Two trials were conducted to determine the effect of protein degradability (low (LD) vs high (HD)) and evaporative cooling (shade cooling vs shade) on performance of 60 lactating Holstein cows in mid-lactation. Cooling and the LD diet increased milk production, 3.5% FCM and feed efficiency in trial 1 (24 cows) while in trial 2 (36 cows) LD diet increased milk production and feed efficiency and cooling did not exert a significant effect. Differences between trials were probably due to higher environmental temperature humidity indexes (77.0 vs 72.0), and a higher quality of the rumen bypass protein in the LD diet in trial 2 than trial 1. Cooling reduced respiration rates in trial 1 and respiration rates, rectal and inner ear temperatures in trial 2. Eating patterns were unaffected by protein degradability or cooling.

Thesis (MscAgric (Animal Sciences))--University of Stellenbosch, 2006. / Six non-lactating, ruminally cannulated Holstein cows were used in a three part study to determine the effect of biotin supplementation to dairy cows on forage fermentation characteristics. Cows were randomly assigned to two groups in a 2 x 3 change-over experiment. All cows received oat hay ad libitum and one of two concentrate feeds, fed twice daily at 2 kg per feeding as a top dressing. The concentrates were identical in composition, except for a premix that was included to provide either 0 or 40 mg supplemental biotin/cow per day when the concentrate was fed at a rate of 4 kg/cow. Cows received the respective treatments for 28 days before being changed over to the other treatment. All cows therefore received both treatments. The first 21 days in each period were used for adaptation, while the last 7 days of the period were used for an in sacco trial, as well as for the collection of rumen liquor for two in vitro studies. The in vitro studies were a gas production trial and an in vitro digestibility trial. Forages differing in neutral detergent fibre (NDF) content were used as substrates in the study. Lucerne hay (440 g NDF/kg DM), oat hay (680 g NDF/kg DM), and wheat straw (798 g NDF/kg DM) were chosen to represent high, medium and low quality forages. In the gas production study, samples (0.5 g) of the three forages were incubated at 39ºC in buffered rumen liquor (obtained from cows in the different treatments) in glass vials. Pressure readings were taken after 12, 18, 24, 30 and 48 hours incubation using a digital pressure gauge fitted with a 21 gauge needle. Pressure readings were converted to gas volumes with the aid of a predetermined regression equation. In the in vitro digestibility trial, forage samples (0.25 g) were weighed into Ankom F57 filter bags and incubated at 39ºC in an Ankom Daisy II incubator in buffered rumen liquor. Three bags of each substrate were removed from the incubation jars after 18, 24 and 30 h incubation. Bag residues were analyzed for dry matter, organic matter and NDF. In the in sacco degradability trial, forage samples (5 g) were weighed into 100 x 200 mm Ankom Forage Bags and inserted into the rumina of the respective cow simultaneously. One bag per substrate was removed from each cow at after 4, 8, 18, 24, 30 and 48 h incubation, while two bags per substrate were removed after 72 and 96 h to ensure enough residue for subsequent chemical analysis. Samples of rumen liquor were taken at each of the mentioned incubation times for VFA analysis, while rumen pH was also measured at these times. All the data collected were subjected to a one-way ANOVA, least square means were determined and significance was declared at P<0.05. Biotin supplementation increased the rate of gas production (0-12 h) of all three substrates, as well as cumulative gas production at 48 h. No treatment effects were observed in the in vitro digestion study. Biotin supplementation increased the rate of in sacco NDF disappearance and calculated effective NDF degradability in oat hay and wheat straw, but not in lucerne hay. The rumen pH curve appeared higher for the biotin treatment than for the control and the value at the 72 h sampling time was significantly higher for the biotin treatment than for the control treatment (6.13 vs 5.94). Rumen pH tended to be higher (P<0.10) at 18 h (6.44 vs 6.23), 48 h (6.13 vs 6.00) and 96 h (6.14 vs 6.04). There was also a tendency (P<0.10) for the mean pH over the total 96 h period to be higher for the biotin treatment than for the control (6.09 vs 5.97), while the maximum and minimum pH values did not differ between treatments. Molar proportions of volatile fatty acids did not differ between treatments and the acetic acid proportion was relatively high (acetic:propionic = 74:15), which was probably because the cows were not on a very high concentrate diet. It was concluded that biotin supplementation to dairy cows may improve fermentation rates and NDF digestibility of certain forages.

