The fiber is an essential component and one of the main items in diet of ruminants, and their physical and chemical characteristics can directly affect the digestive physiology in the rumen. In the practice, the fiber in the balance of diets given different terms, according with their solubility and degradation characteristics. These terms, including FB (crude fiber), NDF (neutral detergent fiber) and ADF (acid detergent fiber), NDF being more related to structural carbohydrates (cellulose, hemicellulose and pectin), which is more used to interfere in the diet utilization by animal, their quantity can stimulate or inhibit food intake by ruminants. Based on the physical characteristics of NDF two new concepts were developed: physically effective NDF (peFDN) related to particle size and effective NDF (eFDN) related with the ability of food in maintained the percentage of fat in milk. The FDA refers to cellulose, lignin, silica and protein, and is used to estimated the hemicellulose by subtraction of ADF from NDF. The fiber stimulates chewing, serves as substrate for microorganisms, contribute to maintenance of the fermentative standards and rumen ambient stability. Thus, the fiber in diet of ruminants when not available in quantity and quality at animals may compromise the performance and interfere in the final products characteristics, yonder cause disturbances in the energy metabolism of animals.
This study showed the effect of feed restriction on performance, nitrogen balance (NB), microbial protein synthesis, carcass traits and meat cut of the thirty-two Sindhi non-castrated males (296 ± 21.3 kg initial BW and 21 ± 1.5 months old). All bulls were distributed in a completely randomized design with four treatments (feed restriction levels) (0, 15, 30, and 45% in total dry matter -DM) and the data were subjected to analysis of variance and regression. Nutrient intake, NB, final BW, total gain, feeding efficiency, carcass gain, hot and cold carcass weight, subcutaneous fat thickness, commercial cuts and fat tissue decreased linearly (P<0.05) by feed restriction level. A linear increased on digestibility of DM, NDFap, total carbohydrates and on the proportion of muscle tissue, as well as quadratic increase on non-fibrous carbohydrates and bone tissue percentage with the restriction level imposed on bulls (P<0.05). The feed restriction did not affect (P>0.05) the digestibility of crude protein, synthesis and microbial efficiency, deposition efficiency, longissimus dorsi area and muscle + fat/bone ratio. The feed restriction reduced intake and consequently performance, carcass traits and meat cuts of Sindhi bulls; however, it promoted a reduction in the N excretion, which can be important if conducted a subsequent compensatory weight gain.
A demanda pela produção de leite no Brasil tem sido cada vez maior e aliado a este fato observa-se crescentes melhorias no que diz respeito às práticas de manejo que proporcionam o aumento da produtividade associado aos avanços em relação aos estudos de comportamento e bem-estar animal, visto que estes constituem uns dos fatores mais importantes na promoção da sustentabilidade dos sistemas de produção animal. Atualmente tem-se notado grande preocupação da sociedade mundial em relação ao bem-estar animal que reflete na escolha dos alimentos, ou seja, a tendência é que o mercado consumidor procure cada vez mais produtos que sejam provenientes de sistemas de produção que respeitem os padrões de bem estar animal. Portanto, essa revisão de literatura propende abordar temas que merecem uma atenção visando um melhor bem-estar animal para incrementar a produtividade.
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