HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Interpretive Summary Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Perfield, J. W. Articles by Bauman, D. E. Search for Related Content PubMed PubMed Citation Articles by Perfield, J. W., II Articles by Bauman, D. E.

Use of Conjugated Linoleic Acid (CLA) Enrichments to Examine the Effects of trans-8, cis-10 CLA, and cis-11, trans-13 CLA on Milk-Fat Synthesis^*

¹ Department of Animal Science, Cornell University, Ithaca, NY 14853
² Natural ASA, N-6160, Hovdebygda, Norway

Corresponding author: D. E. Bauman; e-mail: deb6{at}cornell.edu.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION ACKNOWLEDGEMENTS REFERENCES

 
Conjugated linoleic acid (CLA) supplements have typically been comprised of 4 isomers (trans-8, cis-10; cis-9, trans-11; trans-10, cis-12; and cis-11, trans-13 CLA). Abomasal infusion of pure isomers has shown that trans-10, cis-12 CLA is a potent inhibitor of milk-fat synthesis, whereas cis-9, trans-11 CLA has no effect. However, there appear to be additional fatty acids that inhibit milk-fat synthesis, and the objective of this study was to investigate the effects of additional CLA isomers present in CLA supplements. Four rumen fistulated Holstein cows (141 ± 8 DIM, mean ± SE) were randomly assigned in a 4 x 4 Latin square experiment. Treatments were abomasal infusion of (1) skim milk (negative control), (2) trans-10, cis-12 CLA supplement (positive control), (3) trans-8, cis-10 CLA supplement, and (4) cis-11, trans-13 CLA supplement. Treatments 2 through 4 were targeted to provide 4 g/d of the CLA isomer of interest. The trans-8, cis-10 CLA supplement had no effect on milk-fat yield, whereas the trans-10, cis-12 CLA supplement reduced milk-fat yield by 35%. The cis-11, trans-13 CLA supplement contained some trans-10, cis-12 CLA, and when data were compared to the positive control treatment group, it was obvious that cis-11, trans-13 CLA also had no effect on milk-fat synthesis. Milk-fat content of specific CLA isomers was significantly elevated within respective treatment groups. Milk yield, DMI, and milk protein yield were unaffected by treatment. Overall, trans-10, cis-12 CLA reduced milk-fat synthesis, whereas the other major isomers present in CLA supplements (trans-8, cis-10 CLA and cis-11, trans-13 CLA) had no effect.

Key Words: conjugated linoleic acids • CLA • milk fat • lactation • cows

Abbreviation key: CLA = conjugated linoleic acid, MFD = milk-fat depression

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION ACKNOWLEDGEMENTS REFERENCES

 
Conjugated linoleic acid (CLA) is a collective term for different positional and geometric isomers of octadecadienoic acid that contain a pair of double bonds in a conjugated configuration. Mixed isomers of CLA have been shown to reduce milk-fat content when abomasally infused into lactating cows (Loor and Herbein, 1998; Chouinard et al., 1999a, 1999b; Mackle et al., 2003). Commercial preparations of calcium salts of mixed CLA isomers provide a method for protecting the CLA from biohydrogenation in the rumen. Dietary supplements of these rumen-protected calcium salts of CLA cause a reduction in milk-fat synthesis of cows that are at different stages of lactation and fed a variety of diets (Medeiros et al., 2000; Giesy et al., 2002; Perfield et al., 2002; Bernal-Santos et al., 2003).