Thesis (MScAgric) -- Stellenbosch University, 2009. / ENGLISH ABSTRACT: Ruminants have a compound stomach system that enables them to utilize forages more efficiently than monogastric animals. However, forages alone do not contain sufficient nutrients to meet the requirements of high producing dairy cows. Forages are high in fibre and their nutrient availability depends on the degree of cell wall degradability. Improvements in forage fermentation would increase energy intake and subsequently milk production and performance by dairy cows. It is therefore important to find ways to improve forage degradation and utilization in the rumen. The use of different non-fibre carbohydrate (NFC) sources has different effects on animal performance. Supplementing forage based diets with energy sources containing sugar, starch or pectin results in variation in performance measurements such as milk yield, milk composition and dry matter intake (DMI). This thesis reports on two studies in which the effect of energy supplementation on forage fermentation and digestion parameters was investigated. In the first study an in vitro gas production protocol was used to determine the effect of sugar (molasses), starch (maize meal) and pectin (citrus pulp) on total gas production and rate of gas production of different forages. The forage substrates included wheat straw (WS), oat hay, (OH) lucerne hay (LUC), ryegrass (RYE) and kikuyu grass (KIK). The three energy sources, as well as a control (no energy source) were incubated in vitro with each of the above mentioned forages. Rumen fluid was collected from two lactating Holstein cows receiving a diet consisting of oat hay, lucerne, wheat straw and a concentrate mix. Forages alone (0.25 g DM) and/or together (0.125 g DM) with either molasses (0.1412 g DM), citrus pulp (0.1425 g DM) or maize meal (0.125 g DM) were weighed into glass vials and incubated for 72 hours. The weights of the energy sources were calculated on an energy equivalent basis. Blank vials, that contained no substrates, were included to correct for gas production from rumen fluid alone. The substrates were incubated in 40 ml buffered medium, 2 ml of reducing solution and 10 ml rumen fluid. Gas pressure was recorded automatically every five minutes using a pressure transducer system and the method based on the Reading Pressure Technique (Mauricio et al., 1999). Gas pressure was converted to gas volume using a predetermined regression equation. In the first gas production trial, the gas production included gas produced by the energy sources, while in the second gas production trial, the energy source gas production was deducted from the total gas production to determine the effect of energy source on gas production of respective forage substrates per se. Data were fitted to two non-linear models adapted from Ørskov and McDonald (1979). Significant forage x energy interactions were observed for the non-linear parameter gas production (b) in Model 1 and for b and lag phase (L) in Model 2 in both trials. In the first gas production trial, the higher fermentability of the energy sources supplemented to forage substrates, increased b (Model 1 & 2) of the LUC and WS. The gas production rate was affected in different ways for different forages, with the most noticeable effect on WS when it was supplemented with energy sources. All the energy sources increased c of WS irrespective of the model used. Energy sources had no effect on the L of LUC, OH or RYE, but decreased the L of WS and KIK. In the second trial, maize meal had no effect on b for any of the forages (Model 1 & 2), while molasses (Model 1 & 2) decreased b for all forage substrates, and citrus pulp (Model 