Agriculture and Food Systems - Theses
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ItemResponses of young sheep to supplements when fed low quality roughages( 1999)The morphological components of which cereal straw is composed vary in composition and nutritive value. In a survey of relevant literature, stem materials (ST) are usually found to be consumed by ruminant animals at a slower rate than leaf material (LF) from the same crop residues when these are fed alone as separated fractions. This is attributed to the higher content of cell wall constituents (CWCs) and often lower content of N of ST. Because ST and LF can vary in proportions in the roughage fed as a basal feed, the response of animals to supplements might also be expected to be variable particularly when the basal feed is offered in excess that permits selection. In particular the response to supplemental N sources varying in ruminai degradability may vary. The objective of this thesis program was to investigate the interactions between the basal roughage and supplement measured as effects on digestion and LW responses of young sheep. The overall hypothesis was that across diets made up of different proportions of LF and ST fractions of cereal straw, the response to N supplements is dependent on CWCs concentration. The program was completed through a series of experiments conducted at the Mt Derrimut Field Satation of the University of Melbourne. In all experiments the animals were fed on a basal feed of LF or ST fractions of barley straw, with supplements including (a) Bar+USS, barley grain (Bar) fortified with urea solution prepared at a ratio of 5:1 (urea plus Na,SO4). (b) USS, urea solution alone added to the basal roughage and (c) FM, fishmeal. With each basal feed one group of lambs did not receive any supplement and served as a control group (CONT). Experiment 1 (Chapter 3) was conducted to evaluate chemical and nutritional characteristics of straw fractions of Parwon cultivar barley. Straw was separated into 4 fractions - stem (ST), leaf blade (LB), leaf sheath (LS) and broken fractions plus weeds (OT). The separated fractions were analysed chemically ( van Soest, 1974) and in vitro digestibility (Tilley and Terry 1964 ) determined. ST was the largest fraction and contained a significantly higher concentration of neutral detergent fibre (NDF; p<0.01) than LB, LS and OT (83.1, 78.6, 76.8,and 71.5 g/100g respectively). ST contained less hemicellulose (HC) than LB but more than LS and OT (37.5, 39.6, 36.3, and 35.7 respectively). N content was lower in ST than in LB, LS and OT fractions (0.4, 0.9, 0.6, and 0.7 respectively). Digestibility in vitro was significantly lower (P<0.001) for ST than for other fractions (38.5, 72.7, 60.1, and 63.0 respectively) while energy required for grinding (Chenost 1966) was much higher (P<0.001) for ST than for other fractions (121, 54.6, 64.2, 56.6 respectivly). In Experiment 2 (Chapter 4) ST and LF fractions of the same Parwon barley straw were fed as the basal feed to lambs and DM intake of ST was 15% lower than for LF (403 vs 473 g/d). When LF feed was supplemented with USS and FM, DM intake was greater by 28% and 25% respectively, while supplementation with Bar+USS resulted in 10% lower LF intake. In contrast, with animals fed ST as the basal roughage, only FM led to an increase in DM intake of only 10%. Supplementation with Bar+US and USS and FM improved overall digestibility, estimated metabolisable energy intake and N intake. Low N intakes on the basal roughages supported low ruminai ammonia-N concentrations (mg/1) immediately before feeding (ST, 20.4 ; LF 35.8), but these were improved where supplements had been fed with each of ST Bar+USS, 263.7; USS, 186.7; and FM, 151) and LF (Bar+USS, 219.5; USS, 62.5; and FM, 150). Six hours after feeding, ammonia-N concentrations (mg/l)were higher for ST (99) still low for LF(35) when fed alone, reduced below the prefeeding levels by supplements of Bar+USS (ST,167; LF 173) but raised by USS (ST, 201; LF 148) and FM (ST, 114; LF, 192). The concentrations of total volatile fatty acids (VFA) in rumen fluid (mMoUl) were not significantly different for ST and LF before feeding except where FM was the supplement, or six hours after feeding except where Bar+USS or USS were fed with LF (before feeding: ST, 51; Bar+USS, 55.7; USS,46.5; FM, 56 ; LF, 42.6; Bar+USS, 53; USS, 55.5; FM, 63.6; 6h after feeding ST, 55.5; Bar+USS, 70.2; USS, 62.1; FM, 50.4 ; LF, 55.7; Bar+USS, 69.5; USS, 60.9; FM, 60.9). Lambs on ST and LF alone lost weight (ST, -105; LF -98 g/d ). Rate of liveweight loss was less when Bar+USS (ST, -32.3; LF -2.4g/d) and USS (ST, -79.8; LF -31.2 g/d) supplements were fed, while FM promoted LW gain (ST, 37.5; LF, 72.4g/d). N retention data was consistent with these LW gains, except where Bar+USS was the supplement, in which case the animals were in positive N balance though losing weight. Wool growth was significantly improved (P<0.001) only by FM on both ST (+47%) and LF (+57%) basal roughages. In Experiments 3 and 4 (Chapter . 