07/16/17
Litter Size - Can we predict it?

Litter Size – What the research says

Litter Size - Can we predict it?

There is an ongoing paucity in the literature surrounding most dog matters, and that means dog knowledge is often based on anecdotes and experience instead of facts and figures. Dog breeding is no exception. Breeders will tell you that they get bigger litters if x, smaller litters if y, that they’ll never mate a bitch if z. While personal experiences can provide case studies, I am interested in much bigger data.

Enter a Norwegian study looking at 10,810 litters.

This study used data held by the Norwegian Kennel Club to look at every litter registered in 2006 and 2007, across 224 breeds. Statistical analysis was then done to determine all the wonderful figures summarised below.

The aim of this study was to determine what actually makes a difference in litter size. (Litter size being the number of puppies born, alive or dead.)

Firstly, an overall average had to be determined. For this data set, the average litter size, considering all breeds, was 5.4 puppies.

For those interested in average litter size by breed: The largest average litter size was in the Rhodesian Ridgeback with an average of 8.9 pups per litter. The Toy Poodle and Pomeranian had the smallest average litter size – 2.4 pups per litter. And the Border Terrier (because I’m biased) had an average litter size of 5.1 pups per litter.

This study found that litter size was influenced by the size of the breed, the method of mating, and the age of the bitch. Litter size was not affected by season of birth, or the number of litters a bitch had had.

Size of the breed

This study examined dogs based on average breed size. They were classed as miniature breeds (<5kgs), small breeds (5-10kgs), medium breeds (10-25kgs), large breeds (25-45kgs), and giant breeds (>45kgs). Bitches were recorded against the average size of a dog for their breed and not specifically on the size of that given bitch.

“When looking at all the … litters…, mean litter size increased with the size of the breed. The mean litter size was 3.5 in miniature breeds, 4.2 in small breeds, 5.7 in medium breeds, 6.9 in large breeds, and 7.1 in giant breeds.”

The feature of larger dog breeds having larger litters is not a new thing – this phenomena is consistent across other studies. But this study is different as it found that it wasn’t just size of the breed that mattered…

Age of the bitch

The first analysis of this data showed no significance with the age of the bitch, however, once breed size was taken into account, there were two trends apparent:

  • In small and miniature dogs, young and old bitches had smaller litters than the ages in between.
  • In larger breeds, increasing age corresponded with decreasing litter size. (Young bitches of larger breeds produced the largest litters – unlike small and miniature breeds.)

Predicted litter size by the age of the bitch for the five different breed size groups from Borge et al. study.These results are a little different to other studies, which have shown smaller litter sizes as bitches get older. (As in, the results this study got for larger breeds was seen in all breeds in previous studies.) It could be that smaller sample sizes in other studies may have missed this, or that other studies used larger breeds as their data set instead of small or miniature breeds. One suggestion is that small breeds may not mature as quickly as previously believed, and so they’re not able to reproduce until they reach that mark. (To me, this kind of makes sense – considering small breeds often live longer, then it’s likely that they mature more slowly, too.)

Method of mating

Like the age of the bitch, the first analysis on the data didn’t show a significance change in litter size based on mating method. However, when the data set was adjusted for breed, breed size, and age, naturally mated bitches had significantly larger litters than those who had been AIed (either fresh or frozen).

A decrease in mean litter size of 0.4 puppies would be expected for litters conceived with AI with fresh semen and 1.3 for AI with frozen semen, both compared to natural mating.

Things that didn’t matter

The number of litters a bitch had previously didn’t influence the size of her litter. (However, older bitches normally had had more litters – and their age did influence litter size.)

The season the litter was born in did not influence litter size.

Conclusion

Size of the breed, age of the bitch, and the method of mating are three factors work together in determining litter size. It’s not one thing – it’s all three.

“… the size of the breed, the age of the bitch and the method of mating were found to influence litter size in purebred dogs when controlling for breed, with the size of the breed as the strongest determinant.”

