The recommended stages of maturity for cutting annual cereals for whole-crop forage are based on what’s good for silage. We just always assumed if it works for silage it must work for greenfeed and swath grazing too.
Researcher Greg Penner isn’t so sure now, based on some research he’s been involved with at the University of Saskatchewan.
In a nutshell, they’ve found waiting to cut cereal forage until a later stage of maturity may improve digestible dry-matter (DM) yield without negatively affecting intake, thereby improving animal gains per acre and reducing the cost of feed.
“Crops for silage require certain levels of carbohydrates and high moisture content to pack and ferment properly and digestibility increases during storage, but none of those apply when the crop is taken as dry whole-plant forage for greenfeed or swath grazing,” says Penner, an assistant professor of ruminant nutrition with the Department of Animal and Poultry Science.
“We know that whole-plant yield increases as growing degree days increase, so we are giving up potential yield by cutting the crop before it matures. We know, too, from Dr. Vern Baron’s work in the early 1990s, that organic matter digestibility when measured in vitro (in a test tube) doesn’t change with maturity.”
Penner and his associates set out to determine whether the maturity levels recommended for silage — early dough for barley, late milk for oats, soft dough for wheat and two weeks after heading for millet — make sense for greenfeed bales or swath grazing.
Small plot trials using CDC Cowboy barley, CDC Weaver oats, an experimental forage wheat line (07FOR21), and red proso millet were grown in 2011 and cut at four stages of maturity: head elongation, late milk/early dough, hard dough, and mature.
The highest DM yield was from mature crops and chemical analyses revealed more feed quality advantages than drawbacks as the crops advanced in maturity.
Organic matter increased as a percentage of DM as did non-fibrous carbohydrates (NFC), which takes in all of the starch and sugars.
Neutral detergent fibre (NDF) and phosphorus content decreased. The decline in phosphorus would have helped bring it more in balance with calcium, had calcium not decreased as well. Decreases in calcium and crude protein (CP) were the chief disadvantages to letting these crops mature before cutting them.
The trend was similar for all crops except the wheat, where they noted an increase in NDF as time went on.
Penner uses the barley findings to illustrate the effect of advancing maturity on feed quality.
Dry matter content jumped from 14 per cent at head emergence, to 23.5 per cent at the early-dough stage and almost doubled again, reaching 55 per cent by maturity. From heading to maturity, the organic matter rose from 89 per cent to 93 per cent, the NFC climbed from 8.7 per cent to 36 per cent, and NDF fell from 59.5 per cent to 45.7 per cent. Phosphorus content dropped by half from 0.43 to 0.26 per cent, as calcium content fell from 0.52 to 0.30 per cent.
Crude protein as a percentage of DM declined steadily from 18.5 per cent at heading to 14.1 per cent at early dough and 9.4 at hard dough, however, when measured as total CP yield, the level remained steady as maturity advanced.
Feed tests are useful but the ultimate measure of a feed’s quality is animal performance.
The Weaver oat crop seeded May 17 was cut at late milk (July 12), hard dough (August 13) and full grain (August 28). Again, DM yield at late milk was lower than at the hard-dough and full-maturity stages, measured at 211, 472 and 417 tonnes per hectare, respectively.
The nutritional composition of the oats changed significantly from the late-milk stage to the hard-dough stage, but very little after that.
Comparing late-milk oats to mature oats, as a percentage of DM, NDF decreased from 60.8 to 54.3 per cent; crude fat increased from 2.6 to 3.7 per cent; NFC increased from 19.6 to 25.5 per cent; and crude protein decreased from 8.2 to 7.7 per cent. Ash (the non-digestible portion) started at 9.5 per cent, dipped to 9.1 per cent at hard dough and increased again to 9.8 per cent at maturity.
“We saw the reduction in NDF as the crop matures, so more starch was available, but we didn’t know if it was really available to the cows,” Penner says.
Cows were fed balanced rations containing 60 per cent oat forage cut at the three different stages of maturity. A concentrate of alfalfa pellets, barley grain and canola meal fed separately and a vitamin-mineral mix rounded out the ration.
The positive for Penner was that they got more yield as the oats matured with no loss of intake. The cattle didn’t eat any more or less of the oats at any stage of maturity.
They also found out that the starch in the later-cut forages is digestible. Cows fed hard-dough and mature oat forage had a lower rumen pH than the cows fed late-milk forage. True, low rumen pH can lead to digestive upsets; however, it was considered a positive in this study because it indicated that the starch was available and rumen pH didn’t drop to a level that would make it a health concern.
This year Penner and his associates plan to confirm their findings.
— Debbie Furber is a field editor for Canadian Cattlemen at Tisdale, Sask. This article appeared in the June/July 2013 edition.