Metzger-Petersen, Katrin: Supplementation of a rumen-protected conjugated linoleic acid mixture (cis-9, trans-11; trans-10, cis-12) to early lactation dairy cows : effects on feed intake and performance. - Bonn, 2013. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc:
author = {{Katrin Metzger-Petersen}},
title = {Supplementation of a rumen-protected conjugated linoleic acid mixture (cis-9, trans-11; trans-10, cis-12) to early lactation dairy cows : effects on feed intake and performance},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2013,
month = jun,

note = {Conjugated linoleic acids (CLA) are geometric and positional isomers of linoleic acid with conjugated double bonds. Cis-9, trans-11 and trans-10, cis-12 CLA are the two most intensively studied isomers. The cis-9, trans-11 isomer has been mainly studied with respect to improved human diet and health issues, whereas studies considering trans-10, cis-12 CLA have mainly investigated the effects on ruminant nutrition because of its dose-dependent milk fat depressing properties. Most studies have been performed in the United States of America; however, all of them were time-limited, and did not follow the effects of a restricted CLA feeding period throughout lactation. This has led to one main objective of this thesis, which includes a study where a rumen-protected mixed CLA source (3.22 g/d and 3.36 g/d trans-10, cis-12 CLA and cis-9, trans-11 CLA, respectively) was fed for a) 80 d and b) 120 d starting 6 d after parturition. The total observation period was 240 d. Furthermore, a study was performed investigating the effects of supplementation with 4.96 g/d each of trans-10, cis-12 CLA and cis-9, trans-11 CLA as a rumen-protected mixed CLA product starting during the transition period and early lactation (d 18 a.p. to d 80 p.p.). Performance in milk was observed for 100 days.
The results reveal a tendency for depressed milk fat content across the entire lactation period in the long term (100 d) by transition feeding with CLA. The milk yield tended to increase with CLA feeding across the lactation period, depending on the duration of supplementation. These results, however, are only valid for multiparous cows. It seems as if primiparous cows react differently upon CLA-induced milk fat depression. No effects on milk fat were visible in this case. Dairy cows fed CLA during the transition period showed a quicker reduction in milk fat content after parturition than if feeding started after parturition. It seems as if the period of lactation at which the CLA supplementation is terminated has an influence on the recovery of milk fat content. The energy balance could have an effect, since animals in positive energy balance mobilize fatty acids that were retained beforehand. No differences between the American studies and the present study could be found. No effects of CLA product supplementation were detected on the amount of energy corrected milk yield, dry matter intake, live weight, energy balance, ketosis indices.},

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