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Ruminant livestock maintain an important role in meeting the nutrient requirements of the global population through their unique ability to convert plant fiber into human-edible meat and milk products. Volatile fatty acids (VFA) produced by rumen microbial fermentation of feed substrates represent around 70% of the ruminant animal's metabolic energy supply. Rumen fermentation profiles may directly impact productivity because the types of VFA produced are utilized at differing efficiencies by the animal. Improving our understanding of factors that control these fermentative outcomes would therefore aid in optimizing the productive efficiency of ruminant livestock. Improvements in animal efficiency are now more important than ever as the livestock industry must adapt to continue meeting the nutritional needs of a growing global population in the context of increased resource restrictions and requirements to lower the environmental impact of production. The relationship between diet and VFA ultimately supplied to the animal is complex and poorly understood due to the influence of numerous nutritional, biochemical, and microbial variables. The central aim of this body of work was therefore to explore and characterize how fermentation dynamics, rumen environmental characteristics, and the rumen microbiome behave in response to variations in the supply of fermentative substrate. The objective of our first experiment was to describe a novel in vitro laboratory technique to rank livestock feeds based on their starch degradability. This experiment also compared the starch degradation rates estimated by the in vitro method to the rates estimated by a traditional in situ method using sheep. A relationship between the degradation rates determined by these two procedures was observed, but only when feed nutrient content was accounted for. While this in vitro approach may not be able to reflect actual ruminal starch degradation rates, it holds potential as a useful laboratory technique for assessing relative differences in starch degradability between various feeds. Our second experiment aimed to measure changes in VFA dynamics, rumen environmental characteristics, and rumen epithelial gene expression levels in response to dietary sources of fiber and protein designed to differ in their rumen availabilities. Conducted in sheep, this study utilized beet pulp and timothy hay as the more and less available fiber source treatments, respectively, and soybean meal and heat-treated soybean meal as the more and less available protein source treatments, respectively. Results indicated that rumen environmental parameters and epithelial gene expression levels were not significantly altered by treatment. However, numerous shifts in response to both protein and fiber treatments were observed in fermentation dynamics, especially in interconversions of VFA. The objective of the third investigation was to assess whether the rumen microbiome can serve as an accurate predictor of beef and dairy cattle performance measurements and compare its predictive ability to that of diet explanatory variables. The available literature was assembled into a meta-analysis and models predicting dry matter intake, feed efficiency, average daily gain, and milk yield were derived using microbial and diet explanatory variables. Comparison of model quality revealed that the microbiome-based predictions may have comparable accuracy to diet-based predictions and that microbial variables may be used in combination with diet to improve predictions. In our fourth experiment, the objective was to investigate rumen microbial responses to the fiber and protein diet treatments detailed in Experiment 2. Responses of interest included relative abundances of bacterial populations at three taxonomic levels (phylum, family, and genus) in addition to estimations of community richness and diversity. Numerous population shifts were observed in response to fiber treatment. Prominent fibrolytic population abundances as well as richness and diversity estimations were found to be greater with timothy hay treatment and lower with beet pulp whereas pectin degraders increased in abundance on beet pulp. Microbial responses associated with protein treatment were not as numerous but appeared to reflect taxa with roles in protein metabolism. These four investigations revealed that significant changes can occur in VFA fermentation and rumen microbial populations when sources of nutrient substrates provided in a ruminant animal's diet are altered and that a new approach may be useful in investigating degradation of another important substrate for fermentation (starch) in a laboratory setting. Our findings also determined that animal performance can be predicted to a certain extent by rumen microbial characteristics. Collectively, these investigations offer an improved understanding of factors that influence the process of converting feed to energy sources in the ruminant animal.

Hellebores (Helleborus spp.) are winter-­‐flowering ornamental plants that are difficult to propagate in tissue culture. To improve the performance of hellebores during micropropagation, preliminary tests were done to standardize temperature and light quality. The effects of growth hormone type and concentration on plant multiplication were also assessed. Performance remained low, and plantlets often displayed visible contamination.

Two groups of 10 Border Leicester ram lambs ( LGR lambs: 10 weeks old; 22.7 ±0.59 kgLW) were grazed on irrigated and N fertilised pastures of Grasslands Puna chicory (Puna) and Wana cocksfoot (Wana) over a six week period. Both pastures were maintained as vegetative, pure species swards and offered in weekly subdivisions at high herbage allowances of 12.5 to 15 kgDM/lamb/day. Liveweight of the lambs was recorded weekly and pasture intake was estimated in week 3 from dilution of two faecal markers, chromium oxide (Cr₂O₃) and ytterbium (Vb) acetate, and in vitro digestibility measured from oesophageal extrusa samples. Another two groups of 6 lambs each, each lamb fitted with rumen and duodenal cannulae (SOD lambs) were co-grazed on Puna and Wana from weeks 4 to 5 to measure digesta flow and nutrient supply at the duodenum. Chromium ethylene diamine tetra-acetic acid (Cr-EDT A) and Yb acetate were used as solute and particulate phase digesta markers, respectively (Faichney, 1975; Siddons et al., 1985). The digesta markers were infused continuously into the rumen using portable battery powered peristaltic pumps and sampled following the procedure of Faichney (1975, 1980) to measure digesta passage and site of nutrient digestion. LWG (g/d) of LGR lambs grazing Puna (273 ± 24.3) was significantly greater (p 10% age units lower compared to the most edible parts (leaves and stem above 50 cm: 83% OMD) of Puna. The original Puna data (viz. DOMI) was revised by correcting for the low in vitro digestibility of the oesophageal extrusa sample. The difference between the revised DOMI of Puna (680 g/d) and Wana (716 g/d) was less than 10%, and the former was equivalent to an ME intake of 10.6 MJ/d, acceptable for good lamb growth rate (Cruickshank, 1986). Notwithstanding possible error of the original intake estimate, data on digestion characteristics and site of digestion suggested a higher post-ruminal digestion of Puna than Wana, which is consistent with high growth rate in lambs grazing pasture (Cruickshank, 1986), Digestible OM apparently digested in the rumen (DOMADR) for Puna was 0.51 ±0.018, significantly lower (p

