On-Farm Performance Testing

Performance Testing for Sire Evaluation and Selection

Dr. Frank Pinkerton, akathegoatman@icloud.com; 512.392.4123

Boer goat owners are continually searching for herdsires that will improve overall performance of their herds. Performance testing is the key and a much more effective method for herdsire selection than appraisal of phenotypic characteristics. I excerpt passages from my book on meat goat management and marketing made by contributing author, Dr. Richard Browning, animal geneticist at Tennessee State University-Nashville.

Performance testing is the comparative evaluation of goats for production traits of economic importance: reproduction, growth and carcass merit. Ancestry (pedigree) and visual appraisal for conformation (appearance) have been the primary basis of animal selection in meat goat herds. Most resource inputs (i.e., herd expenses) go into annual doe management. In return, does are expected to become pregnant, deliver newborns and raise multiple kids with good growth to weaning.

Reproduction is generally viewed as the most important trait of meat animal production. Reproductive output in a meat goat herd is defined as litter weight weaned per doe exposed to the buck. On-farm performance testing includes the comparative evaluation of does for reproductive output, the evaluation of individual kids for weight gain, and, in multi-sire breeding programs, herd sire comparisons of progeny performance.

Objective, accurate recording allows producers to make better selection and culling decisions and, secondly, to measure performance responses to management changes. Performance records should be easy to collect and use. They can be handwritten records in a notebook or on index cards. Each animal in the breeding herd should have a separate record. Alternatively, records can be maintained electronically on computer spreadsheets or herd management software. Electronic records allow easy handling of data for analysis or transfer to central processing centers such as industry organizations or universities, particularly for herds with large sets of data accumulated over several years. However, a hand calculator and a little time are all that may be required for processing data from smaller herds using handwritten records. Regardless, proper record keeping is essential to a successful performance testing program.

Animal identification

A prerequisite to performance testing is proper identification of animals. Ear tags and tattoos are the most common forms of ID for meat goats. Assign each herd member a unique and permanent ID number. Assign ID numbers to kids at birth when collecting early data such as birth weights, litter sizes and neonatal deaths. Newborn kid data must be matched with the correct doe. In herds with many does kidding together on pasture or range, it can sometimes be challenge to tell which kids belong to which does. Rejected kids, early newborn deaths, and the occasional swapping of kids by does make it important to properly and adequately ID kids soon after birth, preferably within 12-24 hours.

Scales

Scales are another requirement for a performance testing program. Body weight is undeniably important as a measure of meat animal performance as well as for aspects of general herd management. A small hand-held scale is sufficient to records birth weights. A larger livestock scale is needed for weaning weights. Scales may be bought, borrowed or rented, depending on the needs and resources of individual operations. A scale should be periodically checked to ensure accuracy and precision.

Contemporary groups: A contemporary group is a set of meat goat kids born and raised together under uniform conditions. Performance testing for genetic evaluation requires factors like age, nutrition and location to be equal for all kids. Kids in a contemporary group are born within a 60-day period and managed together from birth to weaning. Dams should also be managed similarly to weaning. Data from kids born outside the 60-day window or managed differently (e.g., on show circuit, bottle babies, kept in separate pastures) are excluded from the group. Contemporary groups for kids weaned at three months old are planned 8-10 months earlier at the start of breeding. Breeding seasons no longer than 6-7 weeks assure that kids will be within the 60-day age range at weaning.

Performance recording

Primary traits to record in a meat goat herd are the number of kids born and weaned from each doe exposed

to bucks, kid birth and weaning weights and dam weight at weaning. Birth weight is the starting point to determine pre-weaning growth rate. Record newborn weights within 24 hours of birth. Record weaning weights at around 90 days of age. Weaning weights are usually recorded on one calendar date for a group of kids that vary in ages. The ages within a contemporary groups of kids should deviate from 90 days by no more than 28 days. It is also useful to weigh the dams when the kids are weaned. Dam weights are used to calculate the efficiency of doe production.

For each doe exposed to the buck, record the number of live births and the number of kids weaned. Note stillborns in a doe’s file and use them for litter size, but they need not be weighed. Artificially-raised kids are not credited to the dam for weaning litter size or weight. In cases when a doe adopts a kid from another doe, the adopted kid can be credited to the ‘foster’ dam for weaning data. Failure to birth or wean a kid following buck exposure are recorded as zero (0) for the doe.

Animal evaluations

Because ages vary in a contemporary group of kids at weaning, weight comparisons can be biased. A 79-day-old kid cannot be expected to weigh as much as a 112-day-old kid. Therefore, weaning weights are converted to a standard 90-day age basis. Two equations are used to generate 90-day weights.

First, calculate average daily gain (ADG):

ADG = (w.wt – birth wt) /weaning age in days

After the average daily gain is determined, the second equation gives the 90-day weight:

90-Day Weight = (ADG x 90) + birth wt

When birth weight is not available, ADG cannot be determined. In the absence of birth weight records, the previous equations can be replaced with the following equation based on weight per day of age:

90 Day Wt = (wwt /weaning age) x 90

Adjustments are made to 90-day weights because litter size and age of dam can affect weaning weight. On average, weaning weights decrease as litter size increases and young does wean lighter kids than mature does. Multiply 90-day weights by the appropriate correction values to get adjusted 90-day weight factors.

