Effects of supplemental parenteral administration of vitamin E and selenium to Jerseys and Holsteins during the nonlactating period

A survey of Canadian dairy nutritionists to assess current trace element formulation practices

The purpose of this study was to identify current practices and perceptions around trace element feeding for dairy cows through a Canadian dairy nutritionist survey. An online survey with 23 questions was used to collect data from Canadian dairy nutritionists with the help of professional associations and social media. The survey was active from November 2021 to April 2022. The first 7 questions collected descriptive information on respondents, and the subsequent 16 questions focused on trace element feeding. A total of 92 participants from all over Canada filled out the survey, and about 26% of Canadian herds and cows were represented by these respondents. The participants had diverse views on the importance of diet formulations for trace elements to optimize cow health and productivity, with perceptions varying from very important to not important. In comparison, macronutrients and selenium were consistently rated as very important by between 58% and 74% of respondents. Software reference values were used by 54%, 72%, and 73% of participants to estimate trace element concentrations of forages, cereals, and protein sources, respectively, highlighting the importance of regularly updating the feed library of the software. More than 60% of nutritionists participating in this study had intentionally formulated diets above trace element software recommendations, considered mineral interactions occurring in the rumen, and used a trace element source known for its better bioavailability (e.g., organic, chelate) when they formulated diets. Herds with more than 80 cows were more likely to be given trace element supplements known for their greater bioavailability. The most used supplement with enhanced bioavailability was selenium. In addition, different trace element feeding strategies pertaining to different stages of lactation and breeds were reported. This finding can be explained by the absence of clear recommendations on trace element feeding by breed. The participants who adjusted trace element feeding according to the stages of lactation considered the transition period as the most challenging period, and they identified the need for a source of trace element known for its greater bioavailability for this period. Further research should aim to identify environmental risk of trace element overfeeding using the One Health approach. Moreover, strategies to avoid trace element overfeeding should be evaluated.

The effect of parenteral supplementation of vitamin E with selenium on the health and productivity of dairy cattle in the UK

Recent work has suggested that the recommended intakes of vitamin E for dairy cattle need to be increased, particularly in dry cows. However, these suggestions are based on data from cattle in the USA, which may have significantly different oxidative stresses than European cattle. This study, which involved 594 cattle on three dairy farms, was designed to determine the effect of increased vitamin E supplementation on the health and fertility of UK dairy cows. Cattle were randomly allocated to receive either two intramuscular injections of 2100 mg of vitamin E (and 7 g of sodium selenite) 2 weeks before calving and on the day of calving, or no additional vitamin E supplementation. Although supplementation had no effect on milk yield, reproductive efficiency, or incidence of uterine infections, supplemented cattle had a lower risk of culling and a lower rate of mastitis. These figures were economically significant but not statistically significant at the 10% level. Supplementation reduced the incidence of retained fetal membranes from 6.5% to 3%, an effect which was almost significant at the 5% level. If these data are representative they suggest that vitamin E recommendations for UK cattle should be reassessed.

Manipulation of antioxidant status fails to improve fertility of lactating cows or survival of heat-shocked embryos

Experiments were conducted to test whether enhancement of antioxidant status could improve fertility and milk yield in dairy cows and resistance of cultured embryos to heat shock. Three experiments in three herds were performed to evaluate the effect of multiple intramuscular injections of 500 mg of vitamin E and 50 mg of selenium at 8 to 21 d before expected calving and at 30 and 80 d postpartum on reproduction of lactating Holstein cows. Vitamin E and selenium injections did not improve reproductive function or milk yield in any of the studies. The predicted 305-d milk yield (averages of least-squares means across treatments) were: 9478, 7073, and 10,204 kg projected 305-d milk for experiments 1, 2, and 3, respectively. Percentages of cows pregnant at first service were 30, 16, and 24% in experiments 1, 2, and 3, respectively. Three studies were performed to test whether vitamin E improved development of cultured bovine embryos exposed to heat shock. Heat shock of 41 degrees C at the two-cell stage reduced development to the blastocyst stage, but culture with 100 microM vitamin E did not reduce effects of heat shock on impaired development. For example, 9 h at 41 degrees C reduced blastocyst development from 51.2 +/- 3.3% to 3.4 +/- 3.3% in the absence of vitamin E and from 54.0 +/- 3.3% to 5.2 +/- 3.3% in the presence of vitamin E. Development of morulae to the blastocyst stage was not compromised by culture at 41 degrees C for 9 h. Additionally, there was no overall effect of vitamin E on morula development. In conclusion, multiple injections of vitamin E and selenium at the administered levels did not improve postpartum fertility nor milk yield of lactating Holstein cows in three different herds, and there was no direct thermoprotective effect of vitamin E for cultured, heat-shocked embryos.