The value of grazing weeds

Cam Nicholson discusses weeds in pastures – are they valuable feed?

Cam Nicholson:... this topic, which has fascinated me for a while, because as an agronomist, and as someone providing advice to a whole lot of farmers, there's this constant concern about weeds I have in my pasture, and what can I do about weeds in my pasture. In a lot of cases, the weeds are a valuable source of feed, and actually removing them has limited value apart from you wanting to spend some money in making your pastures look a bit prettier.

Cam Nicholson:So what I want to do, and where this work originally emanated from was just understanding more about that weed dynamic and how weeds in a pasture system, or what we call weeds in a pasture system, just appreciating where they are of value, and how they can be used rather than necessarily having to remove them.

Cam Nicholson:This is work that's in progress at the moment. It's being supported by Meat and Livestock Australia, and someone who is helping me, the second name on there, Jess Brogden, Jess is here, so Jess is going to put up her hand now. So a lot of the data that you'll see in the photos that I'll put forward here are one's that Jess has actually prepared for us, and also Lisa Miller that some people may know as well.

Cam Nicholson:It's being done through Southern Farming Systems, so the information I'm going to give you here, we don't have it in hard copy yet, but in another six months time it will be.

Cam Nicholson:Okay, just to run through, and a lot of the information I'll give you, there are four bits of information I suppose that I'll be talking about. And so there are some terms that we need to understand.

Cam Nicholson:The first one is around digestibility, and I'm sure people have heard the term digestibility, but basically what it means is a proportion of the fodder which is retained by the grazing animal. So something that's of higher digestibility, more of what they eat or put down their throat, they can actually use within their system and it's not excreted. So basically high digestibility means you get greater value out of it.

Cam Nicholson:The second one which is interchangeable is a thing called metabolisable energy, and a lot of cases, the limitations in our animal's system is based on not having enough energy in the system. So energy is actually driving the performance of those animals. There's a direct relationship between metabolisable energy and digestibility. A rough rule of thumb is if something is 70% digestible, it's roughly 10 megajoules of metabolisable energy. That goes up and down by about .8 of a megajoule of energy for every 5%, so if something was about 75% digestible, a rough rule of thumb would be about 10.8 megajoules of energy. So it goes up and down on that basis.

Cam Nicholson:And so really important when we want to understand where the weeds fit into it and the value that those weeds might have is understanding what energy or what the digestibility of that feed is and where that sits in comparison to the pasture that you're growing all the desirable species that you've got in your pasture.

Cam Nicholson:Third term is around crude protein, and again, I'm sure people are familiar with the term protein. It's called crude protein because it not only includes the proteins that the animals can directly digest, but also includes things like nitrogen and urea and things like that that are picked up in the protein as well, and that's why it's called crude protein. So I'll be showing you some result around the protein in these weeds as well.

Cam Nicholson:And the last one relates to fibre. Some people probably heard the term NDF or neutral detergent fibre. It's basically the cell walls or the structure of the plant that the animals digest. And so the more the fibre increases, the slower it is for it to be processed and pop out the rumen, so that they can eat some more.

Cam Nicholson:So things that have got higher fibre or fibre limits or regulates intake, how much an animal can eat. Once they eat it the first time and their gut is full, they can't eat anymore again until that gut empties out or their rumen starts to empty out. So the amount fibre that's in it is really important as a determinant of how quickly that goes through the rumen and therefore how much more they can eat. So there are four terms that I'll be talking about when I go through the different weeds that we've got.

Cam Nicholson:Okay, some of the measured levels around those terms, typically digestibility is in the range of about 85% at the top end of the scale to around about 30-35%. It's not north to 100. Okay, that's the sort of range that we'll be talking about. From feed tests, they have a simple three step category. They talk about high quality feeds being above 65% digestible, and low quality feeds less than 55% digestible.

Cam Nicholson:So when I talk about these weeds and where do they fit in from a digestibility point of view, I'll refer to them sometimes as just high quality feed or low quality feed.

Cam Nicholson:From a crude protein point of view, most people will be familiar with these, dry sheep needs about 6% or 8% protein. An animal that's lactating and therefore putting some protein into milk needs about 8% or 10%. And a growing animal, because it's putting down muscle and things like that, it needs about 12% to 16% protein depending on how fast it's growing.

