The effect of chloride ammonium, vitamin E and Se supplementation throughout the dry period on the prevention of retained fetal membranes, reproductive performance and milk yield of dairy cows

Impacts of heat stress on immune responses and oxidative stress in farm animals and nutritional strategies for amelioration

Heat stress is one of the greatest challenges for the global livestock industries as increased environmental temperature and humidity compromises animal production during summer leading to devastating economic consequences. Over the last 30 years, significant developments have been achieved in cooling and provision of shade and shelter to mitigate heat stress reducing some of the losses associated with heat stress in farm animals. However, the recent increase in the incidence of heat waves which are also becoming more severe and lasting longer, due to climate change, further accentuates the problem of heat stress. Economic losses associated with heat stress are both direct due to loss in production and animal life, and indirect due to poorer quality products as a result of poor animal health and welfare. Animal health is affected due to impaired immune responses and increased reactive oxygen species production and/or deficiency of antioxidants during heat stress leading to an imbalance between oxidant and antioxidants and resultant oxidative stress. Research over the last 20 years has achieved partial success in understanding the intricacies of heat stress impacts on oxidative stress and immune responses and developing interventions to ameliorate impacts of heat stress, improving immune responses and farm animal health. This paper reviews the body of knowledge on heat stress impacts on immune response in farm animals. The impacts of heat stress on both cell-mediated and humoral immune responses have been discussed identifying the shift in immune response from cell-mediated towards humoral response, thereby weakening the immune status of the animal. Both species and breed differences have been identified as influencing how heat stress impacts the immune status of farm animals. In addition, crosstalk signaling between the immune system and oxidative stress has been considered and the role of antioxidants as potential nutritional strategies to mitigate heat stress has been discussed.

A meta-analysis and meta-regression of the effects of vitamin E supplementation on serum enrichment, udder health, milk yield, and reproductive performance of transition cows

Vitamin E is an essential nutrient for cows, but the effect of vitamin E supplementation is often controversially discussed in the published literature. The main goal of this meta-analysis was to evaluate the effects of vitamin E supplementation on its serum and colostrum enrichment, milk yield (MY), and somatic cell counts (SCC), as well as on various reproductive variables of transition cows, by considering a large set of variables that might influence the responses to vitamin E supplementation. After a broad search in journals and databases with keywords related to transition cows supplemented with vitamin E and appropriate filtering of the results, 36 papers including 53 trials were selected, and their data were extracted into a database. A meta-analysis was conducted on the extracted data. The analysis showed enrichment of serum vitamin E both at parturition (effect size: 2.423) and postpartum (effect size: 0.473), but no effects of vitamin E supplementation on IgG concentration in colostrum (effect size: -0.05) were found. There was a tendency for supplemented cows to produce more milk (effect size: 1.29) during the first month of lactation. Because of large heterogeneity, a meta-regression was performed but none of the presumed influencing factors was identified as a potential variable affecting MY. Milk SCC, as an indicator of udder health, was unaffected by vitamin E supplementation. Vitamin E supplementation tended to decrease the calving to first estrus period (CFP), whereby supplementing Se and taking parity into account in the analysis significantly lowered the CFP. Cows receiving additional vitamin E had, on average, 6.1% fewer cases of retained placenta, whereby Se supplementation and breed were key factors improving the effect of vitamin E to reduce retained placenta. In this regard, breeds other than Holstein responded better and these cows showed a lower incidence of retained placenta. The supplemented cows showed fewer days open (effect size: -0.31), and this improvement was affected linearly by increasing the dosage administered. Also, cows showed fewer services per conception with increasing dosage of vitamin E. In conclusion, this analysis showed that supplementing vitamin E did not affect SCC or colostrum quality but improved reproductive performance of transition cows, an effect consistent with increased levels of serum vitamin E and, for some variables, being modulated by Se supplementation.

Effect of reduction of milking frequency and supplementation of vitamin E and selenium above requirements on milk yield and composition in Assaf ewes

The aim of this research was to study the effect of milking frequency and supplementation with a vitamin-mineral complex above requirements on intake, body weight (BW), and milk yield and composition in high-yielding Assaf ewes. Sixteen lactating Assaf ewes were used in this study, separated into 4 groups of 4 ewes each. Animals in 2 of the groups (control groups) did not receive any extra vitamin-mineral supplement, whereas animals in the other 2 groups (supplement groups) received daily an oral dose of 1g of vitamin E (1,000 IU, DL-α-tocopherol acetate) and 0.4 mg of selenium (sodium selenite anhydrous). The experiment consisted of 2 consecutive periods of 3 wk (twice-daily milking in both mammary glands) and 8 wk (once-daily milking in one mammary gland and twice-daily milking in the other gland). Intake, BW, and milk composition were controlled weekly, and milk production was recorded 3 times a week. Administration of the vitamin-mineral supplement had no effect on dry matter intake, BW, or milk production and composition. The reduction of milking from twice to once a day caused a decrease in milk production and lactose concentration and a significant increase in protein concentration, total solids, and somatic cell count, without affecting the fat content. Administration of a vitamin E and Se supplement at the doses used in the present study does not seem to exert, in the short term, a noticeable effect on the mammary gland when milking frequency is reduced.