RESUMO: Este estudo teve como objetivo avaliar o efeito da inclusão de diferentes doses de fitase em rações para frangos de corte com diferentes níveis de fitato e níveis reduzidos de cálcio (Ca) e fósforo disponível (Pd) sobre seu desempenho. Foram utilizados 1.404 frangos machos Cobb®500, distribuídos em delineamento inteiramente casualizado, em esquema fatorial 2x3, com dois níveis de fitato (4,25 kg / ton - MP e 6,0 kg / ton - HP) e três níveis de fitase (0, 750 e 1500 FTU / kg), com nove repetições por tratamento. Foram avaliados os parâmetros de desempenho, e aos 21 dias de idade, quatro frangos por repetição foram abatidos para coleta do conteúdo ileal para análise do coeficiente de digestibilidade ileal aparente (CDIA), e foram removidas a tíbia direita de um frango por repetição para quantificar seu peso e porcentagem de resíduo mineral (% RM), Ca e P. Aos 42 dias de idade, uma ave por repetição foi abatida para medir o rendimento de carcaça e cortes. Os animais que receberam fitase na dieta apresentaram maior consumo médio de ração e ganho de peso médio, e maior peso ósseo, % RM, % Ca e % P, quando comparados ao tratamento sem fitase (P < 0,01). Os animais que receberam dieta contendo HP com inclusão de 1500FTU / kg de fitase apresentaram os melhores CDIAs de nutrientes (P < 0,0001). Em relação ao fitato, os animais que receberam a dieta MP apresentaram maior CDIA de matéria seca e maior %P na tíbia quando comparados aos animais que receberam a dieta HP. A adição de fitase a dietas com níveis reduzidos de Ca e Pd pode melhorar os CDIAs e as características ósseas na presença de níveis elevados de fitato. No entanto, a redução dos níveis de Ca e Pd na dieta sem adição de fitase prejudica o desempenho dos frangos de corte e não afeta o rendimento de carcaças e cortes.

ABSTRACT: This study evaluated the effect of including different doses of phytase in broiler diets with different levels of phytate and reduced levels of calcium (Ca) and available phosphorus (aP), on broilers performance, digestibility (CAID), and bone characteristics. One thousand four hundred and four Cobb®500 broilers were used, distributed in a complete randomized design, and a 2x3 factorial arrangement, with two phytate levels (4.25 kg/ton - MP and 6.0 kg/ton - HP) and three phytase levels (0, 750, and 1500 FTU/kg) totalizing six treatments with nine replicates each. The animals that received phytase in their diet showed higher average feed intake and weight gain, and higher bone weight, % mineral residue, % Ca, and % P, when compared to the treatment without phytase (P < 0.01). Animals that received a diet containing HP with the inclusion of 1500FTU/kg phytase had the best CAID of nutrients (P < 0.0001). Regarding phytate, animals that received the MP diet showed a higher CAID of dry matter, and higher %P in the tibia when compared to animals that received the HP diet. The addition of phytase to diets with reduced Ca and aP levels can improve the CAIDs and bone characteristics in the presence of high phytate levels. However, reducing Ca and aP levels in the diet without adding phytase impairs the performance of broilers and has no effect on their carcass and cuts yield.

ABSTRACT The objective of this study was to evaluate the effect of pre-farrowing lipid supplementation for three days on performance parameters of sows and piglets and the survival rate of litters. Four hundred hyperprolific sows were randomly distributed in blocks according to their body condition score, weight, and parity order. Three levels of soybean oil were added on top at the time of feed supply and compared to the control treatment. The levels were: 250 mL, 500 mL, and 1,000 mL, in addition to the control that contained only the crude fat present in the feed (5.04%). Sows were weighed and evaluated for their body condition score at the beginning and end of the lactation period, and their piglets were weighed at birth, after 24 h, and at weaning to determine colostrum yield of the sow and daily weight gain of piglets during the lactation period. Survival rate of litters was also evaluated. Weight loss of gilts decreased linearly as the level of supplemented oil increased. The other parameters evaluated were not affected by treatments, suggesting that the supplemented soybean oil was used for growth rather than milk production of gilts. Additionally, it had no effect on the performance of multiparous females. Under the experimental conditions of this study, soybean oil supplementation for gilts in the first three days before farrowing decrease their weight loss but does not change their body condition score, colostrum yield, and performance and survival of their litters.

