Thesis (Ph. D.) -- Lincoln University, 2010. / Also available via the World Wide Web.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The aim of the study was to determine the effect of increasing levels of Maize silage in finishing diets for Merino lambs on their feed intake, production performance, feed conversion ratio, digestibility and meat quality. Concerns exist regarding the intake of high moisture and fibre containing silage in sheep due to the physical fill effect thereof. To determine the efficiency of silage as feed ingredient for sheep, maize was cut at 27% dry matter (DM), compacted into 220 litre plastic drums, sealed and left to ferment for 60 days. The silage produced was analysed for fermentation end products and the nutritive value determined. The silage produced had an optimum pH, starch and water soluble carbohydrate (WSC) content. The crude protein (CP) content (112.2 g/kg DM) was higher than expected. Four diets containing, on a dry matter (DM) basis either, 0, 20, 50 or 70% maize silage was formulated on an iso-nutrient basis with exception of neutral detergent fibre (NDF). The aim was to establish the effect of increasing levels of silage on animal production with regard to dry matter intake, growth, digestibility and meat quality. Diets were formulated on an iso-nutrient basis to match the 70% silage diet and therefore had relatively low specifications due to the high inclusion of silage from the 70% silage diet. A growth study and an in vivo and in vitro digestibility study were conducted to determine the effect of the different diets on feedlot sheep production. Meat quality was also determined to establish whether the experimental diets had an effect on meat quality. Forty lambs in a completely randomised block design, with four treatments, were used in a 60-day finishing study. The dry matter intake (DMI) of lambs decreased as silage inclusion increased above the 20% silage inclusion level. At the 20% inclusion rate, the feed intake of the animals was stimulated. This resulted in significant differences found between the cumulative intake of the low and the high silage diets. Feed conversion ratio (FCR) was poorer, however, for the control and 20% silage diets. The poor FCR most likely was related to the quality of the feed ingredients used in the formulation of the control feed and the concentrate in the 20% silage diet rather than the silage itself. Significant differences were also found in the dressing percentage of the slaughtered animals where the 20 and 50% silage diets had a higher dressing percentage than the control and 70% silage diets. It was concluded that silage can be successfully incorporated into sheep diets, especially at low levels where its inclusion stimulates intake. Eight animals per group were used in an in vivo digestibility study to determine the apparent digestibility of the experimental diets. Feed, faeces and urine samples collected during the trial period were analysed for the respective nutrients. The 20% diet, even though having the best overall apparent digestibility, did not result in better production responses. Lambs on the 20% silage diet had the highest daily DM intake, which resulted in them having the highest energy intake. There were no differences in total energy excreted between the silage-based diets. This resulted in the 20% silage diet also having the best energy retention. Nitrogen retention was the highest for the control and 20% silage diets. This can be ascribed to the low quality of the concentrate part of the diet. The 20% silage diet, as previously stated, had the highest apparent DM and organic matter (OM) digestibility, while the control diet showed the lowest overall nutrient digestibility. The low nutrient digestibility of the control diet can be ascribed to the relatively poor quality ingredients used. There were no differences in the crude protein (CP) digestibility between the control and the 20% diet. Both proved to be higher than the CP digestibility of the 50 and 70% silage diet. As the neutral detergent insoluble nitrogen (NDIN) was higher for the 50 and 70% diets, this observation was not surprising. Fibre content of the silage-based diets increased as the inclusion level of the silage increased, which resulted in a decrease in overall fibre digestion. Three cannulated sheep were adapted on each experimental diet for two weeks before rumen fluid was collected for the