This study is better than past studies in this area for its huge sample size, its variety of breeds, and the fact that it considers all puppies in a litter (not just those registered, as some past studies have done). In this way this study is unique. It is probably a pretty reliable data pool for purebred dogs, too, as 90% of purebred dogs in Norway are registered with their kennel club.

Things to consider regarding the vigour of the results:

  • It’s a retrospective study.
  • It does not include data from litters where all pups were born dead.
  • Calculating mean litter size is hard, because of % made up of small or large breeds. Small breeds are currently popular, so could perhaps pull down the mean litter size seen in this study. Studies done in different countries, with different breeds being popular, is likely to result in different results.
  • There is a relatively small sample of bitches who were mated not-naturally in this study, so the results should be interpreted cautiously, however the results are consistent with previous findings.
  • This study only groups dogs by weight – not by body shape. This might yield differences. (A neapolitan mastiff is really different to a greyhound.) And they group them by weight average of breed, not the weight of the individual bitch
  • This study looked at only two years and the researchers wonder if there might have been more variation in season of birth if there was more time taken into consideration.

In conclusion: Based on this study, breed size is the strongest determinant for litter size in a dog. The age of the bitch and the method of mating were also significant predictors of litter size. These three things interact, making litter size predictions difficult!

Acknowledgements:

Borge, KS, Tonnessen, R, Nodtvedt, A, & Indrebo, A 2011, “Litter size at birth in purebred dogs – A retrospective study of 224 Breeds”, Theriogenology, 75, 911-919.

Thank-you to Waldwiese Kennels for the cover image – a litter of longhair weimaraner puppies.

07/3/17
Canvas art - why you should choose to memoralise your pets with canvas.

Canvas Art for Pets

Canvas art - why you should choose to memoralise your pets with canvas.

The modern way to display art in homes is by canvas. While in the past, framed images have been the fashion, we no longer want our artwork to displayed in boxes on the wall. We like the infinity of canvas – the way there is no end, as though the whole image could consume the world.

The love of images-on-canvas has extended to our pets, too. Many homes are choosing to cover their homes in not just art, but photos of their beloved pets.

Besides the appealing look, there are other benefits to a canvas too:

  • Easier to clean – no glass where fingerprints can be laid, no moulding to attempt to dust in nooks and crannies. With canvas, you can gently vacuum, or use a damp cloth.
  • Easier to transport – no risk of breaking glass, and lighter (and cheaper!) too
  • Less choice – less choice is easier! Of course you can choose to size of your canvas, but you avoid having to make decisions about frames and matt boards.
  • More display options – Canvas can be propped up on shelves easily, while heavy frames risk slipping and could result in broken glass. Also, should the fashion ever change back to frames, canvas can be framed in much the way as flat art. No loss!
  • Cheaper – when you purchase canvas art, you are buying the complete work! No moulding, glass, or hanging guides required, so what you see on check out is what you get.

Recently, I received a canvas from TheCanvasFactory.com.au – an Australian distributor of canvas products. It was super easy to upload an image to the site, and it arrived quickly to my home. However, when it arrived, the image was a little ‘off’ – it seemed blurry in places. I contacted them and they quickly, and without promptly, sent me a second canvas at no cost. THIS one was great! I now have our wedding photo (including dogs, of course – they came to our wedding for photos) on display in our bedroom.

I would very much recommend TheCanvasFactory.com.au if you are looking for canvas products to adorn your own walls. They have good prices, diverse sizes, and great customer service.

A lovely border terrier artwork, on canvas.

A lovely border terrier artwork, on canvas.

01/30/17

Breeding Away from MMVD in Cavalier King Charles Spaniels

Puppy Buyers What You Need To Know about MMVD in Cavalier King Charles Spaniels

ResearchBlogging.orgThe health of many breeds was slammed in the documentary “Pedigree Dogs Exposed”, and one breed that received a barrage of criticism was the Cavalier King Charles Spaniel (CKCS or Cavs).

