Effect of supplementing Moringa oleifera essential oils on milk quality and fatty acid profile in dairy sheep

The milk of sheep is used almost entirely for making cheese, yogurt and other dairy products (Pulina et al., 2006) due to its higher  protein and fat content compared to milk of cow and goat (Rouissiet_al2008). For this reason, the relationship between the nutrition of the sheep and the quality of the milk is mainly assessed in terms of its technological properties and coagulation, which are significantly affected by the milk fat and protein concentration (Pulina et al., 2005). For dairy sheep, milk production is dependent on the level of food and the quality of the components of the ration (Bocquier and Caja, 2001).
       
Moringa is native to India but is now cultivated in all tropical and subtropical regions of the world (Rajangam et al., 2001). This sturdy tree does not need a lot of water, it is grown in the mountains region, but it adapts to the arid climate and resists heat. It is characterized by rapid growth and can reach 12 meters in height during the first three years of growth (Yang et al., 2006).
       
Moringa is known for its medicinal benefits. Its leaves are rich in vitamins minerals and proteins. The leaves as well as the fruits of this tree are used to cure several diseases such as hypertension, diabetes, rheumatism, or back pain. It could also serve to combat desertification. Little information about the use of Moringa oleifera as a protein source in the diet of ruminants is available. In this context the purpose of this study was the assessment of the effects of doses administered by the oral route of essential oils of Moringa oleifera on the quantity and quality of the milk.

Twenty-four Sicilo-Sarde ewes were divided into three homogeneous groups (8 animals per group), with body weight (Kg) 42.3 ± 3.2 kg as control (C) group ; and 43.5 ± 2.8 kg (O-M1) and 42.9 ± 3.5 kg (O-M2) as treatment group. The number of lactation was 1.9 ±0.5; 2.1± 0.8; 2.1 ± 0.6 for the control, O-M1 and O-M2 groups respectively. Ewes of  all three groups received a ration of oats hay along with  500 g/ewe/day of concentrate feed. Ewes of the treatment groups (O-M1 and O-M2) received 0.3 ml and 0.6 ml of Moringa oleifera essential oils respectively administered by the oral route in the morning daily. Water was available for ad libitum consumption. The Moringa oleifera EO was obtained from Moringa oleifera plant cultivated in experimental plot at Higher agriculture School of Mogran Tunisia. The ration was divided and distributed in two meals per day. The chemical composition of oat hay and concentrate feed were analyzed according to the AOAC (1990) (Table 1).
 

       
Milk samples were collected after two weeks of adaptation period to the diets and experimental conditions. During eight weeks, ewes were hand milked twice a day in the morning and evening at 07:00 and 15:00 UTC+01:00. Individual milk yields were recorded, once a week, in the morning and evening milking. Two aliquots of each individual milk samples were composed by unifying amounts of morning and evening milk in proportion to respective yields and were collected for analyses of physicochemical and fatty acids by the Lactoscan. Fatty acids profiles were measured using gas chromatography (Shimadzu, GC-14 A), lipids extraction was performed by the Folch method Folch et al., (1957). The chromatograph was equipped with a split/split less injector and a flame ionization detector. The methyl ester separation was carried out on capillary column HP INNOWAX 250 (30 m × 0.32 mm i.d) with film thickness about 0.25 μm. Injector and detector temperature was 220° C. The oven temperature was programmed as: initial temperature of 45°C maintained for 5.0 min, then rose to 190°C at 7°C/min and held at 190°C for 30 min. Fatty acids were identified by comparing with the retention times of fatty acids in standard samples.
       
All data were subjected to statistical analysis by the mixed procedure (SAS, 2000). The method of orthogonal contrasts determines the comparison between averages. The following contrasts have been used:
 
Contrast 1 (Cst 1): Effect of Moringa EO presence (C vs. O-M1 + O-M2)  
Contrast 2 (Cst 2): Effect of Moringa EO dose (O-M1 vs.O-M2)

The average amount of ingested oat hay was respectively 1140; 1200 and 1180 g DM/ewe/day for the groups C; O-M1 and O-M2 without significant difference between the average (P>0.05). This trend appears in the fork of the capacity of ingestion of the ewes during the milking phase (Rouissi et al., 2008). Indeed, the dose of essential oil of Moringa oleifera does not affect the basal diet quantity ingested, which corroborates with the results of Smeti et al., (2018).
       
The production of milk and its physicochemical composition are grouped in Table 2. The amount of milk (ml) produced was 517 for the control group and 572; 598  respectively for the experimental groups (O-M1 and O-M2) with a significant difference between the average (P<0.01). The supplementation of the essential oils of Moringa oleifera has increased the production of the milk, as well as the dose has a significant effect (O-M1 vs. O-M2). However, the effect of the essential oils of Moringa oleifera on the level of milk production converges with the results of Kholif et al., (2018). This trend can be explained by the fact that the use of essential oil increased the practical application of food by microbes in the rumen and minimize the losses of energy and protein during the rumen fermentation and therefore draw profile of the quality of the food thus engendering the increased e production of the milk (Matloup et al., 2017). 
 

       
The incorporation of EO of Moringa has profoundly increased the milk fat (%) in supplemented groups (P<0.01), which was similar to the results of Pulina et al., (2006) and Debashis et al., (2009). According to Kholif et al., (2018), the observed greater milk fat content with M. oleifera extract could reflect enhanced fiber digestibility.
       
The urea nitrogen concentrations were 46.7; 42.2 and 36.4 mg/dl, respectively for the groups C; O-M1 and O-M2 with a significant difference (P< 0.01). This corroborates with the results of Smeti et al., (2018), which can be explained by the decrease in the concentration of NH3-N in the rumen. The physical criteria of the milk (pH, density and freezing point) were not affected by the incorporation of essentials oil of Moringa oleifera.
       
The supplementation of essential oils of Moringa oleifera had affected the proportion of fatty acids (P<0.01) (Table 3). The proportion of saturated fatty acids was 75.01; 72.48 and 70.1 g/100g of total fatty acids with significant differences between them (Table 3). This corroborates with the results of Kholif et al., (2016) on the Nubian goat in lactation, conversely to the polyunsaturated fatty acids which are in favor of the (O-M2) group.
 

       
Milk fatty acid proportions of unsaturated fatty acids (UFAs), mono UFA (MUFAs), total conjugated linoleic acids (CLA), and UFA/saturated fatty acids (SFAs) ratio were higher (P<0.05)  for ewes of group (O-M2). This result was similar Kholif et al., (2018) who attributed this finding to the effect of some active compounds present in the extract of Moringa oleifera on ruminal fermentation.
       
The proportions of CLA produced in milk depend mainly on the diets that are fed (Kim et al., 2016). This can be explained by use of food by microbes in the rumen and the modification of the proportions of acetate and propionate in the rumen which reflects on the proper digestion of the fibers in the presence of Moringa oleifera in the ration (Belhi et al., 2018). Furthermore, the inhibition of the ruminal biohydrogenation of unsaturated fatty acids of food origin in the presence of essential oils by inhibiting growth of some bacteria involved in this process (Kholif et al., 2012).