CASE STUDY: IMPACT OF HYPODERMA LINEATUM UPON LIVE GROWTH, CARCASS ATTRIBUTES, AND HIDE VALUE OF FED BEEF CATTLE
Guadian Garcia, Daniel Ernesto
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A case study was done at the West Texas A&M University Research Feedlot, Canyon, from 14 November 2014 to 5 August 2015. While processing crossbred bulls (n=32) upon arrival (d0), some animals in the load of cattle were identified to be infested with grubs, later identified as the common cattle grub, Hypoderma lineatum (Villers). Metaphylaxis was administered upon arrival (d 0) to the feedlot; additionally, cattle were vaccinated against respiratory viruses, dewormed, and individually identified. Cattle were placed on a starter ration (d0) and transitioned to a finishing ration by d45. Twelve days after arrival, all cattle were re-weighed and manually palpated to quantify infestation by grubs; a hide map was used to record the location of the individual grubs. Grubs were manually extracted from the left side of infested animals to assess potential need for physical removal; right side grubs remained in the animals. Also, on d12, animals were administered a growth-promoting implant, and band-castrated. Two grub-infested cattle were slaughtered (d18) at the WTAMU Meat Laboratory to document hide damage; hides were manually fleshed and converted into rawhide. Two animals (grub-free) died from bovine respiratory disease during the study period (d15, d50). The remaining cattle were reweighed (d12, d40, d70, d96, d124, d152, d180, d208, d234, d236, and d264) to assess potential differences in growth rate. Cattle were slaughtered in two groups (n=9 on d234; n=19 on d264) at a local beef processor. Data collected during slaughter and grading processes included individual animal identification, liver score, hot carcass weight, longissimus muscle area, 12th rib subcutaneous fat depth, kidney-pelvic-heart fat, yield grade, marbling score, and quality grade. Hides were individually identified and tracked through the facility to hide processing. Hides were green de-fleshed, lime de-fleshed, and de-haired for 24 h. Hides were then exposed to blue-chroming chemicals for 24 h; subsequently, blue-chrome hides were individually graded as #1, #2, or #3 hides. No difference in initial weight (P = 0.89), finished weight (P = 0.35), average daily gain (P = 0.59), hot carcass weight (P = 0.38), longissimus muscle area (P = 0.91), 12th rib subcutaneous fat depth (P = 0.64), calculated yield grade (P = 0.84), or kidney-pelvic-heart fat (P = 0.38) was detected between grub-free and grub-infested cattle. Grub-infested cattle tended to have more marbling (P = 0.07) than grub-free cattle. No difference in hide damage or value occurred between left sides (manually extracted) and right sides (grubs allowed to remain). Infestation by grubs did not negatively affect growth or carcass attributes. Hide damage in feeder calves resolved during the finishing period and grub-damaged hides met #1 criteria. Timely application of avermectin can prevent this problem from reducing beef system value.