2 Why Use it? The most versatile of the citrus feeds Palatable Rich in nutrientsEasily mixed with other feed ingredientsExerts a mildly laxative effectCan be stored all-year feedingDeteriorates less in storage than many other feedsRodents and birds aren’t particularly attracted to itAn effective way to decrease waste output
5 ProcessesDuring the drying process, the water content of citrus pulp decreases from about 80% to 11% water (Grant, 2007).The drying process requires the addition of lime (quicklime (CaO) or hydrated lime (Ca(OH)2)) to neutralize the free acids, bind the fruit pectins and release water (Wing, 2003; Göhl, 1978).The mixture of fresh pulp and lime is then pressed to remove the excess moisture.The resulting liquid, rich in soluble sugars, is concentrated to make citrus molasses that can be fed to animals, sold to distillers or reintroduced in the final pulp (Rihani, 1991; Grant, 2007).Once the liquid is removed, the pressed pulp is dried in a natural gas dryer and then pelleted and cooled (European Union, 1999; Göhl, 1978; Grant, 2007).
6 Nutritional Attributes Dried Citrus Pulp (DCP) is considered an energy concentrate feed and a cereal substitute for ruminants (Arthington et al., 2002).It has a high fibre content (about 20% NDF in DM) and contains large amounts (10-40% DM) of highly digestible peptic substances and water soluble sugars (mostly sucrose) (Rihani, 1991).Rich in calcium (1-2% DM), due to the lime added in the drying process, which may triple the original calcium content (Rihani, 1991 ; Crawshaw, 2004).Its protein content is low (about 5-10% DM) as are ether extract (about 2% DM) and phosphorus (about 0.1% DM).The nutritive value of dried citrus pulp is variable and depends on many factors, the main one being the relative proportion of skins and seeds, which, among other factors, varies according to the citrus species and variety, the harvesting process and season (Rihani, 1991).
7 RuminantsDried citrus pulp is a common ingredient in ruminant diets and compound feeds throughout the world.In the tropics, it can enhance tropical beef and dairy production systems based on low to medium nutritive value grasses and other forage sources (Villareal et al., 2006).
8 Energy Value & Digestibilty Due to its relatively high digestibility (OMD in the 85-90% range) and energy value (ME about kcal/kg DM, 85-90% that of maize and comparable to barley ME), citrus pulp is used as a cereal substitute in concentrate diets (Bampidis et al., 2006;Villareal et al., 2006).Its energy is based on soluble carbohydrates and digestible fibre (Wing, 2003).Citrus pectins are easily and extensively degraded, producing acetic acid, which is less likely than lactic acid to cause a fall in pH resulting in acidosis (Wing, 2003).Due to its high fibre content, the long rumination of citrus pulp produces large quantities of saliva that has a buffering effect on rumen pH (Mertens, 2000; Faria et al., 2008).Considered to be a safer feed than cereals for animals fed high-concentrate, low-roughage diets, such as high-yielding dairy cows (Crawshaw, 2004).In rations containing low digestibility forages (hay or straw) or based on roughages such as maize silage or sorghum silage, citrus pulp seems to have a positive effect on fibre digestibility, perhaps due to a longer rumen retention time (Arthington et al., 2002;Barrios- Urdaneta et al., 2003).
9 SupplementationThe digestibility of the protein of citrus pulp is low and variable (from 37% to 70%) and, therefore, including large amounts of citrus pulp in diets containing protein-rich forages may cause a general decrease in protein digestibility (Rihani, 1991).Its low soluble nitrogen content may result in a decrease in rumen ammonia - Supplementation with urea or ammonia can be a valuable strategy. However, true protein sources can be more efficient than non-protein N (Rihani, 1991).Due to the low phosphorus content and to the Ca:P imbalance, phosphorus supplementation is an important consideration for balanced diets containing citrus pulp (Arthington et al., 2002).As citrus pulp has a low content of vitamin A, green leafy roughage is an important ingredient in rations with high levels of citrus pulp (Göhl, 1982).
10 PalatabilityThe palatability of dried citrus pulp is variable, as it may have a bitter taste due to limonin and other compounds present in the seeds and peels (Rihani, 1991; Wing, 2003;Göhl, 1978).It can result in a decrease in intake if introduced too quickly in the diet, and a more progressive introduction is recommended (Rihani, 1991; Wing, 2003;Göhl, 1978).It is well accepted by animals that are accustomed to it and can then increase intake (Rihani, 1991; Wing, 2003;Göhl, 1978).In fattening lambs, palatability decreased when diets contained more than 40% dried citrus pulp (Bhattacharya et al., 1973).
