Herd Sires

[mikey]

Choosing a Herd Sire
Form Follows Function

By Nancy Nickel 


The purchase of a herd sire is the manifestation of a vision for every dairy goat owner. It is a concrete and positive step in the direction of a herd's future, and the continued enjoyment of one's goat keeping endeavors. More than "half a herd," he is the future.

The decision to purchase a herd sire is carefully considered at Nickel's Dairy Goats, Clark, Missouri. We first list the traits we believe our herd exemplifies and consider only genetics that will enable us to maintain our genetic advantage. Just as corporations and businesses maintain a mission statement for guidelines and direction, a herdsman will profit from keeping a clear view of attainable goals. All team members involved in our goat project participate in the planning stages as well as in the daily work; the "hands-on" experience is the basis for the decisions to be made.

Our second consideration in selection is the list of qualities that we believe will move us ahead. When deciding, we always remember the advice we have been given by prominent breeders who we revere as our elders in goat keeping. When faced with the decision of a new herd sire in 1993 we questioned Evin Evans of Split Creek Dairy in North Carolina for some good advice. We felt fortunate that a person such as Evans would take the time to talk to us, for in addition to her success as a commercial dairyperson; she is an ADGA judge and has placed well when exhibiting at the National Show level. Evans told us that in her years of goat breeding she had found that "form follows function." She explained that when making choices about what does to keep or what bucks to use she always made her choice in favor of milk. She found that to choose the milkiest animals also brought conformation and longevity into the herd.

We look to a buck's mother and grandmothers to assess our chances of getting the production and conformation we desire. Seeing uniform udder form and shape on these three does has proven to give a good indication of the type of udders a buck will produce.

We use a method of "guestimation" in an attempt to hedge our bets in favor of receiving the actual genes that will give us what we observe visually. The first rule of thumb is "have it in hand to pass it on." Simply stated, a doe with a lovely udder is more likely to pass it on than her full sister who is average in that area. A buck from an excellent dam and granddam is more likely to pass on this trait than a buck that comes from an average mother.

Once the lineage shows that a trait is not passed on to the next generation, we treat it as lost and consider it to be a nonentity in those genetics. Certainly, there are desirable recessive traits that will not be apparent and can resurface in the following generation. However, this is a risk that we have chosen not to take in our breeding program. Recessive traits are actually the easiest to breed for, if one considers that in order to exhibit a recessive trait, an animal must be genetically "loaded" for that trait. By loaded, I mean he has that potential on both gene sides, and has no other choice but to produce what is seen.

All breeders of livestock must play the genetics gambling game in order to succeed in the animal world. Basic rules indicate that if there are two traits of equal strength, there is a 50/50 chance of receiving either one. In life we find this not to be exactly true. It seems that some traits will be transmitted in bundles. To add to the confusion, some families pass these bundles more freely than others. In the line of LaManchas we have worked with we see this with the color genetics for black and white in contrast with the genetics that produce orange and cream. The orange ones were better milkers by volume and the black ones were the high butterfat does. Given a pair of full sisters, this would inevitably be true. In the LaMancha world in general, the does that fit the official American Dairy Goat Score Card would out-milk and out-live the ones who did not. We consider the effects of longevity balanced against the ability to withstand the rigors of production over extended time important in sire selection as well.

Milk production records are also very useful. Our goal has always been superior production. And more importantly, we look for long level lactation curves that provide us with an appropriate volume of milk over an extended period of time. Like stated earlier, we believe traits are passed most usually in groups, or bundles, and not as individual entities. So when looking for a herd sire, it's important to consider what traits have been passed consistently in his family and be sure to look at all four corners of his pedigree to see that there is a consistency of breeding in each corner indicating that these traits have come from a single and continuing source.

Line breeding using the four-corner method is just another way of saying look at the grandmothers. To make this visual, we place the buck's name in the center of a 4" x 6" card and write his mother's name on one side and his sire's name on the other. Then we write the parents' parents in their respective corners. The goal is to have each animal on the card be an individual that exhibits the qualities you wish to incorporate in your herd. If this is not the case you have opened yourself to the possibility that you are bringing in dominant and unwanted characteristics that will manifest in the kids produced. To add to the surety that we will get what we are seeking, in addition to the consideration of "where" these traits will come from we believe it is a plus to know "who" the traits will come from. We hope to see that the four corners of the pedigree card have a single ancestor exhibiting the proper trait, either in two corners of our card coming from each side, or as a parent of each of the four corners which would then come from all corners on both sides.

