Last update: December 1, 2010 12:34:36 PM E-mail Print

 

PERFORMANCE TESTING -THE ROAD TO FUTURE

ANGORA GOAT BREEDING

 

Gretha Snyman & Buks Olivier

Grootfontein Agricultural Development Institute, P/bag X529, Middelburg (EC), 5900



Within any animal breeding enterprise, it is important that each breeder has a breeding plan. A breeding plan consists of a breeding objective (i.e. a broad aim of what he wishes to achieve with his specific breeding programme), as well as a selection strategy (i.e. how will the set breeding objective be achieved). For example, a breeding objective could be to have an efficiently reproducing ewe flock and to breed bigger rams with good quality fine mohair. Once the breeding objective has been determined, the breeder has to decide which traits should be included in his breeding programme in order to achieve his set objectives. There are a multitude of traits which could be included in a breeding plan for Angora goats. For example : Body weight, fleece weight, fibre diameter, style, character, other subjective fleece traits, number of kids born or weaned and weaning weight of kids.

Selection in practice 

The basis on which all selection is done, is the variation which exists in all traits among individuals in all species. For example, if we look at the body weights of a group of young rams, we shall see that some of them will have below average body weights, other above average and most of them ± average body weights.

In practice, fewer rams than ewes of each progeny group are usually retained for replacement purposes. Therefore, selection of rams can be much more strict than for ewes. Where, for example, only the top 5% rams are selected, only those above average need to be selected. In the case of ewe replacements, it will sometimes be necessary to retain up to 80 % of the young ewes, and in doing so, ewes with below average performance will also be retained in order to maintain flock numbers. In practice, therefore, most selection emphasis is normally placed on rams and they are more strictly selected on traits such as body weight and fleece traits. Ram selection should therefore be focussed on the economically important growth and fleece traits, while ewe selection should be done mainly on reproductive performance.

WHY PERFORMANCE TESTING ? 

The most economically important traits in ram selection are body weight, fleece weight and fibre diameter. Moderately high heritabilities were obtained for these three traits. Furthermore, selection for any of these traits will lead to a correlated increase in the other two traits. In respect of the revised breeding policy of many breeders, namely increasing body weight, decreasing or keeping fibre diameter constant and maintaining fleece weight, these correlations are unfavourable. Selection for increased body weight, for instance, will lead to an unwanted correlated increase in fibre diameter. It is therefore obvious that the only effective way in which body weight could be increased genetically, without increasing fibre diameter simultaneously, would be to measure these traits and incorporate them into a suitable selection index, in order to identify the bigger rams producing finer hair.

Performance testing of rams at second vs. third shearing 

Fleece weight measured at 8 to 9 months of age is not a very accurate predictor of future fleece weights (low repeatability), and most breeders only want to maintain fleece weight. It is therefore proposed that performance testing of body weight and fibre diameter be done at the third shearing or at selection age of young rams, and that fleece weight then be left out of the selection index. The positive genetic correlation between fleece weight and body weight will assure that fleece weight will not decrease if selection is aimed at increasing body weight.

BLUP of breeding values (EBV) 

Owing to their moderately high heritabilities, selection can be done on the individuals own performance, for example indices for own body weight and fibre diameter. However, increased genetic gains in respect of these traits can be achieved if selection is based on BLUP of breeding values. For example, for a trait with a heritability of 0.30 (such as body weight and fibre diameter), selection based on BLUP of breeding value can increase gain by 20%, when compared to selection based on the individuals own performance only.

Advantages of using BLUP breeding values :

* Accuracy of selection is increased because information of all relatives (parents, progeny, half-brothers and -sisters) are included in the estimation of the EBV

* Genetic trends can be obtained and selection progress and efficiency of selection monitored

* Rams born in different years can be genetically compared

* Rams from different breeders can also be genetically compared. Genetic ties between studs is necessary for this to be possible (i.e. more than one breeder make use of the same ram / rams).

PERFORMANCE TESTING FOR INCREASED REPRODUCTIVE PERFORMANCE 

Reproductive rate is the most important trait influencing income. The most expensive mohair is produced by kids and young goats and a high lambing percentage will ensure a large proportion of kid and young goat mohair. A high reproductive rate also contributes to higher selection intensity, i.e. when more young goats are available at selection age, selection could be more strict and genetic progress could be quicker.

Not all of the information required for the accurate identification of superior ewes is available at an early age. Adequate information on the productive performance (growth and fleece traits) is available and accurate selection based on these traits is therefore possible. These traits, however, contribute much less to total lifetime productivity than the ewe's reproductive performance. At this stage little information on the young ewe's reproductive ability is known.

