Thesis ((M.Sc. Agric. (Animal Nutrition)) -- University of Pretoria, 2008. / Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (M.S.)--University of Wisconsin. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 132-144).

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Kikuyu over-sown with ryegrass is the most widely used pasture system in the Southern Cape of South Africa. During the winter months the kikuyu component remains dormant and cows are solely dependent on the ryegrass component of the pasture. Ryegrass has a low growth rate (25 - 30 kg DM ha-1 day-1) during the winter and early spring months (June - September), resulting in roughage shortages. There are various strategies that can be adopted to overcome these shortages. Most commonly, lucerne hay is bought in. The cost (R 1800 - R 2400 ton-1), however, is high and all farms do not have the capacity to store hay in large quantities. Significant wastages occur when feeding lucerne in ring feeders or feed troughs. Silage made of surplus grass, maize or cereal crops can also be fed. Many farms do not have the implements required for ensiling and due to financial pressure, most farms are at full capacity and as such no surplus pasture is available for ensiling. The purpose of this study was to determine whether a high fibre concentrate supplement and restricted pasture intake strategy could be followed to overcome roughage shortages during the winter months. Forty eight lactating Jersey cows were blocked according to 4 % fat corrected milk yield (19.1 ± 2.2 kg day-1 (±s.d.)), days in milk (104 ± 62.7) and lactation number (4.4 ± 1.8). Cows within blocks were then randomly allocated to one of the three treatments. Treatments were defined according to the amount of a high fibre concentrate supplement that was allocated as well as the level of pasture allocated: Treatment 1 - Low concentrate treatment (LC) received 4 kg concentrate cow-1 day-1 and 10 kg DM pasture cow-1 day-1; Treatment 2 - Medium concentrate treatment (MC) received 7 kg concentrate cow-1 day-1 and 7 kg DM pasture cow-1 day-1; Treatment 3 - High concentrate treatment (HC) received 10 kg concentrate cow-1 day-1 and 5 kg DM pasture cow-1 day-1. Eight ruminally cannulated Jersey cows were used in the rumen study portion of the trial. These cows were divided into two groups of four and were allocated to the MC and LC treatments. They were used in a cross-over design, where all cows were subjected to both treatments. The metabolisable energy, crude protein and neutral detergent fibre contents of the high fibre concentrate supplement was 10.9 MJ kg-1, 145 g kg-1 and 231 g kg-1, respectively. Cows of the three treatments grazed separately, allowing for the restriction of pasture intake according to treatments specifications. The average daily milk yield and milk fat content of treatments LC, MC and HC was 16.2a, 17.3ab and 18.1b kg day-1 (P < 0.05) and 4.91a, 4.96a and 4.58b % (P < 0.05), respectively. The average stocking rate for treatment LC, MC and HC was 5.07a, 6.07b and 7.64c cows ha-1 respectively. Thirty seven percent of pasture was saved on the HC treatment strategy compared to the LC treatment. Cows gained body weight during the study at a rate of 0.62a, 0.28b and 0.27b kg day-1 (P < 0.05) for the LC, MC and HC treatments, respectively. None of the hourly rumen pH values differed between treatments LC and HC. The rumen pH of cows on treatment LC did, however, spend a longer time below pH 6.0 and pH 5.8 compared to the rumen pH of cows on treatment HC (P < 0.05). The digestibility of dry matter and neutral detergent fibre of pasture of cows on treatment LC and treatment HC at 30 hours of incubation was 82.3 and 73.5 % (P < 0.05) and 43.5 and 39.2 % (P < 