Commercial preparations of mixed CLA isomers are predominantly composed of 4 CLA isomers (trans-8, cis-10 CLA; cis-9, trans-11 CLA; trans-10, cis-12 CLA; and cis-11, trans-13 CLA). Abomasal infusion of relatively pure CLA isomers identified trans-10, cis-12 CLA as a potent inhibitor of milk-fat synthesis (Baumgard et al., 2000, 2002; Loor and Herbein, 2003) and the curvilinear relationship between percent reduction in milk fat and milk fat content of trans-10, cis-12 CLA has been established (Baumgard et al., 2001; Peterson et al., 2002). However, scenarios exist where the milk-fat content of trans-10, cis-12 CLA does not appear to account completely for the percent reduction in milk-fat synthesis. Peterson et al. (2003) induced milk fat depression (MFD) with a high concentrate, low roughage diet and noted that in their investigation, as well as in other studies where MFD was induced with polyunsaturated oil supplements (Piperova et al., 2000; Whitlock et al., 2002), the MFD was much greater than would be anticipated by the milk-fat content of trans-10, cis-12 CLA. A similar discrepancy between milk-fat content of trans-10, cis-12 CLA and reduction in milk fat was observed by Perfield et al. (2002) and Bernal-Santos et al. (2003) in cows fed rumen-protected CLA. Likewise, Chouinard et al. (1999b) demonstrated that abomasal infusion of a CLA supplement containing a mixture of CLA isomers devoid of the trans-10, cis-12 CLA isomer caused MFD.

The substantial divergences from the relationship between milk-fat content of trans-10, cis-12 CLA and reduction in milk-fat yield suggest that other CLA isomers or unique fatty acids formed in the rumen might also affect lipid metabolism in the mammary gland. The objective of the present study was to examine milk-fat synthesis and compare the effects of CLA supplements enriched with other predominant CLA isomers found in CLA mixtures (trans-8, cis-10 CLA and cis-11, trans-13 CLA) to the effects of trans-10, cis-12 CLA, a known inhibitor of milk-fat synthesis. Similar to trans-10, cis-12 CLA, trans-8, cis-10 CLA, and cis-11, trans-13 CLA are CLA isomers that are naturally present in the rumen and milk fat but at very low concentrations (Sehat et al., 1998; Bauman et al., 2000; Piperova et al., 2000, 2002).

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION ACKNOWLEDGEMENTS REFERENCES

 
The Cornell University Institutional Animal Care and Use Committee approved all procedures involving animals. Four rumen fistulated lactating Holstein cows 141 ± 8 DIM (mean ± SE) were randomly assigned in a 4 x 4 Latin square experiment and housed in tie stalls at the Cornell University Large Animal Teaching and Research Unit. Cows were fed a TMR formulated to meet or exceed nutrient requirements for energy, protein, minerals, and vitamins (NRC, 2001) using the Cornell Net Carbohydrate and Protein System (Fox et al., 1992). Chopped alfalfa was the major forage component, with cornmeal as the major concentrate (Table 1). Cows were fed ad libitum with equal portions of feed offered at 0700 and 1900 h daily. Water was available at all times.

Treatments were abomasal infusion of (1) skim milk (control), (2) trans-8, cis-10 CLA supplement (8,10 CLA), (3) cis-11, trans-13 CLA supplement (11,13 CLA), and (4) trans-10, cis-12 CLA supplement (10,12 CLA). The conditions by which the 8,10 CLA and 11,13 CLA supplements were manufactured resulted in a significant proportion of one other CLA isomer in each supplement. The fatty acid composition of the supplements (Natural ASA, Hovdebygda, Norway) is provided in Table 2. The presence of trans-10, cis-12 CLA in the 11,13 CLA supplement was accounted for by the positive control treatment group, which provided a comparable quantity of trans-10, cis-12 CLA. The CLA supplements were emulsified with skim milk using a microfluidizer (model 110T; Microfluidics, Newton, MA) at a pressure of 8000 lb/in² (563.6 kg/cm²) as previously described (Chouinard et al., 1999a). Emulsions were prepared fresh each experimental period, and target concentrations were formulated to provide 4.0 g/d of the isomer of interest. Actual CLA concentrations in the emulsions were determined by the difference in total solids content (AOAC, 2000: method 990.20) between the skim milk (control) and each of the emulsions, and average amounts of CLA isomers infused over the 4 treatment periods are presented in Table 3. Skim milk (control) and CLA emulsions were stored at 4°C until infused.

