Banca de DEFESA: MARILENE DOS SANTOS MACIEL

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : MARILENE DOS SANTOS MACIEL
DATE: 01/02/2022
TIME: 09:00
LOCAL: ON-LINE
TITLE:

EVALUATION OF SANTA INES SHEEP CARCASSES: A MULTIVARIATE APPROACH

KEY WORDS:

carcass classification, factorial scores, orthogonal rotations, body measurements, stepwise selection

PAGES: 90
BIG AREA: Ciências Agrárias
AREA: Zootecnia
SUMMARY:

Multivariate analysis corresponds to a set of methods that simultaneously use information from all response variables in the interpretation of the data set, taking into account the correlations between them. Among the sets of multivariate methods we can highlight factor analysis, multiple regression analysis and multivariate discriminant analysis. These methods have in common the objective to reduce the dimensionality of the data. Considering that a large number of variables are used in the carcass evaluation, there is the possibility that many of them contribute little to the discrimination of the evaluated individuals, as they are redundant due to the high correlations. Based on the above, the objective was to assess the adequacy of factor analysis and rotational methods through factor analysis; predict carcass tissue composition using factor analysis compared to classical multiple regression analysis and; distinguish groups of sheep as a function of conformation score and carcass finish and identify the variables that most contribute to differentiation, through multivariate discriminant analysis. Information from 122 sheep of the Santa Inês breed was used, comprising 24 carcass characteristics: Empty body weight (EBW); Body weight at slaughter (BWS); Hot carcass weight (HCW); Could carcass weight (CCW); Biological yield (BY); Hot carcass yield (HCY); Cold carcass yield (CCY); External carcass length (EXL); Internal carcass length (ICL); Rump width (RW); Chest width (CW); Rump perimeter (RP); Leg perimeter (LP); Chest perimeter (CP); Leg (LEG); Loin (LOI); Ribs (RIB); Neck (NEC); Blade Shoulder (BLA); Leg yield (LEGY); Loin yield (LOIY); Rib yield (RIBY); Neck yield (NECY); Blade Shoulder yield (BLAY). The KMO test (Kaiser-Meyer-Olkin) indicated that the carcass variables evaluated were suitable for the application of factor analysis. Among the rotations tested, the Varimax orthogonal rotation presented the simplest structure for interpreting the constructed factors. Classical multiple regression analysis produced a better prediction for tissue composition (higher R² and lower MSE) compared to multiple regression analysis using the factor scores from the multivariate factor analysis. R² values ranged from 0.584 to 0.636 for muscle proportion, 0.198 to 0.351 for bone proportion and 0.496 to 0.579 for total fat proportion. Indicating low to moderate accuracy, in this case, more adequate independent variables should be used to better predict the tissue proportion in Santa Inês sheep. In the multivariate discriminant analysis, the variables with the highest discriminatory power for carcass conformation scores were CCW, EXL and NEC and for carcass finishing were BWS, EXL and CP. Multivariate discriminant analysis proved to be efficient to allocate the animals to their original groups (carcass scores).

BANKING MEMBERS:
Externo à Instituição - ROBERTO GERMANO COSTA - UFPB
Externa à Instituição - MARIA ANTÔNIA REVIDATTI
Externa à Instituição - JANAINA KELLI GOMES ARANDAS
Interna - 1819750 - LAURA LEANDRO DA ROCHA
Presidente - 337405 - MARIA NORMA RIBEIRO