The more different the bloodline in the corners of this card, the more likely one is to miss the mark in adding the desired trait to the genetics one is breeding. For simplicity's sake, we would call this a "1" corner and view the possibilities of receiving genetic benefit to be rather random. When bucks like this are used, we have always had to cull the offspring heavily for the traits we needed—an expensive proposition in both time and labor. Then those doe offspring would need to be bred back into the buck's lineage exhibiting the new trait, or to the sire himself and the culling process proceeds another year. Although it is truly only three generations from the sale barn doe to Best in Show, the time and expense of this journey is prohibitive. What must be done in traveling on this journey is to build a "3" or "4" corner animal as described in the preceding paragraph.

To save both time and money, we like to buy a four cornered herd sire already composed by a thoughtful breeder. If this is not likely to be available we purchase a "3" cornered buck and a doe who will compliment the missing corner and in a year or two we will have bred our own "4" cornered sire. In Nubians back in the 1980s it was a simple thing to do—most of the big milking Nubians were line bred on GCH++*B Hallcienda Frosty Marvin. We purchased GCH ++*B Winterberry Shawn's Caviar who was "Marvin bred" on all four corners; in fact, he traced back to Marvin 32 times if the pedigree was taken to the limits. No matter what this buck was bred to he provided improvement in milk, mammary, stature, and topline. As a four-corner buck, he had no choice but to give us what he had been bred on. It was a bonus that three of his four corners were animals that would have been considered "4"s as well.

In addition to using the four corners to choose new herd members, the cards are used to select what breeding we will look to for herd replacements. The four corner cards made for every member of the herd include the milking records indicating length of lactation, total poundage and butterfat percentage. These have proven to be an invaluable tool in looking at the composition of our herd. We are able to predict with some accuracy what kids will look like and what production might be.

Always a consideration is the awareness that an animal who does not pass on the traits that the card indicates is culled as are the offspring produced. While this may seem like a drastic measure, we consider that to be able to manifest a herd vision and project it into the future is a goal to be met in the most expedient manner. We consider the pedigrees and the examples of the genetics we see in the flesh as signposts pointing the way to shape the herd of the future. A buck that is solidly bred to produce the traits he exhibits is the most economical way for us to proceed.
 

[Mustang Sally Farm]

Nubian Dairy Sires
It is believed in some circles that a more masculine,not coarse in appearance Nubian buck will pass traits from himself into daughter/s that will make them more feminine for dairynesss.

Masculine as in,lots of depth between the front legs,good body capacity,great flat bones.Breed character,long bell ears,that strong roman nose,good feet and legs.

The bucks dam should be put together very correct,beautiful udder,strenght and body capacity,good bones,solid,strong feet and legs.

Over refinded bucks,might not be the right answer to your breeding goal/s program.

[Mustang Sally Farm]

Probably one of the most overlooked aspect to any herd sire is the sires dam,grandma.Considering that a male will spread his gene pool further than any lone female,sires dam really becomes important.Should you not like the sires dam then breeding this buck will be of little value to your herd.Not only does one want a good breeding buck for herd improvements but a breeding buck with a dam that has interest to you.Who's your daddy and who is grandma??

[Mustang Sally Farm]

Reproduction and Genetic Selection

 Predicted Transmitting Ability and Reliability
Michel A. Wattiaux
The Babcock Institute




GENETIC EVALUATION OF DAIRY CATTLE IN THE USA

The genetic evaluation of dairy sires began in the United States in 1935. In 1974, the Modified Contemporary Comparison (MCC) index was implemented as an improved method of evaluating animals. Every six months, in January and July, the United States Department of Agriculture calculates the genetic values of cows and bulls whose records are collected by the Dairy Herd Improvement (DHI) programs. Since July 1989, the Predicted Transmitting Abilities (PTA) of cows and bulls have been computed using a statistical procedure called the "Animal Model." In the animal model, males and females are evaluated at the same time using an extremely powerful computer.