1 & 2) decreased b of OH and RYE, to lower values than those of the control treatments. Gas production rate was not affected by molasses for any of the forage substrates, while citrus pulp (Model 1 & 2) increased c of OH and maize meal increased c of OH and KIK. Lag phase was only affected by energy sources in WS and KIK, where all the energy sources had lower L values than the control treatment. It was concluded that forage fermentability is affected differently by different energy sources. These observations may have important implications, in practice, on rumen health and milk production, and the data obtained can potentially be used as guidelines in feed formulations. In the second study, in vitro digestibility trials were undertaken to determine the effect of sugar (molasses and sucrose), starch (maize meal and maize starch) and pectin (citrus pulp and citrus pectin) on neutral detergent fibre (NDF) and dry matter (DM) degradability of forages. Forage substrates used included wheat straw, oat hay, lucerne hay, ryegrass and kikuyu grass. Rumen fluid was collected from two lactating Holstein cows receiving a diet consisting of oat hay, wheat straw and a concentrate mix. In vitro degradability was done with an ANKOM Daisy II incubator and forage substrates were incubated with or without the respective energy sources for 24, 48 and 72 hours. The substrates were incubated in 1076 ml buffered medium, 54 ml of reducing solution and 270 ml rumen fluid. The residues were washed, dried and analyzed for NDF. In the study with the applied energy sources (molasses, maize meal and citrus pulp) there were a forage x energy source interactions. Supplementation with the applied energy sources all improved dry matter degradability (DMD) of forages (24 and 72 hours), when compared to the control treatment, except for RYE supplemented with maize meal and citrus pulp at 24 hours. Molasses seemed to have had the biggest effect on DMD in all forage substrates. Supplementation with maize meal had no effect on neutral detergent fibre degradability (NDFD) of any forage substrate, except for an improvement in NDFD of LUC at 72 hours. Molasses improved NDFD of LUC at 24h, but had no effect on the other forage substrates. Citrus pulp improved NDFD of OH (72 hours), as well as LUC and WS (24 and 72 hours). It is postulated that the NDF of the energy sources was more digestible than that of the respective forages, and that the improved NDFD values could be ascribed to the contribution of the energy source NDFD. Overall, pasture grasses had a higher NDFD than the hays and straw, and appear to be more readily fermentable by rumen microbes than the low quality hays and straw explaining the higher NDFD. In the study involving the purified energy sources (sucrose, maize starch and citrus pectin), forage x energy source interactions were observed. In general, supplementation with these energy sources improved DMD at 24 and 72 hours except for RYE and KIK (72 hours). Pasture grasses (RYE and KIK) had a higher NDFD than LUC, OH and WS. At 72 hours, NDFD was 37.1% for LUC, 42.5% for OH and 40.3% for WS, compared to 70.5% for KIK and 64.9% for RYE. A possible explanation is that KIK and RYE samples came from freshly cut material, harvested after a 28d re-growth period. In general, sucrose (24 and 72 hours) and citrus pectin (72 hours) had no effect on NDFD of forage substrates. However, supplementing oat hay (24 hours) with starch and citrus pectin, and wheat straw (24 and 72 hours) with starch lowered NDFD, when compared to the control treatment. It is hypothesized that microbes fermented the easily fermentable energy sources first, before attacking forage NDF. The study suggested