I have been working a lot with the sheep ration calculation program created by Montana State University. This is a really nice, free, online too for doing feed nutrient balancing for sheep of all stages of life. You can do this by hand using the Pearson Square method, but the online tool is easier, especially when combining more than two feedstuffs.
This is where it really helps if you can buy hay that comes with a lab analysis. If you don’t have this, you can still tinker with the tool, as it has a lot of generic feed profiles to choose from. But, you are guessing, so at most, you can do a best- and worst-case analysis of what your animals might be getting, and try to shoot for the high side with supplementation.
Here is a look at my hay, just by itself, in how it would serve my ewes in late gestation. This is for adult ewes weighing 154 lbs, pregnant with twins, and assuming I could get them to eat 4% of their bodyweight, or about six pounds of hay day.
If you blow it up a little (click on the image if you can’t see), you can see that the ewes would barely be skimming by on dry matter intake, digestible energy (DE), metabolizable energy (ME), and total digestible nutrients (TDN). This waters down to meaning they are taking in enough calories. But, the crude protein (CP) is too low, which would compromise lamb size and health. This tool doesn’t have a profile for ewes pregnant with triplets or quads, so I have to consider that some of my ewes will need even more than this profile requires. And, I know that my ewes may have trouble taking in that much hay, especially the ones pregnant with triplets, because there is diminished room in their abdomens, and they tend to feel full quickly.
Currently, the sheep are eating (and wasting) about 3.2 pounds of hay a day per head, just as they are entering the mid-gestation phase. This is as much as they are willing to eat, if I feed them more, they just make a bed out of it. 
If I assume their appetites will increase to four pounds per day, and I add some grain, along with my mineral supplements, this looks a little better:
I still worry that this is a little lean for ewes bearing triplets, but that is the disadvantage of feeding a mob. If I could ultrasound the ewes and separate them by the number of fetuses they were carrying, I could feed each group more precisely. But as it is, the ewes with twins will be fed optimally, the ones with singles will be over-fed, and the ones with litters will be under-served.
The ewelambs have a similar picture:
Interestingly, data on ewelambs specifies that they require a similar diet to the mature ewes. Despite the mature ewes weighing almost twice as much, ewelambs are still growing, so they need extra calories, and a lot more protein. This diet is very close to the minimum of protein for them, and it is maximizing the amount of grain I can give them. So, it’s clear why so many people choose to incorporate soy protein into animal diets- it is astronomically higher in protein than whole grains. (Soybean meal is about 50% protein, whereas the corn and barley I am feeding are lucky to hit 10%.) So despite some consumers now thinking soy is evil, it is a very cost-effective foodstuff for animals. So far, I am trying to stick to “rolled” (crushed) whole grains, rather than processed soy protein, because there is some research that implies that it promotes a healthier rumen. But it costs more…
The other fun fact that emerges in these numeric grids is how the mineral supplements contribute to the diet. You can see that my copper supplementation is about double what they are getting in the hay, so not shockingly large, even though I’m using a cattle supplement. Iron amounts are huge, nearly two thousand times the minimum required, so I am still a little puzzled why my sheep livers are testing deficient here. And the kelp offers pretty meager amounts of all of the “big” minerals. I’m still torn on its advantages- it is a very expensive way to deliver minerals, but it does have a lot of the “fringe” minerals that don’t appear in feed profiles or nutrition studies, that nobody knows about. And the sheep definitely love it. So I’m sticking with it for now, but am continually suspicious of its return on investment.
The tool offers this disclaimer:
These are only recommendations. Recommendations are based on the NRC and other research, not actual requirements. Actual requirements can vary with feed interactions, environmental factors, differences among breeds, management goals, animal health, and other factors.These calculated values are expressed as a percentage of a single “text book” animal recommended value. Consult the “Column Headings” section of this program or the 1985 or 2006 NRC, nutrient requirements of sheep to better understand the range of values, particularly with minerals, that may be appropriate.
So, we know these calculations aren’t the end-all. We still need to continually monitor the ewes’ actual physical condition, because they may not be textbook ewes. In fact, I have a hunch Katahdins are generally more efficient than textbook ewes, because they have been bred with that priority in mind. But I am trying to bump up my feeding from last year, to see if I can shift the bell curve of lamb birth weights higher. It’s so cold and wet here, I want good-sized, vigorous lambs that are less likely to chill; and I haven’t had a problem yet with too-big lambs. So we’ll see if this slightly more generous feeding schedule does the trick!
January 26, 2012 at 3:59 pm
When you say how many Pounds per head per day they are eating are you just dividing how many pounds of hay you are feeding by how many ewes you have and assuming they Are all eating equal amounts? Or do you have a more exact way of figuring it out? We bought a flock all due at different times- had 6 ewes go a month ago then 6 more this week some looking big but not close and some looking a few weeks out. It’s nuts! Want to make sure everyone is getting what they need. This post was exactly what I needed!
January 27, 2012 at 3:04 am
Julie, I do just divide # lbs eaten by # of sheep, and I count the llama as 2 sheep. For the online calculator, I take 10% off as waste when I’m calculating how much I think they are getting (and that’s a high waste figure, but I feed on the ground, so I think it’s accurate for me). The calculator is also doing some math to account for moisture content in the feed- i.e. if the hay’s lab analysis says there is 92% dry matter, than the feed calculator will “write off” 8% of the weight eaten as water.
I have 40 sheep here, so unfortunately, there isn’t a good way for me to figure out what each one is eating. I do have weights on all of them from various times, so I can add up how much the whole herd weighs collectively, and then calculate a percentage of bodyweight they should be consuming as a group to get rough figures (I think they say dry ewes should eat about 2.8% of their bodyweight, then it goes up from there when they are pregnant). But it mostly comes down to averaging, and some will lose out. It doesn’t matter so much with hay, as there is plenty and they all have a chance to eat as much as they want. But with grain, it is harder- when it’s put down, it’s a gobble-fest; so if there is a timid one in the bunch, she’s not going to get her fair share and someone else will get extra.
In the dairy industry, I’ve seen where they give each cow her own headstall feeding station, and she wears an RFID chip around her neck which will only unlock “her” feedstall. This allows them to both control what each cow gets to eat, as well as weigh how much she chooses to take in. In dairies where all of this is electronically monitored and automated, the computer can immediately “flag” a cow who is off her feed, which would be awesome to know! And, it allows them to do interesting math on feed conversion- figuring out which cow can produce the most milk on the least amount of feed, or highest butterfat, etc. Cool!
But so far, sheep don’t make enough money or live long enough to justify putting in such hi-tech systems!
Re- getting sheep with unknown and spread-out due dates, I know what you mean. I did that my first year and hated it. I over-fed some ewes that looked huge and “due any day now” only to realize after the fact that they had a long ways to go and I was giving them too much. This is high risk, as it pushes them towards prolapse if they get too fat, and it encourages huge babies and difficult births. So now I’m all about controlled breeding times and carefully monitoring their intake for each stage of pregnancy.