Applications of alternative technologies, intelligent dual-energy x-ray Absorptiometry (idxa) and infrared imaging, in swine sciences
Petry, Amy Leann
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The objective of the following thesis which includes two studies is to evaluate the efficacy of Intelligent Dual-energy X-ray absorptiometry (iDXA) technology as an alternative to the comparative slaughter technique for estimating available energy contents of sorghum grain and sorghum DDGS; and to evaluate the efficacy of using infrared imaging as an alternative for monitoring core body temperature in pigs. In Exp 1, twenty-nine gilts (BW 71.34 ±1.42) were randomly assigned to pens in groups of three or four. Pens were randomly assigned to 1 of 3 isocaloric and isonitrogenous dietary treatments: a conventional corn soybean based diet (n=9), 30% inclusion of sorghum grain (n=10), and 30% sorghum dried distiller grain solubles (n=10), and fed for 56 d. Initial BW, final BW, ADG, ADFI, and F:G for each treatment group was measured. The last 3 d of each 28 d period, fecal samples were collected for energy and nitrogen digestibility measurements. On d 56, blood plasma was collected and analyzed for antioxidant concentration. Prior to treatment application, 15 gilts from each treatment were scanned using iDXA, where lean mass, and lipid mass were measured to determine initial body composition. Body composition was analyzed again using iDXA for all gilts over a 2 d period, d 28 and 29, and again at, day 56 and 57. Dietary treatment GE was measured using bomb calorimetry, DE was determined using the indicator technique and TiO2 as an indigestible marker, ME was calculated by multiplying the lipid and protein deposition of the animal by the energetic cost of deposition, and NE was calculated by multiplying the lipid and protein deposition of the animal by the amount of energy in each g of deposition. Estimates of ME and NE for sorghum and sorghum DDGS were measured using a modified approach to the difference method, by subtracting the related energy contribution of the basal diet in terms of ME and NE from the sorghum and DDGS diets. Body composition and growth performance metrics did not differ among treatments (P>0.05). Sorghum diet was significantly lower in digestibility of N, GE and DE (P<0.01). However, there was no differences in ME and NE across treatments (P>0.05). Estimates of ME for sorghum grain and sorghum DDGS are 3294 and 3679, and NE are 2590 and 2287, respectively. Antioxidant levels tended to be higher in DDGS and sorghum treatments (P=0.07). Concluding, iDXA technique for measuring retained energy can offer greater accuracy for estimating ME and NE by taking multiple measurements, increasing the statistical power. From these results we can conclude that sorghum DDGS and sorghum have the same feeding value as corn in terms of ME, NE, growth performance, and body composition. The use of sorghum grain or sorghum DDGS in finishing pigs could give producers greater economic flexibility in diet formulation without sacrificing growth performance or changes in body composition. In study two, 23 gilts (BW 30.5 ±5.62 kg) were housed in metabolism crates in an environmentally controlled facility while being slightly feed restricted. After four days of adaptation, the febrile response was induced by intramuscular injection of E. coli lipopolysaccharide (LPS; 25µg/kg BW). Each pig’s BT was recorded at times 0, 2, 4, 6, 8, 10, and 24 hours post-LPS challenge, using the following three methods: (I) RT, (II) IR imaging of the eye and ear, and (III) CBT. Statistical analysis was carried out in a completely randomized design in SAS using Mixed, Correlation and Regression procedures. Relative to time 0, LPS increased the eye temperature, CBT, and RT by 0.92, 1.32, and 1.48 °C, respectively (P < 0.01), but had no significant effect on ear temperature. Eye temperature, RT, and CBT, but not ear temperature, were highly correlated (r ≥ 0.96) during the course of the study (P < 0.01). Estimated regression parameters (α and β) for predicting CBT using eye temperature were -28.2 ±8.70 and 1.76 ±0.221, and for RT were -24.5 ±7.69 and 1.65 ±0.196 (R2 ≥ 0.96; 95 % confidence interval). Collectively, these results indicated a strong relationship between eye temperature, RT and CBT in pigs. Therefore, IR of the eye can be used as a precise, non-contact alternative to RT measurements for monitoring CBT in swine.