Any research into predicting birth weight of lambs

[Devil's advocate]

My fault entirely, some of our lambs have been too big this year. Causing pain for ewes, lost some lambs, extra antibiotic use, some prolapses etc.

Predictable, never had so much winter grass, drier than average winter, plenty of veg waste to feed & no wastage of nuts when feeding ewes on the floor. Hay likly better than average too.

Never fed less hay & concentrates but still fed too much.

Is it possible to be scintific about this & scan for litter number (well yes thats easy) then weigh, condition score ewes through the season with EID tags to build up a graph on a computer. Analise feed of course & try to factor in weather conditions.

If I had all that information I would be none the wiser. But there must be a correlation with weight gain over winter & weight of lambs?

I don't have the numbers but total mixed ration addlib tweaked to the correct balance of nutrients must be the way to go.

 

[Farmer Fin]

Think a lot of foetal size is set in the first trimester when placenta is developing. Better nutrition gives better placenta and better grown lambs.

 

[Devil's advocate]

Think a lot of foetal size is set in the first trimester when placenta is developing. Better nutrition gives better placenta and better grown lambs.

Yes I agree.

Just when it is hardest to control net nutrition.

Some of my ewes skin & bone put everything into producing large lambs.

 

[Bury the Trash]

Also I would suggest Less good feed required mid term. And leave main concrete feeding till later , ie last 3 or even 2 weeks ..... just a suggestion.....

Concrete

Just read they are just skin and bone .....that doesn't really add up if they've been overfed ll the way through

I'm gonna have to giv up typing with this thing

 

[Devil's advocate]

Also I would suggest Less good feed required mid term. And leave main concrete feeding till later , ie last 3 or even 2 weeks ..... just a suggestion.....

Concrete

Did not start feeding concentrates until two weeks before lambing, its the stragglers which are the main problem. I suppose we should use raddle.

 

[tepapa]

Restrict feed and lambs will get smaller after a few days, will help the late lambers.

We need @Global ovine for a definitive answer.

 

[Devil's advocate]

Also I would suggest Less good feed required mid term. And leave main concrete feeding till later , ie last 3 or even 2 weeks ..... just a suggestion.....

Concrete

Just read they are just skin and bone .....that doesn't really add up if they've been overfed ll the way through

I'm gonna have to giv up typing with this thing

It does they have developed a big demanding placenta, which is taking all the nutrients.

What set this thread off was a 90kg ewe last night two huge lambs nearly 35Ib weight combined & the ewe is just skin & bone. The lambs died too long coming, but ewe has recovered & is rearing a foster lamb.

 

[Bury the Trash]

As mentioned a time or to on the forum gestation length ..(Ram). even a couple of days or sk extra in the womb on good feed could cause problems especially if that coincided with a few slightly narrowoer pelvis ewes

 

[Bury the Trash]

It does they have developed a big demanding placenta, which is taking all the nutrients.

What set this thread off was a 90kg ewe last night two huge lambs nearly 35Ib weight combined & the ewe is just skin & bone. The lambs died too long coming, but ewe has recovered & is rearing a foster lamb.

Milk yield is ok then

 

[Devil's advocate]

Milk yield is ok then

Yes very good. I would say best milk yeild I've known.

 

[tepapa]

It does they have developed a big demanding placenta, which is taking all the nutrients.

What set this thread off was a 90kg ewe last night two huge lambs nearly 35Ib weight combined & the ewe is just skin & bone. The lambs died too long coming, but ewe has recovered & is rearing a foster lamb.

As I understand it, reduced feed in mid trimester diverts energy to develop the placenta. Which is normally a good thing as you can underfeed mid pregnancy (usually in deepest winter to save on feed) but it also benefits lamb survival as lambs are born bigger if fed correctly later on.
Well fed ewes throughout pregnancy can produce small lambs, as is seen in fattening Hogg's which become pregnant but give birth to small lambs even though they have been fed well.

By your description of a lean ewe and big lambs, it would fit that they have been underfed for a period ,which has developed a good sized placenta, and through good late pregnancy feeding has produced big lambs.
Edit: which is also why you can't add condition on ewes in last trimester as they will use the energy to grow the fetus, not to increase body weight.

 

[Bury the Trash]

But the op says they have had it good all the way through.

