April 2013 - AFMA

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The impact of amino acid formulation on the dairy cow By TP Tylutki, PhD Dpl ACAN, AMTS LLC, USA What does a cow need to survive, reproduce, grow and produce milk? Typically the answers would be energy, protein, fat and minerals/vitamins. But let’s take a step back and look where these come from. Energy in the cow is going to come from fermentable carbohydrates, fatty acids, and the biggest one, volatile fatty acids (VFAs), from the rumen. The rumen takes all these fermentable products and the rumen microbes produce VFAs. These VFAs are used to produce glucose and fat (both body fat and milk fat). Protein is more difficult. Supply Everyone is used to the terms crude protein, soluble protein, degradable protein and non-degradable protein. None of these are correct though. The underlying problem is that animals do not use protein. Protein is a collective term for nitrogen-containing compounds. When feed is sent to the laboratory for analysis, they do not analyse for protein. Rather, they analyse for nitrogen. This methodology goes all the way back to the developer, Johan Kjeldahl, in 1883. There are a couple of newer methods commercially used that rely on combustion to determine how much nitrogen is in a sample, but the resulting compound (nitrogen) quantified is the same. It is then assumed that all proteins contain 16% nitrogen. This is not true either. A product such as maize protein may contain 16% nitrogen, milk 15,7% and wheat 17,5%. A great example of this is urea. Urea is 46% nitrogen. Using the standard 6,25 multiplier, this gives a crude protein of 287,5%. What should be measured, is either total amino acids or each amino acid AND ammonia nitrogen. Commercially this is not viable as it is cost-prohibitive. The cost per sample to do amino acids instead of crude protein, is between 15 and 20 times higher. Table 1: Amino acid composition of tissue, milk, microbes and several feeds (g/100g) Amino acid Tissue Milk Microbes Soya 48 Blood Alfalfa Maize gluten meal 60 MET 1,82 2,71 2,68 1,30 1,07 0,73 2,09 LYS 6,29 7,62 8,20 6,49 9,34 6,02 1,24 HIS 2,45 2,74 2,69 2,69 6,45 2,62 2,45 PHE 3,65 4,75 5,16 5,22 7,86 6,32 6,48 TRP 1,18 1,51 1,63 1,41 1,88 1,84 0,37 THR 3,83 3,72 5,59 4,83 4,73 5,00 2,93 LEU 6,96 9,18 7,51 8,66 13,40 9,26 16,22 ILE 2,94 5,79 5,88 3,99 0,88 6,01 4,34 VAL 4,28 5,89 6,16 4,39 9,08 7,14 5,04 ARG 6,65 3,40 6,96 7,74 5,01 6,39 3,17 Figure 1: Overview of amino acid flow in cattle 48 AFMA MATRIX ● APRIL 2013
Figure 2: Nitrogen intake and excretion from rations varying in crude protein levels from 13,5% to 19,4% dry matter starting to show much greater impact beyond these simple output measurements. Table 1 contains the amino acid content of milk, tissue, microbes and several feeds. Ignoring amino acids while formulating results in diets that are typically more expensive will result in higher levels of nitrogen excretion. As reported by Olmos et al. (2006), varying the crude protein content of diets in lactating cows had no effect on milk nitrogen output or milk protein (Figure 2). As illustrated, at each incremental increase in crude protein intake, all extra nitrogen was excreted as manure. Figure 3 splits manure into faecal and urinary nitrogen, where it is very clear that excess nitrogen is going to urine. Feed science Figure 3: Nitrogen excretion via faeces and urine from diets varying in crude protein content Ammonia will be used in the rumen to help meet the nitrogen requirements of the rumen microbes. The amino acids consumed will be degraded in the rumen (and used for ammonia and energy sources by the rumen microbes), or escape the rumen and be potentially available to the cow to absorb directly. As the cow consumes a meal, the total amino acids plus ammonia enter the rumen. Figure 1 illustrates the generic flow through the cow. Ammonia (either consumed or from the degradation of amino acids in the rumen) is either captured by rumen microbes, recycled to the rumen via saliva, or is excreted either via urine or milk (MUN). The rumen microbes supply a large mass of amino acids to the cow (anywhere from 40-80% of the total supply), with the rest coming from non-degradable as well as digestible amino acids. All the productive processes of the cow or heifer are driven by amino acid supply. Amino acids are used for milk protein and muscle (growth) as outputs. Equally important, though, are their uses in enzymes, energy for the fetus and immune function. Unfortunately, when most people talk about amino acid nutrition, they focus on the output side of milk protein only. Research is Getting it to the cow Given these results, how do we get amino acids to the cow? Dr Larry Chase at Cornell University has been collecting data on herds fed low crude protein diets. In this dataset (14 herds in the Northeast USA), milk production averaged 38,6/fed diets averaging 15,7% crude protein and MUNs averaging 9,5 mg/dl. Commonalities regarding diets were a high level of fermentable carbohydrates (28,2% starch, 4,5% sugar) and 55,7% roughage (with a range of 48 to 60,4%). In other words, these diets are formulated to maximise microbial yield. Going back to Table 1, if we compare the amino acid content of microbes to that of milk, we find that they are very similar. It is safe to say that rumen microbes are the perfect food for cows! Thus, the first step in amino acid nutrition is to maximise rumen microbial yield. That is accomplished by feeding high levels of fermentable carbohydrates, ensuring enough degradable nitrogen, and some free amino acids to feed the rumen microbes. Our current carbohydrate recommendations for maximising microbial protein (MP) output are shown in Table 2. The microbes require nitrogen as well. This is relatively simple to accomplish as microbes require ammonia and some true amino acids. A standard diet of maize silage, alfalfa hay (silage, green chop), ground maize, soy meal and minerals will typically supply ade- AFMA MATRIX ● APRIL 2013 49
Page 1: APRIL 2013 Volume 22 No 1 Matrix Qu
Page 4 and 5: Editor’s note A battling world ec
Page 6 and 7: News & views China doubles corn pur
Page 9: Benchmarking is a crucial aspect of
Page 13: Feed industry Feed outlook for 2013
Page 19 and 20: Processing The technical and practi
Page 21: a stress condition and compensate i
Page 25: Biofuel co-products as livestock fe
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Page 37: The way feed is presented will affe
Page 42 and 43: Lynn Phillips Consulting cc CK 88/2
Page 44 and 45: Figure 1: Fluorescence microscopy s
Page 47: Control of E. coli, Salmonella and
Page 52 and 53: Table 2: AMTS recommended carbohydr
Page 55 and 56: Feed science Sow nutrition: Avoidin
Page 57 and 58: ies showed that weight loss had a n
Page 59: of both the advisor and the farmer
Page 62 and 63: Special report: Top feed companies
Page 64 and 65: Table 2: Asian companies in the top

April 2013 - AFMA

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