Heart issues are a problem in Cavs, and it can be fatal. The hearts of all mammals are made of a series of chambers and valves. It is a very synchronised organ and everything needs to work ‘just so’. During one particular condition, myxomatous mitral valve degeneration (MMVD), one of the heart valves ceases to function properly. Overtime, this puts pressure on the rest of the heart, and this leads to chronic heart failure. How individual dogs react to MMVD varies a great deal, and so prognosis after diagnosis is quite variable. The disease often progresses slowly. (If you more detail see this ACVIM factsheet.)

To understand the gravity of this problem, 37% of Cavs that die before 10 years of age do so due to MMVD. (From Swedish insurance data 1995-2006.)

Knowing that there was a problem, the Danish Kennel Club (DKCA) chose to act.

 

The DKCA Breeding Scheme

The DKCA brought in a mandated breeding scheme in 2002-2011, leading to 997 Cavs being examined in those years. Examination include asculation (stethoscope listening) and echocardiography (“echo”, sonograph of heart using ultrasounds) to evaluate the presence of murmurs in any indviidual cav. (Murmurs are predictors of MMVD progression, and have a genetic component.) Each dog was evaluated 1-4 times. There was a total of 1471 exams over the 9 years.

From my understanding, the DKCA required that Cavs be examined after 18 months of age to be approved for breeding. This approval would last until the dog is four years old and, to be bred after four years of age, they had to be re-examined and approved a second time.

To be approved, the dog had to have a MVP grade of two or less, and a mitral regurgitation murmur grade of three or less. If a dog had higher scores, they were excluded from breeding. After 2007, the criteria changed to become slightly more strict. It’s interesting when reviewing the data in this study that the largest number of unapproved dogs occurred in 2007, presumably as a result of this ‘tightening’ of regulations. While this must have been disappointing at the time, it’s a good way for the DKCA to encourage continual improvement without causing a huge reduction in genetic diversity.

The status of each dog examined became published and freely available on the DKCA website.

The DKCA would only register puppies from parents that had fulfilled the cardiac health criteria.

 

How good was the scheme?

This article, published in the Journal of Veterinary Internal Medicine, evaluated the study. Here, comparisons were made between scores of the beginning of the scheme to the end. They also categorised dogs as either approved by the breeding scheme (both dogs tested before mating), or unapproved (one or both parents unknown cardiac status before breeding).

Over the course of the study, they concluded that Cavs were at a 73% decreased risk of developing MMVD.

“A mandatory breeding scheme based on auscultation and echocardiography findings significantly decreased the prevalence of MMVD over the 8- to 10-year period. Such a breeding scheme is therefore recommended for CKCS.”

As a personal comment, I wanted to note that of the 1380 exams that met the criteria of this study, only 78 animals were excluded from breeding.

 

What would be better?

Being able to DNA test for MMVD would be brilliant, but even though we know this condition is highly heritable, DNA markers have not been established. DNA testing is not conceivable in the near future.

“Breeding restrictions or recommendations aimed at decreasing the prevalence of MMVd in CKCS have been developed in breeding clubs in different countries. The high heritability of the disease indicates that section against the disease could be successful.”

This study was retrospective, and only included animals over 18 months of age at their first examination, and excluded animals that were pregnant or lactating. Nine years is a long time, and there could have possibly be variations in scoring over time (despite this studying using clinical observers). A study with a greater sample size with less exclusions and more consistent scoring would always be better, but not necessarily highly achievable.

Interestingly, sometimes dogs can test better if there are changes in the dog. So, a dog’s heart may appear to have a murmur on one occasion, but if the dog changes body condition, heart rate, or both, then the second time the dog is asculated, it may not get the same reading. Therefore, testing dogs on numerous occasions would probably be best for consistency (but a difficult task in reality).

 

What does this mean for puppy buyers?

If you are wanting to add a Cav to your family, when talking to Australian breeders, the recommendations were made that breeders should be:

  • Having their breeding CKCS’s hearts examined annually, preferably by a specialist.
  • Not breeding from dogs that show a heart murmur at five years of age or younger.
  • Not breed any dog until they are 2.5 years old, especially if the parent(s) of the dog have murmur(s).

I asked a couple of Cavalier breeders on their recommendations, and have included them below as a starting guide for puppy buyers.

