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 Years III NE Value of Feeds for Dairy Cows a Dairy Cow Production Stages b The Challenge of Feeding Lactating Cows c Importance of Milk Composition and Quality d Impacts of type of diet IV Maintaining Adequate Fiber Levels a Methods to Measure Effective Fiber b Benefits V Grain Sources to Feed Cattle a Adding Buffers to Dairy Cow Diets Current Lecture Dairy Cattle Nutrition and Feeding Changes 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 again NE Value of Feeds for Dairy Cows NE value of feeds is affected by nutrient composition of feeds physiological function of the animal Effects of Nutrient Composition on NE Value of Feeds These 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 NE Effect 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 cattle Net Energy Value of Feeds for Dairy Cattle Energy Unit Corn Grain Mcal kg Poor quality Hay Mcal kg Gross Energy 4 5 4 5 Digestible Energy 3 5 1 7 Metabolizable Energy 3 1 1 3 Net Energy Maintenance 1 94 0 75 Net Energy Lactation 1 87 0 93 Net Energy Growth 1 30 0 19 Impact of Level of Production on Nutrient Requirements of a 1300 lb Dairy Cow Requirements Dry Cow 20 70 120 Increase Over Dry Cow NEl Mcal day 10 16 32 47 4 9X CP g day 406 1117 3079 4988 12 0X Ca g day 24 51 119 188 8 0X DMI lb day 20 30 45 70 3 5X to meet nutritional needs you must increase DMI and nutrient density of feed Dairy Cow Production Stages Phase Time Event s I Early Lactation 0 to 10 weeks Peak of milk production occurs within 3 6 weeks II Milk Lactation 10 to 24 weeks Milk yield begins to lower peak DMI between 11 13 wks III Late Lactation 24 weeks Milk yield lowers regain body tissue IV 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 and muscles and calcium takes from skeletal tissue As the stages go on lactation becomes less important and reproduction takes its place The Challenge to Feeding Lactating Dairy Cows Goal provide high energy diets to allow cows to achieve their genetic potential to produce milk Dilemma feeding high grain diets more milk but too much dietary starch may damage rumen papillae 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 maintaining adequate dietary fiber levels to avoid rumen damage and milk fat depression Importance 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 L Impact of Type of Diet On Rumination Time Saliva Production and Rumen pH fed more roughage time spent chewing increases increasing saliva production and rumination time key component of saliva is sodium bicarbonate greatly ups rumen pH less acidic and increases microbe population On 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 milk production Summary 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 precursor Maintaining Adequate Fiber Levels Rule 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 forage Why 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 chewing Methods to Measure Effective Fiber Roughage 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 DM Penn State Particle Size Seperator sorts feeds into 3 particle sizes large 0 75 inches medium 0 3 and 0 75 small 0 3 Recommended for a TMR 6 10 large particles 30 50 medium particles 40 60 small particles Benefits of Adequate Fiber Levels short term benefits cow