You will often hear it said that Icelandic sheep can thrive on grass and hay alone; no grain is necessary. This can be true; I would even argue it is the preferable way to feed them, as you don’t get the added phosphorous from the grain that can contribute to urinary calculi in rams, and the sheep don’t get “hot” like when on grain. (By “hot”, I mean hyper, like a kid on caffeine.) Plus, they don’t get whiny for their “treats.” You see, Icelandic sheep, being a more primitive breed, have a larger rumen proportionally than most other sheep. This means they can process more hay and thus extract more nutrients than sheep with smaller rumens. However, even Icelandic sheep rumens have their limit, and hay quality must be considered when choosing a diet. If the hay has few enough nutrients that the sheep cannot physically eat enough to extract enough of these nutrients, then other sources of nutrients, such as grain, will need to be provided. However, I have written this article with the specific intent to discuss hay quality, and not the supplements that may be needed. The following is what I have found useful when finding hay, what gives me a better idea as to whether or not that hay is sufficient to meet the needs of my sheep.
Hay is not just hay. Hay varies massively in its nutrient contain depending on when it was cut and where. When considering hay quality, the most important aspects to consider are protein and rfv (relative feed value), which are determined by lab analysis. (A forage analysis is inexpensive and can save a lot of headache.) Protein content is what is going to determine how well the hay can keep weight on the sheep. It is also necessary for the production of milk in lactating ewes. How much protein a sheep needs depends largely on life stage and pregnancy status. I have included below a few figures taken from “Nutrient Requirements of Sheep, 6th revised edition, 1985″ by National Academy Press. I highly recommend owning this book, as it has proven very valuable to me in understanding sheep nutrition and what the various nutrients do.
Example 1: 110 lb. Maintenance Ewe: Needs about 10% protein hay if fed 2.2 lbs of hay per day (the minimum amount of dry matter she should consume). That would only be about 7% protein hay if she were to consume 3 pounds a day. These figures are based on the ewe needing to consume 0.21 lbs of protein every day to maintain her weight.
Example 2: 110 lb. Lactating Ewe, first 6-8 wks: Needs have increased to 0.67 lbs of protein necessary per day. Her dry matter need has increased to 4.6 pounds per day. This means that if she got the minimum amount of dry matter, she would need hay with about a 15% protein content.
Example 3: 66 lb Replacement Ewe Lamb, over 8 weeks old, less than 4 mo.: This growing lamb needs 2.6 lbs of dry matter per day, and must consume 0.41 lbs of protein per day to maintain her growth. This would mean she’d need hay that was about 16% protein if she were consuming the minimum amount of dry matter. (Again, if she consumes more pounds of dry matter per day than the minimum, the percentage of protein necessary decreased.)
These examples are just to give an idea about what protein means to sheep and how the amount of it needed changes with the sheep’s age and condition. There are obviously many more life stages; this is not meant to be complete. But if the daily protein requirements are not meant, the sheep either will not grow, or will even lose weight.
I mentioned that the stage at which grass is cut affects protein content. Grass at an earlier stage of growth has a higher protein content than grass at a more mature stage of growth. The highest protein grass is found just before seed heads form. I have seen plain grass hay have protein contents as high as 16% when cut at this stage, though the cuts are lower volume. Even when seed heads form, but before the seeds mature and harden, is also a fairly high protein stage. A little volume is gained at this stage, though a little protein content is lost compared to cutting it younger. This stage often yields 10-13% protein, based on the analyses I have seen. Once the stems start to harden and become woody, and the seed heads ripen and turn yellow, a lot of the protein content is lost. This hay will often have around a 7% protein content, and be far less palatable.
RFV (Relative Feed Value):
Now I also mentioned rfv. This is the palatability of the hay; how available the nutrition is to the animal. A low rfv is typically indicative of a very stemmy cut of hay. The grass was cut when it was quite mature, resulting in a tougher, stemmier consistency of hay that is harder to eat and digest and in which the nutrients are harder to extract. If you have ever seen cattle or grinding hay advertised, this is typically what that is. Sheep in particular seem very picky about eating stems; mine just won’t. Lots of stems mean lots of waste around the feeder, and also have a tendency to clog my feeders. Likewise, a high rfv typically means a younger cut of hay; the grass was cut near its peak of nutrition, before it got the chance for its stems to get woody and for seed heads to form. What defines a high or low rfv? I personally prefer to get hay with at least an rfv of 100. This is pretty palatable hay that also usually has a decent protein count. (High rfv tends to also correlate with a high protein content, because to cut the grass at a time when it has a high rfv is also to cut it at the stage where is has a good protein content.) Some dairy hay, which usually also contains alfalfa, can have rfv values over 200, just for some comparison.
Hay Color: I only mention this because I often see hay advertised as “nice and green” as a measure of quality. All the green color means is that the hay is fresh enough that the sun hasn’t destroyed the chlorophyll yet. It has very little to do with nutrition. (Though green hay is often fresh enough that it likely still has its vitamin A intact; this is the first nutrient lost with time. Most other nutrients are actually very stable in hay if they are protected from moisture.) A person can buy wonderfully green hay that will cause sheep to lose weight over the winter because they can’t eat enough of it, because it was cut mature and has a low rfv and protein level.