that forage NDFD values are not fixed, and may be altered by type of energy supplementation. / AFRIKAANSE OPSOMMING: Die meervoudige maagsisteem van herkouers stel hulle in staat om ruvoer meer effektief te benut as enkelmaagdiere. Ruvoere alleen bevat egter nie genoeg voedingstowwe om die behoeftes van hoogproduserende melkbeeste te bevredig nie. Ruvoere is ryk aan vesel en hul voedingstofbeskikbaarheid word bepaal deur die graad van selwand degradeerbaarheid. ‘n Verhoging in ruvoerfermentasie sal energieinname verhoog en gevolglik ook melkproduksie en prestasie. Dit is dus belangrik om maniere te vind om ruvoerdegradeerbaarheid en -verbruik in die rumen te verbeter. Die gebruik van verskillende nie-vesel koolhidraat (NFC) bronne het verskillende uitwerkings op die prestasie van diere. Energie-aanvullings soos suiker, stysel en pektien tot ruvoer-gebasseerde diëte, beïnvloed prestasiemaatstawwe soos melkproduksie, melksamestelling en droëmateriaalinname (DMI) op verskillende maniere. Hierdie tesis lewer verslag oor twee studies waar die invloed van energie-aanvullings op ruvoerfermentasie en verteringsmaatstawwe ondersoek is. In die eerste studie is ‘n in vitro gasproduksieprotokol gebruik om die invloed van suiker (melasse), stysel (mieliemeel) en pektien (sitruspulp) op totale gasproduksie (b) en tempo van gasproduksie (c) van verskillende ruvoersubstrate te bepaal. Ruvoersubstrate wat gebruik is, was koringstrooi (WS), hawerhooi (OH), lusernhooi (LUC), raaigras (RYE) en kikuyugras (KIK). Die drie energiebronne, sowel as ‘n kontrole (geen energiebron), is in vitro geïnkubeer saam met elk van die genoemde ruvoere. Rumenvloeistof is verkry van twee lakterende Holsteinkoeie, wat ‘n dieet ontvang het bestaande uit hawerhooi, koringstrooi en ‘n kragvoermengsel. Ruvoere is alleen en/of in kombinasie met melasse (0.1412 g DM), sitruspulp (0.1425 g DM) of mieliemeel (0.125 g DM) in glasbottels afgeweeg en vir 72 uur geïnkubeer. Die massas van die energiebronne is op ‘n energie-ekwivalente basis bereken. Leë bottels wat geen substraat bevat het nie, is ingesluit om te korrigeer vir gasproduksie afkomstig vanaf rumenvloeistof alleen. Substrate is in 40 ml van ‘n buffermedium, 2 ml reduserende oplossing en 10ml rumenvloeistof geïnkubeer. Gasdruk is elke vyf minute outomaties aangeteken deur gebruik te maak van ‘n drukmetersisteem en die metode is gebasseer op die Reading gasdruktegniek. Gasdruk is omgeskakel na gasvolume deur gebruik te maak van ‘n voorafbepaalde regressievergelyking. In die eerste proef het totale gasproduksie die gas wat deur die onderskeie energiebronne geproduseer is, ingesluit. In die tweede proef is gasproduksie afkomstig van die energiebronne afgetrek van totale gasproduksie, om sodoende die invloed van die energiebronne per se op die gasproduksie van die onderskeie ruvoersubstrate, te bepaal. Data is met behulp van twee nie-liniëre modelle gepas. Betekenisvolle ruvoer x energie-interaksies is in albei proewe waargeneem vir die nie-liniëre parameter b (gasproduksie) in Model 1, en vir b en L (sloerfase) in Model 2. In die eerste proef het die energiebronne se hoë fermentasie gelei to ‘n verhoging in b (Model 1 & 2) van LUC en WS. Energie-aanvullings het die c-waarde van die onderskeie ruvoere verskillend beïnvloed, met WS wat die mees opvallende effek gehad het. Al die energiebronne het die c-waarde van WS verhoog, ongeag watter model gebruik is. Energiebronne het geen invloed op die L-waarde van LUC, OH of RYE gehad nie, maar het wel die L-waarde van WS en KIK verlaag. In die tweede proef het mieliemeel geen invloed op die b-waarde van enige van die ruvoere gehad nie (Model 1 & 2), terwyl melasse (Model 1 & 2) die b-waarde van