ABSTRACT The objective of the present study was to evaluate the qPCR for detection and enumeration of Staphylococcus aureus and Streptococcus agalactiae using different milk samplings in comparison to the conventional microbiology. Four dairy herds with a history of subclinical mastitis caused by S. aureus and S. agalactiae were selected. Sampling approach included milk samples from bulk tank (BT), cow level (composite samples, CO), and mammary quarter level (MQ) from 785 lactating cows. Three consecutive monthly milk samplings were carried out, totaling 3347 MQ milk samples, 912 CO, and 12 from BT. All collected milk samples were subjected to conventional microbiology and qPCR for detection and enumeration of S. aureus and S. agalactiae. The qPCR showed 71.5% of diagnostic sensitivity for S. aureus isolated from MQ milk samples, 71.8% for CO, and 50% for BT milk samples compared with conventional microbiology methodology. Taken together, the diagnostic sensitivity for S. agalactiae isolated from MQ milk samples was 90.2, 87.7 for CO, and 90.9% for BT milk samples. In general, the qPCR methodology enabled the detection of S. aureus and S. agalactiae, regardless of the type of milk sampling. The direct use of milk samples to estimate the counting of S. aureus by qPCR demonstrated lower sensitivity than the counting of S. agalactiae, which can be explained by the pathogen infection dynamics and differences in milk sample type.

ABSTRACT We evaluated the inclusion of two crude extracts produced by Streptomyces genus on in vitro dry matter and organic matter digestibility (IVDMD; IVOMD), cumulative gas production, volatile fatty acids (VFA), and methane (CH4) and ammoniacal nitrogen (NH3-N) concentration. The experimental design was randomized blocks with three blocks and four treatments: AMC (1.2 mg/25 mL ruminal inoculum), Caat (1.2 mg/25 mL ruminal inoculum), negative control (no inclusion of extracts), and positive control (sodium monensin, 1.7 mg/25 mL ruminal inoculum). Ruminal fluid samples were collected from three multiparous Holstein dairy cows fitted with ruminal cannula and incubated in a 24-h fermentation assay. There was no effect of crude extract inclusion in comparison with negative control on cumulative gas production in 24 h. However, cumulative gas production was lower when Caat extract was included in comparison with AMC inclusion. The Caat inclusion increased propionic acid concentration and reduced the concentration of butyric acid and acetate:propionate (A:P) ratio in relation to negative control. The CH4 concentration was lower with Caat inclusion in relation to AMC, and the ratio of CH4 concentration to digestible dry matter was lower in the negative control compared with all additives. Caat inclusion decreased the NH3-N concentration, and IVDMD was not altered compared with negative control. Additionally, the inclusion of Caat crude extract increased propionic acid concentration and reduced butyric acid concentration and A:P ratio, without reducing the IVDMD and IVOMD. Caat extract modulates rumen fermentation, increasing available energy and decreasing gas production without causing changes in dry matter and organic matter digestibility.

ABSTRACT The current pricing process of raw milk in Brazil discourages producers from improving milk composition, which affects both yield and quality of dairy products. Furthermore, small and medium-sized dairies face great difficulties when it comes to planning production. Thus, a linear programming model was developed to price the raw milk and determine the optimal mix (combination of quantities) of dairy products that maximizes total contribution margin (TCM) under daily scenarios of high (January) and low (July) raw milk supplies (summer and winter, respectively) by comparing optimal solutions with actual results. The TCM of optimal and actual mixes were higher in January due to the greater availability of raw material. Packaging was a limiting factor in the production of cheese in optimal mixes. The relationship between unit contribution margin (UCM) and the required amount of raw materials per product unit and resource availability is crucial to defining the mix of dairy products and TCM of the dairy. Casein and raw milk volume showed shadow prices. Under both scenarios, the calculated prices of raw milk were higher than the prices charged by the dairy and were higher in January. The proposed model remunerates the producers based on the quantity and quality of raw milk. The dairy can maximize its TCM by better planning its mix of products with the use of linear programming.