Dry Matter: This one isn’t a nutrient, but is important for determining the actual levels of nutrients within a feedstuff. All figures given assume 100% dry matter. This means there is no moisture in the feed, which in reality doesn’t really happen. Most hay is somewhere in the ballpark of 10% moisture content. This means that 10% of the bulk is water, and does not count toward your total intake. If you have 3 lbs of hay, and it is 10% moisture, then 0.3 lbs of that hay is water. You must subtract that from the total amount of hay to get the actual amount of dry matter present. In the 3 lbs of hay example, that means you have 2.7 lbs of dry matter. This applies to all feedstuff given to a sheep, not just hay. However, I am only focusing on hay in this article.
The above was meant as a summary to allow a shepherd to understand the main components of hay quality. This should provide a basis for understanding what a sheep needs based on the other factors involved: age, genetics (some sheep have larger rumens than others), and the bred/not bred status of ewes. Time of year, namely temperature, also plays a large role.
I have already briefly discussed in the section about protein the role age and the bred status of a ewe plays on a sheep’s needs. However, when discussing age, one must also consider that sheep their first year are smaller than full adult size. This also means they have smaller rumens. Their ability to process nutrients from hay on a daily basis is thus diminished when compared to adults; they just do not have the physical capability of getting as much out of their hay. What this means is that one can only increase the dry matter to a certain level before the sheep just cannot physically process anymore. Take for example the ewe lamb mentioned in the section on protein. She needs 2.6 lbs of dry matter per day, and 0.41 lbs of protein.
So if her hay were 16% protein and 10% moisture, then…
3 lbs of hay would provide 2.7 lbs of dry matter (3 lbs hay * 0.1 moisture = 0.3 lbs moisture. 3 lbs hay – 0.3 lbs moisture = 2.7 lbs dry matter.) At 16% protein, this would mean 0.43 lbs protein in this 3 lbs of hay. (2.7 lbs dry matter * 0.16 protein = 0.43 lbs protein) This would be sufficient to meet her needs.
If her hay were 10% protein and 10% moisture, then…
3 lbs of hay = 2.7 lbs dry matter. At 10% protein, this would mean 0.27 lbs of protein in this 3 lbs of hay. This would not meet her needs. However, if you were to give her 4 lbs instead… 4 lbs hay = 3.6 lbs dry matter. At 10% protein, this equals 0.36 lbs of protein. Still not enough. You’d need at least 4.1 lbs of dry matter per day to meet her needs. (0.41 lbs protein / .1 protein = 4.1 lbs dry matter) Add 10% onto that to account for moisture… (4.1 lbs dry matter = 90% or 0.9; X lbs of moisture = 10% or 0.1. 4.1 lbs dry matter/X lbs hay = 0.9/0.1 ; 4.1X = 0.41 ; X = 0.46 lbs of moisture.) So 0.46 pounds of moisture accounts or 10% of the total; add this to the dry matter count, 4.1 lbs, which accounts for 90 % of the total, and you get 4.56 pounds of hay per day needed to provide enough protein. At 10% protein, this is the minimum amount of hay the ewe lamb can be fed.
So now lets look at 7% protein hay, which is not too uncommon if you buy late harvested, untested hay. Hay like this is quite common for farmers in our area to produce; they just wait for full volume to be reached before harvesting, which means lots of stems and seed heads and little protein. 3 lbs of this hay at 10% moisture would yield only 0.19 lbs of protein. It would take 5.9 pounds of dry matter to reach the required 0.41 lbs of protein. When moisture is added back in, you are looking at 6.6 lbs of hay needed each day to meet the protein requirements. And if the hay is this low in protein, it is probably also low in rfv and will have a lot stem waste. The 6.6 lbs would be what actually needs to be consumed: more would have to be given to account for the waste. If it is even just a 10% waste, you would need to provide 7.3 pounds per day to that ewe so that she can eat enough.
So to summarize: At 16% protein, the ewe lamb would only need to eat about 3 lbs of hay per day; at 10% protein, about 4.5 lbs per day; at 7% protein, she’d have to consume about 6.5 pounds of hay per day just to meet her needs. That is how much difference hay quality can make.
I mentioned before that rumen capacity is limited, especially in youngsters. The question becomes; can this hypothetical ewe lamb physically consume 6.5 pounds of hay per day? Does she have that capacity? I don’t know what the actual capacity of the rumen on a lamb is, but I do know that my lambs only seem to eat about 4 lbs of hay per day, based upon how much I must feed them on a daily basis.
Then you must consider too the last factor that I had not yet discussed; that of winter temperatures. Below a certain temperature point, the calorie needs of a sheep start to increase as that sheep burns more energy to keep warm. In a cold winter, those sheep are going to need to consume even more hay yet, beyond the numbers mentioned above.
Where I am going with this is that young growing lambs, as we head into winter and haying season, may not be able to physically eat enough of a low protein hay to meet the required daily nutrient needs. The sheep will then have to burn his or her reserves to make up the deficit, and thus lose weight. Worst case, a sheep can literally starve to death despite being provided with unlimited amounts of hay if the hay is too stemmy and low protein. This is why it is so important to understand hay quality.
I want to mention here briefly that I have only been talking about hay in this article. This is what one would need to know if he or she wanted to raise his or her sheep on hay or grass alone. A person can get away with using low protein hay if that person is willing to add other feedstuffs on top of the hay, such as grain or alfalfa cubes or lamb pelleted feed. There are many options to adding more protein in addition to hay, but that is another topic.