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    Venison production from weaner red deer stags grazing Moata annual ryegrass or perennial ryegrass pastures : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in animal science at Massey University, Palmerston North, New Zealand
    (Massey University, 1990) Ataja, Abu Mohammed
    Four grazing experiments were conducted with red deer stags, three with weaner stags (start 6 months old ; end 12 months old) and one with yearling stags (start 15 months old; end 21 months old). In New Zealand (NZ) the calving season for red deer is during late spring/early summer (November/December) and the calves are normally weaned in late February/early March. The price schedule for venison is highest during August to November, in response to Northern Hemisphere export market demand and is greater for carcasses of 50 kg or above. However, there is no well defined system for meat production from deer. The objective of these studies was to evaluate different systems of growing red deer stags to a slaughter liveweight (LW) of 92 kg (>50 kg carcass weight (CW)) by one year of age or less, by the end of November. Thus an attempt was made to define a system of meat production from deer that was most profitable to NZ venison producers. [... full abstract in file 01_front]
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    The nutritional value of ryegrass-white clover leaf protein concentrate : a thesis presented in partial fulfillment [sic] of the requirements for the degree of Doctor Philosophy in Biochemistry at Massey University
    (Massey University, 1983) Johns, David Carville
    Leaf Protein Concentrate (LPC ) , which was manufactured from a mixture of Ryegrass and White Clover (Lolium perenne and Trifolium repens) at the Ruakura Agricultural Research Centre , was evaluated as a possible protein source for feeding to chickens . The nutritional value of LPC was compared to that of soybean meal ( SBM ) . LPC was shown to have a lower nutritional value than SBM in the growth trials . The addition of methionine or cystine to the diet containing LPC improved both food utilization and weight gain of the chickens . These growth parameters showed the greatest improvement when 2 g methionine/kg diet was added to the LPC diet. The additional quantity of 2g methionine/kg diet was similar to the amount of sulphur amino acid contributed by LPC to the d i e t ; 1.8 g sulphur amino acid from L PC /kg diet. When an equivalent amount of cystine (1.6g) to methionine , on a sulphur basis , was added to the LPC d i e t and fed to chickens , it was shown to support the same amount of growth and maintain a similar food utilisation level as additional methionine . LPC contributed only 0.6g cystine/kg of diet . As this was much lower than the added cystine and/or methionine , it was concluded that the availability of cystine in the whole diet was reduced by the presence of LPC rather than the lack of availability of cystine in LPC alone . The following information was also obtained : - (i) Pancreatic hypertrophy and increased pancreatic enzyme activity (trypsin and chymotrypsin ) occurred due to feeding the LPC diet . (ii) The invitro exhaustive enzyme digestibility study indicated that while the overall digestibility of LPC was approximately 6% lower than that of SBM, none of the individual amino acid digestibility estimates i n LPC diverged markedly from the mean . All LPC amino ac ids were released equally by enzyme hydrolysis . (iii) In contrast to the invitro findings , the in vivo mean amino acid availability estimates for the ingredient LPC (as measured in the excreta) were lower than the corresponding SBM estimates by approximately 1 5% . The cystine availability estimate for the ingredient LPC was only 5 1 . 2% in terms of corrected amino acid availability ( CAAA), and 1 1 . 9% in terms of apparent amino acid availability ( ApAAA). By comparison the cystine availability estimates for the ingredient SBM were 80 . 8% CAAA and 7 5 . 