No abstract

Plant extracts have been proposed as substitutes for chemical feed additives due to their potential as rumen fermentation modifiers and because of their antimicrobial and antioxidant activities, possibly reducing methane emissions. This study aimed to evaluate the use of oregano (OR), green tea extracts (GT), and their association as feed additives on the performance and methane emissions from dairy between 28 and 87 d of lactation. Thirty-two lactating dairy cows, blocked into 2 genetic groups: 16 Holstein cows and 16 crossbred Holstein-Gir, with 522.6 ± 58.3 kg of body weight, 57.2 ± 20.9 d in lactation, producing 27.5 ± 5.0 kg/cow of milk and with 3.1 ± 1.8 lactations were evaluated (means ± standard error of the means). Cows were allocated into 4 treatments: control (CON), without plant extracts in the diet; oregano extract (OR), with the addition of 0.056% of oregano extract in the dry matter (DM) of the diet; green tea (GT), with the addition of 0.028% of green tea extract in the DM of the diet; and mixture, with the addition of 0.056% oregano extract and 0.028% green tea extract in the DM of the diet. The forage-to-concentrate ratio was 60:40. Forage was composed of corn silage (94%) and Tifton hay (6%); concentrate was based on ground corn and soybean meal. Plant extracts were supplied as powder, which was previously added and homogenized into 1 kg of concentrate in natural matter, top-dressed onto the total mixed diet. No treatment by day interaction was observed for any of the evaluated variables, but some block by treatment interactions were significant. In Holstein cows, the mixture treatment decreased gross energy and tended to decrease the total-tract apparent digestibility coefficient for crude protein and total digestible nutrients when compared with OR. During the gas measurement period, GT and OR increased the digestible fraction of the ingested DM and decreased CH expressed in grams per kilogram of digestible DMI compared with CON. The use of extracts did not change rumen pH, total volatile fatty acid concentration, milk yield, or most milk traits. Compared with CON, oregano addition decreased fat concentration in milk. The use of plant extracts altered some milk fatty acids but did not change milk fatty acids grouped according to chain length (short or long), saturation (unsaturated or saturated), total conjugated linoleic acids, and n-3 and n-6 contents. Green tea and oregano fed separately reduced gas emission in cows during the first third of lactation and have potential to be used as feed additives for dairy cows.

Resumo -O objetivo deste trabalho foi caracterizar a produção e a qualidade do leite em sistemas de produção da região Sul do Rio Grande do Sul e verificar a porcentagem de amostras que se enquadram nos limites determinados pela Instrução Normativa 51 (IN 51). De setembro de 2000 a agosto de 2001, exceto janeiro, foram monitoradas, mensalmente, dez unidades de produção leiteira classificadas nos seguintes sistemas de produção: especializado, semi-especializado e não especializado. Em amostras coletadas no tanque resfriador, foram avaliadas características físico-químicas do leite, realizada a contagem de células somáticas e a produção de leite foi corrigida para 4% de gordura. Houve diferença significativa entre os sistemas para produção de leite, porcentagens de gordura, lactose, caseína, sólidos totais, sólidos desengordurados, contagem de células somáticas, acidez titulável e densidade. Consideradas todas as características do leite, apenas 41,8% das amostras se enquadraram nos limites estabelecidos pela IN 51. A maior especialização dos sistemas resultou em aumento da produção de leite e menor contagem de células somáticas, além de maiores valores porcentuais da caseína, lactose e sólidos desengordurados, possivelmente pelo melhor manejo nutricional e higiene na ordenha.Termos para indexação: propriedades físico-químicas do leite, contagem de células somáticas, Instrução Normativa 51, produção de leite. Milk quality in production systems in the Southern region of Rio Grande do Sul, BrazilAbstract -The objective of this work was to characterize milk yield and quality of production systems in the southern region of Rio Grande do Sul, and verify the proportion of samples in the range allowed by Federal Normative Instruction 51 (IN 51), created to establish quality parameters for milk in the country. From September 2000 to August 2001, except January, ten dairy production units were monthly evaluated and then classified into three productions systems: specialized, partially specialized and nonspecialized. Bulk tank milk was sampled to determine physicochemical characteristics, somatic cell count and milk production was corrected to 4% milk fat. Production systems differed statistically for milk production, percentages of fat, lactose, casein, total solids, nonfat solids, somatic cell count, acidity and density. Only 41.8% of samples were in the acceptable range of IN 51 rules. Production systems greatest specialization resulted in higher milk yield, reduced somatic cell count and larger percentages for milk casein, lactose and non-fat solids, probably due to better nutritional management and milking hygiene.