Fatty Acid Analysis
Milk fat was extracted using the method of Hara and Radin (1978), and fatty acid methyl esters were prepared by base-catalyzed transmethylation according to Christie (1982) with modifications by Chouinard et al. (1999a). Fatty acid methyl esters were quantified using a gas chromatograph (GCD system HP 6890+; Hewlett Packard, Avondale, PA) equipped with a CP-SIL 88 fused silica capillary column (100 m x 0.25 mm (i.d.) with 0.2-µm film thickness; Varian, Inc. Walnut Creek, CA). Gas chromatograph conditions were as described by Perfield et al. (2002). Fatty acid peaks were identified using pure methyl ester standards (Nu-Chek Prep, Elysian, MN). Additional standards for CLA isomers were obtained from Natural ASA. A butter oil reference standard (CRM 164; Commission of the European Community Bureau of References, Brussels, Belgium) was used to determine recoveries and correction factors for individual fatty acids.

Statistical Analysis
Data were statistically analyzed as a 4 x 4 Latin square design using the PROC MIXED procedure of SAS (1998), where the model is:

where

Yijk	=	observation,
µ	=	overall mean,
Ti	=	treatment (i = 1, 2, 3, and 4),
Pj	=	period (j = 1, 2, 3, and 4),
Ck	=	cow (k = 1, 2, 3, and 4), and
Eijk	=	residual error.

	RESULTS AND DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION ACKNOWLEDGEMENTS REFERENCES

 
Abomasal infusion was used as a convenient experimental method to provide the CLA isomer supplements in a manner that would avoid biohydrogenation and metabolism of the fatty acids by rumen bacteria. In comparison with the control treatment, the 8,10 CLA supplement had no effect on milk-fat synthesis. Reductions in milk-fat percentage and milk-fat yield were observed for both the 10,12 CLA and 11,13 CLA treatment groups (Table 4). However, a similar quantity of trans-10, cis-12 CLA, a potent inhibitor of milk-fat synthesis, was provided by both supplements. The temporal pattern depicts a progressive reduction in milk-fat yield for the 10,12 CLA and 11,13 CLA treatments with a return to previous yields after the termination of infusions (Figure 1). In contrast to milk fat, yields of milk and milk protein were not affected by any of the treatments, and DMI did not differ significantly among treatment groups (Table 4). The lack of change in DMI, milk yield, and milk-protein yield is consistent with other studies that have abomasally infused CLA isomers and observed a reduction in milk fat (Chouinard et al., 1999a, 1999b; Baumgard et al., 2000, 2001; Peterson et al., 2002; Loor and Herbein, 2003).

View larger version (16K): [in this window] [in a new window]   Figure 1. Temporal pattern of milk fat yield during abomasal infusion of conjugated linoleic acid (CLA) supplements. Infusion period (5 d) indicated by the dotted lines. Values represent means from 4 cows; SEM = 0.07 kg/d.

The lack of an effect of the 8,10 CLA supplement on milk-fat yield and milk fatty-acid composition is a clear indication that trans-8, cis-10 CLA at a dose of 3.5 g/d does not cause MFD. The 8,10 CLA supplement did provide 5.7 g/d of cis-9, trans-11 CLA, but there have been a number of previous studies that focused on this specific isomer, in part because it is the major CLA isomer in milk fat. Whereas Loor and Herbein (1998) concluded that cis-9, trans-11 CLA and its metabolite trans-11 18:1 did cause MFD in an early study involving infusion of mixed isomers of CLA, this has not been supported by the present study (Figure 1) or more recent work. Abomasal infusion studies using relatively pure cis-9, trans-11 CLA have shown that this isomer has no effect on milk-fat synthesis even at high concentrations (15 g/d) (Baumgard et al., 2000, 2002; Loor and Herbein, 2003). Griinari et al. (2000) abomasally infused 25 g/d of a mixture containing equal quantities of trans-11 18:1 and trans-12 18:1 and observed no effect on milk-fat synthesis. Furthermore, it has been shown that milk-fat content of either cis-9, trans-11 CLA or trans-11 18:1 has little or no relationship to milk-fat percent or milk-fat yield (Kelsey et al., 2003; Lock et al., 2003). Therefore, we conclude that, although trans-8, cis-10 CLA is taken up by the mammary gland and transferred to milk fat, it has no effect on milk-fat synthesis.

