Susantha Jayasundara

Anti-methanogenic effects of monensin in dairy and beef cattle: A meta-analysis

Monensin is a widely used feed additive with the potential to minimize methane (CH4) emissions from cattle. Several studies have investigated the effects of monensin on CH4, but findings have been inconsistent. The objective of the present study was to conduct meta-analyses to quantitatively summarize the effect of monensin on CH4 production (g/d) and the percentage of dietary gross energy lost as CH4 (Ym) in dairy cows and beef steers. Data from 22 controlled studies were used. Heterogeneity of the monensin effects were estimated using random effect models. Due to significant heterogeneity (>68%) in both dairy and beef studies, the random effect models were then extended to mixed effect models by including fixed effects of DMI, dietary nutrient contents, monensin dose, and length of monensin treatment period. Monensin reduced Ym from 5.97 to 5.43% and diets with greater neutral detergent fiber contents (g/kg of dry matter) tended to enhance the monensin effect on CH4 in beef steers. When adjusted for the neutral detergent fiber effect, monensin supplementation [average 32 mg/kg of dry matter intake (DMI)] reduced CH4 emissions from beef steers by 19±4 g/d. Dietary ether extract content and DMI had a positive and a negative effect on monensin in dairy cows, respectively. When adjusted for these 2 effects in the final mixed-effect model, monensin feeding (average 21 mg/kg of DMI) was associated with a 6±3 g/d reduction in CH4 emissions in dairy cows. When analyzed across dairy and beef cattle studies, DMI or monensin dose (mg/kg of DMI) tended to decrease or increase the effect of monensin in reducing methane emissions, respectively. Methane mitigation effects of monensin in dairy cows (-12±6 g/d) and beef steers (-14±6 g/d) became similar when adjusted for the monensin dose differences between dairy cow and beef steer studies. When adjusted for DMI differences, monensin reduced Ym in dairy cows (-0.23±0.14) and beef steers (-0.33±0.16). Monensin treatment period length did not significantly modify the monensin effects in dairy cow or beef steer studies. Overall, monensin had stronger antimethanogenic effects in beef steers than dairy cows, but the effects in dairy cows could potentially be improved by dietary composition modifications and increasing the monensin dose.

Using automated soil water content measurements to estimate soil water budgets

The distribution of precipitation into the components of a soil water budget has a profound impact on crop growth, groundwater recharge, soil erosion, and groundwater and surface water contamination levels. The main objectives of this study were to develop a new method of measuring soil water balances and to demonstrate the use of the method in examining differences between partitioning of water in conventional tillage (CT) and no-tillage (NT) management systems. Hourly precipitation, evapotranspiration, and changes in soil water storage data were collected automatically over a 3-yr period at a field site near Elora, Ontario. Runoff and interception were calculated as the difference between measured increases in soil water storage and total rainfall during each significant rain event when the soil was not frozen. Drainage was then calculated, as it was the only component of the soil water balance not measured. The amount of soil water stored in the NT system was greater than the CT system during the latte...

Transformations and losses of swine manure 15N as affected by application timing at two contrasting sites.

An improved understanding of the fate of manure N is necessary for developing efficient manure management plans that ensure adequate crop nutrition and minimum environmental problems. This study quantified the fate of 15N-labelled liquid swine manure applied at three different times (late-fall, spring pre-plant and side-dress) on two soil types (a well-drained fine sandy loam and an imperfectly drained silt loam). Manure N uptake by corn (Zea mays L.) was significantly lower with fall application than with two spring applications (14-18% vs. 30-38% of applied N) in both soil types. Manure application increased total N leaching (30-43 vs. 27 kg N ha-1 yr-1 in the control), especially with fall application. Manure N contributed 18-25% of the total N leached in the fine sandy loam and 8-10% of the total N leached in the silt loam. Application timing did not affect manure N leaching in the silt loam, which ranged between 3 and 5% of applied N. In the fine sandy loam, fall application resulted in significantly...

Greenhouse gas emissions intensity of Ontario milk production in 2011 compared with 1991

Jayasundara, S. and Wagner-Riddle, C. 2014. Greenhouse gas emissions intensity of Ontario milk production in 2011 compared with 1991. Can. J. Anim. Sci. 94: 155-173. For identifying opportunities for reducing greenhouse gas (GHG) emissions from milk production in Ontario, this study analyzed GHG intensity of milk [kg CO2 equivalents kg-1 fat and protein corrected milk (FPCM)] in 2011 compared with 1991 considering cow and crop productivity improvements and management changes over this period. It also assessed within-province variability in GHG intensity of milk in 2011 using county-level data related to milk production. After allocating whole-farm GHG emissions between milk and meat using an allocation factor calculated according to the International Dairy Federation equation, GHG intensity of Ontario milk was 1.03 kgCO2eq kg-1 FPCM in 2011, 22% lower than that in 1991 (1.32 kg CO2eq kg-1 FPCM). Greenhouse gas sources directly associated with dairy cattle decreased less (21 and 14% for enteric fermentation and manure management, respectively) than sources associated with feed crop production (30 to 34% for emissions related to N inputs and farm-field work). Proportions of GHG contributed from different life cycle activities did not change, with enteric fermentation contributing 46%, feed crop production 34%, manure management 18% and milking and related activities 2%. Within province, GHG intensity varied from 0.89 to 1.36 kg CO2eq kg-1 FPCM, a variation inversely correlated with milk productivity per cow (kg FPCM sold cow-1 year-1). The existence of a wide variation is strong indication for potential further reductions in GHG intensity of Ontario milk through the identification of practices associated with high efficiency.