Introduction

In tropical countries where livestock production is mainly based on grass-dominated pastures, herbage mass during the dry season is generally not sufficient to satisfy the nutritional requirements of livestock because of the low yield and quality which drastically decline. Due to this, the performance of the animals is been affected losing about 20% of their body weight (Lamidi & Ologbose, 2014) leading to low in productivity of the animals. Nutritive contents of forages are high when they are still young while they reduced as they mature. In order to alleviate the problem of feed scarcity and to maintain their quality it becomes imperative to conserve the forages so as to meet the nutrient requirements of animals all year round. Sahoo (2018) described silage production in the tropics as a sustainable means of supplementing feed for ruminants in the dry season due to the fact that the production of silage is not dependent on weather conditions compared to hay making. The production of silage from tropical grasses is valuable because of its relatively lower production cost for animals (Wilkins, 2019).

However, grasses in the tropics grow and mature earlier than the ones from temperate region with the same age due to high temperature regime. This lead to fall in nutrients and digestibility because of the early growth and aging of the plants (Ojo et al., 2016). Babayemi and Igbekoyi (2008) therefore reported that silages made from grasses that have become lignified are poor in nutrients because of the low protein content. In other to utilize these grasses as livestock feeds, increasing the nutrient density with a rich protein source as supplement will improve fermentation and the nutritive value of the silages (Ojo et al., 2018).

Browse seeds have been reported to be high in CP and serve as potential feed for ruminants (Idowu et al., 2013). However, they contain secondary metabolites which limits their utilization by ruminants but are reduced to some extent without detrimental effect on the animals if they are been processed and conserved (Oyaniran, Ojo, Aderinboye, Bakare, & Olanite, 2018).

The silage quality is usually influenced by the stage of maturity and use of additives (Oliveira et al., 2020) and their changes are reflected by their chemical composition. The chemical composition of silage produced, depends largely on stage of growth of the harvested plants as well as the changes from activities of plants enzymes during the storage periods (Souza et al., 2022).

For this study, we therefore hypothesize that the low quality of tropical grasses at advanced stage can be improved by conservation with inclusion of browse seeds. Hence

this study is to evaluate the effects of phenological stages and ensiling length on chemical composition of M. maximus ensiled with M. oleifera seeds at different proportions.

Material and methods

Location and climate of the study area

The study was conducted at the Federal University of Agriculture Abeokuta (FUNAAB) Nigeria, West Africa, located 76 m above sea level and falls within latitude 7° 15′ north and longitude 3° 21′ east with average annual rainfall of 1037 mm. Mean annual temperature and humidity are 34.0°C and 82%, respectively.

Collection of samples and procedure of silage making

The matured pods of M. oleifera were harvested using a tree-pruning pole attached with a sickle at the end. The collected pods were sun-cured for three days, and the seeds were extracted by manually opening the pods. The seeds of all the plants were further sundried for three days and ground using hammer mill to pass through3 mm sieve. Megathyrsus maximus grass were harvested at vegetative (8 WAP) and early reproductive (11 WAP) stages which were planted at spacing of 0.5 × 0.5 m and fertilized approximately with 150 kg N ha^-1 of poultry manure. The grasses were chopped to about 2 cm long, wilted for 2 hours and were mixed uniformly with the tree seeds at different proportions (100% grass: 0% Moringa seeds, 75% grass: 25% Moringa seeds and 50% grass: 50% Moringa seeds). They were then packed according to the treatment into well labeled laboratory glass jar bottle silos of 960 mL, compressed and compacted to ensure anaerobic conditions. They were then stored for 30, 60, 90 and 120 days on the laboratory tables. The treatments were replicated 3 times.

Experimental design

The study was 2 × 3 × 4 factorial experiment. The factors were two phenological stages (vegetative and reproductive stages), three proportions of the grass and tree seeds (100:0, 75:25 and 50:50) and four ensiling length (30,60, 90 and 120 days).

