Effect of concentrate supplementation to free ranging dromedary camels on yield, physicochemical quality and fatty acid profile of milk

Moges Dereje, Mengistu Urge, Getachew Animut¹, Mohammed Y Kurtu and Sisay Tilahun²

Haramaya University, College of Agriculture and Environmental Sciences, School of Animal and Range Sciences, P.O. Box 138, Dire Dawa, Ethiopia
mogesdr@yahoo.com
¹ Agricultural Transformation Agency, P.O.Box 708, Addis Ababa, Ethiopia
² Ethiopian Institute of Agricultural Research, P.O.Box 2003, Addis Ababa, Ethiopia

Abstract

The effects of supplementation on yield, physicochemical quality and fatty acid profile of dromedary camel milk were investigated for a period of 120 days. Eight multiparous healthy camels just after early lactation were randomly allocated to one of four treatments in a double 4x4 Latin Square design. The supplementary concentrate feed was prepared from a mixture of wheat bran, sorghum grain, noug (Gizotia abyssinica Cass.) seed cake and mineral-vitamin premix. The experimental dietary (D) treatments were browsing/grazing only (D0), browsing/grazing plus 0.25 kg concentrate feed per kg milk (D0.25), browsing/grazing plus 0.50 kg concentrate feed per kg milk (D0.5) and browsing/grazing plus 0.75 kg concentrate feed per kg milk (D0.75).

Camels that consumed D0.75 had superior body weight gain (BWG) and body condition score (BCS) compared to those fed D0, D0.25 and D0.5. Camels fed D0.5 and D0.75 had higher milk yield and milk fat content than D0 and D0.25. There were no differences among treatments in protein, ash, solid not fat (SNF), pH, acidity and specific gravity of the milk. There were no differences among the FA categories, the concentrations of which were in the order of SFA > MUFA > PUFA and LCFA>MCFA. The top to bottom sequences of the four abundant FAs of the camels’ milk were oleic, palmitic, stearic and myristic acid. Camels fed with D0.75, D0.5 and D0.25 produced milk with higher palmitoleic acid than unsupplemented camels. 

Key words: atherogenesity, body condition score, browsing

Introduction

Camels in Ethiopia are important livestock species that significantly contribute to the livelihood of the pastoralists and agro-pastoralists in the arid and semi-arid areas as well as to those living in the neighborhoods of the dry lands. The comparative advantage of the camel over the other species in the arid and semi-arid environment is its natural ability to produce milk, meat, fiber, and draught power in areas where other animals are less able to produce and reproduce (Hashi 1984; Knoess et al 1986). According to Epstein (1971) and Yagil (1994) camels were primarily domesticated for milk and are widely recognized to produce more milk and for a longer period of time than any other milk animal held under the same environment (Kaufmann and Binder 2002). Similarly, Knoess et al (1986) noted that in Punjab (Pakistan) well-fed dromedary camels produced more milk than high-merit exotic cattle and their crosses. Thus, the efficiency of the camel should be appreciated in terms of its productivity, its superb adaptation to the harsh environment, sustainability of production across seasons and accessibility to people living in areas not or less suitable for food crop production.

However, due to climate variability and frequent drought (Cossins and Upton 1988), the nomadic system, which was utilized by camel herders for centuries is no longer an efficient system for camel production and is being replaced by sedentary systems in many parts of camel rearing regions of the world (Schillhorn Van Veen and Leoffler 1990). Consequently, the heterogeneous range forages that used to serve as sources of good camel feed have decreased. This has led to reduced number of nutritious range species, and inadequate supply of feed in terms of biomass and quality. As such, feed becomes the most important single factor affecting productivity of camels (Yagil 1994). Hence, camel husbandry in general and feeding in particular must be transformed to adapt to the changing environmental and socio-economic situation of the pastoral and agro-pastoral system so as to maximize the benefits that can be obtained from camels. Under such changing circumstances proper feeding of camels might entail employing supplementation of locally available feeds to enhance the productivity of the animal. The objective of this paper was, therefore, to investigate the effects of supplementation on the milk yield, milk quality and milk fatty acid composition in free ranging dromedary camel.

