Célia Raquel Quirino

Evaluation of four mathematical functions to describe scrotal circumference maturation in Nellore bulls.

Four functions to characterize scrotal circumference (SC) growth in Nellore bulls were compared to identify which was the most suitable for biological interpretation. Nellore bulls (n = 532), born between September and December of 1992 to 1994 were used in the study. Measurements were made on fixed dates in January, April, July and October of each year. At the time of SC measurements, the ages of the bulls ranged from 200 to 1300 d. The functions used to describe the data were: Brody, SC = A (1 - B exp -kt); Logistic, SC = A/(1 + B exp -kt); Gompertz, SC = A exp(-B exp -kt) and Richards SC = A (1 + B exp -kt)m, where SC is the scrotal circumference at t days of age, A is the estimated SC at maturity, B is the integration constant established by the initial values of SC and t, k is the maturity constant, which equals the ratio between the maximum rate of growth and SC at maturity; m is the inflection point parameter for Richards function, which did not converge. The Brody, Gompertz and Logistic functions fitted the data in a similar fashion, with similar values for the statistics EMS and R2, and they reached convergence with similar computational costs. The Logistic function presented the best pattern of average prediction error, and therefore, it was selected for biological interpretation. For the Logistic function, estimated SC at maturity (A) was 37.95 cm at 72 mo of age. The maturity index (k) was .11 cm, and the inflection point (time of maximum growth) was reached at 13.09 mo of age at an average SC of 18.97 cm.

Genetic parameters of libido in Brazilian Nellore bulls.

Genetic, environmental and phenotypic correlations between libido, testicular measurements, body weight and semen traits were estimated by multiple-trait-restricted maximum likelihood (MTDFREML) under animal models. Reproductive records, collected from 1992 to 1997, of 288 Nellore bulls were used. Estimates of heritability for libido unadjusted, adjusted for scrotal circumference and adjusted for body weight, were 0.34 +/- 0.10, 0.31 +/- 0.10, and 0.19 +/- 0.11, respectively. Genetic correlations between libido and body weight, scrotal circumference, testis length, testis width, testis volume and testis consistency were, respectively, 0.69, -0.43, -0.31, -0.16, 0.10, 0.87, and between libido and semen volume, sperm motility, vigor, gross motility, major, minor and total defects were, respectively, 0.71, 0.51, 0.12, 0.16, 0.31, 0.26 and 0.43. Results suggested that selection for libido would be effective and that it would lead to desirable correlated response for scrotal circumference, physical and morphological semen traits and undesirable correlated response in body weight.

Lactation curves of four genetic groups of Holstein-Zebu crossbred cows

Lactation curves were fitted from 1,340 lactations of F1 Holstein-Gyr, Holstein-Guzerat, Holstein-Nellore and Holstein-Undefined Zebu crossbred cows from two farms with milk controls carried out every 14 days. Nutritional management was based on pastures in the summer, and corn silage and sugar cane with urea during winter and concentrated rations in the milking, according to the production. Incomplet Gamma function was used for estimating parameters of curves, production during lactation peak and of the time from the beginning of lactation to the peak, of persistence and total milk production. Within each genetic group, curves were adjusted for the several lactation orders. Adjusted coefficients of determination were higher than 90% for most of the curves; therefore Incomplete Gamma function adequately fitted lactation curves of F1 Holstein-Zebu cows. Curves showed initial production followed by upward phase until lactation peak and downward phase subsequent to the peak. For fifth or higher orders of Holstein-Nellore, the curve was linear and downward from the beginning. The differences among curves of the first order and others were evident for all genetic groups. Differences among initial production and production during lactation peak were not expressive, with the following means for all lactation orders: mean 2.3 kg for Holstein-Gir; 2.6 kg for Holstein-Guzerat; 1.2 kg for Holstein-Nellore and 3.5 kg for Holstein-Undefined Zebu, showing a discreet lactation peak. The mean from the beginning of lactation to the peak was 23.3 days ranging from 15.8 for Holstein-Nellore group to 32.6 days for Holstein-Undefinied Zebu. Persistence of lactation tended to decrease and initial productions, during the peak and total production increased according to lactation order. In general, Holstein-Undefinied Zebu cows show higher total production and persistence compared to the others.