0.05), respectively. The results show that winter roughage shortages can be managed by feeding higher levels of a high fibre concentrate supplement and restricting pasture intake, although a decrease in milk fat content can be expected. / AFRIKAANSE OPSOMMING: Kikoejoe, oorgesaai met raaigras, is die mees algemene weidingstelsel in die Suid-Kaap van Suid-Afrika. Tydens die wintermaande is die kikoejoe-komponent dormant en diere is afhanklik van die raaigras-komponent. Raaigras het ‘n lae groeitempo (25 - 30 kg DM ha-1 dag-1) gedurende die winter- en vroeë lentemaande (Junie - September) en dit lei tot ruvoertekorte. Daar is verskeie strategieë wat toegepas kan word om die ruvoertekorte te oorkom. Die gewildste is die aankoop van lusern hooi, alhoewel die prys (R 1800 - R 2400 ton-1) die gebruik daarvan beperk. Boere het ook nie altyd die kapasiteit om groot hoeveelhede lusern te stoor nie en baie hooi word vermors as koeie dit uit hooivoerders en voerbakke vreet. Kuilvoer wat gemaak word van surplus weiding, mielies of graangewasse kan ook gebruik word. Baie boere het nie die implemente om kuilvoer te maak nie en as gevolg van finansiële druk, funksioneer die meeste plase reeds op vol kapasiteit en is daar dus nie altyd voldoende surplus ruvoer waarvan kuilvoer gemaak kan word nie. Die doel van hierdie studie was om te bepaal of ‘n hoë-vesel kragvoer en beperkte weiding-inname gebruik kan word om ruvoertekorte gedurende die wintermaande te oorkom. Agt-en-veertig lakterende Jerseykoeie is geblok volgens 4 % vet-gekorrigeerde melkopbrengs (19.1 ± 2.2 kg dag-1(±s.d.)), dae in melk (104 ± 62.7) en laktasie nommer (4.4 ± 1.8). Koeie binne blokke is vervolgens ewekansig aan een van drie behandelingsgroepe toegeken. Die groepe is gedefinieer volgens die hoeveelheid hoë-vesel kragvoer en weiding wat toegeken is: Behandelingsgroep 1 - Lae-vesel kragvoergroep (LC) het 4 kg kragvoer koei-1 dag-1 en 10 kg DM weiding koei-1 dag-1 ontvang; Behandelingsgroep 2 - Medium-vesel kragvoergroep (MC) het 7 kg kragvoer koei-1 dag-1 en 7 kg DM weiding koei-1 dag-1 ontvang; Behandelingsgroep 3 - Hoë-vesel kragvoergroep (HC) het 10 kg kragvoer koei-1 dag-1 en 5 kg DM weiding koei-1 dag-1 ontvang. Agt rumen gekanuleerde Jerseykoeie was gebruik in die rumen studie gedeelte van die proef. Die koeie was verdeel in twee groepe wat dan aan die LC en HC behandelings groepe toegeken is in ’n omslag ontwerp met twee behandelings en twee periodes. Die metaboliseerbare energie, ruproteïen en neutraal bestande veselinhoud van die hoë-vesel kragvoer was 10.9 MJ kg-1, 145 g kg-1 en 231 g kg-1 onderskeidelik. Die drie behandelingsgroepe het apart gewei, sodat weidingtoekenning beperk kon word en weidinginname bepaal kon word. Die gemiddelde daaglikse melkopbrengs en melk vet % van behandelingsgroepe LC, MC en HC was 16.2a, 17.3ab en 18.1b kg dag-1 (P < 0.05) en 4.92a, 4.96a en 4.58b% (P < 0.05) onderskeidelik. Die gemiddelde veelading van behandelingsgroepe LC, MC en HC was 5.07, 6.07 en 7.64 koeie ha-1 onderskeidelik. Volgens die strategie van die HC behandelingsgroep strategie is sewe-en-dertig persent weiding bespaar, in vergelyking met die LC behandelingsgroep. Koeie in behandelingsgroepe LC, MC en HC het in massa toegeneem gedurende die studie teen ‘n tempo van 0.62, 0.28 en 0.27 kg day-1 (P < 0.05), onderskeidelik. Rumen pH-waardes het nie tussen behandelingsgroepe LC en HC verskil nie. Behandelingsgroep LC se rumen pH was vir ’n langer periode onder pH 6.0 en pH 5.8 as in die geval van behandeling HC. Die verteerbaarheid van droëmateriaal en neutraalbestande vesel van wieding van koeieop behandelingsgroepe LC en HC na 30 ure van inkubasie was 82.3 en 73.5 % (P < 0.05) en 43.5 en 39.2 % (P < 0.05), onderskeidelik. Die resultate dui daarop dat winter ruvoertekorte bestuur kan word deur die voeding van hoër vlakke hoë-vesel kragvoer en die beperking van weidinginname, hoewel ‘n afname in melk vet % verwag kan word.