Materials and methods

Study site

The study was conducted at Haramaya University Camel Research Station, Erer Guda, Easter Ethiopia, from September to December, 2012. The site is located at an altitude range of 1300 to 1600 m above sea level, and at 9^o14′ N latitude and 42^o14′ E longitude. The soils are sandy-dry-loam with some alluvial nature in the seasonally flooded and riverine areas. The rainfall pattern is weakly bi-modal with two peaks, one in March and April and the other in July to September. Relatively short dry season is in May and June while the long dry season is from October to February. The rainfall is very variable in its spatial and temporal distribution with an annual precipitation ranging from 400 to 500 mm (Tamire 1986). The agro-ecology of the area ranges from semi-arid to arid condition and the temperature ranges 17 to 31^oC.

Animals and management

A total of 8 multiparous camels just after their early lactation were obtained from Haramaya University camel research herd and pastoral camel herds residing nearby the University farm in Erer Guda village. Animals were selected on the basis of normal body and udder conditions (with no blind teats) and good temperament (docile). Experimental camels were quarantined for 3 weeks. During this period they were weighed using weighing bridge, condition scored, ear tagged, de-wormed against endo-parasites with a broad-spectrum anti-helmentic (albendazole), and sprayed against ecto-parasites with acaricides (vetacidin 20% EC) and vaccinated for pasteurelosis and anthrax based on the recommendation of veterinarians. During the 2 weeks after quarantine, all animals were given access to the supplementary feeds starting with small quantity at the beginning and ending up to the full recommended amount of feed per day. During the experimental period, camels were observed routinely for any abnormalities, de-wormed against endo-parasite at an interval of three months and sprayed against ecto-parasiteevery week as prophylactic measures. As a precaution against health risks, rectal temperature was taken twice a week to observe for any sub-clinical symptoms of diseases.

Experimental feeds and feeding management

At the beginning it was planned to include urea treated maize stover as part of the experimental feed, but the camels refused to consume since they get sufficient fresh range forage from the grazing fields. Thus, the supplementary feed was composed of wheat bran (60%), sorghum grain (27%), noug (Gizotiaa byssinica Cass.) seed cake (12%) and mineral and vitamin premix (1%). All experimental animals were browsing during day time between 0700 and 1730 hours and corralled individually during night time. The camels obtained water in the grazing range. All animals were fed with the experimental feed in individual pens for an adjustment period of 2 weeks and for the rest of the study period. The supplementation was offered to the animals at 0600 and 1800 hours.

Experimental design and treatments

The experimental camels were assigned randomly to one of the four dietary (D) treatments, namely browsing only (D0/no supplement), browsing plus 0.25kg of concentrate feed per kg milk (D0.25/low level), browsing plus 0.50 kg of concentrate feed per kg milk (D0.5/medium level) and browsing plus 0.75 kg of concentrate feed per kg milk (D0.75/high level).A double 4 x 4 Latin Square design forming 4 x 8 rectangles (Mead et al 1993) was used for the experiment. At the end of the quarantine period, the animals were randomly allocated to one of the treatment diets. Fourteen days of adaptation period in between each treatment were employed to eliminate the carry over effects of the previous treatment followed by a 7 day measurement period. Thus, each treatment period had a duration of 21 days which made a total of 84 actual data collection days.

Data collection procedures and measurements

Body weight and condition score

Body weights (BW) of the camels were measured using weighing bridge (TRU-TEST, made by Tru-Test Limited, Auckland, New Zealand. www.tru-test.com) while body condition scores (BCS) were assessed in scale of 0 to 5 (0=Emaciated and 5=Obese) according to the procedure described by Faye et al (2001). Initial body weights of all camels were recorded on the first day of the experiment and subsequent body weight measurements and condition scores were taken at 3 weeks interval (at the end of each period) before the morning meal. The mean total weight gains were calculated as differences between the final and the initial weight of each camel.

Milking and milk yield

Milking was done regularly by the same person every morning at 0600 and evening at 1800 hours. Calves were allowed to suckle the left or right side teats at each milking on alternate days. Milking was conducted by hand and the amount of milk obtained from the two teats not suckled was multiplied by two to estimate the daily milk yield of each camel (Simpkin 1996). Energy corrected milk (ECM) was calculated using the equation of Anderson et al (2007) as; ECM= (milk yield * 0.3246) + (fat yield * 12.86) + (protein yield * 7.04). Calves were corralled separately from their dams during the night and they remained at the corral during the day.

