EFFECT OF SOYBEANS AND PALM OIL ADDITION TO THE COWS DIETS ON MILK FATTY ACID PROFILE

Effects of soybean and palm oil supplements on milk yields and fatty acids composition with considering intermediate products of unsaturated fatty acids hydrogenation were investigated. Fifteen multiparous Holstein cows in mid-lactation were assigned to groups of 5 each. Cows of control group fed (kg): alfalfa hay — 6; corn silage — 20; grass silage — 10; wheat — 3; corn — 2; soybean meal — 1; molasses — 2. In the diet of the 1st treated group, soybean meal was replaced by 1.5 kg of extruded soybeans. Diet of 2nd treated group cows was supplemented with 0.3 kg of palm oil. All diets were equivalent in contents of nutrients (except fat). Crude fat content in the diets was 0.70, 0.96 and 0.97 kg/cow/day, respectively. Treatment lasted 2 months. Milk yield was recorded weekly for the duration of the study. The milk fatty acids methyl esters were then quantified by gas chromatography. 18:1 (P<0.001) and 1.3 times more of cis-9,trans-11 18:2 (P<0.05) fatty acids compared to cows of control group. Trans-11 18:1 and cis-9,trans-11 18:2 act in animal and human tissues as antagonists of ω-6 fatty acids and, respectively, they are synergists of ω-3 fatty acids. Thus an increased content of these acids improves milk dietary value. Cows of both treated groups had higher milk protein yield for 40 g daily (P<0.05). Milk fat yield was increased only in cows fed palm oil, it was 50 g greater than in control cows (P<0.05). Both fat supplements increased the average daily milk yields. Milk yield of cows fed diet with soybeans addition was higher by 4 % (P<0.05), and in cows fed diet with palm oil milk yield grew to 7 % (P<0.05). Fat corrected milk yield was increased only in cows fed diet with palm oil addition (P<0.05). The results of the present study indicate a benefits of feeding cows by palm oil as dietary supplement.

Effects of soybean and palm oil supplements on milk yields and fatty acids composition with considering intermediate products of unsaturated fatty acids hydrogenation were investigated. Fifteen multiparous Holstein cows in mid-lactation were assigned to groups of 5 each. Cows of control group fed (kg): alfalfa hay -6; corn silage -20; grass silage -10; wheat -3; corn -2; soybean meal -1; molasses -2. In the diet of the 1st treated group, soybean meal was replaced by 1.5 kg of extruded soybeans. Diet of 2nd treated group cows was supplemented with 0.3 kg of palm oil. All diets were equivalent in contents of nutrients (except fat). Crude fat content in the diets was 0.70, 0.96 and 0.97 kg/cow/day, respectively. Treatment lasted 2 months. Milk yield was recorded weekly for the duration of the study. The milk fatty acids methyl esters were then quantified by gas chromatography.
In the milk of cows fed diet with soybeans was found 2.2 times more of trans-11 18:1 (P<0.001) and 1.3 times more of cis-9,trans-11 18:2 (P<0.05) fatty acids compared to cows of control group. Trans-11 18:1 and cis-9,trans-11 18:2 act in animal and human tissues as antagonists of ω-6 fatty acids and, respectively, they are synergists of ω-3 fatty acids. Thus an increased content of these acids improves milk dietary value.
Cows of both treated groups had higher milk protein yield for 40 g daily (P<0.05). Milk fat yield was increased only in cows fed palm oil, it was 50 g greater than in control cows (P<0.05). Both fat supplements increased the average daily milk yields. Milk yield of cows fed diet with soybeans addition was higher by 4 % (P<0.05), and in cows fed diet with palm oil milk yield grew to 7 % (P<0.05). Fat corrected milk yield was increased only in cows fed diet with palm oil addition (P<0. 05 Dietary sources of lipids can be added to the diet of lactating dairy cows to increase the energy density of the diet, modify milk production, and milk fatty acids profile [1][2][3][4][5]. Cows receiving fat supplements produce more milk per unit of consumed dry matter, due to better energy use associated with lower energy losses in the rumen, more efficient production of ATP from long-chain fatty acids than from acetate, direct inclusion of long-chain fatty acids in the fat milk [6]. Fat supplements to the cows diet decrease energy loss on thermoregulation and methanogenesis, reduce the risk of ruminal acidosis. Moreover, fat supplementation has some other effects, such as increased absorption of fat-soluble nutrients and reduced dustiness of feed [5]. Fat digestion and metabolism in ruminants has several features associated with fermentation in the rumen. Double bounds of dietary unsaturated fatty acids are isomerizes and saturated by ruminal bacteria [1][2][3]. In addition, ruminal bacteria synthesize specific fatty acids with odd and branched carbon chains [7]. Triglycerides of the diet are largely hydrolyzed by microbial lipases of rumen to yield free fatty acids, and double bounds of unsaturated fatty acids in turn undergo biohydrogenation to stearic acid and positional and geometrical isomers of oleic, linoleic and linolenic acids that delivered to the small intestine, absorbed to the blood and used by the organism, including for the synthesis of milk fat [1][2][3]. As a result, unsaturated fatty acids, including α-linolenic acid (cis-9,12,15 18:3) and linoleic acid (cis-9,12 18:2), are abundant in grass and certain other ruminant feedstuffs, yet are present at low concentrations in ruminant meat and milk.
The main aim of investigations into ruminal biohydrogenation is to create healthier ruminant products. Increased milk concentration of both conjugated linoleic acid can be obtained by feeding of oilseeds and other fat supplements [14][15][16][17]. The objective of this experiment was to compare the effects of soybeans and palm oil feed supplement on cows' milk production and composition. Conjugated linoleic acid has drawn significant attention in the last two decades for its variety of biologically beneficial effects. At the same time, some researchers are skeptical of positive actions based on traditional ideas about the impact of trans fatty acids, so further research is needed to determine the health effects of trans-11 18:1 and cis-9,trans-11 18:2 acids [18,19].

