Selecting for HARDY Angora goats
By Dr Mackie Hobson BSc(Agric),BVSc

1. Reproduction

There are farmers who are now considering using genotyping to select for the ‘hardy gene’ in their Angora goats. The current cost  for DNA isolation and genotyping would suggest selection on the sire side may be cost effective.

Cold stress related deaths were implicated to a dysfunction in the adrenal cortex. It is the normal reaction of a goat when under stress (cold stress) to produce cortisol (a steroid hormone). The reason that cortisol is so critical is that the glucose requirement of a cold goats is 66% higher than goats under normal conditions. A lack of glucose results in a drop of the goat’s body temperature, heart function so resulting in possible death.

The chief role of cortisol is:

• Produce a high energy fuel (glucose) and reduce all other metabolic activity not related to this.

Through studying the Angora goat’s adrenal steroidogenic pathway, it was demonstrated that the cause of the observed hypo-cortisolism lies with a single steroidogenic enzyme CYP17. (Storbeck et al., 2007; Storbeck et al., 2008; Storbeck et al., 2009).

3 genotypes H0,  He and  Hu differed in the CYP 17 gene. (He having significantly more Cortisol ).

• Selecting for He in trials indicated that it does not have a negative effect on mohair production or quality.

What are the the 3 genes?

1. H0 : Only one CYP17 gene

• Lowest cortisol producer
• Poorest reproduction (62% poor reproducers)

2. He: Both CYP17 genes

• Highest Cortisol
• Same quantity and quality of mohair
• Reproduction (42% poor reproducers) – Similar to Hu

3. Hu: CROSS between He + H0

• Worst for cold
• Reproduction ( 35% poor reproducers) similar to He.
• Middle for cortisol

Trials by  M.A. Snyman,  K-H. Storbeck & P. Swart when exposing Angora goats to cold stress noted significant differences in rectal temperature were recorded among the three genotypes.

• The Hu animals had lower rectal temperatures than the He and Ho animals , which did not differ from each other.
• At 150 minutes, the first Hu goat had to be removed from the trial as its rectal temperature dropped below 32 °C. At 180 minutes a second Hu goat had to be removed and revived, while at the end of the trial, three more Hu goats whose rectal temperatures dropped below 32 °C had to be revived. None of the He or Ho goats had to be removed from the trial due to a rectal temperature dropping below 32 °C.

Why has the lack of cortisol production occurred in the Angora goat?

• A negative relationship between hair and cortisol production. Producers have inadvertently selected for hypo-adrenocorticsm (low cortisol production)

Are there any concerns about selecting for the hardy gene and reducing hair production? 

• Production data was gathered from fine hair goats kept at the Jansenville Experimental Station born between 2000 and 2008. Statistical analysis revealed that there is no significant difference in the production data among the genotypes. Therefore, selection for more hardy goats based on the CYP17 genotype should not adversely affect the quality or quantity of mohair produced.
• CYP17 is also vital to the production of sex steroids by the gonads As these hormones play a critical role in determining the reproductive characteristics of the animal. Trials have determined that was no significant differenced in testosterone levels between rams of the different genotypes and CYP 17 had no effect on the reproductive fitness of rams.

What genes are currently out there?

Presence of the Hardy gene in the Veld rams 2013 and 2014

The distribution of the 3 genotypes in the veld rams in 2013 (blue) and 2014 (red) reflect the distribution of the genotype in other flocks (green) checked in  previousst studies.

Does the hardy gene have any influence on internal parasites?

A study was done to Rank the Veld rams for resistance to internal parasites by SAMGA in 2014.

These rams were then compared to the prevalence of the hardy gene in the top 50% of resistant goats.

• The results suggest there is unlikely to be a link between the hardy gene and internal parasites

Graph : The prevalence of 50% of each of the 3 genes in the top 50% worm resistant rams.

Breeding hardy Angora goats

If a He ram is identified and used in breeding then the initial offspring possibilities initially include.

Therefore in a breeding program where sires where selected for the hardy gene it would not take long to breed a hardy flock of Angora goats.

How can farmers proceed?

The way forward for breeders interested in incorporating the CYP17 genotype into their selection strategy,

1. It is recommended that all Ho genotype rams could be culled as a first step. Preferably only He sires should be used.
2. As the Hu genotype is in abundance in the population, it would be unfeasible to cull possible Hu sires with desirable production characteristics. These sires should, however, only be mated to He genotype ewes. Mating of Hu sires to Ho ewes would yield 50% Ho and 50% Hu progeny, while a mating between a Hu sire and Hu ewes will yield 25% Ho, 50% Hu and 25% He progeny. It is not possible to get rid of the ACS- gene, as all the animals possess this gene. An effort can, however, be made to get rid of the animals that does not have the ACS+ gene (the Ho genotype), thereby increasing the frequency of the ACS+ gene in the population.

For farmers who wish to genotype their rams, blood samples should be collected and send to Stellenbosch University for genotyping. The genotyping cost is estimated to be between R250 and R300 per sample, for a minimum of 50 samples. Arrange beforehand with Dr Karl Storbeck (storbeck@sun.ac.za) when you plan to genotype the animals.

Protocol for blood sampling:

1.Ask a veterinarian to assist with the collection of blood samples.

Blood samples should be collected from the left jugular vein of the animals into 10 ml EDTA plastic vacutainer blood collection tubes. A new, sterile needle should be used for each animal.

2. The blood collection tube should be labelled with the date and an identity number of the ram before collecting the blood sample. After blood collection, the tube should be rotated a few times to make sure that the blood is mixed with the anticoagulant in the blood collection tube.
3. Collected blood samples should be stored on ice directly after sampling and while being transported to the laboratory. Please try to send samples off as soon as possible after sampling, to ensure that high quality DNA can be obtained from the blood samples.
4. Blood samples should be sent Attention: Dr Karl Storbeck Department of Biochemistry JC Smuts Building Van der Byl street Stellenbosch 7600 Email: storbeck@sun.ac.za Office: 021 808 5884

Dr Mackie Hobson

SAMGA Vet

REFERENCES

• A REVIEW OF THE ROLE OF CYTOCHROME P450 17-HYDROXYLASE/17,20 LYASE (CYP17) IN HYPOCORTISOLISM IN SOUTH AFRICAN ANGORA GOATS

1. Storbeck1, M.A. Snyman2 & P. Swart1#

• HYSIOLOGICAL PARAMETERS OF THREE SOUTH AFRICAN ANGORA GOAT CYP17 GENOTYPES SUBJECTED TO COLD STRESS .M.A. Snyman1#, K-H. Storbeck2 & P. Swart2.1 Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg (EC), 5900.2 Department of Biochemistry, University of Stellenbosch, Private Bag X1, Matieland, 7602 University of Stellenbosch, Grootfontein Agricultural Development Institute

• Wentzel et al., 1979). Fourie (1984)
• Van Rensburg (1971)
• Herselman & Van Loggerenberg (1995)
• Payne & Hales, 2004.
• SAMGA trial worm resistance and the ‘hardy gene’. 2014
• A. Snyman# & M. van Heerden