Experiments were conducted to investigate: 1) production of trans-18:1 and cis/trans-18:2 isomers due to input of forage and corn grain in continuous culture fermenters, 2) concentrations of trans-18:1 and cis/trans-18:2 isomers in blood and milk fat of grazing cows fed a grain supplement containing solvent- or mechanically-extracted soybean meal, 3) plasma and milk fatty acid profiles of lactating cows in response to a conjugated linoleic acid (CLA) mixture infused into the rumen, and 4) effects of cis9,trans11-18:2 (9/11CLA) or trans10,cis12-18:2 (10/12CLA) on de novo synthesis and desaturation of milk fatty acids in lactating cows fed unsaturated oils. In the first study, rumen fermenters were fed (50 g DM/d) orchardgrass or red clover with 0, 8, or 16 g/d corn replacing equal portions of forage DM. Outflow of trans11,cis15-18:2 (11/15LA) in effluents was greater when DM input was clover or grass only. With each increment of corn, output of 9/11CLA increased until it was 205% greater compared with forage alone. Trans11-18:1 (TVA), an intermediate in 18:2n6 (LA) and 18:3n3 (LN) hydrogenation, output increased by 28% with corn addition. Outputs of trans10-18:1 and 10/12CLA nearly doubled as corn increment increased. In the second experiment, Holstein cows grazing mixed clover-grass pastures were fed a grain supplement (6.7 kg/d) containing 1.7 kg solvent-extracted soybean meal (SES, 15 mg LA/g of DM), 1.9 kg mechanically-extracted soybean meal (MES, 24 mg LA/g of DM), or 1.9 kg MES plus 30 g of liquid methionine hydroxy analog (MESM). Cows fed MES or MESM had greater concentrations of LA, TVA, 9/11CLA, and 11/15LA in blood compared with cows fed SES. Daily yields of 18:0 (SA), LA, LN, TVA, and 9/11CLA in milk fat also were greater for cows fed MES or MESM compared with SES. In experiment 3, four Holstein cows were used in a 4 x 4 Latin square to determine plasma and milk fatty acid profiles during infusion of a CLA mixture at 0, 45, 90, or 180 g/d for 48 h into the rumen. Relative to the control, infusion of 180 g CLA/d decreased milk fat percentage and yield. Lower milk fat yield resulted from depressed concentrations of saturated 6:0 to 16:0 medium-chain fatty acids (MCFA). Concentrations of TVA, trans10-18:1, and 10/12CLA in blood plasma, and yields in milk fat increased in response to each dose of CLA. Stearic acid yield also increased as dose of CLA increased. Yield of cis9-18:1 (OA) in milk fat, however, was lower at 180 g CLA/d. In experiment 4, four cows were fed high-oleic (HO) or high-linoleic (HL) (2.5% of DM) oil for 11 d prior to abomasal infusion (15 g/d) of 9/11CLA or 10/12CLA for 48 h (2 x 2 factorial). Milk fat percentage and yield decreased 25% due to infusion of 10/12CLA compared with 9/11CLA, regardless of diet. Lower fat yields resulted from lower MCFA concentrations and yields. Regardless of diet, concentration (but not yield) of SA increased 40% when 10/12CLA was infused compared with 9/11CLA. Concentrations and yields of OA, 9/11CLA, and 20:4n6 also were reduced by infusing 10/12CLA compared with 9/11CLA regardless of diet. Thus, in addition to inhibiting de novo fatty acid synthesis, 10/12CLA appeared to inhibit desaturation via delta-6 and delta-9 desaturases. Significant implications from the above studies include: 1) 11/15LA and TVA are the primary intermediates flowing out of the rumen during hydrogenation of pasture lipids, 2) replacing forage DM with starch, OA, and LA increases synthesis of trans10-18:1 and 10/12CLA in the rumen, 3) desaturation of TVA produced in the rumen provides an alternate source for 9/11CLA in milk fat, and 4) 10/12CLA decreases de novo synthesis and desaturation of milk fatty acids. / Ph. D.