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 44-49). Also available on the World Wide Web.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Monensin was approved in the 1970’s as a feed additive to ruminant diets. Since then, many studies on the effects of Monensin were done. Its mode of action includes the improvement of feed conversion by altering rumen fermentation. This alteration results in a change in the rumen microbial population. Some processes that benefit from the manipulation of rumen microbial population are volatile fatty acid production, peptide degradation and amino acid deamination. The use of ionophores as an antibacterial product in animal feeds were banned by the European union ( EU) in 2006 because of chemical residues found in the edible product making it potentially unhealthy for human consumption and it is also socially unacceptable. Thus, alternative sources need to be identified to help improve the rumen microbial population. Such an alternative could be plant based EO. Oregano (Origanum vulgare) is a natural anti-bacterial compound affecting a variety of gram positive and gram negative bacteria. It has been reported to improve the overall health and production of lactating dairy cows by enhancing rumen fermentation. The aim of this study was to determine the effect of an essential oil extracted from oregano on production and rumen fermentation of Jersey cows grazing ryegrass pasture during spring. Effects were determined on milk yield, milk composition, live weight body condition, rumen pH, Ammonia-nitrogen (NH3-N) and volatile fatty acid (VFA) composition, organic material (OM) and neutral detergent fibre (NDF) digestibility of pasture in the rumen. Fifty four early lactation Jersey cows were blocked, according to days in milk (DIM), 4% fat corrected milk (FCM) and lactation number. Cows within blocks were randomly allocated to one of the three treatments. The three treatments were as follows: Control (CON; maize based concentrate with no feed additives), an ionophore treatment, (MON; a maize based concentrate with monensin provided a daily dose at 300 mg per cow), and an essential oil treatment (EO; a maize based concentrate with oregano extract provided at a daily dose of 1.15 g per cow. Cows received 6 kg of concentrate in the milking parlour and were allocated 10 kg dry matter (DM) of ryegrass pasture, divided into two grazing periods after each milking. Before milking, cows were separated into their respective treatment groups for milking and the consumption of their specific concentrate treatments. Milk yield was recorded on a daily basis. Composite milk samples were collected per cow on a bi-weekly basis. Live weight and body condition score (BCS) were determined before and after the study. Six rumen cannulated cows were used in the rumen study. Two cows were randomly allocated to each of the three treatments in a 3 x 3 Latin square design (three treatments and three periods) thus all the cows were subjected to all three treatments over the experimental period. Ruminal pH, volatile fatty acids (VFA) concentration, ruminal ammonia-nitrogen (NH3-N), and in sacco degradability were determined. The daily average milk yield and milk fat content did not differ among treatments (P > 0.05) and were 20.5, 20.3 and 20.4 kg per cow and 4.5, 4.5 and 4.6 % for cows receiving the CON, MON and EO concentrates respectively. Milk protein and milk lactose content increased (P < 0.05) for the two additive treatments in comparison to control and were 3.39b, 3.55a and 3.60a % for milk protein and 4.50b, 