Production , quality and fatty acid composition of milk of Serbian White goat

This paper investigates the duration of the first and the second lactation, total and daily milk yield and chemical composition in Serbian White goat. Standard examination methods were used. Total and daily milk yields were significantly higher in the second lactation. Total solids, fat, lactose, crude protein, casein, serum protein and ash content in both lactations were similar and did not show statistically differences. Saturated fatty acid (SFA) content was 70.92 % in the first lactation and 72.01 % in the second; unsaturated fatty acid (USFA) content was 26.73 % and 23.50 %, respectively. Unsaturated and saturated fatty acid relation was 0.38 in the first lactation and 0.33 in the second; polyunsaturated (PUFA) and monounsaturated fatty acid (MUFA) relation was 0.13 and 0.13, respectively. It was concluded that Serbian White goat in half-intensive breeding system can produce milk of good quality for consumption as well as good raw material for cheese production.


Introduction
Goat milk is topic of interest in the recent years.Milk composition has fundamental importance for its nutritive and marketing value, as well as for its technological characteristics (HAENLEIN 2004).It depends of endogenous (breed) and exogenous factors (feeding, season variations, age, oestrus, pregnancy, body weight, lactation phase and number of lactation, environmental conditions and health) (PARK 1990, ANTUNAC et al. 2001a, b, WOJTOWSKI et al. 2001, WALISIEWICZ-NIEDBALSKA et al. 2004, STRZALKOWSKA et al. 2004, GUO et al. 2004, BöMKES et al. 2004, PALA and SAVAS 2005, STRZALOWSKA et al. 2004, MEMISI et al. 2007).
Variability of amount and chemical composition of milk are under influence of dominant genetic background (55 %), while other variations (45 %) are influenced by paragenetic factors (feeding).
One of the most important components of milk is fat.Milk fat is composed mostly of triacylglyceroles (98 % of total milk lipids).Fatty acids with short and medium chain (C4-C10 and C12-C16) present approximately 30 % of milk fat.Long chain fatty acids are originated from the feeding stuffs and make 40-60 % of milk fat, depend of the type of feed (WALISIEWICZ-NIEDBALSKA et al. 2004, STRZALKOWSKA et al. 2006).About 50 % of the fatty acids presented in milk fat are synthetized by mammary glands, while the second part present fatty acids from blood.
Fatty acids, particularly C6:0-C10:0 influence the development of desirable sensoric properties of milk (GUO et al. 2004).Presence of desirable odor and taste in cold, fresh goat milk is the result of increase of free fatty acids C6:0-C9:0 and branchy chain fatty acids C9 and C10 (methyl-and ethyl-C8) that are more significantly represented in milk of small ruminant in regard to cow milk (DELACROIX-BUCHET and LAMBERET 2000).
Fatty acids are of particular therapeutic importance due to its specific metabolism and have use in the therapy of some metabolic diseases (HAENLEIN 2004, CHILLIARD andLAMBERET, 2001).
On the base of earlier investigations (ZUJOVIC 1993, ZUJOVIC et al. 1998) it was found out that domestic White goat bred in Serbia presents the population of expressed genetic background for milk yield.Due to its characteristics and because of importance in nutrition this race breed has gain the popularity for breeding in Serbia.
The aim of this paper was to investigate the milk production in the first and the second lactation, chemical composition and fatty acid composition of Serbian White goat.

Material and methods
In this experiment, the milk of Serbian White goats was examined.Goats were breeding semi-intensive (pasture and indoor system) in area of Stara Planina (Old Mountain) in the southern Serbia at 600-750 m altitude.It were examined 293 goats in the first lactation and 219 goats in the second lactation.The number of samples for chemical examination was 12 (Samples of milk were collected from 12 households.One sample for chemical examination was represented as total quantity of milk from one household milked for one day).Milk samples for chemical examination were taken every three week.During investigation goats were clinically healthy.After milking, milk was refrigerated at 4 °C and before examination heated at 40 °C.
Milk yield was controlled every day during the both lactations and measured by scale with accuracy 10 -3 kg.
Total solids were obtained after drying to constant weight at 102 °C.Fat content was determined by the butyrometric Gerber method with a calibrated butyrometer (ISO 11870:1991).Total nitrogen, non-casein nitrogen (NCN) and non-protein nitrogen (NPN) were determined by standard procedures using the Kjeldahl method.Casein nitrogen was calculated as the difference betwen total nitrogen and NPN (multiplied by a conversion factor of 6.38) and serum protein as the difference between NCN and NPN (multiplied by a conversion factor of 6.38).Lactose was measured by infrared analysis using the Milkoscan apparatus according to the IDF method (IDF 141B:1996).Ash was determined by weight after burning at 525 °C.
Obtained data were statistically analyzed by calculating of mean value, standard deviation, coefficient of variation, as well as range.The differences among mean value were determined according to Student's test (equal means hypothesis).The significant level of test was set at P<0.05 and P<0.01.
Lipids from milk samples were separated according to international standard ISO 14 256-IDF 172:2 001 using n-pentane and diethyl ether with addition of ammonium hydroxide solution.Extracts were dried under stream of nitrogen and dried lipids frozen at -18 °C until analysis (ISO 14156:IDF 172:2001).
An aliquot of lipids, 50-60 mg, was transferred to 15 ml glass test tube with 5 ml of 0.5 M methanolic sodium hydroxide.The test tube was heated on a stream bath for 8-10 min.Then 3 ml of 5 % BF 3 methanolic solution was added and left on a stream bath for another 3 min.After the cooling to the mixture was added saturated sodium chloride solution to float up the methyl esters.
To accelerate devotion of two layers and to dissolve solid lipids too, 5 ml of n-hexane was added with vigorously shaking.After 30 min n-hexane upper layer was avoided with pipette and dried under anhydrous sodium sulphate to auto sampler vial and analyzed (METCALFE et al. 1966).
The analysis of fatty acid methyl esters were performed on HP 5 890 Series II gas chromatograph (Agilent Technologies, USA) fitted with column DB 23 60m, ID 0.25mm, film thickness 0.25 µm (J&W Scientific).The chromatographic conditions were described in details in work of BECHTEL and OLIVEIRA (2006).Chromatograms were analyzed by ChemStation software using external standard method.

