Eight Holstein cows (4 primiparous and 4 multiparous) were used in a replicated 4 x 4 Latin square design to determine milk production response and N balance when diets had no NRC-predicted excess of rumen-undegradable protein (RUP) or rumen-degradable protein (RDP), 10% RUP excess, 10% RDP excess, or 10% excess of both RUP and RDP. Diets were fed as a total mixed ration with (dry matter basis) 25% alfalfa silage, 25% corn silage, 19 to 21% corn grain, and varying proportions of solvent soybean meal and expeller soybean meal as primary sources of supplemental RDP and RUP, respectively. Milk yield and dry matter intake (DMI) were recorded daily, and total collection of feces and urine was completed in the last 3 d of each 21-d period. Dietary crude protein averaged 17.5 and 18.5% for the recommended and excess RDP diets, respectively, and 17.3 and 18.4% for the recommended and excess RUP diets, respectively. When cows were fed excess RUP diets in the form of expeller soybean meal, DMI and milk production increased, but the opposite was true when the diets contained excess RDP in the form of solvent soybean meal. Milk composition was not affected by RDP, RUP, or by parity, and there were no parity x RDP interactions for any of the measurements. However, apparent digestibility of neutral detergent fiber, dry matter, and N increased in multiparous cows but not in primiparous cows because of excess RUP. The increase in the yield of milk N with excess RUP was not influenced by parity, but multiparous cows retained more of the additional N apparently absorbed, whereas primiparous cows excreted the additional apparently absorbed N in the urine. Overall, the difference in urinary N due to parity (70 g/d) was about 4 times greater than the impact of dietary treatments (17 g/d). Our results suggest that multiparous cows have either a much larger urea pool or a greater demand to restore body protein mobilized earlier in lactation compared with primiparous cows. Reduction in urinary N excretion in commercial dairy herds could be obtained by separately balancing rations for first and later lactations.

Aims To evaluate the persistence of Mycobacterium avium subsp paratuberculosis (Myco. paratuberculosis), Salmonella enterica serotype Typhimurium (Salm.Typhimurium) and a commensal Escherichia coli (E. coli) isolate under the low pH and high organic acid (OA) conditions of ensiling of forages. Methods and Results Decay rates and the time required to obtain a 90% reduction in cell concentration were calculated following (i) exposure to buffered OA (pH 4·0, 5·0, 6·0 or 7·0) (ii) exposure to silage exudates and (iii) survival through ensiling of forage materials. Salm. Typhimurium had higher decay rates in silage exudates (−0·5601 day−1) than did E. coli (−0·1265 day−1), but both exhibited lower decay rates in silage than in OA or silage exudates. Myco. paratuberculosis showed no decrease in silage and decay rates in silage exudates were significantly lower (2–12 times) than for the other two organisms. Conclusions Escherichia coli, Salm. Typhimurium and Myco. paratuberculosis exhibit marked differences in response to acidity. All three organisms show acid resistance, but Myco. paratuberculosis in particular, if present in manure and applied to forage grasses, may survive the low pH and high OA of the ensilaging process; silage may therefore be a potential route of infection if ingested by a susceptible animal. Significance and Impact of Study This information contributes to the understanding of potential risks associated with silage preservation and contamination of livestock feed with manure‐borne pathogens.

The goal of nitrogen (N) application is for crop uptake, resulting in improved yield and quality of the crop harvested. However, N fertilizer applications are also susceptible to emission losses, as ammonia (NH 3 ) and nitrous oxide (N 2 O), and surface and groundwater losses as nitrate-N (NO 3 -). In the past, research has focused on the rate of nutrient application on yield, quality, and N losses. As producers look to improve nutrient use efficiency, the need for research to address other factors in nitrogen application has grown. Specifically, a growing number of researchers are looking at how the 4Rs of nutrient application-source, rate, time, and place-affect crop uptake and yields. The fertilizer industry established the 4R Research Fund to help establish sustainability indicators and environmental impact data for implementation of 4R nutrient stewardship across North America.Improved N use efficiency can be achieved through combinations of rate, source, time, and place. A recent roundtable meeting identified as a goal "broadening the focus of applied research beyond N rate to move toward more integrated agricultural systems," and cited the 4R nutrient stewardship approach as a step to help represent A growing number of researchers are looking at how the 4Rs of nutrient application-source, rate, time, and place-affect crop uptake and yields. This article begins a new series from The Fertilizer Institute highlighting some of the latest 4R research. Earn 0.5 CEUs in Nutrient Management by reading this article and taking the quiz at www.certifiedcropadviser.org/ certifications/self-study/825. crop nitrogen research

Nitrous oxide (N2O) is a potent greenhouse gas that can result in nitrogen loss from the soil. The scientific literature is deficient in studies that measure N2O emissions, NO3 leaching, and crop performance across multiple sources of nitrogen fertilizer and changes in field practices. However, there are tools and strategies available to consultants and producers to improve nitrogen use efficiency and reduce N2O emissions while not decreasing yield. Earn 0.5 CEUs in Nutrient Management by reading this article and taking the quiz at http://www.certifiedcropadviser.org/education/classroom/classes/543

Where did the 4R idea come from? This article looks at a few of the early sources and how those concepts relate to current challenges facing phosphorus management. Earn 0.5 CEUs in Nutrient Management by reading this article and taking the quiz at http://www.certifiedcropadviser.org/education/classroom/classes/564.