Advances in Animal and Veterinary Sciences

Download PDF Download ePUB
AAVS_9_9_1416-1423

 

 

Research Article

 

The Potency of Traditional Market Vegetable Waste as Ruminant Feed in the Special Region of Yogyakarta

 

Muhsin Al Anas1*, Himmatul Hasanah2, Ali Agus1

1Department of Animal Nutrition and Feed Science, Faculty of Animal Science, Universitas Gadjah Mada, Yogyakarta, Indonesia; 2Department of Biology Education, Faculty of Math and Science, Yogyakarta State University, Yogyakarta, Indonesia.

 

Abstract | The relatively high-volume of vegetable waste in the Special Region of Yogyakarta Province causes environmental problems. Although it contains high nutrients, vegetable waste potential as ruminant feed is yet optimally utilized due to the possible presence of heavy metals such as Pb, Cu, and Hg, which can reduce livestock productivity. This study aimed to determine the nutrients and heavy metals content of vegetable waste from 11 traditional markets in Yogyakarta. The results showed vegetable waste contains protein (>20%) and fiber (<30%). It was also noted that the heavy metal concentration is below the maximum tolerable limit for ruminant feed ingredients. The nutrient and heavy metal content showed no difference between Sleman District, Bantul District, and Jogja City. This study concludes that vegetable waste from traditional markets in the Special Region of Yogyakarta has prospective as ruminant feed due to its high nutrient content with a low level of heavy metal.

 

Keywords | Ruminant feed, Heavy metals, Nutrients, Vegetable waste, Yogyakarta

 

Received | May 14, 2021; Accepted | June 12, 2021; Published | July 28, 2021

*Correspondence | Muhsin Al Anas, Department of Animal Nutrition and Feed Science, Faculty of Animal Science, Universitas Gadjah Mada, Yogyakarta, Indonesia; Email: muhsin_alanas@ugm.ac.id

Citation | Al Anas M, Hasanah H, Agus A (2021). The potency of traditional market vegetable waste as ruminant feed in the special region of yogyakarta. Adv. Anim. Vet. Sci. 9(9): 1416-1423.

DOI | http://dx.doi.org/10.17582/journal.aavs/2021/9.9.1416.1423

ISSN (Online) | 2307-8316; ISSN (Print) | 2309-3331

Copyright © 2021 Al Anas et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

 

INTRODUCTION

 

The Special Region of Yogyakarta has a relatively high potential for vegetable waste due to the presence of many traditional markets as places for high-intensity vegetable transactions. Vegetables and fruit waste in traditional markets reaches 84% of total market waste (Cahyari and Sahroni, 2015). This waste was not optimally utilized and had an impact on environmental pollution. Processing vegetables and fruits waste into alternative feed can increase livestock productivity with low costs. Besides, it can reduce the pile of vegetable waste that pollutes the environment.

 

The problem with vegetable waste as ruminant feed is the high heavy metal content. Heavy metals consumed by ruminants decrease rumen fermentation performance and feed digestibility. Heavy metals become enzyme inhibitors in the gastrointestinal tract cause feed degradation was not optimal. Inhibited nutrient utilization causes a decrease in livestock productivity (Yue et al., 2007; Mudhoo and Kumar, 2013; Marounek and Joch, 2014). Heavy metals such as Pb, Cu, and Cr in vegetables exceed the maximum limit (Zhou et al., 2016; Latif et al., 2018). Based on this description, this study aims to determine the potential and heavy metal contamination of traditional market vegetable waste in the Special Region of Yogyakarta.

 

MATERIALS AND METHODS

 

Samples collection

Vegetable waste samples were collected from 11 traditional markets in the Special Region of Yogyakarta. Three traditional markets in Sleman District include Demangan, Condong Catur, and Gamping, three traditional markets in Bantul District covering Piyungan, Barongan, and Bantul. Meanwhile, five traditional markets in Jogja City include Kranggan, Beringharjo, Kotagede, Prawirotaman, and Giwangan. From each traditional market, a total of ±12 kg of vegetable waste was collected at three different points as replications, with ±4 kg of the sample at each replication. Vegetable waste samples were stored in plastic bags for laboratory analysis.

