Case Study: Feeding strategy and pasture quality relative to nutrient requirements of dairy cows in the northeastern United States

Pasture samples (n = 380) collected during the grazing season on 14 dairy farms (2012 to 2014) were analyzed for nutritional composition. The MIXED procedure of SAS was used to test effect of year, month, and farm. Frequency analysis was used to determine the proportion of pasture samples that met minimum NEl, CP, and macro mineral requirements of lactating Holstein and Jersey cows (25 kg of milk/d; NRC, 2001). The Large Ruminant Nutrition System model was used to evaluate feeding strategies that accompanied grazing. Each year, forage quality declined with the advancing grazing season (CP, NEl, P < 0.01). If pasture was the only feed, energy was limiting; 36 and 86% of pastures failed to meet minimum NEl requirements for Holstein and Jersey cows, respectively. Nine and 21% of pastures did not meet the minimum CP requirements, whereas Ca, P, and S did not meet minimum NRC (2001) requirements in 31 and 22, 19 and 26, and 11 and 7% of samples for Holstein and Jersey cows, respectively. Magnesium and K were in excess of dietary requirements. Farms were categorized as high, moderate, and low pasture intake (HP, MP, LP). Milk production was numerically lowest for HP farms (16.8 kg/d) and greater for MP and LP farms (20.0 and 21.3 kg/d, respectively). Average DMI from pasture was 90, 46, and 26% for HP, MP, and LP farms, respectively. Overall, pasture quality was high. Varying feeding strategies allow farmers to use pasture, homegrown forages, and concentrates to meet individual production goals.