Survival of the Fittest
Lincoln University, 8th April 2005
by Kerry Dunlop

Breeding for better survival

I have always believed in the survival of the fittest. For this reason the sheep at The Gree have been bred under commercial conditions. No preference has been given to the SIL recorded ewes that comprise 40 % of the flock of 2500 ewes. Clients, some who have been using The Gree rams for the last thirty years, farm from intensive flat land to hard hill country in the South Island.

Breeding for Survival

• This presentation will describe the genetic changes of crossbred sheep that have been made in the last thirty years.
• Mostly this has been in response to the change in economic circumstances and the need for “easy care” sheep. It has been effective because of the development of superior performance recording schemes such as SIL.
• The importing of new breeds has given the sheep industry new options.
• I will highlight the fact that crossbreeding can significantly increase the survival of lambs to weaning.
• Selection within a breed for increased survival is slow due to the low inheritance of this trait.
• If you have a vigorous prolific sheep flock, the major gains are most likely to come from attention to management practices, which is not the brief of this presentation.
  The theme for today is the survival of the fittest. You as a commercial farmer have to decide what is the optimum lambing percentage for your farm situation. You have a number of options that influence the outcome.

Basic Principles

I would like to highlight three basic principles.

1. The inheritance of survival is very low.
   A lamb’s survival has much more to do with management and environmental circumstances than it has to do with genetics.
2. Crossbreeding purebred sheep has the greatest impact to improve lamb survival.
   For example mating a Romney ewe to a Cheviot, Border Leicester or East Friesian ram.
3. To make progress to breed for better survival a large population of sheep are necessary. This applies to any lowly inherited trait.
   To explain this I will give you:
   1. A brief history of the sheep-breeding programme at The Gree.
   2. Then I will describe the present situation with Greeline composite sheep.
   3. I will explain why have I stopped breeding Romney and Coopworth sheep.
   4. Finally some comments about the future options, which will help to improve lamb survival.

History of sheep-breeding

1. History of sheep breeding at The Gree

The Gree is a 270 hectare flat to slightly rolling intensive sheep property. It is situated 18 kms north of Winton in Southland. Sheep wintered comprise 2500 ewes, 650 ewe hoggets, 200 ram hoggets and some 20 hectares of barley is grown.

In 1964 I began screening Romney 2th ewes which weaned a good set of twins.

This was my response to the high labour input at lambing. In those days, each morning during lambing, a number of ewes required assistance. This was often to deliver lambs with swollen heads or dystokia. If they were alive they were reluctant to drink. Dopey devils.

A significant number of ewes were unable to feed their lambs. This was due to dropped udders, inappropriate teat placement or simply large teats. The ewes because of stress through difficult lambing lost their mothering instinct and wandered off. The result was often mismothered and starved lambs.

This scenario came about largely as a result of high wool prices, which had prevailed, in the previous decade. So called “top” stud rams were those that won prizes at the show and subsequently made very high prices at public auctions. These sheep were made to look the part. They had heavy bone and “excellent constitution”. Genetically they were a disaster.

2. Group breeding and “easy care”

The response to this was the establishing of group breeding schemes.

In 1968 I sent a group of 4th ewes, which had weaned consecutive twins, to the central flock of the NZ Romney Development Group which was located in Hawkes Bay. In return top performance recorded rams came back to The Gree.

The objective of the NZRDG was to breed clear faced prolific easy care Romney sheep.

This was the first large-scale sheep group-breeding scheme in the world. We had 20 members from the Waikato to Southland. There was a base of more than 100,000 ewes. We were well advised by scientists such as Prof Al Rae from Massey University and we had the support of the Ministry of Agriculture and their new computer performance-recording programme.

Along with other sheep group breeding schemes and the development of the Coopworth and Perendale during the 1960s and 70s the NZ sheep industry had available to it more productive “easy care” sheep.

No doubt many of you here today have benefited from the improved genetics, which began thirty years ago.

3. Coopworth concept

I have already mentioned that crossbreeding is a most effective way to increase productivity and with it improve lamb survival.

In the 1960s Prof Ian Coop from Lincoln University showed us that with selection for productive traits the loss of hybrid vigour from the Border Leicester Romney F1 or first cross could be offset by the F3 generation. It can subsequently be built on. Today the Coopworth breed is a popular productive sheep.

I used my first Coopworth ram in 1969 and became a member of the Apex Coopworth Syndicate in 1972.

Greeline Composite Sheep

Composite sheep, are defined as sheep which contain three or more breeds. Composite sheep have become popular with sheep farmers in New Zealand in recent years.

Greeline Composite Sheep

The Greeline is a genetic package which at this stage is comprised of ¼ East Friesian, 3/8 Texel, 3/8Coopworth.

It has been developed using the “Coopworth concept” principle to interbreed for improved meat production.

To maintain a significant population of sheep to select from two other SIL recorded flocks are participating. Referencing by exchanging rams with other breeders who have a similar genetic package is also minimising any risk of inbreeding.

The main reasons for this change are:

1. The emphasis has to be on meat. It is no longer appropriate to breed a dual-purpose sheep when crossbred wool for some years now has become a by-product.
2. It is necessary to lamb ewe hoggets which can wean good twins.
   In twelve months the wool from a hogget will net not much more than $12.00.
   If one lamb is weaned the return is at least $60.00 and two lambs will make $120.00.
3. Ewes should be able to wean triplets.
4. Meat yield will be the basis for payment in the near future.
5. Competition for land use forces us to increase productivity.

