Utilising Gliricidia sepium leaf meal as a protein substitute in cassava-based supplements to increase average daily gain of Ongole bulls and income of smallholder farmers

Keywords: concentrates, feed formulations, forage trees, least cost rations, profit, protein supplements, ruminant nutrition, supplements, tropical cattle.

Self-sufficiency in beef production is one of the goals of the Indonesian government program in 2026 (Sulaiman et al. 2018). Currently, Indonesian beef production is mostly supplied by smallholder farmers and is unable to meet domestic demands. There are approximately 16.4 million head of beef cattle across all of Indonesia, and 98% of the cattle population is raised by smallholder farmers (DGLS 2018). Smallholders can have quite efficient production systems, but cattle raised in smallholder farms often have low growth rates and poor feed conversions due to the lack of feed and/or poor diet formulations. Farmers offer forage to cattle usually based on availability without regard to meeting energy and protein requirements (Adiwinarti et al. 2011). The subsequent low farmer profitability can be addressed by better utilising available energy sources, such as dried cassava powder (DCP) or cassava pulp, and various protein sources, such as copra meal (CM), soybean hulls (SBH) or legume leaves.

The highest average daily gain (ADG0 reported for Ongole cattle in Indonesia is 1.3 kg/day; Mayberry et al. 2014). The protein concentrates from this experiment are too expensive for smallholder farmers (CM being 4876 Indonesian rupiah (IDR)/kg DM and SBH being 4614 IDR/kg DM). Therefore, it is important to evaluate other cheaper and more accessible sources of protein. Locally grown and processed Gliricidia leaf meal (GLM) as a protein source has the potential to be more profitable and adoptable for smallholder farmers.

In this study, GLM was used to replace CM or SBH in a concentrate based on cassava powder. GLM is processed from Gliricidia sepium leaves by drying and grinding similar to the process in making Leucaena leucocephala leaf meal (Gunawan and Gunardi 2000). Gliricidia sepium is a leguminous tree and the leaves are a good source of protein (approximately 18% crude protein (CP; Smith and van Houtert 1987). Fresh Gliricidia leaf is limited in use for cattle because of varying palatability issues (Smith and van Houtert 1987), and processing it into meal or pellets and mixing it with other local ingredients may be one way to improve its acceptance and use. Copra meal is a by-product of coconut oil extraction and has an appreciable CP of approximately 22% (Feedipedia 2012a). CM is also a potentially valuable source of energy due to its residual oil content. SBH is a by-product of the oil extraction process (Goehring et al. 2012), with a CP content of approximately 13% (Feedipedia 2016) and an appreciable digestibility value (77% total digestible nutrients; Negrão et al. 2020). There are few strategies to increase the metabolisable energy (ME) content of a concentrate mix in Indonesia, as grains are best used for humans and the poultry industry, and most by-products are not as high in ME as grains. Cassava tuber (whole or processed) provides one of the few opportunities in Indonesia, as it is widely grown and the agronomy is well established. However, farmers tend to purchase it rather than growing their own for cattle feed. There is an opportunity to combine cassava tuber with a high protein tree legume or protein meals to formulate a concentrate supplement that is cheap and readily accessible to farmers.

Dried cassava tuber has a high digestibility and ME value (approximately 12.2 MJ/kg DM) with a low protein content (approximately 2.9% CP; Feedipedia 2012b). Recent feeding trials have shown that cassava tuber inclusion should not exceed 40–50% of a ration for fattening bulls (Retnaningrum et al. 2021).

The objectives of this experiment were to determine the effect of substituting CM or SBH with GLM in a cassava-based concentrate supplement on the ADG of Ongole bulls, and whether this was a good strategy to increase the farmer’s income. The hypothesis of this experiment is that GLM can replace CM and SBH as a protein source in cassava-based concentrate supplements for beef cattle. It is also hypothesised that the use of GLM will increase the ADG of Ongole bulls with a lower feed cost, thus making it more profitable for smallholder farmers.

Forty Ongole bulls with an initial bodyweight of 199  ±41.1 kg and aged between 12 and 18 months were used in this village experiment. This is a typical weight of Ongole bulls in the smallholder system in Indonesia. Their weight is low, particularly for the frame size, so there is a large potential for improvement for ADG. The cattle were owned by a cooperative smallholder farmer group in Banaran and Bleberan villages. The two villages are located in Playen Subdistrict, Gunungkidul Regency, Special Region of Yogyakarta, Indonesia, and all treatments were allocated across both villages. All bulls received an identification number that was attached to a neck collar. All bulls were treated with macrocyclic lactone via an ivermectin subcutaneous injection (dose: 1 mL/50 kg liveweight (LW)) to control internal and external parasites prior to commencement of the experiment. This experiment was approved by the University of Queensland Animal Ethics Committee.

