Random regression models for milk, fat and protein in Colombian Buffaloes / Modelos de regresión aleatoria para leche, grasa y proteína en búfalos de Colombia

Objective. Covariance functions for additive genetic and permanent environmental effects and, subsequently, genetic parameters for test-day milk (MY), fat (FY) protein (PY) yields and mozzarella cheese (MP) in buffaloes from Colombia were estimate by using Random regression models (RRM) with Legendre polynomials (LP). Materials and Methods. Test-day records of MY, FY, PY and MP from 1884 first lactations of buffalo cows from 228 sires were analyzed. The animals belonged to 14 herds in Colombia between 1995 and 2011. Ten monthly classes of days in milk were considered for test-day yields. The contemporary groups were defined as herd-year-month of milk test-day. Random additive genetic, permanent environmental and residual effects were included in the model. Fixed effects included the contemporary group, linear and quadratic effects of age at calving, and the average lactation curve of the population, which was modeled by third-order LP. Random additive genetic and permanent environmental effects were estimated by RRM using third- to- sixth-order LP. Residual variances were modeled using homogeneous and heterogeneous structures. Results. The heritabilities for MY, FY, PY and MP ranged from 0.38 to 0.05, 0.67 to 0.11, 0.50 to 0.07 and 0.50 to 0.11, respectively. Conclusions. In general, the RRM are adequate to describe the genetic variation in test-day of MY, FY, PY and MP in Colombian buffaloes.

Objetivo. Fueron estimadas funciones de covariancia para los efectos genéticos aditivos y de ambiente permanente, y posteriormente fueron estimados los parámetros genéticos para la producción de leche en el día del control (PDC) para leche (MY), grasa (FY), proteína (PY) y producción de queso mozzarella (MP), usando modelos de regresión aleatoria (RRM) mediante Polinomios Ortogonales de Legendre (LP) en búfalos de Colombia. Materiales y Métodos. Fueron analizados 1884 registros de PDC de primeras lactancias para MY, FY, PY y MP, hijas de 228 reproductores. Los registros procedían de 14 rebaños entre 1995 y 2011. Para las PDC fueron consideradas 10 clases mensuales de días en lactancia. Los grupos contemporáneos fueron definidos como rebaño-año-mes de control. Fueron incluidos en el modelo efectos aleatorios genético aditivo, de ambiente permanente y residual. Los efectos fijos incluidos fueron grupo contemporáneo, efecto lineal y cuadrático de edad al parto, y curva promedia de la lactancia de la población, la cual fue modelada por un LP de tercera orden. Los efectos aleatorios genético aditivo y de ambiente permanente fueron estimados por RRM mediante LP de tercero a sexto orden. Las variancias residuales fueron modeladas usando estructuras homogéneas y heterogéneas. Resultados. Las heredabilidades para MY, FY, PY y MP variaron de 0.38 a 0.05, 0.67 a 0.11, 0.50 a 0.07 y 0.50 a 0.11, respectivamente. Conclusiones. En general, los RRM son adecuados para describir la variación genética para la PDC de MY, FY, PF y MP en búfalos de Colombia.

Estimation of genetic parameters for test-day milk yield in first calving buffaloes / Estimación de parámetros genéticos para producción de leche en el día de control en búfalas de primer parto / Estimação de parâmetros genéticos para produção do leite no dia do controle em búfalas de primeiro parto

Background: the milk yield records measured along lactation provide an example of repeated measures; the random regression models are an appealing approach to model repeated measures and to estimate genetic parameters. Objective: to estimate the genetic parameters by modeling the additive genetic and the residual variance for test-day milk yield in first calving buffaloes. Methods: 3,986 test-day data from 1,246 first lactations of crossbred buffalo daughters of 23 sires and 391 dams between 1997 and 2008 from five farms were used. The model included the genetic and permanent environment additive as the random effect and the contemporary group (year, month of test-day) and age at calving as covariable (linear) fixed effects. The fixed (third order) and random (third to ninth order) regressions were obtained by Legendre polynomials. The residual variances were modeled with a homogeneous structure and various heterogeneous classes. The variance components were estimated using the WOMBAT statistical program (Meyer, 2006). Results: according to the likelihood ratio test, the best model included four variance classes, considering Legendre polynomials of the fourth order for permanent environment and additive genetic effects. The heritabilities estimates were low, varying from 0.0 to 0.14. The estimates of genetic correlations were high and positive among PDC1 and PDC8, except for PCD9, which was negative. This indicates that for any of the selection criteria adopted, the indirect genetic gain is expected for all lactation curves, except for PCD9. Conclusion: heterogeneity of residual variances should be considered in models whose goal is to examine the alterations of variances according to day of lactation.

