ARTICLE 84 FEED & ADDITIVE MAGAZINE September 2023 Results from the meta-analysis indicated that supplementing RPC during the transition phase led to a notable increase in energy-corrected milk yield by an average of 2,2 kg/day. Furthermore, there was a tendency for a reduction in the incidence of retained placenta and mastitis among the supplemented cows compared to their non-supplemented counterparts. Interestingly, the changes in energy-corrected milk yield and milk component yields exhibited a linear relationship with the amount of choline ion supplementation, up to a threshold of 25,2 g/day. The exact optimal dosage of choline ion supplementation remained uncertain due to this linear response. The meta-analysis also unveiled that the response to choline was influenced by the supply of metabolizable methionine in the postpartum diet. This connection was expected due to the biochemical interactions between choline and methionine within the body, influencing 1-carbon metabolism and phosphatidylcholine synthesis. Even when the lactating diet provided metabolizable methionine at a level of 2,60% of metabolizable protein, supplementing RPC still increased energy-corrected milk yield. A noteworthy observation stemming from the meta-analysis was the dearth of literature investigating the role of supplemental choline in nulliparous cows – those that haven't given birth yet. These nulliparous cows typically comprise around 30 to 35% of the prepartum cow population on dairy farms. While it's anticipated that these cows could also benefit from choline supplementation during the transition period, this remains a relatively unexplored area in research. THE EFFECTS OF RPC ARE OBSERVED REGARDLESS OF THE BODY CONDITION OF COWS Given choline's role in hepatic lipid metabolism and its potential to reduce the risk of fatty liver, it's not uncommon for nutritionists and veterinarians to propose supplementing RPC primarily to over conditioned prepartum cows, which are at an increased risk of developing hepatic steatosis. To investigate this notion, we revisited data from two randomized experiments. In these studies, prepartum cows were divided into groups, with one group receiving 0 g/day of choline ion and the other group receiving 12,9 g/day of choline ion from ReaShure RPC. This supplementation began around 255 days of gestation and continued until 21 days postpartum9. The objective was to ascertain whether the response to RPC was influenced by the body condition of cows upon entering the prepartum group. A total of 215 pregnant parous Holstein cows were enrolled in both experiments, with each cow's body condition score assessed twice before the treatments commenced. The cows' mean body condition was 3,51, ranging from 2,69 to 4,25. The results of this analysis revealed that irrespective of the cows' body condition scores prepartum, supplementing transition diets with 12,9 g/day of choline as RPC yielded consistent positive effects. This supplementation led to increased milk yields by 1,8 kg/day, fat yields by 0,08 kg/day, true protein yields by 0,04 kg/day, energy-corrected milk by 1,9 kg/day, and 3,5% fat-corrected milk by 2,1 kg/day. Additionally, cows that received RPC exhibited enhanced feed efficiency in converting feed into energy-corrected milk, regardless of whether they were under or over conditioned before calving. This study demonstrates that the response to RPC is observed in cows regardless of their degree of fatness at the initiation of prepartum supplementation.
RkJQdWJsaXNoZXIy MTUxNjkxNQ==