks 9 and 19. Concentrations of insulin-like growth factor-I in week 19 were lower in cows fed TGA and FFA than in those fed the starch-rich ration. Post-prandial responses were usually greater following morning than afternoon meals. Fructosamine, albumin, urea, growth hormone, thyroxine, and 3,5,3'-triiodothyronine concentrations were similar in weeks 9 and 19 and were not influenced by dietary treatment or feeding times. In conclusion, there were distinct metabolic and endocrine effects of feeding TGA and FFA compared with STA and the concentrations as well as the 24-h changes of various metabolic and endocrine traits in weeks 9 and 19 of lactation were also different.

Insulin-dependent whole-body glucose utilization and insulin-responses to glucose in week 9 and week 19 of lactation in dairy cows fed rumen-protected crystalline fat or free fatty acids.

Whole-body insulin-dependent glucose utilization and insulin responses to glucose in euglycemic-hyperinsulinemic clamps (EHGC) and in hyperglycemic clamps (HGC) were evaluated in high yielding dairy cows fed rumen-protected fat (triglycerides), free fatty acids, or a starch-rich ration (n = 5 per group) in Week 9 and Week 19 of lactation. The experiment was performed under conditions of nonsignificant differences in energy and protein balances in Week 9 and Week 19 and in the three groups. Basal (pre-infusion) concentrations of glucose were lower (P < 0.05) in Week 9 than in Week 19 of lactation and were higher (P < 0.05) in Week 9 in cows fed free fatty acids than in cows fed the starch-rich ration. In EHGC, glucose infusion rates were similar in Week 9 and Week 19 and in the different groups, indicating similar insulin-dependent glucose utilization. Furthermore, because insulin concentrations in EHGC in Week 9 and Week 19 and in the three groups were very similar, metabolic clearance rates of insulin were not affected by stage of lactation and feeding. In addition, insulin responses to the same glucose increments in HGC were not different in Week 9 and Week 19 and in the three groups, indicating that insulin secretion was not affected by stage of lactation and feeding. In conclusion, insulin secretion, insulin metabolic clearance rate, and insulin-dependent glucose utilization between Week 9 and Week 19 of lactation were stable. Furthermore, feeding rumen-protected triglycerides or free fatty acids did not significantly modify insulin secretion, insulin metabolic clearance rate and glucose-dependent glucose utilization compared with starch-rich feeding.

Insulin-like growth factor I absorption in the jejunum of neonatal calves.

The absorption of recombinant human insulin-like growth factor I(rhIGF-I), [125I]rhIGF-I, xylose and [3H]lysine, administered into a clamped jejunal segment in anesthetized neonatal calves, was studied by measuring their appearance in the mesenteric vein draining the gut segment. Only trace amounts of IGF-I and of [125I]rhIGF-I and/or 125I were absorbed following dissolution in saline, buffer or colostrum. The absorption rate of both [3H]lysine and/or 3H and of xylose was much greater than the absorption of rhIGF-I, [125I]rhIGF-I and/or 125I but was also transient. Biological effects of ingested IGF-I in neonatal calves should barely occur as a consequence of intestinal absorption even in 1-day-old calves, known to absorb various peptides and proteins.

Immunoreactive insulin-like growth factor I and insulin in blood plasma and milk of mares and in blood plasma of foals.

Concentration of (total) globulin was relatively stable in blood plasma of mares, but rapidly decreased in colostrum to very low levels within 2 days after parturition. In foals, after intake of the first colostrum, globulin increased within 1 day in blood plasma, but remained at lower concentrations than those measured in mare plasma. Concentrations of immunoreactive insulin (iI) were high during the first 2 months of lactation in blood plasma of mares and then decreased, were high in first colostrum and then decreased drastically, and remained at low concentrations up to weaning in blood of foals. In mares, concentration of immunoreactive insulin-like growth factor I (iIGF-I) in plasma increased during late pregnancy, peaked 2 days after parturition, and then gradually declined until weaning. iIGF-I was highest in first colostrum and then dramatically decreased within the first 2 days of lactation. In foals, iIGF-I gradually increased over the first 2 months of life. IGF-I in the horse appears to be bound to proteins of similar molecular weight as in cattle. The study demonstrates different patterns of changes in plasma iIGF-I and iI concentrations in mares and their foals, whereas iI, iIGF-I and globulin changes in colostrum and milk occurred in parallel. Furthermore, plasma iI and iIGF-I behaved differently, while colostrum iI and iIGF-I behaved similarly, in mares compared with dairy cows.

[Postprandial plasma variations of 3-methylhistidine compared to those of lysine, homoarginine and xylose on the normal conditions and in malabsorption in the suckling calf]. / Variations plasmatiques postprandiales de 3-méthylhistidine comparée à celles de lysine, d'homoarginine et de xylose dans des conditions normales et en cas de malabsorption chez le veau pré-ruminant.

We have studied the absorption of 3-methylhistidine (3MH) in vitro and changes in its plasma concentration in preruminant calves after ingestion of milk containing 3MH under normal and malabsorptive conditions. Changes in 3MH concentration were compared to those in lysine, homoarginine (as a component of guanidinated caseine) and xylose, also added to milk. The absorption of 3MH in vitro was dose-dependent and was inhibited by leucine, indicating that 3 MH was transported in the same manner as neutral amino acids. After the ingestion of milk supplying 2.5-20 mumols (3MH)/kg body weight, 3MH increased dose-dependently within 1.75 h and reached maximal levels between 3 and 8 h. Lysine concentration initially parallelled the course of blood 3MH levels but dropped sooner. Homoarginine concentration did not increase until 2-4 h postprandially, probably as a consequence of the time needed for casein degradation. Xylose concentration increased as rapidly as 3MH and lysine concentration. Feeding a diet containing soybean protein for 36 d and administration of neomycine for 5 d to newborn calves induced malabsorption of xylose. However, 3MH absorption and caseine digestion, which increased after homoarginine absorption were not reduced.