THE IMPORTANCE OF CALCIUM
By AKKPS Member Debra Allen of Allen's Acres
Minerals constitute a small percentage of swine diets, but their importance to growth, health, and productivity of the pig cannot be over-emphasized. Swine require 15 minerals in their diet and macro-minerals are the minerals that swine need in larger quantities, usually described for inclusion in percent of the diet. The macro-minerals are: calcium, phosphorus, sodium, chlorine, potassium, magnesium, and sulfur. About 5 percent of the total body weight of swine consists of minerals. Although these minerals are found in most feed grains, some are at low concentrations in feeds commonly used in swine diets. Consequently, it is essential that the diet be balanced using supplemental mineral sources. Minerals are essential for most of the basic metabolic reactions in the body and are an important factor in growth, reproduction, and resistance to diseases. They have a role in digestion; metabolism of protein, fats, and carbohydrates; and the structure of chromosomes, enzymes, nerves, blood, skeleton, hair and milk. The efficiency of mineral absorption depends on concentration of that mineral in the diet, the mineral source and its availability, mineral to mineral interactions in the diet, and the mineral status of the animal. Most swine depend primarily on their daily feed to supply needed mineral requirements. However, minerals should not be added to the diet haphazardly. Overuse can lead to serious consequences, including antagonistic interactions between minerals leading to potential deficiencies and impaired growth of the pig.
CALCIUM & PHOSPHORUS
Calcium and phosphorus play an important role in the development and maintenance of the skeletal system, blood clotting, muscle contraction and many other regulatory functions. Calcium and phosphorus are the two most abundant minerals in the pig. In the pig 96-99% of the calcium and 60-80% of the body phosphorus is found in the skeletal system. These two minerals must be considered together when formulating diets based on the pig’s requirements, as their ratio to each other can greatly affect their absorption and utilization in the body. The accumulation of calcium and phosphorus in bone is interdependent and one will not accumulate without the other. In bone, calcium and phosphorus are deposited in a 2.2:1 ratio.
THE ROLE OF CALCIUM
More than 90 percent of all calcium in the body is found in bones and teeth. Thus, calcium is the most important mineral when it comes to skeletal development and maintenance. Non-skeletal functions, in the form of ionized calcium, include muscle contraction and relaxation (birth procedure in sows), nerve conduction, regulation on blood clotting, and cell signaling in immune responses. Clearly, calcium is an important nutrient, although not always recognized as much as in humans.
CALCIUM
A deficiency in calcium can result in improper bone formation, reduced bone strength, lameness, and under extreme deficiency, poor growth. In young pigs this deficiency can be observed as rickets. However, in mature swine, pigs will remove calcium from their bones when fed a deficient diet, weakening their bones. This is the most common cause of “downer” sows post-weaning. The sow depleted her bone reserves to meet milk production demands and consequently created bones that are brittle and break easy during the moving, mixing and fighting post-weaning.
The calcium content of corn, small grains and soybean meal is very low and requires swine diets to be supplemented with calcium in all phases of swine production. In the U.S., most of the pig’s calcium requirement (50-75%) is typically met by feeding calcium carbonate (ground limestone). The remainder is typically met by supplemental phosphorus sources like mono- or di-calcium phosphate which contain a substantial amount of calcium.
Calcium is rarely considered to be a limiting nutrient in pig feeds because it is abundant and cheap. Limestone and calcium carbonate – the two most common sources of calcium – are readily available, and at competitive prices. But there are cases where calcium deficiency or toxicity, or under- and over-supplementation, can occur, causing considerable problems. Despite its abundance and low price, calcium cannot be used without caution and, as it happens, this is the case as it is invariably being used as a common carrier for many products.
CALCIUM REQUIREMENTS
Calcium requirements range from about 1 percent of complete feed for breeding gilts and sows, down to about 0.5 percent for finishing pigs. Research on this subject is quite old. Several organizations occasionally publish their estimates based mostly on experience and common practice.
