Recent research has determined that dietary phosphorus levels for lactating dairy cows can be significantly reduced without negatively impacting milk production or reproductive performance. Presently, most dairy rations are being formulated with phosphorus levels higher than recommended by the National Research Council (NRC 2001). Reducing phosphorus levels in Pennsylvania dairy rations to NRC recommendations can provide two benefits: reducing manure phosphorus excretion, thus reducing environmental concerns; and, most importantly, reducing dairy ration costs by $15.00 per cow per year with potential savings to Pennsylvania dairy producers of $9 million annually.
While some producers are aware that manure phosphorus levels will decline when feed phosphorus levels are reduced, many are reluctant to reduce their phosphorus feeding for fear of reduced milk production and/or reproductive performance. Change in producer attitudes and practices are often more widely and rapidly accomplished when some from within their group adopt the change and document the desired outcome(s). Fourteen dairy producers from Southwestern Pennsylvania have agreed to cooperate in this project that will show that reducing phosphorus in the dairy ration to revised NRC recommendations will decrease manure excretion and not adversely affect dairy cow performance. This project seeks to accomplish reductions in manure phosphorus levels and improvements in farm income through a well-monitored multi-farm research/demonstration project of the new phosphorus feeding recommendations. Environmental sustainability will be enhanced when bringing these farms into compliance for the phosphorus-based nutrient management plans. Of even greater interest to the producers involved and to the dairy community at large will be the improvement in the economic sustainability of their individual farms through a reduction in the cost of feeding their cows without a reduction in gross income.
During the two year study, seven of the operations will continue to supplement phosphorus at levels similar to the previous two years (same P) while the other seven will reduce ration phosphorus to NRC recommended levels (reduced P).
Reduce ration phosphorus levels on seven of the 14 study herds to NRC recommended level.
Milk and component production will be monitored and measured to see if there is significant change with the reduced ration phosphorus level.
Reproductive performance will be monitored to see if there is significant change with the reduced ration phosphorus level.
An economic analysis will be conducted to see if the reduced phosphorus levels significantly
affected feed costs and profitability.
Fourteen dairy producers where originally asked to participate in the study, however, 11 producers actually completed the study.
Milking cow rations were submitted by the 14 original herds and ration phosphorus levels were documented and used to determine which herds would be asked to lower ration phosphorus levels to the NRC recommended level of .39%. Total mixed rations (TMR) and manure samples were analyzed to provide this confirmation. Four herds with ration phosphorus levels above .44% phosphorus were the herds selected to lower ration phosphorus levels to NRC recommendations.
The dairy nutritionist for each of these four herds were contacted and asked to cooperate with the NRC recommendations. The remaining 10 herds served as the controls for the study.
TMR and manure samples were collected every six months over the two year period and analyzed for percent phosphorus. Rations for each producer were also collected at the time of the TMR and manure sampling and ration phosphorus levels were documented.
Dairy Herd Improvement (DHI) records were monitored for milk production, milk components (butterfat and protein percentages), and reproductive performance (calving interval) and the three levels were recorded.
At the start of the study, ration phosphorus ranged from .37% – .57 % (.20% range).
At the start of the study, manure phosphorus ranged from .48% – 1.04% (.56% range).
At the conclusion of the study, ration phosphorus ranged from .36% – .42% (.06% range).
At the conclusion of the study, manure phosphorus ranged from .40% – .81% (.41% range). Ration and manure phosphorus levels where significantly lower at the conclusion of the study.
The three herds that were asked to lower ration phosphorus levels to NRC recommendation of .39% had an average ration phosphorus level of .46% at the start and .38% respectively at the conclusion of the study and manure phosphorus levels of .88% and .66% respectively.
Milk production was not significantly affected by lower ration phosphorus levels. Average milk production at the start of the study was 66.8 lbs./cow/day and 70.2 lbs./cow/day at the conclusion of the study.
Reproductive performance as measured by calving interval was not significantly affected by lower ration phosphorus levels. Average calving interval at the start of the study was 14.2 months and 13.9 months at the conclusion of the study. These results confirm other research that has been conducted indicating dietary phosphorus levels can be significantly reduced without negative impacts to milk production and reproductive performance.
Based on current ration costs, dairy producers could reduce ration costs by $21.90 (range $14.60 – $29.20) per cow per year by following the NRC recommendation of .39% phosphorus in the ration.
This study reinforces other research projects indicating dietary phosphorus levels can be significantly reduced without negative impacts to milk production and reproductive performance. Many dairy nutritionists are still formulating dairy rations with dietary phosphorus levels above the NRC recommendation of .39%. This is an added feed cost as well as a potential environmental hazard from excess phosphorus excretion in the manure and the potential of increasing phosphorus in ground and surface runoff. This has become a major concern in many Pennsylvania water sheds and especially the Chesapeake Bay. We hope to publish the findings of this study in the “Hoard’s Dairyman” magazine.
Education & Outreach Activities and Participation Summary
One of the major topics presented at the 2005 SW Pennsylvania Dairy Day Program focused on “Phosphorus Based Nutrient Management.” Fourteen veterinarians/dairy nutritionists and 56 dairy producers attended the workshop.
Based on current ration costs, dairy producers could reduce average ration costs by $21.90 (range $14.60 – $29.20) per cow per year by following the NRC recommendation of .39% phosphorus in the ration.
All 11 herds in the study had lower ration and manure phosphorus levels as a result of participating in the study.
An educational workshop was conducted for veterinarians and dairy nutritionists to encourage them to follow the NRC recommended ration phosphorus level of .39%. Seventy four percent of the workshop participants (N=14) indicated they had a moderate to great deal better understanding of the NRC requirements as a result of attending the workshop.
An educational workshop was conducted for dairy producers to encourage them to follow the NRC recommended ration phosphorus level of .39%. Fifty percent of the workshop participants (N=56) indicated they had a moderate to great deal better understanding of the NRC requirements as a result of attending the workshop.
Areas needing additional study
Additional applied field research needs to continue as many dairy nutritionists are still formulating ration phosphorus levels above NRC requirements and recommendations. This study focused only on the ration phosphorus formulation and phosphorus excretion in the manure. With additional funding, we would like to look at soil phosphorus levels and monitor ground and surface water on several farms that are feeding excessive phosphorus versus those who are know feeding at NRC requirements.