in vitro digestibility study. No differences between the silage based diets were found for in vitro true digestibility (IVTD). The IVTD of the 20, 50 and 70% diets were higher, however, than the IVTD of the control diet confirming earlier observations on the choice of ingredients used in the control diet to formulate iso-nutrient diets. Degradability coefficients were determined for the DM and NDF fractions of the different experimental diets and fitted to the non-linear model; p = a + b (1 – e-ct). The amount of DM that disappeared in a certain time (t) is represented by p. Constant a represents the fraction that was rapidly soluble, b represents the potential degradable fraction and c is the rate at which b was degraded. There were no differences between experimental diets for the rapidly soluble fraction. The silage-based diets had a higher potential degradable fraction (b) but did not differ in the degradability rate (c) from the control diet. Silage-based diets had higher overall effective degradability than the control but did not differ between one another. Constant a was not determined for NDF degradability since the NDF fraction did not have a rapidly soluble fraction. The control diet had the lowest potential degradable NDF fraction with the rate also being lower than the silage based diets. Effective NDF degradability was highest for the 50% silage diet. Lambs used in the finishing study were slaughtered and meat samples taken for meat quality tests. The pH, colour, drip loss, cooking loss, shear force and fatty acid composition were determined on the Longissimus dorsi samples collected at Roelcor (Malmesbury, Western Cape, South Africa). Proximate analysis was also conducted on the meat samples. The experimental diets did not have a significant effect on the proximate chemical composition of the meat. Colour differences were found; however no clear pattern could be established. There were no differences in fatty acid composition. It can be concluded that up to 70% maize silage can be included in the finishing diets of Merino lambs with no adverse effects on the meat quality. The study showed that 20% maize silage can be included in the finishing diets of Merino lambs without negatively affecting intake, production, digestibility or meat quality. Future research is needed to optimise the 20% silage diet, however, and to again look at the effect that it will have on animal production, including the effect thereof on total methane emissions. / AFRIKAANSE OPSOMMING: Die doel van die studie was om te bepaal of mielie kuilvoer doeltreffend gebruik kan word as ‘n komponent in die afronding van Merino lammers. Gedurende die proses is mielies gesny teen 27% droë materiaal (DM), en saamgepers in 220 liter plastiek dromme. Dit is toegelaat om te fermenter vir 60 dae. Die kuilvoer wat daaruit geproduseer is, is geanaliseer vir fermentasie eindprodukte, en die voedingstofwaarde is bepaal. Vier diëte met onderskeidelik 0 (kontrole), 20, 50 en 70% kuilvoer is geformuleer op ‘n iso-nutriëntbasis met die uitsondering van vesel (NDF). ‘n Groeistudie, tesame met ‘n in vivo en in vitro verteerbaarheidstudie is uitgevoer om die effek van die verskillende diëte op diere produksie te toets. Vleiskwaliteit toetse is ook gedoen om te kyk of die verskillende diëte ‘n effek op vleiskwaliteit het. Veertig lammers, in ‘n ewekeurige blokontwerp, is gebruik in ‘n 60 dae afrondingstudie. Dit is opgemerk dat die DM inname (DMI) afgeneem het soos die kuilvoer insluiting bo die 20% vlak toegneem het. By die 20% insluitingskoers, is voerinname by die diere gestimuleer. Dit het veroorsaak dat beduidende verskille gevind is tussen die kumulatiewe inname van die lae en die hoë kuilvoer diëte. Die voeromsetkoers (VOK) was egter hoër vir die kontrole en 20% kuilvoer diëte. Beduidende verskille is ook gevind in die uitslagpersentasie van die diere, waar die 20% en 50% kuilvoer diëte ‘n hoër uitslagpersentasie as die kontrole en 70% kuilvoer diëte gehad het. Agt diere is per groep gebruik in ‘n in vivo verteerbaarheidstudie om die skynbare verteerbaarheid van die eksperimentele diëte te toets. Voer, feses en urien monsters is gedurende die proefperiode ingesamel en geanaliseer. Die 20% kuilvoer dieet het die hoogste DM en organiese materiaal skynbare verteerbaarheid teenoor die kontrole diet wat die laagste gehad het. Daar was geen verskille in die ru- proteien (RP) verteerbaarheid van die