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.

Data concerning daily milk yield (MY), percentage of milk fat (%F), protein (%P), lactose (%LT), and total solids (%TS), and somatic cell counts (SCC) for a herd of 222 Murrah buffalo reared in the state of São Paulo, Brazil, were collected monthly from 1997 to 2000 in order to study the factors affecting SCC and their relation to milk production and constituents during lactation. SCC decreased in the second month of lactation and increased thereafter, up to the ninth month of lactation. The interaction of month of lactation x order of calving was significant. Mean MY observed during the first month of lactation was 6.87 kg, which increased to 7.65 kg during the second month, and then decreased until the ninth month of lactation (3.83 kg). During the different months of lactation, %F, %P, %LT, and %TS ranged from 6.28 to 8.38%, 4.05 to 4.59%, 4.96 to 5.34%, and 16.94 to 18.55%, respectively. Calving year, calving order, and order of month of lactation significantly affected MY, %F, %P, %LT, and %TS. The regression coefficients of transformed SCC on MY and %LT were negative and significant during all months of lactation, showing that milk and lactose yield decreased with increased transformed SCC, causing losses to buffalo milk producers.

RESUMO -Os objetivos deste estudo foram estimar as tendências e os parâmetros genéticos e fenotípicos do peso padronizado aos 378 dias de idade (P378), medidas corporais e perímetro escrotal de machos Nelore, pertencentes às populações selecionadas e controle da Estação Experimental de Zootecnia de Sertãozinho. As herdabilidades, estimadas considerando-se modelo de touro e modelo animal, foram, respectivamente, 0,53±0,12 e 0,36 para P378; 0,38±0,11 e 0,58 para altura na garupa; 0,31±0,10 e 0,10 para perímetro torácico; 0,40± 0,11 e 0,13 para comprimento do corpo; 0,39±0,11 e 0,30 para comprimento do dorso; 0,33±0,10 e 0,12 para comprimento da garupa; 0,08± 0,07 e 0,14 para distância de ísquios; 0,23±0,09 e 0,08 para distância de íleos e 0,57±0,13 e 0,44 para perímetro escrotal. A correlação genética mais alta entre P378 e medidas corporais foi encontrada para perímetro torácico (0,86 ± 0,08); as demais variaram de 0,46 a 0,72. Os resultados deste estudo mostraram que, em função dos valores médios a altos das herdabilidades estimadas para P378 e da maioria das características de medidas do corpo dos animais, houve considerável variação genética aditiva nesses atributos. Além disso, devido às altas correlações genéticas de P378 com a maioria das características, pode-se concluir ser bastante provável que grande parte dos genes que controlam o peso pós-desmame também seja responsável pelo desenvolvimento das diferentes regiões do corpo de machos Nelore. A magnitude desses parâmetros justifica a tendência genética positiva nas características de seleção direta e nas secundárias.Palavras-chave: medidas corporais, parâmetros genéticos, perímetro escrotal, peso pós-desmame, tendência genética Estimates of Genetic Parameters and Trends for Body Weight at 378 Days, Body Measurements and Scrotal Circumference of Sertãozinho Nellore MalesABSTRACT -The objectives of this study were to estimate the genetic trends and also the genetic and phenotypic parameters for body weight at 378 days (W378), body measurements and scrotal circumferences of Nellore males from selected and control populations of the Estação Experimental de Zootecnia de Sertãozinho (SP), Brazil. The heritability estimates, considering sire and animal model were, respectively, 0.53± 0.12 and 0.36 for W378 days; 0.38±0.11 and 0.58 for hip height; 0.31±0.10 and 0.10 for chest girth; 0.40± 0.11 and 0.13 for body length; 0.39± 0.11 and 0.30 for dorsal line length; 0.33± 0.10 and 0.12 for rump length; 0.08 ± 0.07 and 0.14 for distance between pin bones; 0.23± 0.09 and 0.08 for distance between hip bones and 0.57± 0.13 and 0.44 for scrotal circumference. The highest genetic correlation between W378 and body measurements was found for chest girth (0.86 ± 0.08), and the others ranged from 0.46 to 0.72. Based on the median to high heritability values found for the majority of traits, it is expected to exist a good amount of additive genetic variability controlling their variation. In addition, due to the highest correlation between W378 and most of the traits, it is pr...