Resumo: O objetivo deste trabalho foi avaliar o efeito de diferentes tamanhos de partícula de farelo de soja, em dietas fareladas e peletizadas, no desempenho de frangos de corte. Foram avaliados 1.440 pintos de corte machos da linhagem Cobb500, com 1 a 35 dias de idade. O delineamento experimental foi inteiramente casualizado, em arranjo fatorial 2x4, com duas formas físicas da dieta e quatro granulometrias de farelo de soja (625, 775, 1.053 e 1.406 μm), tendo totalizado oito tratamentos, com nove repetições com 20 aves cada uma. Foram avaliados consumo de ração, ganho de peso e conversão alimentar. Houve interação significativa entre as formas físicas das dietas e o tamanho das partículas do farelo de soja. De 1 a 21 dias de idade, os menores valores de consumo de ração e ganho de peso foram obtidos com a dieta farelada contendo partículas do farelo de soja de 1.406 μm. Já de 1 a 35 dias de idade, o maior ganho de peso é alcançado quando os frangos são alimentados com dietas peletizadas com tamanho de particula do farelo de soja de 1.406 μm.

Abstract: The objective of this work was to evaluate the effect of different soybean meal particle sizes in pelleted or mash diets on broiler performance. A total of 1,440 male Cobb500 broilers, with 1 to 35 days of age, were evaluated. The experimental design was completely randomized, in a 2x4 factorial arrangement, consisting of two feed physical forms and four soybean meal particle sizes (625, 775, 1,053, and 1,406 μm), totaling eight treatments, with nine replicates of 20 birds each. Feed intake, weight gain, and feed conversion ratio were evaluated. There was a significant interaction between diet physical form and soybean meal particle size. From 1 to 21 days of age, the lowest feed intake and weight gain values were obtained with the mash diet containing 1,406 μm soybean meal particle size. From 1 to 35 days of age, the greatest weight gain is achieved when broilers are fed the pelleted diet with 1,406 μm soybean meal particle size.

ABSTRACT The objective of this study was to evaluate increasing levels of dried apple pomace on cat diets and its effects on the apparent total tract digestibility (ATTD) of nutrients and diet metabolizable energy (ME) and palatability. Fecal characteristics of cats were also evaluated. Four experimental diets were produced to contain 0, 30, 60, and 90 g kg−1 of dried apple pomace. Two experiments were carried out. In experiment 1, the diets were offered to twelve adult cats distributed in a completely randomized block design (n = 6). Two evaluation periods (blocks) of 11 days were used to analyze diet digestibility and fecal characteristics. In experiment 2, the palatability of diets containing 0 (control) vs. 90 g kg−1 of dried apple pomace was compared using 20 adult cats on two consecutive days (n = 40). Increasing dietary dried apple pomace levels (0-90 g kg−1) linearly reduced the ATTD of crude protein (834.0-798.0 g kg−1 of dry matter) and ME (4290.1-4161.0 kcal). There was a quadratic effect of the increasing dried apple pomace levels on the ATTD of the other nutrients, as well as on fecal dry matter (fDM) content and output. The dietary inclusion of 90 g kg−1 of dried apple pomace promoted a greater intake ratio (0.61) in relation to the control diet. The inclusion of up to 90 g kg−1 of dried apple pomace reduces diet digestibility, ME, and fDM of cats. However, it improves diet palatability. These results indicate that the dried apple pomace is a palatable fibrous component and its inclusion can be used to reduce the energy content of cat foods.

