Economic impact of oxidative stress on the profitability of dairy cows and calves: In the most simplistic terms, the body (humans and animals) could be compared to a medium in which millions of chemical reactions take place with the support of food energy. These reactions are the basis of life without which life will cease to exist. Thus, the body could simply be called the fire of life because oxygen is one of the main substances required by humans and animals to maintain this fire. This fire can neither be allowed to burn out of control nor be extinguished completely. Thus, for a healthy bodily function, an optimum burning of this fire is necessary. Oxidative stress occurs when the generation of reactive metabolites of oxygen (reactive oxygen metabolites/species or free radicals) exceeds their safe detoxification or disposal by the body. In animal production, reactive metabolites of oxygen may occur as a result of physical, biological, and chemical stressors which could result in morbidity, mortality or reduced production. In dairy cows, some important health disorders (retained fetal membranes, udder edema, mastitis) appear to be related to oxidative stress. Also, milk quality and shelf-life could be affected by antioxidants such as vitamins C and E. Pre- and post-weaning periods could be very stressful for dairy calves, thus lowering their immune function and resulting in infection by deadly pathogens.
What are antioxidants?
In the process of the use of oxygen to support life, free radicals or reactive oxygen metabolites (ROM) are formed. Free radicals include singlet oxygen, superoxide, hydrogen peroxide, hydroxyl radical and fatty acid radicals. Free radicals can react with enzymes, cell membranes and DNA damaging them or even causing cell death (process of ageing). Cellular defenses to control or neutralize the harmful effects of free radicals in the body are through 1) Enzymatic neutralizing defenses (Zn/Cu/Mn superoxide dismutase, Fe-catalase, Se-glutathione peroxidase and Se-glutathioneS-transferase), 2) Enzymatic damage repair defenses (lipases, proteases and DNA/RNA repair enzymes), 3) Non-enzymatic defenses (glutathione, uric acid, melatonin, hypotaurine) and 4) Nutrient defenses (carotenoids, ascorbate, tocopherols, tocotrienols, phenols, lycopenes, trace minerals, etc.).
Measurement of oxidative stress in animals:
Research ndicates that when recently weaned calves were purchased at auction barn and transported long distances (e.g. from Tennessee to Texas), the byproducts of lipid peroxidation called malondialdehydes (MDA) increased in the blood (Figure 1) and at the same time their ability to detoxify free radicals as measured by blood total antioxidant capacity (TACA) plummeted (Figure 2). TACA is the total capacity of plasma or tissue to detoxify oxygen radicals. Thus, these calves were predisposed to tissue damage (lung lesions, etc.).
When blood vitamins A and E were measured along with the incidence of bovine respiratory disease (BRD), as their blood antioxidant vitamin concentrations decreased, the incidence of BRD increased (Figures 3 and 4). Ultimately, as the incidence of BRD increased, their performance as measured by average daily gain (ADG) decreased (Figure 5). The lower the vitamin concentration, the more chronically sick they became.
In another study with calves where blood vitamin C (ascorbic acid) was measured before and after shipment from Arkansas to Texas, calves’ average blood vitamin C concentrations decreased from TN values of 2.67 micro Moles/ liter (uM/L) to 0.16 uM/L (TX), with some calves below detectable levels. This result was very surprising because cattle can synthesize vitamin C.
Thus, marketing and transit stress were either too intense resulting in the depletion of the supply of ascorbic acid or the rumen was not well developed to support vitamin C synthesis. Consequently, calves of this size (dairy and beef) should be supplemented with ruminally protected vitamin C to meet their daily requirements and/or to counter physical, biological and chemical stressors in the production system.
The relationship of blood antioxidants to the immune system was reported in dairy calves raised in commercial calf hutches and indoor metal pens. There was a positive correlation between plasma ascorbate and IgG concentrations in calves housed in metal pens but the relationship was negative for those housed in hutches. Additionally, housing in metal pens decreased plasma cortisol, plasma ascorbate, IgG and specific antibody titers when compared with those housed in commercial hutches.
Calves with respiratory and enteric infections showed decreased plasma concentrations of ascorbic acid. Because calves are not capable of synthesizing endogenous ascorbic acid until 21 days of age, it is inevitable that they should receive ascorbic acid in their diet during this period. Also, the housing type and season of the year (stressors) could prolong the age at which ascorbic acid is synthesized in calves.