11 Dairy Cattle A valuable feedstuff for dairy cows. The extensive acetic acid production in the rumen helps maintain milk yield and milk fat content when forage is scarce (low fibre diet) or when high energy is required (e.g. as a replacement for cereals) (Arthington et al., 2002).Has no useful dietary properties other than its nutrient content (Wing, 2003).It is not a full substitute for cereals and while it does have roughage-sparing properties, it cannot be used in place of the entire roughage allowance (Wing, 2003; Crawshaw, 2004).A level of 40% of the total ration from dried citrus pulp has been considered feasible (Wing, 2003).Inclusion rates lower than 20% (diet DM) are recommended, and higher levels may alter negatively DM intake, milk parameters and diet digestibility (Belibasakis et al., 1996; Assis et al., 2004a).Inclusion at 20% DM, as a concentrate substitute in a 50-60% maize or sorghum silage-based diet does not change DM intake, milk yield or milk protein content (Belibasakis et al., 1996; Assis et al., 2004a).Feed efficiency (carbohydrate conversion) increases while maintaining the same milk yield (Miron et al., 2002).
12 ...Dairy CattleBelow 20%, neither rumen parameters nor digestibility are altered (Assis et al., 2004b).Between 20% and 24% inclusion in mixed dairy rations, rumen parameters remain unaltered but milk yield and milk protein content may be reduced, while milk fat content remains equal or increased (Leiva et al., 2000).Beyond 24% of the total diet, dried citrus pulp decreased total dry matter intake, and total dry and organic matter digestibility (Salvador et al., 2008).Early research reported that citrus pulp could cause milk taint under certain conditions, but this has not been confirmed experimentally (Crawshaw, 2004).
13 Beef Cattle & Growing Cattle A valuable feed for beef and growing cattle and can partly replace cereal energy sources.It can be safely included in rations at 20-30% of the DM (Crawshaw, 2004), but higher values are feasible.It is possible to include up to 40% dried citrus pulp in the diet of fattening cattle without altering animal health (Oliveira et al., 2002; Oliveira et al., 2005).Up to 55% dried pulp in the diets of young bulls (replacing 86% of maize grain) does not affect live-weight gain and carcass yield, though there might be a decrease in backfat thickness) (Henrique et al., 2004; Henrique et al., 2006).In beef cattle fed low-quality star grass (Cynodon nlemfuensis), increasing the amounts of dried citrus pulp up to 2.5 kg/day/animal (as fed), equal to 30% of the diet DM, reduces forage intake but increases energy intake (Villareal et al., 2006).Urinary calculi have been observed in steers fattened with rations of more than 30% citrus meal (Göhl, 1978).Citrus pulp at % of the diet is acceptable in rations for calves over two months old (Wing, 2003), but it is not recommended for younger calves because of depressed intake (Göhl, 1978).
14 Sheep - Fattening Lambs Sheep can adapt quickly to a diet containing 20% dried citrus pulp (Crawshaw, 2004).Several experiments have reported that citrus pulp can be included up to 30-40% in the concentrate diet of fattening lambs with no ill-effects on growth and carcass quality (Bhattacharya et al., 1973; Martinez Pascual et al., 1980; Caparra et al., 2007).A positive effect on feed efficiency and daily gain has been reported (Rodrigues et al., 2008).Dried citrus pulp included at 36% in a cassava flour-based diet gave higher diet digestibilities, live-weight gains and average daily gains than cassava peels, groundnut hulls and maize cobs (Aregheore, 2000).Daily weight gain is found to be maximized with 15-20% citrus pulp in the concentrate (Martinez Pascual et al., 1980).Rates above 30% can decrease digestibility (Göhl, 1978).Higher rates (more than 40-60%) resulted in overall performance decreasing and an increase in the severity of rumen parakeratosis (Martinez Pascual et al., 1980; Rodrigues et al., 2008), and lower palatability (Bhattacharya et al., 1973).
15 EwesInclusion of 30% citrus pulp in the concentrate given to lactating ewes fed alfalfa hay and straw did not affect milk yield and milk composition) (Fegeros et al., 1995).Another experiment reported that replacing 33% to 100% of barley with citrus pulp in diets based on ammoniated straw resulted in a linear decrease in milk yield, but not milk composition, and a lower daily weight gain of lambs (Castrillo et al., 2004).
16 GoatsIn male goats, supplementation with dried citrus (lemon) pulp and urea of a diet based on barley straw and alfalfa hay increased DM intake and apparent dry matter digestibility of the straw (Madrid et al., 1997).However, a later experiment showed that digestibility decreased when a supplement of 300 g/day/animal was given (Madrid et al., 1998).In growing kids, replacing maize grain with 40% citrus pulp gave the best daily weight gain, DM intake and feed conversion while higher levels were thought to have deleterious effects on mineral metabolism (Bueno et al., 2002).Dry citrus pulp can also be incorporated into goat rations as a dry season supplement to foliage from leguminous browse plants (Enterolobium cyclocarpum), replacing up to 50% of the concentrate (dried brewer's grains) (Oni et al., 2008).