 

[tepapa]

But the op says they have had it good all the way through.

He also says the 90kg ewe was skin and bone.
It's either underfed or I'll.

 

[Bury the Trash]

Think a lot of foetal size is set in the first trimester when placenta is developing. Better nutrition gives better placenta and better grown lambs.

Yes, poor at that time and lambs will be smaller no matter what feed they get later on which can explain the opposite ie fat ewes and less and tiddly lambs cant win ir and its luck and weather... which we cant predict ... is the only difference a lot of the time

 

[neilo]

My fault entirely, some of our lambs have been too big this year. Causing pain for ewes, lost some lambs, extra antibiotic use, some prolapses etc.

Predictable, never had so much winter grass, drier than average winter, plenty of veg waste to feed & no wastage of nuts when feeding ewes on the floor. Hay likly better than average too.

Never fed less hay & concentrates but still fed too much.

Is it possible to be scintific about this & scan for litter number (well yes thats easy) then weigh, condition score ewes through the season with EID tags to build up a graph on a computer. Analise feed of course & try to factor in weather conditions.

If I had all that information I would be none the wiser. But there must be a correlation with weight gain over winter & weight of lambs?

I don't have the numbers but total mixed ration addlib tweaked to the correct balance of nutrients must be the way to go.

All (or most) Signet recorded flocks are recording birth weights, and have been for many years. That data will be used to produce an ebv for birth weight. I think it’s coming in as part of the changes to the analysis this Spring.

Of course nutritional management plays a massive part, but genetics will determine differences given the same nutritional management.

 

[puppet]

He also says the 90kg ewe was skin and bone.
It's either underfed or I'll.

A 90kg ewe at skin and bone must be the size of a small pony.
The placenta mainly develops mid pregnancy and most lamb growth is in last 50 days. Big lambs suggest too much feeding then. Likewise you can still reduce it now and give enough to avoid TLD.
Plenty advice available about weight gain or loss and effect on lamb size. The other option is just to put a hand on them 6 weeks before and feed in groups. Never an exact science but a reasonable guide

 

[Global ovine]

My fault entirely, some of our lambs have been too big this year. Causing pain for ewes, lost some lambs, extra antibiotic use, some prolapses etc.

Predictable, never had so much winter grass, drier than average winter, plenty of veg waste to feed & no wastage of nuts when feeding ewes on the floor. Hay likly better than average too.

Never fed less hay & concentrates but still fed too much.

Is it possible to be scintific about this & scan for litter number (well yes thats easy) then weigh, condition score ewes through the season with EID tags to build up a graph on a computer. Analise feed of course & try to factor in weather conditions.

If I had all that information I would be none the wiser. But there must be a correlation with weight gain over winter & weight of lambs?

I don't have the numbers but total mixed ration addlib tweaked to the correct balance of nutrients must be the way to go.

@Devil's advocate:
Several issues arise in your situation and questions and some have been commented on above, so I will give a brief but broad brush answer/comment to those I think I can see in your opening post.

• Feeding to control lamb birth weight is not the same as feeding to maintain ewe body condition (BCS) as both have different goals.
• Sire breed of foetuses controls gestation length. Texels can be "in the oven" for about a week longer than some breeds. Like timber trees that put on their highest rates of timber volume in the last years of their rotation length, so do lambs put on their greatest weight gain in the last few days pre birth. Breeds that are renowned for ease of birth usually have shorter gestation length. All breeds can have a wide spread of leaving gestation length variability, but breed averages show where most are, so selection against large birth weights can be easily achieved. Another reason to pick your ram breeder before you pick the ram.
  
• Adequate ewe nutrition levels to maintain BCS in the first trimester is necessary for foetuses to access good nutrition transfer via placental development to reach birth weights which have greatest chance of survival in twins and triplets.
• Fat ewes have more lambing difficulties and metabolic problems than ewes in store condition. Ewes below store condition have reduced lactation peaks and duration as well as having less survival in multiples.
  