There are many options of composite sheep available today but I am going to review of the breeds that comprise the Greeline Composite.

½ East Friesian ½ Coopworth

Seventeen EF sires have been evaluated at The Gree by mating them to Coopworth ewes.

The ½ EF ½ Coopworth lambs showed considerable hybrid vigour. They had more than 90% survival and weaned 15% heavier than the Coopworth lambs.

As ewe hoggets the 1/2 EF1/2 Coopworth scanned 145% on average. As 2th ewes there has been a wide variation between sire groups. Some had no advantage over the Coopworth at 190%. The best sire group have scanned at 280% as 2th ewes.

This is now reflected in last years lambing when the mixed aged 1/2EF ewes reared 232% lambs with 88% survival.

Positives: Superior milk production, prolific & precocious, sound feet, good mouths, very good udders and teat placement, minimal dagging and acceptable wool.

Negative: deficient carcase, too lean and can be flighty.

Texel

Positive: excellent lean carcase, hardy, good mothers, minimal dagging

These negative comments apply when released from quarantine in 1992

Negative: difficult and slow to lamb, poorly shaped feet and prone to scald, black fibre, variable wool quality and some strains low prolificacy.

Coopworth

Coopworth: A great base from which to build a composite.

The Greeline Composite, 1/4EF,3/8Texel,3/8Coopworth gives sheep farmers a simple option to lift the productivity of their sheep where the emphasis is on meat production. The positives of each parent breed have been selected.

Survival. The selection of any stud ram at The Gree is made only after the dam’s and grand dam’s lifetime records for lambs weaned have been checked. All lamb losses are recorded. The causes could be due to abortion, adverse weather or accident such as smothered by the dam or drowned. The deaths are coded as to whether they died at birth or later.

Some lambs which are tagged simply don’t appear at weaning.

An attempt is made to determine if the death is the ewes or lambs fault or other.

It is only by tagging lambs at birth that these and many other observations can be made.

For the past five years I have been tagging lambs from ewes, which have had, the single scanned sheep removed. This has given me experience with lambing at 250 % of lambs or better.

The main causes of death have changed significantly from the old Romney, which I described earlier in this presentation. The experience I have had with lambing ewes with triplets highlights the chance of a breech birth or two lambs jammed together. Neither of these problems appear to be either repeatable in future years, nor are they heritable. The other problem with triplets are lambs that become mismothered and then die from starvation.

On average at The Gree 85 % of lambs born as twins or triplets are expected to survive to weaning. Of the 15 % of lambs that don’t make it, about 50 % die after they have been tagged. My aim is to consistently achieve 90 % survival with a lamb drop of 200 %.

Resistance to disease. A healthy animal that has had the appropriate protection from vaccination is least likely to succumb to disease.

Footrot. Where footrot is a significant problem breeding for resistance has brought worthwhile progress especially in the fine wool breeds. I have always given a priority to ensuring that feet are structurally sound and I cull animals that are most vulnerable to scald.

Parasite resistant sheep are desirable. Some sheep breeders have made progress with this objective. There is scientific debate as to whether resistance or resilience is the best approach. The emphasis at The Gree has been to breed resilient sheep. That is to have sheep that can be highly productive in spite of a parasite challenge. This means that lambs are only drenched for parasites after a faecal test is made. The aim is to encourage the natural immune system to kick in as early as possible so that no drenching is necessary after twelve months of age.

Future options to enhance lamb survival.
To decide the best option for your farm there are some basic facts, which should be understood.

Graph, with acknowledgement to John McEwan & Peter Amer, Agresearch, Invermay

As scanning % increases the proportion of ewes producing singles, twins and triplets change.

This graph shows this clearly. The percentage of ewes that produce twins peaks at about 66 % at.170 % pregnancy scanning.

I recommend that you read in last months March 2005 Country-wide publication an article written by Gerard Hall that reports John McEwan with the headline “ A higher lambing % may not always be the best”.

Table, with acknowledgement to John McEwan & Peter Amer, Agresearch, Invermay

The birth rank of a lamb has a major influence on its chance of survival.

The following table shows the % survival rates of birth to weaning by birth rank on different classes of farm. In green is the percentage of lambs reared in each situation.

The main point here is that more lambs born doesn’t necessarily mean more lambs weaned. In the table above triplets on hard hill country wean 120 % lambs reared compared to twins in the same environment that wean 140 % ( in red )

As pregnancy scanning reaches 200% about 20% of the ewes will carry triplets.

To successfully harvest the lamb crop at this level of prolificacy requires a change in mind set.

The management of ewes with triplets is another topic and many aspects will have been covered here today.

Summary

1. Significant change has occurred in the last thirty years when it comes to breeding for survival.

Easy care sheep have been bred which require minimal assistance at lambing.

2. The problem of difficult single births and dopey lambs has been replaced by the problems associated with ewes producing triplets.

3. I find that it is still difficult to achieve above a ninety percent survival to weaning when the ewes scan better than 200 % of lambs. At this level about 20 % of the ewes produce triplets.

4. Provided the ewes are capable of producing adequate milk, that they have good udders and teat placement and that they have good mothering instinct, I believe that at this level of production most progress can now be made with improved management.

5. Finally, hope for good weather at lambing.