Effects of CLA supplementation in diets with different levels of forage NDF on ‎performance, serum metabolites and liver functionality in Holstein fresh cows ‎

The aim of this study was to evaluate the effects of CLA supplementation in diets with different levels of forage NDF on performance, serum metabolites and liver functionality in Holstein fresh cows. Forty Cows were blocked based on their body condition score at calving and 305-d mature-equivalent milk yield, and randomly allocated to 1 of 4 experimental diets from calving to 21 days in milk (DIM). Treatments were used in a 2×2 factorial arrangement with 2 levels of fNDF and 2 doses of CLA supplement; Treatments were formulated to contain 18.0 or 23.0% fNDF without or with CLA supplement for diets 18fNDF-CLA, 18fNDF+CLA, 23fNDF-CLA and 23fNDF+ CLA. There was no effect of fNDF by CLA interaction on investigated items. Dry matter intake increased up to 1.5 kg with 18fNDF diet compared to 23FNDF (P<0.01), while the addition of CLA reduced the dry matter intake to 1.15 kg/d compared to diets without CLA supplementation (P<0.01). Cows fed 23fNDF diet lost more body weight than those fed 18fNDF. Milk yield was higher for cows fed 18fNDF than 23fNDF (P<0.01). Cows fed diets containing CLA produced more milk, lower milk fat percentage, and higher lactose content. (P<0.05). Serum glucose was higher in cows fed CLA-containing diets (P<0.01). Cows fed 18fNDF had lower serum concentrations of NEFA and BHBA compared to those fed 23fNDF (P<0.05), but CLA supplementation did not affect serum NEFA and BHBA (P>0.05). (P<0.05). In general, the reduction of forage NDF in the diet of fresh cows led to improved feed intake and production performance. Addition of CLA to the diet of fresh cows led to glucose savings by reducing fat synthesis, increasing lactose content and milk production.