Glucosuria - causes - Page numbers refer to Sodikoff except where stated otherwise.
Thrall 316, 435, 437
carbohydrate overload
corticosteroid administration
diabetes mellitus Sodikoff: 33, 115, 119, 123, 125, 161, 187,
324, 326, 328. (Thrall 434-435)
embolic nephritis 296
Fanconi’s syndrome 115, 304
feline urologic syndrome 294
lead poisoning 56, 63, 68
nephrotoxicosis 184, 288
nonsteroidal anti-inflammatory drug-induced renal disease 310
renal ischaemia 290
renal tubular defects 44, 115, 306
stress
urinary tract haemorrhage
vit C administration (false positive)
Vit D toxicity 113, 127, 364
Saturday, December 29, 2012
Horses are Smart!
Published in Vetmed March 2012
According to E.B. Hanggi, at the Equine Research Foundation, Aptos, California, USA, horses are smarter than we think! They can manage ordinary daily cognitive tasks and mental challenges quite well.
In nature, food and water sources are of inconsistent quality and variable distribution. Their predators change location and habits. At the same time they must deal with interactions in the herd and need to learn and remember the identities and roles of other individuals in the herd.
Life for a domesticated horse is even more bewildering. In addition to dealing with natural situations, they often live in unsuitable environments, need to suppress instinctual behaviours and learn tasks that are not natural behaviours. They also need to co-exist with humans, who from a horses' viewpoint must be very strange indeed.
Research into the nature of cognition and perception in horses is gradually providing some fascinating insights.
Horses learn through habituation throughout their lives. In a new environment, horses are very reactive and pay attention to any stimulus perceived by any of their senses. However, when certain stimuli are insignificant and are repeated regularly, the response diminishes. Habituation is a simple form of learning, but none the less important, as it allows non-vital information to be filtered out subconsciously, enabling the horse to focus on what is significant.
When a horse is particularly sensitive or fearful, either by its nature or through learned experience, it can be desensitized. Rough handling of its ears, or a bit banging against its teeth may make a horse extremely sensitive to being bridled, for example. This leads to head shyness. Such a horse needs to be retrained by approaching its head in increments and retreating when necessary until the horse willingly accepts normal, gentle bridling.
Horses can become habituated and desensitized to almost overwhelming stressors if it is done correctly. A good trainer exposes horses in a positive manner to all sorts of sights, sounds and contacts, for instance by leaving him unrestrained in a safe corral and having humans behaving strangely around him, playing with bouncing beach balls, multicoloured balloons, umbrellas, plastic tarps, pylons, rattles etc. This makes the horse much more capable of handling novel events calmly. If desensitization is not done correctly, it has the potential to make a horse more fearful and sensitive, for instance by removing an alarming stimulus too soon.
Pavlovian conditioning does not only work for dogs.
A horse also learns effortlessly when initially unimportant stimuli or events are regularly coupled with stimuli that initiate some sort of response. This form of conditioning is used by a trainer when he places a word onto a behaviour. The word "trot" would mean nothing to an untrained horse, but if it is regularly paired with the flick of a whip (associated with invoking a flight response or pain) immediately before the horse changes gait on an upward transition, the horse soon learns to respond to the verbal cue, without the use of a whip.
The use of the word "good", when correct behaviour is carried out, followed by a food treat, informs the horse that a food reinforcer is forthcoming.
To many a veterinarians dismay, horses often learn that the sight of a syringe is associated with pain. The unconditioned horse will then attempt to escape if he has not been trained to accept such handling.
Stabled horses will learn to associate certain sounds with feeding - eg doors opening, hay being poured into a bucket, or will respond to visual cues , such as the arrival of the caretaker. They will then display sometimes unwelcome anticipatory behaviours, such as vocalizing, pawing or kicking stall doors. When reinforced, these may become conditioned behaviours. For instance, when a horse, upon hearing grain being poured, starts kicking his door, a person may feed the horse hurriedly in an attempt to get him to settle down. This positively reinforces the undesirable behaviour and if this scenario repeats itself, the horse has effectively trained the human to feed him quickly.
Operant conditioning, in contrast to classic or Pavlovian conditioning, occurs when an animal manipulates its environment to obtain reinforcement, which can be positive, when he receives something he desires, or negative - such as removing something unpleasant. Both types strengthen the relationship between stimulus and sought after response, so that when the same stimulus is given again, there is an increased chance that the horse will repeat the action.
In the early stages of learning the meaning of a new stimulus, the horse may respond randomly and hit upon the desired response by accident. Reinforcement of the response at the correct moment will cause the animal to repeat the behaviour. Horses excel at this type of learning, especially when positive reinforcement is given.