Bulls were randomly allocated into either a control group (R₀) or one of three treatments (R₁, R₂ and R₃), as shown in Table 1. Feed nutrient content of the current feeding system (CFS – R₀) and the concentrate diets of treatments can be seen in Table 2. The control group (R₀) was fed the CFS, whereas treatment groups were fed the CFS and dietary supplements at an approximate 1% LW/day on a DM basis. Each treatment involved 10 bulls (five bulls in Banaran and five bulls in Bleberan), so the total number of bulls (40) was used in this experiment. All treatments diets were allocated randomly in each village.

Table 1.  Dietary treatments.

Table 2.  Feed nutrient content of the current feeding system (R₀) and the concentrate supplements of treatments (R₁, R₂ and R₃).

Bulls were housed individually, and CFS was offered ad libitum to each animal in the morning and in the afternoon. The constituents of the CFS mainly consisted of native grass (Paspalum conjugatum, Cynodon dactylon), cultivated grass (Pennisetum purpureum), agricultural waste (corn stover, peanut straw) and tree leaf (Artocarpus heterophyllus, Albizia chinensis). GLM, CM, SBH and DCP were used in the concentrate in various proportions (Table 1) to make up the supplemented treatments. GLM was made by harvesting fresh G. sepium leaves at Wanagama forest and sun-dried for 12–48 h until a moisture content of approximately 15% was obtained. Dried Gliricidia leaves were then ground by local farmers at Banaran village and formed the GLM. CM, SBH and DCP were purchased from local traders. Each different concentrate was mixed as a mash prior to offering. There was a 2-week adaptation period to reach an estimated DM supplement level of 1% LW/day, which was adjusted based on LW measured every 3 weeks. A mineral block was provided to each animal in the feeding trough during the experiment.

At the start and every 3 weeks until the end of the trial, all bulls were weighed individually in the morning after food and water were removed at 22:00 hours the previous night. Average daily LW gain (kg) was calculated by regression of LWt during the experimental trial, using the initial LW as a covariate. These weights were used to calculate supplement level, which was based on LW. Individual feed intakes (FIwas observed daily by the farmers using individual spring scales and a whiteboard as a diary under the supervision of a technician. The amounts of feed offered and refused were monitored by a technician to ensure bulls had ad libitum access to sufficient CFS. Samples of CFS were taken and stored once every 3 weeks for DM analysis.

Samples of concentrates were collected in the first week and 12th week of the experiment for DM, ash, CP, ether extract (EE) and crude fibre (CF) analysis. Ether extract was determined by Method No 930.09 (AOAC 2005), CP by Method No. 978.04 (AOAC 2005) and CF determined by Method No. 930.10 (AOAC 2005). The amount of nitrogen-free extract (NFE) was calculated via the equation: % NFE = 100 − (% moisture + % EE + % ash + % CF + % CP). The concepts of CF and NFE are standard in animal feed analysis in Indonesia.

The feed to gain ratio (FFG) was the ratio of feed DM intake to ADG. Income over feed cost (IOFC) was obtained from the ADG multiplied by the price of the ADG (IDR/kg LW) minus the average daily feed costs of DMI (IDR/day), as previously reported by Cowley et al. (2020). The price of ADG was IDR 55.000/kg LW.

The experiment was a randomised complete design with four treatments and 10 animal replications. Data were analysed using analysis of covariance (ANCOVA), with the initial bodyweight of bulls as the covariate to control the effect of this variable to the dependent variable (Montgomery 2013). Least-squares means for each treatment were calculated, then continued with orthogonal contrast analysis to compare control (R₀) versus treatment (R₁, R₂ and R₃); without GLM (R₁) versus with GLM (R₂ and R₃); and R₂ (with GLM and SBH) versus R₃ (with GLM and CM).

The data analysis for forage intake, concentrate intake, total feed intake, ADG, FFG and IOFC was performed using the General Linear Model procedure in SAS (Statistical Analysis System) version 9.0.

