August/September 2003 Health

August/September 2003

Goal Setting

It is extremely important for breeders to have goals in a breeding program. Too many times no thought is given in a breeding program or the trial and error method is used and therefore one can never claim success. What makes a good goal? It must be concise; it must be obtainable; and it must be measurable. One might say, "I want to raise big sheep" or "I want to raise meaty wethers". Are these good goals? No. Why? They are not concise. They don't define what big is or what meaty is to the point that they can be accurately measured.

It would be much better to define one’s breeding goal as, "I want to raise Suffolk yearling rams that are 42 inches tall and weight 450 lbs" or "I want to raise lambs that have a 5 square inch loin eye and a leg score of 15 (when evaluated 1-15) when they weigh 130 lbs. These two goals are concise, they can be achieved and, most importantly, they refer to measurable traits. Only when goals are sound will one be able to design a breeding program that is successful. It's not enough to want to have a goal of winning a county or State Fair, or a National Show at Sedalia or Louisville. One needs to know what steps it takes to develop a phenotype (how the animal looks) in a very specific manner in order to assemble a breeding and selection program to achieve a phenotypic goal. All breeders do not need to have the same goals. In fact, this would not be good because all flocks would tend to have similar gene pools and no variation in phenotype would exist.

Selecting Goals for a Breeding Program

There are several options to consider when developing goals for breeding.

(1) FLOCKS INTENDED FOR ENTERTAINMENT

There are many sheep flocks (generally small flocks) that are not designed with profit in mind. These flocks, often known as hobby flocks, are not driven by the need to make a profit, but are more intended to satisfy the owner through other means. They many be used to keep a small acreage of grass mowed and clean or to provide entertainment for the family. They may be used to teach responsibility to the young people in the family through 4-H/FFA projects. These flocks fulfill needs other than producing stud sheep and therefore are unlikely to make a significant contribution to improving the gene pool of the Suffolk breed.

Goals for this group of sheep owners may be centered around management rather than genetic improvement. This is fine but will not be discussed in these articles.

(2) Flocks managed to produce profit

Sheep flocks which are managed with profit as a primary goal generally are larger than hobby flocks and success with such flocks is measured in terms of dollars. These flocks could well have an impact on the gene pool of the Suffolk breed (for good or for bad).

(3) Flocks managed to improve desired traits and be profitable

It is this type of flock with which these articles will be concerned. The concepts discussed can be applicable regardless of the owner's motivation.

These breeders must have answers for the following questions as they develop their goals: (a) What market am I producing sheep to serve? (commercial rams, frame sheep stud, wether sire and dam stud, wether market, etc.) (b) Is the market local or national? The type of sheep that satisfies the local market may not be the same type that meets the demands of a national market.

Setting goals for a breeding program is not an easy process. In fact, few breeders can precisely define the goals of their own operation.

When setting goals it is import to select traits that are quantitative (objective) in nature. That is, goals must involve traits that can be accurately measured. Examples of such traits include weight per day of age, yearling weight, height, girth measurement, average daily gain, etc. While these traits may be controlled by many different genes, they can be accurately measured (that is by a scale or tape measure).

It is much harder to select for qualitative traits which are subjective in nature. Examples of qualitative traits might include breed character, pattern, structural correctness, soundness, etc. All of these traits are important to phenotype but they are hard to select for within a breeding program for two reasons: (1) They are influenced by many genes and (2) they are subjective, meaning that what one person may call a sound sheep another might not, or what is good breed character for one breeder is not so good for another. This is precisely why the show ring winner does not always breed true. It's one person's choice on a given day and is based completely on phenotype. This will be discussed at greater length in other sections.

Influencing Phenotype

Two major components influence phenotype, environment and genotype. A simple formula is:

Environment + Genotype = Phenotype

Why is this so important? The environment sheep are raised in has greater influence than genotype on heritability.

Traits can be grouped into three different categories: reproductive traits, which are low in heritability, (5-20 percent heritable), production traits, which are medium in heritability (20-35 percent heritable) and carcass traits, which are high in heritability (35-55 percent heritable).

What does this mean? Well, in the case of ewe fertility the heritability rate is 5 percent. When applied to the formula we find that 95 percent of ewe fertility, influencing lambing rate, is due to the environment which she is exposed. That is why researchers suggest feeding ewes to put them in a gaining state before breeding. This increases lambing rate approximately 10 percent.

On the other end of the spectrum, loin eye area is about 50 percent heritable. Therefore, 50 percent of loin eye area is due to environment. For the life of me, I have never understood why some feeders limit feed lambs. It only reduces the genetic potential of a lamb to express loin eye size. The environment in which a sheep is raised will determine the extent to which genes can express themselves. It only reduces the genetic potential of a lamb to express loin eye size. The environment in which a sheep is raised will determine the extent to which genes can express themselves. Environment can limit or enhance gene expression. One must remember that these concepts are why good feeders and good fitters have such great success masking the genotype of show animals. This is an extremely important concept to understand when you are selecting a stud (ewe or ram) to go into your breeding program. Knowing something about flock management and parents of individuals is far more important than show ring winnings when it comes to making progress in improving phenotype of your flock. By the same token it is extremely important to manage (that is feeding, housing, etc.) sheep in such a manner that the genotype can be expressed phenotypically.

With that in mind, in the next article we will discuss how genes express themselves and try to explain some of the complexities associated with trying to make progress breeding your ideal Suffolk.