The effect of proanthocyanidin-rich hulls and proanthocyanidin extracts from bean (Vicia faba L.) hulls on nutrient digestibility and digestive enzyme activities in young chicks

Dietary plant bioactives for poultry health and productivity

1. Plants and their biologically active chemical constituents, sometimes called secondary metabolites or bioactives, present numerous opportunities for the improvement of livestock production by inclusion in the diet. 2. Many such plant derived materials have well established therapeutic values in man; however, their potential as feed additives in animal production, particularly of poultry, remains largely unexploited. 3. There is increasing evidence indicating that they can be efficient in controlling diseases, and plant bioactives may also influence production parameters such as feed efficiency and product quality. 4. It has been reported that they may even replicate some of the effects of antibiotic growth promoters, which were banned from use in Europe from 2006. 5. This review assesses the status of plant bioactives in poultry production and their mode of action on avian physiology, particularly in the digestive tract.

Hormone-related, muscle-specific changes in protein metabolism and fiber type profile after faba bean intake

Male growing Wistar rats were fed, over 15 days, isoenergetic (16.72 +/- 0.49 MJ) and isoproteic (11%) diets containing either lactalbumin or raw Vicia faba L. (Vf) as the sole source of protein. Compared with pair-fed controls (PF), soleus muscles of Vf-fed rats showed increased (P < 0.05) synthesis and breakdown rates. In addition, the soleus of Vf-fed rats displayed a decrease (P < 0.05) in type I and an increase (P < 0.01) in type IIc fibers compared with that of PF animals. On the contrary, extensor digitorum longus muscles of both Vf-fed and PF rats showed an increase (P < 0.01) in type I and a reduction (P < 0.05) in type IIb fibers together with a decrease (P < 0.05) in the cross-sectional area of the latter fibers. Vf-fed rats exhibited a significant decrease in serum insulin (P < 0.05) and thyrotropin (P < 0.01) levels, together with an increase in plasma glucagon (P < 0.05) and 3,5,3'-triiodothyronine (P < 0.01) concentrations, compared with the PF group. Both Vf-fed and PF rats experienced an increase in corticosterone concentrations (P < 0.01 vs. control; P < 0.05 vs. PF). The muscle-specific changes in both protein metabolism and fiber type composition may partly depend on the hormonal changes that were observed after Vf intake.

The effect of condensed tannins in Lotus corniculatus on plasma metabolism of methionine, cystine and inorganic sulphate by sheep

Fresh Lotus corniculatus containing 27 g extractable condensed tannin (CT)/kg dry matter (DM) and 8 g bound CT/kg DM was fed at hourly intervals to sheep held in metabolism cages to study the effects of CT on nutrient digestion and on metabolism of methionine, cystine and inorganic sulphate in plasma. Polyethylene glycol (PEG) was continuously infused into the rumen of half the sheep to remove the effects of CT. Principal measurements in the two groups were plasma irreversible loss (IRL) rate and interconversions of methionine, cystine and inorganic sulphate using 35S labelling. CT in Lotus corniculatus had no effects on the apparent digestion of cellulose and minerals, slightly depressed DM, organic matter and hemicellulose digestion and markedly reduced the apparent digestion of N (P < 0.01). The concentration of NH3 and molar proportions of iso-butyric acid, iso-valeric acid and n-valeric acid in rumen fluid were markedly increased by the PEG infusion (P < 0.01), whereas total volatile fatty acid concentration and molar proportions of acetic acid, propionic acid and n-butyric acid were not affected. PEG infusion temporarily increased rumen protozoa numbers. CT greatly increased the IRL of plasma cystine (13.1 v. 7.0 mumol/min; P < 0.05) and reduced IRL of plasma inorganic sulphate (36.8 v. 48.1 mumol/min; P < 0.01) but had no effect on methionine IRL. CT increased transulphuration of methionine to cystine (4.37 v. 1.24 mumol/min; P < 0.05), increased cystine entering the plasma from whole-body protein turnover plus absorption from the small intestine (9.34 v. 5.75 mumol/min; P < 0.05) and increased cystine flux to body synthetic reactions (11.89 v. 5.41 mumol/min; P < 0.05). CT had no effect on the proportion of methionine total flux transferred to sulphate (0.05 v. 0.06; P < 0.05), reduced the proportion of methionine flux transferred to body synthetic reactions (0.68 v. 0.86) and markedly reduced the proportion of cystine flux transferred to sulphate (0.09 v. 0.27; P < 0.01). It was concluded that CT in Lotus corniculatus reduced rumen protein degradation and markedly increased utilization of plasma cystine for body synthetic reactions.

