Studies on the nutritive value of lucerne for dairy cows

Du Toit, Francois (Francois Johannes) (2001-12)

Thesis (MScAgric)--University of Stellenbosch, 2001.

Thesis

ENGLISH ABSTRACT: An experiment was conducted to determine whether the quality of lucerne hay could be improved by artificial drying in a forced air bulk dryer (FABD) in comparison to lucerne hay produced by natural drying in the field. Lucerne fields were divided into four blocks of equal size and blocks were randomly assigned to each of the two treatments (natural or artificial drying). Lucerne was harvested at an early to mid flowering stage on six occasions. In two blocks, cut lucerne was left in the field to dry. Material in the remaining two blocks were left in the field for an initial drying period of no longer than 24 hours, after which it was transferred to a FABD. Samples oflucerne were taken at the time of harvest and then at regular intervals (on average 0, 4, 8,22,26,29,47,50,53, 56, 58,69, 72, 76 and 80 hours after cutting) in the field and in the FABD until the material was dry enough for baling (ca. 15-18% moisture). Collected lucerne samples were dried in a forced draught oven until constant mass to determine moisture content. The rate of moisture loss was compared. Samples of the lucerne hay in the field and in the FABD were taken after baling to determine forage quality by means of chemical analysis. Samples were analysed for crude protein (CP), total digestible nutrients (TDN), digestible organic matter (DOM), acid detergent fibre (ADF) and neutral detergent fibre (NDF) content. Good weather conditions for natural drying during the trial period resulted in lucerne hay of similar chemical composition. Naturally dried lucerne hay had CP, ADF and NDF contents of 17.3, 41.2 and 48.0%, respectively, while values for artificially dried lucerne were 17.6, 40.6 and 47.3%. It was concluded that artificial drying of lucerne does probably not produce lucerne of a better quality than field drying under good weather conditions. In the following trials eight ruminally cannulated cows (four Jerseys and four Holsteins) were used to compare protein and fibre degradability of lucerne harvested at different stages of maturity (ie. 4, 5 and 6 weeks' regrowth), and of different lucerne products (ie. lucerne hay, lucerne leaves and 8% leaves added to hay), dried in a forced air bulk dryer. All cows received a total mixed lactation diet for the duration of the trial period. The first in situ rumen degradability trial was conducted with lucerne harvested at three stages of maturity namely after 4,5 and 6 weeks' regrowth. Bags were incubated in the rumen for time intervals of 0, 2, 4, 8, 16, 24, 48 and 72 hours. Samples were analysed for dry matter (DM), crude protein (CP) and neutral-detergent fibre (NDF) content. The effective DM, protein and NDF degradabilities of lucerne hay did not differ (P>0.05) between Holstein and Jersey cows. In Holsteins, DM degradability values calculated at an outflow rate of 0.05/h for lucerne harvested after 4, 5 and 6 weeks' regrowth were 63.1, 57.1 and 55.0%, respectively. Values of 64.6, 58.6 and 55.7% were obtained in Jerseys. CP degradability values for lucerne harvested after 4, 5 and 6 weeks' regrowth were 81.7, 77.2 and 77.6% in Holsteins and 81.3, 78.2 and 79.4% in Jerseys. NDF degradability values for lucerne harvested after 4, 5 and 6 weeks' regrowth were 35.8, 45.5 and 23.2% respectively in Holsteins and 35.1, 45.9 and 24.8% in Jerseys. Analysis of the effective DM, protein and NDF degradabilities across breeds indicated differences between lucerne harvested after 4, 5 and 6 weeks' regrowth. Rumen degradability of DM and protein was the highest for lucerne harvested after 4 weeks' regrowth. DM degradability values oflucerne harvested after 4,5 and 6 weeks' regrowth calculated at a flow rate of 0.05/h were 63.9, 57.9, 55.4%, respectively, while protein degradability values were 81.5, 77.7 and 78.5%. The lowest ruminal NDF degradability values were found for lucerne harvested after 6 weeks' regrowth. Values for NDF degradability calculated at a flow rate of 0.05/h for lucerne harvested after 4, 5 and 6 weeks' regrowth were 35.5, 45.7 and 23.7%, respectively. These results indicated that lucerne quality decreased in terms of DM, protein and NDF degradability as the plants mature. The second in situ rumen degradability trial was conducted with three different lucerne components dried in a forced air bulk dryer, namely lucerne hay, lucerne leaves and lucerne hay + 8% leaves. The procedure followed was the same as in the first in situ trial. Dacron bags, containing samples of the lucerne components were incubated in the rumen for time intervals of 0, 2, 4, 8, 16,24,48 and 72 hours. Samples were also analysed for DM, CP and NDF content and compared both between breeds and across breeds. DM and protein degradability values (rate and effective degradability) of the artificially dried lucerne hay were higher in Jerseys than in Holsteins. DM degradability values calculated for Holsteins at a flow rate of 0.05/h for lucerne hay, lucerne leaves and lucerne hay + 8% leaves were 57.6, 66.5 and 61.4%, respectively, while protein degradability values of 76.9, 75.5 and 77.9% were obtained. DM degradability values calculated for Jerseys were 62.9, 69.1 and 61.7%, respectively, while protein degradability values of 82.4, 77.6 and 78.5% were obtained. Analysis of the mean disappearance values across breeds indicated that protein degradability of lucerne hay in the rumen was higher than that of lucerne leaves. Protein degradability values calculated at a flow rate of 0.05/h for lucerne hay and lucerne leaves were 80.1 and 76.5% respectively. The NDF degradability of lucerne hay was, however, lower than what it was for lucerne leaves (24.6 vs. 29.7%).

