Feeding Fish Meal and Extruded Soybeans Enhances the Conjugated Linoleic Acid (CLA) Content of Milk

Fish Meal and Extruded Soybean

The Effect of Feeding Fish Meal and Extruded Soybean on Increasing Conjugated Linoleic Acid (CLA) in Milk

Article: Feeding Fish Meal and Extruded Soybeans Enhances the Conjugated Linoleic Acid (CLA) Content of Milk[۱]

Authors: Abu-Ghazaleh, AA Schingoethe, DJ Hippen, AR Whitlock, LA

Year of publication: 2002

INTRODUCTION:

Conjugated linoleic acid (CLA) refers to a collection of positional and geometric isomers of octadecadienoic acid with conjugated double bonds. Conjugated linoleic acid is synthesized either in the rumen as an intermediate in the biohydrogenation of linoleic acid or in the tissues by ∆9-desaturase from trans-11 C18:1 (TVA), another intermediate in ruminal biohydrogenation (Griinari et al., 1999; Donovan et al., 2000). More than 82% of the CLA in dairy products is cis-9, trans-11 CLA (Chin et al., 1992). In animal models, cis-9, trans-11 CLA has been shown to reduce the incidence and growth of tumors, enhance immune function, and to have the ability to prevent diabetes.

The dietary addition of plant oils and fish oil resulted in substantial increases in milk fat cis-9, trans-11 CLA concentrations (Dhiman et al., 2000; Donovan et al., 2000; Whitlock et al., 2002). However, feeding greater amounts of plant oils and fish oil normally tends to decrease ruminal metabolism. Including fish oil at 2% of the diet increased milk CLA concentrations by 3.2- fold but decreased both milk fat percentages and yield (Donovan et al., 2000). In the study reported by Dhiman et al. (2000), CLA concentration in milk fat increased 190% when cows were fed 2.0% soybean oil, but milk fat percentages and yields dropped. An alternative is to use full fat seeds that are processed so that a portion of their unsaturated fatty acids becomes available in the rumen for microbial biohydrogenation. Previous investigations (Dhiman et al., 2000; Whitlock et al., 2002) with dietary processed soybeans showed increased concentrations of cis-9, trans-11 CLA in milk fat.

Goals:

The aim of this study is to determine the effect of adding fish oil derived from fish meal (FM) along with extruded soybean (ESB) to the diet of lactating cows on the levels of cis-9, trans-11 CLA and TVA in milk.

MATERIALS AND METHODS:

Twelve multiparous lactating cows, with an average days in milk (DIM) of 66 days, were assigned to a 4×4 Latin square design over a period of four weeks, receiving one of the following four treatments: Control, 0.5% fish oil derived from fish meal (FM), 2.5% oil extracted from extruded soybean (ESB), A combination of both oils (0.5% from fish meal and 2.0% from extruded soybean; ESB+FM). The experiment used four protein sources: fish meal, extruded soybean, soybean hulls, and soybean meal. The diets were formulated to provide 18% crude protein. It is noteworthy that the fat content of the tested fish meal and extruded soybean was measured at 8.9% and 19.3%, respectively. Accordingly, the total fatty acid intake per day was: 332 g/day for the control group, 1000 g/day for the FM group, 1500 g/day for the ESB group, and 1512 g/day for the ESB+FM group.

RESULTS AND DISCUSSION:

Milk production and milk composition were affected by the treatments. Cows fed with ESB, FM, and ESB+FM produced 3.6, 1.3, and 4.7 liters more milk, respectively, compared to the control group. The reported increase in milk production cannot be attributed to higher feed intake, as the daily dry matter intake was similar across all treatments (P > 0.05). This finding may be due to the provision of higher quality protein and amino acids in the small intestine for milk synthesis, since supplying adequate amounts of protein and amino acids in the intestine of lactating cows promotes increased milk production.

The experimental treatments caused a decrease in milk fat content, with the highest milk fat observed in the control group and the lowest in the ESB+FM treatment. However, there was no significant difference in the total amount of milk fat produced among the treatment groups. In fact, with increased milk yield and decreased milk fat percentage, the energy-corrected milk was similar across the treatments. The amount of true protein produced in the milk increased, while the percentage of true protein decreased. Previous studies have shown that fat supplementation in lactating dairy cows reduces milk protein percentage. Therefore, the results of this study regarding fat and protein are consistent with past research. The highest somatic cell count (SCC) in this study was observed in the control group, although the SCC values remained within acceptable limits and did not reduce milk production.

The experimental treatments caused a decrease in milk fat content, with the highest milk fat observed in the control group and the lowest in the ESB+FM treatment. However, there was no significant difference in the total amount of milk fat produced among the treatment groups. In fact, with increased milk yield and decreased milk fat percentage, the energy-corrected milk was similar across the treatments. The amount of true protein produced in the milk increased, while the percentage of true protein decreased. Previous studies have shown that fat supplementation in lactating dairy cows reduces milk protein percentage. Therefore, the results of this study regarding fat and protein are consistent with past research. The highest somatic cell count (SCC) in this study was observed in the control group, although the SCC values remained within acceptable limits and did not reduce milk production. 

