Chemical composition of Sesbania sesban and reed forage
The chemical composition of Sesbania sesban, Alfalfa, and reed plants differs due to differences in plant growth stage, cutting frequency, harvesting regimen, soil type, fertility status, parts of the plant (leaves, twigs, whole forage, and green pods) included during feeding, and environmental conditions in which the plant grows (Tekliye et al., 2018). The Sesban tree has high nitrogen content in its foliage and is a great protein supplement for roughage that is lacking in protein (Sabra et al., 2010; Manaye et al., 2009). This tree's leaves and branches provide significant levels of protein (ranging from 20 to 25 percent) that are easily digested by ruminants (Pravin et al., 2012). Sesbania sesban contain a high level of CP, indicating that it might be used to supplement protein in ruminant diets that were low or lacking in CP (Gebreyowhans and Zegeye, 2019). Reed grass had a moderate level of crude protein (12.25%), which was similar to that found (12.25%) by De la Cruz (1983). The higher percentage of fiber fractions (NDF and ADF) in reed forage than alfalfa and sesban may be due to its low CP content. Mahmoud et al. (2017) in a study, using some grass and legume, and other plants, found that the crude fiber and ether extract contents were high in the species that contained less protein and low in species with high protein content.
The chemical composition of sesban and reed forage in the present study was close to alfalfa or higher than it in some components. Hence, we can consider sesban and reed forage can be used as sources of protein and energy to feed lambs during the summer season. Moreover, the chemical compositions of sesbania sesban in our study are similar to those reported by ElKholany (2004), Zaki (2015), and El-Moghazy et al. (2017).
Dry matter intake, Nutrient digestibility and nutritive value of experimental rations
The lower intake in the reed plant group than in other forage groups may be due to higher fiber contents in reed plans and low nitrogen, both of which limited dry matter intake (DMI). Moreover, the higher NDF (57.26%) contents of the reed plant are always negatively correlated with DMI (Mokhtarpour and Jahantigh 2018). However, the improved forage intake of rams fed on Sesbania and alfalfa may be attributed to its lower NDF and ADF and higher CP with more palatable parts and thus increased DM intakes (Tekliye et al. 2018). Similar results of feed intake were observed with growing lambs (Farghaly et al., 2022).
The higher nutrient digestibility of all forage types could indicate the benefits of combining concentrates with fodder like Sesbania and reed plants, which had moderate tannin levels. Tannin levels in Sesbania and reed forages are modest, which may help to slow down the rate of degradation of concentrate feeds. Our findings are consistent with those of Mekoya et al. (2009) and Nsahlai et al. (1999), who found that a ration with a moderate tannin content or a combination of rapidly degradable concentrates and forage legumes with moderate tannin levels can provide adequate levels of both rumen degradable and by-pass protein to ruminants. Mekoya et al. (2009) reported that replacing concentrate mixture by Sesbania sesban at level 47.5 and 95% as a source of protein in lamb diets increased DM, OM and N digestibility. The higher protein contains in all forage in this study particularly alfalfa and Sesbania may improve the nutrient digestibility. These results coincide with that of McDonald et al. (2010) found that including dietary protein in the supplement enhanced protein availability to rumen bacteria, allowing the digestion process to be sped up. Tekliye et al. (2018) reported that supplementing Sesbania sesban leaves to ration enhanced significantly apparent nutritional digestibility. Zaki (2015) stated that the digestion coefficients were affected by different factors such as animal species, activities of rumen microbes, feed components, and associated effects. The improvement in nutrients digestibility due to the associative effect between feeds was approved by ElKholany (2004) when companies sesbania -corn in both forms fresh and silage than other treatments. Also, he attributed the improved digestibility of CP due to higher CP content in sesbania forage than corn plants in both forms fresh and silage as well as the differences in chemical nature of each protein of each forage.
It could be noticed that the nutrient digestibility of the reed forage group tended to be lower than the control and sesban groups. However, the digestibility of NDF and ADF were significantly (P< 0.05) higher than that of the control and sesban groups. The improvement in the digestibility of the structural carbohydrates of the reed forage group may be attributed to reducing the intake level which decreased the passage rate and exposed the feed to microbial attack for a long time (Fenner et al., 1966). Moreover, the higher protozoa count in the rumen liquor of the reed forage group (Table 4) may be participating in improving the digestibility of fiber fractions. McSweeney and Mackie (2012) reported that protozoa are responsible for 30–40% of overall fiber digestion under specific conditions. The same author also stated that protozoa are also involved in lipid hydrolysis and are thought to account for 30-40% of total ruminal activity. Previous studies have shown that the nutrients digestibility of fresh reed forage can be improved by ensiling it as a result of improved digestion of the plant cell wall components (Saeed and Al-Sultani, 2017; Hassan et al., 2009), or by adding yeast culture and urea during the ensiling process (Saeed, 2015; Saeed and Al-Sultani, 2017; Mokhtarpour and Jahantigh, 2018), which stimulates the rumen bacterial activity leading to increased ruminal digestion and improved DM, OM, CP, NDF, and ADF digestibility rates.
