Performance of Nellore cattle fed individualy or in group, nutrient requirements and proteic evaluation of feeds for ruminants / Desempenho de bovinos Nelore alimentados individualmente ou em grupo, exigências nutricionais e avaliação protéica de alimentos para ruminantes

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The present work was developed based on four experiments. The two firsts were conducted aiming to evaluate the fecal dry matter production using total fecal collection or estimated by chromic oxide (Cr2O3), titanium dioxide (TiO2), isolated, purified and enriched lignin of Eucalyptus grandis (LIPE), indigestible neutral and acid detergent fiber (NDFi and ADFi, respectively), in two periods of sample collection (three or five days); to evaluate the use of Cr2O3 and TiO2 to estimate the individual intake of concentrate, and the use of NDFi and ADFi to estimate the individual intake of roughage; and to determine the dry matter intake, the digestibilities coefficients of dry matter and of the nutrients and to determine the microbial protein production in Nellore cattle of three genders. In the first experiment, four heifers were fed with sugar cane plus 1,0% of urea/ammonium sulfate on as-fed basis, ad libitum and 1,0% of live weight in concentrate, fed separate from roughage. Each animal was considered as sub-block (main plots), in a splitplitplot design, being the methods to estimate fecal dry matter the sub-plot and the sampling days the sub-sub-plot. The Cr2O3 and TiO2 were mixed in the concentrate (10 g/animal), and the LIPE was introduced via cannula (0,5 g/animal). In the second trial, eighteen animals were used, allotted to a complete randomized design, in factorial design 2x3, being two levels of concentrate offer and three genders. The diets had 12,5% CP in the dry matter and the roughage used was corn silage. The ruminal synthesis of nitrogen compounds was estimated using the purine derivatives. All markers estimated properly the fecal dry matter production, with no effects in the sample period, excepting ADFi. There was not difference between Cr2O3 and TiO2 to estimate the individual concentrate intake (P>0,05). There was no significant difference (P>0,05) between genders and levels of concentrate in dry matter intake and nutrient digestibilities, excepted for ether extract. The average microbial efficiency was 133,42 g of microbial CP/kg of TDN. Therefore, it is recommended to use three days of sample collection period because its cheaper and less labor intensive. The final decision when choosing between Cr2O3 and TiO2 to estimate concentrate intake has to take in account the availability, its cost and laboratorial analysis. The NDFi can be used to estimate the roughage intake. There were not differences in the dry matter intake between Nellore bulls, steers and heifers. The gender didnt influence the microbial protein production. The third experiment was developed aiming to estimate the individual intake of dry matter, concentrate and roughage of animal fed in group. To evaluate the dry matter intake (DMI), daily weight gain (DWG) and feed conversion (FC) by animals of three genders, fed individually or in group, fed two levels of concentrate offer; and determine the effect of two levels of concentrate offer (1, 0% of live weight or 1,25% of live weight) and the genders effect in carcass traits of confined Nellore cattle. It was also the objective to validate the Hankins and Howe (1946) equations, to estimate the carcass physic composition, and the Paulino (2002) equations, to estimate the empty body weight macromineral composition of Nellore cattle; determine the metabolized requirements of energy for maintenance and liquid requirements of crude protein, energy and macromineral for gain, and also the efficiency of conversion of liquid protein requirements into metabolized protein requirements in Nellore cattle. Forty five Nellore (15 bulls, 15 steers and 15 heifers) were used, being nine animals (three of each genders) slaughtered at the beginning performing the reference group. The 36 animals remaining (12 of each gender) were allotted in two levels of concentrate offer (1,0% and 1,25% of live weight) and two schemes of feeding (individually or in group), in a factorial design 2x2x3. The trial lasted 112 days. To estimate the individual DMI of the animal fed in group, the LIPE was used to estimate the fecal dry matter production, the Cr2O3 and TiO2 to estimate the individual concentrate intake and NDFi and ADFi were used to estimate the individual roughage intake. At the end of the experiment all animals fed individually were slaughtered to determine the empty body weight and corporal composition, being the right carcass divided in five commercial cuts. From left carcass the HH section was obtained. The liquid requirements for gain were obtained by deriving the equation of corporal content of each nutrient, in function of log of empty body weight. The metabolized energy requirements for maintenance were estimated by a regression of retained energy and metabolized energy intake. The efficiency of conversion into metabolized protein was estimated by regressing the protein retained and metabolized protein intake. There were not effects (P>0,05) of concentrate level and feed scheme in DMI, DWG and FC. Bulls were superior to steers in some weights of the commercial cuts and steers were superior to females. Paulinos (2002) equation was efficient to estimate Ca concentration in the empty body weight. For all macromineral were proposed news equations to estimate its contents in empty body weight using the HH section. The equations obtained for retained energy were: RE = 0,0559*EBW0,75*EBWG1,1037 (bulls); RE = 0,0738*EBW0,75* EBWG0,9688 (steers); RE = 0,1020*EBW0,75*EBWG1,0408 (females). The feed scheme did not influence the DMI and DWG of Nellore cattle of three genders. Bulls grow 24% faster than steers and steers grow 22% faster than females. The concentrate offer between 1,0 and 1,25% of live weight did not influence carcass traits in Nellore cattle. Bulls were more efficient in meat deposition and had higher yield in some commercial cuts. Liquid energy requirements for gain increase with higher live weights while liquid protein requirements for gain decrease with higher live weights. The metabolized energy requirements for maintenance were higher for females and the efficiency of conversion into metabolized protein is about 50%. It can be concluded that is possible to estimate the macromineral composition using the HH section in Nellore cattle. The fourth experiment was developed aiming to determine the fraction A, B and kd of dry matter and crude protein of 27 feeds used for ruminants in Brazil. It was also the objective of the trial to determine the intestinal digestibility of rumen undegraded protein by the three steps and the mobile nylon bag techniques. Four Nellore females, cannulated in rumen and duodenum, were fed ad libitum with corn silage and concentrate. The Orskov and McDonald (1979) model was used to obtain the rumen degradability of DM and CP, and the times of incubation were 0, 2, 4, 6, 12, 16, 24, 48 and 72 hours, being after that determined the DM and total nitrogen in the residues of incubation. To determine the intestinal digestibility (ID) of CP was used the three steps and the mobile nylon bag techniques. The ruminal degradation of DM and CP data were similar to literature. The three step technique did not estimate properly the ID of all feed evaluated, excepted for the proteic feeds. The soybean meal (93,95%) had the higher ID of CP using the mobile nylon bag technique, and corn (85,58%), cotton seed meal 46% of CP (84,93%), corn gluten (82,98%) comes after. It can be concluded that the most feeds have total CP digestibility higher or next to 90%, excepting for soybean, coffee and cacao hulls and elephant-grass and corn silage. It is recommended to use the equation IDCP (%) = 5,1906 + 1,1053*X, to correct the ID obtained by the three steps technique for non-proteic feeds, being X the ID obtained by the three steps technique.

ASSUNTO(S)

intake in group nutrition requirements bovino digestibilidade intestinal nutricao e alimentacao animal bovine consumo em grupo necessidades indicadores nutrição digestibility

ACESSO AO ARTIGO

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