The 11,13 CLA supplement contained both cis-11, trans-13 and trans-10, cis-12 CLA, and it caused a reduction in milk-fat synthesis. To address this, a positive control treatment consisting of pure trans-10, cis-12 CLA was used. The trans-10, cis-12 CLA isomer has been shown to be a potent inhibitor of milk-fat synthesis (Baumgard et al., 2000, 2001; Loor and Herbein, 2003). Peterson et al. (2002) established that a curvilinear relationship exists between dose of trans-10, cis-12 CLA abomasally infused and the extent of reduction in milk-fat synthesis. In the present study, similar amounts of trans-10, cis-12 CLA were provided by both the 11,13 CLA and 10,12 CLA treatments, and they resulted in an equivalent decline in milk-fat synthesis. The reductions in milk-fat yield observed for these 2 treatment groups were also consistent with the dose response curve developed by Peterson et al. (2002). Likewise, milk composition changes observed for the 11,13 CLA and 10,12 CLA supplements were similar to Peterson et al. (2002), and the percentage of trans-10, cis-12 CLA present in the milk fat of the 11,13 CLA and 10,12 CLA treatment groups was not different (Table 5). Therefore, we conclude that cis-11, trans-13 CLA has no effect on rates of milk-fat synthesis, and the decrease in milk-fat yield and changes in milk fatty-acid composition observed with the 11,13 CLA supplement were entirely due to the presence of trans-10, cis-12 CLA.

The impetus for this study was based in part on results from an earlier experiment where abomasal infusion of a supplement enriched with cis/trans 8,10 CLA and devoid of cis/trans 10, 12 CLA caused a reduction in milk-fat synthesis (Chouinard et al., 1999b). At the time, we were unable to identify which double bond was cis and which was trans, but in subsequent analysis, we established that this isomer was trans-8, cis-10 CLA. Results from the present experiment rule out trans-8, cis-10 CLA along with cis-11, trans-13 CLA as causes for that reduction in milk-fat synthesis. Castor oil was the starting material for the manufacture of the trans-8, cis-10 CLA enriched supplement used by Chouinard et al. (1999b), whereas the starting material used to make the trans-8, cis-10 CLA preparation in the present study was vegetable oil. Both preparations contained a high concentration of trans-8, cis-10 CLA. However, the difference in starting materials may have resulted in a slightly different overall fatty acid profile. Obviously, the preparation derived from castor oil contained a small quantity of a potent inhibitor of milk-fat synthesis other than the trans-10, cis-12 CLA isomer, and this is why a reduction in milk-fat synthesis was observed. In particular, castor oil has a high content of ricinoleic acid (12-hydroxy-9-octadecenoic acid), and perhaps this or some metabolite of it brought about the reduction in milk-fat synthesis.