 

Identify the type of vegetable waste

A total of 1-2 kg of collected vegetable waste was used for identification. Vegetable waste was separated based on the variety and weighed to get the percentage of each vegetable waste.

 

Vegetable waste drying

The unsorted vegetable waste sample (1 kg), divided into three parts and wrapped in a weighed paper bag. The wrapped samples were heated in a 55°C oven for 3-5 days to obtain air-dried samples. The dry waste samples were ground into powder using a Wiley 2 mm grinding machine. Vegetable waste samples were analyzed proximate (crude protein, crude fat, crude fiber, dry matter, and organic matter) using the AOAC (2005) and heavy metals (Pb, Cu, and Hg) through the atomic absorption spectroscopy (AAS) method (Hina et al., 2011).

 

Data analysis

Data were analyzed by one-way analysis of variance (ANOVA) with a completely randomized design, followed by Duncan’s Multiple Range Test (DMRT) to determine the difference between mean values (Gomez and Gomez, 1984).

 

RESULTS AND DISCUSSION

 

The potential of traditional market vegetable waste in the Special Region of Yogyakarta is presented in Table 1. The results showed that each traditional market in Sleman District, Bantul District, and Jogja City had high potential based on the vegetable variety. Each traditional market has an average of 12 types of vegetable waste and was dominating by vegetables such as cabbage, spinach, water spinach, mustard greens, Chinese cabbage, green beans, chayote, cucumber, carrots, tomatoes, long beans, and jackfruit peels. A variety of waste will have various types of nutrients and potential as ruminant feed. According to some researchers, vegetable waste such as carrots, cabbage, spinach, cauliflower, tomatoes, banana leaves, corn husks, onion peels, cassava leaves, taro, jackfruit, cucumbers, potatoes, pumpkins, leek, celery, lettuce, broccoli, bananas, oranges, grapes, melons, pears, and plums have the potential as feed for ruminants (Ezeldin et al., 2016; Wadhwa and Bakshi, 2013; Bakshi et al., 2016; Mahgoub et al., 2020).

 

There are many traditional markets in the Special Region of Yogyakarta. According to Statistics Indonesia (2019), the Special Region of Yogyakarta has 357 traditional markets. The number of traditional markets is due to the high people’s preference for purchases in traditional markets. People choose vegetables at an affordable price. Vegetables were mostly produced in rural areas in the Special Region of Yogyakarta, which affected the variety of vegetables in traditional markets. Furthermore, the supply of vegetables also comes from other producer areas, such as Magelang and Boyolali, which have vegetable production centers.

 

The chemical composition analysis of traditional market vegetable waste in the Special Region of Yogyakarta is shown in Table 2. The chemical composition of traditional market vegetable waste in Sleman District, Bantul District, and Jogja City were no different (P>0.05). It was due to the high percentage of aste variety in each district almost same.

 

The chemical composition analysis showed that vegetable waste protein content reached 19%, and fiber lower than 30% would support livestock growth. The protein and the fiber content of vegetable waste are almost equivalent to elephant grass (Pennisetum purpureum S.) at 13.47-19.43% and 29.60-35.50% (Haryani et al., 2018), and Setaria grass (Setaria sphacelata) about 20.31-23.44% and 24.02-30.41% (Fitriana et al., 2017). According to Bakshi et al. (2016), vegetable waste is a good source of crude fiber and energy, especially for ruminants. Sheep requires about 9.8-16.7% protein (National Research Council, 1985), vegetable waste as an alternative feed can increase productivity at an economical cost. According to research by Retnani et al. (2014), the utilization of 100% vegetable waste as wafers feed-in sheep has the highest body weight gain and a final weight of 25.6% higher than conventional feed.

