The four stomachs of a dairy cow

Transcription

1 The four stomachs of a dairy cow Left side view 1) Rumen 2) Reticulum 3) Omasum 4) Abomasum Reticulo-omasal orifice (reticulo-rumen exit) (on the right side of the cow) (on the right side of the cow) Esophagus Dorsal sac Cranial sac Ventral sac

2 The digestive tract Right side view Large Intestine Colon Rectum Cecum Small Intestine Duodenum Jejunum Ileum Rumen Reticulum Omasum Abomasum

3 Functions of the digestive tract: mouth Rumination reduces particle size and exposes fibrous carbohydrates for bacterial fermentation. Production of as many as 180 liters of saliva per day when the cow chews 6 to 8 hours per day. Saliva is rich in buffers (sodium bicarbonate and phosphates) that neutralize the acids produced by rumen fermentation. Buffers maintain neutral ph that favors bacterial growth in the rumen.

4 Functions of the digestive tract: reticulo-rumen Retention of long forage particles that need to be ruminated. Long particles in the fibrous mat stimulate rumination. The carbohydrates and proteins in the feeds are fermented by microbes. Production of volatile fatty acids (VFA) as end products of microbial fermentation. Fermentation allows for the growth of microbes which are rich in high quality protein. Gases Long Particles in a Fibrous Mat Small Particles in a Liquid Pool Absorption of VFA, which are the primary sources of energy for the cow. Gases (carbon dioxide and methane) produced by fermentation are eructated (500 to 1000 liters/day).

5 Functions of the digestive tract: omasum Absorption of water, volatile fatty acids and minerals. Large particles are trapped in the leaves attached to the wall (and thus contribute to the selective retention of large particles in the rumen).

6 Functions of the digestive tract: abomasum Secretion of hydrochloric acid and digestive enzymes. Digestion of carbohydrates and proteins that escaped rumen fermentation. Digestion of microbial protein produced in the rumen (1 to 2.5 kg per day).

7 Functions of the digestive tract: small Intestine Secretes digestive enzymes, and receives digestive secretions from pancreas and liver. Site of enzymatic digestion of proteins, carbohydrates and lipids. Site of absorption of water, minerals, amino acids, glucose and fatty acids.

8 Functions of the digestive tract: cecum and large intestine Cecum Fermentation of unabsorbed products of digestion by a bacterial population Large Intestine Absorption of water Formation of feces

9 Components and chemical composition of feed Feed Water Dry Matter Organic matter (C,H,O,N) Nitrogenous compounds Lipids Carbohydrates Phenolic compounds Vitamins Non protein Protein Simple Compound Non cell wall Cell wall Fat soluble Water soluble Urea, amines, etc. Free amino acids Non-essential amino acids Essential amino acids Fatty acids, Sterol Triglycerides Phospholipids Waxes Sugars Starches Pectins Hemicellulose Cellulose Lignin, tannins, etc. Provitamin A, Vit. D2,D3, E, K Vit. of B complex Vitamin C Inorganic matter (Minerals) Essential Macro Micro Possibly essential Ca, Cl, Mg, P, K, Na, S Cr, Co, Cu, F, I, Fe, Mn, Mo, Se, Ba, Br, Ni, Sr, Sn, V

10 Forage versus concentrates 1) Bulk (volume) Density 2) Particle size 3) Energy content 4) Fiber content 5) Protein content 6) Mineral content Calcium, Potassium, Phosphorus, Micro. 7) Vitamins 8) Speed of fermentation 9) Palatability 10) Extent of digestion Forage High Low Long Low (0.8 to 1.5 Mcal NEl) High Legumes % Grasses 8-18% Crop residues < 4% Higher Low Higher Slow Low/High < 45 to 65% Concentrate Low High Short Low/High (0.8 to 2.2 Mcal NEl) Low Variable (<10% >90%) Lower Low Lower Rapid Higher > 80%

11 Density of forages and concentrates Forages: Large volume per unit of weight Concentrates: Small volume per unit of weight

12 Starch granule structure Potato Corn Grain Oats Wheat

13 Effects of maturity on forage quality early Neutral Detergent Fiber, %DM Crude Protein, %DM late early mid pre vegetative bloom heading Alfalfa (Legume) full early mid Energy Mcal NEl/kg DM full post Timothy (grass) milk stage As green plants mature quality decreases because of: a decrease in energy content an increase in fiber content a decrease in protein content

14 Yield of green forages: quantity or quality Yield of dry matter (tons/hectare) Indigestible dry matter Maximum yield of total dry matter Maximum yield of digestible dry matter Digestible dry matter Vegetative growth Late boot (grasses) First flower (legumes) Advancing stage of maturity Seed formation

15 Corn growth and maturity Constituents of plant dry 100 matter, % Age, days Dry matter, % 20 Fully dented Late dent Dough to early dent Late milk to dough Milk stage Grain Cob & Silk Husk & Ear Shank Leaf Sheaths Leaves Dented Dented Dough Dough Milk Milk Black layer Milk line Mature Immature

16 Protein metabolism in dairy cows Ration Rumen Intestine Crude protein (N x 6,25) Protein that escapes Protein breakdown by bacteria Ammonia Amino acids Non-protein Nitrogen Recycled in saliva Urea Liver Overflow ammonia Bacteria Bacterial protein Absorbed into the blood Fecal Nitrogen Excreted in Urine = Fermentable energy