ABSTRACT This study aimed to evaluate the effects of including 200 g kg −1 dried distillers grains with solubles (DDGS) to xylanase- and protease-supplemented diets for dogs on kibble properties, digestibility, fecal characteristics, and palatability. Experimental diets consisted of: 0 g kg −1 DDGS without enzymes (0WE), 0 g kg −1 DDGS with xylanase and protease (0XP), 200 g kg −1 DDGS without enzymes (200WE), 200 g kg −1 DDGS with xylanase (200X), 200 g kg −1 DDGS with protease (200P), and 200 g kg −1 DDGS with xylanase and protease (200XP). Kibbles were evaluated for density, extruded size, expansion index, hardness, and uniformity. Six beagle dogs were distributed in a 6×6 Latin square design for analysis of digestibility and fecal characteristics. A palatability assay was also conducted in 16 beagle dogs, comparing the following treatment groups: 0WE vs. 200WE and 0XP vs. 200XP. The results showed that DDGS inclusion had no influence on kibble physical properties and reduced digestibility of dry matter (DM), ether extract after acid hydrolysis, gross energy, and organic matter, regardless of enzyme addition. Moreover, dietary addition of DDGS reduced fecal pH and increased total short-chain fatty acid, acetate, and propionate productions. Fecal odor was increased in dogs fed diets containing DDGS. Regarding palatability, animals preferred diets supplemented with enzymes and without DDGS, and no difference was observed when comparing 0WE and 200WE diets. No changes in the physical properties of kibbles were caused by DDGS inclusion; therefore, it can be used in diet formulation without interfering with the industrial process. Increased production of SCFA and a possible modulation of digestive tract microbiota promoted by DDGS addition may benefit animals. However, at the tested levels, enzymes had no positive effects on diet digestibility. Despite reducing digestibility, DDGS can still be included without enzyme supplementation in low-cost diets for dogs, as nutrient digestibility of the diet remains within acceptable limits for some pet food categories.

ABSTRACT The objective of this study was to evaluate the alterations in blood biochemical profiles and body condition of dogs after intake of the diet without soybean hull (0%SH) and with soybean hull (16%SH) replacing corn. Twelve Beagle dogs with ideal body condition score (BCS) (average: 5) were distributed in a completely randomized design (six animals per treatment) and received the daily amount of food according to the energy needs for maintenance (g/kg weight0.75). The animals were evaluated on days 0 and 28 in relation to the blood biochemical profiles and body measurements, such as: total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), very-low density lipoprotein (VLDL), triglyceride (TAG), glucose, body weight (BW), body fat percentage (%BF), nape, rib, tail base (TB), chest, and abdomen with plicometer, and BCS (scale of 1, thin and 9, obese), canine body mass index (CBMI), and thickness of the adipose tissue of the seventh lumbar vertebra (L7) with ultrasonography. The data were analyzed by Student's t test. The variation (final - initial, mg/dL) of cholesterol (16.33 vs. 15.55), HDL (17.56 vs. 10.05), LDL (22.78 vs. 14.57), VLDL (-4.01 vs. -1.92), TAG (-20.11 vs. -11.66), and glucose (-16.77 vs. -20.31) of dogs fed 0%SH and 16%SH, respectively, showed no difference. The body measurement variation (cm) of TB (1.00 vs. -0.60) obtained a significant difference. The addition of soybean hull in the diet does not alter the blood biochemical profiles; however, it does decrease the deposition of lipids in subcutaneous tissue.

RESUMO: O objetivo do presente estudo foi avaliar a digestibilidade e os efeitos imunomoduladores de dietas suplementadas com luteína em cães. Dezesseis cães adultos foram distribuídos em dois grupos (controle e teste), em delineamento inteiramente casualizado. Os cães foram alimentados durante 120 dias com dietas iso-nutritivas, diferindo apenasna inclusão de 45g de luteína/kg na dieta do grupo teste. As amostras de sangue foram colhidas no início e no final do período experimental para avaliar o total de linfócitos, o índice de proliferação de linfócitos e a contagem de linfócitos CD4 + e CD8 +. Para avaliar a digestibilidade aparente da dieta, os cães foram alojados em gaiolas metabólicas por dez dias (cinco dias de adaptação e cinco para coleta total de fezes). Os coeficientes de digestibilidade aparente não foram diferentes entre cães do grupo controle e os alimentados com luteína. A suplementação dietética com luteína não influenciou a contagem de linfócitos totais ou o índice de proliferação de linfócitos, mas resultou em número de linfócitos CD4 + e CD8 + mais elevadas. A suplementação de luteína não afeta a digestibilidade da dieta ou o índice de proliferação de linfócitos em cães. No entanto, aumenta as concentrações dos subtipos CD4 + e CD8 + de linfócitos T.

