Contact/s:
Silvija Dreijere
silvija.dreijere@llkc.lv
Dairy Cow Feed Rations and Ammonia Emissions
Latvia
Temperate, Humid Continental
- Reducing nitrogen losses
- Balancing feed rations
- Ammonia emissions
Thematic Areas
Production System/s
Summary for Practicioners on the Main Finding(s)/Innovative solution(s)
On farms, reducing nitrogen losses in livestock not only helps to preserve the environment, but also improves the farm’s bottom line.
Ruminant livestock are not very efficient at using the nitrogen they take up in feed. If rations are very precisely calculated, 30 to 35 percent of the nitrogen in feed proteins and non-protein compounds becomes a component of milk. The rest of the nitrogen is excreted from the body mainly in urine and faeces. About 60 to 80 per cent of urinary nitrogen is in the form of urea.
Urea concentration in urine is an important indicator of ammonia emissions in dairy farming. It is possible to adjust both the urine output, the urinary urea concentration and the total manure output with the feed ration. It must be clearly understood that urine and faeces separately emit very minimal quantities of ammonia, but only after they reach the floor surfaces in the housing and these two fractions of excreta physically mix, ammonia is released.
There are additional factors that influence the evaporation of ammonia in cow housing. These include temperature, air velocity, pH, size of floor surfaces, moisture content of manure and storage time. For example, high pH and temperature contribute to increased ammonia emissions. Dairy cow manure typically has a pH between 7.0 and 8.5, which allows ammonia to be released into the atmosphere quite quickly.
The deposition of atmospheric ammonia and chemical compounds resulting from atmospheric chemical reactions with ammonia (i.e. ammonium aerosol) is thought to contribute to water and soil acidification and eutrophication.
Thus, one solution is to balance feed rations as closely as possible to the amino acid needs of the cow: the amount of crude protein in the diets of high-yielding cows can be safely reduced, allowing farms to maintain high milk yields (above 35 kg per cow per day) while improving nitrogen use efficiency.
Summary for Practicioners in Native Language
Saimniecībās, samazinot slāpekļa zudumus ganāmpulkā, palīdzam ne tikai vides saglabāšanai, bet arī uzlabojam saimniecības peļņas rādītājus.
Atgremotāji ne īpaši efektīvi izmanto ar barību uzņemto slāpekli. Ja barības devas ir ļoti precīzi sarēķinātas, tad 30 līdz 35 procenti no slāpekļa, kas ir barības olbaltumvielu sastāvā un neproteīna savienojumos, kļūst par piena sastāvdaļu. Pārējais slāpeklis no organisma tiek izvadīts pamatā ar urīnu un fēcēm. Apmēram 60 līdz 80 procenti no urīna slāpekļa ir urīnvielas formā.
Urīnvielas koncentrācija urīnā ir būtisks indikatorrādītājs amonjaka emisijām piena lopkopībā. Ar barības devām ir iespējams koriģēt gan urīna daudzumu, gan urīnvielas koncentrāciju urīnā, gan kopējo mēslu daudzumu. Ir pilnīgi skaidri jāsaprot, ka urīns un fēces atsevišķi emitē ļoti minimālus amonjaka daudzumus, bet tikai pēc nonākšanas uz grīdu virsmām novietnēs un abām šīm izdalījumu frakcijām fiziski sajaucoties notiek amonjaka izdalīšanās.
Ir arī papildu faktori, kas ietekmē amonjaka iztvaikošanu govju novietnēs. Tie ir temperatūra, gaisa plūsmas ātrums, pH, grīdas virsmu laukumu lielums, kūtsmēslu mitruma saturs un uzglabāšanas laiks. Piemēram, augsts pH un temperatūra veicina paaugstinātu amonjaka emisiju. Slaucamo govju kūtsmēslu pH parasti svārstās no 7,0 līdz 8,5, kas ļauj amonjakam diezgan ātri izdalīties atmosfērā.
Tiek uzskatīts, ka atmosfēras amonjaka un ķīmisko savienojumu nogulsnēšanās, kas rodas atmosfēras ķīmiskās reakcijās ar amonjaku (t.i., amonija aerosolu), veicina ūdens un augsnes paskābināšanos un eitrofikāciju. 1. attēlā parādīts slāpekļa cikls un ietekme gan uz ūdens, gan gaisa kvalitāti.
Additional Information
On farms, reducing nitrogen losses in livestock not only helps to preserve the environment but also improves the farm’s bottom line.
Ruminant livestock are not very efficient at using the nitrogen they take up in feed. If rations are very precisely calculated, 30 to 35 percent of the nitrogen in feed proteins and non-protein compounds becomes a component of milk. The rest of the nitrogen is excreted from the body, mainly in urine and faeces. About 60 to 80 percent of urinary nitrogen is in the form of urea.
Urea concentration in urine is an important indicator of ammonia emissions in dairy farming. It is possible to adjust both urine output, urinary urea concentration, and total manure output with the feed ration. It must be clearly understood that urine and faeces separately emit very minimal quantities of ammonia, but only after they reach the floor surfaces in housing and these two fractions of excreta physically mix is ammonia released.
There are additional factors that influence the evaporation of ammonia in cow housing. These include temperature, air velocity, pH, size of floor surfaces, moisture content of manure, and storage time. For example, high pH and temperature contribute to increased ammonia emissions.
Dairy cow manure typically has a pH between 7.0 and 8.5, which allows ammonia to be released into the atmosphere quite quickly.
The deposition of atmospheric ammonia and chemical compounds resulting from atmospheric chemical reactions with ammonia (i.e. ammonium aerosol) is thought to contribute to water and soil acidification and eutrophication. Figure 1 shows the nitrogen cycle and its impact on both water and air quality.
There are two ways to reduce nitrogen losses from cows. First, the microorganisms living in the rumen must effectively “consume” the protein and nitrogen present. The second is to balance feed rations as closely as possible to the amino acid needs of the cow so that the total amount of protein is reduced, and the amount of excess nitrogen is correspondingly lowered.
Feeding high-protein diets is not only harmful to the environment but also to the animals. Making the most of nitrogen in the animal is also a way to reduce the cost of milk production. If the liver is overloaded with ammonia, blood urea levels will increase, as will the amount of milk urea (MUN). This can have adverse effects on cow health and reproduction. Excessive ammonia build-up in the cow results from overfeeding, when too much nitrogen and/or protein reaches the micro-organisms in the rumen.
Additional energy is required to remove the excess nitrogen from the body, which can lead to a reduction in milk yield and other performance parameters. Excess ammonia is converted to urea in the kidneys and liver.
Urea is a small organic compound formed from carbon, nitrogen, oxygen, and hydrogen. It is primarily eliminated from the body in the urine, but as blood urea levels rise, so does the amount of urea in milk.
This is why the amount of urea in milk is measured—to assess how much of the protein (nitrogen) intake is being lost due to inefficient utilization.
By balancing rations according to amino acid requirements, the amount of crude protein in the diets of high-yielding cows can be safely reduced from17.5% to 16.6%, allowing farms to maintain high milk yields (above 35 kg per cow per day) while improving nitrogen use efficiency.
There is a second benefit: the amount of nitrogen in the manure is reduced, which means fewer hectares are needed for manure spreading to stay within nitrogen limits per hectare.
A very important factor in successfully reducing crude protein in the ration is accurate on-farm feeding and knowing the chemical composition of the forage very precisely—or conducting forage analyses on the farm