17 PigsCitrus pulp is bulky and more fibrous than cereals and therefore less valuable in pigs than in ruminants (O'Sullivan et al., 2003).The presence of limonin-containing pips may be a limiting factor and citrus pulps from seedless fruits could be more usable than pulps containing seeds (Crawshaw, 2004).Sows seem to be more able to digest citrus pulp than growing pigs (Crawshaw, 2004).
18 Growing PigsDried citrus pulp may be included at up to 5% in the diet of growing pigs (O'Sullivan et al., 2003).Higher rates can adversely affect growth rates (O'Sullivan et al., 2003; Baird et al., 1974), feed conversion efficiency and carcass yield (O'Sullivan et al., 2003).However, another experiment reported that up to 15% citrus pulp had no unfavourable effects on digestibility and energy value provided that phosphorus and vitamin D were added (Nicolakakis et al., 1999).In many case, serious health problems (anorexia, locomotion problems, hyperthermia, erythema) have been reported at a 15% inclusion rate (Santos et al., 2002) suggesting caution should be excercised when rates higher than 10% are used.
19 SowsDried citrus pulp may be included at up to 20% and 15% in the diets of pregnant and lactating sows respectively, without affecting reproductive performance, sow body weight, piglet weight at birth or at weaning and voluntary feed intake (O'Sullivan et al., 2003).Another experiment reported using up to 50% citrus pulp in gestating and lactating sows without deleterious effects on performances and productive indices (Sotto et al., 2009).
20 BroilersLevels between 5% - 10% of citrus pulp in the diet increased soluble non-starch polysaccharides and led to impaired growth rates, lower feed efficiency and reduced carcass yields.The 10% level changed fatty acid profile of the meat, depressing monounsaturated fatty acids and palmitic acid and increasing the predominance of n-6 and n-3 polyunsaturated fatty acids (Mourao et al., 2008).’Dried citrus peels improved final live weight and live-weight gain up to 7.5% inclusion, and reduced serum cholesterol concentration (Chaudry et al. 2004).Sun-dried sweet orange rinds collected from retailers of peeled oranges could be used to replace up to 15-20% maize (about 7-9% of the total diet) in the diet of broilers without any adverse effect on performance (Oluremi et al., 2006; Agu et al., 2010).A summary of earlier experiments reported the 7.5% inclusion rate in the diet as the most favourable (El Boushy et al., 2000).
21 Laying HensA 5% inclusion rate seems to be safe in laying hens (El Boushy et al., 2000), but higher rates have been suggested.10% dried citrus peel in the diet of laying hens had no significantly adverse effect on feed intake, egg production, and egg weight (Yang et al. 1985).A level of 12% dried citrus pulp in the diet did not affect performance and egg quality of laying hens in the early stage of production (Nazok et al., 2010).A diet with 15% citrus peels decreased feed efficiency and gave darker egg yolks (Yang et al ).
22 QuailsUsing up to 6% dried citrus pulp in diets for laying quails had no significantly adverse effects on performance (Florou-Paneri et al., 2001).
23 RabbitsDried citrus pulp is a good ingredient for rabbit feeding with a nutritive value of about kcal/kg (as fed) and can be included at 20-30% of the diet (Hon et al., 2009; de Blas et al., 1990; Pereira et al., 2005; Papadomichelakis et al., 2002; Papadomichelakis et al., 2004).In one experiment, a 25% inclusion of dried citrus pulp was found to be economically beneficial compared to the traditional diet (Leon et al., 1999).No mortality or distress was recorded at 25% inclusion (Hon et al., 2009).Dried citrus pulp can also totally replace alfalfa meal as a source of fibre in the diet of rabbits enhance live-weight gains (Coloni et al., 2009).Rabbits fed citrus pulp (up to 51.5 g/day), similar to that had caused severe health issues in cattle, did not show signs of poisoning or other symptoms (Tokarnia et al., 2001).
24 FishUse of dried citrus pulp as part as fish diets has been reported in several fish species:Nile tilapias (Oreochromis niloticus): dried citrus pulp with addition of a probiotic (Saccharomyces cerevisiae) can replace up to 10% of maize grain in Nile tilapia fingerling diets without any adverse effects on growth parameters, nutrient digestibility or their immune status (El-Sayed et al., 2010).Tambaqui (Colossoma macropomum): citrus pulp was included in a complete diet containing meat meal, soyabean meal, maize starch and maize oil (Macedo-Viegas et al., 1996).Orange koi carp (Cyprinucarpio leanneanus): ground and sun-dried peels of sweet oranges were acceptable (Ipinjolu, 2000).Rohu (Labeo rohita): dehydrated fruit processing wastes can be safely used at a level of 25% in the diet. Pineapple wastes had a significantly higher growth promoting effect in fingerlings compare to sweet lime and orange wastes (Abani Deka et al., 2003).