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Potentials and flaws of using 3-dimensional models to describe changes in energy reserves in dairy cattle.

L. G. R. Pereira

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06-23-2020

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Abstract:

T74
Potentials and flaws of using 3-dimensional models to describe changes in energy reserves in dairy cattle.
J. H. M. Viana1, E. K. N. Arashiro2, L. G. B. Siqueira3, L. G. R. Pereira*3. 1Embrapa Recursos Gen�ticos e Biotecnologia - Embrapa Bras�lia, DF, Brazil, 2Universidade Federal Fluminense Niter�i, RJ, Brazil, 3Embrapa Gado de Leite Juiz de Fora, MG, Brazil.

The mobilization of energy reserves during lactation determines changes in body shape, which are used to score body condition (BCS) by visual inspection. Recently, new strategies have been proposed to automatize BCS evaluation. Three-dimensional (3D) scanning can be used to obtain geometric data from body surface, however, its use to predict energy reserves still needs validation in cattle. In this study, structured infrared light scanning (Kinect sensor, Microsoft) was used to create 3D models of the rump and dorsal regions of Holstein x Gir crossbred dairy cows (n = 65). The 3D models were used to measure the average (right and left sides) area (A3D; mm2) between the sky surface and a reference line drawn: 1) between transverse and spinous processes of the lumbar vertebra near the 13th rib, for the loin; 2) between tuber coxae and tuber ischiae prominences, for in the ilium-ischium depression; and 3) between both tuber ischiae prominences, for the ischiorectal fossa. Measurements were performed with a 3D modeling software (Rhinoceros 3D 5.0, McNeel). The subcutaneous fat thickness (SFT) was measured by ultrasonography, using a 3.5 MHz, liner array probe (Aquila Vet, Esaote), at the insertion of biceps femoris muscle and at the region of longissimus dorsi muscle, between 12th and 13th ribs. Cows were visually scored for BCS in a 1 to 5 scale. The association among A3D, SFT, and BCS was evaluated by correlation and regression analysis, correlations were compared using the Pearson and Filon's test (comparingcorrelations.org). All estimations of energy reserves by SFT and A3D were correlated with BSC (P < 0.05). However, A3D was equivalent to SCF for describing changes in BCS when measured at the rump (R = 0.72 vs. R = 0.81; P > 0.05), but not at the loin (R = 0.47 vs. R = 0.81; P < 0.001). There was a quadratic effect of BCS on A3D, and in cows with BCS above 4, SCF was better than A3D for describing variations in energy reserves (P < 0.05). In summary, changes in rump 3D surface geometry can be effectively used to estimate energy reserves in non-obese cows.

Keywords: 3-dimensional imaging, BCS, precision dairy farming.