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A Link Between Staple Length and Depth of Color

As part of our work using data from the AOA EPD database to examine whether fleece color affects the expression of fleece traits, we looked at the relationship between color and the EPDs for staple length for over 1300 males in the EPD database.  We found a pattern that suggests that faster fleece growth rates have a visible dilutive effect on the color we see in fawn, beige and white animals, by increasing the length of the hair relative to the amount of pigment produced to color it.   

 

This means that two animals with identical genotypes for color (and similar environments, etc.) could have phenotypically different colors if their fleece growth rates were different:  The one with faster fleece growth would appear lighter than the one with slower growth.

 

The implications for breeding decisions?  We discuss some of them in our library article on this topic.  Enjoy!

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Does Depth of Color Affect the Expression of Other Fleece Traits?

We ask the question above as a short lead-in to an only slightly longer – but quite interesting – look at the possible connection between the depth of color of an animal’s fleece and the curvature of the fibers in that fleece, discussed in our library article on this topic.    Our curiosity about this was stimulated by analysis of the amount of pigment present in the fiber of different colored alpacas that was published in Kylie Munyard’s 2011 paper, “Inheritance of White Colour in Alpacas”, which, as we have noted before, has quite a bit to say about the likely genotypic characteristics of colored alpacas as well.

Those of you who breed for dark browns and blacks, or who process dark-colored alpaca, will be well aware that these fleeces are quite different than otherwise similarly fine and uniform white and light fleeces in particular.  The yarns we make from fine dark fleeces are equally sumptuous but denser, silkier, and often notably bright.  They are suitable for different types of end products than those we produce with elite light fiber.  And, as the analysis in our library article suggests, it seems likely that these dark fleeces are different at least in part because the comparatively large amount of pigment in the hair affects how much curvature – a measure that correlates with crimp frequency, as well as memory in yarn or knitwear – is expressed in the fleece.  

If true, this is more than a interesting bit of trivia.  For one, it means that we need to consider carefully what an “advanced” or ideal dark colored fleece should look like with regard to character.    Breeding for finely crimped dark animals may well mean selecting against the total amount of pigment present in the fiber, which may or may not be readily visible to the unaided eye in some instances, but may have implications for the underlying genotypes, or other characteristics of the fiber and its performance.  And that brings up a second, broader question, which is whether the amount of pigment in fiber, or the processes associated with its creation and presence, could affect the expression other fleece traits.   While we wait for these questions to be answered with further research, it’s probably good to hold onto the idea that breeding for elite dark-colored animals may well produce fleeces that have very different visual and performance characteristics than lights, but are equally elite, appealing, and valuable.

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No Such Thing as a Dominant White?

If any of the assertions below contradict what you believe about alpaca base coat color genetics, it’s definitely worth reading this blog post and continuing on to a very friendly, fun-loving statistical analysis that is available in our website’s library!

1. First, all white alpacas can produce color when they are bred to it. There is no such thing as a homozygous dominant white animal.  In fact, a pink-skinned white is in some ways as recessive a creature as a true black.

2. What’s more, many fawns are not just “dilute” but carry a white base coat color allele, which acts to dilute a brown allele in the production of the phenotypic coat color. You can actually breed two fawns together and get a homozygous white.

3. White breeders, no need to rely on those pure-white pedigrees to make sure you don’t produce fawns and browns. Turns out a brown allele can’t really hide itself well phenotypically.

4. Color breeders, to introduce white genetics into a color breeding program with lower odds of producing white offspring, breed that white animal to brown. The darker, the better.

Now, if you are like me and lack an educational background in genetics, it may also be true that, like me, you find it hard to wade through genetic research on alpacas.  In my case, I can sometimes remember a conclusion from a genetics paper for only a few hours after I read it.  Sad, but true: Ask me a few days later and what I remember about the paper is likely to be “It had a lot of letters that didn’t make words.”   Lacking an intellectual framework for understanding the research, I have had trouble retaining what genetic research I have read long enough to evaluate it in the context of my own experience, let alone incorporate it into my breeding strategies.

