BEC Feed Solutions Written by:Steve Blake – BEC Feed Solutions Modified and Presented by: Ken Bruerton – Protea Park Nutrition The role of Phosphorus in

BEC Feed Solutions

Written by: Steve Blake – BEC Feed SolutionsModified and Presented by: Ken Bruerton – Protea Park

Nutrition

The role of Phosphorus in Cattle Nutrition

Phosphorus is an essential element to life

The chemical symbol for Phosphorus is:

P

The Role of Phosphorus in Cattle Growth and Reproduction


Nutritional Role of Phosphorus

Phosphorus (P) is present in all cells in the body

Essential for many digestive and metabolic processes, including conversion of feed into energy, building and repair of body tissues and cell division.

Essential component of the bones – hydroxy apatite (dicalcium phosphoshate)

75-85% of P is in the skeleton

P transported in the blood stream.

Ca & P constantly being drawn from the bone reserves and replaced.

P deficiency results in osteomalacia (Peg Leg)

Nutritional Role of Phosphorus

P moves from the blood to the salivary glands. Saliva contributes more P to the rumen than the feed eaten.

Rumen micro organisms have a requirement for P distinct from the requirements of the animals tissues.

The requirement of the rumen micro-organisms is generally supplied by the endogenous secretion into saliva.



Decreased P in the diet results in decreased feed intake, without an effect on Dry Matter (DM) digestibility.

Decreased feed intake results in:-

Decreased growth rate Decreased milk yield Decreased reproduction rate Decreased calf growth rate

P absorbed mainly in the small intestine

P absorption depends on:-

P content of the diet Ca: P ratio P bioavailability

Phosphorus Loss Faecal, 400kg animal looses 6 – 8g per day.

Faecal P consists of some dietary P (feed) and some endogenous P (saliva)

Milk – 1 litre milk contains 0.95g of P

P deficiency leads to decreased milk volume, not decreased P content.


Phosphorus / Energy / Protein

Nitrogen (N), P and Energy levels in pastures generally move in parallel.

P intakes lowest prior to spring storms. When protein and energy are also at their lowest.

There is a misconception that P deficiency is most acute at this time.

P deficiency is most acute in the growing season when plant P levels are at their highest. During this

time protein and energy levels are also at their highest.

Supplementation with P, N, or Energy will only be positive, if that nutrient is the first limiting nutrient.


Phosphorus / Energy / Protein

During the growing season on legume based pastures, P can be the first limiting nutrient even

though P levels are at their highest.

N will be the first limiting nutrient on native pastures as early as mid to late summer.

When faecal N drops below 1.3%, growth stops. However, supplementation should be started before this. Also, never feed P when faecal N is below 1.3%.

Necessary to address any N and/or Energy deficits before additional P supplementation is

beneficial.

P supplementation (on its own) during the dry season leads to decreased growth rate. This is most likely because energy is expended to metabolize the P.


Energy

Protein

Phosphorus

Wet Dry

Phosphorus Requirements

Maintenance requirement for P increases with the size of the animal. It is not directly proportionately to the body weight but rather to the Weight0.75

Increased growth leads to increased demand for P 3.3g P / 250g/d Lwg

Lactation 0.95g P / lt milk @ 80% absorption = 1.2g dietary P / lt. @ 5lt/day = 6g/day.

With lower digestibility sources more dietary P is required. P requirement increases during pregnancy to support growth of foetus and

placenta. 30kg calf = 210g P Placenta = 10 g P

90% of this 210g is needed during the last 90 days of pregnancy. 1.5g/day until month 7 4g/day in month 9



Recommendations

Feed N to breeders in early autumn on native pastures Be early rather than late with supplementation. Ease them into supplementation with lower levels of NPN.

Feed N to heifers and steers from late autumn on native pastures

No P supplementation for growing stock if they are loosing weight unless protein is supplied as well and standing dry feed is available.

Lactating breeders feed P in late dry season at half wet season rate to match reduced energy and protein intake

Case Study 2009 season Helen Springs


Nutrient Intake and Growth

Simply put: if the pasture available has enough nutrients the cattle will grow, produce milk, reproduce.

They need: Energy – drives all metabolic processes. If energy is

deficient cattle lose weight. Cows will not cycle. Proteins – needed to provide amino acids to make

immune proteins (antibodies), enzymes, muscle proteins (growth)

Minerals – bones (Ca & P), electrolyte balance (Na, K, Mg, Cl, SO4,PO4), trace minerals (Fe, Zn, Mn, Cu, Se, Co, I) for blood, enzyme cofactors, hormones.

Vitamins – generally produced by rumen micro-organisms. These act as antioxidants and cofactors in enzymes.

Nutrient Intake and Growth

If the pasture is deficient in just one nutrient growth will be limited by the supply of that nutrient. If protein is deficient relative to energy DM intake will

also be suppressed. Therefore protein is a key nutrient.

If there is enough energy and protein but P is deficient growth will be limited.

Mores subtle deficiencies such as trace minerals may also limit reproduction eg Zn and Se.