5 and 6) the objective was to investigate the factors responsible for low feed intake and poor performance of lambs fed ST compred to those on LF. The DMI (g/d) of lambs fed ST and LF were similar to those achieved in experiment 2; and were significantly greater for LF (P<0.001). Likewise supplements of Bar+USS, USS and FM had similar effects to those reported for experiment 2_ Changes in DMI, MEI ruminai environment before feeding or 6 and:12 hours after feeding were consistent with those recorded during experiment 2. However concentration of total VFA was significantly elevated at 12 hours after feeding. Differences in ruminal environment were evident in terms of VFA concentrations and the distribution of rumen digesta particulate material in different size fractions; both variables were affected both by the basal diet and the supplement. For LF, the proportions of particles >2mm and of very fine particles (0.125 mm) were greater and for particles between 0.5 and 1 mm less those for ST in all cases. Further, the proportion of particles >2mm was less where FM was fed than for any other feeding regime. The mean retention times of rumen fluid, measured from CoEDTA dilution rate, and calculated for rumen particulate material was longer (24%, P<0.01) for ST than for LF but there was no significant effect of supplement on this (Experiment 4, Chapter 6). The mean percentage of very fine particles in the faeces of lambs fed on LF was higher than for lambs fed ST alone or with supplements. Rate of ruminai degradation of OM of ST and LF as measured by nylon bag technique ( Experiment 3, Chapter 5) was similar at 12 and 24 hours but greater for LF than for ST at 48 and 96 hours of incubation. Bar (cracked whole grain) was degraded more rapidly and extensiveley than FM; in LF fed sheep this difference was more marked. Rate of degradation of acid detergent fibre (ADF) was influenced by the kind of supplement and was greatest in lambs given FM , and least in lambs given ST with no supplement. Only the FM supplement resulted in LW gains, though rates of LW loss were least and LW gains with FM were greatest with LF as the basal roughage. The responses are interpreted as flowing from the greater proportion of ADF and lignin in the CWCs content and the greater digestibility of ADF in the LF fraction. The ST feed fraction with higher concentrations of cell wall constituents (CWCs) as NDF was eaten at a slower rate (Experiment 5, Chapter 7) and digesta particulate material and, in these experiments, the fluid phase are retained longer in the rumen. LF showed not only an advantage over ST in these respects but also in terms of a number of important digestion parameters supported a greater response to supplements, particularly N supplements of low degradability. Thus FM is these experiments interacted with the roughage component of the diet. It provided more consistent ruminai ammonia concentrations supporting a better environment for microbial activity and growth. Microbial protein together with undegraded dietary protein together provide a balance of nutrients that allows LW gains on otherwise submaintenance basal feeds. The greater enhancement of performance with LF compared to ST and the particle size measurements suggest that greater fragmentability of LF may be a major contributor . In terms of technical improvement of livestock feeding systems, providing the animal with opportunity for selection of more leaf and less stem may improve the likelihood of responses to supplements but this was not demonstrated in Experiment 5. FM was used as the experimental supplement to provide slowly degraded and undegraded dietary protein of high biological value to the animal. FM is expensive and other crop byproducts and local feed materials with properties of slow degradability of protein and good amino acid balance need to be identified. An alternative strategy would be to provide a maximum opportunity for the selection of most digestible parts. If refusals are then collected, quality could be further improved with alkali treatment and necessary supplementation. This would provide a strategy for the use of morphological fractions which could be an economical approach for the efficient utilization of roughages.