Unfortunately negative reinforcement is most often used in training. Horses are typically trained to perform actions to avoid something aversive. Under saddle they move forward when leg pressure is applied by the rider, on the ground they yield their hindquarters when pressure is applied to the flank, they back up when pressure is applied to the bridge of their nose, and they enter a trailer to avoid whips, or pressure from ropes. A good trainer refines this by reinforcing the correct and ignoring the incorrect. In this way only the slightest pressure will eventually produce the desired response, making the human/horse partnership appear effortless.
Research has been done with respect to the use of positive reinforcement principles to facilitate trailer loading of horses. It is not uncommon for a horse to be reluctant to be loaded onto a trailer. It can be very time consuming and hazardous for horse and handler. A horse may resist by rearing, pulling back, pawing, kicking or even falling over. If the owner gives up and fails to load the horse, such behaviour is reinforced. Traditional loading methods are based on negative reinforcement, often with some punishment for an uncooperative horse as well. Researchers Ferguson and Rosales-Rui found that , with positive reinforcement and target training, horses learned to load willingly and improper behaviours ceased. These effects also generalized to other novel situations. Horses that have learned to load through positive reinforcement do so eagerly, sometimes requiring only a verbal or visual signal, even when unrestrained. Positive reinforcement can also be targeted at lifting feet for hoof care, groundwork, grooming and veterinary handling.
Discrimination learning in horses has been researched since the 1930's. In discrimination tasks, horses must learn that one stimulus, and not another will result in positive reinforcement. That stimulus then begins to control behaviour, so that the horse acts in a specific manner in the presence of one stimulus, but not the other. In one study a specific horse learnt 20 pairs of discriminations. This horse also "learnt to learn" by using a general pattern to more easily solve subsequent tests. After 6 months he had also retained 77.5% of the discriminations. The "learning to learn" phenomenon has been noted in many other studies. It is a worthwhile tool in training. Often horses are restricted to performing only within a particular discipline. Racehorses don't jump; and dressage horses rarely set foot on a trail. These limitations prevent horses from learning about a variety of stimuli and such animals are less able to deal with novel situations. The more positive stimulation a horse experiences, the more readily it learns in new situations. It is also better adjusted in a variety of conditions and environments.
Spatial cues seem to be more readily discriminated by horses than any other stimuli. This is supported by observations made by vigilant horse owners of how well horses find their way around in areas they have only visited infrequently. Horses also react noticeably when objects in their environment are moved. This demonstrates an awareness of spatial surroundings.
The ease with which horses discriminate visual stimuli makes it easier for researchers to study cognition; and also to measure perceptual abilities and therefore equine vision. It has been experimentally demonstrated that a horse's visual acuity is 20/30 on the Snellen scale. (Human 20/20, dogs 20/50).
Experiments regarding colour vision in horses showed that they could discriminate red and blue from gray. Others showed that they could also discriminate between green and yellow. Recent research by Hanggi and Waggoner showed that horses responded to colour in the same manner as some red/green colour blind humans.
A myth that surfaces repeatedly is that horses cannot recognize what they have seen with one eye with the other eye. Anatomical dissections have proven that the horse's two cerebral hemispheres do indeed have a functional pathway to convey information, and a behavioural study proved that they do have inter ocular transfer. This study used multiple two choice discrimination tests with one eye blindfolded. Once the discrimination was learned, the blindfold was placed over the other eye. Horses immediately responded to the same stimulus, clearly demonstrating interocular transfer.
Horses often startle at an object they have seen before when approaching it from a different angle. This can be explained by the fact that the shape of the object appears differently when seen from another perspective. Experiments with different objects demonstrated that recognition of rotated objects was good under some but not all conditions.
With generalization a behaviour previously conditioned to one stimulus, transfers to other similar stimuli. Riding school horses regularly utilize this form of learning when making sense of a large assortment of inexact hand, leg and seat cues from riders of varying skill levels. Dressage horses, in contrast, learn to discriminate highly precise cues from their riders. As a result they go through mechanical motions that rarely enhance cognitive skills. A horse's generalization abilities can be enhanced by incorporating variety into their programs. As social animals, horses are most comfortable in the company of their own kind. Social interactions can facilitate the learning of new behaviour by observing other horses
The cognitive abilities of horses need to be understood to ensure good husbandry and treatment.
It is as harmful to confine a thinking animal to a dark, dusty stable with little or no social interaction as it is to provide inadequate feed or use abusive training methods. It is certainly in the best interests of both horses and handlers to better understand the scope of equine thinking, and enrich horses' environment. In the not too distant past little consideration was given to why horses behaved like they did. This limited the provision of adequate care and welfare. More recently research into equine cognition and perception has made noteworthy advances. This has led to a greater interest in training methodology and management. Even so, we are still a long way from fully understanding what it is to be a horse. More studies are needed to fully understand this remarkable animal and provide it with the best environment and training for its and our needs.