TRAITS EVALUATED

The five production traits for which the evaluation is performed are:
1. Milk yield
2. Fat yield
3. Protein yield
4. Fat percentage
5. Protein percentage

In addition, conformation traits (primarily udder, feet and legs, body form, and dairy capacity) are also evaluated. Genetic evaluation of bulls for productive life (life expectancy of daughters in the herd) and somatic cell score (a measure of resistance to mastitis infections) have been available in the United States since January 1994.

PREDICTED TRANSMITTING ABILITY

Transmitting ability is the average genetic value for a certain trait that an animal transmits to its offspring. The transmitting ability of a trait may be calculated with a certain degree of confidence (called reliability) using three sources of information:
1. The genetic merit of the parent;
2. Performance of the animal itself (when applicable);
3. The distribution of the records for a particular trait in the offspring of an individual (progeny test).

Figure 1: The frequency distribution of daughters around the average PTA of two sires
Figure 1: The frequency distribution of daughters around the average PTA of two sires

The predicted transmitting ability value of a bull is an average number; it is our best estimate of the genetic merit of a bull. The genetic value and performance of a particular daughter still contains an unpredictable component because each daughter receives a different set of genes from the bull. Chance determines the actual genetic merit of the offspring at the time of fertilization of the ova by the spermatozoon. In other words, the genetic merit of an animal cannot be predicted at the time of mating. For example, when two animals of high genetic merit are mated, the genetic value of the offspring will not necessarily be high. Although the offspring is more likely to be above average, it is possible that its genetic merit will be below average.

The performance of the daughters of a bull is distributed according to the bell-shaped curve, whether a bull has a PTA of 1000 kg or 0 kg for milk. It is important to realize that although Sire A has a PTA of 1000 kg, a few of Sire A's daughters may have a genetic merit below some daughters of Sire B, who has a PTA of 0 kg (Figure 1). However, the important point is that more daughters of the high-average sire (Sire A) have a PTA higher than daughters of the low-average sire (Sire B).

Genetic base

Genetic base is the reference point used to express the predicted transmitting ability of an animal for a trait. All PTA values are expressed as a deviation from the genetic base. The base is defined by setting the average predicted transmitting ability to zero for a group of animals. For example, in the United States until 1994, the PTA for milk yield was set at zero for all cows born in 1985 and still milking in 1990. There is a separate base for each trait and each breed of cow.

Strictly speaking, there is no need to modify a genetic base. However, as genetic progress is made, the PTAs continue to increase. It is only a matter of convenience that the genetic base is periodically upgraded. Some countries change genetic bases every year (Canada), whereas others change it only once every 10 years. In the United States, the genetic bases are modified every five years.

The impact of changing the genetic base is illustrated in Figure 2 for milk production. Changing the genetic base does not change the genetic value of an animal or the ranking of an animal relative to others in the population; only the reference point has been modified.

Reliability

Reliability is a measure of the confidence that should be given to the PTA estimate. Reliability reflects the amount of information in the PTA evaluation and depends primarily on:
• The reliability of the PTA of the parents and other relatives
• The number of records (cows)
• The number of herds in which the daughters are located (sires)

It takes about 30 daughters in 30 different herds to obtain a bull's PTA evaluation for milk yield with a reliability of about 70%. One hundred daughters in 100 different herds increases the reliability of the PTA to about 88%. The greater the amount of information available, the higher the reliability and the less likely it will be that future PTAs will be different from current PTAs. A PTA with a reliability of 70% is likely to change in the future. The direction of the change is unknown; as more information is available, the PTA value may go up, go down, or remain almost unchanged. Thus the use of a sire with a low reliability entails a greater risk, but at the same time a greater opportunity than a sire with a highly reliable PTA (more than 90%), which is no longer expected to change greatly.

Figure 2: Effect of changing the genetic base on PTA value for milk yield
Figure 2: Effect of changing the genetic base on PTA value for milk yield

Confidence range

Confidence range reflects the interval within which the animal's true transmitting ability is expected to be 68% of the time (two out of three times). A confidence range is useful because it gives a realistic expectation of the magnitude of change that may affect the PTA of a bull.