Kidding percentages in excess of 120% under extensive conditions in Angora goats lead to the production of a large number of kids, but the viability and survival rate of these kids are in many instances very poor. The aim should therefore be to ensure that each ewe produces a viable kid at weaning, in order to enable it to grow up strong and healthy. Furthermore, in view of the limited natural resources, an increase in number of kids born per ewe joined is not the sole answer to generate higher income. Selection for litter size, without taking the weaning weight of the individual kids into consideration, would therefore be short sighted. Total weight of kid weaned is determined by litter size, as well as other factors, such as mothering ability, milk production of the ewe and growth potential of the kid. Total weight of kid weaned per ewe (TWW) should therefore be the main breeding objective in the ewe flock.

The results of various studies on small stock indicate that there is large variation in total weight of lamb weaned, regardless of the reproductive rate of the flock. This variation could be utilized and below average reproducers could be culled. In doing so, the average performance of the flock should increase (See Table 1).

Table 1. Reproduction of Angora ewes in the Jansenville flock which were mated four times (no selection for reproduction was done) 

 

Poorest 10

Best 10

Kids born / ewe

2.2

5.7

Kids weaned / ewe

0.8

5.2

Kg Kids weaned / ewe

11.1

93.4

Income from hair (R/ewe)

R144-00

R936-00

Two-tooth body weight of ewe

24.7

31.9

Two-tooth hair production of ewe

2.49

2.43

Income from hair = Calculated as 2 kid shearings for each kid weaned @ R60-00 per shearing.

At selection age, total weight of kid weaned by the young ewe’s dam is the best predictor of lifetime reproduction of the young ewe. It is therefore recommended that ewe selection should take place in two phases.

In the first phase, young ewes could be assessed subjectively for breed standards and conformation or fleece faults. Preliminary selection on the basis of body weight could then be done. If preferred, one of the selection indices recommended for Angora ram selection could be used. Each breeder or commercial producer should decide which selection strategy is most suitable for his specific circumstances and requirements. As the production traits contribute much less to total productivity than the ewe's lifetime reproductive performance, more than the required number of young replacement ewes should be selected during the first phase. These ewes should then be mated and final selection (second phase) could be done after their first parity.

Table 2. Reproduction of young ewes at first and consequent parities 

Kid born in Year 1

Kid weaned over 4 parities

Total kg kids weaned over 4 parities

Two-tooth body weight of ewe (kg)

Two-tooth fleece weight of ewe (kg)

0

2.00

32.8

27.5

2.46

1

3.21

53.0

29.1

2.49

2

4.24

65.5

29.5

2.40

 

With the second phase of ewe selection, selection could be done by culling young ewes that fail to wean a kid or produce below average TWW. Selection intensity at this phase is dependent upon several factors. The most important of these are the prevailing environmental conditions especially during mating, but also pregnancy and lactation. In extremely poor years it would be advisable to leave final selection of young ewes till after their second parity.

Selection of rams for reproduction 

Rams from above average dams with regard to reproduction should be selected. When BLUP breeding values for TWW become available, rams could also be selected on breeding values for TWW. As discussed elsewhere, TWW would increase due to a positive genetic correlation with body weight, if selection is based on any of the recommended selection indices. As far as selection for improved reproduction in rams is concerned, it would therefore suffice for the present to accommodate it through indirect selection on body weight.

 

WHAT THE BREEDER HAS TO DO 

Selection for improved efficiency can only be done if sufficient records are kept and if they are correctly applied. In order to achieve this, the Animal Improvement Institute of the ARC, in collaboration with breeders and personnel at the Grootfontein ADI, developed a performance testing scheme for Angora goats. The purpose of this scheme is to supply information necessary for accurate selection to breeders and commercial farmers. In short, the scheme operates as follows (See also Table 3) :

1. Register as participant to the performance testing scheme. Registration forms are available from Dr Buks Olivier, ARC:AII, P/Bag X529, Middelburg (EC), 5900. Each registered member will be visited by people from Grootfontein to explain everything, determine each breeder’s breeding objective (i.e. what selection index he wants to use) and sort out any problems.

2. At mating - Keep a list of all ewes in the stud / flock that are put to the rams. If you want to make use of BLUP breeding values in future, you would have to know which ewe was mated to which ram. This is already being done by stud breeders.

3. At kidding time - Identify and tag each kid and identify its dam. Record birth date with-in the scope of one week. Record birth status and sex of the kid. This is also already being done by stud breeders.

