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PRO. ACCESS |
Health Indicators
Early warning systems
Our health indicators are at once individual and collective, of diagnostic and predictive interest. They allow us to confirm the pathology of a recumbent cow but also to predict the risk of calf mortality or left/ right displaced abomasum in a dairy cow herd. You will find in this section all the parameters which allow us to lead the investigation in a herd.Acid-base balance
The evaluation of acid-base balance of cattle is based on several measures and tests to be performed on urine. These parameters are:
- The measurement of pH (to realize at the farm with specific pH strips)
- The determination of bicarbonate: tCO2
This assay provides a first idea of the acid-base status of the animal. When the animal affected with metabolic acidosis, the excretion of bicarbonate is reduced, but it will be increased during metabolic alkalosis.
A strong correlation between the bicarbonate and urinary pH is expected and the absence of this correlation is a first element of suspicion of metabolic imbalance.
- Assay of strong ions: K, Na, Cl
These assays can be used to assess intakes of each element, which presents a double interest:
1. To detect deficiencies in the supply of K, Na and Cl: in fact, these deficits can have a very strong impact on animal health and production
2. To indirectly evaluate the DCAD (Dietary Cation-Anion Difference) of the ration, this helps to explain most anomalies of the acid-base balance
- The assay of major macro-nutrients: Ca, P, Mg
These assays have different interests:
1. Ca - P: This assay helps to detect the physiological consequences of a disturbed acid-base status and to identify the origin of a possible metabolic acidosis. Indeed, during metabolic inorganic acidosis (eg contribution of anionic salts, diet with very low DCAD, ...), the excretion of calcium is highly increased. On the contrary, during metabolic acidosis of organic origin (eg ruminal acidosis), the excretion of phosphorus increases.
IMPORTANT: This assay is not a correlated to the input of the diet
2. Mg: This assay is to evaluate the contribution of Mg in the diet and the availability of Mg. Indeed, the absorption of Mg is negatively correlated to the potassium content of the diet.
- The SID (Strong Ion Difference)
It is calculated using the following equation: SID = Na + K - Cl
The SID allows to assess the amount of non-titratable acids (NH4 +, lactic acid, ...) excreted in urine.
T4 and thyroids hormons
Thyroid hormons are present in the blood of the calf at birth and are relatively well correlated to the maternal status. The transfer takes place actively and essentially via placenta compared to colostrum which is residual concerning T4-supply.
The transfer of passive immunity and the poor survival due to a lack of temperature regulation at birth are expressions of a lack of thyroid hormone and iodine which can also be associated to a poor selenium status.
Indeed, the presence of triiodothyronin (T3) is required to stimulate the production of surfactant by the newborn lung. Reduced production of surfactant was observed in sheep which underwent ablation of thyroid before birth.
Studies show the importance of thyroid hormones in the management of survival at birth. In calves or lambs born prematurely or in calves from mothers deficient in iodine and selenium, the deficiency of cortisol contributes to inadequate conversion of T4 into T3, which may be responsible, via the peripheral adipose tissue, for failure of thermoregulation, for the acute Respiratory Distress Syndrom (RDS), for stillbirth, for behavior disorders, for the failure of the acquisition of colostral antibodies but also to illness in the days following birth.
Iodine
Essential trace elementIodine deficiency has been known worldwide for many years (Chappuis 1991). It is one of the most important deficiencies in its frequency and global occurence (McDowell).
Iodine is essential for the synthesis of thyroid hormones, whose role is to maintain the energy metabolism. The main deficiency symptoms are found mostly in young animals that have a lack of vitality, difficulty to suckle and are very susceptible to microbial or parasitic infections (Chappuis). The Respiratory Distress Syndrome is also due to the deficiency of iodine. In adults we have shown a relationship between fungal abortions and iodine deficiency.
Needs vary between 0.1 and 2 mg per kg DM in the presence of antagonists (Chappuis), but it is recommended not to exceed 0.5 mg per kg DM for maintenance (NRC 2001).
All French forages are deficient in Iodine.
Zinc
Essential trace element
The Zinc is, after the Iron, the trace element the most abundant in the body. It is necessary for the activity of more than 200 enzymes!