Confidence range is easy to calculate because it depends only on reliability and the standard deviation for the trait of interest. The lower and upper limits of the confidence range can be calculated as follows:


Lower limit = PTA - deviation;
 Upper limit = PTA + deviation;

where deviation =

sqrt(1-reliability)x genetic standard deviation.

Table 1: Approximate deviation from the mean that can be used to calculate a confidence range in which the true PTA of an animal will be found two out of three times*


Reliability
 (%)
 Deviation = x genetic standard deviation
 
 

Milk
 
Protein
 
Fat
 

Kg
 
Lbs
 
Kg
 
Lbs
 
Kg
 
Lbs
 

50
 
180
 
396
 
6
 
13
 
7
 
16
 

70
 
139
 
307
 
5
 
10
 
6
 
11
 

75
 
127
 
280
 
4
 
10
 
5
 
12
 

80
 
114
 
250
 
4
 
8
 
5
 
10
 

85
 
98
 
217
 
3
 
7
 
4
 
9
 

90
 
80
 
177
 
3
 
6
 
3
 
7
 

95
 
57
 
125
 
2
 
4
 
2
 
5
 

99
 
25
 
56
 
1
 
2
 
1
 
2
 

*For calculation of the deviations in this table, the genetic standard deviations were assumed to be: Milk yield 254 kg (560 lbs); Protein yield 8.6 kg (19 lbs); Fat yield 10.3 kg (22.5 lbs).

Let us calculate the confidence interval for two bulls, both with a PTA for milk of 1,000 lbs, but with reliabilities of 70% and 99%, respectively. As indicated in the footnote of Table 1, the genetic standard deviation for milk yield is 560 lbs. Thus for a bull having a PTA with a reliability of 70%, the deviation from the PTA is x 560 = 307 lbs. The lower limit of the confidence range is 1000 - 307 = 693 lbs, and the upper limit is 1000 + 307 = 1307 lbs. Thus we would predict that two out of three times the bull's true PTA value lies between 693 lbs and 1307 lbs. This also means that one out of three times the bull's true value lies outside this range; one out of six times the true PTA will be less than 693 lbs of milk, and one out of six times the true PTA will be more than 1307 lbs of milk.

Once the reliability of the PTA is 99%, the confidence interval is quite small. In our example, a bull with a PTA of 1000 lbs and a reliability of 99% has a true transmitting ability between 944 lbs and 1056 lbs two out of three times (Figure 3).

Figure 3: Confidence range (68%) and reliability of PTAs for milk yield
Figure 3: Confidence range (68%) and reliability of PTAs for milk yield

[Mustang Sally Farm]

Reproduction and Genetic Selection

 Choosing a Bull
Michel A. Wattiaux
The Babcock Institute




The choice of bulls used in the herd today determines what kind of cows will be in production three years in the future. Choosing a bull should be based on the following considerations:
• Prioritize the traits considered for selection and give each trait relative importance-production traits should be three to five times more important than conformation traits
• Use a selection method-the independent culling method or preferably a selection index-to choose a bull based on PTA values
• Do not use reliability to select sires-use reliability to decide how "heavily" to use selected sires

USING PTA FOR SELECTION DECISIONS

The basic purpose of Predicted Transmitting Ability (PTA) is to rank bulls. If a bull has a PTA of +1,000 kg of milk, it does not mean that his daughters will produce 1,000 kg more milk than their herdmates. It does mean, however, that the daughters of this bull have an average milk production 1,000 kg higher than the daughters of the bulls used in the genetic base. Selection should be based on the PTA value of a bull. A common mistake is to use reliability as a criteria for selection. The proper way to use reliability values will be explained later. In terms of selecting sires, two methods are available: the independent culling level and the selection index. Although both methods have advantages and disadvantages, the index method is preferred by geneticists because it usually offers the possibility for greater genetic progress.

