Microminerals usually supplemented in goat rations are iron, copper, cobalt, manganese, zinc, iodine, selenium, molybdenum Goats are ruminants, animals with a four-compartment stomach, as are cattle, sheep and deer. The compartments are the reticulum, rumen, omasum and abomasum, or true stomach. Monogastric or simple-stomached animals such as humans, dogs and cats consume food that undergoes acidi
c breakdown in the stomach and enzymatic digestion in the small intestine, where most nutrients are absorbed. In ruminants, feed first undergoes microbial digestion in the reticulum and rumen — together, often called the reticulo-rumen — prior to acidic digestion in the abomasum and enzymatic digestion and nutrient absorption in the small intestine. The microbial digestion in the reticulo-rumen allows ruminants to consume and utilize grass, hay, leaves and browse. The reticulum and rumen form a large fermentation vat that contains microorganisms, mainly bacteria, that breakdown and digest feedstuffs, including the fibrous component of grass, forbs, and browse that cannot be digested by monogastric animals. Some of the breakdown products produced through digestion of feed by bacteria are absorbed by the animal through the rumen wall and can supply a large part of the energy needs. The rest of the byproducts of digestion, undigested feed and ruminal microorganisms flow out of the reticulo-rumen into the omasum where large feed particles are trapped for further digestion and water is reabsorbed. Material then flows into the abomasum where acidic digestion takes place and then to the small intestine for further enzymatic digestion and nutrient absorption. abomasum. The rumen provides several advantages to the goat in addition to digestion of dietary fiber. The bacteria in the rumen are capable of synthesizing all B vitamins needed. Bacteria can also synthesize protein from nitrogen recycled in the body, which may be advantageous in low protein diets. For proper ruminal function, goats require a certain level of fiber in the diet, measured as crude fiber, acid detergent fiber or neutral detergent fiber. They have bacteria in the rumen that can detoxify anti-nutritional factors like tannins. This enables goats to better utilize feedstuffs containing high tannin levels such as those found in browse. There are very few situations in which a goat will not consume adequate fiber, but they may do so when being fed a very high-grain diet. Inadequate fiber consumption can then lead to several disease conditions. The most serious disease condition is acidosis, or an extremely low pH in the rumen, causing decreased feed consumption. When ruminants are born, the first three compartments of the stomach are underdeveloped and the stomach functions similar to that of a monogastric animal. This enables absorption of antibodies in colostrum and efficient utilization of nutrients in milk. As the young ruminant consumes solid feed, especially high in fiber, and the microbial population is established, the rumen is stimulated to develop. The rumen must have an acceptable degree of development for successful weaning. The greatest asset goats have is the ability and tendency to utilize woody plants and weeds, not typically consumed by other species of animals like cattle and sheep, converting these plants into a saleable product. These plant species can be inexpensive sources of nutrients and make for a very profitable goat enterprise. Goats typically consume a number of different plant species in any one day and can utilize some poisonous plants because they do not consume levels high enough to be toxic. Similarly, goats are believed to have a relatively high ability to detoxify absorbed anti-nutritional factors. Goats are more resistant to bloating than other ruminants and after a brief adaptation may graze alfalfa without bloating. The environmental cue most dominantly affecting seasonal breeding in small ruminants is the annual change in day length (goats are considered short day breeders). Seasonal anestrous occurs when the day length increases and this period is associated with an absence of estrus and ovulation and decreased secretion of the reproductive hormones. Seasonal species are responsive to a hormone called melatonin which is produced by the pineal gland in response to declining periods of light. Melatonin secretion is required to stimulate gonadotropin releasing hormone (GnRH) secretion in order to promote cycling. Melatonin is synthesized and secreted during the night hours when it is converted from serotonin in the pineal gland. Therefore, light entering the eyes inhibits pineal gland conversion of serotonin to melatonin. The pineal gland acts as a regulator of reproductive activity since it can either stimulate or inhibit gonadal function. During short photoperiods, such as in the fall, the long duration of high melatonin secretion switches on short day breeders such as sheep and goats and switches off long day breeders such as the horse and hamster. This explains why increased light (long days) would cause anestrus in goats since this inhibits the conversion of serotonin. Goats are therefore considered to be short day breeders because they begin to cycle during the shorter days of fall. The normal breeding season of goats is during the months of September, October, and November and they may cycle into January and sometimes February (varies for different breeds and in the area of the country). A trained technician or producer can use AI, but practice is needed and the costs compared to the benefits and outcomes (such as profitability) for each farm should be carefully considered. The benefits of artificial insemination, or AI, include:
The producer can make genetic improvement in his/her livestock faster
This procedure reduces the possibility of spreading sexually transmitted diseases between the male and the female
The producer will not have the cost of maintaining a male (except maybe a sterile “teaser” male for heat checking)
The producer can very accurately predict when kids or lambs will be born
Some disadvantages include:
The cost of hiring a technician
The cost of equipment (such as a liquid nitrogen tank)
The buck is better in detecting heat than a person
The success of AI is dependent on:
The appropriate timing of insemination in relation to estrus (heat) and ovulation (release of eggs0
The ability to efficiently collect and cryopreserve (freeze) s***m from quality bucks
The seasonality of goat reproduction