From Liz at Wandalier Cavaliers:

I think that it’s important to stress that [MVD] does appear to be random. That the level of deterioration, and the age of onset can vary greatly. But basically the later the onset, the better the prognosis. But you can have one dog with a heart murmur, and all the litter mates are fine. There’s also still no known mode of inheritance.

And from Barbara at Karhisar Cavaliers:

An important thing for those wanting to buy cavalier puppies is asking the right questions when contacting breeders. Sire and dam should both hold a minimum of current, clear heart & eye certificates from cardiologist and ophthalmologist. Breeders who are doing the official testing will be only too happy to name the relevant specialists and provide copies of the sire and dam’s health clearances.

When looking for parents who have certification, keep in mind that both parents should be cleared. In this study, there was only a significant reduction in risk for offspring if both parents were approved by the breeding scheme. Half the parents being approved is not good enough.

 

Where to for Cav breeding schemes from here?

While the results from this Danish scheme seem good, and a similar scheme in British showed promise as well, there was another in Sweden that didn’t have a significant effect. So, we can conclude that breeding schemes probably have a role in improving breed health, but exactly what the perfect breeding scheme may be is a bit of an unknown.

However, it is likely that mandatory breeding schemes are likely to be the only ones with oomph to bring about change. Schemes that aren’t mandatory haven’t yielded great results.

It’s important to note that not all heart murmurs are associated with heart disease. 6-10% of Cavs have ejection murmurs, and we shouldn’t exclude those from breeding as this would reduce genetic diversity.

So basically there needs to be further evaluation on ongoing breeding schemes to balance costs and benefits.

 

Reference:
Birkegård, A., Reimann, M., Martinussen, T., Häggström, J., Pedersen, H., & Olsen, L. (2016). Breeding Restrictions Decrease the Prevalence of Myxomatous Mitral Valve Disease in Cavalier King Charles Spaniels over an 8- to 10-Year Period Journal of Veterinary Internal Medicine, 30 (1), 63-68 DOI: 10.1111/jvim.13663

On an unrelated note, Some Thoughts About Dogs was proudly one of the Top 50 Dog Training Blog.

06/14/16

New Research on Early Neutered German Shepherds and Joint Disorders

New Research on Joint Disorders in German Shepherds

 

ResearchBlogging.orgIt’s very exciting how there is growing research on desexing in dogs, including age of neutering, and its implications on health. In the past, I have blogged on how desexing in German Shepherds is linked to reactivity. The latest study, published last month, looks at bone disorders, cancers, urinary incontinence, and pyometra in German Shepherds.

Many of the arguments for desexing dogs has been around population control instead of health matters – but obviously health does matter. We want dogs to be healthy.

This retrospective study looked at the health of 1170 German Shepherds. It included the analysis of vet records over 14.5 years (2000-2014). For each incidence of disease, the dogs’ records were followed for eight years, except in the case of mammary cancer, which was followed for eleven years. The data on the incidence of joint disorders and cancers in the German Shepherds was compared beside their sexes, and their neuter-age.

 

Joint Disorders

The biggest problem with early aged desexing in this breed, according to this study, is an increased risk of joint disorders. For example:

  • 6.6% of intact males had one or more joint disorders, but for dogs that were desexed before 6 months, 20.8% had one or more joint disorder. So joint disorder incidence was three times greater in dogs desexed before 6 months than intact dogs. For dogs that were desexed between 6-12 months, the incidence of at least one bone disorder was 16.4%.
  • Similarly, 5.1% of intact female had one or more joint disorders, but for bitches that were desexed before 6 months the incidence was 12.5%, and for bitches that were desexed at 6-11 months the incidence was 17%.
  • Of the joint disorders considered, Cranial Cruciate Ligament Tear was most highly correlated with early desexing. In entire dogs, hip dysplasia was most commonly seen.
  • For desexed dogs, rates of hip and elbow dyplasia was greater than entire dogs, but this difference was not statistically significant.
  • There was no difference between the body condition scores (i.e. fatness) between entire and neutered populations – so it’s not obesity that has caused these problems.