AFRIKAANSE OPSOMMING: Studies omtrent die voedingswaarde van lusern vir melkkoeie. 'n Eksperiment is uitgevoer om te bepaal of die kwaliteit van lusernhooi verbeter kan word deur gebruik te maak van kunsmatige droging in plaas van die tradisionele landdroging. Lusernlande is in vier blokke verdeel en blokke is ewekansig aan elk van die twee behandelings (kunsmatige en landdroging) toegeken. Gesnyde materiaal in twee van die blokke is op die land gelaat vir die duur van die drogingsproses. Die materiaal in die oorblywende twee blokke is op die land gelaat vir 'n aanvanklike drogingsperiode van maksimum 24 uur, waarna dit in 'n massa-droogoond geplaas is. Lusernmonsters is net na sny op die land geneem en daarna met gereelde (gemiddeld 4,8,22,26,29,47,50, 53, 56, 58, 69, 72, 76 en 80 uur na sny) intervalle op die land en in die droër totdat die materiaal droog genoeg was om te baal. Lusernmonsters is in 'n droogoond gedroog totdat 'n konstante massa bereik is vir die bepaling van die voginhoud van die materiaal. Die tempo van vogverlies van die materiaal in die massadroër en op die land is bepaal. Monsters van die lusernhooi wat op die land en in die oond gedroog is, is na baal geneem en die chemiese samestelling van die lusernhooi is bepaal. Monsters is ontleed vir ruprotein- (RP), totale verteerbare voedingstof- (TVV), verteerbare organiese materiaal- (VOM), suur bestande vesel (SBV) en neutraal bestande vesel (NBV)-inhoud. Weersomstandighede was ideaal vir natuurlike droging van lusern en dit het aanleiding gegee daartoe dat die chemiese samestelling van die kunsmatig- en natuurlik gedroogde lusernhooi nie veel verskil het nie. Die RP, ADF en NDF inhoud van natuurlik gedroogde lusernhooi was 17.3,41.2 en 48.0% terwyl waardes van 17.6,40.6 en 47.3% vir kunsmatig gedroogde lusernhooi verkry is. Daar is bevind dat die kunsmatige droging van lusern nie 'n hoër kwaliteit hooi lewer as wat verkry kan word tydens landdroging wanneer weersomstandighede gunstig is nie. Hierna is twee degradeerbaarheidstudies gedoen. Agt koeie (vier Holsteins en vier Jerseys) met rumenkannulas, is gebruik om die proteïen- en veseldegradeerbaarheid van verskillende lusernkomponente te vergelyk. Lusern op verskillende groeistadia gesny, asook verskillende lusernprodukte wat kunsmatig gedroog is, is vergelyk. Al die koeie het gedurende die proeftydperk 'n hoë-konsentraat laktasierantsoen ontvang. Die eerste in situ degradeerbaarheidstudie is gedoen met lusern wat na 4-, 5- en 6 weke hergroei gesny is. Sakkies met lusernmonsters is in die rumen geplaas vir 0, 2, 4, 8, 16, 24,48 en 72 uur onderskeidelik. Monsters is na inkubasie in die rumen vir die DM-, RPen NBV -inhoud daarvan ontleed. Daar is bevind dat die DM-, proteïen en NBV degradeerbaarhede van lusernhooi nie verskil het (P.0>05) tussen Holstein- en Jerseykoeie nie. DM degradeerbaarhede wat by 'n deurvloeitempo van 0.05/h in Holsteinkoeie bereken is vir