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
The digestive tract Right side view Large Intestine Colon Rectum Cecum Small Intestine Duodenum Jejunum Ileum Rumen Reticulum Omasum Abomasum
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.
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).
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).
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).
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.
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
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
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 15-23 % 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%
Density of forages and concentrates Forages: Large volume per unit of weight Concentrates: Small volume per unit of weight
Starch granule structure Potato Corn Grain Oats Wheat
Effects of maturity on forage quality 80 70 60 50 40 30 20 10 0 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 1.6 1.5 1.4 1.3 1.2 1.1 1.0 As green plants mature quality decreases because of: a decrease in energy content an increase in fiber content a decrease in protein content
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
Corn growth and maturity Constituents of plant dry 100 matter, % 90 80 70 60 50 40 30 20 10 0 Age, days Dry matter, % 20 Fully dented Late dent Dough to early dent Late milk to dough Milk stage 40 14 60 20 80 27 Grain Cob & Silk Husk & Ear Shank Leaf Sheaths Leaves 100 29 120 35 Dented Dented Dough Dough Milk Milk Black layer Milk line Mature Immature
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
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
Acidity and ph scale Acid Neutral Alkaline 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Acids produced in the abomasum Acids produced in the rumen Optimum ph for ruminal fermentation Saliva Bicarbonate
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 40 30 Acetic Acid 20 Butyric Acid Rumen ph Milk production (kg/day) 6.5 6.0 5.5 5.0 Fat in the milk (%) Concentrates Forages 20 40 60 80 60 40 80 % ration dry matter 20 % ration dry matter
Concentrate feeding and rumen acidosis ph of rumen content 7.0 6.5 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 5.0 0 6 12 18 24 Hours Concentrate feeding
Concentrate feeding and rumen acidosis (cont.) (cont.) ph of rumen content 7.0 6.5 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 5.0 0 6 12 18 24 Hours Concentrate feeding
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
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
Estimation of of body weight by measurement of of hearth girth circumference Hearth girth (cm) (inches) Body weight Holstein cows (kg) 170 67 395 173 68 412 175 69 430 178 70 448 180 71 466 183 72 485 185 73 504 188 74 523 191 75 543 193 76 563 196 77 583 198 78 604 201 79 625 203 80 645 206 81 666 208 82 687 213 84 729 216 85 753 218 86 777 Position of the tape to measure hearth girth
Dry matter intake of dairy cows Body Weight, kg 400 500 600 700 800 Dry matter intake (kg/day) At maintenance (open, non-lactating) 5.7 6.8 7.8 8.7 9.6 Dry and pregnant (dry period) 7.4 8.8 10.1 11.3 12.5 In mid- and late lactation* Milk yield (kg/day) 2 7.0 8.1 8.9 10.0 11.0 10 11.7 12.5 13.0 13.9 14.9 20 15.9 16.6 17.0 17.7 18.8 30 19.3 20.1 20.5 21.1 22.3 40 22.2 23.1 23.6 24.2 25.4 * In early lactation, dry matter intake may be reduced by as much as 18%.
Milk yield and energy density required in the diet 45 40 35 30 25 20 15 10 Energy requirement Mcal NEl/day Dry matter intake, kg/day Energy density of the ration, Mcal NEl/kg dry matter 1.7 1.6 1.5 1.4 1.3 1.2 1.1 5 Dry and Pregnant Cows 10 20 30 Milk yield, kg/day 40 1.0
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
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 100 80 60 40 20 0 20 40 60 80 Forage, % Concentrates,%
Forage to concentrate ratio and volume of the diet? (F : C) 30:70 (F : C) 50:50 Increasing volume (F : C) 80:20
Intake regulation Dry matter intake (kg/day) 25 20 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 15 10 100 80 60 40 20 0 Percentage of forage in the diet
Effect of milk production on dry matter intake 27 24 21 18 15 12 Dry matter intake (kg/day) Rumen fill limitation Milk production 35 kg per day 25 kg per day 15 kg per day 9 6 100 80 60 40 20 Forage in the ration, (% of ration dry matter) 0 Dry and pregnant cows
Effect of forage quality on dry matter intake Milk yield 25 kg/day 27 24 Dry matter intake (kg/day) Forage quality 21 Excellent (40% NDF*) 18 15 Medium (55% NDF) 12 Poor (85% NDF) 9 * NDF = Neutral Detergent Fiber 100 80 60 40 20 Forage in the ration (% of ration dry matter) 6
Effect of concentrate feeding on lactation yield Lactation yield (kg) 7500 7000 0.4 0.2 6500 6000 5500 5000 2.5 1.2 kg of additional milk per kg of concentrate fed 4500 Concentrates and minerals, % 2 13 27 36 47 Forage, % 98 87 73 64 53 Average amount of concentrates offered during the lactation (kg/day) 0 3.5 4.8 6.4 8.5
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 4 8 12 16 20 24 28 32 36 40 Calf body weight 44 48 52
Milk production kg/day 40 35 30 25 20 15 10 5 Peak and lactation performance Lactation curve Peak lactation kg/day 40 28 20 12 Lactation performance kg 10000 7000 5000 3000 One additional kg of milk at peak equals 200 kg more milk for the lactation. 0 1 2 3 4 5 6 7 8 9 10 11 Month of lactation
Effect of plane of feeding on lactation yield Milk production kg/day 7000 30 Proper feeding during the entire lactation 25 2000 5800 20 5000 800 15 5000 5200 10 5 0 1 2 3 4 Poor feeding during the entire lactation 5 6 7 8 200 5000 9 10 11 Month of lactation