According to E.B. Hanggi, at the Equine Research Foundation, Aptos, California, USA, horses are smarter than we think! They can manage ordinary daily cognitive tasks and mental challenges quite well.
In nature, food and water sources are of inconsistent quality and variable distribution. Their predators change location and habits. At the same time they must deal with interactions in the herd and need to learn and remember the identities and roles of other individuals in the herd.
Life for a domesticated horse is even more bewildering. In addition to dealing with natural situations, they often live in unsuitable environments, need to suppress instinctual behaviours and learn tasks that are not natural behaviours. They also need to co-exist with humans, who from a horses' viewpoint must be very strange indeed.
Research into the nature of cognition and perception in horses is gradually providing some fascinating insights.
Horses learn through habituation throughout their lives. In a new environment, horses are very reactive and pay attention to any stimulus perceived by any of their senses. However, when certain stimuli are insignificant and are repeated regularly, the response diminishes. Habituation is a simple form of learning, but none the less important, as it allows non-vital information to be filtered out subconsciously, enabling the horse to focus on what is significant.
When a horse is particularly sensitive or fearful, either by its nature or through learned experience, it can be desensitized. Rough handling of its ears, or a bit banging against its teeth may make a horse extremely sensitive to being bridled, for example. This leads to head shyness. Such a horse needs to be retrained by approaching its head in increments and retreating when necessary until the horse willingly accepts normal, gentle bridling.
Horses can become habituated and desensitized to almost overwhelming stressors if it is done correctly. A good trainer exposes horses in a positive manner to all sorts of sights, sounds and contacts, for instance by leaving him unrestrained in a safe corral and having humans behaving strangely around him, playing with bouncing beach balls, multicoloured balloons, umbrellas, plastic tarps, pylons, rattles etc. This makes the horse much more capable of handling novel events calmly. If desensitization is not done correctly, it has the potential to make a horse more fearful and sensitive, for instance by removing an alarming stimulus too soon.
Pavlovian conditioning does not only work for dogs.
A horse also learns effortlessly when initially unimportant stimuli or events are regularly coupled with stimuli that initiate some sort of response. This form of conditioning is used by a trainer when he places a word onto a behaviour. The word "trot" would mean nothing to an untrained horse, but if it is regularly paired with the flick of a whip (associated with invoking a flight response or pain) immediately before the horse changes gait on an upward transition, the horse soon learns to respond to the verbal cue, without the use of a whip.
The use of the word "good", when correct behaviour is carried out, followed by a food treat, informs the horse that a food reinforcer is forthcoming.
To many a veterinarians dismay, horses often learn that the sight of a syringe is associated with pain. The unconditioned horse will then attempt to escape if he has not been trained to accept such handling.
Stabled horses will learn to associate certain sounds with feeding - eg doors opening, hay being poured into a bucket, or will respond to visual cues , such as the arrival of the caretaker. They will then display sometimes unwelcome anticipatory behaviours, such as vocalizing, pawing or kicking stall doors. When reinforced, these may become conditioned behaviours. For instance, when a horse, upon hearing grain being poured, starts kicking his door, a person may feed the horse hurriedly in an attempt to get him to settle down. This positively reinforces the undesirable behaviour and if this scenario repeats itself, the horse has effectively trained the human to feed him quickly.
Operant conditioning, in contrast to classic or Pavlovian conditioning, occurs when an animal manipulates its environment to obtain reinforcement, which can be positive, when he receives something he desires, or negative - such as removing something unpleasant. Both types strengthen the relationship between stimulus and sought after response, so that when the same stimulus is given again, there is an increased chance that the horse will repeat the action.
In the early stages of learning the meaning of a new stimulus, the horse may respond randomly and hit upon the desired response by accident. Reinforcement of the response at the correct moment will cause the animal to repeat the behaviour. Horses excel at this type of learning, especially when positive reinforcement is given.
Unfortunately negative reinforcement is most often used in training. Horses are typically trained to perform actions to avoid something aversive. Under saddle they move forward when leg pressure is applied by the rider, on the ground they yield their hindquarters when pressure is applied to the flank, they back up when pressure is applied to the bridge of their nose, and they enter a trailer to avoid whips, or pressure from ropes. A good trainer refines this by reinforcing the correct and ignoring the incorrect. In this way only the slightest pressure will eventually produce the desired response, making the human/horse partnership appear effortless.
Research has been done with respect to the use of positive reinforcement principles to facilitate trailer loading of horses. It is not uncommon for a horse to be reluctant to be loaded onto a trailer. It can be very time consuming and hazardous for horse and handler. A horse may resist by rearing, pulling back, pawing, kicking or even falling over. If the owner gives up and fails to load the horse, such behaviour is reinforced. Traditional loading methods are based on negative reinforcement, often with some punishment for an uncooperative horse as well. Researchers Ferguson and Rosales-Rui found that , with positive reinforcement and target training, horses learned to load willingly and improper behaviours ceased. These effects also generalized to other novel situations. Horses that have learned to load through positive reinforcement do so eagerly, sometimes requiring only a verbal or visual signal, even when unrestrained. Positive reinforcement can also be targeted at lifting feet for hoof care, groundwork, grooming and veterinary handling.