lusern wat na 4-,5- en 6 weke hergroei gesny is, was onderskeidelik 63.1, 57.1 en 55.0%. Die waardes wat vir Jerseys bereken is, was onderskeidelik 64.6,58.6 en 55.7%. Vir lusern wat na 4-,5- en 6 weke hergroei gesny is, was RP degradeerbaarhede 81.7, 77.2 en 77.6%, onderskeidelik, vir Holsteinkoeie en 81.3, 78.2 en 79.4%, onderskeidelik, vir Jerseys. NDFdegradeerbaarhede vir lusern wat na 4-,5- en 6 weke hergroei gesny is, was 35.8,45.5 en 23.2%, onderskeidelik, vir Holsteins en 35.1, 45.9 en 24.8%, onderskeidelik, vir Jerseys. 'n Vergelyking van die DM-, proteïen- en NBV-degradeerbaarhede wat gedoen is met die saamgevoegde data van al die diere, het daarop gedui dat verskille bestaan tussen die lusern wat na 4-, 5- en 6 weke hergroei gesny is. Die lusern wat na 4 weke hergroei gesny is, het die hoogste DM- en proteïendegradeerbaarheid in die rumen getoon. DMdegradeerbaarhede wat bereken is teen 'n deurvloei tempo van 0.05/h vir lusern wat na 4, 5- en 6 weke hergroei gesny is, was onderskeidelik 63.9,57.9 en 55.4% en proteindegradeerbaarhede was 81.5, 77.5 en 78.5%. Lusern wat na 6 weke hergroei gesny is het die laagste NDF-degradeerbaarheid gehad. Waardes wat bereken is teen 'n deurvloeitempo van 0.05/h vir lusern wat na 4-,5- en 6 weke hergroei gesny is, was onderskeidelik 35.5, 45.7 en 23.7%. Hierdie resultate dui daarop dat die kwaliteit van lusern afneem in terme van DM-, protein- en NBV-degradeerbaarhede namate die plante meer volwasse raak. Die tweede rumendegradeerbaarheidstudie is gedoen met 3 lusernprodukte wat in 'n massadroër gedroog is nl. lusernhooi, lusernblare en lusernhooi waarby 8% lusernblare gevoeg is. Dieselfde proefprosedure as tydens die eerste degradeerbaarheidstudie is gevolg. Sakkies met lusernmonsters, is in die rumen geplaas vir 0, 2, 4, 8, 16, 24, 48 en 72 uur. Monsters is ontleed vir DM-, proteïen- en NBV inhoud. Daar is gevind dat die proteïen degradeerbaarheid (tempo en effektiewe degradeerbaarheid) van kunsmatig gedroogde lusernhooi, hoër was by Jerseys as by Holsteins. DM degradeerbaarhede wat in Holsteinkoeie teen 'n deurvloeitempo van 0.05/h bereken is vir lusernhooi, lusernblare en lusernhooi + 8% blare, was 57.6, 66.5 en 61.4%, onderskeidelik, terwyl proteïen degradeerbaarhede 76.9, 75.5 en 77.9%, onderskeidelik, was. Vir Jerseys is DM-degradeerbaarhede van 62.9,69.1 en 61.7%, onderskeidlik, bereken terwyl proteïendegradeerbaarhede 82.4, 77.6 en 78.5% was. Gemiddelde verdwyningswaardes, wat bereken is deur data van al die diere saam te gebruik, dui daarop dat die proteïen degradeerbaarheid van lusernhooi in die rumen hoër was as in die geval van lusernblare. Die proteïen degradeerbaarhede wat bereken is teen 'n deurvloeitempo van 0.05/h, was 80.1 en 76.5%, onderskeidelik, vir lusernhooi en lusernblare. Die NBV -degradeerbaarheid van lusernhooi was egter laer as vir lusernblare (24.6 vs. 29.7%).

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