The effects of supplementation of β-carotene during the close-up period on cows, colostrum, and calves

Due to consumer demands, the dairy industry needs to investigate ways to keep dairy cattle healthy, productive, and profitable while minimizing the use of drugs. One way to accomplish this may be by inclusion of antioxidants in the diet. An important antioxidant that should be considered is β-carotene. β-Carotene is found naturally in many plants and is a dual-purpose nutrient, having both provitamin A and antioxidative functions. Ingested β-carotene can be cleaved into two molecules of retinol if the animal is in need of retinoids. If vitamin A stores are sufficient, β-carotene will be used to help dispose of potentially harmful reactive oxygen species. Reducing oxidative stress may help cows restore their positive energy balance following parturition, as well as possibly decrease pneumonia in young calves. Our objective for this study was to determine the effects of β-carotene supplementation on the cow, her colostrum, and her calf. The trial was conducted on a large, commercial dairy farm in northern Indiana. Ninety-four multiparous Holstein cows were assigned to either a treatment or control group. Each cow individually received a concentrate mix topdressed on to her TMR while in a headlock each morning beginning 21 d prior to expected calving and ending at calving. The treatment group was supplemented with 8 g of Rovimix (800 mg of β-carotene) in the topdress. Body condition score was taken on day of enrollment (d -21) and upon trial completion (d 7). Blood samples were obtained from cows on d -21, -7, 0, and 7 relative to calving. All samples were protected from light. Whole blood samples were analyzed for β-carotene using an iCheck (BioAnalyt; Teltow, Germany) immediately following collection. Serum samples were frozen at -20ºC for later analysis. Similarly, blood samples were collected from the calves at d 0, 1, 7, and 60. Samples were immediately analyzed for concentrations of β-carotene and total protein prior to the serum being frozen. Calves were fed 3.78 L of dam-specific colostrum and colostrum was sampled immediately following parturition. Fresh samples were used for immediate BRIX and β-carotene analysis, as well as for component and colorimeter analysis. Feed samples were collected weekly throughout the trial and nutrient composition of forage and TMR samples was determined. Health records for the animals were collected from DairyComp305. The farm staff was responsible for all care of the animals. Colostrum, serum, and feed samples were analyzed for concentrations of vitamin A, vitamin E, and β-carotene. A full metabolite profile was determined in serum from cows and calves. Proc Mixed, Proc Glimmix, and Proc Freq, among others, in SAS 9.4 were used to analyze the collected data. The rations were adequate for vitamin A, with concentrations in the TMR exceeding NRC requirements by 20% and 276% for close-up and fresh diets, respectively. Vitamin E in the TMR was just under requirements at 92.2% and 93.0% of NRC requirements for close-up and fresh diets, respectively. β-Carotene supplementation significantly increased (P = 0.023) serum concentrations of vitamin A in cows, indicating that the high amounts of supplemented vitamin A in the diet were still not enough to release β-carotene from its provitamin A role. Serum vitamin E concentrations were not affected, indicating that there was no interaction between it and β-carotene. Serum β-carotene concentrations were significantly greater (P < 0.01) for the treatment group on all days when compared with the control group. The concentration of TP was higher (P = 0.045) in β-carotene supplemented cows. β-Carotene supplementation also decreased the concentration of albumin (P = 0.029), increased the concentration of globulin (P <0.01), and affected the ratio between the two (P < 0.01), but these results were confounded by a significant or trending interaction of treatment and parity. No significant effects were detected in reproductive, health, or milk yield variables extracted from DairyComp305. Supplementation of β-carotene increased the concentrations of β-carotene (P < 0.01) and fat (P = 0.042) in colostrum. It also increased the colorimetric values for a* (P = 0.014) and b* (P< 0.01), which indicates that the β-carotene-rich colostrum was significantly more red-yellow in color than the colostrum from control cows. The effects of β-carotene supplementation to the dam were negligible in calves. There were no differences in the concentrations of vitamins A and E in calf serum. Significant effects or trends were observed for concentrations of gamma-glutamyl transferase (P < 0.01), blood urea nitrogen (P = 0.044), β-hydroxybutyrate (P = 0.097), and phosphorus (P = 0.088), but, with the exception of phosphorus, these results were confounded by significant or trending treatment by parity interactions. There was also a significant interaction of treatment by time for gamma-glutamyltransferase (P < 0.01). The majority of calf serum samples had β-carotene below detectable levels. Because of this, Proc Freq was used to determine if there was a treatment difference in the number of calves above or below the detection threshold of 0.05 g/mL. There were 28 samples above the threshold at 24 h of age, with 89.3% (P < 0.01) of the calves with detectable β-carotene concentrations being from β-carotene-supplemented dams. At d 7, there were only 7 calves with detectable concentrations. Of the 7 calves, 85.7% (P = 0.045) were from β-carotene-supplemented dams. Only one sample at d 0 had detectable β-carotene concentration and none did at d 60. This fleeting response shows that supplementing the dam with β-carotene does not substantially affect the calf and direct β-carotene supplementation to the calf should be considered