Corrêa, ângela Maria de Vasconcelos, Valadares Filho, Sebastião de Campos, Lana, Rogério de Paula, Leão, Maria Ignez, Valadares, Rilene Ferreira Diniz, and Rennó, Luciana Navajas
Fundação Cearense de Apoio ao Desenvolvimento Cientifico e Tecnológico The research was carried out to evaluate the in situ ruminal degradation and the intestinal digestibility of raw and roasted soybeans and the effect of diets containing different forms of soybeans on the consumption, nutrient digestibility, production and milk composition, variation in pH and ruminal N-NH3 concentration, urea excretion in urine, concentrations of ureic nitrogen compounds in milk and plasma, nitrogen compound balance, microbial production and thermal environment effect on physiological and productive variables. Twelve pure and crossbred Holstein cows were used in the experiments II, III and IV. The cows were grouped according to milk production and lactation days, used in three simultaneous 4x4 Latin squares and fed the following isoproteic diets: only soybean meal (SM- control diet), raw soybean (RS), roasted soybean (RTS) and soybean meal plus 5% urea (SMU), and total diet consisting of 50% of roughage. The experimental periods were 21 days, the first 14 days for adaptation to the diet and the last 7 for data collection. Experiment I, using the in situ nylon bag technique, evaluated the ruminal degradation kinetics of dry matter (DM) and crude protein (CP) at 2, 4, 8, 16, 24 and 48 hours and the intestinal digestibility of crude protein that is not degraded in the rumen by the three-step method. The following six treatments were applied: raw soybeans - T1; soybeans heat-treated at 125 oC for 3 min with and without steeping -T2 and T3; at 145 oC for 1 min with steeping -T4; at 115 oC for 4 min with steeping - T5; and at 110 oC for 5 min without steeping -T6. The roasted soybeans, independently of the temperature and roasting procedure (with and without steeping), showed lower means of DM and CP effective degradability (ED) than the control diet. Treatment four (T4) was the least degraded with 61.33% of DM effective degradability and 52.23% of CP. The intestinal digestibility of raw soybeans was higher and showed significant effect (P 0.05) among the different diets. CP consumption was affected (P 0.05). NFC digestibility was lower (P 0.05). The tested diets added with 50% of corn silage (DM basis) replacing soybean meal can be fed to high production cows without compromising milk production and composition. The experiment III evaluated the effect of different forms of soybeans on variation in pH and ruminal ammonia, urea excretion in urine (UEU), concentration of ureic nitrogen in milk (UNM) and in plasma (UNP), nitrogen compound balance (NB) and microbial synthesis and efficiency. There was effect (P 0.05) among the diets, whereas the secretion of UNM was significant (P 0.05) and significant differences were neither found (P>0.05) in the excretion of total purine derivatives (PD) nor in the ruminal microbial synthesis and efficiency, which was expressed as g of CP/kg of consumed TDN for the different diets. It was concluded that the tested diets did not affect nitrogen balance nor microbial production, however the addition of raw soybeans increased nitrogen levels in the milk. The experiment IV evaluated the thermal environment effect on the following physiological variables: respiratory frequency (RF), cardiac frequency (CF), rectal temperature (RT), sweat rate (SR); and the productive variables: dry matter consumption (DM), total milk production (TMP), protein (P%) and fat (F%). Significant differences were found (P < 0.05) for all the physiological variables, except for SR. When DM consumption was analyzed, the lowest value was found (P 0.05). Protein content was lower (P 0,05) nas dietas. O consumo de PB foi influenciado (P0,05). A digestibilidade dos CNF foi menor (P0,05). As dietas testadas podem ser usadas para vacas de alta produção juntamente com 50% de silagem de milho na MS em substituição ao farelo de soja. No experimento III, avaliou-se o efeito da soja em diferentes formas sobre a variação do pH e a amônia ruminal, a excreção de uréia na urina (EUU), a concentração de nitrogênio uréico no leite (NUL) e no plasma (NUP), o balanço de compostos nitrogenados (BN) e a síntese e eficiência microbiana. Houve efeito (P0,05) entre as dietas, porém a secreção do NUL foi significativa (P0,05) e também não foram observadas diferenças significativas (P>0,05) na excreção total de derivados de purinas (PT) e, na síntese e eficiência microbiana ruminal, expressa em g de PB/kg de NDT consumido. Concluiu-se que as dietas usadas não afetaram o balanço de nitrogênio nem a produção microbiana, porém a inclusão de grãos de soja crus aumentou os teores de nitrogênio do leite. No experimento IV, avaliou-se o efeito do ambiente térmico sobre as variáveis fisiológicas: freqüência respiratória (FR), cardíaca (FC), temperatura retal (TR), taxa de sudação (TS) e variáveis produtivas: consumo de matéria seca (CMS), produção total de leite (PTL), proteína (P%) e gordura (G%). Foram verificadas diferenças significativas (P0,05). O teor de proteína foi menor (P