Antecedentes: los registros de producción de leche medidos a lo largo de la lactancia son un ejemplo de medidas repetidas, los modelos de regresión aleatoria presentan un enfoque atractivo para modelar medidas repetidas y para estimar parámetros genéticos. Objetivo: estimar parámetros genéticos a través de la modelación de la varianza genética y residual para producción de leche en el día de control en búfalas de primer parto. Métodos: fueron analizados 3986 controles de producción de leche en la primera lactancia de 1246 búfalas, hijas de 391 hembras y 23 toros, durante los años 1997 hasta 2008 en 5 fincas. El modelo incluyó como efectos aleatorios genético aditivo y de ambiente permanente, como efectos fijos grupo contemporáneo compuesto por mes, año de control y la covariable de la edad de la búfala al parto (lineal). Las regresiones fijas (3er orden) y aleatorias (3er a 9no orden) fueron obtenidas mediante polinomios de Legendre. Las varianzas residuales fueron modeladas con una estructura homogénea y varias clases heterogéneas. Los componentes de varianza fueron estimados utilizando el programa WOMBAT. Resultados: de acuerdo con la prueba de la razón de verosimilitud, el mejor modelo fue con 4 clases de varianzas residuales, siendo considerado un polinomio de Legendre de cuarto orden para el efecto de ambiente permanente y genético aditivo. Las heredabilidades fueron bajas, variando desde 0,00 hasta 0,14. Las correlaciones genéticas fueron altas y positivas entre los PDC1 a PDC8, excepto en el PDC9 que fue negativo con respecto a los demás controles. Conclusiones: es necesario considerar la heterogeneidad de varianzas residuales en los modelos estudiados, con el fin de modelar los cambios en las variaciones respecto a los días en lactancia.

Antecedentes: os registros da produção do leite medidos ao longo da lactação, apresentam um exemplo de medidas repetidas. Os modelos de regressão aleatória apresentam abordagem atraente para modelar medidas repetidas e estimar parâmetros genéticos. Objetivo: estimar parámetros genéticos mediante a modelação das variâncias genéticas e residual da produção do leite no dia do controle em búfalas de primeiro parto. Métodos: foram analisados 3986 controles de produção de leite em primeiras lactações de 1246 búfalas, filhas de 391 fêmeas e 23 touros, entre 1997 e 2008 em 5 fazendas. No modelo foram incluídos como efeitos aleatórios o genético aditivo e ambiente permanente, e como fixos o grupo contemporâneo (mês e ano de controle) e a covariável a idade da búfala ao parto (Lineal). As regressões fixas (3° ordem) e aleatórias (3° a 9° ordem) foram obtidas mediante polinômios ortogonais de Legendre. As variâncias residuais foram modeladas mediante estruturas homogêneas e diferentes classes heterogêneas. Os componentes de variância foram estimadas mediante o software WOMBAT. Resultados: de acordo com a prova da máxima verossimilhança, o melhor modelo foi com 4 classes de variâncias residuais, sendo considerado polinômios de Legendre de quarto ordem para o efeito de ambiente permanente e genético aditivo. As herdabilidades foram baixas, variando desde 0,00 até 0,14. As correlações genéticas foram altas e positivas entre o PDC1 e PDC8, a exceção do PDC9 que apresentou valores negativos com respeito aos outros controles. Conclusões:é necessário considerar heterogeneidade de variâncias nos modelos estudados, tentando modelar as mudanças nas variações respeito aos dias em lactação.

Effect of lactation length adjustment procedures on genetic parameter estimates for buffalo milk yield

The objectives of this study were to estimate the genetic parameters for milk yield unadjusted and adjusted for days in milk and, subsequently, to assess the influence of adjusting for days in milk on sire rank. Complete lactations from 90 or 150 days of lactation to 270 or 350 days in milk were considered in these analyses. Milk yield was adjusted for days in milk by multiplicative correction factors, or by including lactation length as a covariable in the model. Milk yields adjusted by different procedures were considered as different traits. Heritability estimates varied from 0.17 to 0.28. Genetic correlation estimates between milk yields unadjusted and adjusted for days in milk were greater than 0.82. Adjusting for days in milk affected the parameter estimates. Multiplicative correction factors produced the highest heritability estimates. More reliable breeding value estimates can be expected by including short length lactation records in the analyses and adjusting the milk yields for days in milk, regardless of the method used for the adjustment. High selection intensity coupled to the inclusion of short length lactations and adjustment with multiplicative factors can change the sire rank..

