Abstract #T191
Section: Production, Management and the Environment
Session: Production, Management & the Environment II
Format: Poster
Day/Time: Tuesday 7:30 AM–9:30 AM
Location: Exhibit Hall B
Session: Production, Management & the Environment II
Format: Poster
Day/Time: Tuesday 7:30 AM–9:30 AM
Location: Exhibit Hall B
# T191
Does a 500-ohm shunt resistor accurately characterize the electrical resistance of adult dairy cattle?
R. Norell*1, J. Spencer2, A. Ahmadzadeh2, M. E. de Haro Marti3, M. Chahine4, 1University of Idaho, Idaho Falls, ID, 2University of Idaho, Moscow, ID, 3University of Idaho, Gooding, ID, 4University of Idaho, Twin Falls, ID.
Key Words: resistance, stray voltage
Does a 500-ohm shunt resistor accurately characterize the electrical resistance of adult dairy cattle?
R. Norell*1, J. Spencer2, A. Ahmadzadeh2, M. E. de Haro Marti3, M. Chahine4, 1University of Idaho, Idaho Falls, ID, 2University of Idaho, Moscow, ID, 3University of Idaho, Gooding, ID, 4University of Idaho, Twin Falls, ID.
By Idaho statute, a 500-ohm shunt resistor must be used when investigating stray voltage on dairies and represents a “worst case” body resistance (BODYR) value for adult dairy cows (USDA stray voltage handbook 696, 1992). BODYR data from the 80s were typically collected from cows in tie stall barns and may not represent modern open lot and free-stall dairies. Our study objectives were to compare: (a) BODYR of 6 cow pathways, (b) effect of wet versus dry haircoats, and (c) 3 electrical connections to the mouth area. BODYR data were collected from 42 cows on a commercial open lot dairy in Idaho. Pathways were: front to rear hooves (FR), neck to all hooves (NALL), rump to all hooves (RALL), mouth to all hooves (MALL), mouth to front hooves (MF), and mouth to rear hooves (MR). NALL and RALL were tested with wet and dry haircoats and data were analyzed as a 2 × 2 factorial model in SAS. MALL, MF, and MR were evaluated with 3 mouth area connections (nose tongs (NT), metal bit (MT), and metal basket (MB)) and data were analyzed as a 3 × 3 factorial model in SAS. BODYR varied significantly between pathways and ranking median BODYR (ohms) from lowest to highest value yields: MALL (255), RALL-wet (314), MF (360), MR (361), FR (469), NALL-wet (544), RALL-dry (9,185) and NALL-dry (820,000). BODYR was significantly lower for rump versus neck location, for wet versus dry haircoats, and exhibited a significant location by haircoat status interaction due to significantly lower BODYR with dry rump versus dry neck. Cows were measured immediately after milking and the rump or udder may have received water spray or contacted wet pipework during milking. BODYR with the mouth connections and pathways were significantly lower for MALL than MF or MR; for NT versus MT and MB; and exhibited a significant interaction between mouth connections and hoof pathways. The percentage of measurements below 500 ohms varies by pathway: MALL (98%), MF (98%), MR (96%), RALL-wet (82%), FR (69%), NALL-wet (34%), RALL-dry (5%) and NALL-dry (0%). A 500-ohm shunt resister overestimates BODYR and underestimates electrical current flow at a given voltage for MALL, MF, MR, RALL-wet, and FR pathway. Contact method and haircoat condition influence measured BODYR of cows.
Key Words: resistance, stray voltage