Litter size and genetics

[Skai]

I was off breeding rabbits for several years and got back into it three years ago. I currently have three does and one buck, all NZ/Cali crosses. Healthy, at a good weight, and fed a quality organic pellet. I don't over-breed or breed in severe weather, so no real stresses. When breeding the same cross in the past I'd get 8-9 kits regularly. With this group I've never gotten more than four or five kits, which I don't consider acceptable for a meat herd. The question is, could the low birth rate be poor genetics on the buck's side, or should I just start over completely with a new group. Opinions would be appreciated.

 

[olhippityhop]

Are the Does related? If they are, I'd lean towards them being the problem. Personally I'd start with Purebred rabbits and go from there.

 

[Alaska Satin]

I was off breeding rabbits for several years and got back into it three years ago. I currently have three does and one buck, all NZ/Cali crosses. Healthy, at a good weight, and fed a quality organic pellet. I don't over-breed or breed in severe weather, so no real stresses. When breeding the same cross in the past I'd get 8-9 kits regularly. With this group I've never gotten more than four or five kits, which I don't consider acceptable for a meat herd. The question is, could the low birth rate be poor genetics on the buck's side, or should I just start over completely with a new group. Opinions would be appreciated.

In my experience, litter size does tend to run in genetic lines, but not always due to the buck. Although it certainly could be your buck if all three does are having the same problem, I've never culled a buck for litter size issues. In my experience, my bucks' production varies from doe to doe. I guess if I was having this problem but I liked the does otherwise, I might try to "borrow" a buck and see if the does perform differently, before I started over from scratch.

How closely related are your does? And what age? I expect smaller litter sizes once does reach 3 or 4 years old, especially if they've been in production the whole time. I do see strong tendencies to have larger or smaller litters in the different matrilineal lines in my barn. And while production drops over a doe's lifetime, another thing I've noticed is that does from the big litter line (14-16 kits per litter during their first year in production) tend to age out faster. Most of them are down to 3-4 kits per litter by the time they are three, whereas does from the more typical litter size lines (7-9 per litter) sometimes still have close to the same number at 3 to 4 years old.

However, litter size can also be related to diet, which can be tricky to determine since most of us don't get to see what's going into the pellets or how they're stored. The rabbits in my barn are just recovering from a horrible year of production; I belatedly discovered they were suffering from not only a vitamin E deficiency but also some as-yet-undetermined issue(s) with the pellets. These pellets were no corn, no soy, organic, looked and smelled great, rabbits liked them... But I can't really name a problem I have not seen in the last 12 months, which coincides exactly with my shift to this brand. Much of the trouble was reproductive: missed conceptions, false pregnancies, litters of 2-4, giant stillbirths, at least one or up to the entire litter being stillborn. All of these issues have tapered off quickly since I switched back to Nutrena. What I had been using for the last year was being brought up by a local feed store from a mill in the Lower 48, I do not know which mill. I might have blamed the rabbits (actually I did butcher a few of them ), but I have had some of these rabbit lines for many generations and knew what I should be seeing from them.

This is the second time I've been through "pellet problems." The first time was with a locally milled brand that served me well for about six years until I started having failures similar to what I've had in the past year. That one was simply vitamin E deficiency, solved by supplementation before I could switch feeds. My point is that a brand that has been great can go wrong without warning, due to changes in ingredient quality and/or sourcing, processing, formulation, storage or transport, among many other possibilities.

Do you have any way to find out the history of your does, or the typical performance of the lines they came from?

Incidentally, the rabbits I did butcher for poor reproduction all had problems with their reproductive tracts, including mummified pregnancies, empty gestational sacs filled with fluid rather than embryos, and tumorous masses in their ovaries, fallopian tubes and/or bladder. The one buck we butchered had numerous lipomas and tremendous vascularization within the tissue of his belly skin. I have never seen any of these issues in my rabbits in nearly two decades of working with these lines. So if you do start over, definitely investigate what might be going on internally!

 

[Skai]

In my experience, litter size does tend to run in genetic lines, but not always due to the buck. Although it certainly could be your buck if all three does are having the same problem, I've never culled a buck for litter size issues. In my experience, my bucks' production varies from doe to doe. I guess if I was having this problem but I liked the does otherwise, I might try to "borrow" a buck and see if the does perform differently, before I started over from scratch.

