Nutritive Value of Stipagrostis lanata (Forssk.) De Winder as a Feed for Livestock

MATERIALS AND METHODS

Plant material: S. lanata plants were collected at flowering stage in July 2011 from their natural habitats in the Nile Delta coastal region of Kafr El-Sheikh Governorate, Egypt. The plant was identified by the Department of Agricultural Botany, Faculty of Agriculture, Tanta University. The voucher specimen was deposited at Laboratory of the same Department. Physical and chemical characters (Ryan et al., 1996) of the soil where S. lanata plants were collected at a depth of 0 to 50 cm are shown in Table 1.

Sample preparation: Aboveground parts of S. lanata were separated, cut into small pieces and air dried. The dried materials were powdered and kept in the refrigerator until use.

Proximate analysis: Moisture content (MC), crude fiber (CF), ether extract (EE), total nitrogen (Kjeldahl method) and ash content (AC) were determine by using the standard procedures of AOAC (1990). Crude protein (CP) % in DM was calculated by multiplying total nitrogen by 6.25. Total carbohydrates (TC) % in DM = 100-(CP+EE+AC), while digestible carbohydrate (DC) also known as Nitrogen Free Extract (NFE) % in DM = TC-CF. Digestible Crude Protein (DCP) was calculated according to the equation of Shaltout et al. (2009): DCP (% in DM) = 0.929 CP-3.52.

Energy measurements: The prediction of the energy value of the aboveground parts of S. lanata as a feed material was estimated by using equations based on its chemical composition (Shaltout et al., 2008) as follows: Total Digestible Nutrients (TDN) were estimated according to the equation: TDN (% in DM) = 0.62 (100+1.25 EE)–0.72 CP. Nutritive value (NV) was calculated as: NV (% in DM) = TDN/CP. Digestible energy (DE) was estimated following this equation: DE (Mcal kg^-1 DM) = 0.0504 CP+0.077 EE+0.02 CF+0.000377 NFE²+0.011 NFE-0.152.

Table 1:	Physical and chemical characters of the soil where S. lanata plants were collected
Values are Mean±SE of 3 replications

Metabolized energy (ME) as Mcal kg^-1 = 0.82 DE and net energy (NE) was estimated as follows: NE (MJ kg^-1 DM) = [(3.65 TDN (%)–100)/188.3]x6.9. Nutritional ratio (NR) was calculated as: NR = DCP (g kg^-1 DM)/NE (FU kg^-1 DM), where FU: food unit and one FU = 6.9 MJ = 1650 kcal. Gross energy (GE) was calculated as follows: GE (kcal g/DM) = DC (4.15)+CP (5.65)+CF (4.25)+EE (9.0). Caloric value (CV) was calculated using the equation of Onyeike et al. (1995): CV (kcal/100 g DM) = (4 CP+9 EE+4 DC).

Anti nutritional factors: The anti-nutritional factors such as alkaloids, saponins, cyanogenic glycosides, flavonoids, total and simple phenolics and tannins were estimated. Alkaloids, saponins and cyanogenic glycosides were measured following the procedures described by Clarke (1970), AOAC (1990) and Haque and Bradbury (2002), respectively. Total flavonoids were determined by the method of Zhishen et al. (1999). Total phenolics, simple phenolics (non-tannin phenolics) and tannins were determined according to Makkar et al. (2007). Amount of tannins was calculated by difference using the following formula:

Statistical analysis: Values of proximate analysis and predicted energy are means of four replications±SE, while values of soil analysis and anti-nutritional factors are means of three replications±SE. Values of standard error (SE) were calculated using Microsoft Office Excel 2007.

RESULTS

Grasses are great source as forage for livestock and dairy production (Ashraf, 2006). From this view, nutritional value of the aboveground parts of S. lanata as a forage for livestock was evaluated in this study. High values of nutrients have been found in S. lanata aboveground parts (Table 2). Dry matter, ash content, crude protein, ether extract, crude fiber, total carbohydrates, digestible carbohydrates and digestible crude protein were 54.63±0.39%, 7.24±0.15%, 8.21±0.16%, 3.96±0.20%, 33.17±0.53%, 80.59±0.23%, 47.42±0.63% and 4.11±0.15% in DM, respectively.

