Grazing management — where quantity is king


To be a better grazing manager or “grazier” and get higher performance out of cattle it helps to understanding more about how they eat. With a better understanding of grazing mechanics and intake, it is possible to put animals in situations for better grazing performance success.

The Western Forage/Beef Group in Lacombe has compiled a great deal of research information to help graziers understand how cows graze.

“Forage has a lot of water in it,” says Grant Lastiwka, a grazing/forage/beef specialist with Alberta Agriculture and Rural Development. “Realistically, there can be 90 per cent water and only 10 per cent dry matter in lush spring forage. A cow has to work hard to get the food she needs. A 1,500-pound cow would have to take in 450 pounds of forage to get three per cent dry matter intake. While cows can do this, they are limited by the number of bites, density of forage/unit area, canopy structure, and the amount of time each day they spend grazing. As well, the energy spent grazing is about 25 per cent more than eating hay or silage stored forage. This varies with the pasture condition and type as the faster the cows can fill up with reasonable quality forage, the less energy they use for maintenance, making more available for performance.”

Animal intake varies greatly. As ‘Low Cost Cow’ educator Dick Diven says, “There are three things you cannot discuss without getting into an argument: politics, religion, and dry matter intake.”

Animal performance is about 70 per cent related to intake (quantity available). Nutritional value (quality available) is the remaining 30 per cent. That is why it is so important to manage animals for quantity factors that allow for high forage intake.

Taken one step further, respected grazing instructor Jim Gerrish stated that, “Close to 70 per cent of intake (quantity of forage dry matter consumed) is related to the residual left at the end of the grazing incident.”

In the late 1990s and early 2000s, Dr. Vern Baron with the Western Forage/Beef Group at Lacombe, carried out a seven-year grazing system comparison trial incorporating this theory. His grazing plan was based on a number of variables. One crucial variable he followed was making sure that at the start of each day he had at least a minimum of forage dry matter volume of five per cent of animal body weight. Because a yearling may eat between one and 3.5 per cent of its body weight, Baron was making sure that forage quantity was higher than needed and a substantial residual was left behind at the end of the grazing day. For example, a 500-pound animal was allocated a minimum of at least 25 pounds of forage dry matter available every day. If you have 10, 500-pound animals and planned for a three day grazing period you would need 10 animals x 500-pound/animal x 5 per cent of body weight x 3 days or 7,500 pounds of forage dry matter allocated for that three-day period. Baron found that animal average daily gain in the five trials each year over those seven years was quite similar. This occurred even though forage quality at times during the summer period could be quite different in each of the systems.

“Animals can only graze for a certain amount of time before they need to rest and ruminate, which is the activity of re-chewing consumed forage to break it down to smaller particle size for further digestion,” says Lastiwka. “With cattle, the ‘roping in’ of the forage is accomplished by the tongue and lips. The fodder is clamped between the incisors and dental pad and sheared off or torn by a head jerking action. This occurs about 20 to 45 times per minute for long periods of time before a beef animal gets tired. If we use an example of a 440-pound animal eating three per cent of its body weight (13 pounds), it would take an average of 6,000 bites per day. Eating at a rate of 20 bites per minute could take five hours of steady grazing. Fortunately, bite size is greater on more dense forage stands. If the stand yield varied from 550 to 2,200 pounds of forage per acre, the number of bites would vary from 3,000 to 12,000 per day to get the same 13 pounds of forage. Therefore, better animal performance is achieved with less energy spent working and more energy directed to gain in a more dense forage stand.”

A beef cow with no calf-at-side may graze for four hours to meet her needs. A cow with calf-at-side on range or pasture will graze for eight hours or more. A cow will seldom graze for more than 12 to 14 hours per day as time is needed to walk, go for water, rest, ruminate and carry out normal herd social activities.

“You can tell a yearling or cows grazing performance by the hours it grazes,” says Dr. R.L. Dalrymple, who spent years in grazing research at the Noble Foundation in Oklahoma. “If a yearling is grazing for 11 hours per day, you will not get good performance.”

“Realizing the need for high forage quantity available and adequate residual left after a grazing event, we can better understand why many skilled graziers try to make sure they have about 1,500 to 1,800 pounds of forage left as residual after a grazing period,” says Lastiwka. “This is a good way for them to try to make sure that animal intake was probably not limited during a grazing period.”

Grazing sounds like a simple act but it has many variables determining animal maintenance and performance end result. The success graziers have is determined by the performance of their animals. It only makes sense to optimize that performance for growth or gain. For yearlings, producers want higher pay weights to have more to sell. For cows they want to gain body condition score so that animals experience less winter hardships and they want to be able to adjust a ration to reduce the cost of feed consumed.

“Cow or yearling performance revolves around managing summer grazing for optimum animal performance,” says Lastiwka. “Wisely grazing for well-managed pastures that have suitable volume at grazing turn-in and residual at the end of the grazing period will result in improved animal, plant, soil organism and overall financial performance.”

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