4.80a and 4.80a % for milk lactose where cows received the CON, MON and EO treatments, respectively. Ruminal pH values did not differ among treatments, however, the average overall pH over the 24 hour profile was higher for the two additive treatments. There were no differences in total volatile fatty acid concentrations among the three treatments. With regards to individual VFA, propionate was decreased in the MON treatment when compared to the CON treatment. The ruminal ammonia nitrogen concentration did not differ among treatments. There were no differences in DM and NDF degradability (DMd and NDFd) on the 6 h incubation period but monensin increased the DMd at 30 h incubation and both monensin and oregano increased NDFd after 30 h incubation. To conclude the use of monensin and oregano oil extract have shown to be beneficial with regards to increasing the milk protein and milk lactose content as well as the NDFd. The average overall pH from the pH profile resulted in the two additive treatments being higher when compared to the control treatment. This could be beneficial to rumen fermentation and have a positive effect on the microbial population. As monensin and oregano oil extract showed similar results, oregano oil extract can be considered as an alternative natural feed additive to monensin. / AFRIKAANSE OPSOMMING: Monensin is in die 1970's goedgekeur as 'n voerbymiddel in herkouerdiëte. Sedertdien het navorsing met betrekking tot die invloed van monensin vinnig toegeneem. Die werking van monensin sluit die verbetering van voeromsetting in deur die verbetering van rumenfermentasie. Die verandering in rumenfermentasie het ‘n invloed op die rumenmikrobiese bevolking. Sommige prosesse wat voordeel trek uit die manipulasie van die rumenmikrobiese bevolking is onder andere vlugtige vetsuurproduksie, peptiedafbraak en aminosuurdeaminering. Die gebruik van ionofore as 'n antibakteriese produk in veevoere is gedurende 2006 deur die Europese Unie verbied as gevolg van chemiese residue wat in die eetbare produk gevind is. Die residue maak dit moontlik ongesond vir menslike verbruik en dit is ook nie sosiaal aanvaarbaar nie. Alternatiewe produkte wat help om die rumenmikrobiese bevolking te verbeter en manipuleer moet geïdentifiseer word. Een alternatiewe produk is plantgebasseerde essensiële olies. Origanum (Origanum vulgare) is 'n natuurlike anti-bakteriële produk wat 'n verskeidenheid van gram-positiewe en gram-negatiewe bakterieë in die rumen beïnvloed. Daar is gevind dat die algemene gesondheid en produksie van 'n lakterende melkkoeie verbeter deur die verbetering van rumen fermentasie. Die doel van hierdie studie was om die invloed van 'n essensiele olie-ekstrak uit oreganum op die produksie en rumenfermentasie van Jerseykoeie wat raaigras gedurende die lente bewei, te bepaal. Effekte is ondersoek op melkproduksie, melksamestelling, lewende massa, liggaamskondisie, rumen pH, ammoniak stikstof konsentrasie (NH3-N) en vlugtige vetsuursamestelling (VFA) asook ruminale droeë materiaal (DMd)- en vesel-verteerbaarheid (NDFd) van die weiding. Vier en vyftig Jersey koeie in vroeë laktasie is geblok volgens dae in melk (DIM), 4% vet gekorigeerde melk (VGM) en laktasie nommer. Koeie binne blokke is ewekansig aan een van die drie behandelings toegeken. Die drie behandelings was as volg: Kontrole (CON, mielie-gebaseerde konsentraat met geen voer-bymiddel nie), ‘n ionofoor-behandeling (MON; mielie-gebaseerde konsentraat met monensin teen 300 mg / koei per dag), essensiële olie-behandeling (EO; mielie-gebaseerde konsentraat met oreganum ekstrak teen 1.15 g / koei per dag). Koeie het 3 kg konsentraat in die melkstal ontvang met elke melking en 10 kg droeë material (DM) raaigras-weiding is per koei toegeken. Weidingsessies