Zebu breeds play an important role in cattle production systems in Brazil. To assess the genetic variability from animals in the Herd Books of Nelore, Gir and Guzerat breeds, generation intervals, inbreeding, effective population size and parameters of gene origin (effective number of founders, ancestors and founder genomes) were calculated using pedigree records from 1938 to 1998. Breed subdivision was quantified by Wright's F-statistics. Calculations were separately carried out for consecutive 4-year intervals in the period 1979-98. Generation interval was around 8 years for the three breeds. Total inbreeding increased in all the breeds reaching values of 2.13%, 2.28% and 1.75%. Effective population size decreased from 85 to 68 in Nelore, from 70 to 45 in Gir and remained nearly constant around 104 in Guzerat. The quantities assessing the number of contributing ancestors decreased with time in all the breeds, and in the last analysed period the most important ancestor accounted for 14%, 3.1% and 4.1% in Nelore, Gir and Guzerat, respectively. Results indicate that the studied breeds are suffering from a loss of genetic variability which can result in negative effects on breeding and conservation purposes.

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Gestation length and birth weight of 939 calves born at Santa Monica Experimental Station, Valenc,a, State of Rio de Janeiro, were studied. The calves were of six red and white Holstein-Friesian (HF) x Guzera (G) grades: 1/4, 1/2, 5/8, 3/4, 7/8 and =s 31/32.As the grade x sex interaction for birth weight was significant, data for each sex were analysed separately. A model, including the effects of grade, year-season of birth, grade x year season interaction and age of dam as a covariate, resulted in the following least-square means for the six grades in the above order (± s.e.): gestation length for cows carrying male calves, 290-0 (± 0-9), 281-2 (± 0-9), 285-3 (± 0-8), 278-8 (± 0-9), 280-5 (± 0-9) and 279-3 (± 0-9) days; gestation length for female calves, 287-5 (± 0-9), 280-1 (± 1-0), 285-3 (± 0-9), 274-5 (± 1-1), 279-2 (± 0-9) and 276-4 (± 1-0) days; birth weight for males, 34-6 (± 0-7), 28-6 (± 0-8), 34-2 (± 0-7), 32-4 (± 0-7), 35-0 (± 0-7) and 34-7 (± 0-7) kg; birth weight for females, 29-9 (± 0-6), 29-5 (± 0-7), 33-4 (± 0-6), 31-9 (± 0-7), 33-6 (± 0-6) and 32-6 (± 0-6) kg.Direct (g 1 ) and maternal (g M ) breed additive effects (HF -G), and direct (h 1 ) and maternal heterosis \h M ) were estimated. The estimates of g 7 , g M , h 1 and h M were respectively, for gestation length for male calves: -21-5 (± 1-9), 10-6 (± 2-1), 1-5 (± 1-8) and -1-6 (± 11) days; for gestation length, for female calves: -21-9 (± 2-1), 14-6 (± 2-5), 5-7 (± 2-1) and -1-5 (± 1-2) days; for birth weight of male calves: -3-5 (+ 1-5), 7-1 (± 1-8), -0-6 (± 1-5) and 1-0 (± 0-9) kg; and for birth weight of female calves: 4-7 (+ 1-4), 4-1 (± 1-6), 2-8 (± 1-3) and 2-0 (± 0-8) kg. The difference in birth weight between males and females was 4-7 (± 0-9) for G-sired calves and 0-8 (± 0-4) for HF-sired calves. 157

RESUMO O objetivo deste estudo foi investigar as relações entre o peso corporal e as medidas corporais altura de garupa (ag), comprimento de garupa (cg), comprimento corporal (cc) e perímetro torácico (pt), 0,807; 0,440; 0,187 e 0,504 para vacas; 0,928; 0,735; 0,819 e 0,880 machos, e 0,942; 0,748; 0,902 0.807, 0.440, 0.187 and 0.504 for cows, 0.928, 0.735, 0.819 and 0.880 for males and 0.942, 0.748, 0.902 and 0.573 INTRODUÇÃOA determinação do peso corporal dos animais é importante para avaliar o crescimento e o estado nutricional, administrar adequadamente remédios e parasiticidas, estabelecer o valor de venda do animal de corte e ajustar o arraçoamento. Entretanto, a realidade econômica das fazendas leiteiras do Brasil muitas vezes não permite a aquisição de balanças para realizar a pesagem dos animais. Para minimizar tal deficiência, pode ser utilizada a alternativa de se predizer o peso por meio de algumas medidas corporais.

