A field trial was conducted on a commercial Parmigiano-Reggiano farm to evaluate the effects of dietary supplementation of a microencapsulated organic acids and botanicals product (AviPlus R®, Vetagro S.p.A, Italy) on lactation performance during summer season (July to September 2020). Twenty multiparous non-pregnant Holstein cows (43 ± 13.6 days in milk [mean ± SD], 2.7 ± 0.86 lactation, and 43.3 ± 3.87 kg of milk yield) were enrolled in a study with a completely randomized design. Cows were assigned to one of two groups (n = 10/group) fed a basal diet supplemented with 25g/d of AviPlus®R (TRT; 75 mg/kg of body weight; 25% citric acid, 16.7% sorbic acid, 1.7% thymol, 1.0% vanillin, and 55.6% triglyceride) or basal diet supplemented equivalent triglyceride used for microencapsulation (CTR). Environmental temperature-humidity index (THI) was recorded hourly and individual milk yield was recorded daily. Rectal temperature measurement and milk components analysis were conducted every 2 weeks. Cows were milked twice daily. Data were analyzed under a mixed model with the random effect of cow and the fixed effects of parity, date and days in milk, treatment and their interaction. Both groups were under heat stress conditions (THI: diurnal change 72 to 82) for the whole study period with no differences between them (P = 0.46). Rectal temperature was lower in TRT group compared to CTR (38.18 vs 38.57 Cº, respectively; P < 0.05). Milk yield was greater for TRT compared to CTR (41.86 vs 39.51 kg/d, respectively; P < 0.01). Milk protein, casein and lactose yields were also greater for TRT relative to CTR (1.31 vs 1.22, 1.04 vs 0.95 and 2.12 vs 1.91 kg/d, respectively; P <0.01). Although no differences were detected for milk fat yield (P = 0.29), yields of energy-corrected milk tended to be higher for TRT group compared to CTR (39.80 vs 38.32 kg/d; respectively, P = 0.12). These results suggest that dietary supplementation of microencapsulated organic acids and botanicals is a means to sustain lactation performance in dairy cattle experiencing heat stress.
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