Proximate analysis and in-vitro gas production of predominant forages in Afe Babalola University rangeland as feed resources for ruminant production

In Nigeria, the major feed resource for ruminant production is the natural grazeland. However, most forage found on such lands cannot absolutely support ruminant production. Therefore, there is need to ascertain the nutritive values of predominant forages in Afe Babalola University before setting up a ruminant farm. Wet season forages: grasses, legumes, forbes and tresses were sampled and analysed for proximate composition and in-vitro gas production using standard techniques. It was found that crude protein ranged between 12.2 and 27.3% in Terminalia catappa and Leucaena leucocephala respectively. The ash content varied from 6.0-22.0% in Andropogon gayanus and Asclepias Syriaca respectively. Crude fibre of the forages was between 12.5 and 28.0% in L. leucocephala and Centrosema pubescens respectively. Gas production was measured for 24hrs at 3hr intervals. At mid-fermentation, gas production ranged between 4.0 and 13.3ml/200mgDM (T. catappa and A. Syriaca respectively). While at termination, it was from 9.0 - 22.67ml/200mgDM in T. catappa and A. Syriaca respectively. Significant differences (P


INTRODUCTION
Low productivity of ruminant livestock is mainly hinged on poor quality forage and its unavailability in quantity. The major resources for ruminants are cereal crop residues and pastures from rangelands. Livestock graze on about 26% of the world's land area. Tchinda et al. (1993) reported that native pastures are the most widely available low cost feeds for ruminants in the tropics. Native rangelands offer the cheapest source of nutrients for the ruminants. It is however an accepted fact that for a greater part of the year, grasslands in the tropics do not supply sufficient nutrients to stocks for actualizing enhanced productivity. Forage digestibility is related to intake rate, and affects animal performance positively. In addition, leafy swards provide more suitable intake conditions in view of the characteristics of animal ingestive behavior (Benvenutti et al., 2008). In Nigeria, ruminants slowly gain weight in the rainy season and rapidly loose it in the dry season, yet in the traditional animal husbandry, ruminants are mainly fed with grasses, so that improved livestock production is not likely attainable and sustainable by forage grasses alone (Babayemi and Bamikole, 2006). Babayemi et al., (2003) had earlier reported that the forages are unimproved and low in nutritive values during the wet season, while during the dry season proper, they are fibrous, lignified with low protein values and even in short supply. Lamidi et al. (2010) agreed with this by reporting that available forages for most part of the year are low in protein content which leads to marked decrease in voluntary intake and digestibility, and subsequently leads to substantial weight loss of the animals during this period. The success of the livestock industry anywhere in the world depends greatly on feed quantity and quality. However, the expensive nature of conventional feed as a result of competition between man In-vitro fermentation procedures Preparation of the buffer and rumen liquor was carried out as described by Menke and Steingass (1988). The substrate was placed in calibrated gas tight plastic syringes fitted with a piston. The syringes were put in an incubator at 39±1ᴼC. Rumen liquor was collected from three female West African Dwarf (WAD) goats, sieved with a four layered cheese cloth and mixed with a sodium buffer (9.8g NaHCO3 + 2.77g (Na)2HPO4 + 0.57g KCl + 0.47gNaCl + 0.12gMgSO4 7H2O + CaCl2. H2O per 1000ml) in a ratio1:2 v/v. 200mg DM of each sample with 30ml of rumen liquor and buffer were placed in each syringe and incubated in triplicate under continuous flushing with CO2. A blank (rumen liquor + buffer) without substrate was incubated at the same time. The reading of the blank was subtracted from that of the other syringes. Gas production was recorded at 3, 6, 9, 12, 15, 18, 21 and 24h. After 24h of incubation, 4ml of NaOH (10M) was introduced into inoculums as reported by Fievez et al. (2005) to estimate the amount of methane produced. The value of gas produced at intervals was plotted against the using the equation Y= a + b (1-ect) (Ørskov and Mc Donald, 1979), where Y= volume of gas produced at time t, a= initial gas produced, b= gas produced from insoluble but degradable fraction, c = the rate constant for the degradation of 'b' and t= incubation time.