There are two AI methods currently used in the goat industry. The first is cervical insemination that involves deposition of s***m in the cervix through the va**na. The second method is laparoscopic (“surgical”) insemination and involves the use of a laparoscope and manipulating probe to aid in depositing fresh or frozen-thawed s***m directly into the oviduct. Laparoscopic AI is becoming less commonly used because it is more invasive, very expensive (a licensed/certified veterinarian is often needed), it can result in scars that may cause future sterility, and cervical insemination techniques are getting good enough that conception rates are quite similar. Some research is being considered to possibly develop va**nal AI in goats using fresh/chilled semen to make it even easier for producers to use this technology. The advantages to cervical AI include:
Less invasive procedure for AI
More cost-effective and practical for the producer (the producer can learn to do this procedure)
Reduces the likelihood of infection and pain to the doe
Conception rates achieved when using cervical AI range from 50 to 70% with timed AI, and 70-80% with breeding by heat check, though rates with any AI are typically lower during spring and summer months. Photoperiod treatment of bucks during the spring and summer months might assist in alleviating the impacts of season. For classes in your area on cervical AI, contact your local County Extension Office or visit the website of AI trainers such as BIO-Genics, LTD at http://www.biogenicsltd.com (mention of providers names are not endorsement). You can contact your local county extension office for others that might be available in your area. For a video of AI in goats see: http://www.youtube.com/watch?v=vF89Ar83M7g
More information about AI (dairy goats):http://aces.nmsu.edu/pubs/_d/d-704.pdf
Embryo Transfer
Another reproductive technique that can be used following the onset of heat is embryo transfer, or ET. Embryo transfer has been used extensively in beef and dairy cattle for years. In this technique, the doe and ewe are first synchronized and later administered a superovulatory hormone which causes the doe or ewe to ovulate more eggs at one time than usual. This process is called “superovulation.” The eggs are fertilized by means of AI or natural service, and at the appropriate time they are flushed out of the reproductive tract of the donor female and then transferred to recipient females (or frozen for future use). The recipient females (ones to be given the embryo) are also synchronized on the same day as the donor doe or ewe. The advantages of this technology are:
It increases the genetic improvement in a herd or flock significantly since all the genetics can be “new”
It provides an additional source of income (“niche” market) to a producer who has superior breeding stock
Frozen embryos from superior stock can be shipped to other farms to aid in improving the genetics of the goat herds or sheep flocks around the United States
It reduces the spread of sexually transmitted diseases from the male to the females
The disadvantages of ET are:
It is very expensive
The response to the hormone treatments may be erratic
It is hard to find a skilled technician who can perform this procedure in small ruminants
Copper is essential in formation of red blood cells, hair pigmentation, connective tissue and enzymes. It is also important in normal immune system function and nerve conduction. Deficiency symptoms include anemia, bleached looking and rough hair coat, diarrhea and weight loss. Young goats may experience progressive incoordination and paralysis, especially in the rear legs. High dietary molybdenum can depress absorption of copper and cause a deficiency. There should be at least four times as much copper as molybdenum in the diet. Sheep– both hair and wool types — are sensitive to copper toxicity, whereas goats require copper levels similar to beef cattle. Angora goats may be more sensitive to copper toxicity than meat and dairy goats. There are differences in copper requirements for several sheep breeds. This could also be true for meat goats, but no data are available. Although most of the United States has adequate copper levels (Figure 7), many areas have high levels of molybdenum due to soil geology and, therefore, require copper supplementation. The liver stores copper, which can protect against toxicity in the short term. However, when liver capacity is exceeded, animals can die rapidly from a hemolytic crisis caused by stressors such as being chased. The white Savanna goat breed was developed from indigenous goats of South Africa. Various farmers bred what was known as white Boer goats for a number of years in South Africa. One of the advantages of these white goats was the fact that the white color is dominant over most other colors. The other reason is that there is a big demand for white goats for slaughter purposes for various reasons. In 1957, Cilliers and Sons along the Vaal River became the best-known of the originators of this meat goat breed. On the rugged, harsh bush country where temperatures and rainfall can vary to a marked extent, natural selection played a big role in the development of these fertile, easy to care for, heat and drought resistant animals. These goats have thick, pliable skins with short white hair. The Savanna has excellent reproduction, muscular development, good bones and strong legs and hooves. Although these goats have white hair, they are selected for totally black pigmented skin, horns, hooves and all bare skin areas to avoid injury by strong ultra-violet rays. The original Savanna importers in the United States maintained the natural selection development and continued the hardy meat goat breed. They noted that the half Savanna kid got up faster after birth and nursed quicker than their other goats. The Savanna breed is relatively new to the United States, having been imported in the late 1990s. The breed is a large framed, extremely well- muscled goat with white color containing a few black pigments found on the ears. The body characteristics resemble those of the Boer goat. The breed is very adaptable and is successful on extensive grazing, as well as on intensive pastures. The Savanna is not a seasonal breeder, and mating can usually be done at a time that will ensure enough feed is available at kidding. The Savanna goat is a highly fertile and fecund breed, and a high twinning rate is generally achieved, even under less than optimal conditions. Savanna wethers have a good growth rate and are an early- to medium-maturity type that produces carcasses with good confirmation.
