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Energy

Energy. Probably in sheep production systems, energy is going to be the most limiting nutrient. It is one of the first things that you come up is going to be the limiting and the most likely to be found and it's either due to inadequate feed or feeds of low quality trying to be fed for a various stage of production. If you don’t have this situation, then you probably have excess level and what happens with excess energy is you just have a bunch of sheep getting overly fat. But, generally, we see and under most feeding situations with the normal feedstuffs that we have is either not enough feed or feeds for that stage of production are of low quality.

If we look then at what happens following the same thing with energy as what happens with the pounds of intake, what happens with TDN requirements over the various stages of production.

Energy Requirements for a 176 lb Ewe

Of course, ewes with maintenance, flushing, early gestation, no difference, during these periods. We do have an increase in the energy requirement for flushing and we’ll talk about that in just a little bit. Then, early lactation it is just slightly above maintenance. Late gestation, those carrying twins, it's up close to 3 lbs of TDN. Lactation upwards to 4.5 for a 176 lb ewe. Then late lactation, this is decreased, but it's still always greater with those ewes that are raising two lambs or more.

Let’s talk about flushing. What is flushing? It’s a process of increasing energy, as I said, two weeks prior to breeding and then two to three weeks into the breeding season. And what we are trying to do and it does result in an increased ovulation rate which hopefully then will give you an increased lambing rate. And of all the studies that have been done, it’s going to range anywhere from 10-20% increase in lambing rate by flushing. It does have benefits from that standpoint. Ewes in lower condition going into breeding are going to give you a greater response to flushing, a greater magnitude, but ewes that are still in good condition are always going to have higher ovulation rates than thin ewes. In some old publications, as it relates to sheep, one of the recommendations listed was that you take your sheep down in condition prior to breeding so that you can get the full benefits of flushing. Well, when they’ve looked at ovulation rates, sheep in good body condition score are still going to ovulate at a higher rate than those in low body condition score. It’s just that you are going to get a greater magnitude from a low body condition score ewe when you go to flush. But of all the work that’s been done, you get about a 10-20% increase in ovulation rate. What does this involve? Well, increasing the energy, in this case metabolizable energy concentration in the diet from about 2 megacals per kg to 2.1 or a total of 1.4 megacalories of metabolizable energy per day. It isn’t a whole lot, but it does give you some pretty good results and in many cases with a 10-20% increase in ovulation rate, it's going to be worth the effort. Now, what do we do? What do we use to flush? Better quality pasture is sufficient. You move them from poor quality pasture to better quality, you’ll get a flushing response. Supplementing some grain will give you the response. Those are two ways that you could go about, methods, management procedures that you could do to flush your ewe flock.

Okay. Now let’s talk about the late gestation period and here we are referring to the last six weeks that are most critical. And why is this? Well, about 70% of the fetal growth occurs during this time. Ewes with multiples, then we’re talking anywhere from 20-35 lbs of fetal growth during this time period. Which is, when you consider the size of the beast you’re working with, is quite phenomenal. Now just because they’re having twins, doesn’t mean they need twice as much. Ewes with the single lambs need 37% more energy in the form of metabolizable energy per day and those with twins 57% more. It isn’t a doubling. What happens if we don’t provide adequate energy during this time period? We get a situation in sheep, you can get it in other species too, but in sheep it's ketosis, probably more commonly referred to as pregnancy toxemia or twin lamb disease. You can kind of figure out why they come up with twin lamb disease because it usually occurred in those ewes that were carrying multiple fetuses that come down with this ketosis situation during late pregnancy. And, of course, what happens, they don’t get enough energy supplied in the diet and they start taking body fat to provide for the growth of the fetuses and you get build up of these ketone bodies from breakdown of fat for the energy to supply for the fetuses. Ketosis is a problem. Best thing to prevent is to adjust your feeding program. You can treat it. There are a lot of methods around to try and treat, but success rates, in most cases, aren’t all that great. One thing that probably is less known or less observed is the fact that if we don’t feed properly during late gestation, we’re probably going to see such things as milk production is going to be affected, less milk production, lamb birth weights, lambs are going to be lighter and weaker at birth, you are going to have a higher death loss from shortly after lambing, early on in that life of the lamb because of poor nutrition during this time period. And these are probably things that most producers don’t realize. If they see ketosis, then they say yeah we’ve have a problem, but thin ewes, down in condition are not going to produce as much milk and they are going to have lighter lambs and lighter lambs at birth are going to be compromised from the standpoint of survivability. Now we can carry it too far, feed too well and get too heavy of birth weights and have losses also, but, in most cases, this is the greatest effect of inadequate nutrition is the death losses from light birth weights and poor milk production.

This is just to kind of show net energy for pregnancy, the differences that occur with the various fetuses from one to three because we have a lot of ewes now that are producing 3 lambs.

If we look at number of fetuses over here, one, two or three. Day of gestation, day 100, 120, 140. This is the net energy for pregnancy for one, a 78 percentage point increase for two lambs, over doubling for three. Point is, two is not twice as much as one, three is not three times as much. But you can see the magnitude and the increase in requirement when you get out here at day 140, even for one. But 570 kilocalories per day is the requirement for a ewe just to maintain a pregnancy along with other bodily functions. Great increases in these high producing ewes when you get out here into day 140 and on into that last trimester of the gestation period.

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