is verdeel in twee periodes, naamlik na elke melking. Voor melking is die koeie geskei om te verseker dat hulle die regte behandeling in die melkstal ontvang. Melkproduksie is daagliks aangeteken. Saamgestelde melk monsters is tweeweekliks per koei versamel. Lewende massa (LW) en liggaamskondisie (BCS) is aan die begin en teen die einde van die studie bepaal. Ses rumen-gekannuleerde koeie is in die rumen studie gebruik. Twee koeie is toegeken aan elk van die drie behandelings in 'n 3 x 3 Latynse vierkant ontwerp (drie behandelings en drie periodes) en al die koeie het gevolglik al drie behandelings gedurende die eksperimentele periode ontvang. Ruminale pH, VFA konsentrasie, ruminale NH3-N, en in sacco degradeerbaarhede; DMd en NDFd is bepaal. Die daaglikse gemiddelde melkproduksie en melkvetinhoud het nie beduidend tussen behandelings verskil nie (P > 0.05) en was 20.5, 20.3 en 20.4 kg/koei per dag en 4.5, 4.5 en 4.6% vir koeie op die drie behandelings (CON, MON, EO), onderskeidelik. Melk proteïen en melk laktose het aansienlik toegeneem (P < 0.05) vir die twee behandelings met die supplemente in vergelyking met die CON behandeling met waardes van 3.4, 3.6 en 3.6% vir melk proteïen en 4.5, 4.8 en 4.8% vir koeie op die CON, MON en EO behandelings, onderskeidelik. Die rumen pH oor 24 uur het nie verkil tussen die drie behandelings nie en die totale VFA konsentrasie het ook nie verskil nie. Die propionaatkonsentrasie het wel afgeneem op die MON behandeling in vergelyking met die CON. Die rumen NH3-N het nie tussen die drie behandelings verskil nie. Die DMd en NDFd verteerbaarhede van die raaigras in die rumen het nie verskil na ‘n 6 h inkubasieperiode nie. Na 30 h inkubasie het monensin ‘n hoër DM verteerbaarheid getoon en in beide die MON en EO-behandelings het die NDF-verteerbaarheid verhoog wanneer dit vergelyk word met die CON. Om saam te vat; die gebruik van monensin en oregano olie ekstrak het getoon dat dit voordelig kan wees met betrekking tot die verhoging van die melk proteïen en melk laktose inhoud, sowel as die NDFd. Die gemiddelde pH van die pH profiel het gelei tot hoër gemiddeldes vir die twee voerbyvoegsel behandelings in vergelyking met die kontrole behandeling. Dit kan voordelig wees om rumen fermentasie te verbeter en dus ‘n positiewe uitwerking te hê op die mikrobiese bevolking. Monensin en oregano olie ekstrak het soortgelyke resultate getoon en daarom kan oregano olie ekstrak beskou word as 'n alternatiewe natuurlike voerbyvoegsel.

Call number: LD2668 .T4 1957 E95 / Master of Science

The aim of the first study was to determine if barley could replace maize as an energy source in concentrates fed to dairy cows grazing on kikuyu/ryegrass pasture without affecting the milk production, milk composition, or cause metabolic disorders. Sixty Jersey cows, in early to mid lactation were randomly allocated to one of five treatments (n = 12) based on feeding concentrates with different ratios of maize to barley, ranging from 100:0, 75:25, 50:50, 25:75 and 0:100, respectively. Concentrates contained 12 MJ ME kg -1 and 130g CP kg-1 DM and cows were fed 3 kg (as-is) concentrate after each milking for a period of 42 days (14-day adaptation and 28-day measurement). Cows strip-grazed the irrigated kikuyu/ryegrass pastures (15.7 ± 1.8 percent DM; 20.2 ± 4.3 percent CP; 44.7 ± 3.5 percent NDF). Milk weights were recorded daily and milk samples collected weekly and analyzed for milk fat and protein content. Body condition score and live weight were recorded at the start and end of the experimental period. Data of all the studies were subjected to a one-way ANOVA. Daily milk yield, FCM, MUN, milk fat yield, milk fat percent, protein yield, protein percent, live weight change, or body