Genetic parameters for milk, fat and protein yields in Murrah buffaloes (Bubalus bubalis Artiodactyla, Bovidae)

The objective of the present study was to estimate genetic parameters for test-day milk, fat and protein yields and 305-day-yields in Murrah buffaloes. 4,757 complete lactations of Murrah buffaloes were analyzed. Co-variance components were estimated by the restricted maximum likelihood method. The models included additive direct genetic and permanent environmental effects as random effects, and the fixed effects of contemporary group, milking number and age of the cow at calving as linear and quadratic covariables. Contemporary groups were defined by herd-year-month of test for test-day yields and by herd-year-season of calving for 305-day yields. The heritability estimates obtained by two-trait analysis ranged from 0.15 to 0.24 for milk, 0.16 to 0.23 for protein and 0.13 to 0.22 for fat, yields. Genetic and phenotypic correlations were all positive. The observed population additive genetic variation indicated that selection might be an effective tool in changing population means in milk, fat and protein yields.

Factores ambientales que afectan el recuento de células somáticas en leche de búfalos (Bubalus bubalis) / Environmental factors that affect milk somatic cell count in buffaloes (bubalus babalis)

Considerando que el recuento de células somáticas (RCS) de muestras de leche es un valioso indicador de la salud de la ubre de búfalas, se desarrolló el presente trabajo con el fin de estimar la relación existente entre algunos factores ambientales y el RCS, verificando la frecuencia de ocurrencia de muestras analizadas en clases de recuentos muy altos, altos, medios y bajos. Fueron analizadas informaciones de 23.534 muestras de controles de leche (RCS), referentes a 2.198 lactancias de animales de la raza murrah con edades entre los dos y quince años, hijas de 187 reproductores; estos muestreos fueron realizados durante siete años. Loa resultados indicaron que de manera general, ocurrieron bajos, medios, altos y muy altos RCS para, 96,34 por ciento,2,3 por ciento, 0,96 por ciento y 0,4 por ciento de las muestras, respectivamente. Las clases de bajos y medios RCS, fueron las que presentaron las mayores frecuencias, confirmando que en búfalos, hay una tendencia a menores recuentos que en los bovinos. Se presentaron diferencias entre las medias del RCS por orden de parto y por estación de parto, y hubo diferencias estadísticamente significativas (p < 0.05) para las medias del RCS en algunos controles. En relación con el orden del parto fueron observadas diferencias entre las frecuencias de los RCS, siendo que, de modo general, a medida que aumentó el orden del parto, disminuyó el porcentaje de bajos recuentos y aumentaron las frecuencias de recuentos medios, altos y muy altos. Los resultados indicaron que los efectos de hacienda, año y orden de parto deben ser considerados en la comparación entre animales...

Estimation models of variance components for farrowing interval in swine

The main objective of this study was to evaluate the importance of including maternal genetic, common litter environmental and permanent environmental effects in estimation models of variance components for the farrowing interval trait in swine. Data consisting of 1,013 farrowing intervals of Dalland (C-40) sows recorded in two herds were analyzed. Variance components were obtained by the derivative-free restricted maximum likelihood method. Eight models were tested which contained the fixed effects(contemporary group and covariables) and the direct genetic additive and residual effects, and varied regarding the inclusion of the maternal genetic, common litter environmental, and/or permanent environmental random effects. The likelihood-ratio test indicated that the inclusion of these effects in the model was unnecessary, but the inclusion of the permanent environmental effect caused changes in the estimates of heritability, which varied from 0.00 to 0.03. In conclusion, the heritability values obtained indicated that this trait appears to present no genetic gain as response to selection. The common litter environmental and the maternal genetic effects did not present any influence on this trait. The permanent environmental effect, however, should be considered in the genetic models for this trait in swine, because its presence caused changes in the additive genetic variance estimates.

Este trabalho teve como objetivo principal avaliar a importância da inclusão dos efeitos genético materno, comum de leitegada e de ambiente permanente no modelo de estimação de componentes de variância para a característica intervalo de parto em fêmeas suínas. Foram utilizados dados que consistiam de 1.013 observações de fêmeas Dalland (C-40), registradas em dois rebanhos. As estimativas dos componentes de variância foram realizadas pelo método da máxima verossimilhança restrita livre de derivadas. Foram testados oito modelos, que continham os efeitos fixos (grupos de contemporâneo e covariáveis) e os efeitos genético aditivo direto e residual, mas variavam quanto à inclusão dos efeitos aleatórios genético materno, ambiental comum de leitegada e ambiental permanente. O teste da razão de verossimilhança (LR) indicou a não necessidade da inclusão desses efeitos no modelo. No entanto observou-se que o efeito ambiental permanente causou mudança nas estimativas de herdabilidade, que variaram de 0,00 a 0,03. Conclui-se que os valores de herdabilidade obtidos indicam que esta característica não apresentaria ganho genético como resposta à seleção. O efeito ambiental comum de leitegada e o genético materno não apresentaram influência sobre esta característica. Já o ambiental permanente, mesmo sem ter sido significativo o seu efeito pelo LR, deve ser considerado nos modelos genéticos para essa característica, pois sua presença causou mudança nas estimativas da variância genética aditiva.