 

But why do German Shepherds have an increased incidence of joint disorders when they’re desexed before one year of age?

If a dog is desexed before one year of age, the growth plates of the dog are unlikely to have closed. (That is, the bones are still growing.) With the removal of hormone cues through the removal of gonads, the bones are likely to grow longer than they ‘should’, which disrupts joint alignment. This disruption leads to joint disorders such as those found in this and similar studies.

However, this research did not just look at bone disorders.

 

Cancer

Unlike previous studies on cancer in other breeds, there was no statistically significant differences between neutered and entire animals. However, in terms of mammary cancer (which was only considered in bitches), 4% of intact females got mammary cancer, but <1% got mammary cancer if desexed before one year of age. The paper notes that mammary cancer seems to be uncommon in German Shepherds and refers to a recent meta-analysis that found the protective factor of neutering in terms of mammary cancer to be weak.

In terms of other cancers there was no significant differences. (My own note though: This study found that only 14% of the entire bitches were used for breeding. Lactating is a protective factor against mammary cancer, so I would suspect that if more of these bitches were breeding bitches, the rate of mammary cancer may have been lower again.)

 

Bitch-Specific Conditions

Urinary incontinence was seen at a rate of 7% in neutered bitches, but was not seen at all with entire bitches. (Urinary incontinence was not considered in males.) The mean age of onset of urinary incontinence in early neutered females was 5.2 years.

Pyometra in intact females was seen as a rate of 2.5%.

How does this compare to other research?

It’s important to note that this new data adds to our growing understanding of desexing implications. This study references:

  • A 2014 study saw that Golden Retrievers and Labrador Retrivers were, generally, more likely to have a joint disorder the earlier they were desexed.
  • A 2013 study saw that Golden Retrievers that were early desexed had more hip dysplasia, cranial cruciate ligament tears, and lymphosarcoma. Desexing, regardless of time, increased the rate of at least one cancer by 3-4 times.
  • Another 2013 study found that, in Vizslas, the incidence of cancers was high in desexed dogs (except mammary cancer – where incidence was low).
  • Another 2013 study found that neutered male and female dogs were more likely to die of cancer than intact dogs.
  • A 2011 study that found that, in several breeds, the incidence of mast cell tumours was four times greater in spayed females as opposed to intact.
  • A 2008 study that saw that desexing before 12 months of age saw joint disorders (such as hip dysplasia, cranial cruciate ligament tears, and elbow dysplasia) occuring at 2-3 times higher rates than in intact dogs.
  • A 2007 study linked early desexing with risk factors for cranial cruciate ligament tears.
  • A 1999 study found that cardiac hemangiosarcoma was four times more common in spayed females than those intact.
  • A 1998 study, looking at several breeds, saw that osteosarcoma was two times more likely in neutered dog compared to intact dogs.
  • A 1988 study that found that splenic hemangiosarcoma was two times more likely in spayed females than intact.

The researchers involved with this study have been adding great data to the neutering/spaying discussion. They have previously published articles on Labrador vs Golden Retrievers and Golden Retrievers, and these articles had similar findings. (Though German Shepherds did not seem to be as cancer prone as the Golden Retrievers.) As all these studies are using vet clinic data, it is not known how similar or dissimilar the strains/lines are – so the sample could be genetically diverse despite being the same breed.

But it seems that, for German Shepherds, it is far better to wait until dogs are twelve months or older before desexing, if desexing is chosen at all. I’ll end on a quote from the paper:

As shown in this study, delaying neutering until the dog is at least a year of age appears to avoid the increase in risks of joint disorders is associated with neutering. This is a consideration for joint disease control that is immediately available.

 

Reference:
Hart, B., Hart, L., Thigpen, A., & Willits, N. (2016). Neutering of German Shepherd Dogs: associated joint disorders, cancers and urinary incontinence Veterinary Medicine and Science DOI: 10.1002/vms3.34

 

Further Reading:

Early Neutering Poses Health Risks for German Shepherd Dogs, Study Finds

A Link Between Desexing and Reactivity

Labs and Goldens: Goldens Get Cancer Better

Desexing: It’s bad for Vizslas, too

But Mammary Cancer!

