RESUMO
Supplemental n-3 fatty acids (FA) may support better immune responses than n-6 and n-9 FA in dairy calves. The objective was to evaluate the effect of n-3 FA, supplemented as a fish oil product (FO) in the milk replacer (MR), in comparison to n-6 and n-9 FA, supplemented as canola oil (CO), on body weight (BW), daily gain, and immunological parameters of preweaning Holstein calves. The study was conducted from September to December 2019. Calves were randomly allocated to a control group (n = 15; BW = 36.2 ± 1.5 kg; mean ± SEM) supplemented daily with 30 mL of CO and to an experimental group (n = 15; BW = 36.3 ± 1.5 kg) supplemented with 60 g of a product containing 30 g of FO. Both treatments were added to the MR during the morning feeding. All calves were fed 4 L of MR at 12.5% solids at 0700 and 1600 h for wk 1, 6 L from wk 2 to 7, and 3 L once daily (0700 h) during wk 8 until weaning (56 d). Blood samples were collected at 7, 14, 21, 28, 35, 42, 49, and 56 d of age for serum haptoglobin, TNF-α, IL-1ß, and protectin. Dry matter intake was recorded in all experimental calves daily. Seroneutralization titers to vaccination against viral diseases (infectious bovine rhinotracheitis, parainfluenza 3, bovine viral diarrhea, and bovine respiratory syncytial virus) were determined. Mixed models for repeated measures were developed to analyze variables over time. Seroneutralization titers were analyzed by the Kruskal-Wallis test. The other variables were compared by a generalized linear model. Serum FA profile at 35 d of age showed that FO supported higher concentrations of n-3 FA than CO. Final BW [65.2 vs. 62.0 kg, standard error of the mean (SEM) = 2.1 kg] and average daily gain (0.52 vs. 0.46 kg/d, SEM = 0.1 kg/d) tended to be higher for the FO than the CO group. An interaction of treatment × day for dry matter intake was observed, especially during weaning (2.17 kg vs. 1.94 kg, SEM = 0.158 kg, for FO and CO group, respectively). Blood lactate (mmol/L) was higher in the CO than in the FO group at d 7. Haptoglobin and IL-1ß were higher for the CO group on d 14 than the FO group. The TNF- α concentrations for the FO group were reduced over time, whereas the concentrations in the CO group remained constant. Protectin was higher in the FO group on d 14, but was lower on d 28, 35, and 49. Seroneutralization antibody titers postvaccination for the PI3 virus were higher for the FO than the CO group. In conclusion, calves supplemented with FO had lower concentrations of blood lactate, haptoglobin, IL-1ß and TNF-α than calves supplemented with CO during the study period. The FO supplementation had a higher DMI than CO supplementation. Results of this trial should be interpreted with caution due to the lack of a negative control group as well as the lower birth weight and growth rate observed under heat stress conditions.
Assuntos
Ração Animal , Óleos de Peixe , Ração Animal/análise , Animais , Peso Corporal , Bovinos , Dieta/veterinária , Suplementos Nutricionais , Ingestão de Alimentos , Leite , Óleo de Brassica napus , DesmameRESUMO
The use of anionic salts to prevent milk fever in dairy cattle has been an effective nutritional strategy; however, the degree of acidification that determines the most acceptable productive responses and well-being of the cow is still a controversial topic. The objective of this study was to assess urine pH in prepartum Holstein cows fed anionic diets and determine its association with plasma total Ca, Mg, P, ß-hydroxyl-butyrate (BHB) concentrations at parturition and the occurrence of peripartum disorders. This investigation consisted of 2 studies. Study 1 was conducted on a grazing dairy. Between February and May 2019, 60 prepartum multiparous cows were tested for urine pH and plasma metabolite concentration at parturition. Total Ca, P, Mg and BHB at day 1 in milk (DIM) were assessed and statistically analyzed by ANOVA (models for polynomial regression). Study 2 was conducted on a drylot dairy farm. Between July 2018 and January 2019, 203 cows were evaluated for urine pH and followed-up for 30 DIM to obtain the incidence of dystocia, stillbirths, milk fever, retained fetal membranes, metritis, clinical mastitis and ketosis. Cows were categorized based on their last urine pH as group 1: pHâ¯>â¯7.0 (nâ¯=â¯135); group 2: pH between 6.0 and 7.0 (nâ¯=â¯46) and group 3: pHâ¯<â¯6.0 (nâ¯=â¯22). A logistic regression model for each health event was conducted considering urine pH group as the main effect. Urine sample was collected at 2.71⯱â¯2.84â¯days before parturition. In study 1, there was a quadratic effect of urine pH on total Ca. Total Ca concentration was higher between urine pHâ¯6.0 and 7.0, while decreasing below pHâ¯6.0 and above pHâ¯7.0. There was a trend (Pâ¯=â¯0.11) for a quadratic effect of urine pH on the concentration of plasma BHB at parturition. ß-Hydroxyl-butyrate was lower approximately between urine pHâ¯6.5 and 7.5. In study 2, the odds for a stillborn in cows with urine pHâ¯<â¯6.0 was 2.39 (95% CIâ¯=â¯1.06-5.40) times the odds for a stillborn in cows with urine pHâ¯≥â¯7.0. There was no association between urine pH and the other diseases. In conclusion, cows with prepartum urine pHâ¯<â¯6.0 and >7.0 had lower concentration of plasma total Ca and tended to have a higher concentration of BHB. Cows with urine pHâ¯<â¯6.0 had a higher incidence of stillbirths than cows with urine pHâ¯>â¯7.0.