Cam Nicholson:If an animal eats excess protein, as you probably know, it's got to get rid of that excess protein because ultimately it will poison itself if it doesn't get rid of that nitrogen, it uses energy to do that. So super high levels of protein can actually have a detrimental effect on overall performance because they're actually using some of that to remove excess nitrogen out of their system, and they use energy to do that. So there's sort of just some numbers to keep in mind. The 65%-55% range and those for your protein.

Cam Nicholson:And the last one's around the fibre. There aren't any standards on what fibre should be, but a rough rule of thumb that the dairy industry uses is around about 35% NDF. They need at least that much fibre in their gut, because that makes the rumen function properly. So they need around that 35%. When it gets lower than that, the gut doesn't perform as efficiently as it possibly could. And so that's another number just to keep in mind, around about that 35% figure.

Cam Nicholson:Okay, a few people may have seen this as well. Anybody done Prograze as a course many, many years ago, you've probably seen this graph then. Just to explain, because this sets up when I talk about the different weeds, this is April to March. So they typical sort of annual season that we would have in this part of the world in Victoria. This is digestibility up here, and on the other side here is metabolisable energy. And you can see that rough relationship between 70% digestible and about 10 megajoules of energy.

Cam Nicholson:If we follow that line around the top, around April-May, when things are actively growing, sort of the period that we're in now where things are growing leaf and not much stem, we're sitting around this 80% plus digestibility in our pastures. When we get to about September-October, and we get to this early in need of flowering where things start to run up the head, you get that decline in quality, and that declines and continues to decline until we get these dry stalks around about March before the Autumn break.

Cam Nicholson:So any dry material you've got left is sitting around that 45%-35% digestibility over that period, and that's typically the sort of cycle that we get with our pasture systems as far as quality goes.

Cam Nicholson:The top line represents more of what I call high quality species. In that mix, the bottom line as it says there has got more volunteer species in it that are of poorer quality. So somewhere in between those two lines, which is the black bit there, is representing the sort of quality that we could expect during the year.

Cam Nicholson:So if we look at high quality pastures from that definition from feed test, we've got high quality pastures. In a lot of cases, if we've got good species in there, until we get to that sort of November-December period, if we've got some of the poorer quality species there, it's probably tapering off around about October. And we hit what we call low quality in around about this January-February-March if we've got reasonable species.

Cam Nicholson:So if you've got ryegrass that's gone dry or phalaris or things like that, that would be sitting up at this end. If you've got more things like silver grass, those sort of things would be more down that end. That's just a bit of a split up between that.

Cam Nicholson:So how does this all fit from a weed point of view? First of all, I want to concentrate on the weeds that we might have when our pastures are typically in this low quality phase. So that's the first one I want to talk about.

Cam Nicholson:So what we might call our summer weeds that you get. Now most of the summer weeds that you'll get in the pasture are germinating now. So the ones that you see in December, January, February, March, are actually germinating now. So they virtually have a 12 month life-cycle.

Cam Nicholson:Anybody know what that is? Yup?

Audience:[inaudible 00:09:10].

Cam Nicholson:No. Anybody else want to have a crack?

Audience:Mustard.

Cam Nicholson:Sorry.

Audience:Mustard.

Cam Nicholson:Mustard, no.

Audience:Dandelion.

Cam Nicholson:Dandelion, yeah. Some folks call it dandelion, flatweed, catsear, it's got a few different names. Okay, so that's the first one. A bit more of a quiz. Anybody can pick what that one is? It's a bit later in the season.

Audience:Sorrel.

Cam Nicholson:Sorrel, okay. Most people got that one. That one?

Audience:Wire weed.

Cam Nicholson:Wire weed or hogweed. They're different, but most people call them the same sort of thing. So some of that wire weed. Something like that?

Audience:[inaudible 00:09:43].

Cam Nicholson:Sorry, not [inaudible 00:09:44]. This is middle of the summer. [crosstalk 00:09:46] Yeah, so it's a [inaudible 00:09:50] of some sort. It's actually wild radish, this one, but you can get those mustards and things like that grow. They're all of a similar family. So that one in that case is wild radish. And that last one?

Audience:Milk thistle.

Audience:Thistle.

Cam Nicholson:It's milk thistle, sow thistle. Yeah, different names, but that's all right. I'm happy to accept all of the above.