Why would you NOT desex your dog?

03/3/16

Photographic Guide to Saving Swimmer Puppies

Saving a swimmer puppy

 

 

I’m proud that, for a number of years, the most popular post on this blog is ‘How to Save a Swimmer Puppy‘. However, I am frequently asked for photographs to illustrate the techniques I mentioned. I have recently had a litter of puppies, so I could stage images showing techniques on young puppies for saving a swimmer puppy.

 

Sling Method

This is by far the most simple method. I use a pillow case, suspended from the back of a chair, and then the puppy is placed inside the pillow case, meaning the puppy is basically in a hammock. When the puppy is placed in the hammock, is important that their legs are tucked underneath them, or the puppy is on their side.

It’s important that the puppy is not allowed to get cold while in this sling, too. You can warm the material of the hammock before placing the puppy inside, and then you can also put a heat pack underneath, on the ground, too (as hot air rises).

You can do this several times a day, ensuring that the puppy stays warm and gets plenty of time to feed in between its time in the sling. Puppies are surprisingly tolerant of this process and rarely object when their stomach is full and their a good temperature.

This is a (zebra-print) pillow case that is suspended on the back of a red chair. Inside, is a baby puppy.  This process will help to fix swimmer puppies.

This is a (zebra-print) pillow case that is suspended on the back of a red chair. Inside, is a baby puppy.
This process will help to fix swimmer puppies.

A puppy (little black blob at the bottom) in a suspended sling. This will help puppies recover from swimmer syndrome.

A puppy (little black blob at the bottom) in a suspended sling. This will help puppies recover from swimmer syndrome.

 

 

Handcuff Method

Using electrical tape, you can create handcuffs that pull the puppies legs inwards, preventing them flailing out to the side as a swimmer. It’s important when using this method that you don’t do it too tight. (To be honest, when I’ve used this method, I’ve had it fall off numerous times a day because of how loose I make it. Fine by me!) You also want to make sure you don’t put too much length between the cuffs – remember the cuffs are supposed to pull the pup’s legs inwards, so if you make the cuffs too long, then the puppy’s legs are still going to be able to swim.

Tools required for the handcuff method: Electrical tape and a pair of scissors!

Tools required for the handcuff method: Electrical tape and a pair of scissors!

Step one: Cut a length of tape. We only need one length of tape, and the exact length will depend on your puppy and how far east west its legs are.

Step one: Cut a length of tape. We only need one length of tape, and the exact length will depend on your puppy and how far east west its legs are.

Step three a: Make one loop of the handcuffs. (This image is for illustration purposes - in reality you'd need the puppy's leg in that loop!)

Step two a: Make one loop of the handcuffs. (This image is for illustration purposes – in reality you’d need the puppy’s leg in that loop!)

 

 

 

 

 

 

 

 

 

Step three b: Make a second loop of the handcuffs. (Photo for illustration purposes - in reality, there would be a puppy with a leg through each loop!)

Step two b: Make a second loop of the handcuffs. (Photo for illustration purposes – in reality, there would be a puppy with a leg through each loop!)

I’m sorry that I am not much of a photographer, but here are some pictures to try to illustrate how these handcuffs look actually on a puppy.

A puppy in swimmer handcuffs.

A puppy in swimmer handcuffs.

A puppy in swimmer handcuffs.

A puppy in swimmer handcuffs.

A puppy in swimmer handcuffs.

A puppy in swimmer handcuffs.

The benefits of the puppy handcuffs is that they can stay on for long periods of time, and the puppy can still feed and cuddle mum and litter mates while wearing them. Sometimes mothers will remove the handcuffs, and sometimes they fall off, so you are likely to have to put on new handcuffs several times a day. Initially, for a severely affected puppy, you may need to start with long handcuffs then reduce the distance between the handcuffs over time. Puppies are surprisingly tolerant of the handcuffs and rarely fuss once they’re on and they’re back at the milkbar!

 

For more tips please do see How To Save a Swimmer Puppy.