A total of twelve lactating Jersey cows were used in a 5-week experiment to determine the effects of severe feed restriction on the permeability of mammary gland cell tight junctions (TJs) and its effects on milk stability to the alcohol test. During the first 2 weeks, cows were managed and fed together and received the same diet according to their nutritional requirements (full diet: 15 kg of sugar cane silage; 5.8 kg of alfalfa hay; 0.16 kg of mineral salt and 6.2 kg of concentrate). In the 3rd week, animals were distributed into two groups of six cows each. One group received the full diet and the other a restricted diet (50% of the full diet). In the 4th and 5th weeks, all animals received the full diet again. Milk composition and other attributes, such as titratable acidity, ethanol stability, pH, density and somatic cell count (SCC) were evaluated. Cortisol levels indicated the stress condition of the cows. Plasma lactose and milk sodium were measured to assess mammary TJ leakiness. Principal factor analysis (PFA) showed that the first two principal factors (PFs) contributed with 44.47% and 20.57% of the total variance in the experiment and, as feeding levels increased, milk stability to the ethanol test became higher and plasma lactose levels decreased, which indicates lower permeability of the mammary gland cell TJ. Correspondence analyses were consistent with PFA and also showed that lower feeding levels were related to reduced milk stability, high plasma lactose, high sodium in milk, low milk lactose (another parameter used to assess TJ permeability) and higher cortisol levels, indicating the stress to which animals were submitted. All observations were grouped in three clusters, with some of the above-mentioned patterns. Feeding restriction was associated with higher permeability of TJ, decreasing milk stability to the ethanol test.

RESUMO -Os efeitos dos meses do ano sobre a composição e produção do leite foram avaliados através do acompanhamento de 10 unidades produtoras de leite, divididas em três sistemas de produção classificados como especializado (ES), semi-especializado (SE) e não-especializado (NE), durante 11 meses do ano. Foram coletadas amostras de leite diretamente dos tanques refrigeradores para determinação das características físico-químicas e contagem de células somáticas (CCS). Quantificaram-se a incidência de mastite e a produção média de leite (litros/vaca/dia) e coletaram-se amostras de água utilizada para consumo e limpeza, de pastagem, concentrado e silagem. O delineamento adotado foi o completamente casualizado, em arranjo fatorial desbalanceado, considerando como fatores os meses do ano, os sistemas de produção e a sua interação. Não foi encontrada variação significativa entre os meses estudados para produção de leite, valores de crioscopia, porcentagens de gordura, extrato seco, nitrogênio não-protéico, CCS, composição química, contagem de coliformes da água e composição bromatológica do concentrado. Os maiores valores de proteína verdadeira do leite foram observados em outubro e novembro, enquanto os maiores de caseína, em outubro, novembro, março e abril. O extrato seco desengordurado foi superior em dezembro e a acidez variou juntamente com a incidência de mastite, sendo superior nos meses de novembro e maio. Em relação à proteína bruta, ocorreu interação entre meses e sistemas. Foram observadas correlações negativas entre produção de leite e gordura, mastite e CCS, e correlação positiva entre produção de leite e lactose. O leite produzido nos diversos meses do ano diferiu, principalmente, quanto à incidência de mastite, fração protéica, extrato seco desengordurado e acidez. A qualidade da água não se modificou expressivamente nos meses em que foi amostrada e se apresentou dentro dos limites considerados aceitáveis.Palavras-chave: característica físico-química do leite, contagem de células somáticas, mastite, produção de leite, variação sazonal Evaluation of Milk Quality on Different Months of Year at Pelotas Dairy Basin, RSABSTRACT -The effect of months of year upon milk production and quality was estimated through evaluation of ten dairy production units classified as specialized (S), partially specialized (PS) and not specialized (NS), which were visited on 11 months of the year. Bulk tank milk was sampled to determinate physical and chemical characteristics and somatic cell count (SCC), mastitis percentage and milk production (liters/cow/day). Besides that, samples of feeds and water used for drinking and cleaning were collected. There were not significant differences between months for milk production, crioscopy, percentages of fat, total solids, non protein nitrogen and SCC, but true protein percentages were higher on October and November, and casein showed higher values on October, November, March and April. Total solids were higher on December. Acidity varied in same way as mastitis percentage, higher on...