ABSTRACT: The objective of the present study was to evaluate the digestibility and the immunomodulatory effects of diets supplemented with lutein in dogs. Sixteen adult dogs were distributed in two groups (control and test) in a completely randomized design. Dogs were fed for 120 days with iso-nutritive diets, which only difference was the inclusion of 45g lutein/kg in the diet fed to the test group. Blood samples were collected in the beginning and at the end of the experimental period to evaluate total lymphocyte, lymphocyte proliferation index, and CD4+ and CD8+ lymphocyte counts. In order to evaluate apparent diet digestibility, dogs were housed in metabolic cages for ten days (five days of adaptation and five for faeces total collection). Coefficients of total tract apparent digestibility were not different between dogs in the control and the lutein-fed groups. Lutein dietary supplementation did not influence total lymphocyte or lymphocyte proliferation index, but resulted in higher CD4+ and CD8+ lymphocyte numbers. Lutein supplementation did not affect diet digestibility or lymphocyte proliferation index in dogs. However, it increases the concentrations of CD4+ and CD8+ T-lymphocyte subtypes.

A glicerina é um coproduto originado da produção de biodiesel, que apresenta possibilidade de uso como fonte energética na nutrição animal. Objetivou-se avaliar os coeficientes de digestibilidade aparente (CDA) e a energia metabolizável (EM) de dietas contendo glicerina, bem como a EM da glicerina em cães. Foram avaliadas quatro dietas contendo crescentes níveis de glicerina: 0%, 3%, 6% e 9%. As dietas foram fornecidas a oito cães adultos, os quais foram distribuídos em delineamento Quadrado Latino duplo (4x4). A adição de glicerina aumentou os CDA da matéria seca, energia bruta e a EM, sem afetar os CDA da proteína bruta e dos extrativos não nitrogenados da dieta. Entretanto, resultou em redução no CDA do extrato etéreo da dieta. Embora a adição de glicerina tenha reduzido o teor de matéria seca fecal, não houve efeito sobre o escore das fezes. Dentro dos níveis avaliados, a glicerina pode ser utilizada na dieta como fonte energética altamente disponível para cães.

Glycerin is a by-product originated from biodiesel production and it is an energetic ingredient of increasing possibility of use in diets of different species. This study aimed to evaluate the digestibility in dogs fed diets containing increasing levels of glycerol (0%, 3%, 6% and 9%). Diets were fed to eight adult dogs, which were distributed in Latin square design (4x4). The glycerol addition in the diet increased the digestibility of dry matter, gross energy and metabolizable energy, without affecting the digestibility of crude protein and nitrogen free extract. However, resulted in lower digestibility of ether extract. Although the addition of glycerin has reduced the amount of fecal dry matter, had no effect on fecal score. Within the levels evaluated, the glycerin can be used as dietary energy source highly available for dogs.

Using sorghum silage, the effect of roughage/concentrate ratios was evaluated on nutrient intake, digestibility, ruminal parameters and methane production by beef cattle. Three treatments (0, 30 and 60% of concentrate in DM of the diet) were distributed in three Latin squares, with nine animals and three periods. Dry matter intake increased as the grain concentration in diet increased; pH showed opposite behavior. Methane emissions were lower for animals fed the diet exclusively with sorghum silage as compared with those fed 30% of concentrate, but was similar to that of animals receiving 60% of concentrate. Losses of ingested gross energy as methane were reduced by 33% when grain concentration was increased in the diet. Concentrations of propionic and butyric acids were greater in diets with grain concentrate; acetic acid concentration was not affected. Concentrate in diet increases available energy for the metabolism, measured by lower losses of ingested gross energy as ruminal methane.