The objective of this study was to evaluate the utilization of different sources of unsaturated long-chain fatty acids in diets for dairy cows during the transition period and early lactation on the milk fatty acid profile and composition of the protein fraction. Thirty-six Holstein cows were divided into three groups, fed the following diets: control (C); soybean oil (SO); and calcium salts of long-chain unsaturated fatty acids (CS). The milk samples utilized for analysis were obtained weekly from parturition to twelve weeks of lactation; each one of the samples originated from two daily milkings. Milk composition and total nitrogen, non-protein nitrogen and non-casein nitrogen levels were analyzed. The cows receiving the diet with calcium salts had lower concentrations of non-protein nitrogen (%CP) in milk compared with the animals fed the diet with soybean oil. There was a decrease in concentration of medium-chain fatty acids C12-C16, and a concomitant increase in concentrations of long-chain fatty acids >C18 in milk fat for the animals fed the diets CS and SO when compared with diet C. Soybean oil and CS diets increased milk-fat concentrations of the acids C18: 1 trans-11, C18: 2 cis-9, trans-11 and C18: 2 trans-10 cis-12 in relation to diet C. The utilization of sources of long-chain fatty acids in the diet of dairy cows increases the biological value of milk in early lactation due to higher concentrations of specific fatty acids such as CLA C18: 2cis-9, trans-11.

Objetivou-se avaliar o uso de fontes de ácidos graxos insaturados nas rações de vacas leiteiras sobre o balanço de nutrientes e o perfil de ácidos graxos do leite. Foram utilizadas 12 vacas Holandesas no terço médio de lactação (média de 128 dias) e (580 ± 20 kg de peso; média ± DP) com produção média de leite de 25kg/dia distribuídas aleatoriamente em três quadrados latinos balanceados 4 x 4 alimentadas com as seguintes dietas: controle (C); óleo de soja refinado; (OS); grão de soja integral (GS) e; sais de cálcio de ácidos graxos insaturados (SCAG). A produção de leite obtida foi de 26,6; 26,4; 24,1 e 25,7kg/dia para as dietas CO, OS, GS e SCAG respectivamente. As vacas alimentadas com a dieta GS produziram menos leite (1,95kg/dia), gordura e lactose em relação às vacas alimentadas com as dietas OS e SCAG. As vacas alimentadas com a dieta SCFA, apresentaram menores concentrações de nitrogênio uréico no sangue, leite, urina (g/dia), maior eficiência do uso de nitrogênio e consumo de energia em relação a dieta OS. As vacas alimentadas com as dietas contendo fontes de ácidos graxos insaturados demonstraram maiores concentrações no leite dos ácidos graxos C18:2 cis-9, trans-11 e C18:1, trans-11, em relação as vacas alimentadas com a dieta CO. O uso de grão de soja integral e óleo de soja promovem maior eficiência dos processos digestivos e aumentam as concentrações de ácidos graxos insaturados no leite de vacas leiteiras.

The objective was to evaluate the effect of unsaturated fatty acid sources supplementation on nutrients balances and milk fatty acid profile of mid lactation dairy cows. Twelve Brazilian Holstein cows in the mid lactation (mean of 128 days) and (580 ± 20kg of weight; mean ± SD) with milk yield of 25kg/d were assigned randomly into three 4 x 4 Latin square, fed the following diets: control (C); refined soybean oil; (SO); whole soybean raw (WS) and; calcium salts of unsaturated fatty acids (CSFA). Milk yield was 26.6; 26.4; 24.1 and 25.7 to the diets CO, SO, WS and CSFA respectively. Cows fed the WS treatment produced less milk (1.95kg/d of milk), fat and lactose than did cows fed the SO and CSFA. Cows fed the CSFA treatment showed less blood, urine (g/d) concentrations of N more energetic efficiency and intake of energy than did cows fed the SO treatment. Cows fed the unsaturated fatty acids sources showed more C18:2 cis-9, trans-11 CLA and trans-C18:1 FA concentration in milk than did cows fed the CO treatment. Diets with whole soybeans and soybeans oil provide more efficient digestive processes, and increase milk composition of unsaturated fatty acids.

Programs designed to enhance milk quality have been used to motivate dairy farmers to improve the quality of the raw milk they produce. The objective of this study was to evaluate the association between a milk quality payment program and four indicative variables of milk quality, by testing bulk tank somatic cell count (SCC), bulk tank total bacterial count (TBC), fat (FAT) and protein (PROT) percentages over three years in four dairy cooperatives in Southern Brazil. We used a multiple regression econometric model estimated from market data of milk delivered by farmers to the cooperatives. Bulk tank milk samples (n = 19,644) were monthly collected. The data set was analyzed for the effects of seasonality, average daily volume of milk, the award/penalty, producer, and cooperatives on SCC, TBC, FAT and PROT. Results suggested an association between the adoption of a payment program based on milk quality and the reduction of SCC and TBC. Nevertheless, the program seems to have not contributed to increase fat and protein milk percentages. This information may help the dairy industry in developing countries to conceive strategies to enhance overall milk quality.