Chemical analyses of ensiled forages

Sub samples of each silage at different ensiling length were oven dried at 65^oC to a constant weight and milled to pass through 1 mm sieve. Proximate composition (dry matter, crude protein, ether extract and ash) were determined according to Association of Official Analytical Chemists (AOAC, 2000), non-fibre carbohydrate (NFC g kg^-1) was calculated as: 1000 - NDF - CP - EE - Ash. Neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) was carried out according to the procedure of Van Soest, Robertson, and Lewis (1991). Concentrations of minerals, calcium (Ca), potassium(K), phosphorus (P) and magnesium (Mg), in the silages were determined using atomic absorption spectrophotometer (Buck Scientific, East Norwalk, CT, USA) after wet digestion with concentrated sulphuric acid according to AOAC (2000).

Tannin content of the milled tree seeds was determined using the Vanillin-HCl method as described by Price and Betler (1977). Saponin content was determined according to the methods of Obadoni and Ochuko (2001).

Statistical analysis

All data obtained were subjected to three-way analysis of variance (ANOVA). Treatment means were separated using Turkey's HSD test. All data were analyzed using the R Statistical Software (R Core Team, 2020). Significance difference were tested at 5% probability level.

Results and discussion

Table 1 shows the effect of phenological stages, proportion and ensiling length on the proximate composition of M. maximus ensiled with M. oleifera seeds. The values of dry matter content reduced from 90 to 120 days of ensiling at different proportion and phenological stages with the lowest value recorded for sole M. maximus silage at vegetative stage and ensiled for 120 days (859.36 g kg^-1). The highest value of CP content (152.98 g kg^-1) was recorded for 50% M. oleifera seed silage at vegetative stage ensiled for 30 days while the least were significantly lower (P < 0.05) in sole M. maximus silage at both phenological stages ensiled for 120 days (70.38 and 63.99 g kg^-1) and also sole M. maximus silage at reproductive stage ensiled for 90 days (68.82 g kg^-1). The result showed an increasing trend in CP and EE contents as the proportion of the seed in the silage increased at both phenological stages. This might be due to higher CP and EE in the seeds. In a similar trend, Ojo et al. (2018) reported that the CP increased with increasing level of treated E. cyclocarpum seeds ensiled with P. purpureum. The CP content also declined with prolonged ensiling length at both phenological stages. This was similar with findings of Okukenu et al. (2018) for M. maximus ensiled with C. molle at different proportion and storage duration. This could be as a result of proteolytic activities and the breaking down of the nutrients by the microbes during the fermentation. Sarıçiçek, Yıldırım, Kocabaş, and Demir (2016) evaluated changes in the quality of maize silage stored for different duration, and found out that extended duration of ensiling decreased dry matter and crude protein contents as storage advanced. The authors reported that as the ensiling period progressed from 90 - 202 days, CP content declined from 89.5 to 65.4 g kg^-1. The values of CP and ash contents at the vegetative stage for each silage with different proportions were higher than that of reproductive stage. This might be due to the dilution of CP content by an increased in amount of structural carbohydrates as the plants matured (Agza, Kassa, Zewdu, Aklilu, & Alemu, 2013). The CP recorded for the silages were above 60 g kg^-1 required by rumen microbes to build their protein body in which the feed intake of ruminants and rumen microbial activity would be affected if it falls below this threshold (Van Soest, 1994). The ash content obtained in this study was higher than the means of 40.5 g kg^-1 reported by Okukenu et al. (2018). This might be due to age at harvest and status of the soil. The deficiency of some minerals in the soil have been reported to reduce the ash content in the plants (Oguntona, 1998). Tilahun, Asmare, and Mekuriaw (2017) also reported that as the plant matures the ash content reduces.