Objetivou-se avaliar diferentes metodologias de determinação da digestibilidade em cães, alimentados com duas dietas contendo fontes proteicas animal (farinha de vísceras de aves - FVA) e vegetal (farelo de soja - FS). As metodologias avaliadas foram: colheita total de fezes (CTF) e os indicadores cinza insolúvel em ácido (CIA), fibra em detergente ácido (FDA) e fibra bruta (FB). Foram utilizados 8 cães adultos, em delineamento Cross over, em parcela subdividida no tempo (parcela: fontes proteicas; e subparcela: metodologias de digestibilidade). O período experimental foi constituído por cinco dias de adaptação, com cinco dias de colheita total de fezes. A dieta contendo FS apresentou maior CDA da PB, enquanto a dieta contendo FVA apresentou maior CDA dos demais nutrientes e energia metabolizável (EM). Os CDA e EM determinados pela CTF e pelos indicadores não diferiram entre si, podendo ser determinados pelos indicadores FB, FDA e CIA, independentemente da fonte proteica da dieta.

The objective was to evaluate different methods of measuring digestibility in dogs fed two diets containing animal (poultry by products - PBP) and vegetable (soybean meal - SBM) protein sources. The methods evaluated were: total fecal collection (TFC) and indicators: acid insoluble ash (AIA), acid detergent fiber (ADF) and crude fiber (CF). Eight dogs were distributed in Cross Over in split plots (plot: sources of protein; subplot: methods for digestibility), fed by five days of adaptation and five days of total fecal collection. The diet containing SBM had a higher ADC of CP, while the diet containing POM showed higher ADC of all nutrients and metabolizable energy (ME). The ADC and ME determined by the TFC and the indicators did not differ. Thus, the ADC of diets in dogs can be determined by TFC and CF, ADF and AIA indicators, regardless of source of dietary protein.

The objective of the present study was to compare the apparent digestibility coefficients of a commercial dog food, fecal consistency and behavior of dogs housed in kennels and metabolic cages. Six adult Beagle dogs were distributed in cross-over experimental design, with six replicates per treatment. Dogs were housed in two environments: metabolic cages and in masonry kennels with solarium. Dogs were fed for a five-day adaptation period, and the five following days were used for total feces collection. Dogs behavior was recorded during a 48-h period, with 10-min intervals. Apparent digestibility coefficients were not different between treatments. However, dogs housed in metabolic cages produced lower weight and more consistent feces as compared with dogs housed in kennels. Dogs spent most of the time sleeping in both housing systems; however, dogs housed in the metabolic cages slept more than those in kennels. Stress-related behaviors (barking, whimpering, stereotypies, etc) were observed for no longer than 15 minutes per day, and were not different between dogs in kennels or in cages. There is no difference in food digestibility evaluated in dogs housed in metabolic cages or kennels; however, dogs kept in metabolic cages eliminate drier feces and spend more time inactive than those kept in kennels.

O experimento foi conduzido com o objetivo de avaliar o efeito da inclusão de ácido linoléico conjugado (CLA) em dietas de suínos dos 65kg de peso vivo até a fase de abate (100kg) sobre desempenho zootécnico, rendimento de corte e características de carcaça. Foram utilizados 200 suínos provenientes do cruzamento industrial JSR x PIC, em igual proporção de sexo. Os tratamentos foram compostos por dietas com (+CLA) e sem (-CLA) adição de CLA. O delineamento experimental utilizado foi completamente casualizado, sendo as características de carcaça avaliadas em esquema fatorial 2x2 (dieta x sexo). Os animais que consumiram CLA apresentaram melhor ganho de peso diário, redução da espessura de toucinho e maior rendimento de carne magra. A retenção de líquidos da carne não apresentou diferença em relação à dieta. Conclui-se, com base nos resultados, que é benéfica a inclusão de CLA na alimentação de suínos em terminação.

The proposal of this study was to evaluate the effect of conjugated linoleic acid (CLA) supplementation on swine diets, reared from 65kg body weight up to slaughter (100kg body weight) on animal performance, cut yields and carcass traits. Two hundred crossbred pigs (JSR x PIC) were used, half barrows and half gilts. The treatments were diets with (+CLA) and without (-CLA) supplementation of CLA. A completely randomly experimental design was used, and for the carcass traits and cut yield it was a 2x2 factorial design (diet and sex). Animals that consumed CLA presented a better average daily gain, decreased backfat thickness and a higher lean meat yield. Meat liquid retention capacity was not affected by diets. Based in these results it is beneficial the inclusion of CLA on finishing pigs feed.

