Is supplementing Selenium (Se) in Angora goats justified?

1. Nutrition

Angora goat farmers often ask me whether supplementing Selenium (Se) is cost effective?

To answer this question we have to look at the different Angora goat farming systems and look at what trial and field work has been conducted in the past.

Firstly we know that Se deficiencies occur under certain conditions.

• Lush pastures,
• Sandy and acid soils with low clay content.
• When high grain/pellet diets are supplemented.

Lucern lands form an important part of Angora goat production on many farms and may result in reduced Selinium (Se) levels.  Lucern contains high dietary levels of  Calcium (Ca) and Sulpher (S). High Ca and S reduce Selenium (Se), Manganese (Mn) and Magnesium (Mg) absorption by the goat.

However under extensive Karoo veld conditions deficiencies are less likely to occur. Karoo shrubs are noted for their relatively high nutritive value. Unlike grasses, shrubs maintain their feeding value throughout the year, with minimal variation. To show that this is the case studies have been conducted on Springbok which are intermediate feeders with a similar dietary intake to Angora goats on the same veld. The studies ( J.B.J. van Ryssen and J.H. Hoon) used Springbok in the Karoo to check for  copper (Cu), selenium (Se) and manganese (Mn) levels.

This study confirmed that in the Karoo region

• It is unlikely that Angora goats would suffer from a Cu or Se deficiencies under extensive conditions. This study was in agreement with the map published by Bath (1979) and supporting the Se map published by Van Ryssen (2001).

It is however important to realise that each farm may be different and camps within a farm may vary due to differences in soil types.

What clinical signs occur in Selenium deficiency?

• The most important economic effect in young goats is the slow growth and poor production.
• In severe cases of deficiency it is possible to develop congenital white muscle disease. Kids may be born dead or die after birth as the kid is unable to suckle. Diagnosis can be made of histopathology samples of the heart muscle which may be streaked with calcified deposits. The muscles may look like cooked chicken meat.
• Delayed white muscle disease is possible under severe deficiencies where clinical signs may be seen at about 2-6 weeks of age. Walk with stiff gait, arched back and nervous signs can be seen before death.
• Reduced reproduction due to embryonic death 3-4 weeks after conception
• Deficiency may result in reduced immunity

How can a Selenium deficiency be diagnosed?

Selenium levels in soil, plants and animals in the same location show a close relationship.

The liver and blood samples are usually used to determine Se levels.

Is it justified to give Se supplements?

A number of trials have been conducted using Se as a supplement (some in conjunction with other minerals)

1. Effects of selenium supplementation on the growth rate, mohair production of Angora goat kids (J. J. Wichtel , K. G. Thompson , A. L. Craigie & N. B. Williamson)

The concentrations of Se  in the lucerne diet were 0.02 mg/kg dry matter (DM). Supplementary Se enhanced

• live weight gain by 26% during the final month of the study;
• However mohair growth was not affected.

2. Trace mineral supplementation of sheep and Angora goats in the different grazing areas of South Africa (J.H. Hoon and M.J. Herselman).

This project was carried out at 20 localities (13 sheep and 7 Angora goats) in the small stock producing areas of South Africa. The ewes of the treatment group received a 1 ml subcutaneous injection of a commercial trace mineral supplement containing Zn, Mn and Se (Multimin® - Virbac) 4-6 weeks prior to mating and again 4-6 weeks before lambing/kidding.   From the results it appeared that

• supplementation of Zn, Mn and Se by means of a commercial product had in general a positive effect on the measured reproduction traits of sheep and Angora ewes and the production traits of their lambs/kids, although differences were relatively small at most localities.
• It also indicated that an increase of 0.4-0.5% in the weaning percentages of Angora goats and
• 7-0.8% in the weaning percentages of sheep was sufficient to cover the cost of the supplementation.

3. Trials by a manufacturer of a commercial mineral supplement (Multimin) suggested an increase in Angora goats:

• in pregnancy by 0.7%,
• Kidding by 1.1%
• Weaning by 4.6% .

4. The influence of trace mineral supplementation on the reproduction of sheep and goats in the different production areas of South Africa. (JH Hoon & PG Marais).

In this study, a commercially manufactured product consisting of a combination of chelated Zn and Mn, as well as Se in the form of sodium selenite, is used. The study was carried out on the farms of 23 participants (15 sheep and 8 goat farmers), using their own animals. Treatment 4-6 weeks before mating and the animals of the treatment group received a subcutaneous injection of 1 ml of the trace mineral supplement. Ewes were mated as one group, scanned for pregnancy and the treatment group received another trace mineral injection 4-6 weeks before lambing.

Preliminary results indicate

• Very small or no differences with regard to scanning percentages between the control and treatment groups at most of the localities.
• In some areas, where shortages of certain trace minerals are common, supplementation increased the conception rate and fecundity of the ewes.
• The high rainfall that occurred in most of the summer rainfall areas during the mating season, with the resulting good grazing conditions, probably contributed to the small differences observed between the two groups at most of the localities

5. The effect of frequency of mineral and Vitamin supplementation on semen quality of Angora goat sires.(A. Baca, A. Snyman & E. Kilian)

Selenium and Vitamin E play a biological role as cell antioxidant by preventing damage by oxygen and various peroxides formed from fatty acids (Smith & Akinbamijo, 2000, Cheah & Yang, 2011). Selenium is also required for the accurate formation of the midpiece and flagella (Cheah & Yang, 2011).  The study concluded:

• Although supplementing at six or eight week intervals yield better results in terms of semen density and motility, there were no consistent differences in the frequency of supplementation of vitamins (A, D, and E) and trace minerals to Angora rams on testes traits or semen quality.

From these trials it can be concluded that due to the relative low cost of Selenium supplementation the use under normal extensive karoo conditions, although small, may be justified particularly 4-6 weeks before kidding.

It is under intensive conditions where Lucerne lands are used is where supplementation is advised

Methods of supplementation

The most common methods of supplementing Se used by Angora goat farmers:

1. Oral/Drench: This is a cheap and safe way of supplementing Se. A single dose usually provides adequate supplementation for 1-3 months.
2. Subcutaneous injection: The safety level is less in injections than using the oral form.

See our website for some supplement options:

https://www.angoras.co.za/article/list-of-mineral-and-vitamin-supplements#171

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Dr Mackie Hobson