However, I do have an antiquated background in statistical modeling! (Insert half-hearted cheers.) And I brushed the cobwebs off of it a few weekends ago to analyze an observation that had been vexing me:  Why, if white is supposedly the “dominant” alpaca color, do I not see large numbers of whites in my own herd that cannot produce color when bred to it?  In fact, I see the opposite.  All of my white whites seem happy to produce color when bred to it, even with deep, multi-generation white pedigrees behind them.  How can this be?

I used basic probability analysis to demonstrate that this outcome is incredibly unlikely if the white base coat color allele is dominant over brown and black, as many of us were once taught.  Then I went back to review Kylie Munyard’s 2011 research on alpaca coat color, and found that she posited a incompletely dominant white allele, along with several other conclusions that came as a complete surprise to me, even though I had previously read that paper several times (I told you.)  Long story short, I found that they fit existing multi-generation color production data better than the classic dominant white/dilution theories do.     I also found they opened doors to new breeding strategies.

I wrote about these findings for a blog post, but the write-up ended up a bit too long for this format.  So I have posted this analysis on our new research library page on our website, (see the tab above, or follow this link Evaluating Genetic Color Hypotheses) along with Kylie Munyard’s 2011 paper.   If the assertions at the start of this post were surprising and/or of interest, read the analysis in the library for more information.  I especially recommend this for breeders of fawns and whites. 

 

 

 

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Alpaca Temperatures and Fertility:  We Checked Some Numbers

                                                       

December 2016.  Those of you who are familiar with our alpaca breeding effort know that we are quantitatively oriented and research-focused.  We also like to share what we learn as broadly as possible.  Some of our research results – especially those from projects led by the human embryologist and fellow alpaca breeder Dr. Kim Gleason, of Dancing Horse Farm – find their way to formal publication.  Sometimes, though, there is incremental yield from our research and data collection that we can distribute more informally, and that is what we will be using this blog for going forward. 

It was because of one of the preliminary results from participation in one of Kim’s long-term studies (in this case, on the effect of various husbandry choices on the sex ratios of crias produced,) that we began to collect temperatures on all of our sires and dams at the time we used them for breeding.  Previously, we had seen a close association between high ambient (i.e., environmental) temperatures and the production of a disproportionately large number of male crias relative to females.  We also understood that it was not the ambient temperature per se that was affecting the sex ratio, but rather the tendency of the animals’ temperatures to vary as a function of it.  In addition, we knew that looking at ambient temperature alone overlooked many important contributors to the animals’ response to heat and cold.  Accordingly, we begin to collect breeding-time animal temperatures in the summer of 2016.  In a year or so, we will be able to discover how those internal temperatures at the time of breeding correlate with the sex ratio of offspring produced by our animals.

In the meantime, however, the analysis of animal temperatures and breeding outcomes has begun to produce other useful feedback.  For instance, we were able to look at this year's breeding data to see if the fertility of our animals declined when they were hot, as has been documented in other livestock species.  We found that it did.   In particular, our data suggests that the likelihood that a breeding produces a pregnancy is lower when the females, but not necessarily the males, are very hot.  More surprisingly, we also find some evidence that even females with internal temperatures in the warmer part of the so-called “normal temperature range” (usually described as between 99.0 and 102.0 Fahrenheit) show a reduced likelihood to produce a successful breeding outcome compared to those with temperatures under 100.0 degrees.   It does make you wonder where that referenced  “normal range” came from.  In any case, the results are pretty dramatic, and, in combination with the tendency of heat-stressed animals to produce male offspring, are causing us to rethink our breeding calendar. 

In Exhibit 1 below, we show both the breeding success rate and average temperature of our dams and sires during August through October 2016.  Although we breed animals year round, this represents our busiest season, and overall, we did 100 breedings of our farm’s females during that time.    As Exhibit 1 reveals, we had a horrible time getting our animals pregnant in August, when they were hot, with only about one out of every three breedings leading to a confirmed pregnancy.  By contrast, in October, when the average animal’s temperature was about two degrees lower than in August, roughly two out of every three breedings produced a confirmed pregnancy (please note that we have removed from this analysis all breedings we conducted with either an unproven sire or dam, as their fertility status is unknown.)

