Oil Palm Tree Wastes 10: The feeding value of PKM for livestock

Published Date: 7th December 2020

Introduction

It is the identification of palm kernel meal/cake as a cheap, and readily available feed raw material from oil palm processing countries that primarily changed its status from that of an agro-industrial waste to that of a valuable by-product or bio-resource. In oil palm producing countries of West African such as Nigeria, PKM has basically no use other than in feeding livestock, mostly because of its availability, and low cost when compared to other common feed ingredients. For example, a 2017 estimate from Nigeria showed that palm kernel cake (PKC) costs less than a third of the price of maize, maize offal, soya bean meal, or groundnut cake, and about a fifth of the cost of both solvents, and mechanically extracted soybean meal. Researchers have therefore concluded that commercial utilization of PKC in poultry, and pig feeding represents the least cost, and practicable alternative in an industry consistently challenged by the rising cost of conventional feed raw materials.

Again, PKM has relatively no major anti-nutritional constituent. It is aflatoxin free, palatable, and has shown considerable potential as a source of carbohydrate, and protein in livestock feeds. The nutrient content however ranges widely, depending on the oil extraction process, the species of the palm nut, and the amount of shell remaining in the meal. The crude protein content ranges from 14 to 21 percent, and has been classified as a medium grade protein. The metabolizable energy, and crude fiber average 2500 kcal/kg and 17.5 percent respectively, although most of the fiber is in the form of mannan, a highly indigestible non-soluble polysaccharide (NSP). Indeed, PKM is relatively low in nutritive value, it is gritty, and may be contaminated with shell fractions, and oil residue, which may become rancid, thereby affecting its taste. Its consistent availability, and competitive price, has however made it popular among farmers as a moderate source of protein, and energy for beef cattle, dairy cows, pigs, rabbits, laying hens, and broiler chickens. Its inclusion in poultry diets is also being advocated not only because of its nutritional value, but its beneficial effect on health as a source of manna-oligosaccharides (MOS), a prebiotic that enhances feed efficiency, and intestinal health of the chicken. Sophisticated technical processes are however currently needed to extract MOS from PKM, while its inclusion in the diet may increase the cost of production.

Challenges and solutions to the use of PKM in livestock feeding

The major challenges to the use of PKM in livestock feeding include poor digestibility, low protein quality, rancidity, and the possibility of mold growth, especially in the hot humid tropical environment.
Poor digestibility: Poor digestibility of PKM is a major drawback to its use in the feeding of monogastric animals such as poultry and pigs. This is mostly due to its high level of fibers which are poorly digested by these animals. The fiber fractions that hinder the utilization of PKM by monogastric animals are chiefly lignin, and NSPs like β-glucan, mannan, and xylan. These fibers cause poor nutrient availability, high digestive viscosity, and fermentation, thus causing poor nutrient absorption, utilization, and watery faeces. The watery feces is particularly more pronounced in layers, and may increase the occurrence of dirty eggs, wet litter, bad odor, and nuisance flies under the deep litter system of management. Similar nutritional, and environmental challenges have been encountered with feeding PKM to pigs although to a lesser degree. These challenges have been generally overcome by feeding broilers, laying chicken, and pigs PKM-based diets, supplemented with either local crude enzyme produced by solid-state fermentation or commercial enzymes at different inclusion levels. For example, commercial enzyme preparations such as protease, cellulase, glucanase, xylanase, mannanase, pectinase, amylase, and galactosidase could be added to unlock the nutrients.

Poor protein quality: Based on amino acid scores, PKM protein has been characterized as generally poor, and therefore does not particularly favor poultry nutrition. The quality of PKM protein may also be affected by Millard reaction or browning, which is due to reactions between lysine, and carbohydrate during the heat treatment of the protein in the PKM to form indigestible complexes. Generally, industrial processes that encourage more efficient yield of oil from the palm kernel encourage browning of the cake, and reduction in its nutritional quality. Poor quality protein in the PKM is usually ameliorated through supplementations with essential, and limiting amino acids in the form of synthetic lysine, and methionine in the PKM-based diets.    