There was no effect on milk-fat synthesis by either trans-8, cis-10 CLA or cis-11, trans-13 CLA, so there must be other explanations for the discrepancy between the milk-fat content of trans-10, cis-12 CLA and reduction in milk-fat synthesis observed when calcium salts of CLA were fed (Perfield et al., 2002; Bernal-Santos et al., 2003). One possibility consistent with the biohydrogenation theory of MFD (Bauman and Grinarii, 2001) is that a unique fatty acid intermediate(s) is formed in the rumen from one of the fatty acids present in the supplement, and this compound(s) is a potent inhibitor of milk-fat synthesis. Calcium salts of polyunsaturated fatty acids are only partially protected against rumen biohydrogenation and metabolism, and this varies according to the specific polyunsaturated fatty acid being protected and the rumen environment (Gulati et al., 1997; Wu and Papas, 1997). Studies that have fed a mixture of CLA isomers in the form of rumen-protected calcium salts showed the specific transfer efficiency for trans-10, cis-12 CLA into milk fat was 2 to 4% (Perfield et al., 2002; Bernal-Santos et al., 2003), whereas the transfer from abomasal infusion was about 20% (Baumgard et al., 2000, 2001; Peterson et al., 2002). The rumen-protected supplement of CLA caused a greater reduction in milk-fat content than would be anticipated based on the milk-fat content of trans-10, cis-12 CLA. This suggests that some of the fatty acids in the supplement were metabolized in the rumen to unique fatty acids that may also be potent inhibitors of milk-fat synthesis. Alternatively, unidentified biohydrogenation intermediates that affect milk-fat synthesis have also been suggested to be involved in situations of diet-induced MFD based on the fact that trans-10, cis-12 CLA content of milk fat is inadequate to explain completely the degree of reduction in milk-fat synthesis (Bauman and Griinari, 2003; Peterson et al., 2003).

Overall, abomasal infusion of trans-10, cis-12 CLA caused a reduction in the rates of milk-fat synthesis consistent with results from previous studies. Comparisons of results from the two CLA enrichments (8,10 CLA and 11,13 CLA) to those of a negative control (no CLA) and a positive control (trans-10, cis-12 CLA) demonstrated abomasal infusion of trans-8, cis-10 CLA, cis-11, trans-13 CLA, and cis-9, trans-11 CLA had no effect on milk-fat synthesis.

	ACKNOWLEDGEMENTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION ACKNOWLEDGEMENTS REFERENCES

 
The assistance of the following students and colleagues at Cornell University in implementing the study is gratefully acknowledged and appreciated: S. Tucker, B. Corl, B. English, L. Furman, D. Dwyer, D. Barbano, J. Lynch, R. Kaltaler, D. Ceurter, M. Partridge, and T. Muscato.

	FOOTNOTES

 
^* Supported in part by USDA-CSREES-NRICGP (Grant 2003-35206-12819), Natural ASA, and Cornell Agricultural Experiment Station.

Received for publication September 5, 2003. Accepted for publication November 17, 2003.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION ACKNOWLEDGEMENTS REFERENCES

 


Association of Official Analytical Chemists, International. 2000. Official Methods of Analysis. 17th ed. AOAC, Arlington, VA.

Bauman, D. E., and J. M. Griinari. 2001. Regulation and nutritional manipulation of milk fat: Low-fat milk syndrome. Livestock Prod. Sci. 70:15–29.

Bauman, D. E., and J. M. Griinari. 2003. Nutritional regulation of milk fat synthesis. Annu. Rev. Nutr. 23:203–227.[Medline]

Bauman, D. E., D. M. Barbano, D. A. Dwyer, and J. M. Griinari. 2000. Technical note: Production of butter with enhanced conjugated linoleic acid for use in biomedical studies with animal models. J. Dairy Sci. 83:2422–2425.[Abstract]

Baumgard, L. H., B. A. Corl, D. A. Dwyer, A. Saebo, and D. E. Bauman. 2000. Identification of the conjugated linoleic acid isomer that inhibits milk fat synthesis. Am. J. Physiol. 278:R179–R184.

