Understanding the full potential of grass is fundamental to ensuring maximum utilization. For anyone wondering, “Does grass have nutritional value?”, this guide answers that question.
Capture the full power of grass
Grass can be used for grazing or silage as the basis for most roughage-based feeding systems. It is simply the cheapest source of feed for ruminants and perhaps the most important factor in the profitability of modern agriculture. However, kiwi cattle farmers must take full advantage of the grass by maintaining the quality and productivity of the pastures.
Farmers can manage intake through grazing and winter feeding plans. In addition, it is important to understand the nutritional qualities of the grass. In short, if you don't know the full nutritional value of grass, there is a chance it will be underutilized or supplemented inaccurately.
In this lawn guide, Germinal will outline key definitions and highlight the importance of different components, while providing advice on how to achieve the best results. Farmers also often grow grass with itwhite cloverInred cloverThat is why we will also discuss these legumes.
drug matter
Dry matter (DM) in feed is the proportion of total components, including fiber, protein, water-soluble carbohydrates, lipids and ash, that remains after water has been removed. In short, the lower the dry matter content, the higher the fresh weight of the feed required to achieve targeted nutrient absorption, whether grazing grass or canned feed.
Dry matter can also be used as a term to measure yield. Yield, recorded as kgDM/ha, is used as a measure of grass carrying capacity (stocking rate) and is a crucial element in effective grazing management. It can also be used to measure the yield of silage crops.
In terms of dry matter content, field and weather conditions cause significant variations, and there are inherent differences between tetraploid and diploid varieties. All other factors being equal, diploids have higher DM content (typically 18-26%) than tetraploids (15-20%), as diploids have smaller cells and a lower cell wall to cell volume ratio. When ruminants are fed exclusively on a tetraploid pasture, they must consume as much as a third more fresh grass per day to achieve the same nutritional intake as a 100% diploid pasture.
When analyzing the dry matter yield, modern ryegrasses are bred for maximum production.
When grazing, the idea is to provide roughage that offers the ideal balance between fresh, nutrient-rich growth and the right fiber content for efficient rumen passage. Ultimately, this balance can be achieved by using a grazing rotation of 18-25 days during the high season.
However, poor grass management will increase the proportion of dying plant material, leading to a significant reduction in forage quality and absorption potential. In silage production, the aim is a chop content of 16-20% DM and an ensiling percentage of 30-35% (for clamp silage) and 35-40% (bale). This allows proper fermentation and optimal absorption, while minimizing the risk of aerobic instability.
D-value and ME of grass
The D value is a measure of digestibility, or the level of feed that can be digested by a ruminant. Regarding the nutritional value of grass, this digestible part of the feed consists of crude protein, carbohydrates and fats.
ME is the amount of energy an animal can get from the food. It is measured in megajoules of energy per kg of feed dry matter (MJ/kg DM). ME is directly correlated with the D value because any feed must be digestible before the energy is available.
Essentially, one percentage point of the D value corresponds to 0.16 MJ/kg DM ME. Part of ME is available as an energy source for rumen microbes. This is called fermentable ME (FME) and consists largely of plant cell walls. The D value in grass will be highest when the grass has fresh leaf growth, but will decrease as the plants mature.
The decrease in the D value will be greatest after the ear (head) emerges. Typically, grass clippings for silage will lose 2 percentage points of D-value between mowing and feeding. The higher the D value and ME in the feed, the better the performance of ruminants.
In Britain, the National Institute of Agricultural Botany estimates that a one point increase in D value (or 0.16 MJ/kg ME) is equivalent to 0.26 liters of milk per day. dairy cow per /day with extra lamb in live weight. Similar work from Teagasc in Ireland and DARDNI estimate that the increase in milk yield is higher, 0.33 and 0.4 liters per cow respectively. cow per day.
Water soluble carbohydrates
In grass, water-soluble carbohydrates (WSCs) are the soluble sugars that are quickly released from the grass into the rumen. WSCs provide a readily available energy source for the rumen microbes responsible for digesting feed. These sugars can also stimulate silage fermentation.
The higher the sugar content, the better the silage is preserved and the higher the nutritional value of the animal will be. A higher WSC is the differentiating factor in modern ryegrass which has been bred at IBERS Aberystwyth University for 30 years. Grass seed varieties with a higher WSC value than conventional varieties are now available in New Zealand as Aber High Sugar Grass.
Relative differences in WSC persist between ryegrass cultivars, although levels may rise and fall over a season due to varying weather conditions.
For example, on a hot summer day the WSC content can reach 35% DM. Meanwhile, on a cool, cloudy fall day it can be as much as 10% DM. Differences between races persist at both ends of the spectrum.
In general, a high WSC will mean that the feed composition is closer to the 2:1 WSC/crude protein ratio, which animal models indicate is the target for optimal nitrogen use in the rumen.
Ultimately, this means that more of the feed is converted into milk and meat, and less is wasted on urine (and methane). Under ideal growing conditionsGerminals Aber HSG raaigraswill achieve the optimal ratio of 2:1 for WSC protein. Wetter silage ultimately uses more sugar to achieve stable fermentation and leaves less for the animal.
