Goat Nutrition Information
|
Don’t my Goats they get what they need from forages?
While most goats receive adequate mineral levels from available forages in order to
survive, the vast majorities are not receiving the mineral nutrition needed for high
levels of production. An important point to remember is that the mineral content of
forages are limited by the mineral make-up of the soils.
If it’s not in the soil, it can’t get into the plant. And while soil types vary, no one soil
type provides optimum levels of all the minerals needed by goats, therefore mineral
supplementation is advisable. Other variables such as plant species, plant maturity
and climate conditions will also play a role in the mineral content of forages.
When most people think of mineral deficiencies they think of severe clinical
deficiencies, which have easily identifiable symptoms (such as white muscle disease
in selenium deficiency). However, as shown in Figure 1, subclinical trace mineral
deficiencies will adversely affect immunity, reproduction and growth long before
clinical deficiency symptoms are observed. Subclinical trace mineral deficiencies are
quite common in all livestock (not just goats) and most producers do not recognize
these deficiencies as a problem since they are hard to identify. Animals grow and
reproduce seemingly normally; they just do so at reduced rates, more inefficiently
and at higher input costs. For these reasons, it is imperative that goat producers
supplement trace minerals in order to maintain efficient production. In many cases, it
could be the difference between profitability and loss.
The relationship between mineral status and onset of subclinical and clinical disease
symptoms. Based on S. Wikse, 1992. Texas A&M Univ. Beef Cattle Short Course.
What minerals are needed and what do they do?
Minerals are loosely grouped into two categories: the macro-minerals and the micro-
or trace minerals. Macro minerals include: calcium, phosphorus, magnesium,
potassium, sulfur and salt and are needed in relatively large amounts in the body.
The trace minerals include: cobalt, copper, iodine, iron, manganese, selenium and
zinc and are needed in very small or “trace” amounts in the body. While
adequate amounts of all of the above mentioned minerals are important to proper
nutrition, copper, selenium, and zinc are deficient in most goat diets in the United
States and therefore, I will focus on these trace minerals for the remainder of this
article Copper. Various levels of copper deficiency are a serious problem for grazing
goats and cattle in the United States. Copper is essential for enzyme functions,
immunity, connective tissue metabolism and iron metabolism among other functions.
It is theorized that reproductive efficiency is reduced due to alterations of enzyme
systems caused by low copper levels. Copper deficiency can result in delayed estrus,
reduced libido, decreased conception rates, infertility, early embryo death, necrosis
of the placenta and central nervous system abnormalities in offspring. High levels of
iron, sulfur or molybdenum in the soil or additional feed supplements can further
exaggerate these deficiency symptoms.
Newborns are very dependent on copper acquired during the prenatal period since
copper levels in milk are poor. Therefore, proper copper nutrition in gestating females
is critical to body stores in newborns. Maternal copper deficiency has been linked to
increased mortality and morbidity in lambs and calves.
Copper requirements of goats are not entirely known. Much of what is known of goat
nutrition has been extrapolated from sheep and cattle research. The established
copper recommendations for goats are 8 to 10 ppm in the total diet. However, recent
studies with goats have suggested that goats may be able to tolerate higher levels of
copper in their diets with no detrimental effects, at least temporarily. Optimum
copper levels for enhanced growth and production in the Boer have not yet been
established. Selenium. Selenium is an anti-oxidant that works in conjunction with
Vitamin E to prevent and repair cellular damage in the body. Selenium and/or Vitamin
E deficiency has been shown to impair immune response. Selenium is also associated
with thyroxine, a thyroid hormone that regulates metabolism, reproduction,
circulation and muscle function. Selenium also protects the body from heavy metals
by forming complexes to render them harmless. Selenium is readily transferred
through the placenta and milk; therefore, a doe’s selenium status will directly affect
the health and thriftiness of her kids.
Most of the soils in the U.S. are marginal to deficient in selenium, but there are areas
in the Western U.S. that are abundant in plants that accumulate selenium (for
example locoweed). Severe clinical selenium deficiency can result in white muscle
disease, characterized by stiffness and heart failure.
Marginal selenium deficiencies can result in impaired fertility, silent heats, cystic
ovaries and the birth of unthrifty kids with poor immunity. Selenium requirements in
cattle have been shown to increase under the following conditions: high levels of
legumes in diet, high sulfur intake, low vitamin E intake, and high levels of heavy
metals in the diet.
The United States Food and Drug Administration tightly regulates selenium as a
result of toxicity concerns. Selenium is highly toxic if excess amounts are consumed.
Unfortunately, the amount of selenium required is very close to the toxicity level,
thus great care must be taken when supplementing selenium. The maximum level of
selenium that can be legally be fed to goats in the United States is 0.7 mg per head
per day or 0.3 ppm in the total ration (dry matter basis). Zinc.
Zinc is known to be essential for sexual maturity, and onset of estrus. Zinc plays a
role in epithelial integrity, meaning that zinc is essential for maintaining the lining of
the reproductive organs. Adequate zinc levels are vital for repair of the uterine lining
following kidding, return to normal estrus cycles and maintenance of the uterine
lining necessary for implantation of embryos. Inadequate zinc levels in cattle
have been associated with abortion, fetal mummification, lower birth weights and
prolonged labor. Zinc is also vital to sperm quality in males.
Zinc and copper also affect reproduction indirectly through hoof and joint health.
Bucks that are lame will not actively seek out does in heat, follow and mount them.
And even if they mount, they may not ejaculate due to associated pain. Therefore,
structural soundness of feet and legs is vital to reproductive efficiency in bucks.
What if I feed trace-mineralized salt?
Unfortunately, trace mineralized salt in loose or block form will not meet all of goats’
nutritional needs. Trace mineralized salt is mostly salt (typically 92 to 98% salt) and
contains relatively low levels of trace minerals as compared to complete mineral
supplements. Because of the high salt content, consumption of these supplements
will be very low; resulting in sub-optimum intakes of needed trace minerals. For
this reason, I strongly recommend use of a complete mineral supplement designed
especially for goats.
Think of Mineral Supplementation as an Insurance Policy Just like you pay every
month for car insurance “just in case” you get into an accident, it is best to provide a
complete mineral supplement “just in case” your goats aren’t receiving adequate
levels of minerals from forages. The cost of auto insurance seems
high until you think about how much an accident would cost, then it seems like a
bargain. In the same sense, the cost of mineral supplementation seems high until you
factor in the costs in lost profits and reduced production caused by inadequate
mineral nutrition. By maintaining high quality pastures you can meet the majority of
your goat’s nutritional needs, but by providing free choice access to a complete
mineral & vitamin supplement you can make sure that ALL of the goat’s nutritional
needs are being met. For a cost of pennies per day, you can ensure that your
production objectives are not being hampered by inadequate mineral nutrition.