UC Davis

Beef and dairy production have been an environmental concern due to their contribution to climate change and other criteria pollutants. In the United States and particularly California this concern led to increased research and regulation into mitigating environmental impacts from beef and dairy cattle production systems. The goal of the present dissertation was to review current literature related to the environmental impacts of emissions from beef and dairy production and the feed and manure additives that can be used to mitigate these emissions and to present research related to mitigating gaseous enteric and manure-based emissions from beef and dairy cattle. Chapter one presents a review of the current literature surrounding beef- and dairy cattle’s environmental impact in relation to climate change and air quality and the feed and manure additives that can be used to reduce these gaseous emissions. This literature review covers the most relevant literature on beef and dairy cattle’s impact on climate change, including methane (CH4) and nitrous oxide (N2O) emissions and the relevant feed additives for enteric and manure mitigation of these gases. This chapter also covers the criteria pollutant ammonia and feed and manure mitigation strategies. Chapter two investigates the potential of a commercial feed additive SOP STAR COW (SOP) to reduce enteric emissions from dairy cows as well as to determine any impacts on dairy cattle performance. Twenty Holstein cows were blocked by parity and days in milk before being randomly assigned to either a treatment group (n = 10; supplemented with 8 g/day SOP) or a control group (n = 10, not supplemented). Head chambers were used to measure enteric emissions over a 12-hour period every 14 days for six weeks. Overall, SOP treated- vs control cows were similar in enteric emissions and milk parameters on respective test days and throughout the experiment. Over time SOP treated cows showed a reduction in CH4 of 20.4% from day 14 to day 42 (P = 0.014). Protein content (%) of the milk was increased in SOP treated cows by 4.9% from day 0 to day 14 (P = 0.036) and 6.5% from day 0 to day 42 (P = 0.002)). No differences were detected in yield of milk protein within the SOP-treated cows over the trial period. Chapter three aimed to determine the efficacy of feeding ractopamine hydrochloride (RAC) for the last 42 d of the finishing period for beef cattle to reduce ammonia (NH3) emissions and improve animal performance. Ractopamine is an orally active, β1–adrenergic agonist (β1AA) that is used to increase lean muscle mass in beef cattle during finishing. A randomized complete block design was used in which 112 Angus and Angus crossbred steers with initial body weights (BW) of 566.0 ± 10.4 kg were assigned to 8 cattle pen enclosures (CPE). This study utilized two treatments a control (CON; finishing ration containing no RAC) and a treatment (RAC; finishing ration containing 27.3 g ractopamine/907 kg dry matter (DM) basis RAC). Body weights were collected on d -1, 0, 14, 28, and 42. Gaseous emissions collection included NH3, N2O, CH4, hydrogen sulfide (H2S), and carbon dioxide (CO2). Emissions were standardized by both live weight (LW) and hot carcass weight (HCW). On day 43 steers were harvested and carcass data were collected. Steers fed RAC vs. CON rations showed lower ammonia by 17.21% from d 0 to 28 (P = 0.032) and a trend for lower emissions from d 0 to 42 by 11.07% (P = 0.070). Steers fed RAC vs. CON showed increased reduction in NH3 that occurred when NH3 emissions were standardized for LW with a 23.88% reduction from d 0 to 14 (P = 0.018), 17.80% from d 0 to 28 (P = 0.006), and 12.50% for d 0 to 42 (P = 0.027). When NH3 was standardized by HCW, steers supplemented RAC vs CON had 14.05% (P = 0.013) lower cumulative NH3 emissions. Hydrogen sulfide was also reduced in steers fed RAC vs. CON rations with a 29.49% reduction from d 0 to 14 (P = 0.009) and a tendency to be reduced by 11.14% (P = 0.086) over d 0 to 28. RAC fed steers vs. CON steers showed reduced H2S emissions when standardized for LW at 28.81% from d 0 to 14 (P = 0.008). RAC vs. CON fed steers also tended to increase average daily gain (ADG) by 0.24 kg/d (P = 0.066) and reduced feed intake by 4.27% (P = 0.069) on a DM basis. A 19.95% increase (P = 0.012) in gain to feed ratio, a 12.52 kg greater HCW (P = 0.006), and 1.93 percentage units increase in dressing percent (P = 0.004) were observed in RAC treated vs. CON steers. Ractopamine simultaneously increased beef cattle performance as well as reduced NH3 emissions resulting in a promising feed additive to help reduce the environmental impacts of beef cattle production. The objective of chapter 4 was to determine if a pistachio shell biochar product could be administered to high nitrogen containing anaerobic digester effluent as a means of reducing gaseous NH3 emissions. A completely randomized block design was used with a total of 18 barrels divided between three treatments with six barrels per treatment (n = 6), a high dose of 4% biochar (HB; 40 g/L), a low dose 1% biochar (LB 10 g/L), and a control containing no biochar (CON). Six flux chambers were used to measure NH3, CH4, CO2, and N2O emissions from barrels containing 75.71 L of effluent each plus respective treatments. Flux chambers were rotated every 24 h to measure a subsequent block of 6 barrels, resulting in gaseous emissions monitoring every 3 days for a total of 31 days. Effluent was measured daily for pH, temperature, and oxidation reduction potential (ORP). On days 1, 16, and 31 effluent samples were collected to be analyzed for percent solids, moisture, total nitrogen, ammonia nitrogen, nitrite/nitrate, organic nitrogen, and total Kjeldahl nitrogen. The LB and HB treatment vs CON barrels pH (7.66 and 7.61 respectively) were reduced (7.83; P < 0.001). Oxidation reduction potential was increased from -46.3 mV to -36.8 mV and 33.7 mV for CON vs. LB and HB respectively (P < 0.001). No differences were detected for any gas parameters or effluent sample wet chemistry parameters. Pistachio shell biochar from gasification cannot be recommended for NH3 mitigation of digester effluent; however, other types of biochar may prove more effective and should be researched further. When considering the mitigation potential of feed or manure additives to reduce greenhouse gasses and other criteria pollutants from beef and dairy cattle it is important to consider both reduction potentials and animal performance as a reduction in meat or milk produced reduces the efficiency of the animal and may lead to increased overall emissions if herd size is increased to compensate for a reduction in efficiency. Sustainable feed and manure additive solutions will consist of available, cost effective, and either performance enhancing or no negative effects on animal performance.