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Title: Effects of conjugated linoleic acid on the performance and metabolism of dairy ewes
Author: Weerasinghe, W. M. P. B.
Awarding Body: Harper Adams University College
Current Institution: Harper Adams University College
Date of Award: 2008
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Four experiments were conducted to investigate the effects of conjugated linoleic acid (CLA) on the performance and metabolism of dairy ewes. In experiment 1, the effects of oil source, feed and pH on biohydrogenation of C18:2n-6 and production of CLA was assessed invitro. Biohydrogenation of C18:2n-6 increased with increasing vessel pH whilst the formation of cis-9, tnms-ll CLA and tralls-lO, cis-12 CLA were related to the initial vessel content of C18:2ti-6. A combination of a high starch diet and low vessel pH resulted in the highest concentration of trans-lO, cis-12 CLA, whilst cis-9, trans-l1 CLA content was greater with a high forage diet and high vessel pH. In experiment 2, the effects of starch level and forage particle length on the performance and milk fat content of CLA in dairy ewes was examined. Feeding high starch diets to ewes increased DMI and reduced milk fat content by proportionately 0.08. Milk fat trans-lO, cis-12 CLA content was not affected by dietary treatment but cis-9, trans-II CLA increased in milk from ewes when fed the low starch diets. In experiment 3, the effects of a rumen protected source of tralls-l0, cis-12 CLA and cis-9, trans-l1 CLA on the performance of dairy ewes fed at a restricted energy intake and differing metabolizable protein (MP) content was assessed. Supplementation with CLA reduced milk fat content, fat yield and milk protein content by 0.33, 0.24 and 0.03 respectively but increased milk yield and yields of milk protein and lactose by 0.14, 0.12 and 0.15 respectively. Compared with low MP, high MP diets resulted in 0.15, 0.16 and 0.14 higher yields of milk, milk protein and lactose respectively. Milk fat content of tnms-lO, cis-12 CLA and cis9, t~alls-ll CLA were increased due to CLA supplementation. In experiment 4, the dose effect of CLA on performance, carcass characteristics and tissue fatty acid composition of dairy ewes was examined. Ewes fed high CLA (H-CLA) had 0.13 higher milk yield compared with those fed the control (C) or low CLA (L-CLA). Compared with the animals fed the control diets, milk fat content was reduced incrementally by 0.15 and 0.34 and fat yield reduced incrementally by 0.14 and 0.24 for L-CLA and H-CLA respectively. Inclusion of CLA increased tralls-lO, cis-12 CLA and cis-9, tralls-l1 CLA in milk fat, and mammary, liver, heart, muscle and perirenal fat, but tissue total fat content and tissue levels of Acetyl-eoA carboxylase and Stearoyl-CoA desaturase mRNA was not affected by dietary treatment.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available