The objective of this study was to evaluate the effect of lipid and selenium sources in diets for finishing Nellore steers on the fatty acid composition and selenium concentration of the longissimus muscle. Fifty Nellore steers (body weight = 458±39 kg) were assigned to one of six dietary treatments: 1) diet containing sunflower seed and inorganic selenium; 2) sunflower seed and organic selenium; 3) whole cottonseed and inorganic selenium; 4) whole cottonseed and organic selenium; 5) soybeans and inorganic selenium; and 6) soybeans and organic selenium. Diets were formulated with the same amount of nitrogen and calories and supplied once daily to steers in collective pens, with three animals per pen, for 120 d. At the end of the trial, steers were slaughtered and samples of the longissimus muscle were collected for fatty acid and selenium analysis. Effect of selenium sources was detected for selenium concentration in the longissimus muscle. Organic selenium had higher concentrations in the meat compared with inorganic selenium. The total saturated, monounsaturated and polyunsaturated fatty acids did not differ between the sources of lipids and selenium. For selenium sources, no differences were observed between the concentrations of polyunsaturated fat. Also, no differences in C18:2 cis-9 trans-11 concentrations were noted; however, steers fed sunflower seed presented greater proportions of this fatty acid in the meat. The results indicated that the use of sunflower seed, cottonseed or soybeans and organic or inorganic selenium in feedlot diets to Nellore cattle does not alter the great part of the fatty acid profile of the longissimus muscle. However, the inclusion of sunflower seed in the diet increases the meat CLA cis-9, trans-11, which is desirable and beneficial for the health of consumers.

The present study was carried out with the objective of evaluating the effects of feeding dairy cows with organic or inorganic sources of zinc (Zn), copper (Cu) and selenium (Se) on blood concentrations of these minerals, blood metabolic profiles, nutrient intake and milk yield and composition. Nineteen Holstein cows were selected and randomly assigned to two groups for receiving organic (n = 9) or inorganic (n = 10) sources of Zn, Cu and Se from 60 days before the expected date of calving to 80 days of lactation. Samples of feed, orts and milk were collected for analysis. Body condition score (BCS) was determined and blood samples were collected for analysis of Zn, Cu and Se concentrations, as well as for metabolic profile. Supplying organic or inorganic sources of Zn, Cu, and Se did not affect dry matter and nutrient intake, blood metabolic profile, milk yield and composition, plasma concentration of these minerals, and BCS or change the BCS in cows from 60 days before the expected date of calving to 80 days of lactation. An effect of time was observed on all feed intake variables, plasma concentrations of Zn and Se, milk yield, milk protein content, BCS and change in BCS.

O objetivo deste trabalho foi avaliar a associação entre o fluxo de leite, a morfometria dos tetos e a prevalência de mastite subclínica em vacas Gir. Oitenta vacas em 2ª ou 3ª lactação, com 90 a 200 dias de lactação, foram divididas, de acordo com o fluxo de leite durante a ordenha, nos grupos rápido ou lento. A morfometria de tetos foi avaliada por imagens de ultrassom do teto anterior direito e medidas externas dos tetos. Amostras de leite foram coletadas para a contagem de células somáticas (SCC) e a cultura microbiológica. O efeito do fluxo de leite durante a ordenha foi avaliado pela análise de variância de produção de leite, SCC, morfometria e medidas externas dos tetos. Foi analizada a associação entre a morfometria e medidas externas dos tetos e a SCC e microganismos encontrados no leite. O fluxo de leite foi significativamente correlacionado à produção de leite. As vacas Gir com fluxo de leite mais lento tinham maior comprimento de canal dos tetos e maior produção de leite, em comparação a vacas de fluxo rápido. A distância do teto ao solo influenciou a SCC das vacas Gir. A prevalência de mastite subclínica e o tipo de microrganismo causador de mastite não foram alterados pelo fluxo de leite durante a ordenha