Milk sampling

Representative milk was taken from each animal once at the end of each period (every 21 days). Morning and evening milk samples were pooled in a container and thoroughly mixed. Milk samples were taken into clean and tightly closed sample bottles (100 ml) by using plungers and dippers and put in ice packed cool boxes for milk composition (fat, protein, lactose, ash), physical quality and fatty acid profile determination. The samples, after arrival from the field, were kept in a refrigerator at -20^oC until laboratory analysis.

Feed Analysis

The supplement feeds were analyzed according to the procedures of AOAC (1990) for dry matter (DM), crude protein (CP), ash, organic matter (OM), ether extract (EE) and crude fiber (CF). Acid detergent fiber (ADF) was determined according to Robertson and Van Soest (1981) and neutral detergent fiber (NDF) according to the procedure of Van Soest et al (1991). Metabolizable energy (ME) was calculated according to Ellis (1980) and nitrogen free extract (NFE) according to Dhont and Berghe (2003).

Milk Analysis

Duplicate milk samples were analyzed for protein, lactose, fat and total solid (TS) content by an infrared technique (LactoScope Delta Instruments BV, The Netherlands). Solids not fat (SNF) contents were determined by difference between total solids and fat of the milk. Ash was determined following the method of AOAC (1990). The pH of milk was measured using portable digital pH Meter (Model Jenway 3051 ELE International, Made in the UK) standardized at pH 7. The temperature was adjusted to 20^οC before pH measurement (Marth 1978). The pH Meter electrode was immersed into the well mixed milk samples and the pH readings were taken when stable. The electrode was rinsed with distilled water between each immersion into the sample. Titratable acidity (TA) expressed as % lactic acid was measured by titration of 9 ml of milk sample with N/10 standard sodium hydroxide solution to a faint pink color using phenolphthalein as indicator (Marth 1978). Specific gravity of the milk samples was determined by Lacto-densimeter (Quevenne’s type Lactometer). To convert the true lactometer (⁰L) reading to density (g/ml), 1.0 was written in front of the true lactometer reading.

Determination of fatty acid composition of the camel milk

Milk fat was extracted according to the method described by ISO 14156:2001(IDF 172:2001). Extracted fat was converted to corresponding fatty acid methyl esters (FAMEs) using methanolic solution of potassium hydroxide (2 mol/L KOH in methanol and hexane) (trans-esterification) following the procedure of ISO 15884:2002 (IDF 182: 2002). Then the FAME samples were put into Gas Chromatograph (GC) vials and stored at -20°C until fatty acid (FA) profiles were determined by Gas Chromatography Mass Spectrometry (GC-MS) analysis using HP 5890 series GC equipped with mass selective detector (MSD), HP 5972 series (German). The FAs were identified on the basis of comparison of their retention time and computer matching with WILEY 275 and National Institute of Standards and Technology (NIST3.0) libraries provided with computer controlling the GC-MS system, in Addis Ababa University, Ethiopia. The spectra of the unknown components were compared with the spectra of the known components stored in the library and named. The individual FAs expressed as a percentage of total FAs were grouped as saturated fatty acid (SFA), unsaturated fatty acid (UFA), monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), short chain fatty acid (SCFA), medium chain fatty acid (MCFA) and long chain fatty acid (LCFA). Finally, PUFA: SFA, MUFA: SFA, UFA: SFA, LCFA: SCFA and LCFA: MCFA ratios were computed.

Determination of index of atherogenisity (IA) of FAs:

IA = aS12 + bS14 + cS16/dP+ eM+ fM

where: S12 = C12:0, S14 = C14:0 and S16= C16:0; P = sum of ω6 and ω3 PUFA; M= oleic acid and M= sum of other MUFA. a–f are empirical constants: b = 4 and a, c, d, e and f are equal to 1.

Iso fatty acids were not included in the calculation. So, the final calculation of the IA of the current camels’ milk was:

(C12:0 + (4*C14:0) + C16:0)/(C10:1 + C14:1 + C16:1 + C17:1 + C18:1 + C18:2.

Statistical analyses

Data were analyzed by using one way analysis of variance procedure of SAS software (SAS 2008) with a model: Y_ijk = μ + p_i + c_j + t_k + eijk, where Y_ijk: dependent variable, μ: overall mean, p_i: effect of period, c_j: effect of camel, t_k: effect of supplement, and eijk: residual effect. Differences between treatment means were separated using Duncan’s multiple-range test (Duncan 1955) at P < 0.05.

