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.
Milk fat was investigated in lactating dairy cows fed diets supplemented with Ca salts of trans fatty acids (Ca-tFA) or Ca salts of conjugated linoleic acids (Ca-CLA). Forty-five Holstein cows (115 days in milk) were fed a control diet (51% forage; dry matter basis) supplemented with 400 g of EnerG II (Ca salts of palm oil fatty acids) for 2 wk; subsequently, 5 groups of 9 cows each were assigned for 4 wk to the control diet or diets containing 100 g of Ca-CLA or 100, 200, or 400 g of Ca-tFA in a randomized block design. Treatments had no effect on dry matter intake, milk production, protein, lactose, or somatic cell count. Milk fat percentage was reduced from 3.39% in controls to 3.30, 3.04, and 2.98%, respectively, by the Ca-tFA diets and to 2.54% by the Ca-CLA diet. Milk fat yield (1.24 kg/d in controls) was decreased by 60, 130, and 190 g/d with increasing dose of Ca-tFA and by 290 g/d with the Ca-CLA supplement. Consistent with increased endogenous synthesis of cis-9-containing CLA from precursors provided by the Ca-tFA diets, total CLA were similar in milk of cows fed Ca-CLA or Ca-tFA. Compared with controls, the Ca-CLA diet increased trans-10, cis-12-18:2 yield in milk, without altering levels of trans-18:1 isomers. In contrast, yields of most trans-18:1 isomers were elevated in milk of cows fed Ca-tFA diets, whereas yields of trans-10, cis-12-18:2 remained similar to control values. We conclude that milk fat depression can occur without an increase in trans-10, cis-12-18:2 in milk and that other components, perhaps the trans-10-18:1 isomer, may be involved.
Animal and Avian Sciences Department, University of Maryland, College Park 20742, USA.
L S
LS
Piperova
U
U
Moallem
B B
BB
Teter
J
J
Sampugna
M P
MP
Yurawecz
K M
KM
Morehouse
D
D
Luchini
R A
RA
Erdman
D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002118:Calcium / Q000008:administration & dosage* / Q000494:pharmacology; D002417:Cattle / Q000502:physiology*; D003612:Dairying / Q000379:methods; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D007536:Isomerism; D007774:Lactation / Q000502:physiology*; D019787:Linoleic Acid / Q000008:administration & dosage* / Q000032:analysis; D008055:Lipids / Q000032:analysis; D008892:Milk / Q000737:chemistry* / Q000378:metabolism; D000073878:Palm Oil; D010938:Plant Oils; D011897:Random Allocation; D012417:Rumen / Q000378:metabolism; D044242:Trans Fatty Acids / Q000008:administration & dosage* / Q000032:analysis
D008055:Lipids; D010938:Plant Oils; D044242:Trans Fatty Acids; D000073878:Palm Oil; D019787:Linoleic Acid; D002118:Calcium