alle ruvoere verlaag het, en sitruspulp (Model 1 & 2) OH en RYE se b waardes verlaag het tot laer as die kontroles. Melasse het geen invloed op die c-waarde van die onderskeie ruvoersubstrate gehad nie, terwyl sitruspulp (Model 1 & 2) die c-waarde van OH, en mieliemeel die c-waarde van OH en KIK, verhoog het. Energiebronne het slegs ‘n invloed op die sloerfase in WS en KIK gehad, waar dit L verlaag het tot laer waardes as dié van die kontroles. Daar is gevind dat ruvoer-fermenteerbaarheid verskillend beïnvloed word deur verskillende energiebronne. Bogenoemde resultate kan in die praktyk betekenisvolle invloede hê op rumengesondheid en melkproduksie en die data wat verkry is, kan potensieël gebruik word as riglyne in voerformulerings. In die tweede studie is in vitro verteerbaarheidsproewe gedoen om die effek van suiker (molasse en sukrose), stysel (mieliemeel en mieliestysel) en pektien (sitruspulp en sitrus-pektien) op neutraalonoplosbare vesel (NDF) en droë materiaal (DM) degradeerbaarheid van ruvoere, te bepaal. Ruvoersubstrate wat gebruik is, was WS, OH, LUC, RYE en KIK. Rumen vloeistof is verkry van twee lakterende Holstein koeie, wat ‘n dieet ontvang het bestaande uit hawerhooi, koringstrooi en ‘n konsentraat mengsel. Die in vitro degradeerbaarheidsproef is gedoen met ‘n ANKOM Daisy II inkubator. Ruvoersubstrate is geïnkubeer met of sonder die onderskeie energiebronne vir 24, 48 en 72 uur. Die substrate is geïnkubeer in 1076 ml buffer medium, 54 ml reduserende oplossing en 270 ml rumen vloeistof. Residue is gewas, gedroog en geanaliseer vir NDF. In die proef met toegepaste energiebronne (molasse, mieliemeel en sitruspulp), was daar ruvoer x energiebron interaksies. Toegepaste energiebron aanvullings het almal DMD van ruvoersubstrate (24 en 72 uur) verbeter, uitsluitend vir RYE wat aangevul is met mieliemeel (24 uur) en sitruspulp (24 uur). Van al die ruvoersubstrate het molasse die grootste effek gehad op DMD. Mieliemeel aanvullings het geen effek gehad op neutraal-onoplosbare vesel degradeerbaarheid (NDFD) van ruvoersubstrate nie, behalwe vir ‘n verbetering in NDFD van LUC by 72 uur. Molasse het NDFD van lucern by 24 uur verbeter, maar geen effek gehad op ander ruvoersubstrate nie. Sitruspulp het NDFD van OH (72 uur), asook LUC en WS (24 & 72 uur) verbeter. Daar word beweer dat die NDF van energiebronne meer verteerbaar is as die van ruvoersubstrate, en dat die verbetering in NDFD waardes toegeskryf kan word aan die bydraes van energiebronne se NDFD. Weidingsgrasse (RYE & KIK) het oor die algemeen ‘n hoër NDFD as hooie en strooi gehad. Rumen mikrobes blyk ook om dié grasse vinniger te verteer as lae kwaliteit hooie en strooi, wat gevolglik die hoër NDFD verduidelik. In die proef met suiwer energiebronne (sukrose, mieliestysel en sitrus-pektien) is ruvoer x energiebron interaksies waargeneem. Energiebronaanvullings het DMD by 24 en 72 uur verbeter, buiten vir RYE en KIK (72 uur). Weidingsgrasse het hoër NDFD as LUC, OH en WS. By 72 uur was die NDFD van LUC 37.1%, OH 42.5%, WS 40.3%, in vergelyking met 70.5% vir KIK en 64.9% vir RYE. ‘n Moontlike verklaring vir die hoër NDFD van KIK en RYE, is omdat dit vars gesnyde material is, geoes na slegs 28 dae hergroei. Oor die algemeen het sukrose (24 & 72 uur) en sitrus-pektien (72 uur) geen effek gehad op NDFD van ruvoersubstrate nie, terwyl stysel en pektien aanvullings tot OH (24 uur), en stysel aanvullings tot WS (24 & 72 uur) NDFD verlaag het. Daar word hipotetieseer dat mikrobes eers die vinnig fermenteerbare energiebronne fermenteer, voordat hulle ruvoer NDF aanval. Hierdie studie beweer dat ruvoer NDFD waardes nie vas is nie, en dat dié waardes beïnvloed mag word deur energiebron aanvullings.