Independent culling level

Independent culling level is a method by which the producer sets a minimum value for each trait in the selection program (In the case of calving ease, the criteria is not a minimum, but a maximum value for percentage of difficult calving). Sires above the minimum for all traits are considered for selection. For example, assuming that two traits of importance are PTA for milk yield and PTA for protein yield, one might decide to choose from among sires with a PTA milk yield greater than 2,250 pounds and a PTA protein yield greater than 65 pounds. As illustrated in Figure 1 only two bulls in the US population in January 1995 would meet these standards.

Advantages

This is the simplest method to identify bulls that meet the goals of a selection program.

Disadvantages

The first difficulty in using the independent culling level is to set the (minimum) standards. A sire may be rejected for failure to meet a standard, even if it is only by a few pounds, while all other traits may far exceed the minimum standards (Figure 1). The need to update the standards periodically is another drawback of independent culling levels. When sires are selected with this method, genetic progress and the change in genetic base may affect which sire becomes the most desirable. If a set of standards has been used for several years, more bulls tend to be in the acceptable group because of genetic progress. Other criteria must be found to select the desired sire or the standards have to be adjusted periodically. In addition, when the genetic base is changed, only very few (if any) of the bulls might meet the standards; again, the standards need to be reviewed and adjusted accordingly.

Figure 1: Selection of sires using the independent culling level
Figure 1: Selection of sires using the independent culling level

Selection index

Use of a selection index allows the ranking of bulls based on a value calculated by giving each selected trait a "relative weight." The "weight" represents the importance that a producer chooses to give to a particular trait. The actual price for milk components, for example, may be used as a weighing factor. In this case, the index would have a currency unit (dollars, francs, etc.). However, the absolute value of an index is really of little importance. Bulls should be ranked according to the most appropriate index, and the highest bulls on the index should be used regardless of the value of the index itself. In other words, there is no significance to setting minimum standards for the value of an index.

Advantages

An index allows identification of bulls that best fit the overall genetic goal without focusing on any trait in particular. Indices force producers to consciously evaluate the traits they want to emphasize and formulate a specific plan for maximizing them in the herd. Once an index is built properly, selection of sires is much simpler than independent culling levels because the best bulls, simply, are the ones that rank at the top of the list. In addition, an index is an objective method to give credit to sires that may be rejected using an independent culling method because they fall short of the standard for one trait.

Disadvantages

Indices are difficult to build because it is difficult to choose the traits to include and the weight to assign to each trait. Many "pre-calculated" indices are now available. Which of the available indices reflects the priority set for a herd is a difficult question to answer. Some indices give an important weight to conformation traits. In other indices, the economic weight given to yield traits is based on the structure of current milk prices in the United States. The interpretation of these indices is difficult for dairy farmers of other countries because, clearly, the pricing of the milk varies widely from one country to another.

How to build a selection index that reflects expected increases in gross income

As an example, let us assume that we are building an index for a market that has the following milk pricing structure. Let us assume that the milk price is 12.2 (any currency unit) per kg for milk containing 3.5% fat and 3.2% protein. The processing plant pays 0.150 currency units per 0.1% of fat (or per gram of fat) and 0.300 currency units per 0.1% of protein (or per gram of protein). The relative weight given to milk yield, protein yield and fat yield may be calculated as follows:
• Value of 1 gram of fat = 0.150 currency units, value of 1 kg of fat = 150 currency units, value of the 35 g of fat in 1 kg of milk = 0.150 x 35 = 5.25 currency units
• Value of 1 gram of protein = 0.300 currency units, value of 1 kg of protein = 300 currency units, value of the 32 g of protein in 1 kg of milk = 0.300 x 32 = 9.60 currency units
• Value of 1 kg of milk without fat and protein = 12.2 - 5.25 - 9.60 = -2.65 currency units

Thus we can calculate an index that will reflect the expected increase in gross income of the daughters of a sire based on his PTA for milk, protein and fat yields. Let us call this index PTA-AGI (Predicted Transmitting Ability of Added Gross Income). We use the terminology gross income because, as cows produce more milk, they eat more; however, the extra cost of feeding is not included in our index.


PTA-AGI = (-2.65 x PTA kg of milk) + (300 x PTA kg of protein) + (150 x PTA kg of fat).