Biosynthesis of milk conjugated linoleic acid (CLA), a component of milk fat with demonstrated health benefits, requires a dietary source of PUFA. Even with PUFA supplementation, milk CLA is highly variable. Therefore, this study was aimed at identifying factors responsible for the variations in rumen CLA precursors and milk CLA. Study 1 evaluated the efficiency of CLA production by grazing cows compared to those fed grass silage or fresh grass. Grazing cows were more efficient than those fed grass silage or fresh grass in milk CLA production. About 75% of the variability in milk CLA was related to the differences in PUFA (l8:2n-6 + 18:3n-3) intake and the remainder was related to factors regulating the extent of PUFA biohydrogenation in the rumen. This study demonstrated that PUFA intake is important but it is not the only factor responsible for the observed variation in milk CLA production. Study 2 evaluated the effect of diets differing in rate of starch degradation on rumen PUFA biohydrogenation and milk CLA. Concentrations of ruminal t11-18:1 and milk CLA were greater for barley-based diets than corn-based diets and were not different between rolling and grinding, indicating that factors inherent in the source of starch were responsible for the observed differences and these factors could not be modified by rolling or grinding the grain. Study 3 examined the effect of stage of lactation on persistency of milk t10-18:1, t11-18:1 and CLA for control and test (supplemented with PUFA and monensin) diets from calving to 270 days in milk. Milk concentrations of t11-18:1 and RA remained similar across the lactation length and were greater for the test diet compared to the control. Changes in milk t10-18:1 concentration during lactation appeared to reflect an effect of the degree of rumen fermentation on PUFA biohydrogenating bacteria. Although PUFA intake is important for milk CLA production, only those diets that give rise to increased ruminal t11-18:1 result in greater milk CLA. Concentrations of rumen t11-18:1 is influenced by the amount of PUFA consumed, degree of shift to t10-18:1 and the extent of PUFA biohydrogenation in the rumen. / Animal Science

No description available.

Nas pesquisas com bovinos de corte, além do bom desempenho animal e da viabilidade econômica, busca-se agregar características qualitativas à carne produzida. O fornecimento de milho alto óleo a bovinos de corte em terminação aumenta o ganho de peso e a qualidade de carcaça, quando comparado ao milho comum. Buscou-se consolidar as informações quanto aos efeitos das dietas para novilhos Nelore em confinamento, sobre os parâmetros da produção animal, como ganho de peso, rendimento de carcaça, degradabilidade das dietas, efeitos sobre os protozoários ciliados e outras medidas ruminais, parâmetros físicos do Longissimus dorsi, composição centesimal da carcaça, composição do ganho e perfil de ácidos graxos nesse músculo. Foram utilizados 48 novilhos da raça Nelore, com peso vivo inicial médio de 435 kg, submetidos a um dos seis tratamentos, usando dois tipos de milho (comum e alto óleo) e três níveis de inclusão de milho no concentrado (25%, 40% e 55%). Os animais foram confinados por um período de 84 dias. Amostras do Longissimus dorsi foram coletadas para avaliação das características físicas da carne e análise do perfil de ácidos graxos na gordura intramuscular. Os tratamentos não influenciaram o ganho de peso, o consumo de alimentos, a conversão alimentar ou os parâmetros da carcaça. A qualidade física da carne também não foi influenciada pelos tratamentos. Para as dietas contendo milho alto óleo, houve alteração na população de protozoários no rúmen e na degradação da FDN. Dietas com milho alto óleo favoreceram o aumento no total dos ácidos graxos intermediários da biohidrogenação na gordura intramuscular. Houve diferenças significativas no ácido rumênico (CLA - C18:2_cis9_trans11), passando de 0,43% para 0,49%, representando um aumento médio de 12,7%, devido ao uso de dietas contendo milho alto óleo. / Beef cattle researchers, over than animal performance and economics are looking for nutritional characteristics of the products from ruminants. Inclusion of high oil corn (HOC) on diets increases weight gain and carcass quality compared to common corn grain. This study looks for data from animal performance on diets using high oil corn, evaluating live weight gain, carcass composition, diets digestibility, dry matter degradability, effects on ciliated protozoa number and quality, muscle quality characteristics, meat composition and fatty acids profile on intramuscular fat. Where used 48 Nellore steers, with initial average live weight of 435 kg in six treatments, using two corn grain varieties (common and high oil corn) and three levels of corn grain in concentrate diets (25%, 40% and 55%). Animals were in feedlot pens for 84 days, after an adaptation period to diets and installations. The Longissimus dorsi was used for evaluating meat characteristics and fatty acids profile on intramuscular fat. There was no effect of diets on daily gain, intake, conversion, or carcass parameters. Meat quality was not also affected by treatments. Diets with high oil corn altered protozoa population and ruminal degradation of NDF. The total biohidrogenated fatty acids in intramuscular fat were increased by treatment with high oil corn and also rumenic acid. Rumenic acid was the major conjugated linoleic acid (CLA) detected in this tissue, with concentrations increasing from 0,43% to 0,49%, representing an average increase of 12,7% caused for HOC diets.