Discrimination learning in horses has been researched since the 1930's. In discrimination tasks, horses must learn that one stimulus, and not another will result in positive reinforcement. That stimulus then begins to control behaviour, so that the horse acts in a specific manner in the presence of one stimulus, but not the other. In one study a specific horse learnt 20 pairs of discriminations. This horse also "learnt to learn" by using a general pattern to more easily solve subsequent tests. After 6 months he had also retained 77.5% of the discriminations. The "learning to learn" phenomenon has been noted in many other studies. It is a worthwhile tool in training. Often horses are restricted to performing only within a particular discipline. Racehorses don't jump; and dressage horses rarely set foot on a trail. These limitations prevent horses from learning about a variety of stimuli and such animals are less able to deal with novel situations. The more positive stimulation a horse experiences, the more readily it learns in new situations. It is also better adjusted in a variety of conditions and environments.
Spatial cues seem to be more readily discriminated by horses than any other stimuli. This is supported by observations made by vigilant horse owners of how well horses find their way around in areas they have only visited infrequently. Horses also react noticeably when objects in their environment are moved. This demonstrates an awareness of spatial surroundings.
The ease with which horses discriminate visual stimuli makes it easier for researchers to study cognition; and also to measure perceptual abilities and therefore equine vision. It has been experimentally demonstrated that a horse's visual acuity is 20/30 on the Snellen scale. (Human 20/20, dogs 20/50).
Experiments regarding colour vision in horses showed that they could discriminate red and blue from gray. Others showed that they could also discriminate between green and yellow. Recent research by Hanggi and Waggoner showed that horses responded to colour in the same manner as some red/green colour blind humans.
A myth that surfaces repeatedly is that horses cannot recognize what they have seen with one eye with the other eye. Anatomical dissections have proven that the horse's two cerebral hemispheres do indeed have a functional pathway to convey information, and a behavioural study proved that they do have inter ocular transfer. This study used multiple two choice discrimination tests with one eye blindfolded. Once the discrimination was learned, the blindfold was placed over the other eye. Horses immediately responded to the same stimulus, clearly demonstrating interocular transfer.
Horses often startle at an object they have seen before when approaching it from a different angle. This can be explained by the fact that the shape of the object appears differently when seen from another perspective. Experiments with different objects demonstrated that recognition of rotated objects was good under some but not all conditions.
With generalization a behaviour previously conditioned to one stimulus, transfers to other similar stimuli. Riding school horses regularly utilize this form of learning when making sense of a large assortment of inexact hand, leg and seat cues from riders of varying skill levels. Dressage horses, in contrast, learn to discriminate highly precise cues from their riders. As a result they go through mechanical motions that rarely enhance cognitive skills. A horse's generalization abilities can be enhanced by incorporating variety into their programs. As social animals, horses are most comfortable in the company of their own kind. Social interactions can facilitate the learning of new behaviour by observing other horses
The cognitive abilities of horses need to be understood to ensure good husbandry and treatment.
It is as harmful to confine a thinking animal to a dark, dusty stable with little or no social interaction as it is to provide inadequate feed or use abusive training methods. It is certainly in the best interests of both horses and handlers to better understand the scope of equine thinking, and enrich horses' environment. In the not too distant past little consideration was given to why horses behaved like they did. This limited the provision of adequate care and welfare. More recently research into equine cognition and perception has made noteworthy advances. This has led to a greater interest in training methodology and management. Even so, we are still a long way from fully understanding what it is to be a horse. More studies are needed to fully understand this remarkable animal and provide it with the best environment and training for its and our needs.
Blue-tongue in Sheep
Wild ruminants are infected by the virus, but do not show symptoms. In Africa, some large carnivores have antibodies to bluetongue. The virus was first recognised in South Africa and has since been found in Africa, Europe, the Middle East, Australia, the South Pacific, North and South America and parts of Asia. Geographic distribution is limited by the distribution of the Culicoides midges. Twenty four serotypes have been identified world-wide. Serotypes identified by the Onderstepoort Veterinary Institute in recent years are as follows:
a). 2008 and 2009 = 1;3;4;6;8;16;18;24
b). 2009 and 2010 = 1;3;4;6
The main vectors are various species of biting Culicoides midges. Ticks or sheep keds may be mechanical vectors and the disease may be spread on veterinary equipment. Cattle are the preferred hosts of many Culicoides species. They develop a prolonged viraemia and often amplify the virus, therefore playing a major role in transmission of the virus.