condition score change were not affected by treatment and values were 15.8 kg, 17.2 kg, 14.9 mg dl-1, 0.72 kg, 4.56 percent, 0.59 kg, 3.77 percent, 6.67 kg, and 0.15 BCS; 15.6 kg, 17.4 kg, 15.2 mg dl-1, 0.73 kg, 4.3 percent, 0.57 kg, 3.71 percent, 1.33 kg and 0.04 BCS; 17.2 kg, 17.9 kg, 15.2 mg dl-1, 0.74 kg, 4.36 percent, 0.63 kg, 3.71 percent, 0.33 kg and 0.08 BCS; 15.6 kg, 16.4 kg, 15.5 mg dl-1, 0.67 kg, 4.33 percent, 0.60 kg, 3.83 percent, -1.46 kg and 0.11 BCS; and 15.0 kg, 16.0 kg, 15.5 mg dl-1, 0.67 kg, 4.57 percent, 0.57 kg, 3.85 percent, 8.86 kg, and 0.05 BCS, respectively for the cows fed 100:0, 75:25, 50:50, 25:75 and 0:100 maize to barley ratio concentrate. According to these results, barley can replace maize without significantly affecting the milk production or milk composition. None of the cows presented any visible symptoms of acidosis. As it was clear from the results in the first study that maize could replace barley the aim of study 2A was therefore focused on determining the effect of feeding different levels of such a barley-based (2.4, 4.8 or 7.2 kg cow-1day-1) concentrate, on milk production, milk composition and live weight change of Jersey cows on kikuyu/ryegrass pasture (23.1 ± 2.95 percent DM, 11.1 ± 0.11 percent CP, 60.8 ± 0.58 percent NDF). Forty-five Jersey cows (early- to mid lactation), were randomly allocated to one of three treatments (n = 15) involving different levels of concentrate (12 MJ ME and 130g CP kg-1 DM) feeding for a period of 42 days (14-day adaptation and 28-day measurement). Milk weights were also recorded daily, and milk samples collected weekly, and analyzed for milk fat and protein. Body condition score and live weight were recorded at the start and end of the experimental period. The results of this study indicated that increasing the concentrate level from 2.4 to 4.8 and 7.2kg cow-1day-1 did not increase the milk yield (14.0 kg, 15.2 kg, 14.4 kg; P = 0.19). The FCM production increased from 15.8 to 17.5kg (P = 0.04) as the concentrate level increased from 2.4 to 4.8kg cow-1day-1. Increasing the concentrate from 4.8 to 7.2kg cow-1day-1 did not result in a significant increase in FCM. The milk protein percent increased significantly from 3.4 - 3.6 percent when the concentrate feeding level was increased from 2.4 to 7.2kg cow-1day-1. The MUN levels were 17.09 mg dl-1, 16.03 5 mg dl-1, and 16.36 mg dl-1 for the 2.4, 4.8 and 7.2kg cow-1day-1 concentrate levels, respectively. This is well within the recommended MUN levels (12 – 18 mg dl-1) indicating that sufficient protein was fed to cows. Increasing the concentrate level from 4.8 to 7.2 kg cow-1day-1 did not increase production, probably due to a higher pasture substitution rate. Supplementing large quantities of rapidly fermentable grains, such as barley, can suppress rumen pH and may have a negative effect on the rate and extent of fibre digestion in the rumen. Therefore the aim of study 2B was not only to determine the effect of feeding different levels of a barley-based concentrate, on milk production, milk composition and live weight change, but was also to determine the effect of a low (4.8 kg cow-1day-1) versus a high (7.2 kg cow-1day-1) level of barley-based concentrate supplementation on ruminal DM and NDF degradability of Westerworld ryegrass sampled from the pastures that these cows were grazing on. Sixty Jersey cows (early- to mid lactation), were randomly allocated to one of three treatments (n = 20) involving different levels of concentrate feeding. Concentrate (12 MJ ME, 130g CP kg-1 DM) was fed at 2.4, 4.8 or 7.2 kg cow-1day-1 for a period of 74 days (14-day adaptation and 60-day measurement). These cows stripgrazed irrigated kikuyu/ryegrass pastures (14.7 ± 4.37 percent DM, 25.1 ± 1.53 