Dairy

This study examined the effects of average daily gain (ADG) during gestation on growth, nutrient digestibility, metabolic response, and subsequent milk yield and composition in dairy heifers. Twenty pregnant Holstein × Gyr heifers (450 ± 5.0 kg; 18 ± 1.1 months) were randomly assigned to moderate (MOD; target 0.35 kg/day) or high (HIG; target 0.70 kg/day) ADG groups, and received a total mixed ration from day 70 of gestation until calving. Body growth, blood metabolites, and lactation performance after birth were measured. At calving, HIG heifers had greater body weight (p < 0.01) and thoracic perimeter (p = 0.02). Nutrient digestibility and most blood metabolites were not affected by ADG (p > 0.05), except for triiodothyronine concentrations, which differed between treatments over time (p < 0.01). Milk yield and energy-corrected milk were not affected by gestational ADG (p > 0.10), while milk fat and total solids showed numerical treatment × week interactions (p ≤ 0.10). These results indicate that higher ADG during gestation increases body reserves at calving but does not affect milk yield. The moderate ADG for Holstein × Gyr heifers during gestation may improve milk quality through higher fat and solids content, emphasizing the importance of tailoring growth strategies for heifers during gestation.

The transition period, spanning approximately three weeks before and after parturition, represents one of the most critical physiological windows in dairy production. Profound metabolic, endocrine, and immune adaptations occur as the cow shifts from gestation to lactation, predisposing high-yielding cows to oxidative stress, inflammation, and metabolic imbalance. Negative energy and metabolisable protein balances stimulate extensive lipolysis and the accumulation of non-esterified fatty acids (NEFAs) and β-hydroxybutyrate (BHBA), which can impair hepatic function and postpartum performance. This review integrates recent advances in the understanding of metabolic and immunometabolic regulation during transition, emphasising the interplay among energy metabolism, oxidative stress, and immune dysregulation. It critically re-evaluates current nutritional interventions including controlled-energy and negative DCAD diets, rumen-protected polyunsaturated fatty acids, and methyl donor amino acids while highlighting the emerging potential of injectable trace minerals as adjunct strategies to improve metabolic resilience. The review concludes by outlining remaining knowledge gaps and proposing a framework linking physiological mechanisms with targeted nutritional management.

Colonial cheese production represents a valuable cultural and economic activity in southern Brazil. This study evaluated the effect of oral supplementation of dairy cows with an essential oil blend (EOB)—a combination of eucalyptus oil, peppermint oil, and menthol crystals—on the chemical composition and quality parameters of Colonial cheese during 21 days of ripening. Nine dairy cows were randomly assigned to three groups: control, EOB3.6 (3.6 g/cow/day), and EOB7.2 (7.2 g/cow/day). Milk from each treatment was used to produce Colonial cheeses, which were analyzed for physicochemical composition, texture, color, lipid profile, thiobarbituric acid reactive substances (TBARS), and microbiological quality at different ripening stages. Data were analyzed by analysis of variance (ANOVA) using SAS^® software, following verification of normality and homogeneity of variances. When assumptions were met, repeated-measures ANOVA was applied, and means were compared using Tukey’s test (p < 0.05). Sensory data were evaluated by ANOVA using XLSTAT^® (Addinsoft, Paris, France). EOB supplementation maintained the physicochemical integrity of the cheeses, with a gradual increase in fat content during maturation (40 g/100 g at 21 days, p < 0.05). At seven days, the EOB7.2 treatment showed lower lipid oxidation (TBARS = 0.063, p < 0.05), indicating antioxidant potential. Significant interactions between treatment and maturation were observed for color parameters and polyunsaturated fatty acids (PUFA) (p < 0.05). Cheeses from EOB7.2 presented higher saturated fatty acids (SFA) and lower unsaturated fatty acids (UFA) compared with the control (p < 0.05). No Salmonella spp. or Staphylococcal enterotoxins were detected. Counts of coagulase-positive Staphylococcus, molds, and yeasts remained stable, while Escherichia coli counts were lower in EOB-supplemented cheeses throughout ripening. Overall, EOB supplementation improved oxidative stability and microbiological safety without compromising the technological or compositional quality of Colonial cheese.