Effect of phenological stages, proportion and ensiling length on fibre fraction of silage is shown on Table 2. Sole M. maximus silage at reproductive stage and ensiled for 120 days had the highest value of ADF content (385.64 g kg^-1). The NDF and hemicellulose contents decline as the proportion of seed in silage decreased with prolonged ensiling length at both phenological stages. This is in line with the findings of Dele et al. (2013) on silage produced from Guinea grass and agro by-product as affected by storage duration. This could be attributed to rate of degradation of fibre content by bacteria during fermentation with prolonged ensiling length (Yahaya et al., 2001). The values of NDF and hemicellulose contents ranged from 445.75 - 691.65 and 110.91 - 382.78 g kg^-1 respectively with the highest recorded for sole M. maximus silage at reproductive stage at 30 days and least recorded for 50 % M. oleifera seed silage at vegetative stage at 120 days of ensiling. The NDF content of sole M. maximus ensiled for 30 and 60 days was slightly higher than 628.2 g kg^-1 reported by Ekanem, Olorunnisomo, and Matthew (2019) for sole M. maximus silage and also higher than the range of 318.80 - 424.40, 603.1 g kg^-1 for P. purpureum ensiled with treated E. cyclocarpum seeds at different proportion (Ojo et al., 2018). This variation could be due to age at harvest. However, the NDF contents of the silage in this study were at level that can be easily degradable which is below 70% if fed to animals (Turgut, Yanar, Tuzemen, Tan, & Comakli, 2008). The ADF values obtained in this study were within the range of 220-500 g kg^-1 reported for forage plants (Slater, 1991). The ADL content also decreased as the proportion of seed in silage decreased at both phenological stages.

Effects of phenological stages, proportion and ensiling length on the mineral composition and anti-nutritional factor of M. maximus ensiled with M. oleifera seed is presented in Table 3. The values of Ca and P contents ranged from 3.05 - 8.06 and 1.64 - 6.92 g kg^-1 respectively with lowest value in sole M. maximus silage at reproductive stage ensiled at 90 days and highest obtained in 25% M. oleifera seed silage at vegetative stage ensiled at 30 days. Lowest value of K content was obtained in 50% M. oleifera seed silage at vegetative stage ensiled for 30 days (11.91 g kg^-1). Calcium and P contents recorded for sole M. maximus silage in this study were lower than 7.02 and 2.44 g kg^-1 respectively reported by Ojo et al. (2016) for M. maximus ensiled for 42 days. The difference could be due to mineral contents in the soil that was available for uptake by plant. Calcium and P contents observed in this study were higher than the range of 2 - 6 g kg^-1 and 0.18-0.48% respectively required for ruminants (Dele et al., 2018). Potassium content was above 0.8% recommended for grazing animals (Dele et al., 2018).

The silage with 50% M. oleifera seed at reproductive stage ensiled for 30 days (4.15 g kg^-1) had the highest value of tannin content while the highest value of saponin content was recorded for 50% M. oleifera seed at vegetative stage ensiled for 30 days. The tannin and saponin contents increased as the proportion of the seed in the silage increased at both phenological stages while they decreased with increased ensiling period. This might be due to heat produced during the ensiling process which is normal in relation to silage temperature even in a well-managed silo (Adesogan & Newman, 2014). Production of heat during the process of conservation might have been responsible for the reduction in tannin and saponin contents as the ensiling period increased.

Conclusion

It can be concluded from this study that silages made from both phenological stages containing M. oleifera seeds improved CP, EE and ash contents and also reduced the NDF, tannin and saponin contents as the ensiling length prolonged. This shows that the higher yield of grass at reproductive stage can be ensiled and enhanced with browse seeds for animal consumption especially during the dry season when high quality is rare for animals.

References

Adesogan, A. T., & Newman, Y. C. (2014). Silage harvesting, storing, and feeding. Gainesville, FL: University of Florida.