Cam Nicholson:Okay, these are five weeds I just want to follow through. Jess has done, I don't know, 25 of them or something, so there's a huge list of them here. I'm not going to go through all of them, but I'm just going to show you some of them because I think they show the differences in some of these weeds, and so some of the key principals that I want you to take away are key messages to take away from this.

Cam Nicholson:So first of all, the summer weeds. We also have a few that will germinate in spring-summer on opportune rain. Okay? So those weeds I was showing you before, they're all germinating now, and they will grow through the season, and they will pop up and still be around in summertime. We've also got a few that appear on spring-summer rain.

Cam Nicholson:That one, anybody know what that is?

Audience:Mint weed.

Cam Nicholson:Mint weed. Okay, yeah. Clammy goosefoot or goosefoot it's sometimes it called.

Audience:Clammy goosefoot.

Cam Nicholson:Clammy goosefoot, yeah. So it's got a few different names around the traps, but yeah, that's what it is. It's sometimes called mint weed. It depends on which part of the world you come from and which school you went to.

Cam Nicholson:Okay, that one?

Audience:It's nightshade.

Cam Nicholson:No, not nightshade.

Audience:Fat hen.

Cam Nicholson:Fat hen, beautiful. Well done. Okay. So that's fat hen. [inaudible 00:11:21], there's a few of those that you'll get, but they're germinating when we get October rain, November rain, December rain. That's when you'll get them.

Cam Nicholson:That one?

Audience:Windmill?

Cam Nicholson:Windmill grass, beautiful. Okay, so I'm going to show you three. There's another bundle of them there that we could have put up as well, but those three will show you the same sort of things. So these are the few summer weeds that I want to refer to.

Cam Nicholson:First of all, let's take the dandelion, flatweed, and catsear. There are measurements that Jess has taken on the digestibility of that weed. That line there and above that line is what we call high quality feed based on that definition. So that's where dandelion or flatweed fits in.

Cam Nicholson:This measurement here that's got about 70% digestibility, that's what the plant looks like. So a plant like that is 70% digestible. And that is occurring around about that November-December period. Think about how that was declining around November-December. These, in fact, are providing high quality feed than what most of your pasture would be that time of year.

Cam Nicholson:And remarkably you get to March and the plant looks like that. You see it dry off and look like that, and you think it's not worth much. It's still above 65% digestible, so it's still got value in it even though it looks like that.

Cam Nicholson:If I do the protein for this same sort of thing, that's protein at 8%. So if you're running dry animals on it, those dry animals would be getting more than enough protein eating that as a feed source.

Cam Nicholson:In this case here, round about that 12%. Think back to those numbers I was talking about of what does a growing animal need. A lactating animal, around about that 10%-12%. Believe it or not, that would provide enough protein. So one weed that we thought might not have been worth much.

Cam Nicholson:Here's another one. Sow thistle, when it looks like that, people will have seen that when it germinates. That prickly sort of thing. That's sitting up above 70% digestible. It's about 10 and a half megs of energy sitting in that. When it starts to run the head like and it's just getting a flower on it, it's still sitting around about that. And when it looks like that and you think, "Oh, it's just a weed and a pain, not worth much." It's still sitting there at about 60 odd percent. So again, another high quality feed.

Audience:You know you've got to watch your sheep to see what they select, and milk thistle is the first thing they like.

Cam Nicholson:Absolutely, yup. And if you go even further and you start looking at some of the proteins in that, the proteins in that early phase are around about 25%. So what you're saying is dead right. They go around, they seem them, they know what they want to pick out. And a few of these photos that I've taken was a leased paddock that we got this year, and when you put the stock in it, you just watch what they went for and you're dead right. First thing is all of the milk thistles. Straight away, they're all standing around it. About four or five of them are all standing around one plant, just eating it into the ground.

Audience:The milk thistle juice is corrosive for some species, isn't it?

Cam Nicholson:Yeah.

Audience:It can cause diarrhoea?

Cam Nicholson:Yes, it can if they eat too much of it over too long a period. And I should say, and I won't have time to go into it here, the stuff that we're putting together, we'll have issues around the animal health and the animal health implications on some of these weeds, and as well as at some of the potential herbicide options that you could look at if you did want to remove them. So I'll put them aside because I'm just not going to have time in the 30 or 40 minutes I've got to do that.