7 % ApAAA. When the diets containing LPC or SBM were assayed by the same technique , the differences in the amino acid availability estimates were markedly reduced . The availability estimates of cystine in the LPC diet were still lower than the other amino acid availability estimates for the LPC diet . These however were only 8-10% lower than the corresponding estimates for the SBM diet. (iv) The mean amino acid digestibility estimates, derived by analysis of the ileal contents of chickens fed with the LPC d i e t were 26% lower than those for chickens fed the SBM d i e t s . The cystine digestibility estimates for the LPC d i e t was approximately 45% lower than the corresponding cystine digestibility estimate for the SBM diet. These results indicated that digestion and/or absorption of the LPC diet was probably being retarded as compared with the SBM diet. (v) Supplementation of the LPC diet with the antibiotic , Neomix , gave an improvement in growth and an increase in the mean amino acid availability ( measured by excreta analysis ) of approximately 7%. This indicated that the gut microflora were influencing the nutritional value of LPC . Feeding the LPC diet in comparison to feeding the SBM diet also tended to increase the level of c1 9 cyclopropane fatty acid in the excreta. This indicated that feeding the LPC diet was influencing the nature and/or activity of the microfloral population . The physiological and metabolic effects of feeding r aw soybean meal and/or trypsin inhibitors , which have been reported in the literature, included pancreatic hypertrophy , increased pancreatic proteolytic enzyme activity , retardation of ileal protein digestibility and.an influence by gut microflora . Each of these factors were characteristic of chickens fed the 1PC diet. It was therefore concluded that the additional need for cystine or methionine by chickens fed the 1PC diet , was due to the presence of trypsin inhibitors in the 1PC . It was demonstrated, by feeding 1 - (methyl 14c) methionine that phenolic compounds were being methylated . However the need for detoxification of aromatic compounds , which required methionine (as a methyl donor ) and /or arginine ( ornithine ) , could not explain the growth depression experienced by chickens fed the unsupplemented 1PC diet. The feeding of 1- (methyl 14c) methionine in conjunction with the 1PC diet also indicated that the digestibility of methionine was not being hindered during the digestive process by preferential binding with other compounds in the 1PC diet. I t was concluded from the result s of this study that 1PC adequately supplemented with methionine , could b e a useful addition to the range of ingredients available for use in poultry feeds.
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    Aspects of water deficit and vegetative growth in selected pasture and forage grasses : a thesis presented in partial fulfilment of the requirement of the degree of Doctor of Philosophy at Massey University, Palmerston North, New Zealand
    (Massey University, 1979) Chu, Alexander Cheong Ping
    In this study, the sensitivity of leaf extension to plant water status, the ability of the plant to recover after different periods of water deficit and the plant's reaction to atmospheric pre-conditioning were examined using different pasture and forage grasses. The sensitivity of leaf extension to plant water status was studied in 3 separate experiments using sudax (SX-6, a forage sorghum hybrid, Sorghum bicolor (L) Moench x S. Sudanese (piper) Staff), prairie grass (Bromus catharticus Vahl. cv. Grasslands Matua) and 2 cultivars of perennial ryegrass (Lolium perenne L. c.v. Grasslands Nui and Grasslands Ruanui). The sudax experiment was conducted in the field, whereas the prairie grass and ryegrass experiments were conducted in the Climate Laboratory, D.S.I.R. The day/night temperatures used in the prairie grass experiment was 22.5°/l2.5°C. For the ryegrass, 2 contrasting temperature regimes were used; these were high (H), 27.5°/12.5°C, and low (L) 17.5°/12.5°C day/night temperatures. It was found that leaf extension was very sensitive to small changes in leaf water potential during the initial stages of desiccation, but the response became less sensitive with increasing levels of desiccation. However, the relationship between leaf water potential and leaf extension rate was not unique. It varied according to the environmental conditions. The true relationship between leaf water potential and leaf extension rate can only be established when the leaf water potential at the site of measurement can be related unequivocally to the leaf water potential at the site of elongation. The rates of recovery in leaf extension, leaf emergence, tiller number, green leaf number, leaf area and dry weight per plant were followed after different water deficit treatments in one experiment with prairie grass and in another experiment with 2 cultivars of perennial ryegrass under 2 contrasting temperature regimes. The environmental conditions for these experiments were the same as those used in the leaf extension experiments. In prairie grass, upon relief of water deficit, the previously desiccated plants showed an "accelerated" rate of leaf extension up to 20% higher than those of the well-watered control plants of the same physiological age. The "accelerated" rate lasted for over 28 days after rewatering during which time 4 to 5 new leaves emerged. However no such "accelerated" rates were observed in the ryegrasses. The "accelerated" response following rewatering in prairie grass would be consistent with a differential sensitivity of cell division and cell elongation to water deficit. The desiccation treatment was more severe in the ryegrass experiment where both cell division and cell elongation could be suppressed, and this could account for the absence of a similar response in the ryegrasses. Under well-watered conditions, the mean leaf emergence rate was 4.1 days per leaf for the prairie grass. The corresponding mean leaf emergence rates for Nui and Ruanui were 5.7 and 6.3 days/leaf under the H and 6.6 and 6.6 days/leaf under the L temperature regimes respectively. Within the grass species, post-desiccation leaf emergence rates between the previously desiccated and the well-watered plants were similar. During desiccation, tiller number was the least sensitive parameter to water deficit, followed by dry weight and leaf number. Leaf area was the parameter most sensitive to desiccation. Amongst the dry weight components, lamina, component was the most sensitive followed by the root component with the sheath component the least sensitive to desiccation. The pattern of recovery from desiccation was examined to see if positive or negative carryover effects occurred. To enable valid comparison of desiccated and control plants physiological age was adjusted by removing a number of "drought" days from the chronological age. It was found that when the desiccation was mild e.g., in the prairie grass experiment, reductions in plant dry weights were proportional to the number of "drought" days. On the other hand, under a more severe level of desiccation, e.g., as in the ryegrass experiments, using the same method of adjustment, it was found that the dry weights of the previously desiccated plants were substantially lower than those of the well-watered control plants of the same physiological age. The reduction in dry weight was more pronounced under the H than under the L temperature regime. After rewatering, in both prairie grass and ryegrass, the relative rates of increase of leaf area were higher in the previously desiccated plants than the well-watered control plants. In contrast to this, the relative rates of increase in dry weight, tiller number and leaf number in the previously desiccated plants were either similar to, or slightly less than those of the well-watered control plants. Although the pattern of recovery in the leaf extension rates was different between the two experiments, this had no apparent positive or negative carryover effects on the relative rates of recovery in the growth parameters measured (e.g., tiller number, green leaf number, leaf area and dry weight per plant). The reaction of prairie grass to desiccation following either a "dry" or a "wet" atmospheric pre-conditioning was compared with those plants that were grown continuously under either the "dry" or the "wet" vapour pressure environments. Plants with a previously "dry" history were able to grow longer into the desiccation period than those with the "wet" history as well as those under the continuous "wet" or "dry" conditions. This apparent "adaptation" was due to a more efficient rate of water use per unit leaf area by the "hardened" plants. But the mechanism that enabled these plants to use water more efficiently was not known. Nui had been reported to outyield Ruanui under the summer and autumn conditions in New Zealand. Because of the importance of perennial ryegrass to New Zealand, a comparison of these 2 cultivars was also made in this study. Between the two cultivars of ryegrass, Nui had a higher leaf extension rate (+20%) under the H temperature regime, it also had a heavier mean tiller dry weight (+28%), a larger mean area per leaf (+24%), but a lower tiller number (-24%) and a lower green leaf number (-18%) per plant than Ruanui. All the other paramters measured, including total leaf area and total dry weight per plant, top to root ratio, specific leaf area, leaf area ratio, stomatal resistance and transpiration rates were similar between the two ryegrass cultivars. Some of the possible reasons for the lack of difference on a per plant basis are discussed. The possibility of using leaf extension rate to predict plant dry weight changes in water deficit studies is also discussed.
