This distinction could only be made with confidence on BTA1 where a QTL affecting milk yield is linked to a pleiotropic QTL affecting days open and fertility treatments.
The analyses of the effect of BRL on milk yield were carried out in 2 steps, where the average 305 day kg energy corrected milk yield (305 day kg ECM) in the last full lactation was described for cows with and without BRL, stratified by parity (2, 3, 4 and > 5) and breed (Danish Holstein and Danish Red).
Clinical ketosis was defined as cows in early lactation with inappetence, depressed general condition and reduced milk yield and tested positive for ketone bodies in milk, where the veterinarian found no other explanation for the symptoms.
Estimated persistency was calculated as the difference between the milk yield at peak lactation and an end day, namely (7) where tmax and t end are the time of peak milk yield and the end time (t end = 305 DIM) respectively.
Production responses to increasing CP were increased dry matter intake (DMI), milk and component yield, and feed efficiency (milk Mcal/kg of DMI), and decreased milk N:intake N. Response in milk yield and feed efficiency to increased CP interacted with experimental design where continuous experiments had greater milk yield and feed efficiency response at higher levels of CP.
Total milk yield available was significantly higher among years for wealthy families, except for 2008 where rich families have less access to milk than poor or middle class families (p > 0.05).
This implies that there is considerable value in selecting for heterozygosity in regions where homozygosity has an unfavourable effect on valuable traits, such as fertility and milk yield.
These results support that in pasture-based systems of dairy production, where energy intake limits milk production, energy spared by CLA-induced milk fat depression is partitioned toward increasing milk yield rather than toward body reserves.
It was calculated as a linear combination of milk yield, fat yield and protein yield, i.e., energy yield = 0.802 x milk yield + 38.4 x fat yield + 23.6 x protein yield, where the yields are measured in kilograms (Nostitz and Mielke 1995).
