www.kimiyaroshd.com-The Effect of Breed, Parity, and Stage of Lactation on Conjugated Linoleic Acid (CLA) in Milk Fat from Dairy Cows_001

Name: The Effect of Breed, Parity, and Stage of Lactation on Conjugated Linoleic Acid (CLA) in Milk Fat from Dairy Cows

Auther: J.A.Kelsey*2B.A.Corl*R.J.Collier†D.E.Bauman*

Addresses:*Department of Animal Science, Cornell University, Ithaca, NY 14853
†Department of Animal Science, University of Arizona, Tucson, AZ 85721

Abstract: Dairy products are the main source of conjugated linoleic acid (CLA), a functional food component with health benefits. The major source of cis-9, trans-11 CLA in milk fat is endogenous synthesis via Δ۹-desaturase from trans-11 18:1, with the remainder from incomplete rumen biohydrogenation of linoleic acid. Diet has a major influence on milk fat CLA; however, effects of physiological factors have received little attention. Our objectives were to examine milk fat content of CLA and the CLA-desaturase index with regard to: 1) effect of breed, parity, and stage of lactation, and 2) variation among individuals and the relationship to milk and milk fat. Holstein (n = 113) and Brown Swiss (n = 106) cows were fed a single diet and milk sampled on the same day to avoid confounding effects of diet and season. Frequency distributions demonstrated that milk fat content of CLA and CLA-desaturase index varied over threefold among individuals, and this needs to be considered in the design of experiments. Holsteins had a higher milk fat content of CLA and CLA-desaturase index, but breed differences were minor. Parity and days in milk also had little or no relationship to the individual variation for these two CLA variables. Breed, parity, and days in milk accounted for <0.1, <0.3, and <2.0% of total variation in CLA concentration in milk fat, respectively. Milk fat content of CLA and CLA-desaturase index were essentially independent of milk yield, milk fat percent, and milk fat yield. We speculate that the basis for the genetic variation among individuals is related to rumen output of trans-11 18:1 and to a lesser extent cis-9, trans-11 CLA, and to the tissue amount and activity of Δ۹-desaturase.

Key words: breed, conjugated linoleic acid, desaturase index, milk fat

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Name: Effect of stearic or oleic acid on milk performance and energy partitioning when fed in diets with low and high rumen-active unsaturated fatty acids in early lactation

Authors: Chen Yanting, Guiling Ma, Joseph H Harrison, Elliot Block

Address:*Department of Animal Science, Washington State University, Pullman, WA 99164, †
Department of Animal Science, Washington State University, Puyallup, WA 98731, and ‡
Church and Dwight Animal Nutrition, Princeton, NJ 08543
۱These authors contributed equally to the research.
۲ Corresponding author: jhharrison@wsu.edu

Abstract: This experiment was conducted to determine the effects of stearic acid (SA; C18:0) or rumen-protected oleic acid (OA; C18:1 cis-9) on milk performance and energy partitioning of early lactation cows when supplemented in diets with low and high level of rumen unsaturated fatty acids (RUFA). In low RUFA experiment (LRUFA), FA supplement rich in either SA or calcium salts OA was added to a basal diet with a low concentration of RUFA (0.75% vs. 1.4%, LRUFA-SA vs. LRUFA-OA). In high RUFA experiment (HRUFA), ۲% soybean oil was added to the diet fed in the LRUFA experiment. In each experiment, 30 multiparous cows were blocked by parity and predicted transmitting ability for milk yield and were randomly fed 1 of 2 treatment diets from 2 to 13 wk postpartum. In the LRUFA experiment, LRUFA-SA had 2.4 kg/d more dry matter intake (DMI) (P < 0.01), 3.8 kg/d more energy-corrected milk (P < 0.01), and 0.3% units more milk fat percentage (P < 0.01) and 0.2 kg/d more milk fat yield (P < 0.01). Dietary treatments did not affect body weight, energy balance, and energy intake partitioning into milk, maintenance, and body tissues (P > 0.1). In the HRUFA experiment, HRUFA-SA had 1.4 kg/d more DMI (P = ۰.۰۳) but similar milk and milk components yields (P > 0.1). HRUFA-SA had a tendency to gain more body weight (P = ۰.۰۷) and had more positive energy balance (P = ۰.۰۱) and decreased gross feed efficiency (milk yield/DMI) (P = ۰.۰۱). Consistently, HRUFA-SA increased intake energy partitioning into body tissues (P = ۰.۰۲) and decreased energy partitioning into milk (P = ۰.۰۱). In summary, SA supplementation had more DMI relative to OA, but the effects on milk and milk fat production were different and affected by the level of RUFA in the basal diet. In application, SA supplementation was more effective to improve milk production when included in the basal diet with the low RUFA.

Key Words: dairy cows, fatty acids, milk fat, ruminal bio hydrogenation

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