Statistical Analysis
Data collected were subjected to analysis of variance at p=0.05.

III.
RESULTS AND DISCUSSION Proximate composition of predominant forages in Afe Babalola University rangeland Shown in Table 1 is the proximate composition of predominant forages in Afe Babalola University. The crude protein for the present study varied from 12.2-27.3% in T. catappa and L. leucocephala respectively. The ash content also varied from 6-22% in A. gayanus and A. syriaca respectively. Crude fibre of the forages was between 12.5 and 28.0% in L. leucocephala and C. pubescens respectively. The ether extract ranged from 2.0 -9.5% (A. gayanus and T. catappa respectively), while the Nitrogen free extract of the forages was observed to vary from 30.5 -53.7% in A. syriaca and A. gayanus respectively. It was noted that there were significant differences (P˂ 0.05) in all the measured parameters among the forages.   The CP of the forage species ranged from 12.2 to 27.3%, which is above the 7% CP requirement for ruminants which will provide ammonia required by rumen microorganisms to support optimum microbial activity. Andropogom gayanus had a higher CP of 13.7% compared to Odedire and Babayemi (2008) CP: 9.36% the ether extract and ash had lower values to that reported by the same authors. The ash content (8%) of Panicum maximum noted in this study was different and lower to the findings of Odedire and Babayemi (2008) however, the CP (13.6) was higher than that reported by the same authors. Amata and Lebari, (2011) reported crude protein of 11.70% in Terminalia catappa as against 12.2% noted in the present study. The workers however reported lower level of crude fibre and ash than reported in the present study. The values obtained for proximate composition of Calopogonium mucunoides were lower in terms of crude protein: 23.8% and Nitrogen free extract: 30.2% but higher in ash: 9.80%, crude fibre: 28.0% and ether extract:8.0% compared to what Mecha and Adegbola (1980) reported; ash (9.80%), crude fibre (21.60%), ether extract(3.10%) crude protein (24.08) and Nitrogen free extract (41.42).

International Journal of Environment, Agriculture and Biotechnology (IJEAB)
The nutrient composition of Centrosema pubescens as obtained in this present study differs from that of Nworgu and Egbunike, 2013 who obtained 9.14% (ash) which is considered higher than the present study ash: 7.0%, crude protein 23.4% was also found higher than crude protein 18.7% of the present study. However, lower values for crude fibre: 8.80 and ether extract: 3.32% compared to that of the present study: crude fibre: 17.7% and ether extract: 9.5% were observed. Generally, the variation that existed between the present study and the past works on the forages considered may be traced to time and seasons of harvest, age of plant, leaf to petiole ratio, ecological location and edaphic (soil) (Makkar and Beacker, 1997; Babayemi and Bamikole, 2006). In-vitro gas production of forages collected from the rangeland in Afe Babalola University. Presented in Figure 1 is the in-vitro gas production of forages from the rangeland in Afe Babalola University. At the onset of fermentation, gas production ranged from 0.00ml/200mg DM in C. mucunoides, P. maximum, T. procumbens, C. pubescens, A. gayanus and T. catappa to 2.33ml/200mg DM in L. leucocephala. However at mid fermentation, it ranged from 4.00ml/200mg DM (T. catappa) to 13.33ml/200mg DM (A. syriaca), while at termination, the gas production ranged from 9.00ml/200mg DM to 22.67ml/200mg DM in T. catappa and A. syriaca respectively. Gas production varied significantly (P˂ 0.05) in the forages from the 3 rd hour to termination at 24 th hour in the present study.  Table 2 is the Metabolisable energy MJ/Kg DM, organic matter digestibility (%) and short chain fatty acid (µmol) of predominant forages in Afe Babalola University. ME is an indication of energy and it ranged between 5.00 and 6.50 MJ/Kg DM (Tridax procumbens and Asclepias syriaca respectively). It was found to be significantly different among forages. Organic matter digestibility ranged from 37.7-58.54% in Tridax procumbens and Asclepias syriaca respectively with significant difference among forages. Short chain fatty acid which is an indication of energy made available to the host animal ranged from 0.27-0.60 µmol (Terminalia catappa and Asclepias syriaca respectively).   /dx.doi.org/10.22161/ijeab/2.4.42  ISSN: 2456-1878 www.ijeab.com Page | 1799 Norton (2003) justifies the use of forages in small quantities in order to supplement poor quality pastures and crop residues. It has been suggested that the gas production technique is more reliable than the nylon bag method for determining nutritive value of feeds containing antinutritive factors (Khazaal et al., 1993). Nature and fibre levels, presence of anti-nutrition factor had been reported to influence the amount of gas produced during fermentation (Babayemi 2004). High level of crude fibre reduce digestibility which is synonymous to in-vitro gas production. In-vitro technique is a more reliable tool for evaluating ruminant forages. Though the two methods are independent of each other, they are interrelated (Babayemi et al., 2004;Fievez et al., 2005).

