Litter Size

• Issue with consistently small litters
• How to get smaller litters

Issue with consistently small litters

Q: Our girl is only producing 3 puppies per litter. This is her second litter and her first was only 3 also. We did progesterone testing and did AI both times at what we thought was the right progesterone levels. We have been working with our repo vet and vet tech also.  

Our girl came from a litter of 7 so we think she is capable of at least that. Any suggestions would be greatly appreciated.

A: I have been dealing with the very same issue recently, and I was very concerned. My girl Claire also comes from a long line of bitches with litters of 8-12. It is the bitch who controls the litter size through the number of eggs released and the environment in the uterus with available “real estate” for egg implantation. So, when I had 2 litters of 3, and then a miss, I wanted to get to the bottom of what was going on as well. I am working with a well-known reproductive veterinarian, and we started with a review of all the documentation that I keep on my girls. I have all the progesterone numbers from each time she was bred, as well as the dates of her heat cycles from her first one. The progesterone numbers for breeding told us that we bred on the appropriate day post ovulation. I would review your progesterone timing, as breeding too early can cause lower litter numbers. Having data on our girls gives us valuable information as it starts to tell a story that helps us get to the bottom of what is going on. We then ran complete bloodwork, including T3 and T4. The bloodwork was unremarkable, with all values in the normal range. Our next diagnostic tool was an ultrasound of the ovaries and uterus. This is where we found our problem. Unfortunately, my girl has one horn of her uterus very crowded with cysts. These cysts have impacted the ability of eggs to implant, and they may also have caused other issues that have contributed to smaller litter size. The cysts that my girl has are so extensive that the Repro. Vet was surprised that she was even able to carry the litter of 3! Because Claire is so valuable to my program, I am working with this vet to attempt one more breeding, and we are going to do a Surgical Artificial Insemenation (SAI). The reason for the SAI is so that the Repro Vet can actually visually inspect the uterus, and deal with the cysts manually. So, my fingers are crossed that in 6 months, I may be able to have a ‘full’ litter of more than 3.

I hope that sharing my experience helps you. I would suggest looking for uterine or ovarian cysts, as they can be the culprit in situations like ours, along with breeding too early in her cycle. One other thing to make sure you check the morphology of the Sire to be. The litter size is also affected by the male in terms of sperm quality, remember it normally takes millions of helper sperm for that one fertilizing speed, and speed DNA health. High DNA fragmentation index in sperm reduces the viability of embryos, increasing resorption rates and stillborns.

How to get smaller litters

Q: I have a 4.5 year old Cavalier. Excellent momma but has very large litters. 7-10! All healthy. Her last whelp 9 weeks ago was 18 hours and 10 pups. Is there a way to manage another breeding in a way that would produce a smaller litter? Like one tie either early or late? Thank you so much!

A: Congrats on the litter sizes you are achieving; many breeders would want to know your secret to larger litters! However, I do understand that large litters like this can take an awful lot out of you and your girl. Managing 7-10 puppies is truly a commitment.

Remember it is the female who determines the litter size, because of the number of eggs that she releases during ovulation. Our goal is to find a way that fewer of these released eggs are fertilized. Breeding either very early, or very late, can definitely reduce the chances of fertilization. We still have to remember that semen, which has not been combined with an extender, will live and be viable for 5-7 days. This is often why people wrongly think she just began her season and “we just had one tie so there will not be puppies,” and then “SURPRISE” you have a litter of 8!

My suggestion is to use progesterone testing, which is the gold standard for timing your breeding. Once you see that she has ovulated by the rise in progesterone numbers, generally, you wait 48hrs for the eggs to mature and these are your prime date(s) for breeding, as you also have to wait for the sperm to capacitate. Capacitation of the sperm is when they undergo changes that must happen for them to penetrate and fertilize the eggs, which takes 24-48hrs. So, my suggestion is to breed late, waiting 4 days to do the breeding not 2. I would also continue to monitor progesterone during the breeding cycle so that you have data. Remember, you may have to balance a litter of 2 versus a litter of 7 as there is no way to predict with accuracy how many she will have if you breed later.

Additional explanation – the LH surge causes ovulation to happen within 2 days. Once ovulation occurs, eggs mature at approx. 60hrs after ovulation (2.5 days) and remain available for fertilization for another approximately 3.5 days at which point they begin to degenerate (6 days post ovulation). This is why breeding later, 4 days post ovulation, gives you pregnancy potential but lower potential than breeding at the optimum timing of 2 days. 

This is a great article on the Veterinary Information Network (VIN). It is more detailed, and I thought you might find it interesting.