Agza, B., Kassa, B., Zewdu, S., Aklilu, E., & Alemu, F. (2013). Forage yield and nutritive value of natural pastures at varying levels of maturity in North West Lowlands of Ethiopia. World Journal of Agricultural Sciences, 1(3), 106-112.

Association of Official Analytical Chemist [AOAC]. (2000). Official methods of analysis (17th ed.). Gaithersburg, MD: AOAC.

Babayemi, O. J., & Igbekoyi, A. J. (2008). Ensiling pasture grass with pods of browse plants is potential to solving dry season feed shortage for ruminants in Nigeria. In Competition for Resources in a Changing World: New Drive for Rural Development (p. 1-4). Hohenheim, GE: Tropentag.

Dele, P. A., Jolaosho, A. O., Arigbede, O. M., Ojo, V. O. A., Amole, T. A., Okukenu, O. A., & Akinyemi, B. T. (2013). Chemical composition and in vitro gas production of silage from guinea grass, cassava peel and cashew apple waste at different periods of ensilage. Pakistan Journal of Biological Science, 16(23), 1801-1805. DOI: https://doi.org/10.3923/pjbs.2013.1801.1805

Dele, P., Akinyemi, B., Okukenu, O., Amole, T., Akinlolu, A., Sarumi, G., … Anotaenwere, C. (2018). Chemical composition of Panicum maximum as influenced by poultry manure rate and age at harvest. The Pacific Journal of Science and Technology, 19(2), 319-325.

Ekanem, N. J., Olorunnisomo, O. A., & Matthew, A. I. (2019). Physical characteristics and chemical composition of Panicum maximum ensiled with brewers’ spent grains for different periods. Journal of Agricultural Production and Technology, 8, 10-18.

Idowu, O. J., Arigbede, O. M., Dele, P. A., Olanite, J. A., Adelusi, O. O., Ojo., V. O. A., & Sunmola, A. S. (2013). Nutrients intake, performance and nitrogen balance of West African dwarf sheep fed graded levels of Enterolobium cyclocarpum seeds as supplement to Panicum maximum. Pakistan Journal of Biological Sciences, 16(23), 1806-1810. DOI: https://doi.org/10.3923/pjbs.2013.1806.1810

Lamidi, A. A., & Ologbose, F. I. (2014). Dry season feeds and feeding: a treat to sustainable ruminant production in Nigeria. Journal of Agriculture and Social Research, 14(1), 17-30.

Obadoni, B. O., & Ochuko, P. O. (2002). Phytochemical studies and comparative efficacy of the crude extracts of some haemostatic plants in Edo and Delta states of Nigeria. Global Journal of Pure and Applied Sciences, 8(2), 203-208. DOI: https://doi.org/10.4314/gjpas.v8i2.16033

Oguntona, T. (1998). Green leafy vegetables in nutritional quality of plant foods. In A. U. Osagie, & O. U. Eka (Eds.),Nutritional quality of plant foods (p. 120-133). Benin City, NG: University of Benin.

Ojo, V. O. A., Adelusi, O. O., Jimoh, S. O., Yusuf, K. O., Dele, P. A., & Akinyemi, B. T. (2018). Effects of proportion and ensiling duration on nutrient digestibility and fermentation characteristics of Pennisetum purpureum and Enterolobium cyclocarpum seeds silage using invitro gas production technique. Bulletin of Animal Health and Production in Africa, 66(1), 163-175.

Ojo, V. O. A., Jolaosho, A. O., Onifade, O. S., Amodu, J. T., Olanite, J. A., Arigbede, O. M., … Amole, T. A. (2016). Dry matter yield, botanical and chemical composition of natural forages of the south western Nigeria as influenced by topography, land use and season. Journal of Animal Production Research, 28(1), 138-150.

Okukenu, O., Ogunrombi, O., Dele, P., Akinyemi, B., Olajide, A., Onifade, O., & Jolaosho, A. (2018). Proximate and fiber composition of Panicum maximum and Centrosema molle silage as affected by different proportions and ensiling periods. Pacific Journal of Science and Technology, 19(1), 264-269.