Thesis (MScAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Statistical analysis was conducted on data from two Elsenburg herds, containing 105 Jersey and 232 Holstein cows. The data was examined for external factors which may affect milk yield and milk composition. The data consisted of 337 first lactation records, taken over a 20 year time period. Breed of cow had an effect on milk yield, butterfat and protein production, as did the year in which the cows were born and the age of the heifer at first calving. There was a significant interaction between the breed and year of birth. There are other external factors, which are difficult to quantify, which may have an effect on production. In the following trials, eight ruminally cannulated dairy cows (four Jerseys and four Holsteins) were used to determine the effect of breed on forage digestibility in the rumen. All cows received a high concentrate mixed ration, with supplementary wheat straw. An in situ rumen degradability trial was conducted with three different forages, viz. lucerne, wheat straw and NaOH-treated wheat straw. The bags were incubated in the rumen for time intervals of 2,4, 8, 12, 16,20,24, 36,48, 72 and 96 hours and samples were analysed for dry matter (DM) and neutral-detergent fibre (NDF). Higher rumen degradability values (P<0.01) ofDM and NDF were observed in Jerseys for all three forages. Differences were more apparent for wheat straw and treated wheat straw than for lucerne. The rate of passage of digesta from the rumen was measured in both breeds by a chromium mordanted wheat straw marker. The Holsteins manifested a higher rate of passage (P<0.05) than the Jerseys, while daily feed intakes were also higher (P<O.Ol) for the Holsteins than for the Jerseys. Daily feed intake, expressed as percentage of body weight was, however, slightly higher for the Jerseys than for the Holsteins. The pH value of the rumen fluid was measured at 0, 4, 8, 10 and 12 hours postfeeding. The only significant difference (P<O.OI)in pH between the breeds was at 4 hours post-feeding, when the ruminal pH dropped more rapidly in the Holsteins than in the Jerseys. The pH in the Holsteins dropped below 6.2, which may have inhibited fibrolytic microbe activity in the rumen, resulting in a lower effective degradability of forages. Total volatile fatty acids were higher in Holsteins from four to 10 hours after feeding, but no differences were observed in acetic acid:propionic acid ratios. It was concluded that Jerseys appear to utilize forages more efficiently than Holsteins and that the differences are more apparent in low quality forages than in high quality forages. / AFRIKAANSE OPSOMMING: Statistiese analises is op data van twee kuddes te Elsenburg uitgevoer, bestaande uit 105 Jersey- en 232 Holsteinkoeie. Die data is ondersoek vir eksterne faktore wat melkproduksie en melksamestelling kan beinvloed. Die data het uit 337 eerste-laktasierekords bestaan, wat oor 'n periode van 20 jaar ingesamel is. Ras van die koei, sowel as die jaar van geboorte en ouderdom met eerste kalwing het 'n invloed op melkproduksie, bottervet- en proteienopbrengs gehad. 'n Betekenisvolle interaksie is tussen ras en jaar van geboorte waargeneem. Ander moeilik kwantifiseerbare faktore mag ook 'n invloed op melkproduksie he. In daaropvolgende proewe is agt rumen-gekannuleerde melkkoeie (vier Jerseys en vier Holsteins) gebruik om die invloed van ras op ruvoerverteerbaarheid in die rumen te bepaal. Al die koeie het 'n hoe-kragvoerdieet ontvang, aangevul met koringstrooi. 