A soja é um grão rico em proteínas e lipídeos, a partir do qual se obtém diversos derivados proteicos de alto valor nutricional. Em virtude disso, realizou-se este estudo com o objetivo de analisar a composição bromatológica de derivados proteicos de soja, bem como as características físico-químicas dos extrusados formados a partir destes. Foram formuladas seis dietas para cães, uma referência e cinco contendo 30% de derivados de soja (farinha desengordurada - FDS, micronizada, farelo, grão integral e grão tostado), as quais foram extrusadas. Os derivados de soja e as dietas foram submetidos a análises bromatológicas e de qualidade do processamento. A FDS e o farelo de soja apresentaram os maiores teores de proteína bruta, enquanto os grãos de soja integral e tostado e a soja micronizada apresentaram os maiores teores de extrato etéreo em hidrólise ácida e energia bruta. A soja grão integral apresentou a maior atividade ureásica e inibitória de tripsina, mesmo após a extrusão da dieta. Os extrusados contendo as sojas grão e micronizada apresentaram as maiores densidades e as menores durezas, índice de absorção de água e grau de gelatinização do amido. Derivados proteicos de soja apresentam alto valor nutricional, entretanto, devem ser termicamente processados antes da extrusão para completa inativação do inibidor de tripsina. Além do mais, derivados contendo alto teor de lipídeos, como soja grão e micronizada, quando adicionados em 30% da fórmula, comprometem a qualidade do extrusado.

Soy is a grain rich in protein and lipids, from which its obtained different protein products of high nutritional value. This study aimed to analyze the chemical composition of different soy-protein products, as well as the characteristics of the extruded produced. Six diets were formulated, a reference and five with 30% soy product (defatted soy flour - DSF, micronized, soybean meal, crude grain or toasted grain), which were extruded. Soy products and diets were submitted to chemical analyses and process quality. The DSF and soybean meal presented the highest crude protein content, while the toasted and crude soybeans and micronized soy presented the highest acid hydrolyses ether extract and crude energy content. The crude soybean presented the highest ureatic activity and trypsin inhibitor activity, even after the diet extrusion. The soy beans and micronized soy extruded presented the highest density and the lowest hardness, water absorption index and starch gelatinization degree. Soy-protein products present high nutritional value, however they should be heated before extrusion to complete inhibition of trypsin inhibitor. Besides, soy products with high fat content, such as soybean and micronized soybean, when added to 30% reduced the extruded quality.

Em virtude da capacidade moduladora dos probióticos sobre a microbiota intestinal a favor da saúde do hospedeiro, objetivou-se, com este estudo, avaliar a digestibilidade e as características das fezes de cães suplementados com Bacillus subtilis (C-3102) na dieta. Foram utilizados 12 cães adultos da raça Beagle, os quais foram distribuídos inteiramente ao acaso, em dois tratamentos: dieta controle e dieta com adição de 0,01% de Bacillus subtilis (C-3102). Os animais passaram por 25 dias de adaptação às dietas e por cinco dias para colheita total de fezes. As características das fezes foram avaliadas por meio da matéria seca, do escore (1: fezes moles, malformadas a 5: fezes secas e duras), do pH, da amônia e da produção de fezes. Não houve diferença na digestibilidade; entretanto, os cães suplementados com probiótico apresentaram fezes mais secas (39,1% vs. 36,5% de matéria seca), com maior escore (3,4 vs. 3,0) e menor teor de amônia (0,45% vs. 0,56%), quando comparados com os alimentados com a dieta controle. A suplementação com Bacillus subtilis (C-3102) melhora a consistência e diminui o odor das fezes dos cães.

Considering the benefice demonstrated by the modulating action of probiotics on the host intestinal microbiota, this study aimed to evaluate diet digestibility and fecal characteristics of dogs fed with diets supplemented with Bacillus subtilis (C-3102). Twelve young Beagle dogs were distributed in a completely randomized experimental design consisting of two treatments: diet with no addition or with the addition of 0.01% Bacillus subtilis (C-3102). Dogs passed through 25 days of adaptation to the diets, and five days of total feces collection. The following fecal characteristics were evaluated: pH, fecal score (1 - watery feces; 5: dry and hard feces), and ammonia content. Diet mean digestibility was compared by the Tukey test, and fecal characteristics by the Tukey-Kramer test. Diet digestibility was not different between treatments, but dogs supplemented with the tested probiotic presented dryer feces (39.1% vs. 36.5% dry matter), higher fecal score (3.4 vs. 3.0) and lower fecal ammonia content (0.45% vs. 0.56%), than dogs fed with the control diet. The dietary supplementation with Bacillus subtilis (C-3102) improves fecal texture and odor in dogs.