Cam Nicholson:So yes, there are some that do have some certain animal health issues that we do need to be aware of, but we'll go through each of those, so they'll be information on each of those. There will also be information on seed set of each of those weeds, and how long that seed lasts for. Some seeds will only remain viable for a couple of years, other seeds will remain viable for decades. So we'll have that information in there as well.

Cam Nicholson:So we take the sow thistle, it's the same sort of thing. A great protein when you think about where that is. So running dry sheep on that, cool. If they can eat enough of that, you've got your protein covered.

Cam Nicholson:Clammy goosefoot, anyone want to have a guess what clammy goosefoot is like? Good, bad, otherwise? That's why it sits around about 65%-70%. Even when it looks like that, the leaves have gone brown, that's where it tests from a digestibility point of view. If we fly through and look at the protein of it, that's where it sits.

Audience:Some of these summer weeds have distinct odours associated with them.

Cam Nicholson:Yup.

Audience:And it stinks like hell, the mint weed. My experience is you may get stuck with it.

Cam Nicholson:It'll be one of the later ones they will eat, but in the measurements we were doing here, it disappeared as well. It was just one of the last preference ones.

Audience:[inaudible 00:16:44].

Cam Nicholson:Yeah, my general experience on it is it's not their preference to eat it, but they will eat it if there isn't other things that they've got.

Cam Nicholson:All righty, so what's the value of those grazing weeds in a pasture system? So I just did a little bit of work where if we think about the time of year we're talking about is where in natural pastures that we might have or dry pastures that we've got, are probably sitting around, and I'll just take at a middle point of 45% digestible and about 6% protein. That's typically what your phalaris or your ryegrass pastures when they've dried off in Feb, the bit of dry material that is left, that's about what it tests out at after it's gone through the season.

Cam Nicholson:And then I've said, "What would happen if I put some sheep on it?" So I've just done this bit of calculation. First cross ewe, she's dry, she's empty. So just before joining, but I've said she's 55 kilos. The green height of five centimetres in that weed that's growing in that pasture, so it's flat to the ground like you'd think a normal pasture would be. They're growing upright as a lot of these weeds do.

Cam Nicholson:The dried materials are 45% digestible. The green material, the weed, would be 60% digestible in it. And so I just did some runs on this. Now just to explain what is going on here, this line across here represents the amount of dry material that would be in the pasture. Ignore all these lines at the top for the moment. If you put the first cross ewes in there and there was a tonne of dry feed, at that 45% digestible, those ewes would lose about 175 grammes a day.

Cam Nicholson:Okay, so just imagine they're just eating that dry feed and nothing else. As there's more dry feed available and therefore they can harvest more, the weight loss becomes less, but they still have a weight loss. So even if there's five tonne of dry feed sitting in the paddock, they are still losing 50 grammes a day because the quality of the feed that they're putting down their throat isn't good enough, and because the digestibility is low in it. What they eat, they can't push out through the rumen and eat anymore, so they're limited to how much energy they can extract out of the feed they put in there.

Cam Nicholson:If you include in this situation here a bit of green weed, and let's take the grey and the yellow lines there, where we added some green feed into it as well. So if we take the yellow line there, that's if we had 200 kilos of green feed. Imagine if you got 200 kilos of weed in there plus this dry feed as well. Their performance goes from losing about 175 grammes to sitting up here of nearly breaking even.

Cam Nicholson:So that little bit of green of that higher quality put into the system changes the whole dynamic of the change in weight gain and also the amount of feed that they're going to eat. So that bit of green helps drive the consumption of the dry as well, and it doesn't matter if it's 200, 300, 400, or 500 kilos, you'll get that same sort of effect. Okay, so it's a little bit of green in it with that level of protein and that level of energy that's making the change.

Audience:Is that change happening because of the green in the rumen to enable the dry to be more efficient?

Cam Nicholson:Yes. It's a combination of things. The little bit that they eat is obviously of higher quality, so they can extract more out of that package of the green stuff they ate, but it also changes the function of the rumen because you've got that higher protein in there, and so the whole rumen function works better as well.

Cam Nicholson:And we found exactly the same thing when we've done a whole lot of stuff on grazing stubbles. If we have a little bit of green picking stubbles, the performance is very, very different to if they have just gotten dry stubble without any green pick in it.

Audience:So where there's no green, it's possible to supplement just a few to keep the rumen, right?

