Animal Unit Months

[BIZIN]

I know I am on the wrong board, but I never get any replies on the forage board. Wondering exactly how to do the math on AUM's? I think I am doing it wrong here. I am using a cow/calf pair as 1 unit, replacement heifers as 0.8 units, bulls as 1.3 units. So if I am running 70 heifers on a paddock for 7 days. I take the 70 multiply by 7 and I get 490. Now here is where I think I am doing it wrong. Do I multiply the 490 by 0.8 as that is the animal unit for the heifers or do I multiply it by 1.2? And on the bulls do I multiply by 0.7 or by 1.3?

 

[novatech]

I know I am on the wrong board, but I never get any replies on the forage board. Wondering exactly how to do the math on AUM's? I think I am doing it wrong here. I am using a cow/calf pair as 1 unit, replacement heifers as 0.8 units, bulls as 1.3 units. So if I am running 70 heifers on a paddock for 7 days. I take the 70 multiply by 7 and I get 490. Now here is where I think I am doing it wrong. Do I multiply the 490 by 0.8 as that is the animal unit for the heifers or do I multiply it by 1.2? And on the bulls do I multiply by 0.7 or by 1.3?

The heifers will consume 80% of what the cow calf pair will eat so you multiply by .8. The bulls will eat 130% of what the cow calf will eat so multiply by 1.3.

 

[dun]

Most everyone calculates it differntly but this is the "standard"
Animal Unit - An animal unit (AU) is one mature cow of approximately 1000 pounds and a calf up to weaning, usually 6 months of age, or their equivalent.
So a 1500 lb cow with am unweaned calf would be roughly 1.5 AUs

 

[BIZIN]

Thanks Novatech. So I was doing it right the first time.

 

[novaman]

I think you made another error, not sure. We are talking animal unit months so your 7 days would have to be converted to months right? 7 divided by 30 = 0.23 months. So your 70 heifers X 0.8 = 56 AU. 56 AU X 0.23 months = 12.88 AUM? Maybe I'm way off.

 

[BIZIN]

haha now im confused

 

[rocket2222]

I think you made another error, not sure. We are talking animal unit months so your 7 days would have to be converted to months right? 7 divided by 30 = 0.23 months. So your 70 heifers X 0.8 = 56 AU. 56 AU X 0.23 months = 12.88 AUM? Maybe I'm way off.

The 12.88 is a AUWeek, times by 4 for the month.

 

[BIZIN]

Now what if I wanted to just figure out head days. Then I would just take 70 x 7 = 490 x 0.8?

 

[rocket2222]

Now what if I wanted to just figure out head days. Then I would just take 70 x 7 = 490 x 0.8?

I'm assuming the 7 is 7 days, so for one day, divide by 7, or just substitute 7 for how ever many day you want.

70 x 7 = 490 x 0.8 = 392 + 7 = 56 or 70 x 1 day = 70 x 0.8 = 56

 

[BIZIN]

So that would be 56 head days. So I could run 70 heifers or 56 cows if I am considering cows as 1 unit, right?

 

[rocket2222]

So that would be 56 head days. So I could run 70 heifers or 56 cows if I am considering cows as 1 unit, right?

yep

 

[SRBeef]

Why not use "cow days" as your unit of measure for grazing.

I take a lactating cow (not incl the calf) as 1.0 cows, a nursing calf starts out at zero when born but by weaning is up to 0.3 or 0.4 cow equivalent.

My bull is about a 0.8 cow eqiuv., yearlings range form about 0.6 to 0.8 cow equiv. depending on weight.

So running your 70 heifers for 7 days means they have consumed 70 heifers x 0.8 cow equiv/heifer x 7 days = 393 cow-days of grazing.

I think this is a fairly simple way of keeping track of grazing requirements and pasture productivity.

By estimating the area they used over the past 7 days and how they cleaned it up, you now know about how much to give them for the next 7 days. I try to give mine no more than 7 days worth at a time. jmho. Jim

 

[novaman]

Why not use "cow days" as your unit of measure for grazing.

I take a lactating cow (not incl the calf) as 1.0 cows, a nursing calf starts out at zero when born but by weaning is up to 0.3 or 0.4 cow equivalent.

My bull is about a 0.8 cow eqiuv., yearlings range form about 0.6 to 0.8 cow equiv. depending on weight.

So running your 70 heifers for 7 days means they have consumed 70 heifers x 0.8 cow equiv/heifer x 7 days = 393 cow-days of grazing.

I think this is a fairly simple way of keeping track of grazing requirements and pasture productivity.

By estimating the area they used over the past 7 days and how they cleaned it up, you now know about how much to give them for the next 7 days. I try to give mine no more than 7 days worth at a time. jmho. Jim

I may be wrong as to why Bizin is calculating AUM's but in my area that is what all the grazing recommendations are figured in. The extension service has all the expected stocking rates for any of the various soils and/or vegetation types.

 

[TexasBred]

haha now im confused

hahaha...me too now....heck just watch the grass. ;-)

 

[BIZIN]

Thanks SR Beef... Thats what I was really looking for. Dad said AUM's and got me confused so I came on here and got more confused. I'm beginning to think that working with dad as he gets older is going to be a bad idea!!! Yes Cow days is what I was looking for. Got it all figured out now. Thanks guys.

 

[SRBeef]

Why not use "cow days" as your unit of measure for grazing.

I take a lactating cow (not incl the calf) as 1.0 cows, a nursing calf starts out at zero when born but by weaning is up to 0.3 or 0.4 cow equivalent.

My bull is about a 0.8 cow eqiuv., yearlings range form about 0.6 to 0.8 cow equiv. depending on weight.

So running your 70 heifers for 7 days means they have consumed 70 heifers x 0.8 cow equiv/heifer x 7 days = 393 cow-days of grazing.

I think this is a fairly simple way of keeping track of grazing requirements and pasture productivity.

By estimating the area they used over the past 7 days and how they cleaned it up, you now know about how much to give them for the next 7 days. I try to give mine no more than 7 days worth at a time. jmho. Jim

I may be wrong as to why Bizin is calculating AUM's but in my area that is what all the grazing recommendations are figured in. The extension service has all the expected stocking rates for any of the various soils and/or vegetation types.

The Extension people can have all the chart numbers for various vegetation types but it isd not as accurate for my place and herd as my own numbers. I think they use AUM to try to be generic across several types of livestock, etc. Cow days is much simpler for me since I am dealing with cattle, not sheep etc.

I have most of my paddocks with parallel hot wires maybe 200 ft apart. If they are 200 ft apart then putting a cross wire 218 ft or 92 paces from the entrance encloses about 1 acre of grass (200 ft x 218 ft = 43600 sq ft = about 1 acre). Definition of an acre is 43560 sq ft but close enough.

Knowing the Cow Equivalents I put on this acre and seeing how long it takes them to eat 8-10" tall grass down to a uniform height of about 3-4" (about the minimum height you want grass to be down to so it can regrow) gives me a very accurate estimate of how many cow days grass I have. This way I know exactly how much area to give them to hold them for 4-7 days 7 days is about my max because any longer than that and the first grass eaten gets a second bite before it can regrow fully....

I hope this helps a bit more and we don't need to be comparing ourselves to extension charts. fwiw. Jim