Infected animals remain infectious to the insect vector for several weeks. The incubation period in sheep is between 5 and 10 days. Cattle show viraemia at 4 days post-infection. They rarely develop symptoms.
Clinical signs seen in sheep include fever, depression, salivation, dyspnea and panting. The lips, ears and eyelids may be swollen and hyperaemic. Dyspnea and panting may be seen. The tongue is often very swollen, may be cyanotic and protrude from the mouth. The mouth often has erosions and ulcerations on mucous membranes. This may be sufficiently severe to lead to necrosis and sloughing of mucous membranes. Hooves are often painful and the coronary band hyperaemic, leading to lameness. Such animals should not be moved long distances, as this may contribute to sloughing of hooves. Abortions may occur, or so-called dummy lambs may be born to affected ewes. Other signs may be seen, such as torticollis, pneumonia and conjunctivitis. Some sheep may shed their wool three to four weeks after recovery. Severity of disease and death rate is influenced by the strain of virus.
At post mortem, the following signs may be seen:
Oedema of face and ears
Crusty nasal exudate
Hyperaemia of coronary bands
Petechia, erosions and ulcers on tongue and dental pad and rest of oral cavity.
Necrotic or cyanotic oral cavity
Trachea may be hyperaemic with foam.
Hydrothorax is seen occasionally
The heart may have petechiae, ecchymoses and necrotic foci.
The reticulum and omasum may show hyperaemia and erosions.
Characteristically haemorrhage is seen at the base of the pulmonary artery.
Oedema may be seen in intermuscular fascial planes and skeletal muscles may have focal haemorrhages or necrosis.
Cattle rarely show symptoms, although clinical signs have been seen and have included nasal discharge, swelling of head and neck, conjunctivitis, swelling and ulceration of the mouth, swollen teats, lethargy and salivation.
Clinical diagnosis is based on symptoms and insect activity. In cattle the disease must be confirmed by laboratory testing. Differential diagnoses include vesicular stomatitis, foot-and-mouth disease, rinderpest, photosensitivity due to plant poisoning, malignant catarrhal fever, infectious bovine rhinotracheitis, bovine virus diarrhoea, foot rot, oestrus ovis infection.
Laboratory diagnosis includes PCR. This allows for rapid diagnosis and can identify the serogroup and serotype. Several EDTA blood samples should be collected from several live febrile animals as early in the course of disease as possible.
Serology may also be used for diagnosis. Competitive ELISA identifies IgG antibodies and will be be positive from 7 to 14 days onwards. These antibodies are persistent. Complement fixation test is positive as early as 1 to 2 days after symptoms appear and measures IgM antibodies. These antibodies start to disappear by 7 days. (Personal communication: Dr. Alison Lubisi).
Serum neutralisation tests will identify the serotype involved.
Control is based on control of the insect vector. Peak populations of Culicoides occur in late summer and autumn. Synthetic pyrethroids or organophosphates are effective against Culicoides. Housing animals from late afternoon to early morning reduces the risk of infection. Animals should also be kept away from low-lying areas near open water.
Although the virus does not affect horses, Culicoides will feed on them and breed in manure piles, so this should be considered in control of an outbreak.
A freeze dried polyvalent live attenuated vaccine is available in South Africa. The vaccine is given as a series of three separate injections with different serotypes of bluetongue virus in each bottle. The vaccine will only stimulate immunity to all serotypes after a number of annual innoculations.
(See vaccine insert for full instructions. )
Grass Tetany in Cattle
Grass Tetany
The rain of the past few weeks have caused a flush of green grass everywhere. It has coincided with the arrival of a crop of new calves throughout the district.
Though wonderful to see, this grazing is not without its risks. Cows with autumn calves can develop grass tetany on new plant growth of grass and cereal crops.
Grass tetany is an often fatal metabolic disorder of cattle. It can occur anywhere, but is prevalent on the northern, central and southern tablelands and slopes of NSW.
Although it is primarily a deficiency of magnesium, it is a complex condition. Magnesium is an important component of the cerebrospinal fluid which surrounds the brain and spinal cord and it is essential for the transmission of nerve impulses. Magnesium cannot be stored in the body and is constantly being secreted in faeces, urine and milk. Cows in milk are especially at risk. Calcium levels also play a role in the expression of symptoms.
Symptoms:
Often farmers will be unaware of a problem until they find dead cows, with froth from the nose and mouth, and signs of a struggle before death.