Points to WSC
- Pick and sow 100% Aber HSG and silage mixes to maximize WSC
- Cut silage in the late afternoon to maximize WSC content
- Avoid making silage that is too wet (less than 28% DM) as this can lead to sugar loss in the effluent and an increase in effluent; Also, wet silage has a greater need for sugars to create good fermentation and stable silage
- WSC peaks 3-5 weeks after grazing or mowing
- Manage the grass to prevent diseases that reduce WSC (e.g. crown rust or leaf spot)
The clover effect
- White clover generally contains less WSC and more protein, so it is important to maintain the 30% white clover target throughout a grazing season for optimal performance.
- Red clover generally contains less WSC than ryegrass, so growing it in combination with Aber HSG varieties is beneficial to the silage fermentation process
- When ensiling red clover and ryegrass, aim for a dry matter content of at least 30% to increase the concentration of WSC in the feed
Is there protein in grass?
Yes, grass contains protein and this is generally reported as total crude protein (CP), which is 6.25 times the nitrogen content. About 80% of the CP in fresh grass consists of real proteins. The remaining fraction is often referred to as non-protein nitrogen.
Any type of nitrogen can be used by an animal, but true proteins are used more efficiently for meat and milk production. A greater portion of the non-protein nitrogen is used inefficiently and then excreted.
CP can be divided into efficiently rumen degradable protein (ERDP) and digestible non-degradable protein (DUP). ERDP is the largest fraction of fresh feed protein and can be broken down by rumen microbes and converted into microbial protein for later digestion. DUP passes through the rumen intact and is later broken down and digested in the small intestine.
CP content varies per cultivar and between cultivars and is influenced by management factors such as crop maturity and nitrogen fertilization.
Real protein
The proportion of CP available as true protein is lowest in the period after nitrogen fertilization has been applied, but increases as the grass grows and converts non-protein nitrogen into true protein.
The proportion of crude protein in the silage that is available as real protein is influenced by fermentation. Better fermentation ensures that more CP remains as real protein.
Fibers in grass
Fiber is measured as NDF (neutral detergent fiber). This is the insoluble fiber fraction (cellulose, hemicellulose, pectin and lignin) that remains after cooking in a neutral detergent. Carbohydrates in NDF are not as readily available as those in the WSC component of ryegrass. However, NDF is important for predicting voluntary intake by ruminants.
The proportion of NDF potentially digestible by ruminants is termed dNDF, which is a secondary source of slow-release carbohydrates that provides a useful source of fermentable energy for ruminants in the colon and rumen.
The grass fiber concentration varies greatly during the growing season. It is at its peak when the grass produces reproductive seed heads, as opposed to vegetative leaves. Conversely, fiber content is often lowest in early spring when fresh growth peaks.
The primary purpose of fiber is to maximize voluntary animal intake while ensuring adequate rumen digestion. For grazing, the optimal NDF content of grass should be in the range of 30-40% of total dry matter, with dNDF being 20-30% of dry matter, or approximately 60-75% of total fiber content in a digestible form.
If grass fiber content falls below these optimal levels, additional fiber feeding may be necessary to prevent the grass from passing through the rumen too quickly. When making silage it is important to mow before the grass is too mature (pre-silage) to avoid a significant decrease in digestibility.
Indicates NDF and dNDF
- Rotational grazing (18-25 days) using the Three Leaf system to determine when to graze will optimize NDF and dNDF levels
- Topping removes stem growth and encourages new growth and prevents NDF from becoming too high, but good grazing should avoid the need for topping
- Mow the silage in front of the grass heads to prevent NDF from building up too high
- Manage grazing and mowing of pastures to prevent diseases that will increase NDF at the expense of overall quality
The clover effect
- The fiber concentration of red clover and white clover is lower than that of ryegrass and has the potential to increase voluntary intake
- The physical form of fibers in clover generally breaks down more quickly in the rumen than fibers in ryegrass
Lipids in grass
Lipids in forage grass contain a high level of polyunsaturated fatty acids (PUFA). And it is the good fatty acids, also known as Omega 3 and Omega 9, that have positive health effects for humans.
From an animal production perspective, increased supply of PUFA has been shown to improve animal fertility and result in positive effects on meat quality with longer shelf life and more desirable color.
Furthermore, there is evidence of reduced methane emissions from ruminants eating a high PUFA diet, an effect that is positive for the environment. Early data suggest that the total fatty acid content of grass ranges from approximately 2.5 to 5% of dry matter, with the PUFA component accounting for 65 to 78% of the total fat content.
Lipids can contain approximately twice as much energy as carbohydrates and are an important source of energy for livestock. Germ breeding programs at IBERS Aberystwyth University have identified lipid concentration and fatty acid profile as important targets for the future.
The clover effect
- The lipid content of white clover is generally slightly lower than that of ryegrass (ranging from 2-4.4% of dry matter)
- Red clover generally contains more polyunsaturated fat than ryegrass
be sure thatview our Knowledge Hubif you would like to read more about the effectiveness of sowing grass and clover.