CALCIUM DEFICIENCY
A mild calcium deficiency will cause poor development of the skeletal system, resulting in an increased number of “broken backs” at the slaughterhouse (especially in pigs finished at very heavy weights), and in poor leg condition in aged sows. This is certainly a chronic problem caused by improper feed formulation and lack of taking into consideration actual feed intake, current performance levels, and other interacting factors, including the feed manufacturing system (for example, the degree of accuracy in weighing ingredients).
A severe deficiency, highly unlikely to occur under modern production practices, is causing rickets (poorly developed bones causing malformation) in growing pigs and osteomalacia (brittle bones) in mature pigs. Such problems can occur when a feed mixing or formulation error happens due to negligence.
CALCIUM TOXICITY
Calcium toxicity is very rare and, again, it only occurs by accidental overdose due to a mixing or formulation errors. Pigs are quite resistant to calcium overdose, but a chronic toxicity will cause internal calcification of organs and growth stasis. Most problems are attributed to reduced absorption of phosphorus and zinc rather than hypercalcemia itself.
CALCIUM IN SOW & PIGLET DIETS
PIGLETS
Calcium carbonate and limestone have a very strong buffering capacity in that they can neutralize hydrochloric acid secreted in the stomach. This acid is the first step in the enzymatic breakdown of proteins and, with its suppression, undigested proteins pass onto the large intestine, where they can be used as “food” by pathogenic bacteria such as Salmonella and Collibacteria, causing severe diarrheas. To make matters worse, hydrochloric acid secretion is not fully developed in recently weaned pigs. This is why extra calcium is not recommended for young piglets.
SOWS
Most diets for developing gilts and breeding sows (gestating, dry and lactating) do not contain adequate calcium. With the major cause of sow culling being leg problems, it is logical to assume that sound development of bone structure should be of paramount importance from an early age.
Instead, most developing gilts receive calcium levels suitable for growing-finishing pigs, but clearly inadequate for long-term bone development. As such, they enter the reproductive cycle with a weak or rather under-developed skeleton system. Overfeeding during gestation, a common problem, offers little in terms of improving bone development at an early age as most gestating diets are usually low in calcium. In addition, fat sows during lactation exhibit poor feed intake, causing substantial loss of calcium from the bones, which is very hard to replace as sows age.
Calcium is also involved in the initiation of milk production in recently farrowed sows. Manipulation of calcium supplementation right before and after farrowing has shown to increase milk yield during the first week of lactation. And let’s not forget that proper calcium levels are required for proper uterine contraction during farrowing.
PHOSPHORUS
Phosphorus is required in the diet of pigs for proper skeletal growth and mineralization, as well as cellular functions. In the pig, approximately 75% of the phosphorus in the body is in the skeleton while 25% is in soft tissues. Phosphorus is found in every cell in the body serving in the energy system (ATP), cell structural components like phospholipids, phosphorylation sites for enzyme activation, and an initiation factor for protein synthesis. The amount of phosphorus required for growth is less than the amount required for maximum bone development. A dietary phosphorus deficiency has an immediate depressing effect on appetite, growth rate, and feed efficiency of swine.
In swine nutrition, phosphorus can be expressed in three different ways: total, bio-available, or digestible phosphorus. Total dietary phosphorus is the chemically analyzed amount of phosphorus in the diet, but does not provide any indication of the amount of phosphorus that is available to the pig for maintenance and growth. Many of the feedstuffs used in swine diets are of plant origin and the phosphorus in these ingredients is poorly digested by the pig. This is because the majority of phosphorus (60-90%) is bound in a phytic acid ring called phytate [3]. Pigs do not have the digestive enzyme, phytase, to remove the phosphorus from this structure and therefore this phytate phosphorus is unavailable to the pig. Commercial phytase is available for use in swine diets.