How closely related are your does? And what age? I expect smaller litter sizes once does reach 3 or 4 years old, especially if they've been in production the whole time. I do see strong tendencies to have larger or smaller litters in the different matrilineal lines in my barn. And while production drops over a doe's lifetime, another thing I've noticed is that does from the big litter line (14-16 kits per litter during their first year in production) tend to age out faster. Most of them are down to 3-4 kits per litter by the time they are three, whereas does from the more typical litter size lines (7-9 per litter) sometimes still have close to the same number at 3 to 4 years old.

However, litter size can also be related to diet, which can be tricky to determine since most of us don't get to see what's going into the pellets or how they're stored. The rabbits in my barn are just recovering from a horrible year of production; I belatedly discovered they were suffering from not only a vitamin E deficiency but also some as-yet-undetermined issue(s) with the pellets. These pellets were no corn, no soy, organic, looked and smelled great, rabbits liked them... But I can't really name a problem I have not seen in the last 12 months, which coincides exactly with my shift to this brand. Much of the trouble was reproductive: missed conceptions, false pregnancies, litters of 2-4, giant stillbirths, at least one or up to the entire litter being stillborn. All of these issues have tapered off quickly since I switched back to Nutrena. What I had been using for the last year was being brought up by a local feed store from a mill in the Lower 48, I do not know which mill. I might have blamed the rabbits (actually I did butcher a few of them ), but I have had some of these rabbit lines for many generations and knew what I should be seeing from them.

This is the second time I've been through "pellet problems." The first time was with a locally milled brand that served me well for about six years until I started having failures similar to what I've had in the past year. That one was simply vitamin E deficiency, solved by supplementation before I could switch feeds. My point is that a brand that has been great can go wrong without warning, due to changes in ingredient quality and/or sourcing, processing, formulation, storage or transport, among many other possibilities.

Do you have any way to find out the history of your does, or the typical performance of the lines they came from?

Incidentally, the rabbits I did butcher for poor reproduction all had problems with their reproductive tracts, including mummified pregnancies, empty gestational sacs filled with fluid rather than embryos, and tumorous masses in their ovaries, fallopian tubes and/or bladder. The one buck we butchered had numerous lipomas and tremendous vascularization within the tissue of his belly skin. I have never seen any of these issues in my rabbits in nearly two decades of working with these lines. So if you do start over, definitely investigate what might be going on internally!

Thank you for your lengthy reply. I bought two of the does and the buck when they were about 6 months old so they are now going into their third year. I was "guaranteed" (?) they were from different litters/different does. Unfortunately the breeder I bought them from has relocated and I no longer have his contact information. The third doe I have is one I kept from one of the original does I bought. None have had conception issues. One breeding and they're pregnant and they kindle on time, all three very consistently delivering 4-5 kits. All of the grow-outs have had very healthy organs and good butchered weight. I don't over-breed them. I consider them to be a backup source of meat in case of a shortage so I only breed a two or three times a year just to keep them fertile.

The feed I've had them on consistently since I got them is GMO free, Modesto Milling Organics,. I've attached a copy of the package label. It appears to be a quality feed and contains a range of supplements including vitamin E. No corn or soy. I've done some extensive research and can't find any problems others may have had that would be associated with the feed, and I really don't feel comfortable with any feed that could contain genetically modified ingredients. They are in comfortable, stress free housing. Not exposed to excessive heat or cold.

I guess I was lucky when I was breeding before because I don't show and I really don't have an eye for body types. I just want a meat rabbit that will give me decent sized litters.

If I understand your comments and can rule out a feeding problem, the fact that they are not bred too often, and have all been consistent in the number of kits kindled from the beginning, do you think that the problem may be breeders that are too closely related? If so, I think my first step may be to try an unrelated buck.

 

[Skai]

Are the Does related? If they are, I'd lean towards them being the problem. Personally I'd start with Purebred rabbits and go from there.

Do you mean related to each other or to the Buck? What do you mean purebred, either NZ OR Cali, because they are a cross of those two. And if you mean are they related to the Buck wouldn't it be easier to replace one buck rather than three does?

 

[olhippityhop]

Do you mean related to each other or to the Buck? What do you mean purebred, either NZ OR Cali, because they are a cross of those two. And if you mean are they related to the Buck wouldn't it be easier to replace one buck rather than three does?

I was asking if the does are all related to each other, which it sounds like they probably are. Purebred as in something with a pedigree. Without a pedigree you have no idea what's really mixed in there. The bloodline you have might just produce small litters. I like Alaska Satin's idea of trying to "borrow a buck" and see if you get different results.