International Journal of Environment, Agriculture and Biotechnology (IJEAB)
Gas production is associated with volatile fatty acid production following fermentation of substrate (Blummel and Ørskov 1993). In addition, the application of models permits the fermentation kinetics of the soluble and readily degradable fraction of the feeds, and more slowly degradable fraction to be described (Gatechew et al., 1998). Moreover the gas production parameters of trees might demonstrate differences in their nutritional value that may be closely related to their chemical composition (Cerrillo and Juarez 2004). The inconsistency observed in the gas production is as a result of the different rate of different anti nutritional content as well as the forage degradability. In-vitro estimations of feed degradation are important tools for ruminant nutritionists. These methods measure either substrate disappearance or fermentation products (Blümmel et al 1997). In the present study, forages with high CP produced higher gas volume. Digestibility has been reported to be synonymous to in vitro gas production (Fievez et al., 2005) that is, forages with high gas production will exhibit better digestibility.
In-vitro gas production characteristics of predominant forages in Afe Babalola University rangeland Presented in Table 3 is the in-vitro gas production characteristic of predominant forages in Afe Babalola University. It was observed that 'a' which is the initial gas produced ranged between 1.67 and 3.67 ml in T. procumbens, A. gayanus, T. catappa and C. pubescens respectively. Significant differences existed among the considered forages (P˂ 0.05). The potential gas production from insoluble but degradable fraction 'b' varied from 7.33-20.65 ml T. catappa and Asclepias syriaca respectively, while the rate of potential gas production (a+b) ranged from 9.00-22.67 ml in T. catappa and Asclepias syriaca respectively. Rate at which gas is produced 'c' ranged from 0.032-0.059(ml/h) in Andropogom gayanus and Calopogonium mucunoides respectively with no significant differences among the forages. a,b,c,d = Means on the same column with similar subscript letters are not significantly different(P˂ 0.05). a-initial gas produced/intercept, b-insoluble but degradable fraction, a + b-potential extent of gas production, c-rate at which gas is produced, Y-gas volume, SEM = Standard error of means.
The intake of a feed is mostly explained by the rate of gas production (c) which affects the passage rate of feed through the rumen, whereas the potential gas production (a +b), is associated with degradability of feed (Khazaal et al., 1995). Therefore the higher values obtained for the potential gas production in the Calopogonium mucunoides, Leucaena leucocephala and Asclepias spp might indicate a better nutrient availability for rumen microorganisms.

Methane gas (mmol) produced at 24 h of incubating predominant forages in Afe Babalola University
Presented in Figure 2 is the methane gas (mmol) produced from incubating predominant forages in Afe Babalola University. The methane gas ranged from 3.33-5.67mmol in Terminalia catappa and Calopogonium mucunoides respectively.