The aim of this work was to evaluate the association between milk flow, teat morphological measurements and subclinical mastitis prevalence in Gir cows. Eighty cows in the 2nd and 3rd lactations, with 90 to 200 days of lactation, were divided according to milk flow during milking into fast or slow groups. Teat morphometry was assessed by ultrasound scanning of the right anterior teat and external measurements. Milk samples were collected for somatic cells count (SCC) and microbiological culture. The effect of milk flow during milking was evaluated by analysis of variance of milk yield, SCC, morphometry and external measurements. The association of morphometry and external measurements of the teats with the SCC and microorganisms found in milk were analysed. Milk flow was significantly correlated to milk production. Gir cows with slower milk flow had longer teat canal and greater milk yield, in comparison to cows with fast milk flow. Teat-end to floor distance influenced SCC of Gir cows. Prevalence of subclinical mastitis and the type of mastitis-causing pathogens were not affected by milk flow during milking

O objetivo deste trabalho foi avaliar o efeito da maturidade da planta sobre a qualidade nutricional do colmo de híbridos de milho, para definir critérios de seleção em programas de melhoramento de milho para ensilagem. Foram avaliados 15 híbridos de milho, do programa de melhoramento do Instituto Agronômico, em Campinas, SP, colhidos com 90, 120 e 150 dias após a germinação, em experimento com delineamento de blocos ao acaso, com três repetições. O quarto e o quinto internódios do colmo foram retirados para determinação da composição bromatológica e digestibilidade in vitro. Com o avanço da maturidade, houve queda no teor de fibra e aumento no de lignina de ambos os internódios. Observou-se aumento na digestibilidade da matéria seca do quinto internódio, mas não houve mudanças na do quarto internódio. A maturidade também reduziu a digestibilidade da fibra em detergente neutro (DIVFDN) do quarto internódio, mas não a do quinto. A DIVFDN do quarto internódio pode ser utilizada como parâmetro de seleção para aumento da qualidade nutricional de híbridos de milho. Nas três idades de corte, houve grande variabilidade genética dos parâmetros de qualidade, o que realça a possibilidade de implantação de programas de melhoramento genético para qualidade nutricional do milho para ensilagem.

The objective of this work was to evaluate the effect of plant maturing on the stalk nutritional quality of corn hybrids, in order to define selection criteria in breeding programs of maize for silage. Fifteen hybrids from the Instituto Agronômico breeding program in Campinas, SP, Brazil, harvested at 90, 120 and 150 days after germination, were evaluated in a randomized block design, with three replicates. The fourth and fifth stalk internodes were removed for determination of chemical composition and in vitro digestibility. In both internodes, fiber content decreased and lignin content increased as maturity advanced. Dry matter digestibility of the fifth internode increased with maturity, while there was no change in the fourth internode. Maturity reduced neutral detergent fiber digestibility (DIVFDN) of the fourth internode but not of the fifth one. The forth internode DIVFDN can be used as a selection criterium for nutritional quality improvement of corn hybrids. There was great genetic variability of quality parameters, among harvested hybrids at the three maturity stages, which highlights the possibility of implementing breeding programs for nutritional quality of corn for silage.

O objetivo deste trabalho foi avaliar o efeito do uso de leite com diferentes contagens de células somáticas (CCS), na qualidade do queijo minas frescal. Utilizou-se delineamento de blocos ao acaso, em esquema fatorial 3x5, com três níveis de CCS (baixa, 125.000 células mL-1; intermediária, 437.000 células mL-1; e alta, 1.053.000 células·mL-1) e cinco tempos de armazenamento. Os queijos foram embalados a vácuo, em embalagens de plástico, e analisados após 2, 9, 16, 23 e 30 dias de armazenamento a 4ºC. A contagem de células somáticas não afetou a matéria seca, a gordura, as cinzas, o pH, a concentração de ácidos graxos livres e os parâmetros sensoriais do minas frescal. A CCS no leite aumentou as perdas de proteína no soro e diminuiu o teor de proteína no queijo. Essas alterações não afetaram o rendimento com umidade ajustada e a proteólise durante 30 dias de armazenamento. Houve interação entre a CCS e o tempo de armazenamento, quanto à firmeza e às notas sensoriais dos queijos. O leite cru usado para a produção do queijo minas frescal não deve conter alta CCS, para evitar menor aceitação sensorial do produto após 30 dias de armazenamento.