The CFS intake of bulls maintained without concentrate (R₀) was not different to the CFS intake of bulls with treatment R₁, R₂ and R₃ (CFS + concentrate; P > 0.05), and ranged from 3.29 to 3.96 kg DM/head per day (Table 3). The concentrate intake of bulls with treatments R₁, R₂ and R₃ were not different (Table 3). As such, the total feed intake of bulls with concentrate supplementation (treatment R₁, R₂ and R₃) was significantly (P < 0.01) higher than bulls maintained under CFS (R₀) (Table 3). However, feed intake (% LW of bulls in control group (R0)) was not different to R₂, but lower than R₁ and R₃. The ADG of bulls supplemented with concentrates R₁, R₂ and R₃ was significantly (P < 0.01) higher than the control group (R₀; 0.31 for the control group compared with 0.60–0.75 kg/head for supplemented groups; Table 3). The FFG (kg feed DM intake/kg LW gain) did not differ among treatments. In this experiment, FFG ranged from 8.47 to 10.77 (Table 3). Concentrate supplementation (R₁, R₂ and R₃) approximately doubled (P > 0.01) the value of daily iIOFC compared with the control group (R₀; Table 3).

Table 3.  Daily intake of feeds, average daily gain and income over feed cost (IOFC) of Ongole bulls fed CFS (R₀) and CFS + concentrate supplements (R₁, R₂ and R₃).

Ongole bulls are a breed of Bos indicus cattle with a similar origin locality to the source of Nellore bulls in Brazil, but they have not had the same selection pressure applied. The mature weight of cows is approximately 348 kg (Mayberry et al. 2014), and their smaller size means they have a valuable role in smallholder systems of production. Mayberry et al. (2014) evaluated the nutritional requirements of cows and bulls using the Australian Ruminant Feeding Standards (Freer et al. 2007) and the North American Large Ruminant Nutrition System (Fox et al. 2004), and concluded that they have similar nutritional requirements and respond similarly as other Bos indicus breeds. This experiment examined strategies by which ADG of bulls could be increased at a village level. Smallholder systems have limited opportunities to increase the ME intake and ADG with available feed resources. The use of cassava and its by-products provide one way in which the ME content and presumably ME intake could be increased. Cassava is widely grown in Indonesia and other Asian and African countries, but can also be widely grown across northern Australia and Central and South America (Fukai and Hammer 1987), and as such, its use as a supplement or in a total mixed ration has wide international application. It is low in CP, so ingredients high in CP need to be added to the mix. Protein meals, such as CM and SBH, are often used in various feeding systems, but their cost and availability can vary markedly across Indonesia, and the use of locally available tree legumes, such as Gliricidia and Leucaena, offer a pathway to combine ingredients at lower cost or higher availability. This experiment has demonstrated that the ADG and IOFC of three supplement mixes based on these protein sources with a high ME (>10 MJ ME/kg DM) content ingredient (DCP) was markedly improved, and that there were no major differences between supplement types based on GLM and DCP and those based on protein meals or by-products (CM or SBH).

The ADG of Ongole bulls maintained under the CFS was 0.31 kg/head with feed intake of 1.8% LW/day (Table 3). These ADG and intake values are similar to those reported by Wiyatna et al. (2012) in a very similar production system with Ongole bulls (ADG of 0.25 kg/head with a feed intake of 1.3% LW/day) and Marsetyo et al. (2021) with fresh corn stover (0.31 kg/head). Supplementation increased the ADG to 0.60–0.75 kg/head (Table 3), which was similar to Lestari et al. (2011) of 0.78 kg/head and Marsetyo et al. (2021) of 0.69 kg/head. In controlled experiments with Ongole bulls on research stations, Mayberry et al. (2014) recorded ADG values up to 1.3 kg/day with diets based on corn grain and protein meals. Increasing the ADG of bulls under supplementation achieved here is a major change to the production system and substantially reduces the time taken to reach sale weights. The results of Mayberry et al. (2014) indicate that there is still a large opportunity for improvement.

The effectiveness of a supplement to increase the ADG of a cut and carry forage system depends on the nutrient content of the supplement. The estimated ME content of the CFS and the various supplement mixes are seen in Table 2. Treatment R₁ was based on a previous mix that markedly increased the ADG in Euro × Ongole bulls, but relied on protein meals. Treatments R₂ and R₃ replaced some of the protein meal sources with GLM. This strategy increased the ME content of the supplement. and enabled a higher DM and hence ME intake to be achieved with an expected increase in ADG (Table 3). Furthermore, it provided a basis for inclusion of GLM into the supplement.