RESUMO -Foram utilizados dados de cinqüenta e um rebanhos participantes do Programa de Melhoramento Genético da Raça Nelore (PMGRN), distribuídos nos estados de Goiás (GO), Mato Grosso do Sul (MS), Mato Grosso (MT), Minas Gerais (MG), São Paulo (SP), Maranhão (MA) e Bahia (BA). Foram obtidas estimativas de parâmetros genéticos para os pesos padronizados aos 120 (P120), 455 (P455) e 550 (P550) dias de idade. Análises unicaráter e bicaráter foram realizadas por modelo animal usando o aplicativo MTDFREML. Para P120 foi utilizado um modelo que incluiu como efeitos fixos, grupo de contemporâneos e classe de idade da vaca ao parto, e como aleatórios, os efeitos genéticos direto, materno e de ambiente permanente da vaca. Para P455 e P550, o modelo utilizado incluiu os mesmos efeitos fixos e o efeito genético direto do animal. Nas análises unicaráter, as estimativas de herdabilidade direta foram 0,29, 0,51 e 0,47 para P120, P455 e P550, respectivamente. Nas análises bicaráter, observaram-se coeficientes de herdabilidade direta de 0,50 e 0,58 para P120, 0,50 e 0,53 para P455 e 0,44 e 0,49 para P550. As correlações genéticas estimadas entre P120 e P455, P120 e P550 e P455 e P550, foram 0,92, 0,93 e 0,96, respectivamente. As estimativas de herdabilidade obtidas para P455 e as correlações genéticas deste peso com P120 e P550 sugerem que a avaliação genética pode ser feita aos 15 meses de idade em substituição aos 18 meses.Palavras-chave: avaliação genética, bovinos, características de crescimento, Nelore, parâmetros genéticos Additive Genetic Variability Analysis in the Growth Characteristics of Nellore BreedABSTRACT -The data were obtained from 51 herds to participate in the Nelore Catttle Breeding Program (NCBP) from the states of Goiás (GO), Mato Grosso do Sul (MS), Mato Grosso (MT), Minas Gerais (MG), São Paulo (SP), Maranhão (MA) and Bahia (BA). Were used to estimative genetic parameters for standardized weights at 120 (P120), 455 (P455) and 550 (550) days of age. Univariate and bivariate analysis were performed by animal model using MTDFREML program. For P120 was used a model that included contemporary groups and cow age at calving as fixed effects, and direct genetic, maternal genetic and permanent environment effects as random effects. For P455 and P550 were utilized the same model but without maternal direct and permanent environment effects. The estimates of heritability direct from univariate analysis were: 0.29, 0.51 and 0.47 for P120, P455 and P550, respectively. In the bivariate analyses the direct heritability values were of high magnitude. The genetic correlation between P120 and P455, P120 and P550 and P455 and P550 were 0.92, 0.93 and 0.96, respectively. The values of the heritability coefficients estimated for the trait P455 and genetic correlation that characteristic with others indicate that the genetic evaluation could be made at the 15 months of age.Key Words: bovine, genetic evaluation, genetic parameters, growth traits, Nellore 1 Parte da dissertação de mestrado da 1 a autora apresentada à FCAV-UNES...

Summary This study investigated genetic trends of some productive and reproductive traits in a herd of Murrah buffalo raised in São Paulo, Brazil. Variance components for milk production (MP), length of lactation (LL), calving interval (CI) and age of first calving (AFC) were estimated by the restricted maximum likelihood method, using an animal model. Estimated heritability values were 0.38; 0.01; 0.10 and 0.20 for MP, LL, CI and AFC, respectively. Estimated repeatability values were 0.50, 0.13 and 0.20 for MP, LL and CI, respectively. Means of predicted breeding values for cows, dams and sires according to calving year and the genetic correlations were presented.

Caseins comprise make up about 80% 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.

RESUMO -Foram estimados parâmetros genéticos para pesos do nascimento aos 570 dias de idade para 35.308 animais da raça Tabapuã, nascidos entre 1975 e 2000, pertencentes à ABCZ (Associação Brasileira de Criadores de Zebu) sob três modelos distintos. O modelo 1 incluiu o efeito genético aditivo direto como aleatório, além dos efeitos fixos de grupo de contemporâneos, definido pelas variáveis: proprietário, rebanho, criador, rebanho do criador, sexo, condição de criação, ano e mês de nascimento, ano e mês da pesagem, e os efeitos linear e quadrático de idade do bezerro e idade da vaca ao parto como covariáveis. O modelo 2 compreendeu, além dos efeitos supracitados, o efeito de ambiente permanente materno. O modelo 3 constou dos efeitos genético aditivo direto e materno e de ambiente permanente materno (aleatórios) e os mesmos incluídos no modelo 1 (fixos). De acordo com o teste de razão de verossimilhança, o modelo 3 foi o mais adequado para ajustar os efeitos estudados. As estimativas de herdabilidade direta foram baixas a moderadas (0,08 a 0,26), decrescendo do nascimento às idades subseqüentes, com picos aos 90 e aos 180 dias de idade. Aos 345 dias de idade, ocorreu novo aumento nas estimativas, com menor oscilação entre as estimativas subseqüentes até 570 dias de idade. As estimativas de herdabilidade materna foram baixas, sendo maiores no período da desmama.Palavras-chave: componentes de variância, gado de corte, herdabilidade Estimation of Genetic Parameters for Weight in Different Ages in Tabapuã CattleABSTRACT -Weight records of 35.308 Tabapuã animals born between 1975 and 2000, made available by the Brazilian Zebu Breeders Association (ABCZ), were used to estimate genetic parameters for growth from birth to 570 days of age. Univariate analyses were used to fit three different models including fixed effects of contemporary group (owner, herd, sex, breeding management, year-month of birth and year-month of weight) and age of calf and age of dam (linear and quadratic) as covariates. Model 1 included only the direct genetic additive random effect; Model 2 considered both direct genetic additive and maternal permanent environmental random effects and Model 3 included the direct genetic additive, maternal, maternal permanent environmental random effects. The likelihood ratio test indicated Model 3 best fitted the data. Heritability estimates for direct genetic effects ranged between 0.08 and 0.26, decreasing after birth along the growth period, but high heritability values were observed at 90, 180 and 345 days of age, and slight changes thereafter. In general, maternal heritability estimates were low, with higher values at the weaning age.Key Words: beef cattle, heritability, variance components 1 Parte da tese de doutorado da primeira autora, financiada pela CAPES. 2 Professor da Universidade de Brasília -Faculdade de Agronomia e Medicina Veterinária (FAV) -Caixa Postal 04508-DF, CEP: 70910-900. E.mail: laila@unb.br 3 Professor Adjunto da Faculdade de Ciências Agrárias e Veterinárias (UNESP-Jaboticabal). Intro...