Antioxidants and Dairy Health Disorders
- Clinical mastitis is an expensive disease for the dairy farmer. The total case of management of the disease average $100 to $140 per case.
- Severity of mastitis increases with a decreased antioxidant capacity.
- Supplemental vitamin E and Se have been beneficial in reducing prevalence and severity of mastitis and somatic cell counts.
- Concentration of ascorbic acid is very high in some immune cells and increase as much as 30 fold when stimulated.
- About 9% of all calvings result in retained fetal membranes (RFM) resulting in $100 to $280/case.
- Ascorbic acid concentrations are 50% lower in maternal and fetal placental tissues than cows without RFM.
- At least 300 IU of vitamin E/day is recommended when oxidized flavor in milk is a problem. About 2% of dietary vitamin E is secreted in milk.
Impact of commingling on oxidative stress and BRD:
Dairy calves being raised as replacement heifers or for veal are commonly purchased from several sources. Also, dairy cows are often housed in large groups in a single pen after weaning. Thus, translocation and pathogen distribution through commingling are common practices which could affect the health of cows and calves. Research supporting the effects of commingling stress on BRD was conducted at the Texas A&M University Research Center in Amarillo using calves obtained from two sources (New Mexico and Tennessee) measuring red blood cell (RBC) lysate concentrations of cellular glutathione peroxidase (cGPx), reduced (GSH) and oxidized (GSSG) glutathione and Zn/Cu/Mn superoxide dismutase (SOD). These biomarkers used to assess the incidence of bovine BRD during the receiving period.
Pretransit HB (mg/dL), cGPx (mU) and GSSG (nmol) were lower (P<0.05) in TN steers than NM steers. Thus, distance of translocation was significant in the antioxidant capacity of these calves (Figures 6 and 7). Pretransit cGPx values for TN and commingled calves correlated negatively with incidence of BRD at the feedyard (Figures 8 and 9). As incidence of BRD increased, cGPx concentrations decreased. Also, the lower the blood cGPx and GSSG concentrations of calves, the higher the incidence of BRD (Figures 9 and 10). Thus, with the depletion of the cellular pools of antioxidants, the greater the impact of stressors on the health of the animal.
When dietary antioxidants such as serum free retinol (vitamin A), α- & y-tocopherols (vitamin E) were measured in the blood of these calves, they decreased precipitously from the farm and through the first 28 days at the feedyard. Thus, with the onset of stress, ruminants become morbid and ultimately lose dietary antioxidants due to a reduction in intake and/ or a reduction in their synthesis in the rumen. In the case of calves, antioxidants depletion in the face of stress is even worse because the rumen is not fully developed to support the biosynthesis of ascorbic acid.
In order to compensate for the stress and/ or disease and the reduced or debilitated antioxidant status, dietary supplementation with antioxidants becomes inevitable to sustain life.
In one study, dairy calves fed 0.5 g or 1 g of microencapsulated ascorbic acid pre-weaning gained 15.4% more weight daily when compared with the control calves which did not received supplementary ascorbic acid. The average daily weight gains were also 8.4% higher than the controls with the continued post-weaning ascorbic acid supplementation. The results suggest that microencapsulated ascorbic acid is essential for calves whose antioxidant defense systems are less well developed.
Dietary sources of antioxidants:
As outlined above, oxidative stress is very common in modern livestock production systems. The economic impact in beef cattle production alone is estimated at billions of dollars due to its relationship to BRD. In other production systems such as dairy, swine and poultry, there are similar economic effects, ultimately affecting the profitability of the overall livestock industry. Who would ever believe that feeder calves originating from lush green native pastures of calf producing areas (TN, KY, AR and NM) would be deficient in serum free retinol resulting from auction barn sale and transit stress?
Who would ever believe that cattle unlike humans that can synthesize ascorbic acid would not have detectable levels of this key antioxidant in their blood?