• Lowered ewe nutritional levels in the second trimester are advantageous to the ewe if BCS is not lowered by more than one condition score. This kicks the ewe's system into gear to mobilise Ca in the 3rd trimester to help prevent Milk Fever and Vagina Prolapse. More BCS loss during the 2nd trimester will increase chances of Twin Lamb Disease leading to Ketosis as ewes carrying big loads of multiples have massive transfers of protein in the last stages of pregnancy. Basically, one can't feed multiple bearing ewes enough energy in late pregnancy, whereas the size of singles can be roughly controlled by controlling energy intakes of ewes as protein complications rarely occur in singles.
  
• A proficient scanner can count 0, 1, 2, 3, etc. although the larger the litter, the longer it takes to find and count all present. Some ewes may lose a twin or triplet that was counted as it has been resorbed (not re absorbed as it only happens once) when a foetus attached to a poor nutrition site in utero snuffs out. These are sometimes seen as pus balls in the afterbirth. However the scanner should mark the ewe according to the litter size for the farmer to feed each mob accordingly.
  
• Forget weighing ewes once they have reached their mature body weight/size. Weighing for management purposes is only useful in growing animals. Mature reproductive females only need BCS monitored to achieve targets at weaning, mating, preg. scanning and about a month prior to lambing, as these are the crucial times indicating if nutritional levels need adjusting to attain a good desired level of performance. Graphing these annually can be of considerable help in managing performance, seasonal feed budgeting and future planning.
  
• There is a strong correlation between average mature ewe frame size and average lamb birth weight per litter size, but that is self regulating. There is up to a 20% variation in ewe pelvic aperture within breeds where selection for easy birth has been undertaken. repeat of comment about the ram breeder. Pelvic angle in the dam further complicates the birth process especially in blunt broad headed/shouldered breeds.
  
• It is difficult to control litter size by weighing ewes as their size can vary according to their nutrition over their 1st (growing) years. BCS of a consistently bred line of ewes will indicate the approximate scanning rate if disease or ram failure doesn't factor. However there is a wide variation between sires for embryo survival (60 -98%) which can add variability to scanning rates and lamb deaths around lambing that will be of a similar magnitude. All this adds variability before birth weight.
  
• When breeding from ewe lambs, which work to very different rules to those governing adult ewes, increasing ewe body weight should be the aim. Those scanning with singles can be held back in the last month to prevent a large number of too heavy birth weights. Ewe lambs carrying twins should be fed on a high energy regime.
• All lactating females should be fed high allocations of pasture once lambed as the 1st 6 weeks is all about lactation. Sheep farmers are dairy farmers over that time. A kilo of pasture DM is much more valuable after lambing than before.

 

[Devil's advocate]

Thank you very much Global ovine.

Although there is one point, that I still think has potential.

If all ewes are weighed at mating & at 2 or 3 intervals whilst pregnant.

This may identify ewes which are dominating the feed trough & related to scanning result they may be better seperated from the flock & put on a lower plane of nutriction. Modern EID tagging, weigh scale tag readers & drafting gates makes this a simple task.

ps Lambing back on track again, still bigger lambs than normal though.

 

[farmerm]

Yes I agree.

Just when it is hardest to control net nutrition.

Some of my ewes skin & bone put everything into producing large lambs.

I second that, my thinnest ewes are producing twins that are much better lambs than the singles coming off better condition ewes

 

[andybk]

@Devil's advocate:
Several issues arise in your situation and questions and some have been commented on above, so I will give a brief but broad brush answer/comment to those I think I can see in your opening post.

• Feeding to control lamb birth weight is not the same as feeding to maintain ewe body condition (BCS) as both have different goals.
• Sire breed of foetuses controls gestation length. Texels can be "in the oven" for about a week longer than some breeds. Like timber trees that put on their highest rates of timber volume in the last years of their rotation length, so do lambs put on their greatest weight gain in the last few days pre birth. Breeds that are renowned for ease of birth usually have shorter gestation length. All breeds can have a wide spread of leaving gestation length variability, but breed averages show where most are, so selection against large birth weights can be easily achieved. Another reason to pick your ram breeder before you pick the ram.

thats very interesting , i put a charollais in with my bottom end zwartbles last autumn at the same time as i tupped the pures , in the next field , they were all together pre tupping.
nearly all the charollais x have lambed already , to the point i was wondering if the ram had got in with the other group . till i checked the numbers , the pures are 1-2 weeks behind i recon (havnt had a pure one yet )