â-casein gene polymorphism permits identification of bovine milk mixed with bubaline milk in mozzarella cheese

Mozzarella cheese is traditionally prepared from bubaline (Bubalus bubalis) milk, but product adulteration occurs mainly by addition of or full substitution by bovine milk. The aim of this study was to show the usefulnes of molecular markers to identify the admixture of bovine milk to bubaline milk during the manufacturing process of mozzarella cheese. Samples of mozzarella cheese were produced by adding seven different concentrations of bovine milk: 0%, 1%, 2%, 5%, 8%, 12% and 100%. DNA extracted from somatic cells found in cheese were submitted to PCR-RFLP analysis of casein genes: alfa-s1-CN - CSN1S1 that encompasses 954 bp from exon VII to intron IX (Alu I and Hinf I), beta-CN - CSN2 including 495 bp of exon VII (Hae III and Hinf I), and k-CN - CSN3, encompassing 373 bp of exon IV (Alu I and Hind III). Our results indicate that Hae III-RFLP of CSN2 exon VII can be used as a molecular marker to detect the presence of bovine milk in "mozzarella" cheese.

Test-day milk yield as a selection criterion for dairy buffaloes (Bubalus bubalis Artiodactyla, Bovidae)

Due to the great demand for buffalo milk by-products the interest in technical-scientific information about this species is increasing. Our objective was to propose selection criteria for milk yield in buffaloes based on total milk yield, 305-day milk yield (M305), and test-day milk yield. A total of 3,888 lactations from 1,630 Murrah (Bubalus bubalis) cows recorded between 1987 and 2001, from 10 herds in the State of São Paulo, Brazil, were analyzed. Covariance components were obtained using the restricted maximum likelihood method applied to a bivariate animal model. Additive genetic and permanent environmental effects were considered as random, and contemporary group and lactation order as fixed effects. The heritability estimates were 0.22 for total milk yield and 0.19 for M305. For test-day yields, the heritability estimates ranged from 0.12 to 0.30, with the highest values being observed up to the third test month, followed by a decline until the end of lactation. The present results show that test-day milk yield, mainly during the first six months of lactation, could be adopted as a selection criterion to increase total milk yield.

Kappa-casein gene study with molecular markers in female buffaloes (Bubalus bubalis)

Caseins comprise make up about 80 percent of the total protein content of milk and present polymorphism with changes in the amino acid sequence. Within this abundance of proteins, kappa-casein is noteworthy, since it has been associated with differences in milk yield, composition and processing. The objective of this study was to observe the existence of polymorphism in the kappa-casein gene in female buffaloes. For this purpose, blood samples from 115 female buffaloes, collected with vacutainer by needle punctionure of the jugular vein, were used. for genomic DNA extraction was done from blood samples. The PCR-RFLP and SSCP techniques demonstrated that the studied animals were monomorphic for the kappa-casein gene. Only allele B was observed in these animals, which was present in homozygosis. Therefore, it was not possible to quantify the gene action on milk yield and its constituents. The monomorphism observed in the population studied would allow the development of a method to identify mixtures of cow and buffalo milk in mozzarella cheese production, especially because, in cattle, the kappa-casein gene is polymorphic.

Factores de ajuste para producción de leche en bovinos Holstein colombiano / Adjustment factors for milk yield in colombian holstein cattle

El objetivo de este trabajo fue estimar factores multiplicativos de ajuste de la producción de leche a 305 días de lactación (PC305) y a edad adulta (PCEA), para rebaños de la raza Holstein colombiano.Fueron utilizadas 116.818 lactaciones de 48.707 vacas, provenientes de los archivos de la Asociación Holstein de Colombia. Los análisis estadísticos fueron realizados mediante la utilización de modeloslineales mixtos usando un modelo animal y el método de máxima verosimilitud restricta (REML). Para producción de leche a 305 días los efectos fijos considerados en el modelo fueron: grupo contemporáneo(rebaño-año), grupo genético de la vaca, mes de parto, número de partos y clases de duración de la lactación en dos grupos de edad de la vaca (<36 y ³ 36 meses) y la covarible edad de la vaca al parto (efecto lineal y cuadrático). Para producción de leche a edad adulta los efectos fijos considerados en el modelo fueron: grupo contemporáneo (rebaño-año), grupo genético de la vaca y clases de edad, número de partos y época de parto. Los efectos aleatorios para las dos variables fueron: efecto genético aditivo, ambiente permanente y residuo. Posteriormente fueron realizados análisis de variancia entre producciones de leche corregidas y no corregidas para determinar la efectividad de la aplicación de losfactores, indicando que la aplicación de los factores de corrección si ajustaron eficientemente producciones de leche para los efectos de duración de la lactación, edad de la vaca, número de partos y época de parto. La mayor producción de leche fue alcanzada por vacas de tres o más partos con edad de 76 a 83 meses de edad y partos ocurridos entre agosto y noviembre.