Farm-level evaluation of implementing feeding best management practices (BMP) on Pennsylvania dairy farms
Feeding best management practices (BMP) can have a significant impact on the environmental footprint of dairy farms. The objective of this study was to evaluate the environmental and productive effects of implementing feeding BMP on commercial dairy farms in Pennsylvania. Fifteen farms (124.8 ± 20.5 ha, 169 ± 39 cows, and 31.4 ± 0.2 kg/cow/d milk production) in central and southeast Pennsylvania participated in the study. A set of 4 background total mixed ration (TMR), forage, milk, feces, and urine samples, as well as feed intake and production data, were collected from each cooperator farm biweekly between January and March of 2013 (PreBMP period). Following the implementation of applicable feeding BMP, chosen by the producer, including reduction of dietary crude protein (CP; n = 9) and P (n = 5), adjusting rations for changes in forage dry matter (n = 10), and group feeding of the lactating herd (n = 2), another set of 4 sampling and data collection events took place between June and August of 2013 (PostBMP period). Data were analyzed using the MIXED procedure of SAS with farm as a random effect. On farms in which dietary CP was reduced (from 17.2 to 15.9%; P < 0.01), fecal N (FN; 2.78 vs. 2.63%; P = 0.01), total urinary N (UN; 0.071 vs. 0.055%; P < 0.01), urinary urea N (UUN; 52.2 vs. 44.4mg/dL; P < 0.01), and MUN (16.9 vs. 13.9 mg/dL; P < 0.01) decreased (Pre- vs. PostBMP, respectively). Only 3 farms successfully decreased dietary P (from 0.42 to 0.40; P <0.01), which resulted in decreased fecal P concentration (0.85 vs. 0.69; P < 0.01). Group feeding was implemented on 2 farms. The average CP of the rations fed on these farms decreased from 15.7 to 14.4% (P = 0.03), which resulted in decreased, UN (0.077 vs. 0.048%; P < 0.01), UUN (56.1 vs. 36.9 mg/dL; P < 0.01), and MUN (17.4 vs. 13.7 mg/dL; P = 0.03). DMI and milk production were not affected by BMP implementation. Bulk tank milk fat (3.91% vs. 3.56%; P < 0.01) and milk protein (3.13 vs. 2.98%; P < 0.01) decreased from Pre- to PostBMP on all farms, perhaps due to seasonal effects. In conclusion, reduced dietary CP decreased N concentrations in urine and feces and reduced dietary P decreased fecal P concentration on commercial dairy farms.
dairy farm, dietary protein, dietary phosphorus