In mild forms of hypomagnesemia, cows may show no symptoms until they are stressed by cold, oestrus or mustering for example, when symptoms may be seen. Early symptoms include twitching of the face and ears and face, a nervous, jumpy appearance and a stiff gait. In the next phase the cow is wild, her front legs are lifted too high in a goose stepping motion, the tail is held higher than normal and she may appear blind. This progresses to excitement, bellowing, galloping and staggering. The cow goes down on her side with stiff, outstretched legs. She paddles violently, her head arches back slightly and she froths at the mouth. The cow may die within minutes.
Low magnesium levels are also implicated in lazy calving syndrome.
Treatment:
There is often not enough time to call a veterinarian, but if one arrives in time, he/she will inject a calcium and magnesium compound intravenously, followed by subcutaneous magnesium. Intravenous injections require caution as giving it too fast, or giving too much, will kill the cow.
If you treat the cow yourself, do not disturb the cow until you are ready to start. Inject one or two plastic bags of commercially available calcium and magnesium solution under the skin, followed by 60 to 100 ml of 50% magnesium sulfate under the skin. Use sterile equipment. Inject each bag into a different site. If possible warm the bags to body heat in a bucket of hot water before use.
After recovery, feed the cow sixty grams of MgO (Causmag) daily.
Prevention:
The most effective supplement is hay treated with magnesium oxide. (Causmag) Daily Causmag requirement is 60 gram per cow per day. It takes two to three days before cows are protected. If supplementation is stopped, the protection ceases too. Excess Causmag can cause scouring.
To treat hay, a slurry is made of Causmag.
Causmag 6kg
Water 2L
Molasses 3kg
This will keep for 10 days.
The prepared slurry is poured onto biscuits or rolled out hay in sufficient quantities to ensure that each adult animal will consume 60g of Causmag daily.
(For other feeding methods, see DPI Primefact 421)
Causes:
Young grass and cereals have lower magnesium levels than older grass and cereals.
Grasses and cereal have lower magnesium levels than clovers and lucerne.
More advanced pastures normally have the three critical minerals, namely magnesium )Mg), calcium (Ca) and potassium (K) in balance. However when cold conditions below 7 degrees Celsius persist for four or more consecutive days, plant roots hibernate and cease to absorb nutrients from soil. As potassium is more chemically reactive than Ca of Mg, a build-up of potassium occurs around the roots of the plant. When temperature warms up again to night temperatures above 8 degrees and 16 degree days for four days, plants switch back to active root absorption and a rapid uptake of potassium (K) relative to Mg and Ca occurs. K suppresses Mg uptake in the rumen. This can trigger hypomagnesemia (lack of magnesium in blood) and grass tetany.
After about 5 days the plant mineral balance will stabilize again.
During a drought, plants will also absorb less minerals from soil, leading to buildup of available potassium in the soil.
After germinating rain, the excess available potassium is rapidly absorbed by new plant growth. This can trigger grass tetany. Ideally stock should be kept off pasture until it has grown to at least 12 cm in length.
Yarded animals that are being hand fed are also at risk after rain. Their manure which is rich in potassium, enriches the soil with potassium. In certain circumstances where rain has germinated short pick grass, animals may consume the grass as it appears. This is not always noticed by managers until losses occur.
Heavy nitrogen or potassium fertiliser application reduces magnesium availability to plants.
Anything that reduces the animals food intake can trigger grass tetany under the right conditions.
Prevention:
Grass tetany occurs where there are acid soils and high potassium levels. Prevention of soil acidification is a long term goal.
Spring calving cows will be less susceptible than autumn/winter calving cows.
Minimise stress in last 6 weeks of pregnancy and in cows with calves.
Avoid sudden changes in food. Leave the gate open to a fresh paddock so animals can move back and forth quietly until they get used to the new pasture.
Keep hay for cows and calves and give the green crop to steers. The best hay is legume hay. It contains the right nutrients to help prevent grass tetany.
Supplement susceptible livestock with Causmag or another MgO containing supplement.
Summary:
Grass tetany is a complex condition, with magnesium, calcium and potassium ratio playing a role.
The risk of a specific pasture causing problems can be evaluated by carrying out soil tests. Plant analysis is less meaningful as levels are constantly changing in the plant and can change within days.
This article provides general information only. Consult your vet to discuss how it applies to you.
Keywords: grass, tetany, magnesium, calcium, potassium
The rain of the past few weeks have caused a flush of green grass everywhere. It has coincided with the arrival of a crop of new calves throughout the district.
Though wonderful to see, this grazing is not without its risks. Cows with autumn calves can develop grass tetany on new plant growth of grass and cereal crops.
Grass tetany is an often fatal metabolic disorder of cattle. It can occur anywhere, but is prevalent on the northern, central and southern tablelands and slopes of NSW.
Although it is primarily a deficiency of magnesium, it is a complex condition. Magnesium is an important component of the cerebrospinal fluid which surrounds the brain and spinal cord and it is essential for the transmission of nerve impulses. Magnesium cannot be stored in the body and is constantly being secreted in faeces, urine and milk. Cows in milk are especially at risk. Calcium levels also play a role in the expression of symptoms.