The effect of shade on behavior and physiological attributes of grazing cows in a high altitude subtropical zone is not well established. This work aimed to investigate how social and ingestive behaviors, as well as physiological and other attributes of dairy cows such as milk production, change in a subtropical environment during the hot season either with or without free access to shade. Fourteen lactating cows were kept on pasture either with no shade or with free access to shade for 5 days and their behavior was recorded with instantaneous scan sampled every 10 min, from sunrise, 0530 h (Greenwich mean time, GMT − 0200 h) to sunset, 2100 h (GMT − 0200 h). Behavior traits included (1) time spent in activities such as grazing, ruminating, resting, lying, standing, walking, seeking shade and staying in the proximity to the water trough and (2) number of events such as water ingestion, aggressive interactions, as well as competition for shade and water. Physiological attributes such as heart and respiratory rates, rectal temperature, number of rumen movements, panting score, as well as milk yield, were evaluated. Time spent in behavioral activities, number of behavioral events and physiological attributes varied between groups (with and without access to shade). Cows with no shade showed increased respiratory and heart rates and panting score at 1300 h, higher values for time of permanence near the water trough, number of competition and aggression events for shade. On the other hand, they showed lower values for time spent resting while lying, ruminating while standing, seeking shade. Access to shade did not change time spent lying, standing, walking with the head up, ruminating while lying, resting while standing, as well as milk yield and number of ruminal movements. Significant interactions between access to shade and days of measurements were detected for time spent walking, ruminating, grazing, resting, number of water ingestion events, competition events near the water trough and for shade, as well as for rectal temperature and panting score measured at 1700 h. In the high altitude subtropical region, access to shade minimizes negative heat stress effects on behavior and physiological aspects of dairy cows.

-The objective of this study was to investigate changes in physiological parameters of dairy cows and understand which physiological parameters show greater reliability for verification of heat stress. Blood samples were collected for analysis and included hematocrit (Ht), erythrocyte count (ERY), and hemoglobin count (HEMO). In addition, physiological variables, including rectal temperature (RT), heart rate (HR), respiratory rate (RR), and panting score (PS) were recorded in 38 lactating cows. These varied according to genetic group (½, ¾, and pure bred Holstein (HO)). Analysis of variance considering the effects of genetic group, days, and their interaction as well as linear and quadratic effect of the black globe humidity index (BGHI) was performed, as well as broken-line regression. These values were higher in pure HO than in ¾ and ½ groups. The average BGHI during the morning was 74, when 70, 43, and 13% of pure HO, ¾, and ½, respectively, presented RR above reference value. The RR was the best indicator of heat stress and its critical value was 116 breaths/min for ½, 140 for ¾, and 168 breaths/min for pure HO cows. In the HO group, physiological variables increased linearly with BGHI, without presenting inflection in the regression. The inflection point occurred at a higher BGHI for the ½ group compared with the other groups. Hematocrit and HEMO were different among genetic groups and did not vary with BGHI, showing that stress was not sufficient to alter these hematological parameters. The ½ HO group was capable of maintaining normal physiological parameters for at least 3 BGHI units above that of HO and 1 to 3 units higher than ¾ HO for RR and RT, respectively. Respiratory rate is the physiological parameter that best predicts heat stress in dairy cattle, and the 1/2 Holstein group is the best adapted to heat stress.

Resumo -O objetivo deste trabalho foi avaliar os efeitos da restrição alimentar sobre a produção de leite bovino e sobre seu perfil eletroforético de proteínas, bem como relacioná-los à estabilidade do leite pelo teste do álcool. Foram conduzidos dois experimentos com vacas Jersey: no primeiro, avaliou-se o efeito da redução de 40% na alimentação fornecida a vacas semiconfinadas; no segundo, avaliou-se o efeito da restrição de 30% do conteúdo de nutrientes digestíveis totais na alimentação de vacas confinadas. As frações proteicas foram determinadas por eletroforese, e sua quantificação por meio de análises de imagens. As amostras de leite foram classificadas conforme estabilidade no teste do álcool a 72°GL. A restrição alimentar de 40% a vacas semiconfinadas reduziu a produção de leite, mas não alterou a composição de proteínas lácteas e a estabilidade do leite; neste caso, o leite instável apresentou maiores teores de β-caseína e de proteínas totais, porém menor proporção de κ-caseína em comparação ao leite estável. A restrição de 30% do aporte energético a vacas confinadas não reduziu a produção leiteira, porém diminuiu a percentagem de albumina sérica bovina e a estabilidade no teste do álcool; neste caso, o leite instável e o estável não diferiram quanto às proteínas lácteas.Termos para indexação: b-caseína, κ-caseína, confinamento, eletroforese, leite instável não ácido, teste do álcool. Electrophoretic characterization of proteins and milk stability of cows submitted to feeding restrictionAbstract -The objective of this work was to evaluate the feeding restriction effects on milk yield and on its electrophoretic protein profile, and to relate them to milk stability to the alcohol test. Two experiments were carried out with Jersey cows: in the first one, the effect of 40% feed restriction was evaluated on semiconfined cows; in the second one, the effect of 30% reduction in total digestive nutrients was evaluated on confined cows. Protein fractions were determined by electrophoresis and their quantification was done by image analysis. Milk samples were classified according to their stability in the 72°GL-alcohol test. The 40% feed restriction for semiconfined cows decreased milk yield, but it did not change milk protein contents and stability; in this case, unstable milk showed larger contents of β-casein and total proteins, but lower κ-casein in comparison to stable milk. The 30% restriction of energy supply for confined cows did not reduce milk yield, but decreased the percentage of serum bovine albumin and milk stability; in this case, unstable and stable milk did not differ as for protein fractions.