Baumgard, L. H., J. K. Sangster, and D. E. Bauman. 2001. Milk fat synthesis in dairy cows is progressively reduced by increasing supplemental amounts of trans-10, cis-12 conjugated linoleic acid (CLA). J. Nutr. 131:1764–1769.[Abstract/Free Full Text]

Baumgard, L. H., B. A. Corl, D. A. Dwyer, and D. E. Bauman. 2002. Effects of conjugated linoleic acids (CLA) on tissue response to homeostatic signals and plasma variables associated with lipid metabolism in lactating dairy cows. J. Anim. Sci. 80:1285–1293.[Abstract/Free Full Text]

Bernal-Santos, G., J. W. Perfield, II, T. R. Overton, and D. E. Bauman. 2003. Production responses of dairy cows to dietary supplementation with conjugated linoleic acid (CLA) during the transition period and early lactation. J. Dairy Sci. 86:3218–3228.[Abstract/Free Full Text]

Chouinard, P. Y., L. Corneau, D. M. Barbano, L. E. Metzger, and D. E. Bauman. 1999a. Conjugated linoleic acids alter milk fatty acid composition and inhibit milk fat secretion dairy cows. J. Nutr. 129:1579–1584.[Abstract/Free Full Text]

Chouinard, P. Y., L. Corneau, A. Saebo, and D. E. Bauman. 1999b. Milk yield and composition during abomasal infusion of conjugated linoleic acids in dairy cows. J. Dairy Sci. 82:2737–2745.[Abstract]

Christie, W. W. 1982. A simple procedure for rapid transmethylation of glycerolipids and cholesteryl esters. J. Lipid Res. 23:1072–1075.[Abstract]

Fox, D. G., C. J. Sniffen, J. D. O’Connor, J. B. Russell, and P. J. Van Soest. 1992. A net carbohydrate and protein system for evaluating cattle diets: III. Cattle requirements and diet adequacy. J. Anim. Sci. 70:3578–3596.[Abstract]

Giesy, J. G., M. A. McGuire, B. Shafii, and T. W. Hanson. 2002. Effect of dose of calcium salts of conjugated linoleic acid (CLA) on percentage and fatty acid content of milk fat in midlactation Holstein cows. J. Dairy Sci. 85:2023–2029.[Abstract/Free Full Text]

Griinari, J. M., B. A. Corl, S. H. Lacy, P. Y. Chouinard, K. V. Nurmela, and D. E. Bauman. 2000. Conjugated linoleic acid is synthesized endogenously in lactating dairy cows by ⁹-desaturase. J. Nutr. 130:2285–2291.[Abstract/Free Full Text]

Gulati, S. K., T. W. Scott, and J. R. Ashes. 1997. In-vitro assessment of fat supplements for ruminants. Anim. Feed Sci. Technol. 64:127–132.

Hara, A., and N. S. Radin. 1978. Lipid extraction of tissues with a low-toxicity solvent. Anal. Biochem. 90:420–426.[Medline]

Kelsey, J. A., B. A. Corl, R. J. Collier, and D. E. Bauman. 2003. The effect of breed, parity, and stage of lactation on conjugated linoleic acid (CLA) in milk fat from dairy cows. J. Dairy Sci. 86:2588–2597.[Abstract/Free Full Text]

Lock, A. L., D. E. Bauman, and P. C. Garnsworthy. 2003. Effects of milk yield and milk fat production on milk cis-9, trans-11 CLA and ⁹-desaturase enzyme activity. J. Dairy Sci. 86(Suppl. 1):245. (Abstr.)

Loor, J. J., and J. H. Herbein. 1998. Exogenous conjugated linoleic acid isomers reduce bovine milk fat concentration and yield by inhibiting de novo fatty acid synthesis. J. Nutr. 128:2411–2419.[Abstract/Free Full Text]

Loor, J. J., and J. H. Herbein. 2003. Reduced fatty acid synthesis and desaturation due to exogenous trans10, cis12-CLA in cows fed oleic or linoleic oil. J. Dairy Sci. 86:1354–1369.[Abstract/Free Full Text]