Cam Nicholson:Yeah, so adding that protein and adding that little bit of extra energy into it, changes what they are eating from a dry point of view, all the performance on a dry point of view.

Cam Nicholson:So the idea of this graph was really just a simple way of saying, if we've got that bit of green weed in it, is it worth anything to us? Yes, it's worth quite a bit to us as far as animal performance goes.

Cam Nicholson:Now obviously if they go into a paddock and there's a couple hundred kilos of green feed and within three or four days of eating all that green feed, then you're going to start to drop down to here again. But while that green is in there, there is some value in it.

Cam Nicholson:Any other questions?

Audience:Say they ate the green in four days, is there a two day lag?

Cam Nicholson:Yeah, there's a transition of as the bugs change over, yes. So this calculation I did, I just said that the dead material was like that, and the rumen was functioning okay.

Audience:If they ate it all in four days, does that protein stay in the gut?

Cam Nicholson:The protein moves through pretty quickly, so it doesn't stay weeks in there after they've eaten it. No. So this performance is almost on a day by day basis. How much green have I got there I what might I be getting out of it.

Cam Nicholson:The message I wanted you to take home though is that little bit of green pick that we might think are weeds and not worth much, are they good quality from both a protein and an energy point of view, but also it changes the dynamic of what they actually do with dry feed as well.

Audience:I suppose 100 kilos or 200 kilos of green, that could be weeds or I guess that [inaudible 00:22:50].

Cam Nicholson:Absolutely, yeah.

Audience:[inaudible 00:22:56].

Cam Nicholson:No, that's right. A couple hundred kilos of green isn't all that much.

Audience:Yeah.

Cam Nicholson:The difference that I've got in here is that I've said that that green is actually of reasonable height so they can actually harvest it and graze it. If you were thinking of a pasture, 200 kilos a pasture would be about half a centimetre to a centimetre high. Animals trying to bite that don't get much. But when the plants are sitting upright, as a number of those weeds are, they're much easier for the animal to harvest.

Audience:Would it be similar if the loose end is standing up?

Cam Nicholson:If the loose end is standing up, yes. If those shoots are standing up, yes it is.

Cam Nicholson:Okay, let's move on. I have no idea what I've got time wise. Joe, are we going all right? Okay. All right.

Cam Nicholson:Just a little bit of green stuff in stubbles. We did quite a lot of work in the grain and graze programme on the value of stubbles which I sort of alluded to. I had a lot of surveying of stubbles. Variability, easily about five tonne of dry feed left behind. The quality of that feed, and this shows again, the green that was in that dry feed is around about 70% digestible and about 98% protein, which is any grain on the ground is even higher as far as energy goes in it.

Cam Nicholson:And then you've got your straw and your trash, which is really down at that low end. So this is an average of probably about 40 stubble paddocks that was surveyed over time.

Cam Nicholson:What we learned from doing that, the livestock performance, and we did a lot of trials on weighing stock in and out of stubbles, but it fits this weed thing, is around the livestock performance is linked to the amount of grain and green on our farm.

Cam Nicholson:And this is a example where we're weighing on a weekly basis. So up here is the amount of green and grain that we've got in the system. On here is the live weight gain of the animals, and as you can see when they go in there, they gain weight. That might be a little bit due to gut fill, but you can see that they essentially gain weight up until a point where the green and grain drops off to a certain level.

Cam Nicholson:So we've got a lot of green and grain. The live weight goes up fairly quickly as the keep eating into that. They get to a certain point there and all of a sudden there's a tip over. And so those animals don't just keep gaining weight and slow down and slowly taper off. They're either gaining weight or they're losing weight, and that tip over is really, really quickly.

Cam Nicholson:And exactly the same thing would happen when stock are grazed in weeds. When that bit of green is in there, you'll be getting that performance as soon as that green goes, that performance will change quite dramatically.

Cam Nicholson:And out of all that, we learned that there was a certain point or a certain threshold down here where if we had less than 40 kilos of grain or round about 40 kilos of grain on the ground, if we were below those thresholds, then animals would lose weight. If it was above those thresholds, it didn't matter whether it was a lot of green and not much grain on the ground or a lot of grain on the ground and not much green, animals would increase their live weight gain.

