Publications by authors named "Sharon R Aarons"

3 Publications

  • Page 1 of 1

Nutrient Intake, Excretion and Use Efficiency of Grazing Lactating Herds on Commercial Dairy Farms.

Animals (Basel) 2020 Feb 28;10(3). Epub 2020 Feb 28.

US Dairy Forage Research Center, USDA Agricultural Research Service, 1925 Linden Drive West, University of Wisconsin, Madison, WI 53706, USA.

Estimating excreted nutrients is important for farm nutrient management, but seldom occurs on commercial grazing system farms due to difficulties in quantifying pasture intake. Nitrogen (N), phosphorus (P), potassium (K), sulphur (S), calcium (Ca) and magnesium (Mg) intake, excretion and use efficiency of 43 commercial dairy herds grazing pasture were calculated to understand the range in nutrient intake and excretion in these systems. Milk production, feed (grazed and supplement), as well as farm and herd management data were collected quarterly on representative farms located in temperate, arid, subtropical and tropical regions of Australia. Lactating herd sizes on these farms averaged 267 (30 to 1350) cows, with an average daily milk yield of 22 (9 to 36) kg/cow per day and the herds walked from <0.01 to 4 km/day on a variety of terrains. The mean total metabolizable energy (ME) required by cows in the herds was estimated to be 195 (116 to 289) MJ/cow per day. Although these farms are considered grazing systems, feeding strategies ranged from total dependence on pasture to total mixed rations (TMRTMR) and consisted of a wide variety of nutrient and energy contents. Mean pasture dry matter intake (DMI) (9 kg/cow per day, from 0.1 to 22 kg/cow per day) was just over half of total DMI. Dietary concentration of crude protein, P, K, S, Ca and Mg concentrations were, on average, 19%, 0.45%, 2.1%, 0.29%, 0.65%, and 0.3%, respectively, for all herds and, except for N, supplement nutrient concentrations were always more variable than pasture. Approximately 72% and 88% of diets provided greater than recommended P and N intakes, respectively. Calculated mean N, P, K, S, Ca and Mg excretions were 433, 61, 341, 44, 92 and 52 g/cow per day, respectively. Of the farm characteristics examined, residual maximum likelihood (REML) analysis indicated that daily excreted N, P and S were significantly related to per ha milk production, and excreted P, K and Mg were related to percentage of herd DMI provided as supplement. Mean use efficiencies by cows of N, P, K, S, Ca and Mg were 21%, 25%, 9%, 16%, 23% and 4%, respectively. These estimates of nutrient excretion and feed nutrient use efficiencies can be used to improve nutrient management on grazing system commercial dairy farms.
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http://dx.doi.org/10.3390/ani10030390DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7143236PMC
February 2020

Spatially and temporally variable urinary N loads deposited by lactating cows on a grazing system dairy farm.

J Environ Manage 2018 Jun 20;215:166-176. Epub 2018 Mar 20.

Agriculture Victoria Research, Department of Economic Development, Jobs, Transport and Resources, 1301 Hazeldean Road, Ellinbank, Victoria 3821, Australia. Electronic address:

Feed nitrogen (N) intakes in Australian grazing systems average 545 g cow day, indicating that urinary N is likely to be the dominant form excreted. Grazing animals spend disproportionate amounts of time in places on dairy farms where N accumulation is likely to occur. We attached to grazing cows sensors that measure urine volume and N concentration, as well as global positioning systems sensors used to monitor the times the cows spent in different places on a farm and the location of urination events. The cows were monitored for up to 72 h in each of two seasons. More urination events and greater urine volumes per event were recorded in spring 2014 (3.1 L) compared with winter 2015 (1.4 L), most likely influenced by environmental conditions and the greater spring rainfall observed. Mean (range) N concentration (0.71%; 0.02 to 1.52%) and N load (12.8 g cow event; 0.3 to 64.5 g cow event) did not differ over the two monitoring periods. However, mean (range) daily N load was greater in spring (277 g cow day; 200 to 346 g cow day) than in winter (90 g cow day; 44 to 116 g cow day) due to the influence of urine volume. Relatively greater time was spent in paddocks overnight (13.3 h) than in paddocks between morning and evening milking (6.4 h), compared with the mean numbers of urinations in these places (6.4 and 3.8 respectively). The mean N load deposited overnight in paddocks (89.6 g cow) was more than twice that deposited in paddocks during the day (43.8 g cow), due to the greater N load per event overnight, and was more closely linked to the relative difference in time spent in paddocks than in the number of urination events. These data suggest that routinely holding cows in the same paddocks overnight will lead to high urinary N depositions, increasing the potential for N losses from these places. Further research using this technology is required to acquire farm and environment specific urinary data to improve N management.
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http://dx.doi.org/10.1016/j.jenvman.2018.03.046DOI Listing
June 2018

Dairy farm impacts of fencing riparian land: pasture production and farm productivity.

J Environ Manage 2013 Nov 1;130:255-66. Epub 2013 Oct 1.

Future Farming Systems Research Division, Department of Environment and Primary Industries, Ellinbank Centre, 1301 Hazeldean Road, Ellinbank, Victoria 3818, Australia. Electronic address:

Dairy farmers are encouraged to restrict stock access by fencing riparian zones to reduce stream pollution and improve biodiversity. Many farmers are reluctant to create fenced riparian zones because of the perceived loss of productive pasture. Anecdotal reports indicate that pasture production in fenced areas is especially valued during summer months when water stress is likely to limit pasture growth in other areas of the farm. We measured pasture production, botanical composition, soil moisture, and fertility in Riparian (within 20 m of the riverbank), Flat (greater than 20 but less than 50 m from the riverbank), and Hill (elevated) areas on three commercial dairy farms from October 2006 to November 2007 in south eastern Australia. Riparian and Flat areas produced significantly more pasture, with on average approximately 25% more dry matter per ha grown in these areas compared with Hill paddocks. Percentage ryegrass was 14% lower on Hill slopes compared with Riparian and Flat areas and was compensated for by only a 5% increase in other grass species. Significant seasonal effects were observed with the difference in pasture production between Hill, and Riparian and Flat areas most pronounced in summer, due to soil moisture limitations on Hill paddocks. To examine potential productivity impacts of this lost pasture, we used a questionnaire-based survey to interview the farmers regarding their farm and riparian management activities. The additional pasture that would have been available if the riverbanks were not fenced to their current widths ranged from 6.2 to 27.2 t DM for the 2006/2007 year and would have been grown on 0.4-3.4% of their milking area. If this pasture was harvested instead of grazed, the farmers could have saved between $2000 and $8000 of their purchased fodder costs in that year. By fencing their riparian areas to 20 m for biodiversity benefits, between 2.2% and 9.8% of their milking area would be out of production amounting to about $16,000 in additional purchased fodder costs. We discuss the additional fencing, production, and on-going management costs associated with fencing riparian areas, the costs to the environment and the enterprise of stock freely accessing waterways, as well as the policy implications.
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http://dx.doi.org/10.1016/j.jenvman.2013.08.060DOI Listing
November 2013
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