 

The result of the analysis of heavy metal content in vegetable waste is presented in Table 3. The results showed that the contamination of heavy metals Pb, Cu, and Hg in Sleman District, Bantul District, and Jogja City did not show a significant difference (P>0.05). Pb contamination in all traditional markets is below 0.01 mg/kg. The maximum level of Pb contamination in forage for feed is 10-50 mg/kg (Reis et al., 2010; Adamse et al., 2017). Pb contamination in vegetable waste was still lower than the maximum level of Pb feed contamination. The maximum Hg

 

Table 1: The potential of traditional market vegetable waste in the Sleman District, Special Region of Yogyakarta

 

No. Market

Name

Vegetable Type Botanical Name Total

(g)

Percentage

(%)

1. Demangan Basil leaves Ocimum basilicum 1033 18.384%
    Jackfruit peels Artocarpus heterophyllus 534 9.503%
    Grated coconut Cocos nucifera 453 8.062%
    Papaya Carica papaya 444 7.902%
    Cucumber Cucumis sativus 393 6.994%
    Banana leaves Musa paradisiaca 373 6.638%
    Water spinach Ipomoea aquatica 345 6.140%
    Others   330 5.873%
    Spinach Amaranthus spp. 279 4.965%
    Eggplant Solanum melongena 263 4.681%
    Bamboo shoots Dendrocalamus asper 235 4.182%
    Young jackfruit Artocarpus heterophyllus 206 3.666%
    Mustard greens parachinensis 170 3.025%
    Chinese cabbage Brassica rapa subsp. pekinensis 144 2.563%
    Cabbage Brassica oleracea 140 2.492%
    Ridge gourd Luffa acutangula 107 1.904%
    Scallion Allium fistulosum 42 0.747%
    Chayote Sechium edule 34 0.605%
    Green beans Phaseolus vulgaris 22 0.392%
    Celery Apium graveolens 21 0.374%
    Long beans

Vigna cylindrica (L.)

18 0.320%
    Carrot Daucus carota 12 0.214%
    Corn husk Zea mays 8 0.142%
    Grape Vitis vinifera 7 0.125%
    Cassava leaves Manihot utilissima 6 0.107%
2. Condong Catur Chinese cabbage Brassica rapa subsp. pekinensis 1755 34.574%
    Chayote Sechium edule 1142 22.498%
    Cabbage Brassica oleracea 670 13.199%
    Water spinach Ipomea aquatica 606 11.939%
    Cassava leaves Manihot utilissima 244 4.807%
    Mustard greens parachinensis 242 4.768%
    Tomato Solanum lycopersicum 157 3.093%
    Eggplant Solanum melongena 135 2.660%
    Green beans Phaseolus vulgaris 51 1.005%
    Spinach

Amaranthus spp.

35 0.690%
    Long beans

Vigna cylindrica (L.)

15 0.296%
    Scallion Allium fistulosum 11 0.217%
    Onion peels Allium cepa 9 0.177%
    Chili Capsicum annuum 4 0.079%
3. Gamping Water spinach Ipomea aquatica 1448 32.701%
    Spinach

Amaranthus spp.

627 14.160%
    Kenikir leaves Cosmos caudatus 527 11.902%
    Cabbage Brassica oleracea 384 8.672%
    Mustard greens Brassica rapa subsp. parachinensis 362 8.175%
    Cucumber Cucumis sativus 319 7.204%
    Carrot peels Daucus carota 234 5.285%
    Guava Syzygium aqueum 89 2.010%
    Pumpkin Cucurbita moschata Durch 70 1.581%
    Eggplant Solanum melongena 67 1.513%
    Others   64 1.445%
    Chayote Sechium edule 53 1.197%
    Radish Raphanus sativus 42 0.949%
    Long beans

Vigna cylindrica (L.)

42 0.949%
    Corn Zea mays 31 0.700%
    Green beans Phaseolus vulgaris 23 0.519%
    Scallion Allium fistulosum 16 0.361%
    Chili Capsicum annuum 15 0.339%
    Daun melinjo Gnetum gnemon 8 0.181%
    Klutuk banana leaves Musa balbisiana 5 0.113%
    Cassava leaves Manihot utilissima 2

0.045%

 


Table 2: The potential of traditional market vegetable waste in the Bantul District, Special Region of Yogyakarta

 

No. Market

Name

Vegetable Type Botanical Name Total

(g)

Percentage

(%)

1. Piyungan Cabbage Brassica oleracea 2338 58.877%
    Spinach

Amaranthus spp.

