The 2010 growing season saw double the historic average precipitation across most parts of Saskatchewan and near triple in some localities. It was welcome coming out of a drought in some areas; not so much in others with ample moisture to start off the season.
With a similar scene unfolding this year across many parts of the Prairies, Dr. Greg Penner, assistant professor with the department of animal and poultry science, and Dr. Steve Hendrick, assistant professor with the Western College of Veterinary Medicine at the University of Saskatchewan, shared some of the lessons learned about forage quality from 2010 with producers during the Western Beef Development Centre field day at the Termuende Research Ranch near Lanigan, Sask.
In general, the heavy rainfall took a big bite out of feed quality and highlighted the importance of paying attention to fibre content in perennial and annual forages baled for hay and put up as silage, Penner says. Producers have been well coached to look at protein and energy levels when formulating rations and generally assume that if those requirements are met, the cows will winter fine, however, there were a lot of thin cows coming into calving this spring.
In most instances, it wasn t for lack of feed in front of the cows. The widespread issue was that the neutral detergent fibre content of the forage was generally on the high side, while the crude protein and total digestible nutrients (energy) were on the low side.
Typically in Saskatchewan, alfalfa hay cut in mid-bloom has an average protein content of 16 to 18 per cent, energy of 60 to 65 per cent and fibre content of 45 to 50 per cent. Alfalfagrass hay generally averages 13 to 16 per cent protein and 56 to 58 per cent energy, with 54.5 per cent fibre.
Samples of the 2010 alfalfa hay crop from eight regions across the province averaged 14.6 per cent protein, 57 per cent energy and 57 per cent fibre. Alfalfa-grass hay averaged 12.7 per cent protein, 56.9 per cent energy and 62.4 per cent fibre.
As for fibre content in alfalfa hay, the low end of the range was close to average in two regions, but the high end ranged from 60 to 72 per cent across the province. The fibre content of alfalfa-grass hay ranged all the way from the low of 43 per cent to the high of 77 per cent in the North Battleford region alone.
The prolonged wet conditions affected fibre content only insofar as it delayed cutting beyond the optimal stage of maturity, Penner explains. As plants mature, the leaf-to-stem ratio decreases and changes in nutrient content can occur quite quickly. The leaf material contains much of the protein and digestible fibre, while the stem is largely fibre, some of which is not digestible. Thus, the change in proportion of the leaf and stem can have a large impact on quality.
The lower-than-average protein and energy content was due to large plant volume, which has the effect of diluting, or lowering the concentration of total nutrients in proportion to plant tissue, even after dry-down.
High water content in the forages has implications during the grazing season, too. Cows have to be capable of increasing forage intake to obtain an adequate level of nutrition because they are consuming so much water. Dr. Paul Jefferson showed that the crude protein level in annual forages decreases in direct proportion to increasing levels of precipitation by applying differing amounts of water through dripline irrigation on barley, oats and millet.
In drought years, the opposite would apply with the water content lower and nutrient concentration higher in smaller volumes of plant material.
Leaching is another factor that contributes to a decrease in forage quality during wet years, Penner adds. Rainfall on the windrows and bales can cause leaching of soluble nutrients from the forage. Excessive moisture can also cause movement of nutrients within the field, for example, nutrients may accumulate in low areas due to run-off, or move below the root zone making them unavailable to plants during the growing season.
THE EFFECT OF HIGH FIBRE
When dietary energy is low, the fibre content of forages in the diet limits how much forage a cow is able to eat. Even though she may appear full and there is hay left in front of her, she will be malnourished because she is physically incapable of consuming enough hay to meet her basic nutritional requirements during gestation and after calving, without factoring in body condition score and weather effects.
Penner and Hendrick work through an example to illustrate this point.
1. How much will a cow eat?
Dry matter intake on a daily basis is about 2.5 per cent of a cow s body weight, equating to 35 pounds of dry matter for a 1,400-pound cow. However, a cow is capable of eating only 1.2 per cent of her body weight in fibre, equating to 16.8 pounds of fibre per day in the total diet for 1,400 pounds per cow.
2. What are the requirements of a 1,400-pound cow?
During the second trimester, mature beef cows need to consume a diet containing about 50 per cent energy and seven per cent protein, which equates to 17.5 pounds of energy and 2.5 pounds of protein. Without increasing feed intake, the same cow requires 21 pounds of energy and 3.2 pounds of protein during the third trimester. After calving, she needs 22.8 pounds of energy and 3.9 pounds of protein in order to produce sufficient milk and ensure she starts to cycle again before the upcoming breeding season.
3. Does your hay quality meet the need?
Fed at 35 pounds of hay on a dry-matter basis (approximately 40 pounds as fed), hay with seven per cent protein and 55 per cent energy, would provide 2.5 pounds of protein and 19.3 pounds of energy on a dry-matter basis to meet the requirements of a 1,400-pound cow in the second trimester. To meet her needs during the third trimester, she would require hay with nine per cent protein and 60 per cent energy. After calving, her nutritional needs could be met with hay with 11 per cent protein and 65 per cent energy.
4. What about fibre content?
While the energy and protein values may appear to be sufficient in order to meet the nutrient requirements, remember that cows require pounds of energy and protein, not percentages. To ensure that fibre doesn t limit the intake of energy and protein, divide the pounds of fibre she is capable of eating (1.2 per cent of her body weight, which equates to 16.8 pounds in this example) by the fibre content of your forage. If your alfalfa hay was on par with the 2010 provincial average of 57 per cent fibre, she would have been able to eat only 29.5 pounds of hay per day, which is far less than the 35 pounds she should have eaten.
5. Are there nutrition gaps?
Again using the 2010 provincial average for alfalfa hay of 14.6 per cent protein and 57 per cent energy, they calculate how much of each nutrient would be available on a dry-matter basis in 29.5 pounds of hay with 57 per cent fibre. Based on these values, a cow would be consuming 4.2 pounds of protein per day (29.5 X 14.6 per cent), which would more than meet her requirements right through calving, however, she would be short on energy, with only 16.8 pounds of energy per day (27.5 X 57 per cent) during that same time period.
This deficiency in energy caused by high fibre content, explains why cows lost weight even though they had lots of feed available.
6. What s the remedy?
Your options would be to purchase hay that meets her requirements, or bring in high-quality hay to blend with your high-fibre hay, or supplement the hay with grain to bring up the energy level in her diet.
The lesson learned from 2010 is that by the time you have thin cows, it s too late to take corrective measures and the nutritional deficiencies will be amplified as calving approaches and post-calving, Penner says.
First, make every attempt to graze or cut perennial and annual forages at the optimal time to balance yield and quality. If wet weather delays grazing or swathing, it s possible to manage the feed you are dealt with as long as you know what you have, he says. This requires testing of your forages to determine energy, protein and fibre values alongside knowing the requirements of your cows as gestation progresses.