Desempenho produtivo, exigências nutricionais e avaliação de métodos para estimação de fluxo de digesta em bovinos alimentados com silagem de milho ou cana-de-açúcar

• Autor(a) principal: Rotta, Polyana Pizzi
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5724
• topic: Silagem de milho; Cana; Indicadores; Fluxo de digesta; Corn silage; Sugar cane; Marker; Digesta flow; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL

This work was developed from four experiments to evaluate the dry matter and nutrients intake, digestibility, animal performance, carcass characteristics, energy and protein requeriments, chemical composition and fatty acid profile of Longissimus dorsi muscle; and to evaluate the ruminal outflow of dry matter and components of digesta sampling in three sites (abomasum, omasum and reticulum) and evaluate three marker systems (single, double and triple). In the experiment 1, 36 crossbred bulls (Holstein × Zebu). with average body weight of 328 ± 39.47 kg and 24 months were used. The bulls were randomly allocated in six different diets, with six bulls in each one. The diets evaluated were corn silage (CS) and sugar cane (SC) with 60 or 40% of dry matter (DM). The experimental diets were: 1) 60CS:40% concentrate (C) (84 days); 2) 60CS:40C (42 days) and 40CS:60C (42 days); 3) 40CS:60C (84 days); 4) 60SC:40C (84 days); 5) 60SC:40C (42 days) and 40SC:60C (42 days); 6) 40SC:60C (84 days). The bulls fed with 40% of corn silage presented higher (P<0.05) average daily gain in comparion with those fed with sugar cane. However, there were no differences (P>0.05) for average daily gain between the diets with 60% of corn silage and 40% of sugar cane. It was observed a positive effect to reverse diets on daily gain. When sugar cane was fed, it was observed an increase in average daily gain in bulls fed with reverse diets in comparison with the diet with a higher proportion of roughage. It can be concluded that sugar cane can replace corn silage in diets of crossbred (Holstein × Zebu) bulls finished in feedlot, but it is necessary to increase 20% in the amount of concentrate in the diet. The experiment 2 was realized using a comparative slaughter, with 44 crossbred bulls (Holstein × Zebu) with 338 ± 39.01 kg and 24 months. The bulls were randomly separated in: four bulls to reference group, four bulls to maintenance level group and 36 bulls fed ad libitum. The bulls of the last group were randomly separated in the same diets described in the experiment 1. The net (NEm) and metabolizable (MEm) energy requirements to maintenance were 78.7 e 114.2 kcal/EBW0.75/day, respectively. The km was 0.6891. The equations obtained to NEg and NPg were: NEg (Mcal/day) = 0.0493 × EBW0.75 × EBG1.0013 and NPg (g/day) = 279.19 × EBG 22.8691 × RE, respectively. The kg was 0.4634. The efficiencies to deposition of energy as protein and as fat were 0.2048 and 0.8848, respectively. The model obtained for the percentage of retained energy as protein (%REp) was %REp = 1.7202 × (RE/EBG)-1.351. This study concluded that NEm and MEm to Holstein × Zebu bulls were 78.7 and 114.2 kcal/EBW0.75/day, respectively, and the NEg and NPg can be obtained by the equations: NEg (Mcal/day) = 0.0493 × EBW0.75 × EBG1.0013 and NPg (g/day) = 279.19 × EBG 22.8691 × RE, respectively. In the experiment 3, 36 crossbred bulls (Holstein × Nellore) with 24 months and body weight of 328 ± 39.01 kg were used. It was used the same diets described in the experiment 1. At the final of the experiment, the bulls were slaughtered at Universidade Federal de Viçosa and a sample located between 12 and 13rd ribs of each bull was took and it was vacuum-packed and frozen at -20ºC to further analyses. The chemical composition in Longissimus dorsi muscle was not influenced (P>0.05) by the different diets. The percentage of the C 18:3 n-3 fatty acid, a strictly essential fatty acid, was higher (P<0.05) in Longissimus dorsi muscle of bulls fed with sugar cane independently of the ratio of roughage concentrate used. The same way, the percentage of C 20:5 n-3, an essential fatty acid, was higher (P<0.05) in Longissimus dorsi muscle of bulls fed with sugar cane independently of the ratio of roughage concentrate used. The percentage of C 18:2 c 9 t 11 was higher (P<0.05) in Longissimus dorsi muscle of bulls fed with sugar cane at 60:40 and 60:40 40:60. Thus, bulls fed with sugar cane present better fatty acid profile in relation with bulls fed with corn silage. This is due the increase of the essential and strictly essential fatty acids in Longissimus dorsi muscle of bulls fed with sugar cane. In the experiment 4, eight crossbred bulls (Holstein × Zebu) fitted with ruminal and abomasal cannulas and with 24 months, weighting 353 ± 36.94 kg were separated in two 4 × 4 Latin squares design. The experimental diets were: 1) 60% of corn silage + 40% of concentrate; 2) 40% of corn silage and 60% of concentrate; 3) 60% of sugar cane + 40% of concentrate; 4) 40% of sugar cane + 60% of concentrate. Eight digesta samplings were realized in each experimental period with intervals of nine hours. At the end of each experimental period it was realized a sample pool and the samples were appointed to the three marker systems (single system: sample without separation; double system: filtred sample; and triple system: filtred and centrifuged sample). The whole reticular digesta composition was different (P<0.05) in comparasion with the others to ether extract (EE), neutral detergente fiber (NDF) and indigestible NDF. The digestas sampled at the abomasum and omasum presented similar (P<0.05) values to rumen outflow to dry matter (DM), organica matter (OM) and NDF. Likewise, the abomasal and omasal digestas were similar (P>0.05) to estimate of ruminal digestibility of DM, OM, crude protein (CP) and NDF. Digestas sampled at abomasum and omasum presented similar (P>0.05) values to estimate the intestinal digestibility of OM, CP and NDF. The omasal sampling is recommend as an alternative to abomasal sampling. Because no difference (P>0.05) among the marker systems to ruminal and intestinal digestion for NDF and intestinal digestion for CP, any marker systems can be used. Therefore, based on few differences in rumen outflow and digestions of estimating with double and triple marker systems, it is recommended the use of double marker system (indigestible NDF and Co-EDTA), that can be accessible to any research center.