Basic Requirements. of meeting cow herd production and profitability goals for the beef cattle enterprise.

Transcription

1 Basic Requiremets It is imperative that cattle producers have a adequate uderstadig of the basic utriet requiremets of the cow herd to make iformed ad effective utritio-related decisios. by Matt Hersom, Uiversity of Florida M eetig the basic utriet requiremets of beef cows is a key compoet of meetig cow herd productio ad profitability goals for the beef cattle eterprise. Table : Itake guidelies, as % of body weight, for beef cows, by forage quality Low-quality forage (<% TDN) Usupplemeted Protei supplemeted Eergy supplemeted Medium-quality forage (-% TDN) Usupplemeted Protei supplemeted Eergy supplemeted High-quality forage (>% TDN) Usupplemeted Protei supplemeted Eergy supplemeted Gestatig cow Lactatig cow Above pouds (lb.) of supplemet, each lb. of supplemet decreases forage cosumptio by 0. lb. Poud-for-poud substitutio of supplemet for forage. ANGUSJoural Jauary 0 Adequate utritio is vital for adequate cow reproductio, cow ad calf health, ad growth of all classes of cattle. Nutriet requiremets of cattle chage throughout the year based upo stage of the productio cycle, age, sex, breed, level of activity, pest load ad eviromet. All of these factors have a additive effect o the utriet requiremets of cattle. I all cases, specific adjustmets to the stadard utriet requiremets may be warrated. Therefore, it is imperative that cattle producers have a adequate uderstadig of the basic utriet requiremets of the cow herd to make iformed ad effective utritio-related decisios. I most productio situatios, the basis for cow herd utriet supply is grazed or harvested forage. With the use of forage comes the eed for seasoal supplemetatio strategies to compesate for forage-quality deficiecies. Without kowledge of the cow s basic utriet requiremets, effective ad

2 cost-effective supplemetatio practices will be difficult to implemet. This article will discuss the basic utriets that are required for productio ad provide tables idicatig diet cocetratio ad daily itake requiremets of key utriets for beef cattle. The iformatio cotaied here is based upo the recommedatios published i the Nutriet Requiremets of Beef Cattle (000). Dry-matter itake Beef cattle have o requiremet for feed itake; however, cosumptio of adequate levels of feedstuffs is imperative to deliver the required utriets for adequate productio. Dry-matter itake (DMI) is affected by a umber of factors, icludig cow body weight, stage of productio, forage quality, supplemetatio level ad type, ad evirometal factors. Cattle of larger frame size ad body weight have greater potetial to cosume forage ad feed compared to smaller-frame or lighterbody-weight cattle. Likewise, lactatig cows have greater DMI potetial compared to gestatig cows. Additioally, thi cows are more likely to cosume greater amouts of feedstuffs compared to well-coditioed cows. Forage itake is geerally limited by forage quality. The greater the forage quality (eergy ad protei cocetratios, digestibility, etc.) of the base forage, the greater the potetial for icreased DMI by cattle. The estimates of DMI listed i the tables were determied by predictio equatios. These predictio equatios assume diets that are adequate i all required utriets. Likewise, examiatio of the tables will show that differeces i DMI occur across mature body weight, cow milkig ability ad stage of productio cycle. Table provides some geeral guidelies for predictio of forage DMI based upo forage quality ad cow productio stage. Water Water is a importat, yet sometimes overlooked, utriet required by cattle. Water is a vital compoet i may body fuctios, icludig temperature regulatio, growth, reproductio, lactatio ad may metabolic fuctios. Water comes from two sources: feedstuffs ad ad libitum cosumptio. The water requiremet is iflueced by several factors, icludig pregacy, lactatio, activity, type of diet, level of itake ad evirometal temperature. Restrictio of water itake below requiremet will reduce feed itake, which will reduce cattle productio. Cattle lose water from the body through a umber of routes. Sources of water loss Table : Approximate total daily water requiremet, i gallos, of beef cows ad bulls Pregat cows 00 lb.,00 lb. Lactatig cows All weights Mature bulls,00 lb.,00 lb. Temperature, F Adapted from the Nutriet Requiremets of Beef Cattle, published by the Natioal Research Coucil, 000. Water itake of a give class of cattle i a specific maagemet system is a fuctio of DMI ad temperature. Water itake is costat up to 0 F. DMI has a major ifluece o water itake. Heavier cows are assumed to be i better coditio ad thus require less DMI ad, i tur, less water itake. urie, feces, sweat, ad water vapor from the ski ad lugs. Urie productio depeds upo activity level, air temperature, water cosumptio ad other factors. The amout of water loss i the feces depeds upo the diet. Clea water is especially importat for youg growig cattle, while dirty water ca decrease cattle performace ad be a potetial source of disease. Basic total water itake requiremets are idicated i Table. Eergy Eergy requiremets are expressed i the followig tables i terms of total digestible utriets (TDN) ad et eergy for maiteace (NEm). Total digestible utriets are the sum of digestible starch, fiber, protei ad fat i the feedstuffs. Eergy requiremets, expressed as TDN, are show i the tables as a percet of the diet dry matter or as pouds per day. The et-eergy (NE) system assigs eergy values of feeds accordig to how the eergy withi a feedstuff ca be assiged to either maiteace or growth/lactatio/ pregacy. Likewise, the amout of eergy eeded for maiteace or growth ca be determied idepedet of the dietary compositio. The NEm requiremet is expressed as megacalories (Mcal) per poud or megacalories per day. Cow eergy requiremets chage throughout the year. The requiremet for eergy by the mature cow is a dyamic situatio because the productio cycle is ot static. At o poit i a yearly productio cycle does a cow experiece oly maiteace eergy requiremets. We may say that a cow is just maitaiig herself, but if she is a productive member of the herd, more tha maiteace is occurrig o a daily basis. Maiteace is defied as the amout of feed eergy itake that will result i o et loss or gai of eergy from the tissues of the cow s body. I reality, a cow must always be addig or subtractig eergy from her body tissues. The additive fuctios to maiteace iclude growth, gestatio ad lactatio. All ogoig eergetic fuctios result i the total eergy requiremet of the Maiteace. Iterestigly, ot all maiteace is cosidered equal. There exist two distict phases of NEm requiremets: durig the lactatio period ad durig the dry period. About a 0% differece exists betwee these two periods. This icrease i maiteace eergy requiremet associated with lactatio is due to the icreased metabolic demad upo body tissues, ot the resultig product of lactatio (milk). Additioally, the iitial eergy requiremet does ot accout for ay eergy expediture for activity associated with grazig. The differece i maiteace eergy requiremets for grazig cattle could be from 0% to 0% depedig upo the grazig coditios ad forage Lactatio. The eergy requiremet for lactatio is a fuctio of milk yield, milk fat percet ad milk protei percet. CONTINUED ON PAGE Jauary 0 ANGUSJoural

