Priming the cow for lactation by rapeseed supplementation in the dry period

High-producing dairy cows experience a sudden and significant increase in energy requirements due to the onset of milk production in early lactation. They mobilize body reserves, mainly adipose tissue, resulting in an increased risk of production decline and the development of health disorders. The objective of the present study was to investigate the effects of feeding oilseeds (rapeseed) during the dry period, thereby priming dairy cows for metabolism of body fat in early lactation. Forty-three Holstein dairy cows were used, 14 were primiparous and 29 were multiparous (≥2nd lactation). In the dry period, 8 wk before expected calving until calving, the cows were fed either a diet with a high content of rapeseed in the total mixed ration (HF) or a standard total mixed ration with a low content of fat (CON). During the first 5 wk after calving, all the cows were fed a standard low fat lactation ration. The treatments were evaluated by performance and metabolic variables in blood and liver. The dry period diet had no effects on body weight and body condition score of the cows during the dry period and in early lactation. The daily yield of milk, protein, and lactose did not differ among treatments. However, the milk fat concentration was lower and the daily milk fat production tended to be lower for the cows fed the HF diet in the dry period compared with the cows fed the CON diet. The plasma content of nonesterified fatty acids, cholesterol, and phospholipids in the dry period was increased in the HF dry period diet compared with the CON diet. The lower plasma concentration of uric acid obtained prepartum for the cows fed the HF diet may indicate a lower rumen microbial protein synthesis. Postpartum, the plasma concentration of β-hydroxybutyric acid tended to be lower for the cows fed the HF dry period diet. The liver content of triglycerides was lower and the liver content of glycogen was higher in early lactation among the cows fed the HF dry period diet compared with the cows fed the CON diet. Based on liver glycogen, triglyceride content, and blood β-hydroxybutyric acid concentration, it could be argued that intake of oilseeds during the dry period is a positive strategy for priming dairy cows for fat metabolism in the following early lactation.