Chemical composition, in situ degradability and amino acid composition of protein supplements fed to livestock and poultry in Cyprus

M Hadjipanayiotou and S Economides

Agricultural Research Institute, 1516 Nicosia, P.O. Box 22016, Cyprus
miltos@arinet.ari.gov.cy

 
Abstract

Chemical composition, in situ degradability, in vitro digestibility of OM and amino-acid composition of 8 protein supplements used in livestock diets have been determined in the present study. Within legume seeds, Cyprus vetch had the highest (35.7%) content in CP followed by common vetch (31.5%); the CP content of chickpeas, field beans, narbon vetch and peas were relatively close (24-27%). True protein as percent of total-CP ranged from 83 to 94%; chickpeas having the lowest (83%), and peas the highest (94%). Chickpeas had  higher fat (5.3%) content than all other grains (1.14-1.62%). Legume seeds were rich sources of K (1.22%) and P (0.52%) and their Ca content was only around 25 and 10% of their P and K content, respectively. Overall, food legumes were good sources of Ca (0.14%), P, Fe (123 ppm) and Cu (15 ppm). Peas had the highest “D” value (95.5%) followed by Cyprus vetch (92.3%). The “D” value of the other grains ranged from 86 to 89%, and was close to that of soybean meal (88%). Legume grains were rich in lysine (1.79%) and poor in methionine (0.42%). The percentage of amino-acids to total-CP was similar in narbon vetch (98.7%), peas (95.0%) and soybean meal (96.0%); the corresponding values for common vetch, chickpeas, cyprus vetch and field beans were 71, 87, 83 and 82%, respectively. Effective CP degradability (ECPdg) in soybean meal was lower (P<0.05) than that of all other legume seeds, and of sunflower meal. Among legume seeds chickpeas had the lowest ECPdg followed in increasing order by common vetch, narbon vetch, peas, cyprus vetch and field beans. There were no significant differences in ECPdg between peas, chickpeas, common vetch and narbon vetch.

Key words: Legume seeds, protein supplements,  chemical composition, amino acid composition, rumen degradability 

Introduction

Imported protein supplements like soybean meal and many species of legumes that are potentially adapted to the dryland agricultural regions of Mediterranean countries are used in diets of highly producing ruminants. Continuous efforts are in progress (Gatel 1994) to achieve improvements in the yield and use of leguminous crops, which would result in greater availability of protein leading to reduction in imports of protein supplements. Data on the satisfactory performance of fattening (Koumas and Economides 1987; Hadjipanayiotou and Economides 1998) or lactating (Petit et al 1997) ruminants given diets containing leguminous grains have already been published. Furthermore, digestion coefficients of Cyprus vetch (Lathyrus ochrus), bitter vetch (Vicia ervilia), field beans (Vicia faba) and common vetch (Vicia sativa) have been determined by Hadjipanayiotou et al (1985). Food legumes containing two or three times the amount of protein in cereal offer the most practical means of eradicating protein malnutrition of the cereal-based diet of the populations of Mediterranean areas (Bahl 1988). Furthermore, the development of high yielding, mechanically harvested leguminous crops is expected to enhance their introduction in rotation systems leading to greater availability of local/regional protein supplements resulting in reduction of imports of animal protein supplements. 

The importance of evaluating the nutritional value of ruminant animal feedstuffs taking into consideration their amino-acid content as well as their protein ruminal metabolism has long been recognized (ARC 1980,1984; ARFC 1992). The present paper reports data on the chemical composition, amino-acid content and in situ degradability of imported protein supplements and of legume grains potentially adapted to semi-arid areas of the Mediterranean region.

Materials and Methods 

Measurements were made on six locally produced leguminous grains namely common vetch (Vicia sativa), chickpeas (Cicer arientum), cyprus vetch (Lathyrus ochrus), field beans (Vicia faba), narbon vetch (Vicia narbonensis), peas (Pisum sativa) and on imported solvent extracted soybean meal (Glycine max) and sunflower meal (Helianthus annuus). Leguminous grains were grown in Cyprus under rainfed conditions following traditional agronomic practices.

Chemical analyses

Proximate constituents, acid detergent fibre (ADF), neutral detergent fibre (NDF), acid detergent lignin (ADL) and true protein (TP) were determined as outlined by Harris (1970). All chemical analyses were made on samples ground to pass a 1 mm sieve. The method of Helrich (1990) was used for Ca, Mg, Cu, Zn, Mn and Fe determination. For total sulphur a modification of Garido’s (1964) method was used; P content was quantified colorimetrically using the ChemLab continuous flow autoanalyzer (ChemLab Instruments Ltd 1981) and Na and K photometrically after wet digestion. In vitro digestibility was measured following the Tilley and Terry (1963) technique as modified by O’Shea and Wilson (1965). 