'n In situ rumendegradeerbaarheidstudie is met drie verskillende ruvoere, naamlik lusernhooi, koringstrooi en NaOH-behandelde koringstrooi uitgevoer. Die ruvoere is vir tye van 2, 4, 8, 12, 16, 20, 24, 36, 48, 72 en 96 ure in die rumen geinkubeer en monsters is ontleed vir droemateriaal (DM) en neutraal-bestande vesel (NDF). Hoer rumen-degradeerbaarheidswaardes (P<O.Ol) van DM en NDF is in Jerseys waargeneem as in Holsteins vir al drie ruvoere. Verskille was meer opvallend vir koringstrooi en NaOH-behandelde koringstrooi as vir lusem. Uitvloeitempo van digesta uit die rumen is in beide rasse met behulp van chroomgemerkte koringstrooi bepaal. Hoer uitvloeitempo's is in die Holsteins waargeneem as in die Jerseys, terwyl daaglikse voerinnames ook hoer was (P<O.05) by die Holsteins as by die Jerseys. Daaglikse voerinname, uitgedruk as persentasie van liggaamsmassa, was egter effens hoer (P<O.OI)by die Jerseys as by die Holsteins. Die pH van die rumenvloeistof is op 0, 4, 8, 10 en 12 ure na voeding gemeet. Die enigste betekenisvolle verskil (P<O.OI)in pH tussen die rasse het op 4 ure na voeding voorgekom toe die pH van die rumeninhoud vinniger in die Holsteins as in die Jerseys gedaal het. Die pH in die Holsteins het onder 6.2 gedaal, wat moontlik fibrolitiese mikrobe-aktiwiteit in die rumen kon inhibeer, met 'n gevolglike daling in effektiewe degradeerbaarheid van die ruvoere. Vanaf 10 ure na voeding was die totale vlugtige vetsuurkonsentrasies hoer in die Holsteins, maar geen verskille in asynsuur:propionsuurverhoudings is waargeneem nie. Die gevolgtrekking is gemaak dat Jerseys skynbaar meer doeltreffend is om ruvoere te benut as Holsteins en dat die verskil tussen rasse meer opvallend is vir lae kwaliteit ruvoere as vir hoe kwaliteit ruvoere.

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

One hundred and twenty lactating Holstein cows in mid-lactation were offered diets varying in protein level and degradability at two locations during hot and moderate weather. Treatments were: (1) High protein (19%), high degradability (65%); (2) High protein (19%), medium degradability (40%); (3) Medium protein (15.5%), high degradability (65%); (4) Medium protein (15.5%), medium degradability (40%). Diets were individually fed during hot weather at the University of Arizona Dairy Farm and contained 38.4% alfalfa hay, 12.4% cottonseed hulls, 9.8% whole cottonseed, and 39.4% concentrate (dry matter). Diets were group fed during moderate weather at the Brigham Young University Dairy Farm, Provo, Ut, and contained 31.3% corn silage, 14% alfalfa haylage, 9.4% whole cottonseed and 45.3% concentrate (dry matter). Average daily ambient temperatures were 35.1°C for hot and 26.8°C for moderate weather locations. Fat-corrected milk (3.5%, 2 x milkings) and milk persistency were lower for treatment 1 than other treatments. For the respective treatments during hot weather means were: 23.4, 26.6, 28.5, 28.4 kg/d; 83.2, 91.2, 90.9, 90.3%; and for moderate weather means were: (3 x milkings): 34.7, 31.8, 32.2, 32.4 kg/d; 97.0, 93.4, 92.1, 90.3%. Dry matter intakes during hot weather were 21.5, 21.9, 23.3, and 23.1 kg/d. Respiration rate and rectal temperature during hot weather were: 90.1, 87.9, 90.9, 94.7 counts/min; 39.0, 39.3, 39.3, 39.5°C and for moderate weather: 61.2, 58.2, 55.5, 67.4 counts/min; 38.8, 38.6, 38.7, 38.8°C. Serum T₃,T₄ and cortisol were generally unaffected by treatment, but were depressed during hot weather. Serum glucose was not significantly affected by treatments at either environmental locations. Animals consumed more water with highly degradable protein diets at each location along with consuming more water during thermal stress. These data show that 3.5% fat-corrected milk and milk persistency are significantly affected (P <.01; P <.025) by rations high in protein of high degradability during heat stress.