In this study, it was shown that GLM was not an equivalent substitute for SBH and CM (R₁ vs R₂ and R₃) in terms of ADG (Table 3). There was no difference in ADG between the two supplement concentrates containing GLM (R₂ vs R₃). Proximate analysis comparisons of the three feed ingredients showed TDN (and estimated ME) content in GLM was 61.5% (9.6 MJ ME/kg DM) and comparable to SBH (62.7% and 9.9 MJ ME/kg DM). These TDN (and ME) values were lower than CM (74.6% and 12.0 MJ ME/kg DM). Furthermore, CP content in GLM was comparable to CM (19.1% and 20.1%, respectively), and higher than SBH (12.5%). However, when combined with DCP, the three concentrate treatments had comparable CP, TDN and ME contents (Table 2).

Intake by bulls in R₀ (CFS) was 3.38 kg DM/head per day (1.80% of LW; Table 3), which is in agreement with Wiyatna et al. (2012) who reported intakes of 2.38–4.37 kg/head per day in traditional village Ongole bulls of similar LW using a cut and carry feeding system.

The feed intake in supplemented treatments (R₁, R₂ and R₃) ranged from 5.58 to 6.29 kg/head per day, which was similar to Lestari et al. (2011) who reported that the feed intake of Ongole bulls of similar LW, could reach 6.42 kg/head per day. Intake in treatments R₁, R₂ and R₃ ranged from 2.38 to 2.69% LW/day, which was lower than Marsetyo et al. (2021) who recorded an intake of 3.28% LW/day in Ongole bulls supplemented with cassava powder and fresh G. sepium. Marsetyo et al. (2021) offered a similar supplement at 1.6% LW/day, whereas in this experiment, concentrates were given at 1% LW/day. There appeared to be no substitution of the basal forage in this experiment under a supplement level of 1% LW, and this facilitated the high response in the ADG (up to 0.7 kg/day) to supplement. This lack of substitution contrasted with a substitution effect of 0.43 (kg basal diet reduction in intake/kg supplement intake) recorded by Marsetyo et al. (2021).

The FFG (kg feed intake in DM/kg ADG) did not differ between treatments (Table 3). The FFG in this experiment ranged from 8.47 to 10.77 which was close to the FFG of intensively raised Ongole cattle (9.2, Lestari et al. (2011) and 12.6, Marsetyo et al. (2021)). These values are higher than feedlot values derived from Retnaningrum et al. (2021) of 5.5. The FFG is very important in determining the profitability of any feeding system.

GLM can be used as an alternative protein source to substitute these protein meal by-products. The ADG and FGR may have been improved at higher levels of supplementation than used in the current experiment, as found by Marsetyo et al. (2021). The level of supplement is often set by the risk of cash outlay rather than the biological response.

The IOFC approximately doubled under supplementation, a very beneficial result to the farmer. In the current situation, GLM was much cheaper than CM and SBH. Concentrate mixtures that contain GLM (R₂ and R₃) cost 2998–3075 IDR/kg DM, whereas the concentrate that contained CM and SBH (R₁) cost 4156 IDR/kg DM (Table 2). This coupled with little difference in FFG of the supplemented groups meant that IOFC was markedly increased under supplementation. Priyanti et al. (2012) reported that IOFC values can be used as an initial indicator to determine the viability of a fattening operation, although the IOFC values are less responsive to daily feed cost than ADG (Cowley et al. 2020). These products are readily available, but range widely in price depending on the region and markets for the DCP. Dried cassava powder can be quite expensive to purchase (as done here), but if home grown, the cost can be much lower (IDR 3617/kg DM vs IDR 1000/kg DM respectively). Thus, systems can be devised to produce a supplement of even lower cost than outlined here, and hence even higher IOFC.

The use of concentrate supplements (at a level 1% LW/day) consisting of 25% GLM, 50% DCP and either 25% SBH or 25% CM can increase the ADG of Ongole bulls from 0.31 kg to 0.61–0.62 kg/head. Cost and availability are two factors that determine the ingredients of a supplement mix. Using DCP and various protein sources provide a practical supplement mix that will increase the ADG and IOFC for farmers. Therefore, the concentrate formula consisting of DCP, GLM and SBH or CM can be used as an alternative supplement for smallholder farmers. A least cost ration formulation system would be useful in formulating supplements for beef cattle to meet the requirement for ME content and CP content (8–10%).

The data that supports this study will be shared upon reasonable request to the corresponding author.

Karen Harper is Associate Editor of Animal Production Science, but is blinded from the peer review process for this paper.

The authors express their sincere gratitude to the Australian Centre for International Agricultural Research (ACIAR) for providing financial support for the research (LPS/2013/021, Profitable Feeding Strategies for Smallholder Cattle in Indonesia).