The higher DCP value of Alfalfa and Sesbania rations may be due to increasing nitrogen content in Alfalfa and Sesbania. Similar results have been reported by Zaki (2015) who attributed the improvement in the DCP value of ration-contained concentrate feed mixture with Sesbania due to an increased digestibility of CP. Jayanegara et al. (2010) found that the addition of S. sesban leaves to concentrate-based diets dramatically reduced in vitro CH4 generation, implying enhanced protein utilization. Also, the value of TDN is differing as a result of different chemical compositions and nutrient digestibility of rations. These results were confirmed by Ahmed et al. (2017) who found that the feeding value expressed as TDN and DCP was improved with feeding Sesbania Sesban and corn silage when compared with other treatments.
It could be observed that the nutritive value of the reed plant ration tended to be lower than other forage sources. Moreover, the feeding value of reed forage was varying according to the maturity phase and parts of the plant. Al-Sodany et al. (2012) stated that the nutritive value and content of nutrients of reed forage was better in younger plants than the older ones and in leaves than stems, which had a strong relationship with the digestibility of the plant. Furthermore, many previous studies approved that the nutritive value in terms of TDN and DCP of Sesbania sesban and reed forage can be improved by ensilage or ensilage with additive other forage plants (Shehata et al., 2006; Zaki, 2015; Ahmed et al., 2017; El-Moghazy et al., 2017).
Rams fed reed grass retained less nitrogen than rams fed alfalfa or sesbania. This could be attributed to lower nitrogen intake as a result of lower reed forage DM intake. However, the percentage of N-retained to N-intake or N-digested in the reed forage group was similar to that of the alfalfa and sesbania groups. The increased nitrogen retention in rams fed alfalfa and sesbania could be related to increased CP intake and digestibility, or it could be connected to improved rumen fermentation (Zaki, 2015).
Rumen liquor parameters:
It could be observed that the rumen pH tended to be lower with feeding alfalfa than in other groups. This is maybe due to an increase in TVFAʼs production in this group compared with other groups. These results agree with that reported by Zaki (2015) who stated that the pH values were affected by different factors such as drinking water, ruminal ammonia, and TVFAʼs. Similarly, ElKholany (2004) reported that the main reason for decreasing rumen PH is mainly due to the increase in TVFAʼs production in the rumen. El-Moghazy et al. (2017) found that the highest concentration of total TVFA occurred at 4 hours after feeding, which was revealed in a decrease in pH values at that time.
It could be noticed that the values of NH3 and TVFAʼs concentrations in rumen fluid decreased with feeding reed forage as compared with other groups, which may be attributed to its lower content of crude protein. ElKholany et al. (2018) found that the differences in rumen ammonia: N concentrations among treatments are correlated with differences in CP content in different roughage feeds. Moreover, Fenner et al. (1966) found that the rate and level of ammonia production were directly related to the solubility of the N- the source of the feed and the proportion of protein of the all-roughage ration. Also, the results showed that there was a significant effect of sampling times for all treatments on NH3 and TVFAʼs concentrations which reached to peak at 4 hours after feeding. This peak was noticed by Shehata et al. (2006) who found that the peak of pH values, NH3-N, and TVFA's ammonia concentrations appeared at 3 hrs post-feeding, these results were noticed when fed Zaraibi bucks reed forage in the form of silage or hay. Moreover, the reduction in the ammonia levels in the rumen at 8 hrs after feeding probably reflects the uptake of this nutrient by the rapidly growing microbial population (Losada et al., 1979). The significant effects among times for all treatments on NH3 and TVFAʼs may be related to the digestion of forages by microorganisms in rumen after feeding and absorption of them after that by rumen cell and used by microorganisms to produce micro-protein. This action is important for rumen nitrogen recycling and protein synthesis efficiency (McSweeney and Mackie, 2012).
The total protozoa count was decreased by about 24.6% of Sesbania group as compared with groups fed on alfalfa and reed forage. The results obtained are consistent with the findings of Newbold et al. (1997) who stated that sesbania sesban was toxic to rumen protozoa and that this was due to the saponin-containing component of the plant. The total protozoa count was increased at 4 hrs. after feeding than before feeding. These results were confirmed by Zaki (2015) when fed first and second cuts of sesbania sesban ad liptum. Similarly, Nhan (1998) found that the protozoa number of growing goats fed Sesbania grandiflora was 4.38 and 4.56 106/ ml for 0 and 4 hours after feeding, respectively. Aziz et al. (2018) reported that there was an increase in the protozoa number and improving in the rumen liquor parameters with the increase in roughage ratio in the diets.