Symptoms:
Often farmers will be unaware of a problem until they find dead cows, with froth from the nose and mouth, and signs of a struggle before death.
In mild forms of hypomagnesemia, cows may show no symptoms until they are stressed by cold, oestrus or mustering for example, when symptoms may be seen. Early symptoms include twitching of the face and ears and face, a nervous, jumpy appearance and a stiff gait. In the next phase the cow is wild, her front legs are lifted too high in a goose stepping motion, the tail is held higher than normal and she may appear blind. This progresses to excitement, bellowing, galloping and staggering. The cow goes down on her side with stiff, outstretched legs. She paddles violently, her head arches back slightly and she froths at the mouth. The cow may die within minutes.
Low magnesium levels are also implicated in lazy calving syndrome.
Treatment:
There is often not enough time to call a veterinarian, but if one arrives in time, he/she will inject a calcium and magnesium compound intravenously, followed by subcutaneous magnesium. Intravenous injections require caution as giving it too fast, or giving too much, will kill the cow.
If you treat the cow yourself, do not disturb the cow until you are ready to start. Inject one or two plastic bags of commercially available calcium and magnesium solution under the skin, followed by 60 to 100 ml of 50% magnesium sulfate under the skin. Use sterile equipment. Inject each bag into a different site. If possible warm the bags to body heat in a bucket of hot water before use.
After recovery, feed the cow sixty grams of MgO (Causmag) daily.
Prevention:
The most effective supplement is hay treated with magnesium oxide. (Causmag) Daily Causmag requirement is 60 gram per cow per day. It takes two to three days before cows are protected. If supplementation is stopped, the protection ceases too. Excess Causmag can cause scouring.
To treat hay, a slurry is made of Causmag.
Causmag 6kg
Water 2L
Molasses 3kg
This will keep for 10 days.
The prepared slurry is poured onto biscuits or rolled out hay in sufficient quantities to ensure that each adult animal will consume 60g of Causmag daily.
(For other feeding methods, see DPI Primefact 421)
Causes:
Young grass and cereals have lower magnesium levels than older grass and cereals.
Grasses and cereal have lower magnesium levels than clovers and lucerne.
More advanced pastures normally have the three critical minerals, namely magnesium )Mg), calcium (Ca) and potassium (K) in balance. However when cold conditions below 7 degrees Celsius persist for four or more consecutive days, plant roots hibernate and cease to absorb nutrients from soil. As potassium is more chemically reactive than Ca of Mg, a build-up of potassium occurs around the roots of the plant. When temperature warms up again to night temperatures above 8 degrees and 16 degree days for four days, plants switch back to active root absorption and a rapid uptake of potassium (K) relative to Mg and Ca occurs. K suppresses Mg uptake in the rumen. This can trigger hypomagnesemia (lack of magnesium in blood) and grass tetany.
After about 5 days the plant mineral balance will stabilize again.
During a drought, plants will also absorb less minerals from soil, leading to buildup of available potassium in the soil.
After germinating rain, the excess available potassium is rapidly absorbed by new plant growth. This can trigger grass tetany. Ideally stock should be kept off pasture until it has grown to at least 12 cm in length.
Yarded animals that are being hand fed are also at risk after rain. Their manure which is rich in potassium, enriches the soil with potassium. In certain circumstances where rain has germinated short pick grass, animals may consume the grass as it appears. This is not always noticed by managers until losses occur.
Heavy nitrogen or potassium fertiliser application reduces magnesium availability to plants.
Anything that reduces the animals food intake can trigger grass tetany under the right conditions.
Prevention:
Grass tetany occurs where there are acid soils and high potassium levels. Prevention of soil acidification is a long term goal.
Spring calving cows will be less susceptible than autumn/winter calving cows.
Minimise stress in last 6 weeks of pregnancy and in cows with calves.
Avoid sudden changes in food. Leave the gate open to a fresh paddock so animals can move back and forth quietly until they get used to the new pasture.
Keep hay for cows and calves and give the green crop to steers. The best hay is legume hay. It contains the right nutrients to help prevent grass tetany.
Supplement susceptible livestock with Causmag or another MgO containing supplement.
Summary:
Grass tetany is a complex condition, with magnesium, calcium and potassium ratio playing a role.
The risk of a specific pasture causing problems can be evaluated by carrying out soil tests. Plant analysis is less meaningful as levels are constantly changing in the plant and can change within days.
This article provides general information only. Consult your vet to discuss how it applies to you.
Keywords: grass, tetany, magnesium, calcium, potassium
Nitrate Poisoning in Livestock
Significant Stock Losses caused by Drought Feeding.