Effect of condensed tannins in hulls of faba beans (Vicia faba L.) on the activities of trypsin (EC 2.4.21.4) and chymotrypsin (EC 2.4.21.1) in digesta collected from the small intestine of pigs

The effects of condensed tannins in hulls of faba beans (Vicia faba L.) on the activities of trypsin (EC 3.4.21.4) and chymotrypsin (EC 3.4.21.1) in digesta obtained from the small intestine of pigs were studied. Using four castrated male pigs (mean body weight 83 kg) fitted with both a simple T-cannula in the duodenum and a post-valvular T-cannula at the terminal ileum, two experimental diets were tested in a Latin square design. The low-tannin diet (LT) contained 200 g faba bean hulls (cv. Blandine)/kg with a low content of condensed tannins (< 0.1% catechin equivalents). The high-tannin diet (HT) contained 200 g faba bean hulls (cv. Alfred)/kg with a content of condensed tannins of 3.5% catechin equivalents. Spot samples of fresh duodenal digesta were taken daily at fifteen time points between 08.00 and 20.00 hours on four consecutive days. Ileal digesta were collected nearly quantitatively on the same days between 08.00 and 20.00 hours over periods of 2 h. Trypsin and chymotrypsin activities in duodenal digesta did not differ between treatments at any time point (P > 0.05). In ileal digesta of pigs given diet HT the mean activity of trypsin was reduced (P < 0.05). The activity of chymotrypsin in ileal digesta did not differ between treatments. Trypsin activity:chymotrypsin activity was somewhat lower in ileal digesta of pigs receiving the HT diet (P < 0.10). The apparent ileal digestibility of crude protein (N x 6.25) was lower for the HT than for the LT diet (0.614 v. 0.728; P < 0.05). Condensed tannins are probably responsible for the lower activity of trypsin in ileal digesta of pigs fed on high-tannin faba bean hulls. Various explanations for the absence of effects of condensed tannins on enzyme activity in duodenal digesta are discussed.

The influence of proanthocyanidin-rich bean hulls and level of dietary protein on energy metabolizability and nutrient digestibility by adult cockerels

Cotyledons and hulls were prepared from twelve varieties of field beans (Vicia faba L.). Adult cockerels were tube-fed either beans, cotyledons or hull diets containing high or low levels of protein. Metabolizable energy coefficients and starch digestibility coefficients were determined for beans, cotyledons and hull diets. Lipid digestibility coefficients from hull diets were also determined. When cotyledons were fed there were no significant differences in the way in which adult cockerels metabolized energy or digested starch from the proanthocyanidin-free and proanthocyanidin-rich varieties (0.780, 0.908, 0.775 and 0.918 respectively). When beans were fed, however, both energy metabolizability and starch digestibility decreased due to the presence of hulls, with proanthocyanidin-rich hulls decreasing values the most to 0.660 and 0.819 respectively, and proanthocyanidin-free hulls decreasing values to a lesser extent to 0.709 and 0.886 respectively. Diets composed of proanthocyanidin-rich hulls depressed metabolizable energy and maize starch digestibility. Their effect on maize starch digestibility, however, was considerably less than that on bean starch. Lipid digestibility was enhanced by proanthocyanidins but only when the protein content of the diet was high. There was a significant correlation (P < 0.05) between the vanillin and anthocyanidin formation methods for the estimation of proanthocyanidins (r 0.779). There was also a highly significant regression of bean starch digestibility v. proanthocyanidin content of coloured-flowered bean hulls (P < 0.001). The regression of maize starch digestibility v. hull proanthocyanidins was also significant at P < 0.005.