The objective of this work was to evaluate the effects of using bulk milk with different somatic cell counts (SCC) on the quality of minas frescal cheese. A randomized complete block design was used, with 3x5 factorial treatments, with three SCC levels (low, 125,000 cells mL-1; intermediate, 437,000 cells mL-1; and high, 1,053,000 cells mL-1) and five storage durations. Cheese was vacuum-packed in plastic bags and analyzed after 2, 9, 16, 23 and 30 days of storage at 4ºC. Somatic cell counts did not affect dry matter, fat, ash content, pH, free fatty acid concentrations and sensory parameters of minas frescal cheese. However, SCC in milk increased losses of protein in whey and decreased the cheese protein content. These changes did not affect the moisture-adjusted cheese yield and proteolysis during 30 days of storage. An interaction effect between SCC and time of storage was observed for firmness and sensory grades of cheeses. Results indicated that raw milk used to produce minas frescal cheese should not contain high SCC, in order to avoid lower acceptance of the product after 30 days of storage.

Objetivou-se com este estudo avaliar a sensibilidade in vitro de Staphylococcus spp.frente a alguns desinfetantes comerciais utilizados no pré e pós-dipping em vacas leiteiras. Foram testados um total de 60 isolados de Staphylococcus spp. identificados como S. aureus (50) e Staphylococcus coagulase positiva (10) recuperados de glândulas mamárias de vacas com mastite subclínica procedentes das regiões Metropolitana do Recife, Agreste e Zona da Mata do Estado de Pernambuco. O estudo da eficácia dos desinfetantes utilizados no pré e pós-dipping foi realizado utilizando-se os seguintes princípios ativos: cloro (2,5%), iodo (0,57%), clorexidine (2,0%), amônia quaternária (4,0%) e ácido lático (2,0%) em quatro tempos distintos (15", 30", 60" e 300"). Observou-se que 100% de S. aureus foram sensíveis ao iodo, 93,3% sensíveis a clorexidine, 80% sensíveis a amônia, 35,6% sensíveis ao ácido lático e 97,8% resistentes ao cloro no tempo de 60". Com relação a Staphylococcus coagulase positiva (SCP), 100% dos isolados foram sensíveis ao iodo, 81,8% sensíveis a amônia quaternária, 99,9% sensíveis ao ácido lático, 72,7% sensíveis a clorexidine e 100% resistentes ao cloro no tempo de 60". Conclui-se que a maior atividade desinfetante in vitro foi verificada para o iodo e clorexidine frente a S. aureus e do iodo e ácido lático frente aos SCP e que há necessidade de avaliação periódica dos desinfetantes utilizados nas propriedades leiteiras nas regiões estudadas, pois, existem variações no perfil de sensibilidade e resistência aos desinfetantes que podem comprometer os programas de controle da mastite bovina causada por Staphylococcus spp.

The objective of this investigation was to evaluate the in vitro sensibility of Staphylococcus spp. to several commercially available disinfectants used for pre and post dipping. A total of 60 isolates of Staphylococcus spp., identified as Staphylococcus aureus (50) and Positive coagulase Staphylococcus (10) were obtained from the mammary glands of dairy cows with subclinical mastitis in the regions of Metropolitan Recife, the Agreste and the Zona da Mata of the State of Pernambuco, Brazil. As active ingredients were used a chlorine base (25%), iodine (0.6%), chlorhexidine (2.0%), quaternary ammonium (4.0%), and lactic acid (2.0%) at four specific intervals (15", 30", 60", and 300"). One hundred percent of S. aureus was found to be sensitive to iodine, 93.3% to chlorhexidine, 80% to ammonia, 35.6% to lactic acid, and 97.8% were resistant to chlorine at a 60-minute interval. With respect to the Positive coagulase Staphylococcus (SCP), 100.0% of the isolates were sensitive to iodine, 81.8% to quaternary ammonium, 99.9% to lactic acid, 72.7% to chlorhexidine, and 100% was resistant to chlorine at an interval of 60 minutes. It can be concluded that the highest disinfectant activity in vitro was found to be with iodine and chlorhexidine for S. aureus, and with iodine and lactic acid for SCP. A further conclusion was that it is important to undertake a periodic evaluation of the disinfectants used on the dairy properties in the regions studied, given the variety of sensibilities and resistance to disinfectants used, which may prejudice the control of bovine mastitis caused by Staphylococcus spp.

