Roquet Arroyo, Maria2024-03-132024-03-132023https://hdl.handle.net/1813/114348The transition period is a vulnerable time for dairy cows since it requires enormous physiological adaptations. One of the biggest challenges cows face is an increased Ca demand at the onset of lactation. The inability of some cows to adequately regulate blood Ca concentrations leads to hypocalcemia. A common dietary strategy to prevent hypocalcemia is to decrease the dietary cation-anion difference (DCAD) of the prepartum diet. The degree and effectiveness of implementation of a DCAD diet is monitored using urine pH. Our objective was to establish if there are associations between close-up dry period herd average urine pH or urine pH coefficient of variation and postpartum health disorders. A total of 30 herds in the northeastern United States which feed a negative DCAD close-up diet to multiparous dry cows were enrolled. Urine samples from 12 to 16 multiparous close-up dry cows were collected from each farm, taken within 21 days of their expected due date. The prevalence of milk fever was associated with both average herd urine pH and urine pH coefficient of variation, such that there was an inverse relationship between average herd urine pH and urine pH coefficient of variation. The prevalence of culling within 30 and 60 days in milk was only negatively associated with average herd urine pH. These results suggest that by reducing urine pH coefficient of variation in the close-up dry cow pen, there is no need to induce extreme metabolic acidosis resulting in a very low urine pH. However, if a greater urine pH coefficient of variation is observed, a lower herd average urine pH should be targeted in order to minimize the prevalence of milk fever. These results indicate that herd average urine pH and the variation of urine pH measurements should be accounted for when considering the effectiveness of a negative DCAD diet fed to parous close-up dry cows.en-USAttribution 4.0 Internationaldissertation or thesis