Amino-acid analysis

The amino acid analysis on the six leguminous grains and on soybean meal was carried out using the waters AccQ-Tag amino acid analysis system (Bourgoin 1993). This involved the pre-column derivatisation of the free amino acids with 6-aminoquinoline followed by separation on a C18 HPLC with fluorescence detection. 

In situ degradability

The degradability in the rumen of the protein supplements was determined using three rumen fistulated dry, mature Damascus goats. Fistulated animals were offered daily 0.5 kg concentrate (160 g CP per kg DM) and 0.6 kg barley hay. Nylon cloth with 36 µm pore size (HSO 13, Henry Simon Ltd., P.O.Box 31, Stockport, England) was used for the bags. The dimensions of the bags were 140 x 90 mm, and about 5 g sample was placed in each bag. Bags were then anchored from the top of the cannula using 25 cm nylon tubing. Bags with content were incubated in the rumen for 2, 5, 8, 24 and 48 h. Three 3 bags/incubation/ interval/animal were used. The procedures used for bags and sample processing, chemical analysis and calculation of effective DM and CP degradability values were those outlined by Ørskov (1982) and Hadjipanayiotou et al (1988).  

Results and Discussion

All leguminous grains analysed in the present study had at least 2.5 times the CP of cereal grains grown under similar conditions (Table 1). In line with previous studies (Hadjipanayiotou et al 1985), cyprus vetch had the highest (35.7%) content in CP followed by common vetch (31.4%) whereas the CP content of chickpeas, field beans, narbon vetch and peas were relatively close (24-27%). Overall, the CP content of Cyprus vetch, chickpeas, field beans and common vetch was higher in the present study (Table 1) compared to those reported by Hadjipanayiotou et al (1985) (31.3, 20.2, 26.0 and 29.0% DM basis). Chickpeas had higher fat content than the other local leguminous grains. Higher fat content in chickpeas (4.3%) than in field peas (1.3%) and faba beans (1.3%) has also been reported by Dixon and Hosking (1992). There were differences among legume seeds in CF, NDF, ADF and ADL content (Table 1).  

Like other grains, legume seeds were rich sources of K and P, whereas their Ca content was only around 25 and 10% of their P and K content, respectively. The Ca content of legume seeds was somewhat lower, but P content was higher than previously reported values (Hadjipanayiotou et al 1985). Finally, among the leguminous grains, narbon vetch had the highest content in S (0.338%) and Fe (235 ppm). The fact that food legumes are a good source of minerals like Ca, P, Fe, Cu, and Mo has also been reported by Bahl (1988).

Peas had the highest D value (95.5%) followed by cyprus vetch (92.3%). The D value of the other leguminous grains ranged from 86 to 89%, and were close to that of soybean meal (88%). The higher D value of chickpeas and peas than the other leguminous grains may be explained by their higher fat and lower ash content, respectively. Sunflower had the highest ash (8.8%) and CF (27.9%) values and the lowest D value.

In line with previously reported data from different parts of the world (Chavan et al 1989; Eggum et al 1989; Moss et al 1997) legume proteins were rich in lysine and poor in methionine and tryptophan (Table 2). Methionine is reported to be the first limiting AA in all the legumes. In terms of pattern and profile of AAs, legume grain protein appears to be supplementary to cereal grain protein.  

There were differences among protein supplements in terms of g of AAs per 100 g of CP. Narbon vetch (98.7%) and pea seeds (95%) had similar values to that of soybean meal (96%). On the other hand, common vetch had the lowest (71%); the corresponding values for chickpea, cyprus vetch and field beans were 87.4, 83.1 and 82.4%, respectively.  The TP as percent of total CP ranged from 83 to 94%; chickpeas having the lowest (83%) and peas the highest (94%) value (Table 1).

Percent disappearances of CP obtained from nylon bags were fitted to the non-linear equation of Ørskov (1982) and estimated parameters are shown in Table 3. Predicted (at fractional outflow rate of 0.08 per hour) effective CP degradability in soybean meal was lower (P<0.05) than that of all legume seeds and that of sunflower meal. There were no differences in effective CP degradability between chickpeas, common  vetch, narbon vetch and peas. The effective degradability of chickpeas was lower (P<0.05) than that of common vetch, cyprus vetch and sunflower meal. Lower predicted effective CP degradability in solvent extracted soybean meal than leguminous seeds has also been reported by Dixon and Hosking (1992).  Higher effective CP degradability in chickpeas and narbon vetch grain than soybean meal have been reported by Illg et al (1987) and Hadjipanayiotou (2000), respectively. This difference in degradability can be associated to the fact that in both studies soybean meal was the result of solvent extraction of soybeans.