percent CP, and 44.4 ± 2.58 percent NDF) at a daily pasture allocation of 10 kg DM cow-1. Milk weights were recorded daily and milk samples collected weekly and analyzed for milk fat and protein. Body condition score and live weight were recorded at the start and end of the experimental period. Twelve Jersey cows, fitted with ruminal cannulae, were randomly allocated to two of the three treatments in the production study and received either 2.4 or 7.2 kg cow-1 day-1, of the same barley-based concentrate, in a two-period crossover design. These cows strip-grazed the same irrigated kikuyu/ryegrass pastures as the sixty cows in the production study. Each period consisted of 21 days for adaptation and seven days for data collection. Rumen liquor samples were collected every 4 hours within a 24-hour cycle and repeated once. Rumen pH was measured immediately, recorded, and the supernatant fluid preserved and frozen, pending VFA analysis. The in situ nylon bag technique was used to determine DM and NDF degradation and dried samples of Westerworld ryegrass pasture were incubated for 0, 4, 8, 12, 20, 30, 48, 72 and 96 hours. The data were fitted in the non-linear model p = a + b (1-exp-ct) (Ørskov & McDonald, 1979). Daily milk production, fat corrected milk, milk fat yield and milk fat percent were not affected by treatment and values were 17.3 kg, 18.4 kg, 0.76 kg and 4.42 percent; 19.0 kg, 20.0 kg, 0.82 kg and 4.35 percent; and 18.1 kg, 19.1 kg, 0.79 kg and 4.37 percent for the 2.4, 4.8 and 7.2 kg cow-1 day-1 concentrate treatments, respectively. Milk protein percentage of cows on the 7.2 kg concentrate cow-1 day-1 was significantly higher than that of cows on 4.2 kg concentrate cow-1 day-1 feeding level. Live weight increased significantly as the level of concentrate feeding increased and values were 17.9 kg; and 28.9 kg on the 2.4 and 7.2kg concentrate treatment, respectively. There was a significant increase in the live weight of cows that were fed 7.2 kg cow-1 day-1 (as-is) in comparison to those cows that were fed 2.4 kg concentrate cow-1 day-1 (as-is). This may have resulted from more nutrients being partitioned to live weight gain rather than milk production. No further response in milk production was observed when concentrate daily feeding was increased from 4.8 to 7.2 kg cow-1 day-1. It is postulated that the higher concentrate allowance resulted in a higher substitution rate and lower DMI intake from pasture. 6 There was no significant decline in the rumen pH (6.2 ± 0.4 and 6.2 ± 0.5) when the concentrate level was increased from 2.4 to 7.2 kg cow-1 day-1 (as-is). The total VFA (118.1 ± 45.9 and 139.4 ± 45.6 mmol L-1) and isovalerate (0.009 ± 0.07 and 0.248 ± 0.52 mmol L-1) increased significantly when the concentrate was increased from 2.4 to 7.2 kg cow-1day-1. No other rumen parameters were affected by treatment. Ruminal DM and NDF degradability of the Kikuyu/ryegrass pature were not affected by the level of concentrate supplementation. An increase in the concentrate level from 2.4 to 7.2 kg cow-1day-1 did not reduce degradability of either DM (94.67 ± 5.97, 94.49 ± 5.09; P = 0.919) or NDF (92.15 ± 8.69, 94.4 ± 11.73; P = 0.451), respectively. Results of rumen parameters and PD values were within the range reported by Bargo et al., (2003), viz. pH 5.76 – 6.29, NH3-N concentration 8.7 – 32.2 mg dl-1, total VFA concentration 90.3 - 151.4 mmol L-1 and PD values 89.5 – 93.5 % reported by Bargo et al. (2003). According to these authors, there is no simple relationship between any amount of the concentrate supplemented, and the ruminal pH and concentrate feeding only affects the in situ ruminal digestion of pasture when it is fed, at quantities higher than 8 kg DM cow-1day-1 (Bargo et al., 2003).