Economic optimization of the number of recipients in bovine embryo transfer programs

A aquisicao e manutencao de receptoras representam grande proporcao dos custos e determinam o numero de produtos gerados em um programa de transferencia de embrioes. Entretanto, a grande variabilidade na producao de embrioes e a necessidade de adquirir e sincronizar receptoras antes de conhecer o numero de embrioes na coleta geram dificuldades na identificacao do numero ideal de receptoras pelo tomador de decisao. Nesse contexto, uma avaliacao ex-ante para determinacao do numero otimo de receptoras foi realizada por meio de analise de sensibilidade para a razao entre o numero de receptoras e de doadoras em um modelo de simulacao. Considerou-se a variabilidade no numero de embrioes coletados aplicando-se a tecnica de simulacao de Monte Carlo, assumindo-se distribuicao normal com media e variância do numero de embrioes viaveis conhecidos. Consideraram-se coletas e transferencias de embrioes em intervalos mensais durante um periodo de 24 meses. O efeito do congelamento de embrioes no numero de prenhezes foi representado modelando-se a dinâmica de um estoque de embrioes congelados. Foram comparados a razao otima entre receptoras e doadoras e o custo por prenhez de tres protocolos de sincronizacao de receptoras (prostaglandina, Progesterona P4 e Ovsynch) com base em suas respectivas taxas de sincronizacao, aptidao e prenhez. A simulacao estocastica associada com analise de sensibilidade foi efetiva em identificar a razao receptora / doadora ideal. O congelamento de embrioes foi efetivo para reduzir o custo por prenhez. A razao otima de receptoras por doadora foi afetada pelo protocolo de sincronizacao, sendo de 20 para a prostaglandina e de 16,7 para os demais protocolos. Apesar do maior custo, o protocolo P4 resultou na menor estimativa de custo por prenhez seguido pelo protocolo utilizando prostaglandina e pelo protocolo Ovsynch.

Environmental and genetic effects on the lactation curves of four genetic groups of crossbred Holstein-Zebu cows

The objective of this study was to evaluate the effects of genetic group and environmental factors, including farm of origin, season of calving and lactation number, on the individual lactation curves of 1,010 Holstein-Gyr, Guzerat-Holstein, Holstein-Nellore, and Holstein-Zebu F1 cows on the experimental farms of the Agricultural Research Company in Minas Gerais (Empresa de Pesquisa Agropecuaria de Minas Gerais, EPAMIG). Least squares analysis and the incomplete gamma function were used to investigate differences in early milk yield, peak milk yield, time from onset to the lactation peak, persistency, total milk yield and lactation duration. The highest early yields were observed for Holstein-Gyr and Holstein-Zebu, and the lowest were observed for Holstein-Nellore cows. Early yield increased with lactation number, and the lactations that began in the late rainy and early dry seasons had the highest early yield. The time between lactation onset and the lactation peak was longer for primiparous Holstein-Gyr and Holstein-Guzerat cows. The lowest yields at the lactation peak were observed for the first lactation number. The highest values of persistency were observed for the first lactation number in Holstein-Guzerat cows. Total production from Holstein-Gyr and Holstein-Zebu cows were higher by approximately 14% and 29% compared with Holstein-Guzerat and Holstein-Nellore cows, respectively. The highest total yields were observed in lactations beginning in the dry season. Total yield increased with lactation number. The shortest lactation periods were observed in lactations beginning late in the rainy season. The incomplete gamma function was used to fit the individual curves from the genetic groups evaluated. The total yield differences were linked to early yields and yields at the peak of lactation.

Morphometric Indices in Santa Ines Sheep

Los efectos de la estacion, ano de nacimiento, edad y sexo sobre indices morfometricos como: capacidad del cuerpo, indice corporal, indice del cuerpo, indice de anamorfosis, indice de compacidad y indice de proporcionalidad corporal fueron evaluados y fueran estimadas las correlaciones entre ellos. Se utilizaron ovejas Santa Ines desde el nacimiento hasta los 12 meses de edad, criadas en el norte del Estado de Rio de Janeiro. Las evaluaciones fueron realizadas durante un periodo de tres anos, totalizando 2.601 observaciones. El ano de nacimiento, el sexo, la edad del animal y la interaccion entre ellos tuvo efectos (P<0,05) sobre los indices estudiados. A partir de las medidas corporales y de los niveles de compacidad se observo que los animales tienden a presentar conformacion mas compacta. Las correlaciones entre las medidas fueron altas y positivas. Los animales estudiados muestran una conformacion longilinea, tendiendo a compacto.