Zinc deficiencies are responsible for cutaneous disorders and for abnormality of hoofs. It is well known that the Zinc deficiency creates an underdevelopement of testicles in the bull and the ram. Zinc deficiency is also directly involved in the immune suppression, it is also reported that Zinc is indispensable to the action of Vitamin A, its hepatic mobilization being possible only in the presence of this trace element. This explains secondary deficiencies in Vitamin A due to Zinc deficiencies.
Finally, the Zinc is essential for the function of insulin, carbonic anhydrase and growth hormone. Deficiency causes a strong disruption of taste: hypogueusia and even its total disappearance: ageusia.
The needs of animals are estimated at 50 mg of kg DM. All forages are deficient in Zinc.
Selenium
Essential trace element
Indispensable constituent of Glutathion peroxydase, it has thus a fundamental function of antioxidant. It so prevents the degeneration of tissues and vital functions. It also participates in the synthesis of thyroid hormones.
Its deficiency in the new born calf is related to the weak calf syndrome (incapability of suckling and getting up easily and to the Respiratory Distress Syndrome. In adults a deficiency is involved in prolapsus, abortions and retained placenta.
Needs in Selenium range from 0.1 to 0.3 mg of kg DM.
95 % of French forages are deficient in this major element of the metabolism.
Copper
Essential trace element.
The Copper is at once indispensable and toxic in rather close ranges. The clinical signs of deficiencies can be confused with other diseases which explains that often the deficiencies are not looked for or diagnosed.
Only Zinc activates more enzymes than Copper. The most important copper-dependent enzyme activities are the following: the assimilation of the Iron, the deficient animals are thus weakened, a strong anti-oxididantive activity by the activation of Superoxide dismutase and the growth of bones and muscles (the heart in particular). It was demonstrated that the immune system would not be effective without Copper. Needs are 10 mg of kg DM for cattle and 5 mg of kg DM for sheep.
The toxicity at these last ones is chronic: they have to ingest more than 15 mg of kg DM per day during several weeks.
Some forages can present a copper concentration superior to 10 mg / kg DM thus it is advisable to always check the status of animals before any copper complementation.
Cobalt
Cobalt deficiency exists only in ruminants, on the one hand because the vitamin B12 in these species is produced by the rumen microflora, plants do not produce it, on the other hand because the Vitamin B12 requirement is higher in ruminants.It is unnecessary to orraly complement a ruminant on Vit B12 ; Cobalt alone is sufficient.
The action of Cobalt is mainly by the activation of two distinct forms of Vitamin B12: the MethylCobalamin and AdenosylCobalamin. The first allows the synthesis of carbon chains, the "bricks" of the large molecules of the body (including methionine, choline ..), the second is essential to energy metabolism (citric acid cycle including).
Cobalt deficiency is manifested by anorexia, anemia, hepatic steatosis, increased mortality of newborn associated with a marked weakness in the young calf after birth.
Deficient animals have growth delay and delayed developement of the ruminal flora.
The assay of blood Vitamin B12 is a good indicator of Cobalt supply, but it also indicates the integrity of the ruminal flora. A low Vitamin B12 level, in particular in dairy cows, is often associated with ruminal acidosis.
Cobalt needs are 0.1 to 0.7 mg of kg DM .
With the notable exception of alfalfa, French forages are deficient in Cobalt.
Vitamin A
Vitamin A or retinol, is the biologically active molecule, it only exists in animals and foods of animal origin.The plants do not contain retinol but pigments called carotenoids, many of which are likely to be transformed into retinol. They are called provitamin A, the best known is beta-carotene which is very abundant in green plants.
The hypervitaminosis is very dangerous for pregnant females, because of its teratogenicity. Any overdose should be avoided. It could result from the combination of simultaneous administration of several sources of vitamins.
Vitamin A is involved in the synthesis of Rhodopsin, which is needed for vision in twilight. This feature explains the emergence of "night blindness" observed in some subjects deficient.
This liposoluble vitamin is also involved in the growth and development, including in the foetus. Vitamin A deficiency induces disturbances of development of cartilage and bone. Vitamin A is involved in maintenace of skeletal and epithelial tissue (digestive, dermal, renal, ...).
