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Feed Management: Phosphorus Levels in Component-Fed Herds

Feed Management: Phosphorus Levels in Component-Fed Herds
Introduction
 
Feed management is a key practice in livestock nutrient management. It includes ration formulation for optimal supplementation of nitrogen and phosphorus, consistency and accuracy of feed delivery, regular feed testing, and diagnostic tools to monitor results. In 2007, Mid-Atlantic Water Program (MAWP) scientists applied the national feed management program to meet the needs of dairy consultants in the Chesapeake Basin. This program certifies consultants in precision feed management, a practice that reduces nutrient loads in animal wastes by minimizing the phosphorus and nitrogen content in the feed. Over the years, the work of this project team has established precision feed management as both an economically and environmentally viable best management practice. As such, state watershed implementation plans include precision feed management as a method to meet load allocations.
 
In 2011, fifty-one Pennsylvania operations received Environmental Quality Incentive Program or Chesapeake Bay Watershed Initiative funding from the Natural Resources Conservation Service (NRCS) for feed management. Pennsylvania currently has twenty-three NRCS qualified nutritionists to write feed management plans. Many of the contracted feed management plans on dairy and beef operations have completed the first year of implementation.
 
Observations From Contracted Dairy Operations
 
Data from the first year's plans submitted to NRCS have revealed several on-going challenges. Focusing on phosphorus, herds feeding a total mixed ration (TMR) have shown a poor agreement between the formulated versus the actual diet fed. A majority of the actual TMRs analyzed show phosphorous levels outside an acceptable margin of ± 0.03% from the formulated, which is an above average margin. There are opportunities to improve precision feeding.
 
The other areas creating greater challenges are component-fed lactating, heifer, and dry cow groups. In several herds some rations were reformulated to remove all inorganic phosphorus and fecal phosphorus remained unchanged or even increased. Fecal phosphorous levels in young calf groups are proving to be high as well. The Mid-Atlantic region is unique in that component-fed herds are commonplace compared to other areas of the country. Phosphorus research reported in peer-reviewed journals focuses on TMR-fed diets. Component-fed herds present a unique set of challenges compared to TMR-fed herds as it relates to feed management practices and their influence on phosphorus excretion. These include feeding sequence of forages and grains, feeding times of energy feeds versus protein feeds, and the number of feedings throughout the day.
 
Current data is lacking on expected fecal phosphorus levels for young-stock. Fecal phosphorus levels in young calf groups on some farms are testing well above the recommended range of 0.65 to 0.85% on a dry matter basis. Young-stock typically receive poor oversight on consumption rates and are generally fed a standard pellet that may or may not match the animals' requirement for phosphorus. Deviation between consumption rates of phosphorous and expected excretion amounts are questioned as well. These are key areas that need to be better defined.
 
Another area that has not been addressed is sampling procedures. Observations of high fecal phosphorus levels have prompted questions about the potential of contamination in the fecal samples collected from cow or heifer groups. Plausible results could be associated with the addition of organic matter, i.e. bedding, during fecal sample collection. It was hypothesized that this may be contributing to higher than expected fecal phosphorus levels. Also, some grain mixtures were analyzed using near-infrared spectroscopy (NIR), which may be providing erroneous information especially when evaluating phosphorus content. Wet chemistry for phosphorus analysis typically provides more reliable results. The Penn State Extension Dairy Team submitted a proposal to the Mid-Atlantic Water Program to evaluate if the high phosphorus levels being observed on contracted dairy operations is a reflection of the ration fed, sampling error, or other issues.
 
Component Fed Herds - Sampling Procedures
 
In January 2013, six component-fed dairy operations were selected for intense sampling of ration ingredients and manure. The operations were located in the Northern, Western, Central, and Eastern parts of Pennsylvania. The goal was to select farms that had a diversity of forage programs that consisted of grass and alfalfa haylage as well as corn silage. The farms were also diverse in how they fed. Two farms fed conventionally in a free-stall set-up and four were in tie-stall barns for the lactating cows. All heifer groups were housed in pens.
 
Feed and fecal samples were collected on average producing cows, peak producing cows (20 pounds over average), and three heifer groups (3 to 7 months, 7 to 12 months, and 13 to 22 months). All feeds and fecal samples were submitted to Cumberland Valley Analytical Lab and were analyzed by wet chemistry. Fecal samples were analyzed for solids and P2O5.
 
Each farm was visited at the same time of day: 9:30 a.m. to 12:30 p.m. This time period was generally when all animal groups were being fed either additional forage or one of their grain feedings. The same people collected feed and fecal samples on each farm. Buckets were used to collect individual lactating cow manure samples (5 cows representing average milk production and 5 cows representing peak milk). Samples were taken from the cows as they were defecating or from the ground right after defecating, or from the rectum. Individual cow samples were composited for the average and peak producers. Both individual cows and composites were analyzed for fecal phosphorus. Only the composites were analyzed for fecal starch. For the heifers, fecal samples were taken directly from the animal or if they were observed defecating, a sample was taken from the pile without contamination from bedding. Only composited fecal samples for the heifer groups were analyzed.
 
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