Simulação e análise econômica da produção in vivo e in vitro de embriões em bovinos

The objective of this work was to evaluate the effect of the variables number of recipients, synchronization protocol, reproductive efficiency indicators and pregnancy cost, in the economic effectiveness of in vivo and in vitro bovine embryo production. A simulation application was elaborated to allow the user to insert the input variable parameters. A basic scenario, from the efficiency traditional rates of in vivo (ET) and in vitro production (IVP) techniques of bovine embryos, was introduced in the software as a criterion to compare the results. This software was able to reproduce both ET and IVP scenarios. The embryo production was simulated through stochastic simulation. The optimal number of recipients using sensitivity analysis was determined. The net present value and cost per pregnancy were used as a decision parameter. The synchronization for fixed‑time embryo transfer decreased the recipient idleness and, consequently, the final cost of pregnancy, in comparison to the traditional methodology. Foetal sexing must be associated to IVP of bovine embryos. In addition, the optimal recipient number per donor is variable and depends on data inserted in the system.

Probability density function of the number of embryos collected from superovulated Nelore breed donors

Diversos modelos tem sido desenvolvidos para avaliar o estado reprodutivo de vacas por meio da concentracao de progesterona no leite, o efeito da selecao do sexo na producao comercial de rebanhos e o desempenho bioeconomico da ovulacao multipla e transferencia de embrioes em rebanhos selecionados. No entanto, modelos que descrevem a producao de embrioes em femeas superovulados ainda tem de ser desenvolvidos. Uma funcao de densidade probabilidade para o numero de embrioes viaveis recuperados de doadoras da raca Nelore foi determinada. Dados de 61.928 coletas de 26.767 doadoras entre 1991 e 2005 foram analisados. Os resultados foram fornecidos pela Associacao Brasileira de Criadores de Zebu (ABCZ) e pela empresa Controlmax Consultoria e Sistemas Ltda.. A densidade probabilidade do numero de embrioes viaveis foi modelada utilizando as funcoes exponencial e gama. A determinacao dos parâmetros foi executada utilizando o criterio de maxima verossimilhanca em um metodo de gradiente nao linear. Ambas distribuicoes permitiram similar nivel de precisao: raiz do erro quadratico medio (RMSE) = 0.0072 e 0.0071 para a distribuicao exponencial e gama, respectivamente. Tanto a distribuicao exponencial quanto a gama foram adequadas para representar a funcao de densidade probabilidade da producao de embrioes para doadoras da raca Nelore.

Reproductive performance of Santa Inês ewes fed protected fat diet

The objective of this work was to evaluate the reproductive performance of Santa Ines ewes fed a diet supplemented with protected fat. Intervals from lambing to first clinical estrus and to conception, conception rate, prolificacy, live weight and body condition were determined. After lambing, 60 ewes and their offsprings were weighted and randomly assigned to three treatments, based on age, body weight and number of born lambs. Treatments consisted of: control diet, or control diet plus 30 g of protected fat, from lambing to day 25 of post-lambing (Sup25), or to day 60 of post-lambing (Sup60). Out of 60 evaluated ewes, 93.3% returned to estrus, and 74.5% got pregnant, with 73.53% lambing rate and 196.5 days lambing interval. The average periods from lambing to first estrus were 32.4, 27.2 and 35.5 days for ewes fed the control diet, Sup25, and Sup60, respectively. The intervals from lambing to conception were 45.2, 46.5 and 45.2 days, and the supplemented diets did not show differences in comparison to the control diet. Supplementation with protected fat to well-nourished Santa Ines ewes does not improve their reproductive performance.

Simulation and economic analysis of bovine sex selection

A simulation model implemented in the programming software Delphi XE® was applied to evaluate sex selection in bovine. The hypothesis under investigation was that a dynamic model with stochastic and deterministic elements could detect the sexed semen technique to minimize pregnancy cost and to determine the adequate number of recipients required for in vivo (ET) and in vitro embryo production (IVP) in the proposed scenarios. Sex selection was compared through semen sexed using flow cytometry (C1) and density gradient centrifugation techniques (C2) in ET and IVP. Sensibility analyses were used to identify the adequate number of recipients for each scenario. This number was reinserted into the model to determine the biological and financial values that maximized ET and IVP using sexed semen (C1M and C2M). New scenarios showed that the density gradient technique minimized pregnancy cost based on the proposed scenarios. In addition, the adequate number of recipients (ET - C1M - 115 and C2M - 105)/(IVP - C1M - 145 and C2M - 140) per donor used was determined to minimize the pregnancy cost in all scenarios.