Mackle, T. R., J. K. Kay, M. J. Auldist, A. K. H. McGibbon, B. A. Philpott, L. H. Baumgard, and D. E. Bauman. 2003. Effects of abomasal infusion of conjugated linoleic acid on milk fat concentration and yield from pasture-fed dairy cows. J. Dairy Sci. 86:644–652.[Abstract/Free Full Text]

Medeiros, S. R., D. E. Oliveira, J. M. Aroeira, M. A. McGuire, D. E. Bauman, and D. P. D. Lanna. 2000. The effect of long term supplementation of conjugated linoleic acid (CLA) to dairy cows grazing tropical pasture. J. Dairy Sci. 83(Suppl. 1):169. (Abstr.)

National Research Council. 2001. Nutrient Requirements of Dairy Cattle, 7th rev. ed. Natl. Acad. Press, Washington, DC.

Perfield, J. W., II, G. Bernal-Santos, T. R. Overton, and D. E. Bauman. 2002. Effects of dietary supplementation of rumen-protected conjugated linoleic acid in dairy cows during established lactation. J. Dairy Sci. 85:2609–2617.[Abstract/Free Full Text]

Peterson, D. G., L. H. Baumgard, and D. E. Bauman. 2002. Short communication: Milk fat response to low doses of trans-10, cis-12 conjugated linoleic acid (CLA). J. Dairy Sci. 85:1764–1766.[Abstract/Free Full Text]

Peterson, D. G., E. A. Matitashvili, and D. E. Bauman. 2003. Diet-induced milk fat depression in dairy cows results in increased trans-10, cis-12 CLA in milk fat and coordinate suppression of mRNA abundance for mammary enzymes involved in milk fat synthesis. J. Nutr. 133:3098–3102.[Abstract/Free Full Text]

Piperova, L. S., B. B. Teter, I. Bruckental, J. Sampugna, S. E. Mills, M. P. Yurawecz, J. Fritsche, K. Ku, and R. A. Erdman. 2000. Mammary lipogenic enzyme activity, trans fatty acids and conjugated linoleic acid are altered in lactating dairy cows fed a milk fat-depressing diet. J. Nutr. 130:2568–2574.[Abstract/Free Full Text]

Piperova, L. S., J. Sampugna, B. B. Teter, I. Bruckental, K. F. Kalscheur, M. P. Yurawecz, Y. Ku, K. M. Morehouse, and R. A. Erdman. 2002. Duodenal and milk trans octadecenoic acid and conjugated linoleic acid (CLA) isomers indicate that postabsorptive synthesis is the predominant source of cis-9-containing CLA in lactating dairy cows. J. Nutr. 132:1235–1241.[Abstract/Free Full Text]

SAS User’s Guide: Statistics, Version 6.12 ed. 1998. SAS Inst., Inc., Cary, NC.

Sehat, N., J. K. G. Kramer, M. M. Mossoba, M. P. Yurawecz, J. A. G. Roach, K. Eulitz, K. M. Morehouse, and Y. Ku. 1998. Identification of conjugated linoleic acid isomers in cheese by gas chromatography, silver ion high performance liquid chromatography, and mass spectral reconstructed ion profiles. Comparison of chromatographic elution sequences. Lipids 33:963–971.[Medline]

Spires, H. R., J. H. Clark, R. G. Derrig, and C. L. Davis. 1975. Milk production and nitrogen utilization in response to postruminal infusion of sodium caseinate in lactating cows. J. Nutr. 105:1111–1121.[Abstract/Free Full Text]

Whitlock, L. A., D. J. Schingoethe, A. R. Hippen, K. F. Kalscheur, R. J. Baer, N. Ramaswamy, and K. M. Kasperson. 2002. Fish oil and extruded soybeans fed in combination increase conjugated linoleic acids in milk of dairy cows more than when fed separately. J. Dairy Sci. 85:234–243.[Abstract]

Wu, S. H. W., and A. Papas. 1997. Rumen-stable delivery systems. Adv. Drug Delivery Rev. 28:323–334.[Medline]

