According to StatsCan, western grain farmers and just about anyone driving across the Prairies, this year’s harvest of cereal crops was phenomenal. With millions of bushels of grain picked up by thousands of combines, tonnes of straw are being thrown out their back ends. Whether it is baled in round or big square bales, a bountiful crop of grain straw can be easily used as an alternative and economical forage source for overwintering beef cows.
The best candidates for feeding straw in winter diets are mature early- to mid-gestation beef cows, which only need to maintain a post-weaning body condition of 2.5-3.0 (re: 1= thin, 5 = obese). These pregnant cows have respective first- and second-trimester nutrient requirements of about 50-53 per cent TDN dietary energy, nine to 10 per cent protein, 0.25 per cent calcium, 0.20 per cent phosphorus and a good complement of essential trace minerals and vitamins. These requirements are only achievable with well-balanced straw diets until the last three months before calving or the onset of colder temperatures, when significantly more nutrients (higher energy) are needed.
The first limiting factor of straw is its high fibre content that quickly fills the cows’ rumen and is slowly digested by ruminal microbes. For example, cereal straws (such as barley, wheat and oats) contain about 70-85 per cent NDF-fibre (44-48 per cent TDN energy) and four to six per cent protein compared to fair quality mixed-grass hay of 55-65 per cent NDF-fibre (52-58 per cent TDN energy) and 11-12 per cent protein.
Still need balanced ration
The implication of feeding low-energy and low-protein straw to beef cows measured against feeding better-quality grass hay is two-fold:
1. A big beef cow is only able to consume about 25-30 lbs. of straw (gut-fill), and
2. Their resident rumen microbes can only digest 60-65 per cent of that amount of straw per day.
As a result, big pregnant beef cows with some fat cover can handle about 50 per cent of their dry matter consumption from straw and the other 50 per cent of the diet should be complimented with more nutritious supplements.
Here are samples of well-balanced straw-based diets for 1,200 – 1,400 lbs. pregnant beef cows that might be fed from late October to end of December:
The feeding costs ($/hd/d) of most of these straw-based rations fall slightly below $1.50 per cow per day, and some are slightly more costly than the predominant grass hay diet (#6). The actual feed ingredient prices of these diets may vary from farm-to-farm, but the chart illustrates what feedstuffs can be used related feeding costs.
Barley and other options
As shown above, barley is the main grain used as supplemental energy for many straw-based cow diets. Its quality is often based on kernel plumpness, bushel weight and the occasional laboratory protein analysis. When barley is fed in any beef diet, the common recommendation is to grind it into coarse hammered kernels to improve digestibility.
In the last few years, commercial screening pellets and corn distillers’ grains have also been used as barley substitutes, particularly when barley prices are relatively high. But realize not all grain screenings are created equal and may consist of various levels of actual grain kernels, oilseeds (such as canola), weed seeds and also cereal stems, pods, chaff and dust. Fortunately, most of these ingredients are ground and heated (weed seed viability is destroyed), before the feed is made into pellets. Corn distillers’ grains have many similar quality issues compared to grain screenings when used as a barley substitute or protein supplement.
Failure to use grain and grain byproducts concentrate along with straw can lead to some dire consequences, such as abomasum impaction. Severely “plugged up” cattle can die within a week without treatment (such as a dose of mineral oil). This can largely be avoided by assuring that the straw-fed beef cows are meeting their energy and protein requirements and have access to adequate fresh clean water at all times.
Most people with experience in feeding cereal straw to beef cows avoid such trouble. They realize no matter how much straw is available, it doesn’t provide the same nutrition as grass hay. It must be supplemented with the right type and amount of other feedstuffs to meet requirements of early- and mid-gestation cows. As cattle get closer to calving the herd needs to be moved to a higher plane of nutrition. †