Oxidative Stress and the transition Dairy Cow:
Classically, the transition period (defined as late pregnancy to early lactation) spans 21 days prepartum to 21 days postpartum. However, this period could be greater because of biological, chemical and environmental stressors preponderant at the dairy farm. A reduction in nutrient intake in the phase of dramatic increase in nutrient requirements is a common characteristic of this period. Thus, the risk of metabolic disorders increases with decreasing profits. Other losses associated with antibiotic treatment and delayed breeding may occur. However, by far the most economically important metabolic disorders that drain profits are ketosis, milk fever, displaced abomasums, retained placentas (or fetal membranes), mastitis, metritis and dystocia, all occurring during this critical period of the lactation cycle. Some of these disorders occur because of a depression in the immune system. Plasma alpha tocopherol (vitamin E) concentrations have been reported to be depressed by as much as 47% at calving. When high levels (1,000 IU per head daily) of vitamin E were fed for 21 days prior to calving, reduced retained placentas was observed. In the phase of decreasing circulating levels of progesterone and glucocorticoids, dietary vitamin E seems to enhance the immune system. Thus, oxidative stress during the transition period could be the transition dairy cow. To remediate against these problems, a balanced antioxidant nutrition is recommended during this period.
Two major antioxidant vitamins manufactured by Maxx Performance (Roanoke, VA) are available to replenish the antioxidant status of ruminants. Microencapsulated Vitamin C is a stabilized vitamin C that when used as a supplement in animal feed is temperature and low pH resistant and will escape ruminal microbial degradation and become biologically available to all ruminants and nonruminants.
By microencapsulation, ascorbate is also physically protected from air, light and metals, thus maintaining its potency (raw supplements are exposed to destruction before they’re needed). Microencapsulated Vitamin C is the most potent form of ascorbic acid which is a powerful reducing agent (electron donor) and participates in intracellular and extracellular quenching of reactive oxidants, recycling of vitamin E (electron transfer to oxidized tocopherols and tocotrienols), participates (co-factor) in 8 major and essential enzymatic reactions, prevention of LDL oxidation, and promotes iron absorption in the gastrointestinal tract. Microencapsulated Vitamin C is free flowing and contains 70% ascorbic acid and can be manufactured in various particle size ranges for compounding with different feeds. Packaging is in 50-pound, poly-lined recyclable cartons that can be stacked in a pallet (4 layers of 10 cartons) for shipping.
Coated Vitamin E is also a microencapsulated vitamin E (a-tocopherol acetate) that when used as a supplement in animal feed is temperature and pH resistant and will escape ruminal microbial degradation and become biologically available to all ruminants and nonruminants. The major antioxidant function of vitamin E (tocopherols and tocotrienols) is to prevent lipid peroxidation. In the cell membrane, it’s been estimated that there is 1 tocopherol molecule for every 1000 lipid molecules. With its phytyl tail buried in the membrane and its chroman ring on the surface, the tocopherol molecule acts as an antioxidant and is regenerated from its oxidized form by interacting with other antioxidants, particularly vitamin C; thus, the two vitamins synergizing to produce maximum biological response during stress. In recognition of this synergy, Maxx Performance has an expansive microencapsulation technology platform for producing Vitamin C and Vitamin E together in a compact single spherical combination particle for ease of handling.
In extreme stressful situation, a very rapid detoxification is needed to restore health and maintain production. Microencapsulated Vitamin CE combination comes in 50-pound, poly-lined recyclable cartons that can be stacked in a pallet (4 layers of 10 cartons) for shipping.
Microencapsulated coated Lysineis a ruminally protected form of the essential amino acid lysine. Cattle do require essential amino acids just like nonruminants, especially if deficiency is created by the stress of production and/or the rumen is not well developed to provide microbial sources of lysine. With the shift away from using animal protein sources in animal production, nutritionists are looking for cost effective sources of essential amino acids, especially lysine to meet animal requirements. Microencapsulated Lysine by Maxx Performance is a stabilized free flowing lysine and provides the most effective way to supplement ruminants directly without the interference of ruminal microbes. Lysine is required for protein synthesis without which the performance (ADG, milk, eggs, reproduction) of livestock is reduced. Maxx Performance rumen protected Lysine comes in 50-pound, poly-lined recyclable cartons that can be stacked in a pallet (4 layers of 10 cartons) for shipping.