Nas pesquisas com bovinos de corte, além do bom desempenho animal e da viabilidade econômica, busca-se agregar características qualitativas à carne produzida. O fornecimento de milho alto óleo a bovinos de corte em terminação aumenta o ganho de peso e a qualidade de carcaça, quando comparado ao milho comum. Buscou-se consolidar as informações quanto aos efeitos das dietas para novilhos Nelore em confinamento, sobre os parâmetros da produção animal, como ganho de peso, rendimento de carcaça, degradabilidade das dietas, efeitos sobre os protozoários ciliados e outras medidas ruminais, parâmetros físicos do Longissimus dorsi, composição centesimal da carcaça, composição do ganho e perfil de ácidos graxos nesse músculo. Foram utilizados 48 novilhos da raça Nelore, com peso vivo inicial médio de 435 kg, submetidos a um dos seis tratamentos, usando dois tipos de milho (comum e alto óleo) e três níveis de inclusão de milho no concentrado (25%, 40% e 55%). Os animais foram confinados por um período de 84 dias. Amostras do Longissimus dorsi foram coletadas para avaliação das características físicas da carne e análise do perfil de ácidos graxos na gordura intramuscular. Os tratamentos não influenciaram o ganho de peso, o consumo de alimentos, a conversão alimentar ou os parâmetros da carcaça. A qualidade física da carne também não foi influenciada pelos tratamentos. Para as dietas contendo milho alto óleo, houve alteração na população de protozoários no rúmen e na degradação da FDN. Dietas com milho alto óleo favoreceram o aumento no total dos ácidos graxos intermediários da biohidrogenação na gordura intramuscular. Houve diferenças significativas no ácido rumênico (CLA - C18:2_cis9_trans11), passando de 0,43% para 0,49%, representando um aumento médio de 12,7%, devido ao uso de dietas contendo milho alto óleo. / Beef cattle researchers, over than animal performance and economics are looking for nutritional characteristics of the products from ruminants. Inclusion of high oil corn (HOC) on diets increases weight gain and carcass quality compared to common corn grain. This study looks for data from animal performance on diets using high oil corn, evaluating live weight gain, carcass composition, diets digestibility, dry matter degradability, effects on ciliated protozoa number and quality, muscle quality characteristics, meat composition and fatty acids profile on intramuscular fat. Where used 48 Nellore steers, with initial average live weight of 435 kg in six treatments, using two corn grain varieties (common and high oil corn) and three levels of corn grain in concentrate diets (25%, 40% and 55%). Animals were in feedlot pens for 84 days, after an adaptation period to diets and installations. The Longissimus dorsi was used for evaluating meat characteristics and fatty acids profile on intramuscular fat. There was no effect of diets on daily gain, intake, conversion, or carcass parameters. Meat quality was not also affected by treatments. Diets with high oil corn altered protozoa population and ruminal degradation of NDF. The total biohidrogenated fatty acids in intramuscular fat were increased by treatment with high oil corn and also rumenic acid. Rumenic acid was the major conjugated linoleic acid (CLA) detected in this tissue, with concentrations increasing from 0,43% to 0,49%, representing an average increase of 12,7% caused for HOC diets.