An experiment involving three feeding trials was conducted to study the effect of substituting chopped wheat straw for alfalfa in diets for lactating dairy cows. The results of these trials have shown that in complete mixed diets or diets containing long alfalfa hay, replacement of half of the alfalfa in rations containing 45% roughage for lactating dairy cows with chopped wheat straw does not adversely affect DM intake or milk yield and increase milk fat percentage. Replacing half of the long alfalfa with chopped alfalfa also apparently improved lactational performance although not as dramatically as that of chopped straw. Ammoniation of wheat straw did not improve the performance response by lactating cows. Inclusion of chopped straw in the diets seemed to enhance the efficiency of milk production. Higher ruminal acetate:propionate ratios and increased digestibility of ether extract resulted from feeding straw. Digestibility of other nutrients were generally either not affected or were depressed by straw feeding. Increasing the chopped wheat straw level to 75% of the roughage resulted in lower DM intake and milk yield and negative body weight gains but higher milk fat levels. It did not appear that maintenance of constant ADF level in a dairy ration regardless of roughage level was the solution to the maintenance of milk fat levels. Thus it has been indicated that under the conditions of this experiment a combination of chopped alfalfa and wheat straw can be used successfully in complete mixed rations for high producing dairy cows. For the most part all productive parameters measured were improved by the addition of straw and by the feeding of complete mixed diets. This was especially true for milk fat which, from a dairyman's viewpoint, is very important because of its impact on milk pricing. It would also have a direct bearing on management by reducing labor costs through elimination of labor intensive handling of long alfalfa. Mechanical handling of complete mixed rations is relatively easier and cheaper.

Two production trials were conducted for 84 d each. The first with 22 Holstein cows in late lactation. The second with 46 Holstein cows in early lactation. Treatments were C (control) and AO (A. oryzae 3g/d). Diets were for production trial 1 a 1:1 forage: concentrate ratio; for trial 2 was 2:3. Milk production in trial 1 was higher (P > .05) in AO fed cows during the first weeks of the trial. In trial two AO cows consistently produced more milk (P < .03). Rectal temperatures during hot weather (over 35°C) were consistently lower in AO fed cows, though not significant (P > .10). Two digestibility trials followed the production trials. For all digestion trials, Cr₂O₃ was used as digesta marker. In trial one AO tended to increase digestibility of DM (P > .10). In trial two digestibilities of DM, NDF and ADF were higher in AO fed cows (P < .05). Three other trials were conducted with mature Holstein cows fitted with ruminal and duodenal cannulae. The first trial tested two levels of forage (1:2 vs 2:1; forage to concentrate) and C vs AO in a 4x4 latin square design. AO increased (P < .05) ADF digestibility in the high concentrate died. No change (P > .10) in rumen pH, concentrations and proportions of VFA, and ammonia concentrations resulted from AO treatments. In the second trial C, AO and SC (Saccharomyces cerevesiae 3 g/d) were compared in a repeated 3x3 latin square design. A 1:2 forage to concentrate diet was fed to six lactating cows. Both AO and SC increased (P < .05) rumen NDF digestibility. The third trial compared C vs AO in a swithchback design with four lactating cows fed a 2:3 forage to concentrate diet. AO increased (P < .05) rumen fiber digestion. AO did not affect rates of passage of corn or alfalfa hay; or the potentially digestible DM of milo, alfalfa hay or wheat straw. AO did increase (P < .05) digestion rate of alfalfa DM. In vitro AO increased DM digestibility. That effect can be reproduced by incorporation of the additive at the time of inoculation.

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