In order to reduce soil phosphorus (P) saturation, it is essential to assess the amount of manure P on cultivated soil. The purpose of this study was to estimate yearly herd manure P outputs from production and feeding records with a model based on replacement and dairy animals. The model predicts manure P based on P ingested by dairy cows (kg yr-1), P secreted in milk (kg yr-1), P in calf at birth (kg yr-1), and the number of first-lactation cows. The relationship between first-lactation cows and heifers was established; there were 1.3 ± 0.05 heifers for each first-lactation cow. Manure P from heifers was then obtained by fitting the model to manure P accumulated in concrete pits of 12 farms, measured over two 6-mo periods at 1 yr intervals. The model added 10.6 ± 4.6 kg of P for each first-lactation cow to predict the yearly P output of 1.3 heifers. Ratios between P harvested as feed and P predicted in manure were calculated in 1133 herds. High ratios were obtained in herds with less customized concentrate (P < 0.001), more harvested grain and silage (P < 0.001) on farm and larger size of herd (P < 0.001) with more milk (P < 0.001) and lower calf production (P < 0.001). Decreasing purchased customized concentrates and increasing the amount of silage fed to animals are valid options to reduce non-point-source P pollution. Key words: Dairy herds, manure, phosphorus, model, reproductive efficiency
The Relationship Between the Number of Spermatozoa Inseminated and the Reproductive Efficiency of Individual Dairy Bulls