Avaliou-se o efeito de níveis crescentes de uréia na dieta de vacas em lactação sobre a produção e composição físico-química do leite. Foram utilizadas nove vacas holandesas em lactação, distribuídas em três quadrados latinos 3 x 3, com três tratamentos e três períodos de coleta. O experimento teve duração de 63 dias, divididos em três períodos de 21 dias. Os tratamentos consistiram de uma dieta controle, formulada para suprir 100% das exigências de PB, proteína degradável no rúmen (PDR) e proteína não-degradável no rúmen (PNDR), composta de farelo de soja como principal fonte protéica e cana-de-açúcar como volumoso, e de duas outras dietas, semelhantes à dieta controle, mas com 0,75 ou 1,5% de uréia em substituição ao farelo de soja. As dietas foram isoenergéticas (1,53 Mcal/kg de energia líquida de lactação) e isoprotéicas (16% de PB). Quando os resultados foram analisados por regressão polinomial simples, não houve efeitos das dietas sobre o consumo de MS, as produções de leite e de leite corrigida para 3,5% de gordura, os teores de proteína e gordura e a contagem de células somáticas do leite. Os níveis de substituição do farelo de soja por uréia não influenciaram o pH, a crioscopia ou a densidade do leite. No entanto, verificou-se efeito linear decrescente dos níveis de uréia na dieta sobre a acidez do leite. Os teores de proteína, gordura, lactose, uréia, extrato seco total e extrato seco desengordurado não foram afetados pelas dietas. Os resultados deste estudo sugerem que o uso de até 1,5% de uréia na MS da dieta de vacas em lactação não altera a produção, a composição e as características físico-químicas do leite.

The objective of this trial was to evaluate the effects of three different dietary levels of urea on milk yield and composition. Nine lactating Holstein cows were randomly assigned to three replicated 3 x 3 Latin squares with three periods of 21 days each. Treatments were: A) control diet formulated to meet 100% of the requirements of crude protein (CP), rumen undegradable protein (RUP) and rumen degradable protein (RDP) according to the NRC (2001) model by feeding soybean meal and sugar cane; B) replacing soybean meal with 0.75% urea; or C) replacing soybean meal with 1.5% urea. Diets were formulated to be isonitrogenous (16% CP) and isocaloric (1.53 Mcal/kg of NEl). No significant differences in dry matter intake, milk yield, 3.5% fat corrected milk, yields of milk protein and milk fat, and somatic cell count were observed among treatments when data were analyzed by simple polynomial regression. Milk cryoscopy, pH and density were also not affected by increasing the proportion of urea in the diet treatments; however, milk acidity decreased linearly when the levels of urea were increased in the diet. Milk contents of protein, fat, lactose, total solids and non-solids fat and concentration of milk urea all did not differ across diets. Results obtained in this trial indicated that the inclusion of up to 1.5% of urea (% of diet DM) in the diet had no effect on milk yield, milk composition, and milk physical-chemical characteristics in lactating cows.

O objetivo deste trabalho foi avaliar o efeito do polimorfismo genético da beta-lactoglobulina, da raça e da sazonalidade sobre as características físico-químicas e estabilidade do leite bovino. Foram selecionados 5 rebanhos da raça Holandesa e 6 da Girolando. Amostras de leite e sangue foram coletadas de 660 vacas Holandesas e 293 Girolandos, num total de 953 amostras, obtidas em duas coletas na estação seca e duas na estação chuvosa. As amostras de leite foram submetidas à análise de acidez titulável, pH, crioscopia, e ao teste de estabilidade ao etanol (70, 76, 80 e 84ºGL). As amostras de sangue foram submetidas à reação em cadeia de polimerase, para determinação do polimorfismo da beta-lactoglobulina em ambas as raças estudadas. Não houve efeito do polimorfismo da beta-lactoglobulina sobre as características físico-químicas do leite. Observou-se efeito de raça (Holandesa e Girolando, respectivamente) sobre a acidez titulável (16,16 e 17,07°D), e da sazonalidade (estações chuvosa e seca, respectivamente) sobre a crioscopia (-0,5411 e -0,5376°H). Nas condições do estudo, observou-se efeito de raça e sazonalidade sobre a estabilidade do leite, com maior instabilidade do leite de Girolando, durante a estação seca. Não houve efeito do polimorfismo da beta-lactoglobulina sobre essa característica.