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ItemFinishing prime lambs using pulse stubbles, and pulse and cereal grains in the Wimmera region of Victoria( 1998)Three trials were conducted as part of this study. The first trial evaluated faba bean and chick pea stubble as feed source for the finishing of lambs. The second trial evaluated the use of barley and field peas in feed lot rations for lambs, and the final trial evaluated narbon beans and vetch as substitute grains for field peas in feed lot rations for lambs. In the first experiment one hundred and twenty six Poll Dorset x (Border Leicester x Merino) mixed sex lambs with a mean liveweight of 40.0 kg � 0.3 kg were grazed on faba bean (FB) or chick pea (CP) stubble at a stocking rate of 6.5/ha and received a supplement of 300 g/hd/day of barley (+B) or were unsupplemented (-B). There was no significant difference (P>0.05) in average daily gain (ADG) over the duration of the trial between lambs grazing faba bean and chick pea stubble, supplemented with barley or unsupplemented. Lambs supplemented with barley tended (P- 4.06) to have a lower ADG in the first fortnightly period, and had significantly lower (P<0.05) ADG in the second period. This result is supported by the observation of supplemented lambs not grazing the stubble but waiting to be fed the barley supplement. This result was reversed in the third period when supplemented lambs tended (P~.06) to have a higher ADG, and in the final period when the ADG was significantly higher (P<0.05) than the unsupplemented lambs. There was a significant correlation (P<0.01 for faba bean stubble and P<0.05 for chick pea stubble) between ADG of unsupplemented lambs and the quantity of grain residue in the stubble. In the second experiment eighty Border Leicester x Merino mixed sex lambs with a mean liveweight of 27.3 kg � 0.2 kg were fed barley (B) or barley + field peas (B+FP) (60:40) either daily at 800 g/hd/day or ad libitum for 56 days following a 14 day introductory period. Hay was provided ad libitum. There was no significant difference (P>0.05) in ADG between lambs fed the treatment rations. Lambs fed B+FP were significantly different to lambs fed barley in the following: higher carcass weight (P<0.05); fatter (P<0.05); higher dressing percentage (P<0.01); higher estimated carcass weight gain (P<0.05) and lower dry matter intake to estimated carcass weight gain ratio (P<0.05). There was no significant difference (P>0.05) in any of the measured characteristics between lambs fed restricted or lambs fed ad libitum. In the third experiment twenty four Poll Dorset x (Border Leicester x Merino) lambs with a mean liveweight of 28.8 kg � 0.45 kg were individually penned and fed ad libitum a ration of narbon beans (NB), vetch (V) or field peas (FP) mixed with wheat and formulated to 16% crude protein. Milled hay was provided separately ad libitum. There was no significant difference (P>0.05) in growth rate, carcass weight, dressing percentage, feed intake, or dry matter intake to liveweight gain ratio between lambs fed the three rations. The growth rate and feed intake of lambs fed FP was more consistent than lambs fed NB or V. Scouring was observed in lambs fed V. There was highly significant (P<0.001) separation and selection of wheat in the NB and FP based rations. Further research needs to be carried out to evaluate meat quality of lambs fed narbon beans and vetch, in particular to determine if there is any effect on flavour of the meat. The use of pulse stubbles, combined with lot feeding can form a feeding system to enable lambs to be finished in the autumn-winter period in the Wimmera region. The growth rate of lambs grazing pulse stubbles is dependent on the quantity of grain residue on the ground. The growth rate can be maintained as grain level declines by the introduction of a barley supplement. Lot feeding can be used to finish lambs when pulse stubbles have been grazed out. A combination of a cereal grain and a pulse grain formulated to 16% crude protein can be fed ad libitum. Hay can be provided separately ad libitum, or a more controlled intake of hay can be achieved by feeding a calculated amount daily.
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ItemAcute prenatal androgen treatment in sheep( 1994)The steroid environment of the cell nucleus in differentiating mammals is a major determinant of subsequent cellular function. The exogenous manipulation of this environment has resulted in permanent changes in metabolism, behaviour, reproduction, endocrinology and growth. The experiments described in this thesis suggest that an acute exposure to exogenous androgen, established as an intramuscular depot in the gravid ewe, can effect these changes. The growth responses resulting from acute prenatal androgen treatment (APAT) are similar to those reported for chronic androgenization.The undesirable side effects of androgenization, e.g. reduced birthweight, deformed external female genitalia and masculine urination posture, can be avoided with APAT. The literature and the experimental data indicate that mammalian development is strongly influenced by tissue steroid status. Furthermore, the literature and the experimental data suggest that both the timing and duration of the modification of mammalian developmental steroid status (MDSS) affect the response of ovine tissues to androgens. Some of the observed responses appear refractory in nature. The periods of sensitivity to MDSS manipulation differ between tissues and between species. MDSS manipulation via APAT is capable of effecting changes to tissues not normally considered sexually dimorphic, including the ovine pancreas, liver, brain, kidney, bone and wool follicle.
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ItemCowpea and navy bean seeds as supplements for sheep( 1992)This study was conducted to determine the feeding value of cowpea and navy bean seeds as supplements for growing sheep fed equal amounts of oaten chaff and barley straw (basal diet) and the digestibility of the basal diet when cowpea and navy bean seeds were used. Thirty-six sheep were used both in period 1 and period 2 of the feeding trial (Experiment 1), randomly assigned to no supplement, 0.5, 1.0 and 2.0% LW of lupin, cowpea and navy bean, and 2.0% LW of lupin and navy bean plus antibiotics, and twenty-four sheep were used in the digestibility trial (Experiment 2) using 1.0% LW of lupin, cowpea and navy bean and no supplement. Results indicated that navy bean seeds and cowpea seeds when used as supplements should be limited by up to 0.5 and 1.0% LW respectively for sheep fed equal amounts of oaten chaff and barley straw.
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