It's hay buying season; a stress filled marathon of heavy lifting during the hottest time of the year! At this moment in early August, first cutting has been put away across the country, and we're in limbo waiting for second. While we wait, I will offer an explanation of why you might choose one cutting over another and debunk some myths especially about carbohydrates. However, it's very, VERY important to understand that hay production is more like a fluid art form than a strict manufacturing process. There are over a dozen factors that could influence the quality of the hay that's available to you, so take each of my educated guesses as guidelines and NOT absolutes. The only thing absolute about a batch of hay is a well sampled forage test result.
Cutting Number VS Stage of Maturity Defined
It's important to first define what we mean by the term "cutting" and separate it from the term "maturity". I'll use my own hay production in Southwest Montana to illustrate. The cutting number is quite simply the progression of harvests throughout a calendar year. This is irregardless of the crop type (i.e. warm or cool season grasses or legume hay). For a cool-season grass hay field in Western Montana, the grower may harvest for the first time in late June/early July. This is first cutting. The grower then reapplies fertilizer and continues to irrigate before harvesting again in late August/early September. This is second cutting. For MOST grass hay fields across the Western and Northern US, it's nearly impossible to get enough tonnage grown for a third cutting before fowl fall weather sets in. Therefore, third cutting grass hay is rare. Third cuttings are a lot more common with alfalfa hay. You'll often find third and even fourth or fifth cutting alfalfa hay in areas where there are a lot of dairy cows.
Maturity of the crop when cut is different than cutting number. Whereas cutting number refers to a sequence of harvest dates, maturity refers to the plant's stage of reproduction at a given moment. Unfortunately for horse hay shoppers, maturity on a given date- let's say 4th of July, can differ wildly between species (Fransen * Griggs, 2002). If you watched an untouched field of grass throughout the year, you would witness it's entire maturity cycle. Check out this link at Oregon State University for images of a grass plant's vegetative, transitional, and reproductive phases. However, when you harvest the grass once or twice plus fertilize and irrigate (or not) to optimize your hay production, you are interrupting that cycle and changing variables. This is why you have to be very careful about making predictions based on cutting number alone- especially carbohydrates!!!
The interaction between cutting number and stage of maturity is complex with both environment and human factors. For example (going back to the cool-season grass field in Western Montana), the hay producer could decide to harvest first cutting when the grass plant is in early, mid or late maturity. If they decide to cut during very early in the plant's maturation (let's say early June), the hay produced will most certainly be very digestible with high calorie and protein values, but they will also lose out on total tonnage, because there is still a lot of biomass to be grown. If the hay producer cuts first cutting during late maturity (let's say mid-August), the digestibility will be much reduced, but there will be a lot more biomass and tonnage to sell. So, many growers are shooting for this delicate balance at mid-maturity where digestibility and total biomass intersect perfectly. That is, of course, if Mother Nature cooperates.
Here's what you need to know and underline= maturity of first cutting should be a top consideration in your decision making and will be summarized by the Relative Feed Value Number- read "Relative Feed Value: The Number One Most Useful Number for Feeding Horses" by OCEN, LLC.The Difference Between Cuttings
The most important take-away from this article is this- it depends!!! What's really fun to realize about this information is that scientists have understood the animal's response to cutting and maturity for a really long time. When you google "first versus second cutting" in Google Scholar, you get articles dated as far back as 1932. We've known how forage cuttings and stage of maturity affects dairy cows for 100 years, but horse owners are just starting to catch up! Most of you are purchasing a cool-season grass hay, so I will start with some assumptions about first versus second cutting for those species and then move onto alfalfa hay and teff hay.
Cool-Season Grass Hay Species (i.e. timothy, orchardgrass, bluegrass, fescue):
On average, first cutting is higher in fiber and lower in digestible energy compared to the average second cutting. Let me say this another way; second cutting is almost always higher in relative feed value (RFV). In my own purchased hay, first cutting had a RFV of 94 and second cutting had a RFV of 107. Therefore, if you have a herd of fatties, shop for MATURE first cutting hay. If you have a herd full of skinnies, shop for second cutting cool-season grass hays.
Alfalfa Hay:
The ratio of leaf to stem increases with each cutting, so if you're trying to put weight on a picky horse, you'll want to try to get second or third cutting with more leaf and less stem.
Warm-Season Teff Hay:
According to my research in 2017 and 2018, second cutting teff grass hay was significantly higher in fiber and lower in digestible energy values compared to first cutting. This is the opposite from your standard cool-season grass hays. Do NOT buy teff hay without a forage test reporting calories and carbs. I've seen a lot of what I am referring to as the "TEFF TRAP"[LINK TO READ HERE] lately where horse owners are incorrectly assuming all teff hay is the same.
Is One Cutting Lower in Non-Structural Carbohydrates?
The simple answer is NO! Absolutely not. Do NOT use cutting as a predictor of non-structural carbohydrates. In my research of how to grow low-carb hay, the primary factors influencing non-structural carbohydrates (NSC% = WSC% + Starch%) were the right application of fertilizer, time-of-day, and maturity at harvest. The cutting number was a secondary factor even when the amount of fertilizer and water was held constant for the cutting. Therefore, I DO NOT recommend that you make buying decisions based on cutting number when looking for low-carb hay. However, you should by ALL MEANS make buying decisions based on cutting number when you are looking for low-calorie versus high-calorie hay! And really, you should be starting there.
SUMMARY
Relative caloric density (digestible energy measured in Megacalories) is basically the ONLY forage quality factor that I will gamble real money on when debating which cutting number to buy. As far as non-structural carbohydrates...I researched how to make low-carb hay for four years, and even I won't gamble on a hay's carbohydrate values. There are too many factors involved. And another important point, when I say "relative", I mean that in a really important way. We can only compare first and second cutting RELATIVE to each other from the same field. Each field is grown and harvested differently, so don't make assumptions across different fields. Again, there are too many factors involved for you to make accurate predictions. Get a forage test done. HERE IS A LINK that tells you how!
REFERENCES
Fransen, S.C. and T.C. Griggs. MANAGEMENT OF COOL-SEASON GRASSES FOR HAY PRODUCTION AND QUALITY. In: Proceedings, Western Alfalfa and Forage Conference, 11- 13 December, 2002, Sparks, NV, UC Cooperative Extension, University of California, Davis 95616 (see http://alfalfa.ucdavis.edu).