view - Department of Reproduction, Obstetrics and Herd Health

CHAPTER 6
quest for the optimal breeding FA composition of dairy rations. This has resulted in
experiments illustrating improved (Cerri et al., 2009; Fouladi-Nashta et al., 2007; Zachut
et al., 2010), but also unaltered (Bilby et al., 2006; Fouladi-Nashta et al., 2009) or even
hampered (Sklan et al., 1994) fertility when feeding UFA to dairy cows.
Furthermore, feeding 22:6n-3 increased the blood lipid peroxidation in transition
cows, elevating the animals to a higher level of susceptibility to oxidative stress (OS)
(Wullepit et al., 2012) which has been linked to embryonic death in the bovine (Fujitani
et al., 1997; Olson and Seidel, 2000; Rooke et al., 2012). The latter might explain in vitro
observations of detrimental effects at high doses of UFA and may confound in vivo
experiments supplementing UFA to increase oocyte and embryo quality in dairy cows. A
multi-study analysis of de Veth et al. (2009) documented a positive effect of trans-10,
cis-12 conjugated linoleic acid (CLA) over 5 studies on days in milk to conception
(DIMCONC) in dairy cows but this kind of analysis has not been conducted for other UFA.
Therefore, the hypothesis of the current study was that high milk UFA are associated
with better fertility parameters in dairy cows. The objective of this study was to analyse
a large dataset containing individual fertility records from dairy herds and link fertility
key-performance-indicators (KPI) to the level of UFA in bulk tank samples as a proxy for
the dietary fatty acid profile on that herd (Lock and Bauman, 2004; Woods and Fearon,
2009).
MATERIALS AND METHOD
RECORD COLLECTION AND DATA HANDLING
Herd level data was collected from 90 dairy herds in Belgium via an automated
herd record collection system (Dairydatawarehouse, Assen, The Netherlands) in 2008
and 2009. Herds without official milk recording were excluded from the analysis. Herd
level data such as the number of calvings within each year (HERDSIZE) and the average
milk production within 305 d (M305) per year were collected. From these 90 herds, bulk
milk tank information was collected via the official Milk Control Centre of Flanders
(Melk Controle Centrum Vlaanderen, Lier, Belgium). For this part of Belgium, typical
bulk tank milk samples are taken every 2 to 3 days depending on the size of the herd.
Samples were analysed for milk protein (PROT), fat (FAT) and the percentage of UFA.
For the study period, cow level information from 15,055 lactations from the
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