Malic acid or orthophosphoric acid-heat treatments for protecting sunflower (Helianthus annuus) meal proteins against ruminal degradation and increasing intestinal amino acid supply

Abstract

The protection of sunflower meal (SFM) proteins by treatments with solutions of malic acid (1 M) or orthophosphoric acid (0.67 M) and heat was studied in a 3 3 3 Latin-square design using three diets and three rumen and duodenum cannulated wethers. Acid solutions were applied to SFM at a rate of 400 ml/kg under continuous mixing. Subsequently, treated meals were dried in an oven at 1508C for 6 h. Diets (ingested at 75 g/kg BW 0.75 ) were isoproteic and included 40% Italian ryegrass hay and 60% concentrate. The ratio of untreated to treated SFM in the concentrate was 100 : 0 in the control diet and around 40 : 60 in diets including acid-treated meals. The use of acid-treated meals did not alter either ruminal fermentation or composition of rumen contents and led to moderate reductions of the rumen outflow rates of untreated SFM particles, whereas it did not affect their comminution and mixing rate. In situ effective estimates of by-pass (BP) and its intestinal effective digestibility (IED) of dry matter (DM), CP and amino acids (AAs) were obtained considering both rates and correcting the particle microbial contamination in the rumen using 15 N infusion techniques. Estimates of BP and IED decreased applying microbial correction, but these variations were low in agreement with the small contamination level. Protective treatments increased on average the BP of DM (48.5%) and CP (267%), mainly decreasing both the soluble fraction and the degradation rate but also increasing the undegradable fraction, which was higher using orthophosphoric acid. Protective treatments increased the IED of DM (108%) and CP, but this increase was lower using orthophosphoric acid (11.8%) than malic acid (20.7%). Concentrations of AA were similar among all meals, except for a reduction in lysine concentrations using malic acid (16.3%) or orthophosphoric acid (20.5%). Protective treatments also increased on average the BP of all AA, as well as the IED of most of them. Evidence of higher increases for those AA showing a high resistance to degradation in the untreated meal were also observed. The total supply of metabolisable AA was increased by 3.87 times for sulphur-containing AA, whereas that of lysine was increased by 2.5 times, mainly because of lysine losses with heat treatments. These treatments and especially that with malic acid would be useful to increase the protein value of these meals but their combined use with lysine-rich protein concentrates would improve the metabolisable protein profile.

Protection of sunflower seed and sunflower meal protein with malic acid and heat: effects on in vitro ruminal fermentation and methane production

“…Similar results have been reported for other rich‐protein feeds, indicating that heat treatment did not produce total N loss. The actual effects of acid and heat treatment on protein are influenced mainly by acid concentration, pH, heating time, temperature and moisture, although differences in susceptibility of different feeds have been reported to be large . Due to the impact of heat in feeds previously processed, such as the SM, the increases in NDF and ADF observed after heat treatment are usually greater in raw samples than in samples previously heated, which is in agreement with the higher increases observed in SS compared with SM in the present study.…”

“…Five hundred grams of each substrate were weighed and pulverised with a solution of 1 mol L −1 malic acid at a rate of 400 mL per kg of feed and left at room temperature for 1 h. Samples were then dried at 150°C for either 1 (MAL1) or 3 h (MAL3). The concentration of malic acid and the duration of the heat treatment were selected from the results of previous studies . The chemical composition of the untreated (UNT) and treated samples is shown in Table .…”

“…The treatment of high‐protein feeds with heat and/or acid solutions has proven to be useful for protecting proteins from microbial degradation in the rumen, but the efficacy of these treatments varies with different factors, such as the type and concentration of acid and the heat intensity and duration . Previous in vitro and in situ studies have demonstrated the efficacy of a combined treatment with malic acid and heat to increase the protein value of sunflower meal (SM) and spring peas …”

Protecting protein against ruminal degradation could contribute to reduced methane production

“…The combined malic acid heat treatment was selected because its efficacy for protecting protein from ruminal degradation was proved in previous in situ and in vitro studies (Arroyo et al., , ; Díaz‐Royón, Arroyo, Sánchez, & González, ; Vanegas, González, Alvir, et al., ; Vanegas, Carro, et al., ). Malic acid, as other acids, causes denaturation of proteins, reduces its solubility and provides effective protection against degradation by ruminal microorganisms.…”

“…Diets with two different CP levels were formulated to analyse the possible interaction between treatment and CP level. Finally, the study examined the differences between diets at two incubation times (8 and 24 hr), as sunflower protein is rapidly degraded in the rumen (Arroyo et al., ) and the influence of treatment might become less marked as incubation time increased.…”