Ruminal fermentation and degradation, kinetic flow of the digesta and milk fatty acid composition of cows fed chopped elephantgrass supplemented with soybean oil Fermentação e degradação ruminal, cinética de fluxo da digesta e perfil de ácidos graxos do leite de vacas alimentadas com capimelefante picado suplementado com óleo de soja AbstractThe aim of this study was to evaluate the ruminal parameters of fermentation and degradation, kinetic flow of rumen digesta, and milk fatty acid composition of cows fed 52% chopped elephantgrass-based diets containing 0.0% (control), 1.5%, 3.0% and 4.5% soybean oil (SO) on a dry matter (DM) basis. Four rumen-cannulated Holstein x Gyr dairy cows with an average milk production of 15.6 ± 3.0 kg day -1 and 90 ± 25 days in milk were allocated in a 4 x 4 Latin square design. The results were analyzed by mixed models. Significant differences were declared at P≤0.05, and P-values from 0.05 < P ≤ 0.10 were considered as a trend. The inclusion of SO in the diet had no effect on the ruminal pH or total volatile fatty acid concentration, but there was a quadratic effect on the ruminal ammonia nitrogen content and a trend for a linear reduction (P=0.07) in the molar proportion of rumen acetate. Linear reductions were also observed in the DM and neutral detergent fiber (NDF) effective degradabilities of elephantgrass forage, but the fluid and particulate passage rates in the rumen and the DM and NDF intakes were unchanged by SO inclusion in the diet. Milk production, protein and lactose contents and yields were unaltered by dietary SO levels. There were linear reductions in the milk fat and total solids contents, but there was no effect of dietary treatments on their yields. The inclusion of soybean oil in the diet of Holstein x Gyr cows fed chopped elephantgrass improved the nutritional quality of milk fat as a result of increased contents of oleic, rumenic and vaccenic acids, which are beneficial to human health, and a concomitant reduction in hypercholesterolemic saturated fatty acids such as lauric, myristic and palmitic acids. ResumoO objetivo deste estudo foi avaliar os parâmetros de fermentação e degradação ruminal, a cinética de fluxo da digesta, e o perfil de ácidos graxos (AG) do leite de vacas alimentadas com 52% de capimelefante picado e inclusão de 0,0 (controle), 1,5, 3,0 e 4,5% de óleo de soja (OS) na matéria seca (MS) da dieta. Foram utilizadas quatro vacas Holandês x Gir com 90 ± 25 dias em lactação, produzindo 15,6 ± 3,0 kg dia -1 de leite, canuladas no rúmen, e alocadas em delineamento Quadrado Latino 4 x 4. Os resultados foram analisados por modelos mistos. Efeitos foram considerados significativos quando P <0,05, enquanto valores de P entre 0,05 e 0,10 foram considerados indicativos de tendência. A inclusão de OS na dieta não alterou o pH do rúmen, nem a concentração total de ácidos graxos voláteis, mas promoveu efeito quadrático sobre a concentração de N amoniacal, e tendência de redução linear (P=0,07) sobre a proporção molar de acetato. Foram observadas reduções...

RESUMOEste experimento teve como objetivo principal avaliar as alterações no perfil de ácidos graxos do leite decorrentes do fornecimento de diferentes níveis de óleo de girassol (OG) para vacas leiteiras alimentadas com dietas completas à base de capim-elefante. Doze vacas da raça Holandesa receberam quatro níveis de OG na dieta (0; 1,3; 2,5 e 3,7% da MS) em delineamento quadrado latino 4 x 4. Não houve efeito (P>0,05) dos níveis de OG sobre o consumo de MS, a produção de leite ou os teores de sólidos do leite. Por outro lado, o perfil de ácidos graxos (AG) do leite foi amplamante modificado com a inclusão de OG na dieta, e observou-se redução (P<0,0001) dos teores dos AG de cadeia curta e média, elevação dos teores de ácido oleico (P<0,0001), dos isômeros de ácido linoleico conjugado, em especial do ácido rumênico (P<0,0001) e da relação entre os ácidos graxos hipo e hipercolesterolêmicos (P<0,0001). Apesar da maior ingestão diária de ácido linoleico (P<0,01) com o aumento do nível de OG na dieta, sua concentração na gordura do leite não foi alterada. Isso indica extensiva bio-hidrogenação ruminal deste AG no rúmen, o que é compatível com o aumento (P<0,0001) da concentração de ácido esteárico e dos AG C18:1 trans, especialmente do vacênico, na gordura do leite. Em geral, os resultados observados no presente estudo indicam que a inclusão de até 3,7% de OG em dietas completas de vacas leiteiras à base de capim-elefante promove melhoria da qualidade nutricional da gordura do leite, sem comprometimento do desempenho produtivo dos animais.