Intake and nutrient supply were measured in early weaned lambs grazing pure species swards of Rere lucerne (Medicago sativa, L), Huia white clover (Trifolium repens, C), Ruanui perennial ryegrass (Lolium perenne, R) and Matua prairie grass (Bromus catharticus, P). A study of the factors regulating intake was undertaken with these young lambs and this area was studied in greater detail with adult sheep, which permitted repeated measurement of rumen digesta content. A preliminary experiment, conducted indoors, studied the effect of lamb age and cannulation on the development of rumen function in lambs weaned at 6 weeks of age and offered clover hay ad libitum. Cannulation did not affect intake (g.kgW⁻¹), in vivo digestibility or marker retention time in the rumen. However, liveweight gain was 22% lower in cannulated lambs than in intact lambs, but this may have been due, at least partly, to differences in weaning weight, as liveweight gain per kg digestible organic matter intake was similar for both groups. Intake (g.kgW⁻¹) increased rapidly from weaning until approximately 10 weeks of age and remained constant, at 36-38gDM.kgW⁻¹, thereafter. With increasing age there appeared to be a reduction in the proportion of apparently digestible organic matter intake (DOMI) and digestible neutral detergent fibre (NDF) intake apparently digested in the rumen, but this affect was largely explained by changes in the intake of cannulated lambs between the 4 periods of nutrient supply measurement. In a later experiment lambs weaned at 6 weeks of age grazed single species swards. Growth rate, intake and nutrient supply were measured during the subsequent 6 week period. Liveweight gain was higher in lambs grazing legumes (321 and 308 g.d⁻¹ for C and L respectively) than for lambs grazing grasses (230 and 227 g.d⁻¹ for P and R respectively). Nutrient supply was measured at 8 and 12 weeks of age. There was no difference in intake (g.kgW⁻¹) or site of nutrient digestion between these periods. The higher growth rate of lambs grazing legumes was associated with a 36% higher DOMI (g.kgW⁻¹) and a 33% higher NAN flow at the duodenum (g.kgW⁻¹). The proportion of DOMI apparently digested in the rumen was similar for all pasture species (average, 0.56), although less digestible NDF was digested in the rumen of lambs grazing legumes (0.76) than in the rumen, of lambs grazing grasses (0.88). Substantial losses of dietary nitrogen occurred across the rumen, particularly in lambs grazing legumes. The proportion of ingested nitrogen lost across the rumen was related to the nitrogen content of the diet. Analysis of the present data and data from the literature suggested that growth rate was better related to the absorption of amino acid nitrogen (aaN) than to ME intake, although intake, which affected both amino acid and ME absorption, exerted the greatest influence. Estimated efficiency of utilisation of ME and aaN, above maintenance, i.e. for growth, appeared low (0.39 and 0.43, respectively) but were within the range commonly observed in animals consuming herbage diets. The retention time of digesta in the rumen (RT) is an important aspect of intake regulation. Two techniques were identified as having potential for the estimation of RT in grazing animals, and these were evaluated in early weaned lambs and, more comprehensively, in adult sheep. Firstly, RT was estimated from the rate of disappearance of digesta from the rumen of fasted sheep. Secondly, RT was estimated from the average daily rumen fill and intake of grazing sheep. The latter technique appeared to give more reliable results and was recommended for general application. Legumes exhibited shorter RT of OM than grasses (average, 6.7 v 8.8h in adult sheep, 3.5 v 8.5h in early weaned lambs). Early weaned lambs displayed a shorter RT of legumes than adult sheep, but this was not apparent for grasses. The pattern of rumen fill, in relation to grazing time, was examined in adult sheep. A consistent pattern was observed, with maximum rumen fill occurring around sunset and minimum fill occurring during the forenoon. The ability of sheep to alter the pattern of fill was studied by restricting the rumen capacity of sheep grazing P and L in spring. This was effected by inserting water filled balloons into the rumen. The presence of balloons was associated with a reduction in OMI (23 and 9% for P and L respectively), although there was no apparent change in the pattern of rumen fill. The volume of digesta in the rumen was reduced in the presence of balloons, particularly in sheep grazing P (average 16 and 9% for P and L respectively), but the total volume of rumen contents (digesta + balloons) increased (7 and 17% for P and L respectively). Therefore, it appeared that intake could be markedly increased if sheep maintained rumen fill at the maximum observed value. This seriously challenged the concept of rumen capacity regulating intake and suggested the involvement of some other factor(s). A conceptual model was developed to study intake regulation. This was based on a combination of physical and metabolic mechanisms interacting in the overall regulation of intake. It provided a qualitative explanation of the response of sheep to restriction of rumen capacity. The model concept has wide potential and warrants further investigation. In conclusion, it appears that the higher growth rate observed in lambs grazing legumes, compared to grasses, was mainly due to higher intake, although amino acid absorption appeared to be of greater importance than ME intake. The intake of high quality grazed herbage is complex and appears to be regulated by a combination of physical and metabolic mechanisms.