Cam Nicholson:And so it's a really useful way of being able to walk into a stubble and know whether that stubble has got any grazing value in it or not. I can tell you, once it drops below those thresholds, you're happy to have the animals lose weight because that's what they'll do, or you may start supplementary feeding if you want to keep them at that condition. Okay? But the gain is really quick. We were surprised. And all of these dots represent long-term trials that we've done, so this has been done for many years over, many stubbles where we've measured a whole lot of green and grain in them.

Cam Nicholson:And it's pretty consistent as you can see. The red things are down here. A couple of these here is where we've had some major diet changes, and that's basically been that it's rained in the period those animals are in there, and we've gone from having a whole lot of grain to all of a sudden a whole lot of green pick really, really quickly. That first change has made a difference.

Audience:In all the stubble, I assume these are cereals?

Cam Nicholson:Yeah, these are cereals. No, I haven't done anything on canola, sorry. But having said that, I can't believe if you ever tested cows who have been on canola stubble, the amount of canola seed that actually goes through them is quite remarkable. So I suspect they can pick that up fairly well as well, both sheep and cattle. Yeah, lick it up.

Cam Nicholson:All right, and so the rough rule that we use is that if you've got 40 kilos of grain as I've said, 40 kilos of green shoot, then that's enough to tip over and be in a positive position rather than a negative on. If you want to translate that, that's about 13 grains per .1 of a metre square. Now .1 of a metre square is about your boots, if you look are your books here, are about 30 centimetres by 30 centimetres. Put them at 90 degrees, draw a little square like that, step back, count the number of grains in it or count the number of green shoots in it, and that gives you some idea of what that threshold is.

Cam Nicholson:For the pulses, the equivalent of that is about 4 lupins on the ground in that little square. A couple of chick peas or field peas or about one faba bean is about all you need to find in that square there, and that will be enough to keep them above that threshold and those points.

Cam Nicholson:That's what 40 kilos of green looks like. So if we were thinking of our weeds, something that's got about that level of green in it is all you need. That's where that threshold sits.

Cam Nicholson:All right, I just want to finish off with a couple of winter weeds because the winter weeds is a slightly different story. Before we were talking about weeds down here, and now I want us to move and think about weeds that are here competing against pasture when the pasture is off high quality, and how some of these weeds fit in.

Cam Nicholson:So your winter weeds generally germinate autumn-winter, so this time of year. What's that?

Audience:Barley grass.

Cam Nicholson:Barley grass, okay, no need to correct that one. All right, that one? Winter grass or poa. It's a little bit hard to see, so I'll give you the benefit of the doubt on that. And that one, it's a bit easier, silver grass because it's got [inaudible 00:29:05]. That one?

Audience:Capeweed.

Cam Nicholson:Capeweed. If we don't get capeweed were in strife. All right, and that one?

Audience:Marshmallow.

Cam Nicholson:Mallow, yeah. Okay, so we can pick all the winter ones pretty well, and that's good. Common you find in all these typically in pastures that we've got competing for other stuff.

Cam Nicholson:So let's have a look at Barley grass. Where does barley grass sit? Barley grass has a digestibility up until about September-October of about 80%. Okay? I can tell you, some of your phalaris is the stuff that you're test will be below 80%. So while it's in that leafy, vegetative stage, it's actually high quality feed, and as people would probably know, germinates early in the season and gets away fairly quickly. Okay?

Cam Nicholson:If we look at something like silver grass, slightly different story. Okay? So it's silver grass when it first sort of gets going when it's still leafy. It's not too bad. I should say the scale is slightly different here. That's October-November-December. It's of lower quality. So of the weeds we've got growing in winter, your barley grass is higher quality and stays higher quality for longer than what something like silver grass does. Silver grass will decline quicker from that point of view. Okay? And it fits into what you might call the low quality category by the time you get to around about November. That's where it's dropped to.

Cam Nicholson:Okay, capeweed. Anybody want to have a stab at where capeweed you reckon might fit? So it sits in the high quality feed from a test point of view or from a digestibility point of view. And marshmallow fits up there. Most animals go into a paddock and they find a bit if mallow and they eat all the leaves of it and leaves the stems behind. Okay, that's because when you start to look at some of the quality, that one might be a bit of an adoration, but all of these are sitting around that 75%-80%.

Cam Nicholson:So it's not as though they're not picking out the weeds because they're lower quality than the other stuff that's growing there, in some cases it's probably higher quality in the desirable species that you own. And that's why they'll pick them out and eat them. So if you think about it, it adds to the feed source.