587 14.782%
    Mustard greens Brassica rapa subsp. parachinensis 505 12.717%
    Bay leaves Syzygium polyanthum 312 7.857%
    Bamboo shoots Dendrocalamus asper 131 3.299%
    Bitter melon Momordica charantia 98 2.468%
2. Barongan Cucumber Cucumis sativus 958 19.740%
    Bitter melon Momordica charantia 753 15.516%
    Cabbage Brassica oleracea 689 14.197%
    Tomato Solanum lycopersicum 560 11.539%
    Eggplant Solanum melongena 261 5.378%
    Water spinach Ipomea aquatica 257 5.296%
    Klutuk banana leaves Musa balbisiana 235 4.842%
    Carrot Daucus carota 180 3.709%
    Long beans

Vigna cylindrica (L.)

175 3.606%
    Scallion Allium fistulosum 161 3.318%
    Cassava leaves Manihot utilissima 143 2.947%
    Banana Musa paradisiaca 138 2.844%
    Taro Colocasia esculenta 112 2.308%
    Others   83 1.710%
    Celery Apium graveolens 55 1.133%
    Cauliflower Brassica oleracea var. Botrytis 44 0.907%
    Mustard greens Brassica rapa subsp. parachinensis 44 0.907%
    Bay leaves Syzygium polyanthum 5 0.103%
3. Bantul Cabbage Brassica oleracea 1592 41.394%
    Carrot Daucus carota 771 20.047%
    Long beans

Vigna cylindrica (L.)

495 12.871%
    Cauliflower Brassica oleracea var. Botrytis 290 7.540%
    Mustard greens Brassica rapa subsp. parachinensis 205 5.330%
    Scallion Allium fistulosum 173 4.498%
    Water spinach Ipomea aquatica 163 4.238%
    Potato Solanum tuberosum 80 2.080%
    Green beans Phaseolus vulgaris 35 0.910%
    Ridge gourd Luffa acutangula 27 0.702%
    Eggplant Solanum melongena 8 0.208%
    Chili Capsicum annuum 7

0.182%

 


Table 3: The potential of traditional market vegetable waste in the Jogja City, Special Region of Yogyakarta

 

No. Market

Name

Vegetable Type Botanical Name Total

(g)

Percentage

(%)

1. Kranggan Green beans Phaseolus vulgaris 1178 27.796%
    Red apple Malus domestica 424 10.005%
    Long beans

Vigna cylindrica (L.)

348 8.211%
    Spinach

Amaranthus spp.

324 7.645%
    Chinese cabbage Brassica rapa subsp. Pekinensis 287 6.772%
    Mustard greens parachinensis 272 6.418%
    Cabbage Brassica oleracea 269 6.347%
    Bamboo shoots Dendrocalamus asper 219 5.168%
    Star fruit Averrhoa carambola 179 4.224%
    Corn husk Zea mays 162 3.823%
    Celery Apium graveolens 144 3.398%
    Orange Citrus reticulata 115 2.714%
    Carrot Daucus carota 91 2.147%
    Scallion Allium fistulosum 89 2.100%
    Banana Musa paradisiaca 49 1.156%
    Eggplant Solanum melongena 31 0.731%
    Tomato Solanum lycopersicum 30 0.708%
    Chili Capsicum annuum 12 0.283%
    Mangosteen peels Garcinia mangostana 9 0.212%
    Rambutan peels Nephelium lappaceum 6 0.142%
2. Beringharjo Mustard greens Brassica rapa subsp. parachinensis 924 28.839%
    Cabbage Brassica oleracea 907 28.308%
    Eggplant Solanum melongena 322 10.050%
    Madeira vine Anredera cordifolia 300 9.363%
    Scallion Allium fistulosum 259 8.084%
    Celery Apium graveolens 243 7.584%
    Carrot Daucus carota 221 6.898%
    Parsley Petroselinum crispum 28 0.874%
3. Kotagede Cabbage Brassica oleracea 3222 74.774%
    Potato Solanum tuberosum 339 7.867%
    Scallion Allium fistulosum 308 7.148%
    Mustard greens Brassica rapa subsp. parachinensis 148 3.435%
    Long beans

Vigna cylindrica (L.)