Results and discussion

Chemical composition of the feeds

Nutrient composition of ingredients used for the formulation of the experimental supplement diet (Table 1) were within the range reported earlier from our laboratory and elsewhere (Mekasha et al 2011; Hirut 2008; Getahun 2014; Gebeyehu et al 2015; Firisa et al 2013). Sorghum grain and wheat bran contain comparable ME followed by noug seed cake. Good sources of readily fermentable energy source, such as sorghum grain, are very important for efficient rumen microbial protein synthesis (Van Soest 1994) and thereby for better milk production and composition. The concentrate mix, as expected, had moderate source of CP and ME. The ME content of the supplementary diet used in the present study was higher than that suggested by Hashi and Kamoun (1995) (10.5 MJ ME) but the CF and ADF values were lower than 17% and 21%, respectively, recommended for dairy cattle of similar production status to the lactating camel used in this study.

Body weight and body condition score

In Table 2, positive response of the camels for supplementation was shown in the form of BW and BCS gain. The BW gain of animals that consumed D0.75 was higher compared to the other three diets. Similarly, groups fed D0.75 and D0.5 exhibited superior BCS gain than the D0 and D0.25 groups. These results indicated that high level supplementation of lactating camels can improve BW and BCS gain. This could be for the reason that the start of the current experiment was just after early lactation stage (first 6 weeks after parturition) of the camels during which positive response of BW and BCS gain could be achieved for concentrate supplementation. This idea is supported by the report of Roche and Holmes (2007) stating that dairy cows in early lactation have physiological drives which give priority to mobilize  energy resources to lactation instead of body condition. As a result, supplementation can have positive effects on BCS gain if it is given after early lactation period. The reports of Biwott et al (1998) and Horan et al (2005) also dealing with lactating dairy cows indicated BW and BCS improvements are common when animals are supplemented with concentrate feed after early lactation stage.

One of the effects of improved body condition of lactating animals is improved reproductive performance. In this regard, Pryce et al (2001) reported strong relationship between BCS and fertility in dairy cows. Bohnert et al (2013) also noted that beef cows with higher body condition score showed better reproductive performance as expressed by higher pregnancy rates than the low body condition score cows. During the present study, it was observed that six out of the eight lactating camels were showing heat signs (sexual desire) within 6 months of parturition. This present observation was supported by Arthur and Al Rahim (1982) and Yagil (1985) who reported that in the tropics it is possible that camels kept under high levels of nutrition and management would show oestrus and rutting throughout the year. Camels in the arid environment, including the camels in the neighborhood of the current research site, usually come into heat after one year of parturition (Khanvilkar et al 2009) during the next breeding season which coincides with feed abundance period. The current observation on the experimental camels was not common in un-supplemented lactating camels. Thus, the result may indicate that supplementation might play a positive role in improving the existing poor reproductive performance of camels in pastoral areas of Ethiopia.

Milk yield and chemical quality

Lactating camels showed a considerable increase in milk yield and quality in response to supplementation (Table 3). The camels produced more milk when they consumed supplement in amounts of 0.5 and 0.75 kg per kg milk. This could be an attribute of concentrates supplementation which promoted better DM digestibility. A higher intake of concentrate provides an increased synthesis of propionic acid, which serves as a precursor for glucose synthesis. Glucose in turn is related to the synthesis of lactose, which is partly responsible for the increase in the volume of the milk produced (Costa et al 2009). Bhattacharya et al (1988) also reported increased milk production in grazing Saudi camels supplemented with barley and lucerne forage. According to the report by Khan and Iqbal (2001), Pakistani camels positively responded to supplementation by producing 9.1–14.1 kg of milk per day. In a study conducted by Knoess (1977) on seven un-supplemented Ethiopian camels, mean daily milk yield was 6.6 liters, which was lower than the mean (10.5liters) for supplemented camels of the current study showing that supplementation increases milk yield significantly. The higher milk yield obtained when camels are supplemented will make more milk available both for family consumption and the calf. This condition in turn will reduce the competition for milk and increase calf survival which can have a positive effect on overall herd productivity.

