Progress 10/01/02 to 09/30/06
Outputs
With previous funding from the CERANR, UW-Madison and UW-Platteville Co-PIs have initiated a system's approach protocol to estimate apparent nitrogen emission (N-losses) during collection of manure excreted by a lactating herd in a freestall barn and to determine the relative impact of dietary crude protein, side of the barn, and month of the year on milk production performance (milk volume and milk component yields), manure production and composition, and herd-level nitrogen balance. The Lactating herd of the Pioneer system-research farm at the University of Wisconsin-Platteville was used for this research in 2004 and 2005. Cows were housed in an 80 stall 2-row barn-design with concrete floor and oat straw bedding. The herd was randomly divided in two groups and assigned to two different diets. A recommended diet was formulated to match the current national feeding guidelines (NRC, 2001) for a cow producing 90 lbs/milk per day with a dietary CP between 16.0 and 17.0 %
of diet DM, and a second diet was formulated to supply 1.5 units higher of CP than the recommended diet (17.5-18.5 % diet DM). Monthly samples of all diet ingredients and milk were collected and analyzed for N content. Total manure collection by manual alley-scraping from each group of cows was conducted monthly over a 3-days and manure samples collected at different time points (12 pm, 8 pm, and 4 am) were analyzed for N content. Dry matter intake and milk yield was recorded to estimate N balance for each group of cows. Our results suggested that feeding 16.5% vs. 18% crude protein diet did not alter dry matter intake (24 vs. 24.5 kg/c/d), milk production (32.2 vs. 31.7 kg/d/d), milk nitrogen excretion (0.48 vs. 0.48 kg/d/c), or manure production (76.7 vs. 78.2 kg/c/d), but influenced nitrogen intake (648 vs. 711 g/c/d), manure nitrogen excretion (393 vs. 422 g/c/d), and the estimate of apparent ammonia loss emission within 4 hours of manure accumulation in the alleys (99 vs. 136
g/c/d). Results of this long term trial show also the combined impact of change in diets with season. Lowest and highest apparent ammonia loss were 83 and 191 g/c/d in January 2005 and September 2004, respectively. This drastic difference was explained not only by a change in temperature with season, but also with the feeding of a high alfalfa silage diet as the farm manager ran out of corn silage at the end of the summer, a common occurrence on commercial farms.
Impacts
Results of this project indicated that a reduction of 1.5 unit of crude protein to respect NRC 2001 recommended levels in dairy cow diets may reduce feed cost, with no change in revenue from milk sales, but a 27% reduction in ammonia emission during manure collection.
Publications
- Aguerre, M. Hunt, T., Weigel. C., and Wattiaux, M. 2005. Effect of dietary nitrogen on estimates of nitrogen emission during manure collection in a freestall barn. J. Dairy Sci. 88: 45 (Abstract).
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Progress 01/01/05 to 12/31/05
Outputs
Our earlier work indicated that milk urea nitrogen (MUN) concentration was negatively correlated with dry matter intake (DMI) and was greater in cows with a greater milk yield relative to DMI (i.e., greater feed efficiency) at three week of lactation [Wattiaux and Karg (2004)]. This observation suggests that MUN may be more reflective of energy and protein balance of the cows than the adequacy of dietary inputs in the first few weeks of lactation. In a recent statistical analysis of test-day MUN from DHIA records, MUN increased rapidly in the days after calving, peaked at 9 to 14 days and then leveled off at approximately 21 days in milk [Wattiaux et al., 2005]. Level of MUN may be affected by changes in DMI, diet composition, and lactogenesis, and as indicated earlier, the energy balance of the cow. A commonly used diagnostic measure to determine the health status of dairy cows in early lactation is plasma non-esterified fatty acids (NEFA) concentrations. A blood
sample is taken and analyzed for NEFA, which gives an assessment of the amount of fat that a cow is mobilizing at the time of sampling. If there were a strong relationship between urea nitrogen (in milk) and plasma NEFA, it would allow producers to use a milk sample to determine if cows are in negative energy balance. This method is non-invasive and the analysis is less expensive than NEFA analysis. Assuming the MUN and blood urea nitrogen (BUN) are as highly correlated in early lactation as in later stages of lactation, our objective was to determine whether BUN was related to energy balance or a measure of tissue mobilization during the periparturient period. Since MUN is elevated in the first few weeks of lactation when cows are mobilizing energy reserves and are in a state of negative energy balance [Wattiaux et al., 2005], we hypothesized that BUN would be related to energy balance and measures of tissue mobilization. Forty-one Holstein cows that were utilized for Rastani et al.