Rancidity: PKC may contain as much as 8.0 percent oil residue, which under poor storage conditions could be susceptible to rancidity. Fats, and oils containing unsaturated fatty acids, especially polyunsaturated fatty acids such as linoleic, linolenic, and arachidonic acids can undergo oxidative rancidity when exposed to oxygen resulting in either poor nutritional value or change in physical conditions of the fats, and oils. Microbial rancidity usually occurs under poor storage, when the enzyme, lipase produced by bacteria or mold breaks down the long-chain fatty acids to short-chain ones. The rancidity of PKC will usually result in its odor, and color changes, and poor palatability, leading to low feed intake, and lower productivity in animals fed the rancid feed. The addition of natural antioxidants such as vitamin E, vitamin C, flavonoids, and carotenoids or synthetic ones such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and ethoxyquin (1, 2-dihydro-6-ethoxy-2, 2, 4- trimethylquinoline) to PKC during storage, has been shown to be effective in limiting its rancidity during storage.

Mold growth: Extended poor storage conditions, especially under the prevailing high humidity, and temperature conditions in tropical countries can encourage mold growth, and elaboration of different types of mycotoxins in the PKM. Fermentation of PKM to improve its nutrient value, which is commonly practiced by small-scale pig farmers in Nigeria when poorly done could also encourage mold growth, and production of harmful mycotoxins in the product. Mold, and mycotoxin inhibitors such as clays, aluminosilicate, glucomannan, yeast cell wall, and plant extracts can be added to the PKM-based diet to prevent the harmful effects of mycotoxin.

The feeding value of PKM for poultry

The inclusion of PKM in poultry diets has been basically driven by the need to reduce the cost of poultry feeds. In Nigeria, palm kernel cake is a readily available feedstuff increasingly used to partially replace the very costly conventional feedstuffs like maize, soybean, and groundnut cake in poultry and pig diets. Earlier studies in Nigeria established that PKC can be fed to the starter, and finisher broiler chicks at 28 and 35 percent inclusion levels respectively, while starter and grower pullets can be fed up to 34 and 38 percent respectively without any deleterious effect on performance. Although higher levels of PKC may be fed to different classes of poultry without incurring significant reductions in performance, researchers at the Federal University of Technology Owerri, Nigeria, recommend that PKC be included in poultry diets at 25 percent for broiler starter, 35 percent for broiler finisher, 30 percent for layer starter, 40 percent layer grower, and 35 percent for laying birds.

Palm kernel cake has also been combined with other cheap, and readily available non-conventional feedstuffs such as plantain, and yam peels as an energy source to replace the costlier maize in the diets of different classes of poultry. Recent research reports from the Federal University of Technology Owerri, Nigeria, observed that palm kernel cake, yam and plantain peels combined in the ratios of 1:1: 2 could be used to replace 50 percent of maize in the finisher broiler diet as a major source of energy, while in turkeys such a combination results in a significant reduction in feed cost, and better growth performances at both the grower, and finisher phases.  Again, researchers at the Federal University of Technology Owerri, Nigeria, have demonstrated that the physicochemical characteristics of a 3:1 ratio mixture of cassava root pulp, and palm kernel cake could be improved by solid-state fermentation, and that such a product could effectively replace up to 100 percent of the maize in broiler diets, without any deleterious effects on growth performance, and carcass quality.