Results and discussion
Table 1 shows duration of the first and the second lactation and data about daily and total amount of milk during lactation.Duration of lactation could be different and depends of many factors.The most important are goat raising and feeding (EKNAES et al. 2006).Obtained results about duration of the first and the second lactation in this experiment are better than 239.36 days for the first and 237.20 days for the second lactation (MEMISI et al. 2001).According to these authors the total milk production in the first lactation of Balkan domestic goat is 175.28L (0.729 kg/day) and in the second lactation 172.47 L (0.722 kg/day) that is less than results in this experiment.BöMKES et al. (2004) cited less lactation, approximately 234.1 days, but more milk per day (2.87 kg).
However, EKNAES et al. (2006) found out higher milk production in Norwegian dairy goats.In the first lactation it was 1.97-3.52L per day.Also MIN et al. (2005) noted 2.95-4.12kg/day in goat bred in farms.
Average values of total solids of 12.63 % in the first and 12.46 % in the second lactation were similar and did not show significant differences (P>0.05), as well as fat (4.39 %, 4.36 %) and lactose content (4.26 %, 4.13 %).Dry matter content was less than 13.31-14.02% that found by FERNáNDEZ et al. (2004), but higher than 9.52-11.27% that established by EKNAES et al. (2006).
Ash content in milk was 0.92 % in the first and 0.94 % in the second lactation, which were less than 0.8 % cited by PARK et al. (2007) and of 0.71-0.83% by FERNáNDEZ et al. (2004).pH value of milk was similar in both of lactation (6.50 and 6.51) and between means did not found significant differences (P>0.05).pH value of milk was less than 6. 69-6.72 (FERNáNDEZ et al. 2004).
Tables 3 present data about fatty acids content in milk of Serbian white goat.Butyric acid content was less in milk in the first lactation (2.03 %) in regard to 2.20 % that found in the second lactation (P<0.05).Obtained results were in accordance to data of PARK et al. (2007) that noted 1.97-2.44%.Other authors (MAREE 2003, EKNAES et al. 2006) found higher values (2.65-4.09% and 2.6 %, respectively).
Duration of the first and the second lactation in Serbian White goat is similar.Daily and total quantities of milk were significantly higher in the second lactation.Basic chemical milk composition is similar in milk in both of lactation.Saturated fatty acid content (C4:0-C10:0) was significantly higher in milk in the second lactation.Saturated (C12:0-C16:0) and unsaturated (C16:1) fatty acid content was similar in milk in both of lactation.Unsaturated fatty acid content (C18:1 and C18:2) was significantly less in milk in the second lactation.Proceeding from conclusions it can be recommended that white Serbian goat in half-intensive breeding system can produce milk of good quality for consumption as well as good raw material for cheese production.
ZAN et al. (2006)tent was 3.10 % in the first and 3.08 % in the second lactation, casein content 2.30 and 2.23 %, and serum protein 0.83 and 0.82 %, respectively.Between means of these parameters did not found statistically difference (P>0.05).Milk protein content was similar in both lactation.Higher level of milk protein was found in investigations ofZAN et al. (2006)that noted 3.40 %, BöMKES et al. (2004) that found 3.38 % and PARK et al. (2007) that established 3.53-3.60%.Less values of 2.56-2.86% found by

Table 3
Fatty acid composition of milk, % Fettsäurespektrum der Milch, % PARK et al. (2007)6) andlues of 0.39-0.92%foundEKNAESetal. (2006) and 2.15 % FERNáNDEZ et al. (2004).Stearic acid content of 8.32 % in the first and 8.35 % in the second lactation were similar and did not show significant differences (P>0.05).Oleic and linoleic acid content in milk was higher in the first lactation (21.87 and 3.07 %) than those found out in the second lactation (19.07 and 2.74 %) that was statistically significant difference (P<0.01).Values of stearic acid content are in accordance toPARK et al. (2007)that found 5.77-13.2% and EKNAES et al. (2006) that found 5.32-16.25 %.Fewer values of 7.85 % found MAREE