RESUMO -Dados de 32.779 controles mensais, de 3.605 lactações em 305 dias (PL305), de 2.082 vacas Gir, filhas de 281 touros, com partos ocorridos de 1987 a 1999, em 11 rebanhos, foram usados com o objetivo de verificar a viabilidade de utilização da produção de leite no dia do controle (PLDC1 a PLDC10) em avaliações genéticas da raça Gir. Foram realizadas análises bivariadas entre as PLDC1 a PLDC10 e PL305, usando para estimar os componentes de (co)variâncias o método de máxima verossimilhança restrita, sob modelo animal, incluindo as três primeiras lactações como medidas repetidas de uma mesma vaca, diferenciadas conforme o grupo contemporâneo de rebanho-ano-estação, de acordo com a idade da vaca ao parto e o intervalo parto-primeiro controle na PLDC1. As médias observadas e os respectivos desvios-padrão (kg) para PLDC1 a PLDC10 e PL305 foram: 11, 97±4,64; 11,93±4,68; 10,98±4,40; 10,18±4,12; 9,66±3,88; 9,20±3,69; 8,63±3,51; 8,08±3,33; 7,59±3,27; 7,22±3,15 e 2.746,17±1.299,90. A duração de lactação foi de 273,72±48,95 dias. As estimativas de herdabilidade variaram nas PLDC de 0,24 a 0,14, sendo maior no primeiro controle e decrescendo até o décimo. A herdabilidade da PL305 foi de 0,19. As estimativas de correlações genéticas entre as PLDC e PL305 variaram de 0,85 a 1,00. As correlações genéticas entre PLDC1 a PLDC9 com PLDC6 a PLDC10 foram acima de 0,80, à exceção entre PLDC9 com PLDC1 e PLDC10 com PLDC1, PLDC2, PLDC3 e PLDC6, que foram inferiores. As correlações fenotípicas tiveram valores intermediários entre as correlações genéticas e as residuais (menores). Considerando a eficiência relativa de seleção, esta mostrou que se baseada nas PLDC2 a PLDC4 ocorrerá a mesma ou melhor resposta que se praticada na PL305.Palavras-chave: bovino de leite, controle leiteiro, eficiência de seleção, melhoramento genético Genetic, Phenotypic and Environmental Parameters for Milk Production at the Control Day and 305 Days of Lactation of Gir Breed CowsABSTRACT -Data from 32,779 monthly milk production, from 3,605 lactations until 305 days (PL305), from 2,082 Gir cows, sired by 281 bulls, calving from 1987 to 1999, in 11 herds, were used to verify the viability of using daily milk production control (PLDC) to perform genetic evaluations within Gir breed. Bivariate analysis on PLDC1 to PLDC10 and PL305 were performed utilizing the restricted maximum likelihood method within an animal model, which included the three first lactations as replicate measures of the same dams unit. Animals were grouped according to the criterion of contemporaneous group of herd-year-season, and according to calvingage and to the interval calving-first control in PLDC1. The observed averages (kg) and the respective standard deviations for PLDC1 at PLDC10 and PL305 were: 11.97±4.64; 11.93±4.68; 10.98±4.40; 10.18±4.12; 9.66±3.88; 9.20±3.69; 8.63±3,51; 8.08±3.33; 7.59±3.27; 7.22±3.15 and 2746.17±1299.90. The average lactation length was 273.72±48.95 days. Heritability estimates for PLDC based on bivariate analysis ranged from 0.24 to 0.14, decreasing fr...