3 Basic Requiremets CONTINUED FROM PAGE These variables chage durig the lactatio cycle. Thus, the eergy requiremet of lactatio chages accordigly. Idetified differeces betwee ad withi breeds that affect milk yield ad milk compositio also affect the lactatio eergy requiremet. Ulike other eergy requiremets, lactatio has a rapid oset of demad for eergy that is iitiated by parturitio. The developmet of mammary tissue occurs prepartum, but the majority of the lactatio eergy requiremet is associated with milk productio. cycle. Whereas the eergy required for gestatio is iitially very small, just 0.% of the eergy requiremet durig the third moth postpartum. I cotrast, the gestatio eergy requiremet oe moth prior to parturitio is approximately % of the total eergy requiremet. The postweaig period is ofte referred to as a maiteace period for the grazig beef cow. Ideed, gestatioal requiremets at weaig do ot equate to the greater eergetic demad of lactatio; however, this is a importat eergetic supply ad demad period. This period is utilized for growth of the products of Gestatio. The eergy requiremet associated with pregacy is a uderlyig eergetic demad for 0 out of moths durig the yearly productio cow herd ca be costrued as the recovery of body-tissue eergy (i.e., body weight ad body coditio) ot associated with the products of coceptio. Durig a small time period after the cessatio of lactatio ad prior to the accelerated fetal growth, additioal eergy supplied to the cow ca be used for growth of body tissues. This growth is used to regai lost body weight ad body coditio score (BCS) due to the mobilizatio of body tissues durig lactatio. These accreted body tissues will most likely be reused at some poit durig the productio cycle to support maiteace or lactatio. Growth. Growth i the case of the mature Protei requiremets are expressed i the Table : Nutriet requiremets of a,000-lb. mature cow, by peak milk-productio level Moths sice calvig 0 lb. peak milk productio C lb. peak milk productio C lb. peak milk productio C Adapted from the Nutriet Requiremets of Beef Cattle, published by the Natioal Research Coucil, 000. ANGUSJoural Jauary 0

4 tables i terms of crude protei (CP). The protei requiremet of cattle is show i the tables as a percet of the diet dry matter or as pouds per day. Similar to eergy, a cow s protei requiremets chage throughout the year. The requiremet for protei is depedet upo the age of the cow, stage of productio ad level of productio. Protei requiremets, like eergy, are additive durig ay poit i the cow s productio cycle. The CP system, as the ame implies, is a crude measuremet of the protei i ay feedstuffs. The amout of CP i a feedstuff is a calculatio determied by the followig equatio: CP = itroge cocetratio.. The CP system is the basic descriptio of protei for cattle. However, protei requiremets have bee further characterized to idicate the amout of protei that is actually available for the cow to metabolize. Cattle protei requiremets are met by two basic sources: the feedstuffs they cosume ad the microorgaisms that populate the rume. The protei compoet of feedstuffs ca be divided ito two fractios idetified as degradable itake protei (DIP) ad udegradable itake protei (UIP). The DIP fractio is composed of the protei fractio of the diet that is digested i the rume, used by rume microorgaisms, ad ultimately results i bacterial (microbial) protei; or that passes through the rume wall as ammoia ad is ultimately metabolized i the liver. I the liver, excess itroge (N) is metabolized to urea, which ca be recycled back to the gastroitestial tract or excreted through the kidey ito urie. The UIP fractio is composed of the protei fractio of the diet that is ot digested i the rume ad that thereby escapes or bypasses the rume. The UIP protei may the be digested ad absorbed i the small itestie. Together, the bacterial protei ad UIP fractio comprise the metabolizable protei available for the cow to meet her protei Maiteace. The geeral rule of thumb is that forages with a CP cocetratio of % or greater are adequate to meet a CONTINUED ON PAGE Table : Nutriet requiremets of a,00-lb. mature cow, by peak milk-productio level Moths sice calvig 0 lb. peak milk productio..... C lb. peak milk productio C lb. peak milk productio C Adapted from the Nutriet Requiremets of Beef Cattle, published by the Natioal Research Coucil, 000. Jauary 0 ANGUSJoural