CALCIUM / PHOSPHORUS RATIO
The calcium to phosphorus ratio is important in swine nutrition. A wide calcium to phosphorus ratio will decrease the absorption of phosphorus, especially when phosphorus is fed near the requirement level. A narrower calcium to phosphorus ratio will result in more efficient phosphorus absorption and is more critical in the young pig. The suggested calcium to total phosphorus ratios in the National Swine Nutrition Guide is 1-1.2:1 across production phases. In general, the recommended calcium to bio-available phosphorus ratio is 1.4-2.4:1 and the ratio is from 1.6-3.0:1 for calcium to digestible phosphorus, both increasing as the pig matures from the nursery period to grow-finish and sow production phases. Calcium and phosphorus are required in many common biological functions, but in the gastrointestinal tract they act as antagonists. Thus, an oversupply of one causes reduced absorption of the other. This is mostly a problem with phosphorus, which is always limiting as it is more expensive, but diets marginal in calcium (by design or accident) can be detrimental for reproductive sows requiring ample quantities of calcium. Calcium also interacts in the same way with zinc.
CALCIUM & VITAMIN D
Vitamin D enhances the absorption and utilization of calcium, enhancing the development of the skeletal system. A new form of vitamin D metabolite (25-hydroxy-cholecalciferol or 25-OH-D3) has been shown to improve bone mineralization and even enhance reproductive performance, beyond levels possible even by super-alimentation with extra calcium and vitamin D. This is particularly important for gilts and aging sows.
OSTEOMALACIA
Osteomalacia is a condition responsible for the downer sow syndrome. Fractures of the long bones at the mid shaft and fractures of the lumber vertebrae are common, with the sow becoming paraplegic. The condition is due to inadequate levels of calcium, phosphorous and vitamin D in the ration. Sometimes sows cannot absorb sufficient micro-nutrients in spite of there being adequate levels in the diet. OM is also associated with immature skeletons, an imbalance of calcium and phosphorus and vitamin D and/or a failure of the sow to consume adequate feed and satisfy her nutritional requirements. Large amounts of calcium and phosphorus are excreted into milk from the bones resulting in weaker less dense bone which predisposes to fractures. Bone mass is also lost due to lack of exercise during confinement in the farrowing crate.
Clinical signs
Sows
- Seen in the first litter gilt.
- Dog sitting position.
- Stiffness
- Sudden acute lameness during lactation or immediately post weaning.
- Fractures.
- Pigs show pain / discomfort.
Piglets
- N/A
Weaners and Growers
- Stiffness.
- Lameness.
- High incidence of fractures of the main bones at slaughter.
Diagnosis
This is by the clinical signs.
Similar diseases include:
- Leg weakness or osteochondrosis.
- Spinal fractures.
- Torn muscles at their insertions into the bones.
- Mycoplasma hyosynoviae infection
Causes
- Inadequate diet.
- Heavy milk production.
- Low feed intake in lactation.
- Breed of animal.
- Shortage of vitamin D3.
- Low calcium in the diet.
Prevention
Once OM has developed treatment is of minimal effect although injections of calcium phosphorus and vitamin D may help. If your herd has a problem consider the following:
- Feed a high dense diet in lactation and 18% protein.
- Check the levels of calcium and phosphorus (minimum 0.9% and 0.75%). In first litter animals it may be necessary to raise the levels to 1.2% and 1%.
- Give up to 100,000iu vitamin D3 by injection 10 days before farrowing.
- Keep gilt litters to ten piglets or less.
- Top-dress the feed in lactation with calcium/phosphorus.
- Bone ratios of calcium/phosphorus in affected sows are often 3:1 (normal < 2:1)
- Use a good lactation diet and feed through breeding to post-farrowing
- Provide non slip floors
- Provide exercise to the pregnant gilt.
- Check parasite levels to ensure no dietary insufficiencies arise.
Treatment
- In the early stages move the sow to well bedded housing.
- If there are no fractures inject with calcium and vitamin D3
- If there is a problem in first litter females inject them with vitamin D3 after farrowing and 7 days later.
- Supplement the diet with dicalcium bone phosphate 30g day of sterilized bone flour.
- If there are fractured bones affected sows should be culled or euthanized.