kontrole en 20% kuilvoer diet nie. Beide was hoër as die RP verteerbaarheid van die 50% en 70% kuilvoer dieet. Die veselinhoud van die kuilvoergebasseerde diëte het toegeneem soos die insluitingsvlak van die kuilvoer toegeneem het, wat ‘n afname in veselvertering veroorsaak het. Lammers op die 20% kuilvoer dieet het die hoogste daaglikse DM inname gehad, wat die hoogste energie inname tot gevolg gehad het. Daar was geen verskille in die totale energie inname van die kuilvoergebasseerde diëte – dit het veroorsaak dat die 20% kuilvoer dieet ook die beste energie retensie gehad het. Stikstof retensie was die hoogste vir die kontrole en 20% kuilvoer dieet. Drie gekannuleerde skape is vir twee weke op elke eksperimentele dieet aangepas voordat rumenvloeistof ingesamel is vir die in vitro verteerbaarheidstudie. Geen verskille is gevind vir die in vitro ware verteerbaarheid (IVWV) tussen die kuilvoergebasseerde diëte nie. Hulle was egter hoër as die IVWV van die kontrole dieet. Degradeerbaarheid koëffisiënte is bepaal vir die DM en NDF fraksies van die verskillende eksperimentele diëte en is gepas in die model p = a + b (1 – e-ct). Die hoeveelheid DM wat verdwyn het binne ‘n sekere tyd (t) word voorgestel deur p. Die konstante a verteenwoordig die fraksie wat vinnig oplosbaar is, b verteenwoordig die potensieel degradeerbare fraksie en c is die koers waarteen b gedegradeer is. Konstante a is nie bepaal vir die NDF degradeerbaarheid nie, aangesien die NDF fraksie nie ‘n vinnig oplosbare fraksie gehad het nie. Daar was geen verskille in die vinnig oplosbare fraksie tussen eksperimentele diete nie. Kuilvoer gebasseerde diete het ‘n hoër potensieel degradeerbare fraksie gehad, maar daar was geen verskille in koers van degradering nie. Die kuilvoergebasseerde diëte het ‘n hoër DM effektiewe degradeerbaarheid as die kontrole dieet. Effektiewe NDF degradeerbaarheid was die hoogste vir die 50% kuilvoer dieet. Lammers in die studie gebruik is geslag en vleismonsters is geneem vir vleiskwaliteit toetse, insluitende pH, kleur, drupverlies, kookverlies en taaiheid. Proksimale analise is ook uitgevoer op die vleismonsters. Die eksperimentele diëte het nie ‘n beduidende effek op die proksimale chemiese samestelling van die vleis gehad nie. Kleur verskille is wel gevind, maar geen duidelike patroon kon vasgestel word nie. Daar was geen verskille in die vetsuur samestelling nie. Daar kan dus tot die gevolgtrekking gekom word dat mielie kuilvoer ingesluit kan word in die afrondingsdiëte van Merino lammers, tot by 70%, sonder enige negatiewe effekte op die vleiskwaliteit. Daar is tot die gevolgtrekking gekom dat mielie kuilvoer suksesvol geïnkorporeer kan word in skaapdiëte, veral teen lae vlakke (20%) waar die gebruik nie net inname stimuleer nie, maar ook geen negatiewe effekte het op produksie en verteerbaarheid nie. / Dr. Francois van de Vyver, Cape Wools and NWGA for providing funding in the form of post graduate bursaries

The aim of the present study was to investigate the bioavailability of selenium (Se) from milled soya beans, a plant protein, to lambs after various degrees of heat treatment. Thirty Dohne Merino lambs (ca. 25 kg live weight, 4 months old) were allocated randomly within sex and weight groups into three treatment groups. During the experimental period, they were fed a diet consisting of a large proportion of milled soya beans as their main source of Se and other feeds low in Se to balance the diet. Blood was drawn during this period and analysed for Se and glutathione peroxidase (GSH-Px) activity. Chemical and Se analyses were performed on the feed and soya bean samples as well as on the organs, wool and rumen fluid of the lambs. Although the ADIN concentration of the soya beans increased with increasing heat treatments, more heat damage could have been inflicted on it to differentiate the different soya bean fractions in comparison to each other. On average, the in sacco disappearance of the dry matter (DM), crude protein (CP) and Se was higher for the unprocessed soya beans compared to the two processed soya beans fractions. As a result, the lambs receiving the unprocessed soya beans (control group- C-group) had a significant higher rumen bacterial Se concentration than the lambs receiving the heat¬treated soya beans. Despite this higher concentration, the liver Se concentration of this group was statistically significantly lower compared to the two heat-treated