Description of a bovine model for studying digestive and metabolic effects of a positive energy balance not biased by lactation or gravidity

Physiological consequences of adaptation to and continued feeding of a high-energetic diet were studied in eight non-pregnant, non-lactating dairy Holstein cows over a period of 16 weeks. The first six weeks served as an adaptation period from the low energetic straw-based diet (3.8 MJ NEL/kg DM) to the high-energetic ration (7.5 MJ NEL/kg DM). Intake of dry matter (DM) increased with dietary energy concentration from 9 to 20 kg/d up to week 9 to 12 and decreased thereafter. The initial live weight (LW) of 550 ± 60 kg was increased linearly and corresponded to an average daily LW gain of 2.3 ± 0.3 kg. Energy balance increased approximately nine-fold to a maximum of 114 MJ NEL/d in week 10. Ruminal fermentation pattern was completely changed from an acetate dominating profile to a propionate based one, which was paralleled by a marked increase in the rumen fluid endotoxin concentration. Unlike blood glucose concentration, which increased continuously, that of cholesterol and triglycerides started to increase after an initial stagnation. In conclusion, both ruminal adaptation to a high-energetic diet and the continued feeding of such a diet induced digestive and metabolic adaptations in non-pregnant, non-lactating cows characterised by a progressing positive energy balance.