Milk fat content was higher when animals were supplemented with 0.5 kg concentrate per kg milk than 0.25 kg and grazing only. This result could be attributed to the fat content of the supplement. Kellaway and Harrington (2004) and Lima et al (2011) mentioned that supplementation increased milk fat content due to the role of the dietary fat in the synthesis of milk fat in the mammary glands. In agreement with the present report, Moges and Uden (2005b) noted that grazing Ogaden camels produced more milk with higher fat when supplemented with protein- and energy-rich concentrate than only grazing/control group. The results of the chemical composition of the camel milk in the current study were well within the range reported by Khan and Iqbal (2001). Increased milk solids and reduced moisture content when animals are supplemented, as in the current study, also were reported in earlier works for camel (Soliman 2009), and other species such as goat (Min et al 2004) and cattle (Madnyawu and Madzudzo 1995).

Physical quality

Concentrate supplementation did not influence milk acidity, pH and specific gravity (Table 4). El-Hatmi et al (2004) also reported absence of significant differences between Tunisian camels offered with low (1kg/day) and high (4kg/day) levels of concentrate supplement in pH, specific gravity and acidity values. These physical qualities of the camel milk in the current study were within the ranges reported by Adugna et al (2013) for eastern Ethiopian camels kept on grazing/browsing on natural range lands. Dowelmadina et al (2014) found similar values for Sudanese camels kept on range grazing/ browsing.

Fatty acid composition

Supplementation did not affect the levels of FAs (Table 5) except for the concentration of palmitoleic acid (C16:1cis9) which was higher for the supplement treatments than the control. This could be due to the action of the enzyme desaturase, which is responsible for the conversion (desaturation) of the saturated palmatic acid (C16:0) into its corresponding monounsaturated palmitoleic acid (C16:1cis9) (Lima et al 2011).  

There were no differences among the FA categories (SFA, MUFA and PUFA). This is in contrast with the study of Faye et al (2008) on camel (Bactrian and dromedary), cow, goat and mare milk, for which higher values of SFA than MUFA were reported, indicating this to be an expected result for many species. PUFA accounted for a much lower proportion of the FA than SFA and MUFA, which is in agreement with the result reported by Faye et al (2008) in supplemented dromedary camels.

There were no differences among the dietary treatments with regard to MCFA and LCFA. The SCFAs (<C6:0) were not found. The chain length based categories were in the order of MCFA (C6:0-C12:0) < LCFA (C14:0-C20:0), which is similar to that reported by Jonák and Fialová (2009). Camel milk fat contains higher LCFA than other mammalian milk fats (Konuspayeva et al 2008). The lower proportion of MCFA and the higher proportion of LCFA observed in camel milk in the present study is in line with the result reported by Park and Haenlein (2006) for unsupplemented camels.

The high ratio of UFA/SFA in the milk supports the previous perception that camel milk has a beneficial effect in lowering blood cholesterol level in humans (Faye et al 2008; Konuspayeva et al 2008),due to the lower content of SFA. The mean ratio of UFA/SFA of the current study (0.65) is well above the minimum recommended value (0.4) suggested by Wood et al (2003). The mean ratio obtained in the present experiment was also higher than the values of 0.45 and 0.43, respectively reported for milk of  unsupplemented Bactrian and dromedary camels (Konuspayeva et al 2008).  The high ratio of the UFA/SFA in the current study could be one of the unique aspects explaining the beneficial value of diet modulated camel milk in human nutrition and health (Faye et al 2008; Konuspayeva et al 2008).

The index of atherogenecity (IA) is another factor verifying the healthy quality of camel milk. The IA is highly associated with the onset of coronary heart diseases (CHD). High value of IA indicates the high risk of cardiovascular disease resulting from lipid intake (Ulbricht and Southgate 1991). The mean IA of the camel milk in the current study (1.70) was much lower than in cows’ milk, which ranged from 3.3 to 3.5 in the study of Chilliard et al (2001) and in the camel’s milk reported  by Konuspayeva et al (2008) which was 2.7.

Conclusions

• Supplementation resulted in:  higher average daily milk yield and fat content; and in better body condition score and reproductive performance.

Acknowledgements

The first author is grateful to SIDA Haramaya University project PhD Scholarship Program for sponsoring the study. Haramaya University and Ethiopian Institute of Agricultural Research are also acknowledged for partial support of the project.

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Received 19 March 2016; Accepted 16 April 2016; Published 2 June 2016

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