130 3.017%
    Bay leaves Syzygium polyanthum 66 1.532%
    Celery Apium graveolens 54 1.253%
    Others   32 0.993%
    Chili Capsicum annuum 4 0.093%
    Klutuk banana leaves Musa balbisiana 4 0.093%
    Carrot peels Daucus carota 2 0.046%
4. Prawirotaman Sweet leaves Sauropus androgynus 1619 37.827%
    Jackfruit peels Artocarpus heterophyllus 783 18.294%
    Water spinach Ipomea aquatica 530 12.383%
    Spinach

Amaranthus spp.

475 11.098%
    Cabbage Brassica oleracea 435 10.164%
    Chayote Sechium edule 136 3.178%
    Carrot Daucus carota 102 2.383%
    Orange Citrus reticulata 71 1.659%
    Banana peels Musa paradisiaca 33 0.771%
    Kenikir leaves Cosmos caudatus 26 0.607%
    Scallion Allium fistulosum 24 0.561%
    Tomato Solanum lycopersicum 19 0.444%
    Cassava leaves Manihot utilissima 18 0.421%
    Bay leaves Syzygium polyanthum 7 0.164%
    Green beans Phaseolus vulgaris 2 0.047%
5. Giwangan Mustard greens Brassica rapa subsp. parachinensis 3268 85.438%
    Tomato Solanum lycopersicum 378 9.882%
    Eggplant Solanum melongena 105 2.745%
    Corn husk Zea mays 74

1.935%


 

Table 4: Chemical composition of traditional market vegetable waste in the Special Region of Yogyakarta (%)*

 

District Dry

Matter

Organic

Matter

Crude Protein Crude

Fiber

Ether Extract Total Digestible Nutrient
Sleman 93.19 19.43 19.03 20.66 2.13 63.00
Bantul 89.79 22.96 18.90 23.42 1.69 68.80
Jogja City 91.04 22.30 22.73 20.11 1.47 68.33
Average 91.06 21.81 19.98 21.76 1.75 67.09
SE 1.913 1.189 0.966 1.110 0.191 1.713
P-value 0.802 0.507 0.235 0.434 0.478

0.230


*dry weight

 

Table 5: The heavy metal content of traditional market vegetable waste in the Special Region of Yogyakarta (dry matter sample)

 

District Lead (Pb, mg/kg) Copper (Cu, mg/kg) Mercury (Hg; µg/kg)
Bantul <0.01 18.39 23.46
Sleman <0.01 18.50 33.12
Jogja City <0.01 12.54 14.52
Average <0.01 16.84 25.41
SE 0.000 1.740 5.414
P-value 1.000 0.352 0.397

 


contamination in the feed is 0.1 mg/kg. The Hg content in vegetable waste is still lower than the contamination limit based on Adamse et al. (2017). The standard of Hg content in ruminant feed is 0.1 mg/kg. Hg contamination in vegetable waste is below the maximum contamination limit.

 

The heavy metals content in vegetables was affected by several factors, such as pesticides and herbicides application, fertilizers, air pollution, soil and irrigation water contaminated with waste, and poor handling during the distribution process (Onakpa et al., 2018; Ruzaidy and Amid, 2020). The problem of utilizing vegetable waste as feed is high heavy metals contamination causes risks to livestock. Heavy metals such as Pb, Cu, and Cr, contained in vegetables, exceed normal permissible limits. Heavy metals consumed by ruminants will reduce rumen fermentation performance and decrease feed digestibility. Heavy metals become enzyme inhibitors in the digestive tract caused less feed degradation. Low nutrient utilization decreased livestock productivity (Yue et al., 2007; Marounek and Joch, 2014).

