Impact of Feed Delivery Pattern on Aerial Particulate Matter and Behavior of Feedlot Cattle †

SIMPLE SUMMARY: Fine particulate matter (with less than 2.5 microns diameter; aka PM(2.5)) are a human and animal health concern because they can carry microbes and chemicals into the lungs. Particulate matter (PM) in general emitted from cattle feedlots can reach high concentrations. When feedlot cattle were given an altered feeding schedule (ALT) that more closely reflected their biological feeding times compared with conventional morning feeding (CON), PM(2.5) generation at peak times was substantially lowered. Average daily generation of PM(2.5) was decreased by 37% when cattle behavior was redirected away from PM-generating behaviors and toward evening feeding behaviors. Behavioral problems such as agonistic (i.e., aggressive) and bulling (i.e., mounting each other) behaviors also were reduced several fold among ALT compared with CON cattle. Intake of feed was less and daily body weight gain tended to be less with the altered feeding schedule while efficiency of feed utilization was not affected. Although ALT may pose a challenge in feed delivery and labor scheduling, cattle had fewer behavioral problems and reduced PM(2.5) generation when feed delivery times matched with the natural drive to eat in a crepuscular pattern. ABSTRACT: Fine particulate matter with less than 2.5 microns diameter (PM(2.5)) generated by cattle in feedlots is an environmental pollutant and a potential human and animal health issue. The objective of this study was to determine if a feeding schedule affects cattle behaviors that promote PM(2.5) in a commercial feedlot. The study used 2813 crossbred steers housed in 14 adjacent pens at a large-scale commercial West Texas feedlot. Treatments were conventional feeding at 0700, 1000, and 1200 (CON) or feeding at 0700, 1000, and 1830 (ALT), the latter feeding time coincided with dusk. A mobile behavior lab was used to quantify behaviors of steers that were associated with generation of PM(2.5) (e.g., fighting, mounting of peers, and increased locomotion). PM(2.5) samplers measured respirable particles with a mass median diameter ≤2.5 μm (PM(2.5)) every 15 min over a period of 7 d in April and May. Simultaneously, the ambient temperature, humidity, wind speed and direction, precipitation, air pressure, and solar radiation were measured with a weather station. Elevated downwind PM(2.5) concentrations were measured at dusk, when cattle that were fed according to the ALT vs. the CON feeding schedule, demonstrated less PM(2.5)-generating behaviors (p < 0.05). At dusk, steers on ALT vs. CON feeding schedules ate or were waiting to eat (standing in second row behind feeding cattle) at much greater rates (p < 0.05). Upwind PM(2.5) concentrations were similar between the treatments. Downwind PM(2.5) concentrations averaged over 24 h were lower from ALT compared with CON pens (0.072 vs. 0.115 mg/m(3), p < 0.01). However, dry matter intake (DMI) was less (p < 0.05), and average daily gain (ADG) tended to be less (p < 0.1) in cattle that were fed according to the ALT vs. the CON feeding schedules, whereas feed efficiency (aka gain to feed, G:F) was not affected. Although ALT feeding may pose a challenge in feed delivery and labor scheduling, cattle exhibited fewer PM(2.5)-generating behaviors and reduced generation of PM(2.5) when feed delivery times matched the natural desires of cattle to eat in a crepuscular pattern.