Deaths were caused by drought feeding of millet silage in one case and millet hay in the other. Approximately 10% of cattle died apparently overnight after being fed the millet products.
Laboratory tests confirmed that the cause was nitrate/nitrite poisoning in both cases.
Nitrates in fodder are converted to nitrites in the rumen. Nitrates in stored fodder can also be converted to nitrites when plant materials heat up or are attacked by bacteria or fungi. Normal levels of nitrite are converted to ammonia in the rumen by bacterial action. However excessive levels of nitrate or nitrite are poisonous.
Certain soil and environmental conditions facilitate nitrate uptake and accumulation by plants, eg.:
Use of nitrogen containing fertilizers
Low soil sulfur and molybdenum
Areas where stock have congregated and urinated and defecated (stock yards)
Drought
Cloudy or cold weather
Herbicide application, esp 2.4-D
Wilting
Plant species
Stage of maturity of plant
Part of plant
Young plants have higher nitrate concentrations and most plant nitrate is located in the bottom third of the stalk.
Hays made from cereal crops, especially those grown under drought conditions and cut while "sappy" can develop toxic nitrite levels when they heat up.
Hays contain almost the same level of nitrate as the parent crop. Silage normally contains significantly less due to the fermentation process.
Sheep are less susceptible to nitrite poisoning than cattle, but can also be affected.
Stressed animals in poor health or poor condition are more susceptible and hungry animals are more likely to eat large amounts.
The risk of poisoning can be reduced by
Having feeds and forages analysed for nitrate levels.
Gradually introducing any new feeds by feeding small amounts frequently and diluting with known safe feeds.
Cattle can become acclimatized to relatively high levels of nitrate this way.
Frequent observation of stock, especially when changing food or grazing.
Don't overstock.
Prevent hungry stock from grazing on high risk fodder.
Do not graze high nitrate pastures for 7 days after rainfall, cloudy weather, frosts or high temperatures causing wilting.
Do not harvest pastures under these conditions either.
Graze these pastures during sunny afternoons above 15 degrees Celsius and remove livestock at night.
Never feed mouldy hay.
Harvest crops close to maturity and raise the cutter head selectively to avoid the bottom part of the stalk.
Keep in mind that rapidly growing weeds after rainfall may also contain excessive levels of nitrate as well as cyanide (prussic acid).
Keywords: cattle, sheep, fodder, drought, grazing, millet, nitrate, nitrite, 2.4 -D.
Deaths were caused by drought feeding of millet silage in one case and millet hay in the other. Approximately 10% of cattle died apparently overnight after being fed the millet products.
Laboratory tests confirmed that the cause was nitrate/nitrite poisoning in both cases.
Nitrates in fodder are converted to nitrites in the rumen. Nitrates in stored fodder can also be converted to nitrites when plant materials heat up or are attacked by bacteria or fungi. Normal levels of nitrite are converted to ammonia in the rumen by bacterial action. However excessive levels of nitrate or nitrite are poisonous.
Certain soil and environmental conditions facilitate nitrate uptake and accumulation by plants, eg.:
Use of nitrogen containing fertilizers
Low soil sulfur and molybdenum
Areas where stock have congregated and urinated and defecated (stock yards)
Drought
Cloudy or cold weather
Herbicide application, esp 2.4-D
Wilting
Plant species
Stage of maturity of plant
Part of plant
Young plants have higher nitrate concentrations and most plant nitrate is located in the bottom third of the stalk.
Hays made from cereal crops, especially those grown under drought conditions and cut while "sappy" can develop toxic nitrite levels when they heat up.
Hays contain almost the same level of nitrate as the parent crop. Silage normally contains significantly less due to the fermentation process.
Sheep are less susceptible to nitrite poisoning than cattle, but can also be affected.
Stressed animals in poor health or poor condition are more susceptible and hungry animals are more likely to eat large amounts.
The risk of poisoning can be reduced by
Having feeds and forages analysed for nitrate levels.
Gradually introducing any new feeds by feeding small amounts frequently and diluting with known safe feeds.
Cattle can become acclimatized to relatively high levels of nitrate this way.
Frequent observation of stock, especially when changing food or grazing.
Don't overstock.
Prevent hungry stock from grazing on high risk fodder.
Do not graze high nitrate pastures for 7 days after rainfall, cloudy weather, frosts or high temperatures causing wilting.
Do not harvest pastures under these conditions either.
Graze these pastures during sunny afternoons above 15 degrees Celsius and remove livestock at night.
Never feed mouldy hay.
Harvest crops close to maturity and raise the cutter head selectively to avoid the bottom part of the stalk.
Keep in mind that rapidly growing weeds after rainfall may also contain excessive levels of nitrate as well as cyanide (prussic acid).
Keywords: cattle, sheep, fodder, drought, grazing, millet, nitrate, nitrite, 2.4 -D.
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