 

The consumption of heavy metals through the feed can become a residue in meat and is dangerous if consumed by humans. Research by Sudiyono (2011) shows that cattle that consume heavy metals lead heavy metal contamination of meat to exceed the maximum limit, causing humans health problems. Sheep that grazing in landfill area contains heavy metals on lamb meat over the permissible limit (Rahayu et al., 2016). Consuming heavy metals causes damage to the brain, lungs, kidneys and liver function, blood composition, and other essential organs. Long-term exposure can lead to physical, muscular, and neurological degenerative processes that imitate diseases such as multiple sclerosis, Parkinson’s disease, Alzheimer’s disease, muscular dystrophy, hypertension, cancer, and may even cause death (Mudgal et al., 2010; Jaishankar et al., 2014) (Table 4 and 5).

 

CONCLUSION

 

Traditional market vegetable waste in the Special Region of Yogyakarta is potentially utilized as a ruminant feed based on the variety and chemical composition. Heavy metal contamination of Pb, Cu, and Hg in vegetable waste was still below the permissible limit for ruminant feed.

 

acknowledgements

 

Laboratory of Nutritional Biochemistry, Faculty of Animal Science, Universitas Gadjah Mada, Yogyakarta, Indonesia.

 

CONFLICT OF INTEREST

 

The authors declare that there is no conflict of interest.

 

authors contribution

 

Muhsin Al Anas designed, performed the experiment and wrote the manuscript. Himmatul Hasanah collected the samples and analyzed the data. Ali Agus supervised all the study and revised the manuscript. All authors read and approved the final manuscript for publication.

 

REFERENCES

 