ECLAMPSIA - MILK FEVER
Eclampsia is a life-threatening condition in pigs that occurs when a nursing sow has low calcium levels in her blood. It can happen at any point, but is most likely to occur within a week of giving birth.
Signs
- Sudden distress
- Heavy panting
- Shaking and trembling
- Fits and convulsions
- High body temperature
- Collapse
Causes
- A calcium deficiency in the sow's diet
- The sow losing calcium in her colostrum
- The sow being a heavy milker
Diagnosis
This is based on the sudden onset and the clinical signs presented but it can be confused with the porcine stress syndrome (PSS). The response to calcium injections if given early enough help to differentiate. Most animals with PSS die regardless of treatment
Treatment
- This involves giving up to 100mls of 40 percent calcium gluconate by injection or as directed by a vet.
- Ideally the injection should be given intravenously but this can be difficult.
- Alternatively, 25mls should be given by intramuscular injection at four separate sites in the neck. The muscles in the rump can also be used.
- Cool the sow by spraying with cold water.
KIDNEY STONES
Studies have shown that there is a correlation between imbalance of minerals (primarily calcium) and the production of kidney stones in many species of animals. There may also be an excess protein component as well but there are few studies done. Goats, sheep, horses, pigs, dogs and cats are seen by vets with calcium based kidney stones. In studies in pot belly pigs, the vast majority (93% vs 7%) of pigs presenting with symptoms are male vs female, and 73% of affected male pigs were barrows. The ureter in a male pig is longer and narrower than a females which might cause this discrepancy.
Risk factors for development of urolithiasis in commercial pigs include reduced water intake, high or low urinary pH, imbalances in the diet, urinary stasis, and preexisting urinary tract infections. Symptoms may include lethargy, inability to pass urine or dribbling urine, rectal prolapse, abdominal distension or swelling, reluctance to move, hunched back. A veterinarian can diagnose kidney stones with an X-ray or ultrasound. They can also take a urine sample to check for calcium-containing crystals and signs of a urinary tract infection.
Treatment may include acidification of urine with oral administration of ammonium chloride has been recommended for prevention of struvite and calcium phosphate urinary calculi in goats, sheep, horses, dogs, and cats. Surgical intervention may be needed.
DO NOT feed bone meal to pigs! Yes, it’s a good source of calcium however it’s illegal in many places, due to risk of disease transmission. Commercial calcium additives are normally calcium carbonate sourced from ground limestone.
OTHER ADDITIVES
Tums or generic equivalent. Tums contain calcium carbonate and dissolve quickly when given orally. The fruit flavored ones are more palatable to pigs than the mint ones usually. They can be hidden in other treats if they won’t eat them plain. Stuffed into a Twinkie or a slice of bread may entice a pig to eat it. There is no “normal dose” but many breeders give 4-6 tablets daily for 3-5 days pre-farrowing and 3-5 days post farrowing.
TransRite Sow Ultra. A feed top dress given as labeled prefarrowing is said to provide the needed calcium for:
- Addresses Farrowing Stress
- Optimizes Farrowing Time
- Supports Muscle Contraction
- Maximizes Feed Intake Post-Farrowing
Calf Manna. This is a general multiple species feed top dress that many breeders swear by when their animals are undergoing stress. Whether it’s gestation, farrowing, showing, or transporting…many add Calf Manna per label directions.
Calcium gluconate injection. Given under direction by a veterinarian, calcium gluconate is injected when calcium depletion is suspected in a sow with poor uterine contractions or dystocia (difficult or slow labor). It can be included in a farrowing kit as long as directions for use are given by a vet.
Vit D. Available as an injection or a drinking water additive. Rarely used in kunekune as they are able to synthesize Vit D from the sun just like humans. More commonly used in confinement operations.
High calcium foods as treats. Green leafy vegetables like kale, spinach, collard greens etc. all contain high amounts of calcium. Legumes are a good source including alfalfa, clover, and soybean hay. Egg shells. Milk, whey, and by products are good treats but care must be exercised to only give in moderation to prevent an imbalance in Ca/Ph ratios.