 

[Alaska Satin]

Thank you for your lengthy reply. I bought two of the does and the buck when they were about 6 months old so they are now going into their third year. I was "guaranteed" (?) they were from different litters/different does. Unfortunately the breeder I bought them from has relocated and I no longer have his contact information. The third doe I have is one I kept from one of the original does I bought. None have had conception issues. One breeding and they're pregnant and they kindle on time, all three very consistently delivering 4-5 kits. All of the grow-outs have had very healthy organs and good butchered weight. I don't over-breed them. I consider them to be a backup source of meat in case of a shortage so I only breed a two or three times a year just to keep them fertile.

The feed I've had them on consistently since I got them is GMO free, Modesto Milling Organics,. I've attached a copy of the package label. It appears to be a quality feed and contains a range of supplements including vitamin E. No corn or soy. I've done some extensive research and can't find any problems others may have had that would be associated with the feed, and I really don't feel comfortable with any feed that could contain genetically modified ingredients. They are in comfortable, stress free housing. Not exposed to excessive heat or cold.

I guess I was lucky when I was breeding before because I don't show and I really don't have an eye for body types. I just want a meat rabbit that will give me decent sized litters.

If I understand your comments and can rule out a feeding problem, the fact that they are not bred too often, and have all been consistent in the number of kits kindled from the beginning, do you think that the problem may be breeders that are too closely related? If so, I think my first step may be to try an unrelated buck.

With all of that background information, it starts to sound like it could well be the buck, especially if the does are unrelated. Even if the two new does and the buck are related, your third doe from an original doe you had would likely be less related, if I'm reading your reply correctly. If your "original" doe, the mother of the third rabbit you have, was also from the same breeder, that might change the relatedness picture.

In any case, there are generally two negative results that can come come from inbreeding: inbreeding depression, and the doubling up of lethal recessive alleles or the increase of other alleles that produce undesired traits. Inbreeding depression doesn't usually show up for many generations. And even if your buck and does were very closely related, if the problem is inbreeding depression, you'd most likely be having other problems besides just small litter sizes.

If your brood stock is crossbred, they're not going to be horribly inbred even if they all came from the same litter, given that Cals and NZs should not bring identical genetic material to the table. But the other problem - increasing frequencies of negative traits - might be an issue, and that can happen just as easily with an outcross as with linebreeding. Some of the worst problems I've had (malocclusion, GI problems) came when I used imported stock with my standing lines of Satins. Some lines just don't play well together. In fact that's why I prefer to linbreed almost exclusively: over time, I weed out the bad stuff, and know what to expect in the litters, so I generally know exactly who the problem is coming from when I see negative results.

The simplest and cheapest thing would be to try a different buck in the next round of breeding, but I would also consider replacing one or two of the does if they're going into their third year. You might be able to shop around for a breeder that is more forthcoming about the production of his or her stock. But I probably wouldn't replace all of the does. IMHO, experienced, reliable mothers are worth having around even if they don't produce large litters!

 

[Skai]

I was asking if the does are all related to each other, which it sounds like they probably are. Purebred as in something with a pedigree. Without a pedigree you have no idea what's really mixed in there. The bloodline you have might just produce small litters. I like Alaska Satin's idea of trying to "borrow a buck" and see if you get different results.

Yes, you are right. The does are not from the same litter but are probably related by mother or father. I am probably going to try to find a "loner" buck. Thanks for the response.

 

[Preitler]

......
None have had conception issues. One breeding and they're pregnant and they kindle on time, all three very consistently delivering 4-5 kits.
......

One thought there, since rabbits are induced ovulators I would try more than one breeding first. Compared to sperm count the number of released eggs is minimal. Maybe he just doesn't get them in the right mood.

 

[tambayo]

From what i see number of kits depends on the doe, not the buck.

 

[Skai]

From what i see number of kits depends on the doe, not the buck.

I would have to agree with you if it wasn't all three doe's.

 

[Skai]

One thought there, since rabbits are induced ovulators I would try more than one breeding first. Compared to sperm count the number of released eggs is minimal. Maybe he just doesn't get them in the right mood.

When I was raising rabbits about 30 years ago (Pure NZ Rew) I only watched for one fall-off and the does delivered 8 to 9 kits regularly. That has me thinking it may be breed or lineage dependent.