Vitamin A is also involved in the metabolism of steroid hormones and spermatogenesis, which explains the importance of vitamin A status in reproductive performance. In case of moderate deficiency, one can observe abortions, retained placenta, metritis, delayed uterine involutions and problems of implantation. In case of severe deficiency, there is ovarian dysfunction with irregular cycles and anoestrus, follicular atresia and formation of cysts.
Vitamin A has an antioxidant function when oxygen radicals are not too important. In the case of intense oxidative stress, Vitamin E takes over.
Vitamin A is stored in the liver, there is an average stock of at least 4 months. So it is in late winter that the animal is the most sensible to deficiencies as well as in case of zinc deficiency whose action is essential to the mobilization of the stock of vitamin A.
The needs are 4 000 IU / kg of DM
Vitamin E
The vitamin of the group E, liposoluble vitamins, are very effective biological antioxidants that prevent damage to cell membranes caused by the accumulation of peroxides. This role is shared by other biological antioxidants, Selenium in the first place (via Glutathion Peroxidase), Vitamin C, β-carotene and Copper (via Superoxide Dismutase).Vitamin E deficiencies are rarely due to lack in diet. They are almost always conditioned by factors that will either destroy vitamin E in the diet or prevent its digestive use, or play the role of antagonistic factors at the cellular level. Thus the main antagonists of vitamin E are fat peroxides in the diet. The secondary factors are the excess of vitamin A, the presence of mycotoxins (zearalenone), injections of iron dextran, the deficit in sulfur amino acids and copper excess.
Almost all myopathies have their origin in selenium deficiency.
However, even in the absence of any clinical signs of deficiency, a supplement of vitamin E enhances the immune system and may help reduce the incidence of some infectious attacks.
It explains the improving effect of vitamin E on immunity and the protective effect it exerts on the immune cells whose membranes are highly rich in polyunsaturated fatty acids and thus particularly susceptible to the destructive action of free radicals.
NEFA : Non Esterified Fatty Acids
In the adipose tissue, there is a balance between lipolysis and lipogenesis. When this balance shifts to lipolysis, ie the conversion of the triglyceride to glycerol + NEFA, the concentration of NEFA in the blood increases. The origin of this shift of balance can be an energy deficiency or an increased sensitivity of adipose tissue to lipolysis, most often in cows too fat.
The concentration of NEFA in the blood is a marker of the intensity of lipomobilisation. It allows us to approach the energy deficit.
We analyze the NEFA
- The last 15 days before calving as an indicator of ketosis and of the risk of displaced abomasum to come in early lactation.
- In early lactation to quantify the weight loss of animals and assess the importance of energy deficit.
BHB Beta-Hydroxybutyrate
The BHB is a ketone.It can be formed in the rumen epithelium and in the omasum in case of excess of butyric acid (ruminal production, forage origin such as sugar beet and sugar), but this way of production is not the main one.
The main origin of BHB is the hydrogenation of a molecule of acetoacetate, formed in the mitochondria of hepatocytes during neoglucogenesis.
Two conditions are necessary for a BHB increase : a primary increase of NEFA, and a penetration of those NEFA in the mitochondria. This penetration of NEFA in the mitochondria occurs during glucose deficiency in ordrer to produce energy.
The BHB is a marker of sub-clinical ketosis
Urinary and milk ketone bodies known high individual variability: at the same rate of blood ketone, excretions between cows are very different.The blood BHB is the best marker of sub-clinical ketosis.
It is a very useful indicator in monitoring reproduction eg to assess the dietary risk of infertility.
Haptoglobin : inflammatory marker
It is a molecule "suicide" which eliminates itself while allowing to reabsorb the iron contained in the hemoglobin and by protecting the body of the oxidizing activity of this last one.
Thanks to this function it increases very quickly when the body has to face an aggression: it is what we call a positive acute-phase protein of the inflammation. It can multiply its level by 1 000 during inflammation or during infection. It is a very premature marker because it increases some hours after the beginning of the inflammatory phase and returns to its normal level (< 100 mg / L) within 3 days.
It does not allow to make the difference between a mastitis or a lameness, but it allows to make the difference between an infectious pathology or a simple deficiency.