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    A study of seasonal root and tiller dynamics in swards of perennial ryegrass (Lolium perenne L.) : a thesis presented in partial fulfilment of the requirements for the degree of Ph D in Agronomy at Massey University
    (Massey University, 1992) Matthew, Cory
    Objectives of this study were (i) to provide data on seasonal variation in root mass and root replacement in perennial ryegrass dominant swards, (ii) to simultaneously collect parallel data for above-ground parameters tiller population density, tiller natality, tiller mortality, herbage mass and herbage production, and (iii) to determine if such information on the behaviour of root and shoot systems and the inter-relation between the two could identify ways in which grazing management manipulation favouring root system development might subsequently result in pasture production increases. Perennial ryegrass was chosen for study because it is the species most commonly used in new pasture sowings in New Zealand. Four field experiments and two glasshouse experiments are reported. In the first field experiment, techniques for making measurements of root mass and root production in field swards were evaluated. Over 80 days from November 1985 to February 1986, total root mass measured by washing roots from "intact" soil cores did not change, but root mass in core-holes bored out and "refilled" with sand was 53% of that in intact cores. The refilled core technique was therefore adopted as a measure of "apparent" root production, and a later calibration study showed that measurements using the refilled core technique underestimate actual root growth. Using the refilled core technique, differences in root production were detected between six mowing treatments designed to allow varying degrees of reproductive development. Root growth was greater where mowing of swards was delayed sufficiently to allow reproductive growth until head emergence or anthesis than where seedheads were either removed before head emergence or left un-mown until seed-set. There was also evidence of increased tillering on treatments with the highest root growth. In the second experiment (December 1986 to May 1988) plots were subjected to lax (LL) or severe (HH) grazing management or to cross-over LH or HL grazing managements. The cross-over date, December 7 1987, was timed to coincide with peak reproductive development. Swards in this study had approximately 100 m m-2 underground stolon, with a seasonal increase in late winter and higher stolon formation on LL plots than on HH plots. Apparent root growth rates exhibited marked seasonal variation, and were typically about 15% of above-ground net production. For 12 months from January 1987 to January 1988 apparent root growth averaged 8.4 and 7.3 kg DM ha-1 day-1 for LL and HH plots, respectively for 0 - 600 mm soil depth. Because of these relatively small differences in root growth, it was concluded that manipulation of root growth would not enable herbage production advantages to be achieved. However, after introduction of crossover grazing managements, high herbage production was observed on LH plots and tissue turnover and herbage dissection measurements showed that this high herbage production was associated with high daughter tiller formation, probably from stubs of decapitated flowering tillers. Experiment 3 (November 1988 to January 1989) comprised 3 plots under common grazing management, and was designed to provide detailed information on the location on the tiller axis of actively elongating roots, and to confirm seasonal patterns of root and tiller growth observed in Experiment 2. Root initiation normally occurred at the same node as leaf senescence, normally two roots formed at each node, and few active roots were found more than 10 nodes below the last leaf. Seasonal timing of peak root growth and tiller appearance was different from that in Experiment 2, however. This is believed to reflect genetic differences between the cultivars 'Ellett' used in Experiment 2 and 'Grasslands Ruanui' used in Experiment 3, but specifically designed controlled comparisons would be needed to confirm this. Experiments 4, 5, and 6 were designed to provide more information on the reasons for high tillering on LH plots in Experiment 2, and investigated the number of daughter tillers formed by flowering tillers subjected to differing cutting treatments. In all three experiments the number and weight of daughter tillers formed was greatest where a degree of reproductive growth occurred, and was reduced where seedheads were cut closer to the ground or earlier, and where seedheads remained uncut to act as a competing sink. These observations indicate that assimilate from parent flowering tillers is important for daughter tiller formation and, in Experiment 6, a cutting treatment which increased translocation of carbon-14 tracer from labelled flowering tillers to daughter tillers also increased the number and weight of daughter tillers formed. It is concluded that grazing management which exploits the potential for high tillering rates from stubs of flowering tillers could increase herbage production on many New Zealand farms by more than 0.5 t DM ha-1 over the summer/autumn period, and implications for farm practice are briefly discussed.
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    Variations in ryegrass varieties in respect to milk production : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1969) Wilson, Gavin F.
    A study was made of some aspects of the nutritive value of ryegrasses with particular emphasis on the relationship between the chemical composition of the pasture and the quantity and quality of milk produced by grazing dairy cattle. The fat content of the milk from Friesian cattle was shown to be depressed when grazing an annual variety of ryegrass during the winter. Depressions in the solids-not-fat content of the milk, on the other hand, were associated with the grazing of Ruanui perennial ryegrass in experiments carried out in the winter and in the spring. The mechanisms involved in producing these differences in milk composition were investigated in a series of experiments in which various supplements were given to animals consuming pasture. Carbohydrate, protein, and lipid supplements were given to: lactating cows to measure effects on milk production, cattle and sheep with rumen fistulea to measure end-products of rumen fermentation, and dry sheep in metabolism crates to study the digestibility of pasture components. It was concluded that the nature or levels of the carbohydrate, protein and lipid fractions of pasture may all influence milk composition and that optimum plant composition is likely to vary according to the type of milk product that is required to be produced.