Oliveira, S. S., Costa, K. A. P., Souza, W. F., Santos, C. B., Teixeira, D. A. A., & Silva, V. C. (2020). Production and quality of the silage of sorghum intercropped with Paiaguas palisadegrass in different forage systems and at different maturity stages. Animal Production Science, 60(5), 694-704. DOI: https://doi.org/10.1071/AN17082

Oyaniran, D. K., Ojo, V. O. A., Aderinboye, R. Y., Bakare, B. A., & Olanite, J. A. (2018). Effect of pelleting on nutritive quality of forage legumes. Livestock Research for Rural Development, 30(4).

Price, M. L., & Butler, L. G. (1977). Rapid visual estimation and spectrophotometric determination of tannin content of sorghum grain. Journal of Agricultural and Food Chemistry, 25(6), 1268-1273. DOI: https://doi.org/10.1021/jf60214a034

R Core Team. (2020). R: A language and environment for statistical computing. Vienna, AT: R Foundation for Statistical Computing.

Sahoo, A. (2018). Silage for climate resilient small ruminant production. In M. Abubakar (Ed.), Ruminants - the husbandry, economic and health aspects (p. 11-39). London, UK: IntechOpen.

Sarıçiçek, B. T., Yıldırım, B., Kocabaş, Z., & Demir, E. O. (2016). Effect of storage time on nutrient composition and quality parameters of corn silage. Turkish Journal of Agriculture - Food Science and Technology, 4(11), 934-939. DOI: https://doi.org/10.24925/turjaf.v4i11.934-939.746

Slater, K. (1991). Principles of Dairy farming (11th ed.). Ipswich, GB: Diamond Farm Book Pubns.

Souza, A. M., Neumann, M., Rampim, L., Almeida, E. R., Matchula, A. F., Cristo, F. B., & Faria, M. V. (2022). Effect of storage time on the chemical composition of whole and grainless corn plant silage harvested at different maturity stages. Revista Brasileira de Zootecnia, 51, e20200180. DOI: https://doi.org/10.37496/rbz5120200180

Tilahun, G., Asmare, B., & Mekuriaw, Y. (2017). Effects of harvesting age and spacing on plant characteristics, chemical composition and yield of desho grass (Pennisetum pedicellatum) in the highlands of Ethiopia. Tropical Grasslands-ForrajesTropicales, 5(2), 77-84. DOI: https://doi.org/10.17138/TGFT(5)77-84

Turgut, L., Yanar, M., Tuzemen, N., Tan, M., & Comakli, B. (2008). Effects of maturity stage on chemical composition and in situ ruminal degradation kinetics of meadow hay in Awassi sheep. Journal of Animal and Veterinary Advances, 7(9), 1061-1065.

Van Soest, P. J. (1994). Nutritional ecology of the ruminant (2nd ed.). Corvalis, OR: Comstock Publishing Associates.

Van Soest, P. J., Robertson, J. B., & Lewis, B. A. (1991). Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science,74(10), 3583-3597. DOI: https://doi.org/10.3168/jds.S0022-0302(91)78551-2

Wilkins, R. J. (2019). Silage: a global perspective. In S. Reynoldsd (Ed.), Grasslands: developments opportunities perspectives (p. 111-132). Boca Raton, FL: CRC Press.

Yahaya, M. S., Kimura, A., Harai, J., Nguyen, H. V., Kawai, M., Takahashi, J., & Matsuoka, S. (2001). Effect of length of ensiling on silo degradation and digestibility of structural carbohydrates of lucerne and orchardgrass. Animal Feed Science and Technology, 92(3-4), 141-148. DOI: https://doi.org/10.1016/S0377-8401(01)00265-6

Author notes

* Author for correspondence. E-mail: oyanirandammy4real@yahoo.com