Concept of a nutrient gap: The forage my have energy in it but is deficient in

protein Common occurrence in northern Australia in dry Season

The forage may have enough energy and protein but is deficient in P

Common occurrence in northern Australia in Wet Season

Pasture analysis from NT property

Supplements for Northern Australia

Sample 1 Mitchell Grass

Sample 2 Mitchell Grass

Average

Growth Stage Mature Mature Mature Dry matter (DM) % 90.2 91.1 90.65 Moisture % 9.8 8.9 9.35 Crude Protein (CP) % 2.3 2.2 2.25 Ash % 10.7 8.9 Fat % 2.0 1.8 Acid Det. Fibre (ADF) % 44.8 46.3 Neutral Det. Fibre (NDF) % 71.9 72.5 Digestible DM % 43.7 43.7 Metabolisable Energy (ME) mj/kg 6.6 6.4 6.5 Dry Matter intake % 1.7 1.7 1.7

DM protein levels at about 2.5% are already at a level where supplementation will be beneficial to intake. They are also at a level where DM intake is suppressed.

From the feed analysis, predicted pasture DM intake potential is 1.7% of body weight (4.25 kg for a 250 kg animal). As fed this = 4.7 kg

Maintenance energy and protein requirements for a beef animals are available from NRC tables.

We know from analysis what the pasture can supply.

We have energy locked up in the pasture but the protein is limiting the intake and therefore weight gain

We can then attempt to bridge the nutrient gap with a lick supplement.



ME Dig. Protein Kg Intake Dig Prot IntakeProtein Deficitmj/kg g/kg g/h/d g/h/d

6.5 9.9 5.3 52.2 147.8

Pasture Provides Maintenance Intake

Body Wt ADG ME Req Dig Proteinkg kg/h/d mj/h/d g/h/d250 0 34.3 200

Maintenance Requirements

Nutrient Intakes required to maintain weight

These animals will lose weight on the pasture available.

Protein Deficit = 147.8 g Supplement Crude Protein = 903 g/kg Supplement ME = 1.1 mj/kg Supplement intake required to bridge protein

deficit = 147.8/0.903 = 164 g/head/day If lick intake is 200 g/head/day protein intake is

180.6 g and the ME intake is 0.22 mj This means the animal’s protein intake should

allow it to consume more dry matter and therefore exploit more of the energy locked up in the standing dry feed.


Consider that there is now enough protein intake to allow an extra 2 kg/h/d of pasture intake.

That gives the animal another 18.9 g of digestible protein and 13 mj of ME

Total protein available for gain = 19.8 + 32.8 = 52.6g

Total ME available for growth 13 + 0.22 = 13.22 mj

Extra growth possible (from NRC) 200 g/h/d The P level in the lick is adequate to support

this weight gain The extra protein in the lick allows the animal

to exploit the standing dry feed and continue to grow.


What About the Breeder? Pasture: 6.5 mj/kg ME; 9.9 g/kg dig. Protein 400 kg cow ME maintenance: 49.4 mj (7.6 kg pasture) Digestible Protein: 290 g/d (can get 75.2 from

7.6 kg pasture) Protein Deficit: 214.8 g/d – Must come from lick

or from breakdown of muscle. Cow will try to milk by metabolising muscle and bone (for the Ca and P)

New lick:


Plant: 1 BEC FORMULATIONS Product: XXX BREEDER LICK Version: 1 Ingr Code Ingredient Name Kgs Pct -------- -------------------------------- --------- ------ 100 UREA 150.000 30.000 81 COTTON 43% Nar 100.000 20.000 130 AMMONIUM SULPH 100.000 20.000 128 KYNOFOS 70.000 14.000 155 SALT 50.000 10.000 125 LIMESTONE 38% 20.000 4.000 CNP7001 CAUSEWAY TRACE MINS 10.000 2.000 Formula Totals: 500.00 Totals at 100.00 Pct DM: 489.02 ---------------------------------------------------------- Nutrient Composition at 100.00 % DM: (Class 6) Nutr Nutrient Name Amount Units ---- -------------------- ------------ -------- 11 RUMINANT M.E. 2.353 MJ/KG 19 MOISTURE 0.000 PCT 20 CRUDE PROTEIN 123.27 PCT 33 NPN PROTEIN EQ. 114.42 PCT 38 R.D.P. 926.64 G/KG 39 U.D.P. 29.855 G/KG 60 CRUDE FAT 0.525 PCT 67 DRY MATTER 100.00 PCT 88 Total N 19.724 100 ASH 46.746 PCT 101 CALCIUM 3.744 PCT 103 TOTAL PHOS 3.214 PCT 105 SODIUM 3.996 PCT 106 CHLORIDE 6.249 PCT 107 POTASSIUM 0.276 PCT 108 SULPHUR 5.172 PCT

Protein Deficit for maintenance = 214.2 g Requires (214.2/1232.7) = 174g of lick

per day Need to produce milk: Milk requirement per litre:

Pasture required per litre to provide energy = 0.75 kg

This also provides 7.45 g of digestible protein


Fat% ME Dig Prot Pmj/d g/d g/d

3.5 4.87 42 1.2

To produce 3 l of milk the extra dry matter intake required would be 3 * 0.75 = 2.25kg

Protein from 2.25 kg of pasture = 22.3 g Protein required from lick to support 3 l/day

milk output is 126 – 22.3 = 103.7g Required extra lick intake = 103.7 /1233.7=

84.1g

Total lick intake required to support the extra dry matter intake to produce 3 l of milk is about 258 g

P intake from that is 8.3g – sufficient, considering there is some P in the pasture (0.5 g/kg)


Summary

Keep the better pastures for breeders To keep breeders milking on pastures

that have hayed off will require a lick intake of at least 250g/h/d

This will slow the rate of weight loss in the cows

Start supplementing breeders while there is still green in the pasture.


Documents

BEC Feed Solutions Written by:Steve Blake – BEC Feed Solutions Modified and Presented by: Ken Bruerton – Protea Park Nutrition The role of Phosphorus in