Efecto del uso de aditivos alimentarios sobre parámetros de fermentación ruminal y población de protozoarios en vacas lecheras

The need to meet the demands of international markets and to ensure sustainable production practices underscore the challenge of improving rumen fermentation. The use of antibiotics, such as monensin, has achieved this goal, but concerns about the potential development of resistance are prompting research into alternatives such as plant extracts. The aim of this research was to assess the impact of monensin and a blend of plant extracts on ruminal fermentation in dairy cows during the transition and early lactation period within mixed grazing systems. Employing a completely randomized design with repeated measures over time, nine fistulated Holstein cows were allocated to one of three treatments: monensin (MON; 300 mg/animal/day), plant extracts (EXP; 50 g/animal/day) containing trans-cinnamaldehyde, flavonoids, curcuminoids, and piperine, and a control treatment (CON) devoid of additive supplementation. Thirty days prior to the anticipated calving date, the animals entered the prepartum phase, being housed in a compost barn system and consuming a total mixed ration (TMR) that incorporated the additive in the concentrate, as per the respective treatment. Following calving, they were managed within a mixed feeding system, undergoing a grazing session between milkings (05:00 and 16:00 hrs) and confinement post-evening milking. Ruminal fluid samples were collected at -11, +33, and +63 days relative to the average calving date to assess pH, ammonia nitrogen (N-ammoniacal), total volatile fatty acids (AGVt), acetic (C2), propionic (C3), butyric (C4) acids, and protozoa population. Sampling was conducted over two consecutive days at 0, 4, 8, 16, and 24 hrs post-feeding. During the prepartum period, ruminal pH concentration, N-ammoniacal, AGVt, C2, C3, C4, and C2/C3 ratio were unaffected by the treatments; however, the protozoa population was significantly lower in the MON and EXP treatments in comparison to CON (p=0.008). In the postpartum phase, N-ammoniacal and C4 concentrations were significantly lower in the EXP treatment relative to MON and CON groups (p<0.0001 and p=0.0001, respectively), and the protozoa population was lower in the MON and EXP treatments compared to CON (p<0.0001). In conclusion, feed additives constitute a strategy to improve rumen fermentation in dairy cows during transition and early lactation in mixed grazing systems. However, further research into their potential to modulate the rumen microbiota is warranted. A more comprehensive understanding of the use of additives in transitioning dairy cows in mixed systems will prove valuable in increasing the production efficiency of dairy production systems in Uruguay.