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The objectives of the study are: 1) to determine the effects of preslaughter diet (concentrate, roughage, or concentrate plus roughage) and duration of feeding (4 or 8 d) on E. coli and other enteric bacterial populations in rumen and rectum, and contamination of skin and carcass in goats; 2) to determine the effects of feed deprivation time (6, 12, 18, or 24 h) on E. coli and other enteric bacterial populations in rumen and rectum, and contamination of skin and carcass in goats; and 3) to determine the effects of preharvest spray washing on skin and carcass bacterial counts in goats; and 4) to determine the effects of preharvest diet, feed deprivation, and spray washing on blood hormone and metabolite concentrations in goats.
Non-Technical Summary: Three experiments will be conducted to study the effects of different types of feed and feed deprivation times, combined with spray washing goats prior to slaughter on skin and carcass microbial loads. In the first experiment, goats will be subjected to one of the dietary treatments (concentrate, hay, or concentrate plus hay) prior to slaughter. Blood metabolites, bacterial populations in the gut, and on skin and carcass, as well as pH values of gut contents and muscle will be analyzed. In the second experiment, goats will be transported to the slaughter facility after being exposed to the dietary treatment that produced the best results, and then subjected to either 6, 12, 18, or 24 h of feed deprivation prior to slaughter. Blood and microbial analysis will be done as explained in the first experiment. In the third experiment, goats exposed to appropriate dietary treatment and feed deprivation time will be spray washed prior to stunning. Spray washed and unwashed control animals will be slaughtered to study the effects on skin and carcass microbial populations. Diet and feed deprivation time have been shown to influence bacterial populations in the gastrointestinal tracts of goats. Spray washing goats prior to slaughter with potable water can reduce skin contamination. Fecal contamination of animal skin is one of the main causes for carcass contaminations with pathogens. An ideal preslaughter management method that results in the least bacterial counts on goat carcasses will be identified from this project. <P> Approach: Experiment 1 (Objectives 1 & 4): Goats (n=48) will be randomly allocated to one of six dietary treatments: concentrate diet for 4 days, concentrate diet for 8 days, hay diet for 4 days, hay diet for 8 days, concentrate plus hay diet for 4 days, and concentrate plus hay diet for 8 days. Feed will be provided twice daily, and all animals will have free access to drinking water. After the feeding period, animals will be subjected to 12 h of feed deprivation and slaughtered using standard procedures. Blood samples will be collected before beginning the feeding trial (baseline) and prior to holding, and prior to slaughter of animals to assess stress responses using plasma cortisol and blood metabolites such as glucose, creatine kinase, plasma urea nitrogen, and NEFA. Muscle pH will be recorded at 0 (immediately after skinning) and 24 h postmortem. The pH values of rumen liquor and colon digesta will also be measured. Skin swabs at hind leg region will be made before subjecting the animals to feed deprivation and prior to slaughter. Carcass swab samples (flank, brisket, leg) will be made after skinning and gut removal before washing. Appropriate dilutions will be inoculated on petrifilms to determine E. coli, coliform, enterobacteriaceae, and aerobic plate counts. Experiment 2 (Objectives 2 & 4): The dietary treatment that results in the least microbial populations in the gut will be selected from Experiment 1. Goats (n=32) will be transported to the slaughter facility after the dietary treatment, and then subjected to either 6, 12, 18, or 24 h of feed deprivation prior to slaughter. Blood and microbial sampling and analysis will be done as explained in Experiment 1. Experiment 3 (Objectives 3 & 4): The diet and feed deprivation treatment combination that results in the least gut microbial populations will be selected from Experiments 1 & 2. Twenty goats will be subjected to the treatment combination selected. On the day of processing, all goats will be sampled on hind legs for total plate and E. coli counts. Ten goats will be individually subjected to a spray wash in the single file race prior to stunning, and the remaining ten goats will be stunned with no spray wash. Each sprayed animal will be moved to the stunning chute 15 minutes after spray wash to allow time for the hair coat to dry or water to drip off. All animals will be sampled again at the time of stunning for microbial load on hind legs to determine the effect of treatment. Each animal will also be blood sampled prior to and after spray washing treatment to assess stress responses. The control animals will be blood sampled at corresponding times. Animals will be processed using standard procedures. After the final wash, each carcass will be sampled for total plate count and E.coli, if any. The data from Experiments 1 & 2 will be analyzed as Randomized Complete Block Design (RCBD) with split-plot arrangement using General Linear Models Procedure in SAS (SAS Institute, 2000). Pairwise mean comparison will be done using the least significant difference (LSD) test, when significant by ANOVA (P < 0.05). The data from Experiment 3 will be analyzed as One-Way Analysis of Variance.