The objective of this study was to evaluate the effect of beta-lactoglobulin polymorphism, breed and seasonality on physico-chemical characteristics and stability of bovine milk. Six Holstein-Zebu (H-Z) and five Holstein dairy herds were selected, of which 660 Holstein and 293 crossbred Holstein-Zebu milk and blood samples were collected, adding up 953 samples, distributed in two collecting periods at rainy and two at dry seasons. Each milk sample was analyzed for titratable acidity, pH, freezing point and milk ethanol stability, at the following ethanol concentrations: 70, 76, 80 and 84ºGL. Individual blood samples were submitted to polymerase chain reaction (PCR) for the determination of beta-lactoglobulin polymorphism. No effect of beta-lactoglobulin polymorphism was observed in physico-chemical characteristics of milk, in both studied breed. Breed effect for Holstein and H-Z, respectively, was observed on titratable acidity (16.16 and 17.07°D, while effect of seasonality (for rainy and dry seasons, respectively) was also observed on freezing point (-0.5411 and -0.5376°H). Effects of breed and seasonality on milk stability were observed (Holstein-Zebu milk was less stable on dry season), however, no effect of beta-lactoglobulin on milk stability was observed.

O objetivo do presente estudo foi avaliar os efeitos da retirada mecânica das células somáticas do leite cru sobre a composição e a proteólise durante o armazenamento refrigerado do leite pasteurizado. O delineamento experimental utilizado foi o de blocos generalizados ao acaso, no qual foram considerados como blocos as repetições (n=3) e o nível de gordura do leite (desnatado e integral). Utilizou-se um arranjo fatorial de tratamento do tipo 2 x 2, constituído por: dois níveis de contagem de células somáticas - CCS (baixa e alta CCS) e pela aplicação ou não da microfiltração ao leite. Foram realizadas, ainda, medidas repetidas no tempo, as quais corresponderam aos dias de coleta do leite pasteurizado durante o período de armazenamento (1, 7, 14 e 21 dias). Os lotes de leite cru de alta (1.000.000cél. mL-1) e baixa (100.000cél. mL-1) CCS foram submetidos ao desnate centrífugo, à microfiltração em sistema a vácuo e, em seguida, os lotes de todos os tratamentos foram pasteurizados e armazenados por 21 dias sob refrigeração a 6°C. Não foi identificado efeito da microfiltração sobre a proteólise do leite, indicando que este tratamento não reduziu a taxa de proteólise do leite de alta CCS durante o período de armazenamento. Foi observado efeito significativo do tempo de armazenamento sobre a proteólise, indicando a manutenção de atividade proteolítica mesmo após a pasteurização do leite. Pode-se concluir que o leite com alta contagem de células somáticas apresenta maior taxa de proteólise durante o período de armazenamento que o leite de baixa contagem de células somáticas. A microfiltração como processo de retirada mecânica das células somáticas do leite não reduz a proteólise do leite durante o armazenamento.

This study was aimed at evaluating the effects of raw milk somatic cell removal by microfiltration on the composition and proteolysis during refrigerated storage of pasturized milk. A completely randomized block design was used, in which repetitions (n=3) and milk fat level (skimmed and whole milks) were considered as blocks. A 2 X 2 factorial arrangement of treatments was used: milks with two different levels of somatic cell counts - low somatic cell count (LSCC) and high somatic cell count (HSCC) - and, microfiltration or not of milk. Repeated measures during storage time were taken from pasteurized milk at days 1, 7, 14 and 21. LSCC raw milk - 100,000cells mL-1 - and HSCC raw milk - 1,000,000cells mL-1 - were obtained from selected cows, skimmed and submitted to vacuum microfiltration. Milk was pasteurized and kept refrigerated at 6°C for 21 days. The application of milk microfiltration was efficient on somatic cell removal; however microfiltration had no effect on milk proteolysis which means the treatment did not reduce HSCC milk proteolysis rate during refrigerated storage. Significant effect of storage period on proteolysis was observed indicating that proteolytic activity remained despite milk pasteurization. HSCC milk proteolytic activity was 1,42 times higher than in LSCC milk, during the 21-day of refrigerated storage period. Based on the results of the study, HSCC milk shows a higher proteolytic activity than LSCC milk, during the 6°C-21 day storage period. Microfiltration, as a somatic cell removal process had no effect on decreasing proteolytic activity of pasteurized milk during the refrigerated storage period.