groups. This can be interpreted that the heat processing of the soya beans enhanced its Se fraction to be taken up by the liver. However, those differences were biologically not significant. The average liver Se concentration between the lambs receiving the over- ¬processed- (a-group) and those receiving the ideal treated soya beans (I-group), did not differ, indicating that the excessive heat treatment did not influence the amount of Se reaching the lower digestive tract of the a-group. Although the Se concentration of the heart muscle of the a-group was statistically significantly lower than for the I-and C-groups, those differences biologically were not significant. Despite an increase in the erythrocyte GSH-Px activity over the duration of the trial in all three the treatment groups, no significant differences between the three treatment groups were observed at any stage. It is concluded from this study that the heat treatment of soya beans has not influenced the incorporation and the bioavailability of its Se fraction to any significant degree. / Dissertation (MSc (Agriculturae))--University of Pretoria, 2006. / Animal and Wildlife Sciences / unrestricted

[Truncated abstract] In Australia, there is pressure to reduce the amount of methane produced by ruminant livestock because they are the single largest source of methane emitted from anthropogenic sources, accounting for 70.7% of agricultural methane emissions. In addition, methane production represents a loss of gross energy intake to the animal. The organisms that are responsible for methane production in the animal gut are a distinct group of Archaea called methanogens. Methanogens occupy three different niches within the rumen. Some live freely in the rumen digesta (planktonic), others are attached to the outer surface of the rumen ciliates (ectosymbiotic), and some reside within the ciliates (endosymbiotic). The types and number of methanogens, as well as rumen ciliates and their symbiotic interactions, influence the amount of methane produced from the rumen. These factors in turn are affected by many factors, including diet and ruminal retention time. In this thesis, I tested the general hypothesis that increasing the amount of grain in the diet and reducing the retention time would affect the abundance and diversity of methanogens in their different niches, including their association with ruminal ciliates. Twenty-four fistulated sheep were used in a complete factorial design with the sheep randomly divided into four groups. ... The change in DGGE banding patterns and Shannon indices when sheep were fed grain indicated that the types of methanogens changed when sheep were fed low and high grain diets, but their diversity did not. In contrast, the diversity of rumen ciliates decreased when sheep were fed a high grain diet. A total of 18 bands from the DGGE analysis of the ciliates were sequenced. All except one, which was 98% similar to Cycloposthium sp. not found previously in the rumen, matched the sequences for previously identified rumen ciliates. Some of the rumen ciliates identified were not present in sheep fed the high grain diet. On a high grain diet, methanogens associate endosymbiotically with rumen ciliates to get better access to hydrogen. It appears that the association between methanogens and rumen ciliates is dictated by the availability of hydrogen in the rumen and not the generic composition of the ciliate population. Furthermore, endosymbiotic methanogens appear to produce less methane than methanogens in other niches. The pot scrubbers did not change ruminal retention time but they did reduce the acetate/propionate measurements observed in sheep on the high grain treatment. The reason why pot scrubbers had this effect remains unknown, but it is interesting to consider that some physical interaction has occurred between the pot scrubbers, the grain and the sheep that has improved the fermentation parameters in sheep fed a high grain diet. The results from this study have advanced our understanding of the interaction between methanogens and ruminal ciliates, and methanogenesis in the rumen in response to dietary changes and mechanical challenges. Extending this work to look more specifically at the species of methanogens that are most closely linked to high methane production and how they interact with the ruminal ciliates will be critical for manipulating enteric greenhouse gas emissions.