Materials and methods
Fifteen multiparous Holstein cows in midlactation were assigned to five treatments. The study was preceded by a 3 weeks randomized covariate period. All cows were fed the same diet during the covariate period and had free access to water. Diets were fed twice daily in equal. Cow's diets consisted of (kg): alfalfa hay -6; corn silage -20; grass silage -10; wheat -3; corn -2; soybean meal -1; molasses -2. After that cows were assigned to groups of 5 each. Cows of control group further fed the same diet. In the diet of 1st experimental group soybean meal was replaced by 1.5 kg of extruded at 130 °C exit temperature soybeans. Diet of 2nd experimental group cows was supplemented with 0.3 kg of palm oil. All diets were equivalent in contents of nutrients (except fat): crude protein -3.2, crude fiber -4.5, starch -2.9, sugar -1.7. Crude fat content in these diets was 0.70, 0.96, 0.97 kg/cow/day, respectively. Experimental period lasted 2 months.
Milk yield was recorded weekly for the duration of the study. Samples collected for the determination of protein, fat, and lactose were taken from two consecutive milkings of each week. Milk samples for the determination of fatty acid profiles were collected during the last week of test periods. Milk fat, protein, and lactose were determined by milk analyzer Ecomilk (Bulgaria . Fatty acids were expressed as percentage of total fatty acids. The fatty acids methyl esters were then quantified by gas chromatograph Hewlett Packard HP-6890 with capillary column НР-88 (Agilent Technologies) 100 m lengths, 0.25 mm diameter, stationary phase film thickness 0.2 mcm. The temperature settings were 280 °C for the injector and 290 °C for the detector, and the column oven was temperature programmed from 40 to 260 °C. Flow rate for the carrier gas (He) was 1.2 ml/min. Peaks were quantified by peak area comparisons with a known amount of an internal standard (heptadecanoic acid, Sigma). Peaks were identified by comparison with known commercially prepared standards (37 component FAME mix, Supelco, № 47885-U; CLA isomers mix, Sigma-Aldrich, № 05632).
The SEM were calculated in Excel by dividing the SD by the square root of sample size. Statistics between control and each of experimental groups were calculated by ttest function in the Excel. Differences were considered significant at P<0.05.

