Malic acid combined with heat treatment to protect protein from soybean meal against rumen degradation

Abstract

-The protection of proteins from soybean meal (SBM) by treatments with solutions of malic acid (at two crescent doses) and heat was studied in a 3 × 3 Latin-square design using three diets and three wethers cannulated in the rumen and in the duodenum. Solutions 2.25 and 4.50 N of malic acid were pulverised (400 mL·kg −1 ) on SBM under continuous mixing. Then, the treated meals were dried in an oven at 117• C for 6 hours. The diets were isoproteic and included 55% lucerne hay and 45% concentrate, with untreated (UT) and treated SBM (T2.25N and T4.50N). The diets were distributed, at 50 g·kg −1 BW 0.75 , in six equal meals (every 4 h). The estimates of ruminal effective degradability (ED) of dry matter (DM) and crude protein (CP) of SBM samples were obtained using in situ and rumen outflow methods, whereas the intestinal digestibility (ID) was determined by the mobile nylon bag technique on residues incubated in the rumen for 8 h. The effects of the addition of malic acid in the diet on rumen fermentation patterns and fibrolitic activity (measured by the in situ degradation of the lucerne hay) were also determined. The treatments did not alter the digestive transit kinetics of SBM particles, which showed rumen outflow rates in the interval from 5.5 to 6.1%·h −1 . Degradation of CP showed a sigmoidal shape in all samples and was described well with a simple exponential model, based on a constant fractional degradation rate (k d ), or using a logistic model in which the fractional degradation rate increases with time from an initial (k o ) to a final (k ∞ ) value. According to the first model, the k d value corresponding to the protective treatments showed a tendency (P = 0.054) to decrease with the treatments (from 4.71 to 3.32 and 3.35%·h −1 for UT, T2.25N and T4.50N, respectively). In the second model, this deceleration of CP degradation only affected k o (P = 0.039), whereas, no effect was observed on k ∞ . These changes reduced moderately the ED of CP of the treated samples (15-16%) in relation to the untreated SBM, although differences were not significant (46.2, 39.3 and 38.5%, respectively, as mean of both models). No effect was observed for the ID of CP with values shown between 99.0 and 99.4%. Including malic acid in the diet did not have an important effect on the degradation of DM and fibre fractions of lucerne hay or on the parameters of ruminal fermentation, except for a decrease (P = 0.050) of the acetic acid:propionic acid ratio (4.44, 3.53, and 3.78 for UT, T2.25N and T4.50N, respectively). Résumé -L'acide malique associé au traitement thermique pour protéger les protéines issues du tourteau de soja des dégradations ruminales. La protection des protéines du tourteau de soja par des traitements combinant des solutions d'acide malique (à deux doses croissantes) et la chaleur a été étudiée selon un dispositif en carré latin 3 × 3 avec trois régimes et trois moutons castrés porteurs de canules du rumen et du duodénum. Des solutions de 2,25 et 4,50 N d'acide malique ont été pulvérisées (400 mL.k...

In vitro efficiency of combined acid-heat treatments for protecting sunflower meal proteins against ruminal degradation

“…In this manner, the protective effect of acid treatments should be mainly determined by protein denaturation through the reduction of its solubility (as shown in Trial 4) and fermentation rate. The reduction of this rate with acid treatments has been shown in previous in situ studies (Vicini et al, 1983;Waltz and Loerch, 1986;Ouarti et al, 2006). The lack of effect of the treatment with water on CP solubility and its lower effect than acids on IVUCP (Table 4) also show the effectiveness of the acid treatments.…”

“…Another benefit of these last treatments was to multiply by three times the intestinal digestible supply from this meal of lysine and methionine and by 3.7 that of cysteine . Similarly, Ouarti et al (2006) protecting soybean meal with malic acid at 0.9 and 1.8 eq/kg and drying temperatures of 1178C for 6 h did not find negative effects on the intestinal digestibility of the undegraded protein, which was nearly complete. Besides, the inclusion at 5% of these treated meals in an alfalfa hay-concentrate diet did not alter the pH, the concentration of volatile fatty acids or the fibrolytic ability of the rumen, but reduced the excessive ammonia concentration resulting from the diet fermentation as well as the acetic acid/propionic acid ratio, attributing this latest effect to the incorporation of malate to the diet.…”

“…Malic acid (or malate) has been indicated as a promise additive to improve ruminal fermentation efficiency through a reduction of the acetic acid : propionic acid ratio (Martin and Streeter, 1995;Callaway and Martin, 1996;Carro et al, 1999), which, together with the providing ruminally fermented energy, should prove useful. In addition, in vivo studies with malic acid-heat treatments of Ouarti et al (2006) showed both a protein protective effect and a reduction of the above cited ratio without negative effects on ruminal and intestinal digestion.…”

“…Moreover, treatments with acid solutions, with or without a posterior heat treatment, can decrease ruminal protein degradation of feedstuffs (Atwal et al, 1974;Vicini et al, 1983;Waltz and Loerch, 1986). Ouarti et al (2006) indicated that a combination of acid with heat treatments may act synergistically and reduce disadvantages of either method. Less intense heat treatment decreases both the cost of energy and the generation of irreversible Maillard reactions associated with overprotecting protein; and use of less acid for treatment will reduce its impact on microbial activity and effects on the rumen environment.…”

“…Most studies utilizing acids to decrease ruminal degradation of protein have used soybean meal (Vicini et al, 1983;Waltz and Loerch, 1986;Szokoly and Schmidt, 2005;Ouarti et al, 2006) or canola meal (Khorasani et al, 1989). Sunflower meal has not been tested previously despite its high ruminal crude protein (CP) degradability, commonly above 0.80 (Gonzá lez et al, 1999;Woods et al, 2003;Rotger et al, 2006) that should allow for the protective response to be large.…”