fatty acid composition of muscle fat and subcutaneous adipose tissue of pasture-fed beef heifers: Influence of the duration of grazing

• Published in: Journal of animal science Vol. 83; no. 5; pp. 1167 - 1178
• Main Authors: Noci, F, Monahan, F. J, French, P, Moloney, A. P
• Format: Journal Article
• Language: English
• Published: Savoy, IL Am Soc Animal Sci 01.05.2005; American Society of Animal Science; Oxford University Press
• Subjects: ad libitum feeding; adipose tissue; Adipose Tissue - chemistry; Animal Feed - analysis; animal growth; Animal productions; Animals; Beef; beef cattle; beef quality; Biological and medical sciences; Body Composition; Body fat; carcass weight; Cattle; Cattle - metabolism; Charolais; Chromatography, Gas - veterinary; conjugated linoleic acid; cow feeding; crossbreds; Diet; fatty acid composition; Fatty acids; Fatty Acids - analysis; feed concentrates; Feeding Methods - veterinary; Female; Food industries; Fundamental and applied biological sciences. Psychology; grass silage; grazing; grazing management; heifers; Linoleic Acids, Conjugated - analysis; lipid content; Lipids - analysis; Lolium perenne; Meat and meat product industries; Muscles - chemistry; omega-3 fatty acids; omega-6 fatty acids; Pastures; polyunsaturated fatty acids; Random Allocation; saturated fatty acids; subcutaneous fat; Subcutaneous Fat - chemistry; Terrestrial animal productions; Time Factors; Vertebrates; Adipose tissue; Polyunsaturated fatty acid; Meat product; Ox; Lipids; Grazing; Fatty acids; Linoleic acid; Conjugated Linoleic Acid; Vertebrata; n-6 fatty acid; Mammalia; Pasture; Beef cattle; Fat; Influence; Chemical composition; Heifer; Muscle; Artiodactyla; Beef; Subcutaneous tissue; Ungulata
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/2005.8351167x

Our objective was to determine the effect of the duration of grazing before slaughter on the fatty acid composition of muscle fat and s.c. adipose tissue (SAT) of beef heifers. Sixty crossbred Charolais heifers (n = 15 per treatment) were assigned randomly to one of four dietary treatments: 45 animals (Treatments 1, 2, and 3, respectively) were housed at the beginning of the experiment, and 15 (Treatment 4) were fed at pasture. Two groups of 15 heifers were moved to pasture 40 d (Treatment 2) and 99 d (Treatment 3) before slaughter, respectively, resulting in preslaughter grazing periods of 0, 40, 99, or 158 d for Treatments 1, 2, 3, and 4, respectively. Before grazing the predominantly perennial ryegrass pasture, animals were housed and offered grass silage ad libitum and 3 kg of concentrate diet (650 g of grass silage/kg of total DMI). After slaughter, the fatty acid profile of the neutral (NL) and polar lipid (PL) fractions of muscle fat from the LM and the total lipids from SAT were analyzed by gas chromatography. Duration of grazing showed a quadratic tendency on mean carcass weight (P = 0.08), but did not affect growth (P = 0.27) or the lipid content (P = 0.13) of the LM. Increasing the duration of grazing led to a linear increase (P < 0.001) in the concentration (on fresh-tissue basis) of CLA in muscle fat (from 11.80 to 17.75 mg/100 g of muscle in NL, and from 0.52 to 0.82 mg/100 of g muscle in PL) and in SAT (from 3.98 to 10.23 mg/g of SAT; P < 0.001), and increased the concentration of C18:1trans-11 in both muscle fat fractions (P < 0.001) and in SAT (P < 0.001). In the total muscle lipids, the polyunsaturated to saturated fatty acid ratio (P:S) increased from 0.12 to 0.15 with increased duration of grazing following a linear (P < 0.05) and cubic pattern (P < 0.05). Increasing the duration of grazing led to a linear decrease in the n-6:n-3 ratio of muscle fat from 2.00 to 1.32 (P < 0.001), and from 2.64 to 1.65 in the SAT lipids (P < 0.001), mainly as a consequence of the increased concentration of C18:3n-3. It is concluded that muscle fat and SAT fatty acid profile was improved from a human health perspective by pasture feeding, and that this improvement depended on the duration of grazing.