Tolerance study of rumen protected conjugated linoleic acid on dairy cows during the transition and early lactation period

Abstract Text: The objective of the current study was to investigate the effects of dietary addition of rumen protected conjugated linoleic acids (CLA) on lactation performance and blood biochemical and hematological parameters of dairy cows during transition and early lactation period, and to evaluate the acute toxicity when it was added with the 10-fold of the recommended level. Twenty-seven perinatal Holstein cows were selected based on their parity and milk production of previous lactation and assigned to 1 of 3 treatments according to a randomized complete block design: (1) Basic diet added with no extra CLA (control); (2) 50 g/d of CLA per head (recommended level); and (3) 500 g/d of CLA per head (10-fold of the recommended level). The CLA used in this trial contained 12.0 % of cis-9, trans-11 and 11.9% of trans-10, cis-12 CLA isomer. The experiment started 3 weeks before expected calving day and finished at 8 weeks after calving. Milk yield was recorded and milk samples were collected to analyze milk composition weekly. The blood samples was collected on d 21 and 10 prepartum; d 1 and week 1, 2, 4, and 8 postpartum to analyze the blood biochemical and redox parameters. An aliquot of blood samples collected on d 21 prepartum and 8 weeks postpartum were used for hematological analysis. Addition of CLA did not exert significant effects on dry matter intake, milk yield, content and yield of milk protein and lactose, and somatic cell count (P>0.10). Compared with control and recommended dose group, CLA addition at 500 g/d significantly reduced content and yield of milk fat, milk urine nitrogen and total solids content (P<0.01). No significant differences were observed in hematological parameters including red blood cell count, hematocrit, hemoglobin, white blood cell count and its differential count and percentage, platelet count among groups (P>0.10). Addition of CLA significantly decreased plasma levels of non-esterified fatty acids (P<0.05), which is beneficial for alleviating negative energy balance status of dairy cows. The CLA also tended to improve the total antioxidant capacity (P=0.09). There were no significant differences in plasma glucose, total protein, albumin, globulin to albumin ratio, creatinine, alanine transaminase, aspartate aminotransferase, and alkaline phosphatase among the three groups (P>0.10). These results indicated that there is no adverse effects of CLA addition on dairy cows’ health even at a 10-fold of recommended dose.

.

Keywords: conjugated linoleic acids, dairy cows, tolerance