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RESUMO -O objetivo deste trabalho foi determinar valores econômicos para utilização em índices de seleção para proteína, gordura e leite sem gordura e proteína (veículo), apropriados para os sistemas de pagamento de duas importantes empresas de laticínios do Paraná e de Minas Gerais. Foram calculados os preços de cada um desses componentes, sendo os preços de proteína, gordura e veículo de, respectivamente, 1,35; 1,89 e 0,17 R$/kg, no Paraná, e 0,20; 0,80 e 0,20 R$/kg, em Minas Gerais. Os custos de alimentação e ordenha desses componentes, estimados com base nos dados da literatura sobre os respectivos requerimentos de energia e fluxo lácteo, foram subtraídos dos preços, obtendo-se valores econômicos de, respectivamente, 0,821; 0,880 e 0,122 R$/kg, para proteína, gordura e veículo, no Paraná, e -0,328; -0,210 e -0,153 R$/kg, na mesma ordem, em Minas Gerais. Os valores econômicos da proteína e gordura foram menores (até negativos) que os praticados nos principais países produtores de leite, em decorrência dos baixos preços pagos por esses componentes no Brasil.Palavras-chave: gado de leite, gordura, índice de seleção, proteína, valor econômico Economic Weights for Selection of Milk Fat and ProteinABSTRACT -The objective of this paper was to determine the economic weights for the use in selection index for protein, fat and milk without fat and protein (carrier) appropriated for the payment systems of two important milk processors in the States of Parana and Minas Gerais. The prices of each one of those components were calculated, and the prices for protein, fat and carrier were 1.35, 1.89 and 0.17 R$/kg, in Parana, and 0.20, 0.80 and 0.20 R$/kg, in Minas Gerais, respectively. The feed and milking costs of these components, estimated from literature data on their energetic requirements and milk flow, were substracted from the prices, yielding economic values of 0.821, 0.880 and 0.122 R$/kg, respectively, for protein, fat and carrier, in Parana, and -0.328, -0.210 e -0.153 R$/ kg, in the same order, in Minas Gerais. The economic values for protein and fat were lower (or even negative) than the values reported for those components in the most important milk producing countries, due to the low prices paid for them in Brazil Key Words: dairy cattle, economic value, milk fat, milk protein, selection index Rev. bras. zootec., 29(3):678-684, 20001 Professor do Departamento de Zootecnia da Escola de Veterinária da UFMG, Bolsista do CNPq. IntroduçãoO pagamento por qualidade do leite vem recebendo certa atenção no Brasil, inclusive com a recente criação do Conselho Nacional de Qualidade do Leite. A qualidade do leite envolve a composição e as condições sanitárias (MONARDES, 1998), mas, no Brasil, os programas considerados de "pagamento por qualidade", geralmente, incluem uma série de fatores relacionados às condições de produção, que não medem a qualidade em si, como o volume e a sazonalidade, a infra-estrutura, o manejo, a raça do reprodutor, os cuidados sanitários etc. Em levantamento realizado pela revista Leite B (ANÔNIM...

Linear y = a' + b'x and gamma type y = e"~c x x b models for the lactation curve (y = daily production on day x of lactation) were adjusted to daily production records of 870 lactations. Withinlactations pooled R 2 = 0-71 and R 2 = 0-74 were respectively obtained for the linear and gamma type models, the latter being preferred for further analyses on account of its general validity under varied circumstances.