Short-Term Strategies to Reduce Excess N on the Farm
- Formulate farm and group specific rations. The studies of Tylutki and Fox (2000) and Tylutki (2002) demonstrated the impact of inaccurate ration formulation and quality control on variation in milk production and income. Based on these and other studies, we believe models such as the Cornell Net Carbohydrate and Protein System (CNCPS) will be utilized in the future to accurately predict farm specific animal nutrient requirements, absorbed nutrients from each feedstuff available to meet requirements, and nutrient excretion that can be used for manure nutrient management planning. Of particular importance are models that result in optimizing the rumen to maximize forage utilization and microbial protein production. Data and feed analysis required by models must be farm specific (housed on-farm) and accurate.
- Appropriate feed analysis schedule and protocol to accurately represent the feeds being fed. To accomplish this, a farm specific feed analysis protocol needs to be followed resulting in a farm specific feed database that includes forages and concentrates. Tylutki et al. (2000) simulated the impact of NDF and dry matter variation in corn silage using the average values and standard deviations as sampled on a 500-cow farm. The impact of improper forage analysis, and lack of control over the dry matters at feeding, resulted in a large annual variation in nutrient excretion (242 pounds N excretion and 64 pounds of P excretion), feed inventory required (61 tons of corn silage), and income over feed costs ($21,792) per 100 cows annually. Their recommendations include determining dry matters of all forages at least twice weekly (more often if wide fluctuations in intakes are observed) and then adjusting diet formulations as needed.
- Improve feeding accuracy. Most farms assume that what is being mixed and fed is what is supposed to be fed. In many cases, this is not a valid assumption (Predgen and Chase, 2002). Tylutki et al. (2000) evaluated the impact of varying feeding accuracy ±3%. The addition of feeding error increased annual variation in P excretion (18 pounds), corn silage inventory (9 tons), and income over feed costs ($19,148) per 100 cows annually. Feeding accuracy needs to be tracked to identify sources of variation, as well as to manage inventory. Commercial software and hardware is available that can be linked to the mixer scales to track this information.
- Monitor dry matter intake to improve accuracy of ration formulation and animal performance. Proper ration formulation relies on many inputs from the farm, including animal body weight, feed inventory, and actual dry matter intakes. To decrease nutrient excretion per unit of milk produced, actual dry matter intakes must be known in order to ensure adequate grams of each nutrient are provided to support animal requirements. The data can also be used as a diagnostic tool.
- Make ration changes as needed to improve accuracy andminimize safety factor in the ration. By increasing the dry matter intake 5%, ration nutrient concentrations can be lowered. Chase (1999) calculated that by increasing intake 5%, it is possible to decrease diet crude protein about one percentage unit to achieve the same pounds of protein intake. This allows higher inclusion rates of homegrown feeds, thus decreasing purchased nutrients. Safety factor reduction, while very effective in reducing excretion, requires a high management level, thus management and feeders need additional training to minimize potential performance variation (Tylutki, 2002).
- Improve feed-bunk management to increase intake and consistency of animal performance. This includes daily cleaning, pushing feed up several times daily, and all other bunk management practices. More consistent performance, and feed intake, allows for more accurate ration formulation for any production level.
- Control the level of refusals. Most farms’ feed refusals from the lactating herd are fed to replacement heifers. From a nutrient excretion viewpoint, this is an expensive practice. Mineral and protein levels that are adequate for lactating cows do not fit most replacement heifer groups. The amount of refusals must be at a level that is consistent with farm management to achieve maximum dry matter intake; however extremely high levels need to be avoided and are indicative of poor management.
- Use the proper ‘tools’ to track the impact of changes in ration formulation and feeding management. These ‘tools’ fall into two categories: short-term (milk production, milk components, and milk urea nitrogen) and long-term (body condition score, replacement heifer growth, lactation persistency, and reproduction). Both sets of tools are required to accurately evaluate a herd.
- Obtain and evaluate manure analysis. Manure needs to be analyzed two ways: visual observation to determine what is not being digested by the cow, and the second is a manure nutrient analysis at time of land application. If large fiber particles or corn grain is evident in visual observation, rations and feeding management need to be addressed. As dietary N and P levels are decreased, manure nutrient concentrations will be decreased.