4. Members of the Angora Goat Stud Breeders’ Society : Sending in kid returns to Angora office in Jansenville - Send in the usual information, together with the complete mating list, i.e. all ewes that are still in the flock, whether they lambed or not. This information is needed for the calculation of ewe productivity.

5. At weaning - Record weaning date, weaning weight, as well as the group in which the kid was raised (twin ewes, veld, pasture, etc.).

6. Members of the Angora Goat Stud Breeders’ Society : The Office will send you a form with the dam-ID, sire-ID, kidding date, kid-ID, birth status and sex of the kid. There will be space on the form to fill in weaning weight, date when weaning weight is recorded, as well as space for various environmental codes, for example natural veld, feedlots, etc. Enter the information recorded at weaning onto this form received from the Office and send it to Grootfontein at the above mentioned address to obtain ewe productivity results.

7. Other participants : You will obtain forms on which to fill in the recorded data from the above-mentioned address at Grootfontein. Enter the information recorded at weaning onto this form and return it to Grootfontein to obtain ewe productivity results.

8. Members of the Angora Goat Stud Breeders’ Society : The Office will send you another form with the kid-ID’s, as well as all relevant information on the kids. There will be space on this form to fill in the raw data recorded at shearing (body weight, fleece weight, shearing date and all relevant environmental codes). Other participants will receive these forms from Grootfontein.

9. At second shearing - If preferred, the following could be recorded for ram kids:

                                * Body weight

                                * Fleece weight

                                * Score for style & character and evenness of fleece (optional)

                                * Take midrib fleece sample (±70 g) for determination of fibre diameter

Complete the shearing data form and send it along with the fleece sample to Grootfontein.

10. At selection age of rams / before third shearing - The following should be recorded for young rams:

                                * Body weight

                                * Score for style & character and evenness of fleece (optional)

                                * Take midrib fleece sample (±70 g) for determination of fibre diameter

Complete the shearing data form and send it along with the fleece sample to Grootfontein.

11. At the third shearing - The following should be recorded for young ewes:

                                * Body weight

                                * Fleece weight

                                * Score for style & character and evenness of fleece (optional)

                                * Take midrib fleece sample (±70 g) for determination of fibre diameter

Complete the shearing data form and send it along with the fleece sample to Grootfontein.

12. Due to the fact that fleece weight of rams is not available at the third shearing, it would be good if the same measurements as for the ewes could be taken for the kapaters. This would ensure that more accurate breeding values for all animals could be estimated.

13. If you are making use of the Angora program on your farm, everything will be much more easier. Firstly, you have to enter your raw data (weaning weight, body weight, fleece weight, etc.) into the computer. Then there will be an option in the program where you could print out the necessary forms which have to be send to Grootfontein along with the fleece samples.

14. Once these records have been gathered, the selection of breeding parents can be based on one of the available selection indices.

OUTPUTS RECEIVED 

Ewe productivity report

If weaning weights and dam ID’s have been send to Grootfontein, you will receive a ewe productivity report. The following will be given for each ewe in this report:

* Age at first lambing

* Number of times the ewe kidded

* Number of kids born and weaned

* Ewe production index

* Weaning weight index for each recorded kid

Fleece data report

After completion of the fleece analysis, you will receive a fleece summary report. In this report, indices for body weight, fleece weight and fibre diameter will be summarised for each animal. The animals will also be ranked according to the breeder’s own selection index. If sire ID’s are available, a sire summary for all recorded traits will also be supplied.

COSTS INVOLVED 

The cost for participation in the scheme is as follows :

Annual fee : R98-00

For each weaning weight record : R 0-39

Analysis of fleece samples : R 4-40 per sample for < 50 samples

: R 4-00 per sample for 51 - 199 samples

: R 3-60 per sample for 200+ samples

: Additional R 0-85 per sample

All prices exclude VAT.

For a ewe flock of 200 ewes, the total cost amounts to ± R4-28 per ewe. Fleece sample analysis contributes 65% of this total cost.

Enquiries 

All enquiries can be addressed to Dr. Buks Olivier (Tel no. 04924-22563) or Dr. Gretha Snyman (Tel no. 04924-21113) at Grootfontein.

 

Table 3. Actions required by breeders to obtain ewe productivity and fleece data reports

Action required to obtain specific report

Ewe Productivity Report

Report on Performance testing of body weight and fleece traits

BLUP-EBV’s for all recorded traits

Mating list (only ewe ID’s)

x

 

 

Mating list (ewe ram ID’s)

 

 

x

Kid ID

x

x

x

Birth date

x

 

x

Sex and birth status of kid

x

x

x

Weaning weight

Weaning date

x

 

x

Body weight & Fleece weight at second or third shearing

 

x

x