Weather has a huge impact on forage quality. This year is no different. From the high rainfall areas in the northern half of the province to the dry conditions in parts of south; we are starting to see trends in feed quality from each region. Localized areas will be similar in quality, but each farm will be different depending on the type and age of the forage stand, soil fertility, rainfall, temperature and management.
The plant has one objective during a growing season. That is to produce seed so that the stand can be sustained. If moisture is abundant, there is large amounts of growth. When it is dry, the plants restrict growth and produces seed earlier in the season. Plants can shut down three weeks earlier (or more) than normal. The differences in growing season impacts forage quality.
Mineralization or the release of nutrients from the soil is reduced when drier conditions occur. This reduces the amount of nutrients available for the plants to use. For example; the amounts of phosphorus and magnesium available to the plants may be lower compared to a year with good moisture. But depending on overall growth or yield, nutrient levels in the plant can actually be higher than in a year with good growth. The available nutrients in a dry year are not diluted down because of the lower yield and thus can be higher than normal. This is especially true with protein. With higher temperatures commonly experienced in a drier year and an abundance of sunshine, the photosynthesis process is very efficient and is driving the conversion of available nitrogen into protein.
With high rainfall and wetter conditions, the effect on overall quality is opposite to that of dry year. Yes, mineralization increases because the soil will release more nutrients into the soil water, but there is a limit to the total amount of nutrients available to plants each year. The dilution effect due to a high yield has a large impact on mineral and trace mineral concentrations in the forage. This is an oversimplification, but if the yield is three times higher than average, then the concentration of a nutrient is roughly one-third of normal. Unfortunately, the high yield is working against nutrient concentrations.
The one nutrient that is contrary to the dilution rule is Manganese. This trace mineral increases in concentration on a wet year. Levels can be 2 to 4 times higher than average. Average concentration for Manganese is 40 mg/kg (or parts per million – ppm). On a wet year, it is possible to have levels up to 120 mg/kg or higher. In this situation, it is possible to reduce the supplemental Manganese in the mineral supplement, or if very high, can be eliminated all together. From experience, very high Manganese concentrations can interfere with reproductive efficiency.
Forage quality is impacted by the type of forage present in a stand. Legumes such as alfalfa, clovers, sainfoin, cicer milk vetch and bird’s-foot trefoil are higher quality forages than grass species. Higher protein in the legumes reduces the need for canola meal, distiller’s grains or soybean meal thus reducing winter feeding costs.
The legumes contain more calcium than the grasses and more protein. Having legumes in the stand are a benefit when trying to balance a ration. To adjust calcium levels in a ration, limestone (38% calcium) is commonly added to supplements, minerals, and premixes. Unfortunately, if included in a free choice mineral, it reduces the acceptability of the product. This problem is resolved by adding a flavouring agent or other ingredients (such as anise - licorice flavour, wheat mids, distiller’s grains) to the mineral. It is more common to have a reduction in mineral intake when there is phosphorus in the mineral.
One of the two biggest influencers on forage quality is the maturity of the crop. As a crop grows and matures, quality decreases. Research that was done through the Soil and Animal Nutrition Lab measured yield and how maturity affected feed quality on thirteen different grass species (Sulieman et. al., Journal of Range Management 52:75–82 January 1999). Forages were cut on a weekly basis starting when the plants were at the 4 to 5 leaf stage. Data from the dry year of 1992 found that yield increased up to week eight and then declined. In 1993, a year with good moisture, yield increased up to week 12. Quality is negatively impacted as the forage matured. From the 1992 data, fibre levels increased by an average of 3 % per week. This reduces digestible energy content by 2 % per week. Protein decreased by 2.5% per week. Waiting for a higher yield by not cutting or being delayed by bad weather dramatically reduces quality.
The second influencer is rain damage when the crop is laying in the swath. Loss of soluble carbohydrate and protein occurs. When the cut plants dry down below 40% moisture, the cell walls rupture and make the nutrients susceptible to leaching. Many times, a hay crop that is a day or two away from baling receives a rain. This results in lower energy and protein content, and higher fibre levels. Voluntary feed intake is reduced because it is more difficult for the animals to digest the higher fibre forages.
Feed samples I have received or taken this year, have variable quality. In central and northern Alberta, with cooler temperatures, cloudy conditions and high rainfall, yields are high but protein content in the forages are down by 20 to 25% compared to long term averages. In many cases, cutting was delayed by 3 to 4 weeks because of poor weather. This has increased fibre levels and reduced energy content in the forage.
When taking forage samples, use a core sampling tool. It is necessary to take 15 to 20 core samples from bales collected off a field. A core sampling tool collects all the fine leaves and flowers from the bale providing a true indication of quality. A grab sample is not accurate. Some of the high quality leaves and stems are lost when grabbing a sample from a bale. A grab sample can be 2% lower in protein and 5 points lower in TDN when compared to a core sample. Have minerals and trace minerals analyzed by the wet chemistry method.
With varied conditions across the province, the only way to be certain of forage and grain quality is to send samples in for analysis. If help is needed interpreting the results and developing balanced rations, contact your feed company or a nutritionist.
Barry Yaremcio M. Sc. P. Ag.
Yaremcio Ag Consulting Ltd.