Cryopreservation of in vivo derived Jersey bovine embryos have resulted in a 10% lower pregnancy rate compared to other dairy breeds. Poor embryo survival after cryopreservation has been partially attributed to the high lipid content of Jersey embryos. In vitro-produced (IVP) bovine embryos have darker cytoplasm than their in vivo-derived counterparts because of higher lipid accumulation. High lipid accumulation is associated with impaired embryo quality. Forskolin is an adenylate cyclase activator that regulates cAMP levels in cells and has been shown to induce lipolysis in IVP embryos. L-carnitine is required for transport of fatty acids from the intermembrane space of the mitochondria into the mitochondrial matrix to support the process of β-oxidation, and enhances ATP production. We hypothesized that the lipid content of in vivo-produced and IVP Jersey embryos is higher than respective Holstein embryos and that forskolin + L-carnitine would reduce lipid content of IVP embryos and vitrification with embryo collapse would improve the cryosurvival of Jersey IVP embryos. The objectives of this experiment were (1) to analyze lipid content of in vivo and IVP Jersey and Holstein cattle embryos, (2) to evaluate the effect of forskolin + L-carnitine added to IVP culture media, and (3) evaluate Jersey IVP survival rates after three cryopreservation procedures. The factorial experimental design for objectives one and two used two breeds (Holstein and Jersey) and three embryo production methods (in vivo, IVP, and IVP + forsk/L-C). In vivo produced embryos (n = 27 blastocysts) were collected from superstimulated donors by routine procedures 7.5 days after AI. IVP embryos (n = 259 blastocysts) were produced by standard procedures; briefly, oocytes were aspirated from 2- to 8-mm follicles from slaughterhouse ovaries and matured for 24 h in SMM medium (BoviPro, MOFA Global, Verona, WI, USA). Matured oocytes were fertilized using semen from two different bulls for each breed, and embryos were cultured in BBH7 medium (BoviPro, MOFA Global) alone or with the addition of 1.5mM L-carnitine during maturation and embryo culture with forskolin (10 µM) added at Day 5 of culture at 38.5°C in 5% O2, 5% CO2, and 90% N2. The lipid content of embryos was quantified by staining Day 7 blastocysts with 1 μg mL–1 Nile red dye (580–596 nm), after which a digital photograph of the equatorial part of the embryo was taken at 40×, and fluorescence intensity (FI) was measured with Image Pro software. Data was analyzed by ANOVA, and means were compared using Tukey’s HSD. For the third objective, grade 1 Jersey IVP blastocysts (n=356) were divided into six treatments using a 2x3 factorial design comparing intact (IB) vs collapsed blastocoele (CB) and three cryopreservation methods: slow freezing (SF) vs vitrification using open pulled straws (OPS) or cryotop (CT). Slow freezing embryos were equilibrated in 0.7 M glycerol and 0.1 M galactose in holding media for 10 min, held for 10 min at -6°C, seeded after 5 min, decreased to -32 °C at 0.5 °C /min, held at -32°C for 5 min, and finally plunged into liquid nitrogen. Vitrified embryos were equilibrated in 1.5 M ethylene glycol (EG) for 5 min, exposed to 7 M EG + 0.6 M galactose for 30 s while loaded into OPS or placed onto CT, then immediately plunged into liquid nitrogen. SF embryos were thawed in air for 10 s and placed in a water bath at 37°C for 45 s. Vitrified embryos were warmed directly into holding medium at 37°C supplemented with 1.0 M, 0.5 M and 0.25 M galactose for 3 minutes each. Subsequently, embryos were cultured in BBH7 and re-expansion rates were assessed at 24 and 48h post warming and data was evaluated by GLIMX. For objective 1, Jersey and Holstein IVP embryos had higher lipid content than Holstein in vivo-produced embryos (P < 0.05), but were not different than Jersey in vivo-derived embryos (P > 0.1). Forskolin + L-carnitine lowered the lipid content (P < 0.05) of both IVP Jersey and Holstein embryos and was not different (P > 0.1) than in vivo-produced embryos. For experiment 2, re-expansion rates were higher for CT, than OPS, and SF (85 vs. 66 vs. 72% ± 0.4, respectively; p<0.05). Main effect means for re-expansion were higher for CB than IB (79 vs 68% ± 0.3; p<0.05). In conclusion, IVP embryos have higher lipid accumulation over Holstein in vivo embryos. Addition of forskolin and L-carnitine to embryo culture media has the potential to lower embryo lipid accumulation and possibly improve embryo viability and cryotolerance of IVP embryos. The CT method and collapsing the blastocoele prior to cryopreservation resulted in higher blastocyst survival rate. Further studies including transfer of embryos to recipients are necessary to corroborate these results.