Results and discussion
Changes in fatty acid composition of cows diet affected the fatty acid profile of milk fat (tabl. 1). Increasing of dietary fat content decreased the synthesis of some short- chain fatty acids (particularly: butyric (4:0), caproic (6:0) and caprylic (8:0) (P<0.05-0.01)) by mammary gland of cows both treated groups. Additionally, milk of cows fed soybeans contained less myristic (14:0) acid (P<0.01), which is caused by more intensive usage of dietary fatty acids for milk synthesis in cows received fat supplements. Increased level of typical for palm oil myristic (14:0) acid (P<0.05) was found in a large amount in the milk of 2nd experimental group cows. Content of other dominant acidpalmitic (16:0) was about the same in the milk of all groups what can be explained by an efficient synthesis of palmitic acid by mammary gland of cows and therefore less influence of diet on this fatty acid presence in the milk.
Supplementation of cows diet by fat with different fatty acids profile differently influenced the unsaturated fatty acids hydrogenation in the rumen and therefore on the ratio of unsaturated fatty acids isomers in milk.
These acids performing the function of ω-6 fatty acids antagonists and are synergists of ω-3 fatty acids in animals and human tissues, so increased level of trans-11 18:1 and cis-9,trans-11 18:2 improves biological value of milk fat.
The level of these 18:1 and 18:2 isomers in the milk of cows of the 2nd experimental group increased also but a much lesser degree. The contents of trans-11 18:1 and cis-9,trans-11 18:2were 1.3 and 1.2 times higher than in control group but changes were statistically significant only for trans-11 18:1 (P<0.05). Another important change in the fatty acid composition of unsaturated fatty acids is a significantly increased content of linoleic (cis-9,12 18:2) acids in the milk of 1st experimental group cows (P<0.001) and decrease its level in the milk of 2nd experimental group cows (P<0.01). Apparently, it's due to different contents of this acid in soybean and palm oils.
The other significant change in milk fat composition was reduced total amounts of branch-and odd-chain fatty acids in cows fed soybeans (P<0.001). These acids are typical for bacteria of rumen, thus reduced its quantity indicates the suppression of ruminal microflora by polyunsaturated fatty acids of soybeans. Another reason for these effects is a reduced synthesis of fatty acids by bacteria when a large amount of dietary fat is receiving; in this case the bacteria partially used exogenous fatty acids. By this we may also explain the slightly decreased odd-chain fatty acids in milk of cows fed palm oil (P<0.05).
Milk fat of cows fed soybeans contains more polyunsaturated (P<0.01) and less saturated (P<0.01) fatty acids than milk fat of control cows. However, content of polyunsaturated acids in the milk fat of cows fed palm oil was lower than in controls group (P<0.01). This is due to differences in the fatty acid composition of the investigated fat supplements.
Both fat supplements increased the average daily milk yields (Table 2), in the 1st experimental group by 4 % (P<0.05) and in the 2nd experimental group by 7 % (P<0.05), but fat corrected milk yields were higher only in cows fed palm oil (P<0.05).

Conclusions
Replacement of dietary soybean meal by full-fat soybeans or palm oil addition to the diet modifies cow's milk fatty acid composition. Polyunsaturated lipids of soybeans enhanced the content of healthy beneficial trans-11 isomers of octadecenic and octadecadienoic fatty acids in the milk fat. However, soybeans have reduced the milk fat synthesis. Palm oil is low in polyunsaturated fatty acids, so it is less affected the formation of trans-isomers of fatty acids and didn't inhibit the synthesis of milk fat. Both fat supplements increased milk yield of cows, but fat corrected milk yield has increased only by palm oil addition. Obtained results points out the effectiveness of the use of palm oil as a fat supplement for the diet of lactating cows.