Total digestible nutrients, nutritive value, digestible energy, metabolized energy, net energy, nutritional ratio, gross energy and caloric value accounted for 59.16±0.22% DM, 7.21±0.16% DM, 2.61±0.01 Mcal kg^-1 DM, 2.14±0.01 Mcal kg^-1 DM, 4.25±0.03 MJ kg^-1 DM, 66.73±2.74 g Fu^-1, 419.79±1.22 kcal/100 g DM and 258.2±1.66 kcal/100 g DM, respectively (Table 3).

Table 2:	Proximate analysis of the aboveground parts of S. lanata measured as percentage of DM
Values are Mean±SE of 4 replications

Table 3:	Predicted energy value of the aboveground parts of S. lanata as a feed material
Values are Mean±SE of 4 replications

Table 4:	Contents of anti nutritional factors in the aboveground parts of S. lanata
Values are Mean±SE of 3 replications

Additionally, contents of total flavonoids, total phenolics, tannins, simple phenolics, alkaloids, saponins and cyanogenic glycosides were 0.036±0.002% DM, 0.46±0.02% DM, 0.29±0.01% DM, 0.17±0.02% DM, 0.97±0.12 % DM, 2.9±0.18% DM and 2.13±0.16 mg/100 g DM, respectively (Table 4).

DISCUSSION

The nutritional value of any forage depends largely on its contents of nutrients and energy value as well as the presence of anti-nutritional factors. Proximate composition of aboveground parts of S. lanata revealed that those parts contained high concentrations of the principal nutrients including minerals (ash), proteins, carbohydrates and lipids. Concentrations of protein, carbohydrates and ether extracts in any forage plant are important factors that determine its use for feed formulation, as they are responsible for caloric value of the plant (Hassan et al., 2007). High amounts of crude protein, total carbohydrates and ether extract in the aboveground parts of S. lanata indicate its high nutritive value. Moreover, the plant is considered as a highly fibrous according to its high level of crude fiber that may be due to the environmental conditions (Boufennara et al., 2012) prevailing in the Nile Delta coastal region of Egypt where the plant grows.

Nehring and Haenlein (1973) stated that gross energy (GE), digestible energy (DE), metabolized energy (ME) and net energy (NE) are the most important categories used in determination of energy value of animal feed. In this study, S. lanata aboveground parts showed high-energy value represented by high amounts of GE, DE, ME and NE.

Nutritional value of a feed depends on the balance between nutritional and anti-nutritional compounds found in this feed (Aberoumand, 2009). Anti-nutritional factors include flavonoids, phenolics, alkaloids, saponins, tannins, oxalates, phytates and cyanogenic glycosides and others (Akande et al., 2010). They inhibit digestive enzymes, bind to proteins reducing the palatability and absorption of nutrients of the feed, and hence cause growth depression (Phale and Madibela, 2006; Sarkiyayi and Agar, 2010; Gwanzura et al., 2012; Gayathri et al., 2012). In addition to its adverse effects, anti-nutritional factors also have some beneficial applications in pharmaceutical, agricultural and food industries (Soetan, 2008). In this study, the results indicate that aboveground parts of S. lanata contain relatively high levels of anti-nutrients. This may be due to that this plant grows in very warm and harsh environments (Ghasemkhani et al., 2008); therefore, these biochemical features support its adaptation and growth in arid and semi-arid environments such as sand dunes. Anti-nutritional factors were proved to play an important role in plant defense mechanisms against pathogens, herbivores and environmental stress (Gwanzura et al., 2012).

Even though the soil where S. lanata grows was poor, it is obvious that S. lanata is of great value as a fodder and its aboveground parts have a tendency to accumulate high concentrations of nutrients and high-energy elements. As environmental factors including soil and climate conditions affect the chemical composition of a plant, it is possible that increasing soil nutrients can enhance the nutritional quality of forage plants (Fateh et al., 2009; Ingweye et al., 2010; Zulfiqar and Asim, 2002).

CONCLUSION

Grasses are widely used in animal nutrition due to their high contents of nutrients. The present study describes the nutritional value of the aboveground parts of Stipagrostis lanata, a wild grass growing in Egypt. The results revealed that those parts are a rich source of nutrients and have high-energy value. Therefore, our study recommends this plant to be planted and utilized on a wide range as a feed for livestock. However, further toxicological studies are needed to assess the possibility of utilization of this plant in animal diet and for feed formulations.