17 Energy metabolism in dairy cows Ration Fibrous carbohydrates (NDF) Cellulose Hemicellulose Starch Simple sugars Non-fibrous carbohydrates (NSC) Absorbed in the blood Rumen (Carbohydrates that escape microbial fermentation) Glucose Gases Volatile fatty acids Energy Bacteria Ammonia Bacterial protein (Starch) Intestine (Glucose) Amino acids Absorbed in the blood Feces Energy (Maintenance, pregnancy, lactation, etc.) Acetic acid Butyric acid Propionic acid Triglycerides (Fats) Glucose Lactose (milk sugar) % Fat in milk Amount of milk produced

18 Acidity and ph scale Acid Neutral Alkaline Acids produced in the abomasum Acids produced in the rumen Optimum ph for ruminal fermentation Saliva Bicarbonate

19 Effects of forage to concentrate ratio of the diet Total volatile fatty acids (VFA) produced in the rumen (moles/day) 60 % Proportion of VFAs 50 Propionic Acid Acetic Acid 20 Butyric Acid Rumen ph Milk production (kg/day) Fat in the milk (%) Concentrates Forages % ration dry matter 20 % ration dry matter

20 Concentrate feeding and rumen acidosis ph of rumen content As a supplement offered twice a day separately from forages Low amount of concentrates fed: As a total mixed ration available all the time, well mixed with forages. Good appetite Good cellulose digestion Good microbial growth 6.0 Poor appetite 5.5 Rumen acidosis Little cellulose digestion Poor microbial growth Hours Concentrate feeding

21 Concentrate feeding and rumen acidosis (cont.) (cont.) ph of rumen content Large amount of concentrates fed As a supplement offered twice a day separately from forages As a total mixed ration available all the time, well mixed with forages. Good appetite Good cellulose digestion Good microbial growth 6.0 Poor appetite 5.5 Rumen acidosis Little cellulose digestion Poor microbial growth Hours Concentrate feeding

22 Importance of balancing a ration Excess nutrients Death Symptoms of toxicity No clear symptoms but partial loss of production Balanced ration Maximum production: The cow produces to her full genetic potential Insufficient nutrients No clear symptoms but partial loss of production Symptoms of deficiency Complete loss of production Clinical sickness Death

23 Balancing a dairy ration Pregnancy Milk Maintenance Growth Water Energy-Fiber Protein Macro-minerals Vitamins & Micro-minerals Cow s appetite Nutrients needed by the cow = Amount of feed dry matter Water Water Water Water Drinking water (and feed moisture) Forage(s) Concentrate(s) Mineral supplements Vitamin supplements Nutrients supplied by the ration

24 Estimation of of body weight by measurement of of hearth girth circumference Hearth girth (cm) (inches) Body weight Holstein cows (kg) Position of the tape to measure hearth girth

25 Dry matter intake of dairy cows Body Weight, kg Dry matter intake (kg/day) At maintenance (open, non-lactating) Dry and pregnant (dry period) In mid- and late lactation* Milk yield (kg/day) * In early lactation, dry matter intake may be reduced by as much as 18%.

26 Milk yield and energy density required in the diet Energy requirement Mcal NEl/day Dry matter intake, kg/day Energy density of the ration, Mcal NEl/kg dry matter Dry and Pregnant Cows Milk yield, kg/day

27 Forage to concentrate ratio Percent of ration dry matter Forage 40% Concentrate 60% Total 100% Dry matter of feed intake If a cow eats 20 kg of dry matter (DM): Forage DM ingested: 20 kg x 0.60 = 12 kg DM Concentrate DM ingested: 20 kg x 0.40 = 8 kg DM Kg of fresh feed ingested If forage is 30% DM and concentrate is 80% DM: Kg of fresh forage to offer: 12 kg / 0.30 = 40 kg Kg of fresh concentrate to offer: 8 kg / 0.80 = 10 kg

28 Fiber and energy in the diet Too much forage limits the intake of energy and milk production in lactating cows. High in fiber Too much concentrate results in milk fat depression, rumen acidosis and other health problems. High in energy Low in energy Low in fiber Forage, % Concentrates,%

29 Forage to concentrate ratio and volume of the diet? (F : C) 30:70 (F : C) 50:50 Increasing volume (F : C) 80:20

30 Intake regulation Dry matter intake (kg/day) Maximum forage in the diet that permits full expression of the genetic potential for milk production Physical regulation: Intake is controlled by the physical fill capacity of the rumen Energy regulation: Intake is controlled by energy requirements Percentage of forage in the diet

31 Effect of milk production on dry matter intake Dry matter intake (kg/day) Rumen fill limitation Milk production 35 kg per day 25 kg per day 15 kg per day Forage in the ration, (% of ration dry matter) 0 Dry and pregnant cows

32 Effect of forage quality on dry matter intake Milk yield 25 kg/day Dry matter intake (kg/day) Forage quality 21 Excellent (40% NDF*) Medium (55% NDF) 12 Poor (85% NDF) 9 * NDF = Neutral Detergent Fiber Forage in the ration (% of ration dry matter) 6

33 Effect of concentrate feeding on lactation yield Lactation yield (kg) kg of additional milk per kg of concentrate fed 4500 Concentrates and minerals, % Forage, % Average amount of concentrates offered during the lactation (kg/day)

34 Phases of of a lactation cycle Lactation phase Early lactation Mid- late lactation Dry period Energy balance Negative Null Positive Null or positive Milk yield kg/day Production peak Dry matter intake kg/day Intake peak Body weight kg Weeks of lactation 0 Body weight loss Body weight gain Calf body weight

35 Milk production kg/day Peak and lactation performance Lactation curve Peak lactation kg/day Lactation performance kg One additional kg of milk at peak equals 200 kg more milk for the lactation Month of lactation

36 Effect of plane of feeding on lactation yield Milk production kg/day Proper feeding during the entire lactation Poor feeding during the entire lactation Month of lactation