​

Figure 1. Effect of treatments (Control, FM, ESB, and FM+ESB) on milk fatty acid composition; Short-chain fatty acids (C4:0 – C13:0), Medium-chain fatty acids (C14:0 – C17:1), Long-chain fatty acids (greater than C18:0).

Changes in the ratio of saturated fatty acids were mainly due to lower concentrations of C12:0, C14:0, and C16:0, and higher ratios of TVA, cis-9 C18:1, cis-9, cis-12 C18:2, and CLA in milk fat from cows fed ESB and FM+ESB diets. The addition of fat supplements led to a decrease in the concentration of short- and medium-chain fatty acids, which are synthesized de novo by the mammary gland. The concentration of individual fatty acids in milk fat decreased in the ESB and FM+ESB diets. Rumen bacteria, which synthesize long-chain fatty acids from individual carbon volatile fatty acids (VFAs), are the main source of these individual chain fatty acids in milk fat. The proportions of C18:0, C18:1, and C18:2 in milk fat increased when cows were fed ESB and FM+ESB. The ratios of C18:1 isomers in milk fat were all affected by the experimental treatments. The increase in trans C18:1 fatty acids in milk fat indicates that incomplete biohydrogenation occurs to a greater extent when cows are fed FM, ESB, or their combination.

The proportion of TVA in milk fat increased by 41%, 177%, and 349% in cows fed FM, ESB, and FM+ESB diets, respectively, compared to the control diet. Δ9-desaturase is responsible for producing at least 65% of the cis-9, trans-11 CLA in milk fat. Previous studies have reported a decrease in milk fat concurrent with an increase in TVA due to fish meal feeding. It has been suggested that trans-10 C18:1, which originates in the rumen from the biohydrogenation of trans-10, cis-12 C18:2 (which is itself formed during biohydrogenation of C18:2), is the factor causing milk fat depression. Additionally, ruminal concentrations of dietary-derived trans-10, cis-12 C18:2 have been reported to negatively correlate with milk fat percentage. Overall, the results of this study support the concept that milk fat depression is associated with the production of trans-10, cis-12 C18:2.

The concentration of cis-9, trans-11 CLA increased significantly (P < 0.05) in all experimental treatment groups compared to the control group, with the greatest increase observed when cows were fed ESB+FM. The content of cis-9, trans-11 CLA in milk fat increased by 42%, 139%, and 321% with FM, ESB, and FM+ESB treatments, respectively, compared to the control. The increase in cis-9, trans-11 CLA content in milk fat with the FM+ESB treatment was significantly greater than the effects of FM and ESB alone. The highest production of TVA and cis-9, trans-11 CLA in milk fat was observed when feeding FM+ESB. This is attributed to the stimulation of the rumen environment by components of fish oil, promoting the production of cis-9, trans-11 CLA and TVA from C18:2 and C18:3 (which originate from the remainder of the diet).

The fish oil present in FM is a good source of EPA and DHA. Cows fed FM consumed an average of 15.8 g/day of EPA and 14.2 g/day of DHA, and secreted an average of 0.94 g/day of EPA and 1.78 g/day of DHA in milk. The transfer efficiency of EPA and DHA from feed to milk was 6% and 12.6%, respectively. The low transfer efficiency of EPA and DHA from feed to milk fat may be due to preferential deposition of these fatty acids in body tissues rather than milk fat, or possibly due to extensive biohydrogenation of EPA and DHA in the rumen.

CONCLUSIONS AND IMPLICATIONS:

Feeding lactating dairy cows with a mixture of fish oil from FM and soybean oil from ESB resulted in a greater increase in the concentration and yield of cis-9, trans-11 CLA and TVA in milk compared to feeding each source separately. This indicates that fish oil enhances the production of cis-9, trans-11 CLA and TVA by stimulating the conversion of linoleic and linolenic acids supplied from other dietary sources. Feeding FM and ESB increased milk production, milk protein yield, and the unsaturated fatty acid content of milk. Milk fat percentage decreased when cows were fed the FM and ESB mixture; however, milk fat yield was not affected. Feeding lactating cows fish oil from FM together with ESB improved the nutritional value of milk and increased production.

REFERENCES:

DOI: https://doi.org/۱۰.۳۱۶۸/jds.S۰۰۲۲-۰۳۰۲(۰۲)۷۴۱۱۶-۷

Abu-Ghazaleh, A., et al., Feeding fish meal and extruded soybeans enhances the conjugated linoleic acid (CLA) content of milk. Journal of Dairy Science, ۲۰۰۲

. ۸۵(۳): p. ۶۲۴-۶۳۱.