Additives such as enzymes, and probiotics have also been used to enhance the nutrient value of PKM for poultry. For example, bioactive yeast (Saccharomyces cerevisiae) has been shown to secret enzymes that help in the digestion of the fibrous constituents of PKM. Such a study carried out at the University of Nigeria Nsukka, Nigeria, showed that supplementation of 0.8 gm yeast/kg of broiler chicks diet containing 30 percent PKC resulted in optimal weight gain, carcass quality, and economic return. The β-Mannan, and another non-starch polysaccharide in PKM that exert anti-nutritional activity in poultry have also been degraded with the aid of exogenous enzyme preparations. In a study at the College of Agriculture Lafia, Nigeria, a multi-enzyme (Hemicell +Roxazyme G) containing β- mannanase, α- galactosidase, glucanase, cellulose, and xylanase was added to broiler starter diets containing 10, 20, 30, and 40 percent inclusion levels of PKM at 500 g/ton and 500 g/ton respectively during 35 days of feeding. The results showed that enzyme addition significantly reduced the cost of feed consumed at 30 percent PKM inclusion level, while cost per kilogram weight gain, and the cost of production were lowest at 20 percent level.

The feeding value of PKM for PigsPKM is now basically used to lower the cost of feeding pigs in many oil palm producing, and processing countries. Several Nigerian studies have shown that up to 50 to 100 percent of the maize in swine diet could be replaced with PKM without any deleterious effect on the average daily feed intake, daily weight gain, feed efficiency, and protein utilization. Rather, the cost of feed consumed/day, and the feed cost/kg live weight gain of the pigs decreases with increasing levels of PKM inclusion, while apparent digestibility of the nutrients contained in the diets, and serum metabolites remain unaffected. A recent report by researchers at the Federal University of Technology Owerri, Nigeria, highlighted the importance of PKC in pig feeding among small-scale farmers in south-eastern Nigeria. These small-scale farmers have developed several on-farm methods of improving the utilization of PKC in pig feedings such as its fermentation in water or fresh cattle blood for several days prior to feeding to improve intake, palatability, and digestibility, while reducing the dustiness of the feed. Palm oil sludge is also used to ensile the PKC so as to increase the energy value of the meal. It is also mixed with cattle rumen digesta, and allowed to ferment for several days in order to improve its feeding value, while reducing the feeding costs, although the fiber content of the mix may increase substantially. The farmers utilize PKC as a binder for other alternative feedstuffs such as cassava flour or seriate, thereby enhancing the utilization of these cassava wastes with reduced deleterious effects. They may also mix PKC, cassava peel, and brewers spent grain to improve the utilization of both the cassava peels, and PKC by their pigs.

Several studies have indeed shown that one of the viable strategies for the effective utilization of PKC in monogastric animal nutrition is to blend it with other materials whose composition, and form can complement that of the PKC. For example, researchers at the Federal University of Technology Owerri, Nigeria, reported that solid-state fermentation of the mixture of PKC, and grated cassava root meal, with or without direct microbial inoculation yields value-added products with the potentials to replace maize in pig diets. They showed that 100 percent replacement of maize with such a product in piglet diet resulted in reduced feed intake, and better feed efficiency. Similarly, pigs at the growing-finishing phase, exhibited comparable performance indices with those on a maize-based diet, while also producing firmer, more consistent, and less odorous faeces. Similar results have been reported with co-fermentation products derived from PKC, and Okara, a soymilk processing waste.  

Recent innovative research at the Michael Okpara University of Agriculture, Umudike, Nigeria developed, and evaluated the utilization of sawdust/palm kernel cake/Zootech fortifier mix as a feed component for pigs in different small-scale farms in southeastern Nigeria. The Zootech fortifier mix is a highly nutritive product developed from the degradation of sawdust with Zymomonas mobilis, a bacteria found in palm wine/diastatic microbes found in snail with limestone, and bone meal to stabilize the products. In eight different experiments, the sawdust/palm kernel cake/Zootech fortifier mixed, were fed to weaned pigs at the following rates;

