How many acres of grass does a cow eat per year?

Answer 1

There are too many variables at stake here to be able to fully answer this question. It all depends in the size of the cow, what she is or has been fed, her maintenance and thus lactation and reproductive requirements, the quality of the feed or pasture she is fed or eating, what condition she is in (needs to stay at, lose or gain), and moisture content of the feed.

We can, however, provide an average amount that a cow should consume in an entire year, not counting for the variables expressed above. Let's say we have a 1000 lb cow that eats 2% of her bodyweight in dry matter feed per day. That means she is eating around 20 pounds of dry matter per day. So for an entire year (365 days) that calculates out to 7300 pounds, which means she is expected to consume around 3.3 tons of feed a year on a dry-matter basis. On an as-fed basis, that number could change from anywhere around 4 tons to 12 tons or more. This is because a cow will consume more feed if it is higher moisture and better quality, and will eat more if she's thin and needs to compensate for losses sustained over time, and/or is experience some level of cold stress that is causing her to eat more to meet her energy or nutrient needs. Lactating cows also tend to eat more than dry cows, and pregnant cows will eat more than open (non-pregnant) cows. Finally, some cows are more "feed efficient" than others and despite being in the same lactational or reproductive stage as the other, one may eat less feed to maintain the same condition (or even increase it) than another cow.

A rule of thumb to know is that a cow will not consume the same amount of feed over an entire year. No cow consumes the same amount of feed as another cow, not even on a dry-matter (all water removed) basis.

Answer 2

This all depends on her size, body condition, area of reproductive activity (lactating, what gestation period, etc.) and age. Typically, a cow will eat 2.5% of her body weight per day. Lactating cows eat 3.5% to 4% of their body weight per day (these values are in dry-matter (DM) terms, and may account for both dairy and beef cows)

Typically dairy cows tend to eat more than beef cows (usually by 0.5% to 1% more) because they are of thinner condition and are producing twice or thrice as much milk for longer: for 10 months of the year. An average dairy cow, being a Holstein, weighs around 1500 lbs. So, for lactating Holsteins, they eat (4% of 1500 lbs =) 60 lbs per day DM. Translating that into months, we have to calculate the average number of days in a month for a year, which is 30.42. So per month, a lactating Holstein will eat 1825.2 lb per day per month DM. A dry Holstein will eat around 2.5% of her body weight per day, which translates to 37.5 lbs per day, and thus 1140.75 lbs/day/month DM.

Now it's difficult to simplify things here, but to really keep it simple for day cows, the average rate of intake per 1500 lb cow throughout the whole entire year (not taking into account lactating nor drying up) would have to be 3% per day. 1500 x 0.03 = 45 lbs/day DM. For a whole year, one cow will eat around 45 lbs/day x 365 days = 16 425 lbs per year DM. Translating that into kilograms, (where 1 kg = 2.2046223 lbs and 1 lb = 0.4536 kg), that's 7450.38 kg/yr DM.

Note that ALL the values calculated above are Dry-Matter values. Thus, the TRUE, as-fed values of how much a cow eats per year depends on three main factors: moisture content of the feed that she eats, the type of feed she is fed, and the nutrient quality of that feed. Other factors include the type, breed, sex and reproductive stage of that cow, and her body condition. There is variation in moisture between the types of feed that is fed, and quite often a bovine is not fed the same diet day-after-day for 365 days out of the year. This is the case with beef cattle, as they may be on a diet of dry hay for 3 to 5 months of the year, then switched to lush pasture for the rest of the year. Cows will eat more of a feed if it has a higher moisture content than they will if it's dry. They will also eat more if the feed is higher quality.

Answer 3

It depends on both the cow (size, breed, general health, etc.) and the quality of the pasture (kind of forage, speed of re-growth, etc.).