(2005) were used for this experiment. Cows had varying energy balance due to differences in dry period length but they were fed the same diets throughout the experiment (prepartum diet: NEL=1.75 Mcal/kg, CP=16.8 percent; Postpartum diet: NEL =1.71 Mcal/kg, CP=16.9 percent). Blood samples were taken at 2 wk prepartum, and 1 wk and 2 wk postpartum. Relationships between BUN and measurements, which included energy balance, DMI, N intake, milk yield, 4 percent fat-correct milk yield (FCM), milk N, milk yield/DMI, FCM yield/DMI, body weight (BW), postpartum BW loss, and plasma NEFA concentration were determined by regression procedures. Equations for the prediction of NEFA were evaluated with single and multiple factors. Two weeks after calving, there was a significant linear relationship between BUN and NEFA (R-square= 0.14; P less than 0.02). Results indicated also that 65 percent of the variation in NEFA can be explained with changes in BUN, feed efficiency and postpartum BW change
taken all together. Additional research with more early lactation cows is needed to examine these relationships and validate the equations.
Impacts
Our earlier research focused on the use of milk urea nitrogen (MUN) as an indicator of nitrogen utilization in dairy cattle and environmental impact of excess nitrogen in dairy diets. However, this year our research focused on the relationship between MUN and cow health in the first few weeks after calving. Post-calving metabolic disorders may have cost more that $1 million to the Wisconsin dairy industry in 2003. Our previous work indicated that the MUN is a good indicator of the excess (or deficiency) of dietary protein in dairy cattle diets. However, our results also suggested that in the first few weeks after calving, MUN may reflect more the energy and protein status of the cow rather than the adequacy of her diet. Thus, results of this research may contribute to using MUN as a new tool for early detection of cows with extreme negative energy balance. These cows are more prone to developing health problems in the weeks after calving due to metabolic disorders.
Publications
- Rastani, R. R., Nelson E. Lobos, Matias J. Aguerre, Ric R. Grummer, and Michel A. Wattiaux. 2006. Relationships between blood urea nitrogen and energy balance or measures of tissue mobilization in Holstein dairy cows during the periparturient period. J. Dairy Sci (in review)
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Progress 01/01/04 to 12/31/04
Outputs
Eight Holstein cows (4 primiparous and 4 multiparous) were used in a replicated 4x4 Latin square to determine milk production response and nitrogen (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 (TMR) with (dry matter basis) 25% alfalfa silage, 25% corn silage, 19-21% corn grain, and varying proportion of solvent soybean meal and expeller soybean meal as primary sources of supplemental RDP and RUP, respectively. Milk yield and DMI were recorded daily and total collection of feces and urine were completed in the last 3 days of each 21-day period. Dietary crude protein (CP) 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, dry matter intake (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 dietary treatments or by parity. In addition, there were no parity by RDP interactions for any of the measurements. Digestibility of neutral detergent fiber (NDF) and apparent digestibility of dry matter (DM) and N increased in multiparous cows, but not in primiparous cows as a result of excess RUP. The increase in milk N with excess RUP was not influenced by parity, but multiparous cows retained more of the additional N apparently absorbed than primiparous cows while primiparous cows excreted most of the additional N apparently absorbed in the urine. Overall, the difference in urinary N due to parity (70 g/d) was more than 4 times larger 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 to primiparous cows. Greater reduction in urinary N excretion in commercial dairy herds could be obtained by balancing rations for first and later lactation separately. Additional data collected in this trial included the within day variation in ruminal ammonia concentration, blood urea nitrogen, and urinary N concentration and excretion.