A = 30% sawdust/65% Palm Kernel Cake/5% Zootech fortifier mixed

B = 30% sawdust/30% Palm Kernel Cake/35% Spent grain/5% Zootech fortifier mixed

C = 30% sawdust/35% Palm Kernel Cake/30% Spent grain/5% Zootech fortifier mixed

D = 30% sawdust/20% Palm Kernel Cake/45% Spent grain/5% Zootech fortifier mixed

E = 20% sawdust/30% Palm Kernel Cake/25% Spent grain/5% Zootech fortifier mixed

F = 30% sawdust/25% Palm Kernel Cake/30% Spent grain/5% Zootech fortifier mixed

G = 20% sawdust/20% Palm Kernel Cake/20% Spent grain/5% Zootech fortifier mixed

H = 10% sawdust/20% Palm Kernel Cake/25% Spent grain/5% Zootech fortifier mixed

The final weight gain, feed intake, cost of feed/kg, cost of total feed intake, feed conversion ratio, mortality, lean meat, cost of production, gross profit, and profit after 50 days of feeding, were found to be superior at the range of 13.30 – 1415 percent, when compared with results gotten with the farmers feeding practices.

The feeding value of PKM for ruminantsPKM is widely used in many ruminant rations, including cattle, buffalo, sheep, goats, and deer, ration, especially in combination with other low energy roughages. In beef, and dairy cattle, it has been included up to 80 percent with good performance results. In Malaysia, a beef cattle formulation of 80 percent PKC, 4.0 percent rice bran, 15.0 percent grass/hay, 0.5 limestones, and 0.5 percent vitamin mix is routinely fed with excellent results. Similarly, a dairy cattle ration containing 50 percent PKC, 42.0 percent grass/hay, 5.0 percent molasses, 1.5 percent limestone, 1.0 percent premix, and 0.5 percent salt has been used to achieve an average milk yield of 10 – 14 L/day/head, and increased milk fat. Up to 50 percent of PKM has been allowed in the rations of grazing sheep and goats without any deleterious effects. The risk of copper toxicity has however been reported at high inclusion levels of 80 – 90 percent, and has been overcome by adding ZnSO4 or ammonium molybdate to the ration to give an average growth performance of 200 - 250 g/day. The two functional formulations based on moderate, and high inclusion levels are, 50 percent PKC, 30 percent grass/hay, 10 percent rice bran, 9.0 percent soybean meal, 1.0 percent premix; and 92.6 percent PKC, 2.8 percent limestone, 1.0 percent salt, 440 mg/kg Na2SO4, and 5.2 mg/kg NH4MoO4 respectively.

A study at the Ladoke Akintola University of Technology, Ogbomoso, Nigeria investigated the milk yield, composition, dam, and kid weight of lactating West African Dwarf goats fed 0, 20, and 30 percent dietary inclusion levels of PKC in a basal diet of wilted Panicum maximum, and Gliricidia sepium browse plants for a period of 18 weeks. The mean milk yield at the end of the period was found to be 138.33, 159.44, and 175.56 gday-1 respectively, while the highest values of the milk nutrients were 4.14 percent milk fat, 3.76 percent protein, 13.07 percent total solids, 8.94 percent solids-not-fat, 4.41 percent lactose, and 0.87 percent ash. The lactating goats recorded the highest average body weight change of 2.31 kg during the study period, translating to an average daily weight gain of 18.33 gday-1. Similarly, the weekly kid weights increased consistently from an initial range of 1.81 – 1.93 kg to a final range of 9.10 – 12.80 kg. They, therefore, concluded that the inclusion of 20, and 30 percent PKC in the diets of WAD goats results in better average milk yield, and kid weights than feeding only a basal diet of wilted Panicum maximum and Gliricidia sepium browse plants.

ConclusionPalm kernel meal has become an important readily available and cheap feed raw material in many oil palm processing countries. It is now routinely used in the formulation of poultry, pigs, and ruminant diets, since processes for overcoming the few challenges encountered in its utilization are now available, and relatively understood by farmers. PKC can now be included in poultry diets at 25 percent for broiler starter, 35 percent for broiler finisher, 30 percent for layer starter, 40 percent layer grower, and 35 percent for laying birds. While up to 50 to 100 percent of the maize in swine diet could be replaced with PKM without any deleterious effect on growth performance, up to 80 percent has been included in beef, and dairy cattle rations with good performance results. Small-scale farmers are also developing novel on-farm methods of improving the utilization of PKC in livestock feeding.

Bibliographic references

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