  • Adamse P, van der Fels-Klerx HJ, de Jong J (2017). Arsenic, lead, cadmium and mercury in animal feed and feed materials; Trend analysis of monitoring results collected in the Netherlands. Wageningen. https://doi.org/10.18174/416680
  • AOAC (2005). Official Methods of Analysis. 20th ed. Association of Official Analytical Chemists, Washington DC, USA.
  • Bakshi MPS, Wadhwa M, Makkar HPS (2016). Waste to worth: Vegetable wastes as animal feed. CAB Rev. Perspect. Agric. Vet. Sci. Nutr. Nat. Resour. 11: 1 – 26. https://doi.org/10.1079/PAVSNNR201611012
  • Cahyari K, Sahroni A (2015). Effect concentration of Chili pepper (Capsicum annum L.) and Tabasco pepper (Capsicum frutescens L.) on biogas production from organic waste. J. Bahan Alam Terbarukan 4: 8 – 15.
  • Ezeldin I, Massaad O, Omer SA (2016). Evaluation of some vegetable wastes as feedstuff for ruminants. Int. J. Sci. Res. 5: 628 – 631. https://doi.org/10.21275/v5i3.NOV161789
  • Fitriana PR, Akbarillah HT, Supratman JWR, Limun K, Fax BT (2017). Quality of the nutrition of Setaria spacellata grass harvested based on cutting intervals. J. Sain Peternak. Indonesia. 12: 444 – 453. https://doi.org/10.31186/jspi.id.12.4.444-453
  • Gomez KA, Gomez AA (1984). Statistical Procedure for Agricultural Research. John Wiley and Sons, USA.
  • Haryani H, Norlindawati AP, Norfadzrin F, Aswanimiyuni A, Azman A (2018). Yield and nutritive values of six Napier (Pennisetum purpureum) cultivars at different cutting age. Malaysian J. Vet. Res. 9: 6 – 12.
  • Hina B, Rizwani GH, Naseem S (2011). Determination of toxic metals in some herbal drugs through atomic absorption spectroscopy. Pak. J. Pharm. Sci. 24: 353 – 358.
  • Jaishankar M, Tseten T, Anbalagan N, Mathew BB, Beeregowda KN (2014). Toxicity, mechanism and health effects of some heavy metals. Interdiscip. Toxicol. 7: 60 – 72. https://doi.org/10.2478/intox-2014-0009
  • Latif A, Bilal M, Asghar M, Azeem M, Ahmad MI, Abbas A, Ahmad MZ, Shahzad T (2018). Heavy metal accumulation in vegetables and assessment of their potential health risk. J. Environ. Anal. Chem. 5: 1000234. https://doi.org/10.4172/2380-2391.1000234
  • Mahgoub O, Kadim IT, Eltahir Y, Al-Lawatia S, Al-Ismail AM (2020). Nutritional value of vegetable wastes as livestock feed. Sultan Qaboos Univ. J. Sci. [SQUJS] 23: 78 – 84. https://doi.org/10.24200/squjs.vol23iss2pp78-84
  • Marounek M, Joch M (2014). Effects of heavy metals and arsenate on the Ovine rumen fermentation in vitro. Agric. Trop. Subtrop. 47: 106 – 108. https://doi.org/10.2478/ats-2014-0014
  • Mudgal V, Madaan N, Mudgal A, Singh RB, Mishra S (2010). Effect of toxic metals on human health. Open Nutraceuticals J. 3: 94– 99. https://doi.org/10.2174/18763960010030100094
  • Mudhoo A, Kumar S (2013). Effects of heavy metals as stress factors on anaerobic digestion processes and biogas production from biomass. Int. J. Environ. Sci. Technol. 10: 1383 – 1398. https://doi.org/10.1007/s13762-012-0167-y
  • National Research Council (1985). Nutrient Requirements of Sheep. National Academy Press, Washington DC.
  • Onakpa MM, Njan AA, Kalu OC (2018). A review of heavy metal contamination of food crops in Nigeria. Ann. Glob. Heal. 84: 488 – 494. https://doi.org/10.29024/aogh.2314
  • Rahayu P, Munawaroh IS, Elok K (2016). Comparison of heavy metal residues on sheep that grazing in landfill area before and after elimination process. Pages 319–326 in Proceedings of International Seminar on Livestock Production and Veterinary Technology 2016. https://doi.org/10.14334/Proc.Intsem.LPVT-2016-p.319-326
  • Reis LSLS, Pardo PE, Camargos AS, Oba E (2010). Mineral element and heavy metal poisoning in animals. J. Med. Med. Sci. 1: 560 – 579.
  • Retnani Y, Saenab A, Taryati (2014). Vegetable waste as wafer feed for increasing productivity of sheep. Asian J. Anim. Sci. 8: 24 – 28. https://doi.org/10.3923/ajas.2014.24.28
  • Ruzaidy NIM, Amid A (2020). Heavy metal contamination in vegetables and its detection: A review. Sci. Herit. J. 4: 01 – 05. https://doi.org/10.26480/gws.01.2020.01.05
  • Statistics Indonesia (2019). Market and Trade Center Distribution By Classifications 2019. Available at https://www.bps.go.id/indicator/173/1875/1/sebaran-pasar-dan-pusat-perdagangan-menurut-klasifikasi.html (verified 2 February 2021).
  • Sudiyono S (2011). Efforts of elimination of residual heavy metals in beef cattle from the waste disposal site locations with conventional maintenance. Sains Peternakan. 9(1): 1 – 7.
  • Wadhwa, M., and S. P. M. Bakshi. 2013. Utilization of fruit and vegetable wastes as livestock feed and as substrates for generation of other value-added products (HPS Makkar, Ed.). FAO, Bangkok.
  • Yue ZB, Yu HQ, Wang ZL (2007). Anaerobic digestion of cattail with rumen culture in the presence of heavy metals. Bioresour. Technol. 98: 781 – 786. https://doi.org/10.1016/j.biortech.2006.03.017
  • Zhou H, Yang WT, Zhou X, Liu L, Gu JF, Wang WL, Zou JL, Tian T, Peng PQ, Liao BH (2016). Accumulation of heavy metals in vegetable species planted in contaminated soils and the health risk assessment. Int. J. Environ. Res. Public Health. 13: 289 – 300. https://doi.org/10.3390/ijerph13030289
  •