Gases gerados durante o processo de fermantação ruminal, metano em particular, representam não só uma perda parcial de energia da alimentação como também são apontados como importantes fatores do efeito-estufa. Quantificaram-se as taxas de emissão de metano (CH4) ruminal por vacas em lactação, vacas secas e novilhas com idade média de 24 meses, em pastejo sob condições tropicais do sudeste brasileiro, utilizando a técnica do gás traçador hexafluoreto de enxôfre (SF6). Foram utilizados quatro animais para cada categoria, distribuídos em quatro blocos. As medições foram realizadas em fevereiro e junho de 2002, com animais da raça Holandesa e Mestiça Leiteira Holandês ¾ x Gir ¼ - Mestiças, mantidos em pastagem de capim-Tanzânia (Panicum maximum Jacq. cv. Tanzania) e capim-braquiária (Brachiaria decumbens cv. Basilisk) adubadas, e também novilhas de ambas as raças em pastagens de capim-brachiaria sem adubação, simulando as condições de produção extensiva. As concentrações de CH4 e SF6 foram determinadas por cromatografia gasosa. Foram encontradas diferenças na emissão de metano (p < 0,05) entre os grupos genéticos. Animais da raça holandesa produziram mais metano (299,3 g dia-1) que as mestiças (264,2 g dia-1). Vacas secas e novilhas produzem menos metano (g dia-1) que vacas em lactação. A média de emissão de metano (g dia-1) pelas vacas secas e novilhas foi de 268,8 e 222,6 g respectivamente e as vacas em lactação 353,8 g. Os animais da raça holandesa, com maior potencial de produção de leite, perderam menos CH4 (p < 0,05) por unidade de matéria seca ingerida (19,1 g kg-1) que as mestiças (22,0 g kg-1). A produção de metano pelas novilhas mantidas em pastagens adubadas (sistema intensivo) foi de 222,6 g dia-1, maior (p < 0,05) que os animais desta categoria em pastagens não adubadas (179,2 g dia-1). A produção de metano variou em função da categoria de animal e pelo sistema de produção imposto aos animais.

Ruminal gases, particularly methane, generated during the fermentative process in rumen, represent a partial loss of feed energy and are also pointed to as an important factors in greenhouse effect. This study aimed at quantifying methane (CH4) emission rates from lactating and dry cows and heifers, 24 month-old in average, on pasture under Southeast Brazil tropical conditions, using the tracer gas technique, sulphur hexafluoride (SF6), four animals per category, distributed in four blocks. Measurements were performed in February and June, 2002, with Holstein and Brazilian Dairy Crossbred (Holstein ¾ x Gir (Zebu) ¼), maintained on fertilized Tanzania-grass (Panicum maximum Jacq. cv. Tanzania) and fertilized Brachiaria-grass (Brachiaria decumbens cv. Basilisk) pastures. Heifers of both breeds were maintained on unfertilized Brachiaria-grass to simulate conditions of extensive cattle farming systems. CH4 and SF6 levels were measured with gas chromatography. Differences in CH4 emissions were measured (p < 0.05) for genetical groups. Holstein produced more methane (299.3 g day-1) than the Crossbred (264.2 g day-1). Lactating cows produced more methane (353.8 g day-1) than dry cows (268.8 g day-1) and heifers (222.6 g day-1). Holstein, with greater milk production potential, produced less CH4 (p < 0.05) per unit of dry matter intake (19.1 g kg-1) than the Crossbred (22.0 g kg-1). Methane emission by heifers grazing fertilized pasture (intensive system) was 222.6 g day-1, greater (p < 0.05) than that of heifers on unfertilized pasture (179.2 g day-1). Methane emission varied as function of animal category and management intensity of production system.