For example a sire with milk PTA of 800 kg, a protein PTA of 20 kg, and a fat PTA of 38 kg, would have a PTA-AGI index of:


PTA-AGI = (-2.65 x 800) + (300 x 20) + (150 x 38) = 9,580 currency units

HOW MANY BULLS SHOULD BE USED IN A HERD?

The number of bulls and the strategy of selecting bulls may differ as a function of:
• Herd size
• Bull's reliability
• The inclination of the farmer to take measured risks. free of serious mastitis

When young sires are selected, the purchase of semen should be limited to only a few units per bull so as to spread the risk. As reliability increases, semen purchases per bull can increase. There is little reason to breed more than 15 to 20% of a herd to any one sire, even if the sire has a PTA with a high reliability. In other words the minimum would be to select at least three sires for every 50 cows in the herd. Diversification is a safeguard against any unforeseen problems that may arise as the result of using any one bull heavily in a herd.

USE RELIABILITY TO DECIDE HOW MUCH TO INVEST IN A SIRE

Reliability indicates the accuracy of genetic evaluations. Often producers use reliability as a criteria for selection. Actually, reliability should never be used in selecting sires; however, once sires have been selected, reliability should be used to decide the intensity of usage (i.e., quantity of semen to purchase). The number of available sires is large and it is tempting to reject those for which reliability of PTA is low. However, using reliability as a selection criteria is likely to limit genetic gain.

Figure 2: Example of change in PTA of 20 sires as reliability increases from 70% to 99%; each sire is identified by a rectangle labeled from 1 to 20 and the distribution of their daughters is illustrated by the horizontal bell-shaped curves.
Figure 2: Example of change in PTA of 20 sires as reliability increases from 70% to 99%; each sire is identified by a rectangle labeled from 1 to 20 and the distribution of their daughters is illustrated by the horizontal bell-shaped curves.

The true genetic value of sires that have a PTA with high reliability is very certain and is not likely to change over time. For some producers, this feature may be important because it guarantees that the genetic merit of the daughters is predicted to be in a narrow range around the PTA. However, high reliability might be considered by others as lack of opportunity. Younger bulls usually have lower reliability because of the limited numbers of daughters in their progeny test. Yet, bulls with the highest genetic merit are among the bulls being progeny tested; we just do not know which ones they are. So how can one take full advantage of the genetic superiority of certain (young) bulls, despite the uncertainty of their PTA?

We know that a PTA accompanied by a low reliability is likely to change, but we cannot predict ahead of time whether the PTA will go up or down. Indeed, when two sires have the same PTA, it is actually more risky to buy a lot of semen from a sire with lower reliability.

If instead of focusing on one young sire, we focus on a group of young sires, the risks will change drastically. Let us consider the future of a group of young sires with high PTAs and low reliability (Figure 2). In general, any time the PTA of a sire decreases, the PTA of another increases. In a group, the bulls that decline in PTA usually are counterbalanced by bulls that increase, for an average of near zero. As a result, the overall PTA average of a group of young sires will remain unchanged over time because the decline in PTA of some of them will be compensated by the increase in the PTA of others (Figure 2). In other words, the best strategy to minimize the risk of low reliability and still maximize potential genetic gain is to focus on low reliability sires as a group. The strategy should be to buy some semen from many young sires as opposed to buying a lot of semen from only a few young sires. By purchasing a few units of semen from several different, low reliability bulls, the chances of milking a large number of daughters from any one bull that may decline in proof is limited; and the chances of milking a few daughters from any one bull that may increase greatly in proof is maximized.

Not all bulls/bucks from the same herd will have the same rate for production.Some will be higher and some lower.The reliability factor is really hard to figure out for bucks over cattle because of the fact.In the west only a handful of bulls are responsible for the majority of calves born,realiability is easier to measure.Buck goats are so spread out that tracking any single buck is difficult.Any buck with 30 daughters in 30 different herds in the Philippines is still some time away.The importance of using more than 1 breeding buck in your herd and by observations and data collection can help the breeder/producer keep track for reliability.Not all bucks born on the farm will score high for reliability which is what that buck transfers in traits needed,two out of three times to his offsprings.

This gets into some really advanced breeding.