This article has been cited by other articles:

				F. Glasser, A. Ferlay, M. Doreau, P. Schmidely, D. Sauvant, and Y. Chilliard Long-Chain Fatty Acid Metabolism in Dairy Cows: A Meta-Analysis of Milk Fatty Acid Yield in Relation to Duodenal Flows and De Novo Synthesis J Dairy Sci, July 1, 2008; 91(7): 2771 - 2785. [Abstract] [Full Text] [PDF]

				D. E. Bauman, J. W. Perfield II, K. J. Harvatine, and L. H. Baumgard Regulation of Fat Synthesis by Conjugated Linoleic Acid: Lactation and the Ruminant Model J. Nutr., February 1, 2008; 138(2): 403 - 409. [Abstract] [Full Text] [PDF]

				J. W. Perfield II, A. L. Lock, J. M. Griinari, A. Saebo, P. Delmonte, D. A. Dwyer, and D. E. Bauman Trans-9, Cis-11 Conjugated Linoleic Acid Reduces Milk Fat Synthesis in Lactating Dairy Cows J Dairy Sci, May 1, 2007; 90(5): 2211 - 2218. [Abstract] [Full Text] [PDF]

				K. J. Shingfield, S. Ahvenjarvi, V. Toivonen, A. Vanhatalo, and P. Huhtanen Transfer of Absorbed cis-9, trans-11 Conjugated Linoleic Acid into Milk Is Biologically More Efficient than Endogenous Synthesis from Absorbed Vaccenic Acid in Lactating Cows J. Nutr., May 1, 2007; 137(5): 1154 - 1160. [Abstract] [Full Text] [PDF]

				J. K. Kay, T. R. Mackle, D. E. Bauman, N. A. Thomson, and L. H. Baumgard Effects of a Supplement Containing Trans-10, Cis-12 Conjugated Linoleic Acid on Bioenergetic and Milk Production Parameters in Grazing Dairy Cows Offered Ad Libitum or Restricted Pasture J Dairy Sci, February 1, 2007; 90(2): 721 - 730. [Abstract] [Full Text] [PDF]

				J. W. Perfield II, P. Delmonte, A. L. Lock, M. P. Yurawecz, and D. E. Bauman Trans-10, trans-12 conjugated linoleic acid does not affect milk fat yield but reduces delta9-desaturase index in dairy cows. J Dairy Sci, July 1, 2006; 89(7): 2559 - 2566. [Abstract] [Full Text] [PDF]

				K. J. Shingfield, C. K. Reynolds, G. Hervas, J. M. Griinari, A. S. Grandison, and D. E. Beever Examination of the Persistency of Milk Fatty Acid Composition Responses to Fish Oil and Sunflower Oil in the Diet of Dairy Cows J Dairy Sci, February 1, 2006; 89(2): 714 - 732. [Abstract] [Full Text] [PDF]

				L. S. Piperova, U. Moallem, B. B. Teter, J. Sampugna, M. P. Yurawecz, K. M. Morehouse, D. Luchini, and R. A. Erdman Changes in Milk Fat in Response to Dietary Supplementation with Calcium Salts of Trans-18:1 or Conjugated Linoleic Fatty Acids in Lactating Dairy Cows J Dairy Sci, November 1, 2004; 87(11): 3836 - 3844. [Abstract] [Full Text] [PDF]

				J. W. Perfield II, A. L. Lock, A. M. Pfeiffer, and D. E. Bauman Effects of Amide-Protected and Lipid-Encapsulated Conjugated Linoleic Acid (CLA) Supplements on Milk Fat Synthesis J Dairy Sci, September 1, 2004; 87(9): 3010 - 3016. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Interpretive Summary Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Perfield, J. W. Articles by Bauman, D. E. Search for Related Content PubMed PubMed Citation Articles by Perfield, J. W., II Articles by Bauman, D. E.