Audience:Can I ask a question?

Cam Nicholson:Yeah.

Audience:[inaudible 00:31:24].

Cam Nicholson:No, no, no. That's because we didn't have measurements. This was a bit of a transition. It just came on in July, so we've had a transition of people between then, so we're filling in a few of the gaps. Sorry. So I'm just showing you this as [inaudible 00:31:42] at the moment, but I would imagine that those two bars will sit somewhere in there anyway.

Cam Nicholson:So that's from the energy point of view. I've just summarised these now from a protein point of view. As you'll see, something like barley grass stays really high protein until about October. Okay, so it's a high quality feed. Contrast that in something like capeweed. Capeweed is up around 30% digestible, I'm sorry, 30% protein in those periods. And I reckon most of you would have that capeweed is a weed. It's a bit of bug and we don't like it. From an energy and from a protein point of view, it's actually got a fair bit in it. It's got some downsides which I'll talk about in a second.

Cam Nicholson:Something like marshmallow, look at the proteins in that. December, it's 20% protein. Okay, and these have been tested multiple times and these are the results we come out with.

Audience:For the marshmallow, is that including the stem?

Cam Nicholson:It includes some stem. Yeah, some stem in that as well. I suspect though that where you see marshmallow, quite often it's in fertile areas. They might be around sheep camps and things like that. And I imagine that protein is a bit high because it's actually high in nitrogen and it's sort of picked that up and turned that into the protein on it. And if you then look at silver grass, as you can see, the protein is a bit lower as well.

Cam Nicholson:A couple of other things I just want touch on to finish off, one is around fibre. So remember that figure that I had for fibre which was around about 35%? We want to try and be above 35% for active and good rumen function.

Cam Nicholson:If you look at something like capeweed, and we're hitting around about that 35% percent, you can see in a lot of cases that the capeweed doesn't make that grade or is just on the border line, and I think that's part of the reason why when you see animals that are grazing capeweed, we do sometimes get some animal health issue, putting nitrate aside, but some animal health issues just on the general function of animals grazing lots of capeweed, because the fibre is just on that border line if it's had enough for the rumen.

Audience:But you could supplement?

Cam Nicholson:Yeah, so you can add other things into it, yeah. But just thinking of it as a weed, separate as an individual weed, energy, protein, pretty good. Fibre on that sort of dicey side of it. Okay?

Cam Nicholson:And mallow sometimes can do the same sort of thing. It's on that sort of dodgy sort of area, where typically the things like our barley grasses and silver grasses, you graze barley grass, you generally don't see those digestive upsets in that early stage on barley grass. And the fibre sits about right. Okay, that's why it's high quality, but it's above that threshold of 35.

Cam Nicholson:Last one I'll show is just the water content. And I'm sure everybody is familiar that when you've got green feed in that, it's got a fair bit of water in it. Typically, in the middle of winter it's 80%-85% water. So when we say a kilogramme of green feed, it's actually only 150 grammes of dry matter because it's 85% water. And that's why animals, if they can be fully fed at that time of year, don't need access to water because they get more than enough water that they need simply by what they eat and they've got to get rid of.

Cam Nicholson:The reason why I put the water content up is that, anybody know where water is extracted out of the animal?

Audience:In the large intestine.

Cam Nicholson:Large intestine is one and the third stomach is the second one. So there are two spots where the animal, if you like, can suck out water as it passes through before it's excreted out the other end. And usually, once it gets above about 85% water, those animals have trouble extracting all the water out if it before it passes through.

Cam Nicholson:So, in other words, if something is above 85% water, then it will tend to be runny when it comes out the other end because you can't extract enough water out of it. And I've just put these four up just as a bit of an example of that.

Cam Nicholson:So if we look at something like capeweed, we've seen animals eating capeweed and it all squirts out the other end. Look at that. Yeah, 90+% water in it.

Audience:But to what extent is nitrate an issue there when you've got some bowel irritation?

Cam Nicholson:Okay, so nitrate can be a problem as well. The nitrate levels in some of these that we've tested at different times, not in the work Jess is doing, but in different times, early on in the season quite often can be below what we consider to be irritable sort of threshold levels. Sometimes weather conditions exacerbate that, so things like frost and cold periods and stuff like that. Herbicides on them can concentrate or exacerbate those as well. But there are times where the nitrate in it is still below what is considered to be non-irritable, but it will still squirt out the end.