Exhibit 1:  Breeding Success Rates By Month

 

 

Month

 

 

Total Breedings

 

Total Breedings

Confirmed

Breeding

Success Percentage

August 2016

28

9

32%

September 2016

36

16

44%

October 2016

36

22

61%

 

Of course, other things besides temperature change with the seasons.  For instance, the amount of daylight varies, as may the amount of fresh forage versus hay, along with other factors that could conceivably affect fertility.  So we looked at the relationship between animal body temperature and breeding success to see if the apparent relationship between the two persisted regardless of the month of the year.  As Exhibit 2 shows, it did.   But the difference between the results for dams and sires begs the question of whether one gender is more important than the other with regard to our fertility results. 

Exhibit 2:  Breeding Success Rates By Temperature of Sire and Dam

Dam

Temp

Total

Bred

Total

Conf.

Percent

Success

Sire

Temp

Total

Bred

Total

Conf.

Percent

Success

>=102.0

25

8

32%

>=102.0

20

8

40%

100.0-101.9

 

57

 

22

 

39%

100.0-

101.9

 

64

 

27

 

42%

<100.0

33

22

67%

100.0

31

17

55%

 

Of course, overall temperatures of both sires and dams are positively correlated.    A hot day here heats everyone up.  But for various reasons -- including but possibly not limited to differences in phenotype, age, condition, and housing -- our males’ and females’ temperatures are not perfectly correlated.  Sometimes we do a breeding where the female’s temperature is relatively high and the sire’s is not, or vice versa.  Looking at this particular subset of “mismatched” temperatures shown in Exhibit 3 gives us further insight – though we must be careful not to draw too strong a conclusion at this point because the amount of data we have for this way of looking at things is particularly limited.

Exhibit 3:  Breeding Results When Dam and Sire Temps Vary

 

Dam Temp

 

Sire Temp

Successful

Breedings

Failed

Breedings

 

Percentage

>102.0

<102.0

5

9

36%

<100.0

>100.0

11

6

65%

 

 

 

 

 

<102.0

>102.0

5

4

56%

>100.0

<100.0

5

8

36%

 

It is notable in these limited results that breedings of males with temperatures above 102 degrees to females with temperatures within the normal range (even though many of them were on the higher side of normal) resulted in pregnancies 56% of the time.  By contrast, females with elevated temperatures bred to males with normal-range temperatures conceived only 36% of the time.  Again, caution is warranted because the total number of observations is very small.  But together they do suggest that it is not so much that our males’ fertility is impaired when they are hot, but that our females have trouble either conceiving or holding the pregnancy until it can be confirmed, or both.  Similarly, a cool female (temperature under 100 degrees) conceived 65% of the time when bred to a high or high-normal temperature male (temperature above 100,) while the reverse situation, a cool sire with a warmer dam, resulted in a much lower pregnancy rate. 

Can we ultimately infer more about whether heat interferes with conception, or whether early pregnancy failure is higher when it is hot in weeks after conception (and even before we can confirm pregnancy), or both?  The answer is yes, possibly:  By introducing temperature data (in this case, historical ambient temperatures as we do not routinely take our animals temperatures) for the time between breeding and confirmation, we can examine the relationship between those conditions, the animals’ temperatures at breeding, and the ultimate confirmation rate.    We have noted in years past that we tend to have a higher slippage of confirmed pregnancies when the weather is hot.  Presumably this is also true in the weeks between conception and confirmation of pregnancy.  It will take us a while to discern this in our data, though, even if it is there, because there is a close correlation between the ambient temperatures at breeding and in the early stages of any animal’s pregnancy that will make it more challenging to separate out these two potential effects.   But we are working on it. 

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