The aim of this study was to evaluate the performance of cows fed with a total mixed ration composed of elephant grass and a concentrate containing 0.0% (control), 1.5%, 3.0% or 4.5% soybean oil on a dry matter basis. The effect of milking time (morning versus afternoon) on butter fatty acid composition was also evaluated. Twelve multiparous Holstein x Gyr cows with an average milk production of 18.0±4.6 kg day-1 and 90±25 days in milk were used in a triplicated 4 x 4 Latin square experimental design with 15-day periods. Data were analyzed using mixed models. There was no effect of soybean oil supplementation on dry matter or neutral detergent fiber intake (P > 0.05). The fat-corrected milk yield linearly decreased (P=0.0109) and the milk protein yield linearly increased (P=0.0023) in response to soybean oil supplementation. The butterfat trans-9 C18:1, cis-9 C18:1, trans-10 C18:1, trans-11 C18:1, cis-9, trans-11 CLA and trans-10, cis-12 CLA content linearly increased (P < 0.05), whereas the C12:0, C14:0 and C16:0 content linearly decreased (P < 0.001) as the level of soybean oil in the diet increased. The butter produced from afternoon milk had a lower content of C16:0 and a higher content of cis-9 C18:1 (P < 0.05). The supplementation of elephant grass-based-diets with soybean oil and, to a small extent, the selective segregation of milk obtained from afternoon milking sessions are strategies that can be used to improve the fatty acid composition of butterfat.

Recent studies have shown that dietary supplementation with sources rich in polyunsaturated fatty acids (PUFA) can improve reproductive perfor-mance of lactating dairy cows. However, no studies have reported the fatty acids composition of follicular fluid (FF) from dairy cows fed high-PUFA diets. This study aimed to evaluate the fatty acids composition of FF from dairy cows fed tropical forage-based diets containing different levels of soybean oil (SO). Four multiparous Holstein-Zebu cows in midlactation (90 ± 25 days in milk) were assigned to 1 of the following dietary treatments (on a dry matter basis): (1) T1 (control) = no SO; (2) T2 = diets containing 1.5% of SO; (3) T3 = diets containing 3.0% of SO; and (4) T4 = diets containing 4.5% of SO. Diets were composed of chopped elephant grass and a concentrate mixture and the forage concentrate ratio was 55 : 45 (dry matter basis). The experimental design was a 4 × 4 Latin square in which each period lasted 21 days. All cows received intravaginal progesterone-releasing devices and follicular waves were synchronized with 0.5 mg of gonadorelin. The FF from dominant follicles was collected by transvaginal ultrasound-guided aspiration on the last day of each period (Day 21) and centrifuged (10000 × g, 1 min) and the supernatant was frozen at -80°C until fatty acid analysis. Extraction and methylation of fatty acids in FF were performed according to the 1-step simplified method described by Masood A et al. (2005 J. Lipid Res. 46, 2299-2305). The fatty acid profile from FF was determined by gas chromatography as described by Cruz-Hernandez C et al. (2007 J. Dairy Sci. 90, 3786-3801). Treatment effects were determined by regression analysis using the REG procedure of SAS (SAS Institute, Cary, NC, USA) and declared significant at P < 0.05. Nearly 30 different fatty acids (70% of the total area) were identified in the FF samples. The most representative fatty acids (% total area) for the 4 dietary treatments (T1, T2, T3, and T4, respectively) were C18 : 2 cis - 9, cis - 12 (19.8, 20.3, 16.1, and 24.2), C18 : 0 (17.7, 16.6, 19.5, and 16.8), C16 : 0 (12.2, 10.7, 11.3, and 17.8), and C18 :1 cis - 9 (6.5, 7.3, 5.5, and 7.7). Inclusion of SO in the diet linearly