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TAMU ANSC 318 - Dairy Cattle Nutrition and Feeding
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ANSC 318 1st Edition Lecture 20 Outline of Last Lecture I. Growing and Finishing Cattle Nutrition and Management Outline of Current Lecture II. Changes in Dairy Numbers Over Recent YearsIII. NE Value of Feeds for Dairy Cowsa. Dairy Cow Production Stagesb. The Challenge of Feeding Lactating Cowsc. Importance of Milk Composition and Qualityd. Impacts of type of dietIV. Maintaining Adequate Fiber Levelsa. Methods to Measure Effective Fiberb. BenefitsV. Grain Sources to Feed Cattlea. Adding Buffers to Dairy Cow DietsCurrent LectureDairy Cattle Nutrition and FeedingChanges in Dairy Numbers over Recent Years•decrease in the number of milk cow operations-42% decrease from 1994 – 2003 and 38% from 2000-2009•small decrease in cow numbers-4% decrease from 1994-2003•Increase in milk production-11% increase from 94-03 and 13% from 00-10•Increase in milk production per cow-16% increase from 94-03 and 13% from 00-09•Dairy production in Texas was declining for a while but, cheese production in the panhandle has increase dairy production in Texas againNE Value of Feeds for Dairy Cows•NE value of feeds is affected by:-nutrient composition of feeds-physiological function of the animalEffects of Nutrient Composition on NE Value of FeedsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.•NE value of feeds is a function of their nutritional content (starch, fiber, etc.)-NE = ME – HI  (ME accounting for fecal, urine, and methane)-heat increment***: fiber > starch > fat•Therefore:-ME from roughages: higher HI  lower NE value-ME from grains: lower HI  higher NE value-ME from rendered fat: very low HI  very high NEEffect of Physiological Function on NE Value of Feeds for Dairy Cows•Heat Increment-highest when ME is used for growth-lowest when ME is used for maintenance or lactation•Therefore:-Me used for growth: higher HI  lower NEg-ME used for maintenance: lower HI  higher NEg-ME used for lactation: lower HI  higher NEg•NEm and NEl are very similar, that is why only NEl is used for dairy cattleNet Energy Value of Feeds for Dairy CattleEnergy Unit Corn Grain, Mcal/kg Poor-quality Hay, Mcal/kgGross Energy 4.5 4.5Digestible Energy 3.5 1.7Metabolizable Energy 3.1 1.3Net Energy – Maintenance 1.94 0.75Net Energy – Lactation 1.87 0.93Net Energy – Growth 1.30 0.19Impact of Level of Production on Nutrient Requirements of a 1300 lb Dairy CowRequirements Dry Cow 20 70 120 Increase OverDry Cow ****NEl, Mcal/day 10 16 32 47 4.9XCP, g/day 406 1117 3079 4988 12.0XCa, g/day 24 51 119 188 8.0XDMI, lb/day 20 30 45 70 3.5X•to meet nutritional needs you must increase DMI and nutrient density of feedDairy Cow Production Stages*****Phase Time *** Event(s)I. Early Lactation 0 to 10 weeks Peak of milk production occurs within 3-6 weeksII. Milk Lactation 10 to 24 weeks Milk yield begins to lower, peak DMI between 11-13 wksIII. Late Lactation >24 weeks Milk yield lowers, regain body tissueIV. Dry Period 5 to 8 weeks Dry period. Late pregnancy (rapid fetal growth)V. Transition Period 2 to 3 weeks Dry period. Late pregnancy. Prepare for Lactation.•In Phase 1  milk production > DMI meaning the cow will lose weight during this stage-cow is not only deficient in energy but, also amino acids (steals protein from fat andmuscles) and calcium (takes from skeletal tissue)•As the stages go on, lactation becomes less important and reproduction takes its placeThe Challenge to Feeding Lactating Dairy Cows•Goal:-provide high energy diets to allow cows to achieve their genetic potential to producemilk•Dilemma:-feeding high grain diets = more milk, but too much dietary starch may damage rumenpapillae and depress milk fat due to inadequate intake of dietary fiber-need rumens to stay healthy because dairy cows are used for years•Challenge:-feed diets with sufficient energy to support maximal milk production while maintainingadequate dietary fiber levels to avoid rumen damage and milk fat depressionImportance of Milk Composition and Quality•Producers are paid for milk volume•they are also paid for milk composition$0.16/cwt bonus per 0.1% increase in milk fat above 3.5%$0.10/cwt bonus per 0.1% increase in milk protein above 3.2%•also paid for milk quality$0.03/cwt bonus per 20,000/L decrease in somatic cell count below 400,000/LImpact of Type of DietOn Rumination Time, Saliva Production and Rumen pH•fed more roughage, time spent chewing increases, increasing saliva production and ruminationtime-key component of saliva is sodium bicarbonate  greatly ups rumen pH (less acidic)and increases microbe populationOn Volatile Fatty Acid Production•there are 2 types of rumen microbes  those that like starch and those that like fiber•by increasing the amount of roughage, we increase fiber, making fiber-loving microbes happy, and causing them to produce more acetate and less propionate-acetate increase fat production in mammary glands and is a precursor for milkproductionSummary•increase grain diets  provide substrates for starch-loving microbes•increase lactic acid production which causes rumen pH to decrease•Increase starch-loving microbe population•decrease fiber-loving microbe population•decrease rumination time•decrease production of saliva which decreases the amounts of rumen buffers•dietary fiber suggestions•decrease in acetic acid production•decrease in milk fat synthesis as acetic acid is the metabolic precursorMaintaining Adequate Fiber LevelsRule of Thumb•Formulate diet to contain a minimum forage:concentration ratio of 40:60•formulate diet to contain minimum of 17% crude fiber or 21% ADF•feed minimum of 1-1.5% of body weight as forageWhy Rule of Thumb May be Wrong•netter to consider effective fiber level of the diet, not just total fiber level•effective fiber is defined as the properties of a feed that cause a cow to chew•the higher the effective fiber of a feed the more time a cow will spend chewing/ruminating•effective fiber of a feed is dependent upon:-particle size (increase rumination)-amount of fiber (increase chewing)-type of fiber (proportion of lignin); increase lignin = increase chewingMethods to Measure Effective FiberRoughage Value Index•RVI is determined by measuring the amount of time a cow spends chewing•RVI is expressed as minutes chewing per unit of feed DMPenn State Particle Size Seperator•sorts


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TAMU ANSC 318 - Dairy Cattle Nutrition and Feeding

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