5 Basic Requiremets CONTINUED FROM PAGE mature cow s CP requiremets. Research has show that the bacterial protei fractio of the diet ca provide aywhere from 0% to all of the cow s metabolizable protei requiremet depedig upo the UIP cotet of the diet. This would imply that forage-based diets of sufficiet CP cocetratio ca maitai a mature cow durig certai phases of the cow s productive Lactatio. Lactatio is the most stressful time i the cow productio cycle. Milk cotais a large cocetratio of protei. The source of the protei i milk comes either from dietary sources or mobilizatio of body lea tissue. Mobilizatio of lea tissue decreases the overall BCS of the cow. Research idicates that maiteace of BCS from calvig to rebreedig is imperative to esure acceptable coceptio rates. Therefore, adequate protei from the diet is a importat utritioal cosideratio. up to parturitio are largely associated with fetal growth ad other products of coceptio. Durig this period, the cow will sacrifice body coditio to support fetal growth. Additioally, adequate protei status leadig up to parturitio is essetial for the productio of adequate high-quality colostrum to support ewbor calf Gestatio. The effect of gestatio does ot greatly affect the cow s protei requiremet durig the first seve moths of gestatio. The majority of the protei requiremet is associated with placetal developmet ad growth. However, durig the last two moths of gestatio, two-thirds of the fetal growth occurs. This fetal growth results i a large demad o materal protei supply. Thus, protei requiremets Growth. Like eergy, protei requiremets for mature cattle are associated with the recovery of lea body tissue that was mobilized durig the productio cycle. Lea-tissue mobilizatio supplies a good deal of protei whe it is eeded. However, because of differeces i the efficiecy of Table : Nutriet requiremets of a,00-lb. mature cow, by peak milk-productio level Moths sice calvig 0 lb. peak milk productio C. 0 lb. peak milk productio C. 0 lb. peak milk productio C Adapted from the Nutriet Requiremets of Beef Cattle, published by the Natioal Research Coucil, 000. ANGUSJoural Jauary 0

6 protei usage, a greater amout of dietary crude protei beyod maiteace requiremets is eeded to replace the mobilized tissue. Calcium ad phosphorus Calcium (Ca) is the most abudat mieral i the body ad is a importat compoet for boes, teeth, membrae permeability, muscle cotractio ad may other metabolic fuctios. The calcium requiremets listed i the tables are coverted to dietary calcium requiremets, assumig a true absorptio of 0%. Absorptio of calcium is largely determied by the balace of requiremet ad itake. Skeletal reserves serve as a large repository of calcium that ca be used to maitai blood cocetratios. Phosphorus (P) is geerally discussed with calcium because the two mierals fuctio together i boe metabolism. Phosphorus is predomiatly associated with boes ad teeth, but also fuctios i cell growth, eergy usage ad membrae formatio. Historically, the calcium-to-phosphorus ratio recommedatio has bee -to-; however, research has idicated that ratios betwee -to- ad -to- result i similar performace assumig that the dietary phosphorus requiremet was met. have requiremets for eergy ad specific utriets. Eergy ad other utriets will first be used to meet the cow s maiteace requiremets, ad the utriets ad eergy will be allocated to productive uses (growth, reproductio ad lactatio). The data preseted i these tables are to be used as guidelies ad a startig poit for utritio decisio-makig. Editor s Note: Matt Hersom is associate professor i the aimal sciece departmet at the Uiversity of Florida Istitute of Food ad Agricultural Sciece (UF/IFAS), Gaiesville. This documet was origially published i October 00 as AN0, oe of a series published by the aimal sciece departmet of UF/IFAS. It was reviewed i 00. Coclusios The key cocept to remember i feedig a beef cow herd is the cattle eed to be fed to meet utriet requiremets. Cows do ot have requiremets for specific feeds; they Table : Nutriet requiremets of a,00-lb. mature cow, by peak milk-productio level Moths sice calvig 0 lb. peak milk productio C lb. peak milk productio C lb. peak milk productio C Adapted from the Nutriet Requiremets of Beef Cattle, published by the Natioal Research Coucil, 000. Jauary 0 ANGUSJoural