Trans18:1 and 18:2 isomers in blood plasma and milk fat of grazing cows fed a grain supplement containing solvent-extracted or mechanically extracted soybean meal.
Thirty Holstein cows grazing mixed clover-grass pastures for 12 wk from May through July were fed a grain supplement containing solvent-extracted soybean meal (SES), or mechanically extracted soybean meal (MES) to determine whether differences in supplemental 18:2n6 fatty acid intake altered secretion of unsaturated fatty acids. Groups of 10 cows each were fed in two equal feedings a supplement (7.3 kg/d) containing ground corn plus either 1.8 kg of SES, 2.2 kg of MES, or 2.2 kg of MES plus 30 g of methionine hydroxy analog (Alimet; MESM). Fatty acid content (% of DM) of grass and clover in pastures averaged 1.9 and 1.5%, respectively. Concentration of 18:3n3 was higher in grass compared with clover (532 vs. 454 mg/g of total fatty acids). Yield of milk (32 kg/d average) and milk components did not differ by supplements. Total blood plasma fatty acids (mg/ml) during wk 4 were higher due to MESM (1.0) compared with MES (0.6) or SES (0.6). Cows fed MESM or MES had greater concentrations of 18:2n6, trans11-18:1, and cis9,trans11-18:2 in plasma compared with cows fed SES. The additional trans11-18:1 was found exclusively in plasma triglycerides, whereas the additional cis9,trans11-18:2 was found in plasma phospholipids and free fatty acids. Daily yields of 18:2n6, trans11-18:1 and cis9,trans11-18:2 in milk fat were greater for cows fed MES or MESM compared with SES. Results indicate yields of trans11-18:1, cis9, trans11-18:2, 18:2n6, and 18:3n3 in milk fat of pasture-fed cows were enhanced by feeding a grain supplement containing mechanically extracted, rather than solvent-extracted, soybean meal.
Loor
J J
JJ
Dairy Science Department, Virginia Tech, Blacksburg 24061-0315, USA.
Herbein
J H
JH
Polan
C E
CE
D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000378:metabolism*; D019587:Dietary Supplements; D005227:Fatty Acids / Q000032:analysis* / Q000097:blood*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D007774:Lactation; D008055:Lipids / Q000032:analysis*; D008892:Milk / Q000737:chemistry*; D010743:Phospholipids / Q000097:blood; D013025:Glycine max; D014280:Triglycerides / Q000097:blood
D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D008055:Lipids; D010743:Phospholipids; D014280:Triglycerides