Cam Nicholson:They just can't extract enough water out of it before it's excreted out the end. It just goes through too quickly. There's too much that they've got to try and suck out and absorb, and that's why they get the runny bums. Okay? Where if you contrast something like your barley grass that they're on, around about that sort of point there, they can still extract that water out of it, and that's why the faeces will be tighter.

Cam Nicholson:So that's just one. So if you look at your capeweed, from that point of view, putting nitrate aside just for the moment, in the early stage you've got high water. That's why it will squirt out. Low in fibre, that's what I might not be the most fantastic diet that they're on, but the energy and protein is pretty good with it. So if it's a component of the diet rather than a major source of the diet, then it can actually be a useful feed. ]

Audience:What's the NDF?

Cam Nicholson:The NDF of?

Audience:Capeweed and that, so like will that take into account how it passes through?

Cam Nicholson:Yup.

Audience:[inaudible 00:37:22] how that either increases or slows it passing through.

Cam Nicholson:So that's the NDF, so that's the fibre. [crosstalk 00:37:44] That's the NDF of it there. So remember I was talking about that 35%, sort of being around about that? If you look at that, that will sort of bounce around on that threshold I reckon between that, and that's why I reckon sometimes, because we're right on the edge, sometimes you could potentially get that problem, and that sort of makes sense to me that that's why sometimes that might be an issue. Too much capeweed in the diet and therefore would have that problem just on that fibre in it and the water content.

Cam Nicholson:All right, five minutes? Summary time, Joe. All right.

Cam Nicholson:I put there that weeds can provide a valuable source of energy and protein, especially when in their vegetative stage. And I've got animal health issues aside. There's a whole story around these different weeds and the animal health problems that you can get. Nitrate is one that we've spoken about, but there are a whole lot of other potential toxins that some of these have and can concentrate at certain times, which we'll go into in the details of the weed stuff that we put together.

Cam Nicholson:And so the choice to remove these weeds is a balance of the feed provided against the negatives. And one of those that we're working on at the moment is this whole idea of competition.

Cam Nicholson:Okay, so all I've talked about in the weeds here is the value of them if you eat them. I think there is another whole story we need to understand that okay, if you've got those weeds here and they're competing against the desirable species you want, just how much impact are they actually having?

Cam Nicholson:Okay, so Jess is doing some work for us at the moment where we're removing some of the competition of those weeds and looking at how that changes the dynamic of the other species that are left behind, because I think that's an important one that we need to understand if we're making those decisions of removing those weeds as well.

Cam Nicholson:And other negatives, things like contamination from seed is obviously issues that you need to consider. So if you've got barley grass and things like that, there are those seed issues. Erodium, which you might have with the seeds. Those sort of things need to be taken into account.

Cam Nicholson:And the last one in the whole weed management is just keeping in the back of your mind this idea about seed longevity or how long those seeds will remain viable once they've been set, because I've seen lots of cases where people have tried to remove certain weeds out of a system, and two years later they're all back again. And they think the weed control failed. The weed control actually worked really well. It's just you've got a seed bank of 10 years of seed sitting there and it's just gonna keep germinating year after year.

Cam Nicholson:So understanding that whole life of the seed that you've got there is really important when we're making those choices of weed removal. And that also will be in the stuff that we're putting together. This work will be available through the MLA Feedbase Adoption Programme, so in the next six months, all of this will be available in multiple sources.

Cam Nicholson:That's where I'll finish talking, but I think there's a couple questions?

Audience:Heliotrope.

Cam Nicholson:Yup.

Audience:I just thought I'd mention that because it causes some issues.

Cam Nicholson:So yes, it's really hard to control, and yes has toxicity issues. So heliotrope is one of those weeds that I'd be removing as a weed. Yeah.

Audience:What value is Onion grass?

Cam Nicholson:So I didn't put onion grass up there, but onion grass, if you can remember of the top of your head, Jeff, but the NDF in it, so the fibre in it was up around 60 odd percent in the middle of once it's germinated. The energy is around about eight or 9 megajoules I think it is, and the protein is pretty low as well. So it's got everything going wrong for it. Yeah. And that's the reason why if they eat it and it gets caught in the guts, it doesn't digest and go out the other end because the fibre is just so high in it. It just rolls around in the gut. Yeah.

Page last updated: 27 Jun 2022