reduced (P < 0.05) concentrations of C16 : 1 cis - 9 (0.8, 0.7, 0.4, and 0.5) and C20 : 3 (1.2, 1.1, 0.5, and 0.7), but linearly increased (P < 0.05) concentrations of C18 : 1 trans - 11 (0.4, 0.4, 0.6, and 1.4), C18 : 1 cis - 11 (0.4, 0.5, 0.4, and 0.9), and C18 : 1 cis - 12 (0.2, 0.5, 0.5, and 0.7) isomers in FF. The increase in the concentration of C18 : 1 trans - 11 in FF from cows fed higher levels of SO was not accompanied by an increase in the proportion of CLA cis - 9, trans - 11 (0.9, 1.0, 0.7, and 0.9 for T1, T2, T3, and T4, respectively). It suggests the absence or low activity of A9-desaturase enzyme in the follicular environment, unlike that observed in the mammary gland. In general, our results indicate that fatty acid composition of follicular fluid from lactating dairy cows is sensitive to changes in dietary supply of PUFA. Financial support: FAPEMIG (CVZ1815/06).

We aimed to evaluate the economic feasibility of adding increasing levels of sunflower oil (0.0, 15, 30, and 45 g/kg of dry matter) to elephant grass (Pennisetum purpureum, Schum) based diets of milkproducing Holstein cows. Data were obtained and analyzed for 12 primiparous Holstein cows that produced on average 16.5 ± 2.8 kg of milk/day, at 95 ± 25 days of lactation. Cows were distributed by milk production, order of lactation, and body weight in a 4 × 4 triple Latin square. Isoproteic diets were provided ad libitum in the form of a forage:concentrate ratio of 60:40, on a dry matter basis. Daily milk production was recorded and milk was analyzed for fat, protein, and fatty acids contents. An economic feasibility study was performed considering the price of the supplied ingredients and the daily intake of each diet. The economic benefit was derived by the determining the difference between income from the sale of milk and the cost of animal feed. The quality-based payment was estimated by averaging the systems used by eight dairy companies, based on fat and protein contents and milk volume. The sunflower oil-free diet provided the greatest economic benefit. Adding sunflower oil to elephant grassbased diets was not economically viable because of its associated costs. Key words: Dairy cattle. Economics. Nutrition. Milk quality. ResumoObjetivou-se avaliar a viabilidade econômica da produção de leite de vacas da raça Holandesa, pela inclusão de níveis crescentes de óleo de girassol (0,0; 15; 30 e 45 g/kg na matéria seca) em dietas à base de capim-elefante (Pennisetum purpureum, Schum). Os dados analisados foram obtidos de um experimento com 12 vacas primíparas da raça Holandesa, com 95 ± 25 dias em lactação, produção média de 16,5 ± 2,8 kg/dia de leite, distribuídas em um triplo quadrado latino 4 x 4, conforme a produção de leite, a ordem de lactação e o peso corporal. As dietas foram isoproteicas, fornecidas ad libitum na forma de mistura total (relação volumoso: concentrado de 60:40, base matéria seca). A produção diária de leite foi registrada e a composição analisada quanto à concentração de gordura, proteína e ácidos graxos. A viabilidade econômica foi realizada considerando o preço dos ingredientes fornecidos e o consumo diário da dieta de cada tratamento. O benefício econômico foi obtido pela diferença entre a receita, com a venda do leite, e o custo com alimentação dos animais. O pagamento por qualidade foi estimado pela média de sistemas utilizados por oito empresas do ramo de laticínios, com base na concentração de gordura, proteína e no volume de leite. A dieta sem inclusão de óleo de girassol foi a que proporcionou maior benefício econômico. A inclusão de óleo de girassol nas dietas baseadas em capim-elefante não foi viável economicamente, devido aos gastos com este ingrediente.