Effects of glucogenic and ketogenic feeding strategies on splanchnic glucose and amino acid metabolism in postpartum transition Holstein cows

Abstract

Nine periparturient Holstein cows catheterized in major splanchnic vessels were used in a complete randomized design with repeated measurements to investigate effects of glucogenic and ketogenic feeding strategies on splanchnic metabolism of glucose and amino acids. At parturition, cows were assigned to 1 of 3 feeding strategies: a glucogenic diet (GLCG) based on sodium hydroxide treated wheat grain (56.5% of diet dry matter); a ketogenic diet (KETO) based on fodder beets (40.5% of diet dry matter); or an alfalfa-glucogenic strategy (ALF-GLCG) supplying 100% alfalfa (Medicago sativa L.) haylage at the day of parturition, followed by a 6-d linear shift to the GLCG diet. Samples were obtained 14d before expected parturition as well as at 4, 15, and 29d in milk (DIM). The net portal release of glucose was greatest with GLCG, reflecting the higher intake of ruminal escape starch with GLCG, as compared with a lower starch intake with KETO. Postpartum, the portal recovery of feed starch was greater (28±3%, mean ± SEM) with KETO as compared with GLCG (15±4%). At 4 DIM, the net hepatic release of glucose was greatest with KETO and least with ALF-GLCG, whereafter it increased as lactation progressed with ALF-GLCG and GLCG, but not with KETO. The high alfalfa haylage allowance at 4 DIM with the ALF-GLCG treatment induced the lowest net release of nutrients from the splanchnic tissues at 4 DIM. The hepatic removal of lactate as percent of total influx (mean ± SEM) increased from 27±3% prepartum to 56±3% at 4 DIM. The hepatic removal of lactate as percent of net portal release increased from 144±10% prepartum to 329±17% at 4 DIM with ALF-GLCG and KETO as compared with 242±20% in GLCG. No clear evidence for an amino acid sparing effect in splanchnic tissues from increasing small intestinal glucose absorption was observed. In conclusion, the glucogenic feeding strategy induced the highest glucogenic status among the tested feeding strategies due to greater release of glucose from splanchnic tissues. In contrast, the immediate postpartum high allowance of alfalfa haylage provided the lowest amount of nutrients from the splanchnic tissues, inducing low glucogenic status, pointing to the importance of allocating highly digestible diets to postpartum transition cows. Salvaging glucogenic carbon via interorgan transfer of lactate from peripheral tissues supported the immediate postpartum incremental increase in hepatic glucose release rather than hepatic catabolism of amino acids.