Quantification of Nutrients Consumed and Utilized by Holstein Cows Grazing Grass Pastures in the North-Eastern USA

Managing the nutrition of high producing dairy cows on pasture in the north-eastern USA is challenging owing to difficulty in accurately estimating intake and In determining nutrient utilisation by grazing dairy cows. In Trial 1, 16 lactating Holstein cows were used to estimate intake with an intensively grazed orchardgrass (Dactylis glomerata L.) pasture with 2 stocking rates of 2.S and 3,9 cows/ha in a 24 week grazing season. Cows were fed a grain supplement which comprised about 35% of the diet dry matter. Chromium oxide was used as an external marker in faeces, Results of Trial 1 indicated total dry matter intake was at or slightly below intake recommended by NRC (1989). Also, most of the crude protein In pasture was degradable. In Trial 2, 3 non-lactating Holstein cows fitted with duodenal and ruminal cannulae were fed all-forage diets consisting of fresh (grazed) orchardgrass­dominant pasture or the same grass conserved as hay or silage to determine nutrient utilisation, Results indicate that grazing cows have high ruminal and low duodenal concentrations of nutrients, Thus, cows may not be efficiently utilising nutrients from pasture as compared with stored forages and require different supplemental feeding strategies.