Adjusting harvest timing improves sugar content and protein synthesis
Research indicates there is a simple, no-cost method of increasing feed value in sweet forages.
Cut them in the evening.
Research scientists Gilles Belanger of Agriculture Canada and Robert Berthiaume of Valacta have studied forage sugar content and feed value.
They presented some of their findings March 4 in a webinar organized by the Beef Cattle Research Council.
“By increasing the sugar concentration in forages, you can improve the performance of ruminants,” said Belanger.
Research shows forages increase their sugar content as they photosynthesize during the day. Maximum sugar content is achieved 11 to 13 hours after sunrise in alfalfa, timothy, tall fescue, red clover and some other forages.
Studies included both spring growth and summer regrowth. Both showed that evening cutting increased sugars, which are also known as non-structural carbohydrates.
Belanger recorded as much as five percentage units more sugar in some cases from evening versus morning cut forages, but the average was 1.8 percentage units.
The material will lose sugar as it sits in the field after cutting, but will still have more than morning cut forage at the end of the wilting period, he added.
Sugars are maximized if the forage is cut in the evening and then ensiled the next day. Silage will have better fermentation with lower pH and ammonium concentration.
Berthiaume discussed research on beef and dairy cattle feed intake and its relationship with forage sugar content. He studied animals fed from two feed bunks, placed side by side. One contained forage cut in the morning and the other had forage cut in the evening.
“Very early on, the animals definitely preferred the p.m. cut hay,” he said. “Cattle are able to detect the presence of sugars, probably through the smell, and do eat more.”
After a time, intake between the two forages evened out. Researchers don’t have a good explanation for this, but speculated that animals instinctively try to balance the supply of sugars and protein in the rumen.
He also studied the sugar effect in pastures by managing cattle access through strip grazing. Animals were enticed to eat in new pasture at 7 p.m., noon and at night.
Results showed cows that were offered new pasture in the morning lost a small amount of weight over the summer, while their calves gained about 1.2 kilograms per day.
Cows that were offered a new strip of pasture 11 hours after sunrise gained weight, and their calves gained about 1.28 kg per day.
“We think that the reason why all of those improvements that we have seen occur is because sweet forages do improve protein synthesis in the rumen. Therefore bacteria are working for you in this case,” he said.
Berthiaume fed alfalfa haylage to cows in late lactation in one of three dairy studies, and results showed a significant increase in dry matter intake and milk yield.
There was also a decrease in milk urea nitrogen, which suggested cows fed evening-cut material made better use of protein.
“We concluded from that study that an increase of 2.3 units of sugars in a … straight forage diet, fed to late lactation cows, we saw an increase in dry matter intake and an increase in milk production, and also this was associated with a reduction in milk urea nitrogen,” said Berthiaume.
“Three different lactation studies with lactating dairy cows, (there were) benefits with mid and late lactation cows (and) limited benefits to primiparous (first calf) cows in early lactation.”