Effects of dietary supplementation of rumen-protected conjugated linoleic acid to grazing cows in early lactation

Abstract

Conjugated linoleic acids (CLA) are potent anticarcinogens in animal and in vitro models as well as inhibitors of fatty acid synthesis in mammary gland, liver, and adipose tissue. Our objective was to evaluate long-term CLA supplementation of lactating dairy cows in tropical pasture on milk production and composition and residual effects posttreatment. Thirty crossbred cows grazing stargrass (Cynodon nlemfuensis Vanderyst var. nlemfüensis) were blocked by parity and received 150 g/d of a dietary fat supplement of either Ca-salts of palm oil fatty acids (control) or a mixture of Ca-salts of CLA (CLA treatment). Supplements of fatty acids were mixed with 4 kg/d of concentrate. Grazing plus supplements were estimated to provide 115% of the estimated metabolizable protein requirements from 28 to 84 d in milk (treatment period). The CLA supplement provided 15 g/d of cis-9,trans-11 and 22g of cis-10,trans-12. Residual effects were evaluated from 85 to 112 d in milk (residual period) when cows were fed an 18% crude protein concentrate without added fat. The CLA treatment increased milk production but reduced milk fat concentration from 2.90 to 2.14% and fat production from 437 to 348 g/d. Milk protein concentration increased by 11.5% (2.79 to 3.11%) and production by 19% (422 to 504 g/d) in the cows fed CLA. The CLA treatment decreased milk energy concentration and increased milk volume, resulting in unchanged energy output. Milk production and protein concentration and production were also greater during the residual period for the CLA-treated cows. The CLA treatment reduced production of fatty acids (FA) of all chain lengths, but the larger effect was on short-chain FA, causing a shift toward a greater content of longer chain FA. The CLA treatment increased total milk CLA content by 30% and content of the trans-10,cis-12 CLA isomer by 88%. The CLA treatment tended to decrease the number of days open, suggesting a possible effect on reproduction. Under tropical grazing conditions, in a nutritionally challenging environment, CLA-treated cows decreased milk fat content and secreted the same amount of milk energy by increasing milk volume and milk protein production.

Fatty acid profile and composition of milk protein fraction in dairy cows fed long-chain unsaturated fatty acids during the transition period

“…Despite the reduction in milk fat content with the triggering of these physiological processes at the expense of higher concentrations of CLA trans-10, cis-12, some studies (Bernal-Santos et al, 2003;Selberg et al, 2004;Medeiros et al, 2010) have shown that this reduction has benefits on the negative energy balance (NEB) by decreasing the energy content excreted in milk, and this favors the increase in the amount of energy retained in the animal body, which in turn reduces the mobilization of body reserves. This is consistent with the data obtained in this study, because the group of cows on the CS diet presented less intense NEB in the transition period (40.32%) in relation to the SO diet, and about 20.0% lower in relation to the animals subjected to diet C, demonstrating the beneficial effect on energy partition (Table 4).…”

Produção e composição de leite de vacas mestiças suplementadas com diferentes níveis de concentrado mantidas em pastagem de capim Tanzânia irrigada

“…Os teores médios de lactose, em trabalhos conduzidos em pasto com suplementação, variaram de 4,51 a 5, 10 (SCHROEDER et al, 2002;MEDEIROS et al, 2010). Estes valores são superiores aos encontrados no presente estudo, onde não houve diferença (P>0,05) entre os níveis de concentrado.…”

Perfil de ácidos graxos na carne de novilhos superjovens da raça Devon, terminados sob diferentes sistemas de alimentação

“…Trabalhando com animais terminados em pastagens tropicais Padre et al (2006) observaram valor médio de CLA de 0,14%, inferiores ao encontrados no presente estudo. Medeiros et al (2010) justificam o menor conteúdo de CLA em animais alimentados com forrageira tropical perante os animais confinados pelos menores teores de ácido linolênico e maiores de palmítico (Tabela 2) que essas forrageiras apresentam. Esse perfil seria menos favorável a produção de CLA, fato que não foi observado no presente estudo.…”

“…Pelas supostas implicações positivas dos ácidos graxos ω-3 na saúde humana, a maior concentração, normalmente encontrada, seria uma vantagem na produção de animais a pasto. No entanto, a transferência dessa conclusão para os animais a pasto em países tropicais, em função da grande diferença de perfil de ácidos graxos entre forrageiras tropicais e temperadas, é prematura (MEDEIROS et al, 2010).…”