Impacts
Increasing societal concerns about the environmental loss of agricultural nutrients has encouraged the investigation of ways to improve N efficiency and reduce N losses from dairy operations. This research has provided data that contribute to lowering the cost of feeding cows and lowering environmental loss of nitrogen from dairy operations. In this study, it was found that the difference in urinary nitrogen, a form of nitrogen most vulnerable to environmental loss, due to parity (70 g/d) was more than 4 times larger than the impact of a difference of about 1 percentage unit of dietary crude protein (17 g/d). Greater reduction in urinary N excretion in commercial dairy herds could be obtained by balancing rations for first and later lactation separately.
Publications
- S.A. Flis, and M.A. Wattiaux. 2005. Effects of Parity and Levels of Rumen Degradable and Undegradable Protein on Production and N-Balance in Holsteins. J. Dairy Sci. (In Press)
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Progress 01/01/03 to 12/31/03
Outputs
In the spring of 2003, four multiparous and four primiparous mid-lactation Holstein cows were used in a replicated Latin Square design (a) to determine nitrogen (N) balance when the diet includes different levels of rumen degradable protein (RDP) and rumen undegradable protein (RUP), (b) to determine whether previously published equations to predict urinary N excretion apply to primiparous and multiparous cows alike or whether separate equations are required, and (c) to determine whether NRC 2001 can be used to predict urine N and fecal N excretion. A sub-objective of this trial was to compare milk urea nitrogen (MUN) values obtained from two commercial laboratories with those from our own lab. The comparison of three different methods for determining MUN in fresh or frozen milk samples is important given the current controversy regarding the accuracy of commercial laboratories. In this trial, a control diet was formulated to meet National Research Council (NRC)
recommendations for RDP and RUP. The three treatment diets were formulated with N excess to the NRC 2000 recommendations. Diets were 10% excess RDP, 10% excess RUP, and 10% excess of both RUP and RDP. Each period consisted of 3 weeks of adaptation and 1 week experimental measurements. Dry matter intake and milk production were measured daily throughout the adaptation and experimental periods. Milk samples were analyzed for major components (lactose, fat and true protein), total N, and urea N. During week 4, a total collection of feces and urine was made from each animal for 3 days and sampled for analysis of N concentration (feces and urine) and creatinine (urine). Other measurements included body weight, rumen sampling (pH and ammonia) and blood sampling (plasma urea nitrogen). Feed ingredients were incubated in situ to determine the actual RDP and RUP values of the protein sources used in the diets. Most laboratory analyses have been completed. Statistical analyses and publication
of results are anticipated in 2004.
Impacts
This research will provide data that will contribute to lowering the cost of feeding cows and lowering environmental loss of nitrogen from dairy operations. In addition, this project will contribute to the validation of an on-farm sampling protocol (primarily urine spot sampling) that will help producers and consultants in predicting manure nitrogen composition (organic vs inorganic nitrogen) and in monitoring the fate of dietary nitrogen consumed in commercial dairy herds.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
The overarching objective of this research is to investigate alternative dietary strategies that maintain or even enhance N utilization by dairy cattle while reducing potential losses of ammonia-N to the environment. Specific studies are designed to measure the impact of forages, minerals, and sources of non-fiber carbohydrates on (1) animal performance, (2) routes of N excretion, (3) characteristics of manure and in particular (4) its susceptibility to ammonia-N volatilization. A graduate student has been hired to carry out the research both on campus and with commercial dairy operation as necessary.
Impacts
The study of dietary factors affecting ammonia losses from dairy manure will contribute to economic and environmental sustainability of our agricultural production systems. The increased efficiency of nitrogen use by dairy cattle may increase farm profitability and stewardship of natural resources. This research will provide estimates of ammonia-N loss (kg/dairy cow/yr) from Midwest dairy farms, and in a larger context, it will explore ways to reduce the emission of N pollutants that are harmful to human health and enhance global warming.
Publications
- No publications reported this period
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