Crescimento de codornas de diferentes grupos genéticos por meio de modelos não lineares

Data from two quail strains, UFV1 and UFV 2, measured weekly from hatch to sixth week in a total of seven live body weight traits were used aiming to estimate genetic correlations and heritabilities. After females were evaluated they were monitored in their egg-laying phase, in which the total egg number, the average weight of the eggs and the average specific gravity of eggs were measured. Multi-trait analysis was performed with the ten traits measured for estimation of heritabilities, genetic and residual correlations. For body weight traits, heritabilities varying from 0.25 to 0.53 for UFV1 and from 0.27 to 0.53 for UFV2 were estimated; genetic correlations increased as the interval between records was reduced. For egg number, the heritability estimate was of low magnitude (0.05 and 0.04), whereas for average egg weight (0.41 and 0.39) and egg specific gravity (0.31 and 0.18), they were of moderate magnitude for UFV1 and UFV2, respectively. The genetic correlations between body weights and egg number were negative in UFV1 and positive in UFV2; for average egg weight, they were positive, and for specific gravity, they were negative for both strains. It can be concluded, then, that selection based on body weight in the growth phase of meat quail must be done preferably at early ages such as weight at the third or fourth week of life, once they are positively correlated with weight at slaughter age and have few effects on the production and quality of eggs.

BackgroundLeptin has a strong relation to important traits in animal production, such as carcass composition, feed intake, and reproduction. It is mainly produced by adipose cells and acts predominantly in the hypothalamus. In this study, circulating leptin and its gene expression in muscle were evaluated in two groups of young Nellore bulls with divergent feed efficiency. Individual dry matter intake (DMI) and average daily gain (ADG) of 98 Nellore bulls were evaluated in feedlot for 70 d to determinate the residual feed intake (RFI) and select 20 animals for the high feed efficient (LRFI) and 20 for the low feed efficient (HRFI) groups. Blood samples were collected on d 56 and at slaughter (80 d) to determine circulating plasma leptin. Samples of Longissimus dorsi were taken at slaughter for leptin gene expression levels.ResultsDMI and RFI were different between groups and LRFI animals showed less back fat and rump fat thickness, as well as less pelvic and kidney fat weight. Circulating leptin increased over time in all animals. Plasma leptin was greater in LRFI on 56 d and at slaughter (P = 0.0049). Gene expression of leptin were greater in LRFI animals (P = 0.0022) in accordance with the plasma levels. The animals of the LRFI group were leaner, ate less, and had more circulating leptin and its gene expression.ConclusionThese findings demonstrated that leptin plays its physiological role in young Nellore bulls, probably controlling food intake because feed efficient animals have more leptin and lower residual feed intake.

RESUMO -Objetivou-se com este trabalho comparar diferentes modelos de regressão aleatória, ajustados por meio de funções polinomiais de Legendre de diferentes ordens, para avaliar o que melhor se ajusta ao estudo genético da curva de crescimento de codornas de corte. Os dados utilizados são provenientes de 26.835 e 27.447 observações, de 3.909 e 4.040 codornas de corte das linhagens UFV-1 e UFV-2. O peso corporal nas duas linhagens foi avaliado aos 1, 7, 14, 21, 28, 35 e 42 dias de idade. Ordens de ajuste das funções contínuas foram gradualmente aumentadas (ordens variando de 3 a 6) para determinação da ordem mínima necessária para descrever as estruturas de covariância em função do tempo nos modelos de regressão aleatória. A função polinomial de Legendre com as ordens 6 para efeito genético aditivo direto e 5 para efeito permanente de animal, para a linhagem UFV-1, e 6 para ambos efeitos aleatórios, para a linhagem UFV-2, deve ser utilizada na avaliação genética da curva de crescimento de codornas de corte em estudo. As herdabilidades estimadas indicam que ganhos genéticos podem ser obtidos como resposta à seleção para peso corporal nas duas linhagens.Palavras-chave: componente de variância, herdabilidade, polinômio de Legendre Random regression models for description of growth curve of meat quailsABSTRACT -The objective of this paper was to compare different random regression models adjusted through Legendre polynomial functions of different orders to evaluate the one best adjusted to the genetic study of the meat quail growth curve. The data used in this study were from 26,835 and 27,447 observations from 3,909 and 4,040 meat quails of the UFV-1 and UFV-2 strain, respectively. The body weight of the two strain was evaluated on 1, 7, 14, 21, 28, 35 and 42 days of age. The orders of adjustment of the continuous functions were gradually increased (orders varying from 3 to 6), to determine the least necessary order to describe structure of covariance in function of time in the random regression models.Legendre polynomial functions of the 6 th order for direct additive genetic effect and 5 th order for permanent effect, for strain UFV-1 and 6 for both random effects for strain UFV-2 should be used in the genetic evaluation of the quail meat growth curve in study. The estimated heritability indicates which genetic traits can be obtained as a response to the physical body weight selection in two strain.

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