Key Findings
Limited knowledge exists about the effects of organic Se additives—OH-SeMet (HMSeBA) and SY—on dairy cow production. This study compared the effects of the supplementation on performance, biochemical parameters, and selenium bioavailability in mid-lactation dairy cows.
Organic Se forms can increase milk and plasma Se concentrations. The high transfer of Se from OHSeMet to milk could reflect transfer to other tissue. Overall, OH-SeMet showed to be more efficient than SY in improving Se concentrations.
About the Co-Author
Nancy Whitehouse, Research Assistant Professor of Agriculture, Nutrition, and Food Systems
Contact information:
Nancy.Whitehouse@unh.edu, 603-862-1349
This research was published in the INSPIRED: A Publication of the New Hampshire Agricultural Experiment Station (Winter 2021)
Researchers: N. Whitehouse and J. Sexton
Selenium (Se) is an essential trace mineral that, if deficient in soil, will be deficient in diets fed to dairy cows. Adequate Se is important for animal health to support immune functions and efficiently fight oxidative stress and pathogens. Standard farm practice is to supplement Se in the diet either in mineral form (sodium selenite) or organic forms. This study compared the bio-efficacy of two organic Se sources (Hydrox-selenomethionine and seleno-yeasts) in mid-lactating dairy cows based on the Se transfer into plasma and milk.
Organic forms of Se include seleno-yeasts (SY) or pure forms such as selenomethionine or hydroxy-selenomethionine (HMSeBA). In monogastric organic Se forms, pure forms (like SeMet or HMSeBA) are described to have an additional bio-efficacy compared to seleno-yeasts attributed to the presence of only about 60% of Se as SeMet in those yeasts, the rest being other organic Se forms (Briens et al., 2014; Zhao et al., 2017).
HMSeBA has been widely shown to improve the relative bioavailability of Se compared with inorganic forms or SY in broiler chickens (Briens et al., 2013, 2014). Sun et al. (2017) and Li et al. (2019) demonstrated that the HMSeBA improves Se bioavailability in milk and plasma and enhances the activities of antioxidant enzymes in dairy cows. Still, limited research has been conducted regarding the effects of the HMSeBA on dairy cow production. Therefore, we compared the effect of the HMSeBA and the SY supplementation on performance, biochemical parameters and selenium bioavailability in mid-lactation dairy cows.
All procedures related to animal care were conducted with the approval of the University of New Hampshire Institutional Animal Care and Use Committee. Cows were housed at the Fairchild Dairy Teaching and Research Center in a naturally ventilated tie-stall barn, fed individually, and had continuous access to water. Twenty-four lactating Holstein cows, 12 multiparous and 12 primiparous were used in a 91 day experiment.
The four treatments were: 1) basal diet as a total mix ration (TMR) with an expected Se background of 0.2 mg/kg TMR as-fed (control), 2) basal diet + 0.3 mg Se/kg TMR as-fed from Seleno-Yeast (SY), (SY-0.3), 3) and 4) basal diet + 0.1 or 0.3 mg Se/kg TMR as-fed from Hydroxyselenomethionine (OH-SeMet), (OH-SeMet-0.1 or OH-SeMet-0.3). The basal diet was formulated to meet the requirement (NRC 2001) of the dairy cow and was fed as a TMR.
Cows were milked twice daily and milk weights were recorded. Milk and blood samples were obtained from each cow during the morning and afternoon on the last 3 days of weeks 1, 2, 3, 4, 6, 8, 10 and 12 of the study. Samples were analyzed for fat, true protein, lactose, milk urea nitrogen (MUN), somatic cells and total Se.
Table 1 shows that dry matter intake overall was not affected by treatment. Milk yield, fat corrected milk and energy corrected milk were significantly higher in the Se treatments versus the control. There was a trend for decreased fat percentage when the Se treatments were fed. There was no effect of Se concentration or source on milk urea nitrogen or lactose percentage. Milk protein percentage in this trial was significantly decreased for SY-0.3 compared to OH-SeMet-0.3 but was not different from the control or OH-SeMet-0.1. T. Milk somatic cell counts (SCC) and linear somatic cell score (LSCS) were significantly lower in the OH-SeMet 0.3 group. The supplementation of Se in diet from SY or OH-SeMet, with both levels of OH-SeMet, significantly increased the average plasma and milk Se concentration, with OH-SeMet-0.3 being the highest followed by SY-0.3 and then OH-SeMet-0.1. In comparison to the control group, SY-0.3, OH-SeMet-0.1, OHSeMet-0.3 increased Se bioavailability in milk by 171, 136 and 205% respectively.
For plasma Se concentration, the OH-SeMet-0.3 and SY-0.3 significantly increased Se level in plasma after the second week of the study and until the end of the study. Furthermore, OH-SeMet-0.3 induced significantly higher plasma Se concentrations by 7–9% compared to SY-0.3 from week four until week twelve. The control group constantly declined but supplementation with 0.1 of the OH-SeMet maintained the plasma Se at high level but is not sufficient to completely reach the level obtained by the supplementation of 0.3ppm. Selenium was greatest for OH-SeMet-0.3 and lowest for control with the SY-0.3 and OH-SeMet-0.1 being in between. Selenium bioavailability was greatest for the OH-SeMet-0.3 (27.6%), then SY-0.3 (23.4%) and OH-SeMet-0.1 (21.6%).