Buck kids are typically heavier than doe kids, but sex of kid adjustments are not required because comparison are made with sing sex groups. Buck kids are compared only to other buck kids and doe kids are compared to other doe kids.

An additional step is generating weaning weight ratios. Within each sex groups, individual kid weights are compared to the group average to produce rations for relative evaluation. Ratios show the deviation of kid weaning from the contemporary group average. A ratio is calculated with the following equation:

WWT Ratio = (90-day kid wt/90 day herd wt average) x 100

A ratio of 100 is equal to the group average. A kid with a weight ratio of 122 is 22% heavier than the group average. A kid with a ratio of 91% is 9% lighter than the group average.

Sire and Doe Evaluation

In herds using multiple sires, kid weights and ratios can be used to compare sires for progeny performance if each kids’ sire is known. Buck and doe kid ratios may be combined for sire evaluations. Adjusting doe kids to a buck kid weight equivalent is required to combine buck and doe kid weight records for sire evaluation.

For each dam, add the weights of all kids she weaned. Actual or 90-day weights can be used for doe evaluations. Actual weights are preferred because they credit the ability of does to breed early and raise kids for a longer period of time, weaning off more weight on average compared to does bred later in the season. When comparing young and mature does, correct kid weights for age. A sex-of-kid correction can also be made to put doe kids on a buck kid weight-equivalent for unbiased litter weight evaluation.

Litter size corrections are not made to kid weights for doe evaluation. Zero (0) is recorded for litter weight weaning of does not weaning a kid. Litter size at birth and weaning should be assessed for each doe. After two or three production years, a certain average number of kids weaned by does should be expected, such as 1.5 kids weaned per buck exposure. Doe production efficiency can be measured by how much total litter weight a dam is able to wean relative to her own body weight. A heavier doe (e.g., 150 pounds) tends to require more management inputs than a lighter doe (e.g., 100 pounds). However, the heavier doe may or may not be able to convert the greater inputs into a correspondingly heavier litter weaning weight. The following equation provides the efficiency of doe production:

Doe Production Efficiency = (litter wwt/dam wt at weaning) x 100. (FP: the calculation allows one to better compare does of different weights).

Nutritional resources are used by does for self-maintenance, reproduction to produce kids, and milk production to raise kids. In young does, growth must also be supported.

Forage and feed inputs may be available in limited or unlimited supply to does and usually represent the primary expense of herd management. Doe production efficiency values vary widely, ranging from less that 50% to over 100%.

Recording other important traits

Other production-related traits should be of interest to producers. Growth rates after weaning can be evaluated on farm when goats are retained to heavier market weights or when developing replacement stock. Always keep detailed health records on each animal in the herd. Evaluation of records is recommended for traits associated with internal parasitism, lameness, abortions, mortalities and other health concerns to help in making selection and culling decisions and for reviewing various herd management procedures.

On-farm performance testing of the does herd is important in crossbred, commercial meat goat operations expecting good doe kid performance with minimal management inputs. On-farm performance testing is important in purebred seedstock operations that expect to provide genetics to commercial meat goat producers. Each producer will set site-specific performance levels for selection and culling decisions.

Performance records, when used in conjunction with visual appraisal and pedigree, facilitate genetic improvement for economically important traits. Performance records allow for the evaluation of management procedures and how changes in herd management affect animal performance. Performance records, when coupled with financial records, provide the basis for assessing the economic status of an operation and the likelihood of making a profit or incurring a loss from year to year. Performance and financial targets usefully provide direction to breeding programs. On-farm performance testing helps owners achieve their herd goals and objectives. Correction values for 90-day kid weaning weights: Multiply value figure X litter weight to correct. Group Value

Litter Size: 1 & 1 1.00 (# born & # weaned) 1 & 2 1.14 2 & 1 1.04 2 & 2 1.18 3 & 1 1.08 3 & 2 1.23 3 & 3 1.27

Age of Dam 1 1.10 (years) 2 1.09 3+ 1.00

Sex of Kid Buck 1.00 Doe 1.11 Wether 1.08

(Values courtesy of Dr. David Notter, Virginia Tech)

Logistics

I now describe the logistics (the how-to) of collecting, analyzing, and utilizing on-farm performance data. Put differently, how does one generate the performance figures, how does one evaluate the figures, and, most importantly, how does one put this genetic selection program into action? First, contact Dr. Ken Andries, animal geneticist at KY SU-Frankfort, atkenneth.andries@kysu.edu or c502.682.0067.

If you decide to participate, Ken would enroll you in the free program and discuss initial actions on his and your part. You would provide him your contact information as well as your location and number of breeding age females and also your estimated kidding schedule(s) so that he can get the forms to you in a timely manner. Only Ken and you have access to this data; it is shared with no one. It is only for your use; it cannot be compared to other herd data because the production environments are not the same.

Data collection

As kidding time approaches, Ken will send you two forms. The first is a code sheet which enables you to identify certain needed information about the does and their kids. The code categories for breed, livability, birth type, rearing type and kidding ease are crucial for analysis of doe performance. He will also send you kidding data sheets that enable you to provide specific information about each doe and her off-spring.

When all the litters in a given ‘kidding group’ of does have been weighed, you return the kidding data sheets to Ken by email or mail. A ‘group of does’ is defined as those kidding within a 60-day interval of each other. A producer may have two or more such groups depending on his breeding/kidding schedules.

The rationale for this evaluation-by-group is that the environment (climate and feeding program) changes over time; accordingly, it is not fair to compare litter performances from spring-kidding does to fall-kidding does to winter-kidding does.

If it seems too inconvenient to get birth weights, you don’t have to provide Ken birth weights of individuals or litters in order for him to compare 90-day (adjusted) litter weaning weights. He can compare weight-per-day-of-age (weaning weight/days of age, as adjusted).

There is usually a small, but positive correlation between birth weight and 90-day weight (reflecting birth weight per se and the more aggressive suckling by larger, more vigorous kids). Should early culling decisions be required, this correlation could be used to do so. Birth weights are also useful for assessing possible impacts on kidding-ease scores and livability scores. Perhaps it may be useful to remember that

final litter weight, not average daily gain, is the most useful selection criteria.

Data analysis

When Ken receives your data sheets (as described above), he will transpose the raw figures to his computer program and apply adjustment factors to the data to derive ‘adjusted 90-day litter weights’ for each doe. Essentially, you give him the weight of each litter and associated info and the program will do the rest. The properly adjusted litter weight at weaning for each doe will reflect: calculated 90-day weights, age of dam at parturition, number of kids born in the litter, number of kid weaned in each litter, and sex of kids in each litter.

In due time, Ken will send you a doe summary sheet showing the adjusted litter weaning weights for comparing all does in the group. All your does should be evaluated, or else you would be lying to yourself, and also to your prospective customers; why bother to partially-test at all?

During analyses, the computer program first calculates the average adjusted litter weaning weight for the group and, secondly, compares each doe’s record to this average, and assigns it a ratio figure. For example, if the group’s average adjusted litter weaning figure were, say, 80 lbs, and doe A posed a 125 ratio she was 25% above (better than) her group average. If doe B posted an 80% ratio, she was 20% poorer than the group average. Comparison of doe ratios enables rational keep-or-cull decisions.

Ken’s program can also provide a sire summary sheet if you have kids in a given 60-day kidding groups sired by two or more sires. This summary will show the number of kids weaned (having 90-day weights) from a given sire as compared to the number of his kids born—a most useful comparison indeed. One may calculate kid survival rates for each sire (number of kids weaned/number of kids born x 100).

The crucial sire performance figures are the Average Adjusted 90-Day Weights (AAWW). The sires may be evaluated mathematically as shown below: Rank Sire AAWW Ratio 1. 616 34.58 105.8 2. 859 33.82 103.5 3. 4006 32.67 100.0 4. 146 32.47 99.4 5. 5052 29.81 91.2 Average 32.67 100.0

As readers will perceive, this year’s kid crops suggest that bucks 612 and 859 produced kids only 3.5 to 5.8% higher than the average weaning weight, respectively. With prior records for comparison, one could know if these ‘findings’ were consistent over 2-3 years. However, owners could also evaluate these sires by tabulating the performance Ratios of their daughters in this and prior years.

Those sires having a majority of their daughters with 80-plus ratios over the years would be the keepers (and so would be the dams of saleable young buck prospects, of course).

Utilizing Performance Data

If all your herd kidded within the requisite 60-day interval and all does and kids were treated alike until weaning at about 90 days of age, you could use the ratios shown to select keeper-does and to choose keeper kids from particular does. If you have two, or more, kidding periods, there is the issue of choosing between does with similar Ratios, but in different groups—a tough one that only you can decide because only you know the seasonal situations. Look first at the group averages for guidance.

Caveat: The degree of selection pressure you could apply across the entire herd would be dependent on your site-specific situation (herd size, expansion/contraction plans, cashflow needs, prospective sales, expected feed supply, any resource limitations, etc.).

Understand that the speed of herd improvement you can achieve depends on the ‘reach’ of your prospective herd sire, i.e., his performance must be appreciably better than the performance of the does; if it is not, progress will be slow indeed.

Remember also that you will have reduced rate of improvement when the heritability of the traits you are trying to improve is low. (Heritability of reproductive traits are rather low (.3 or less) while heritability of ADG is moderate (.45 or so) and heritability of carcass quality is higher (.6 or so).

Also, attempting to improve multiple traits simultaneously will slow the overall rate of improvement. Remember too that economic traits are the most important to the productivity and profitability of your operation.

And, a final observation for those of you engaged in show stock production and associated show activities. If you do performance testing, you well learn if your best looking goats are the most productive goats in terms of fertility, fecundity, feed conversion efficiency, gains/day etc.

Remember that economic traits are the most important to the productivity and profitability of your operation.