School of Agriculture, Food and Ecosystem Sciences - 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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ItemNutritional modification of muscle long-chain omega-3 fatty acids in lambs : effects on growth, and composition and quality of meat( 1999)Three experiments were conducted to investigate the effects of dietary supplements rich in omega-3 fatty acid on muscle omega-3 fatty acid deposition. The consequential effects on growth performance of lambs, colour and lipid oxidative stability of muscle over refrigerated display, and the sensory properties of cooked meat were also examined. A mixture of lucerne chaff : oaten chaff was used as basal diet, offered in different proportions were fed to lambs ad libitum (Expt. 1) or at 90% ad libitum (Expts. 2 and 3). Such mixtures of roughage diet support slow growth and provide a feed quality pattern similar to late spring to late summer pasture. In Expt. 1, fish meal (7%), canola meal (8%) and soymeal (7%) as natural feed supplements were compared in lambs fed low quality roughage diet. In Expt. 2, fish meal (9%) and oilseed supplements either in unprotected form (rapeseed - 7%) or in protected form (ground canola seed - 6%) were examined in lambs on medium quality roughage diet. Lipids and the proteins in the ground canola seed were treated (RUMENTEK) with aldehyde to protect them from the rumen microbial activity. Fish meal (9%), fish oil (1.5%), fish oil (1.5%) with sunflower meal protein (9%),' and sunflower meal protein alone (10.5%) (a commercial product of a protein supplement from RUMENTEK) were compared in lambs fed medium quality roughage diet in Expt. 3. Long-chain omega-3 fatty acids (eicosapentaenoic acid + docosahexaenoic acid) in muscle longissimus thoracis was increased modestly and markedly with fish meal and fish oil alone or with sunflower meal protein diet, respectively. These long-chain fatty acids were deposited in the muscle structural phospholipid rather than in storage triglycerides. All the diets mentioned above also significantly reduced omega-6:omega-3 fatty acid ratio in meat which is another beneficial effect, as the dietary recommendation in many countries has been to reduce the ratio of omega-6:omega-3 in human diet. Soymeal diet increased modestly both the omega-3 and omega-6 fatty acid content of muscle longissimus thoracis resulting in no differences in the omega-6:omega-3 ratio of the meat. A supplement of protected canola seed significantly increased the precursors of omega-6 (linoleic) and omega-3 (linolenic) but not the long-chain analogues such as arachidonic acid (omega-6) and eicosapentaenoic, docosahexaenoic acid (omega-3), respectively. The marked increase in linoleic acid content was in both triglyceride and phospholipid fractions of muscle longissimus thoracis but the modest increase in linolenic acid content was only in triglyceride fraction of meat. Supplements of canola meal used in Expt. 1, unprotected rapeseed used in Expt. 2 and protected sunflower meal protein used in Expt. 3 did not alter the fatty acid composition of muscle longissimus thoracis compared with lambs fed the control diet in that particular experiment. The increased level of long-chain omega-3 fatty acid and/or omega-6 fatty acid with the lipid supplements discussed above did not significantly affect the meat colour stability and lipid oxidative stability of fresh and vacuum packaged meat over the storage at refrigerated display. This suggests that the conditions under which the animals are grown (grazing vs grain fed or feedlot) and the species of animal are important in determining the oxidative stabilities of meat by altering the levels of muscle vitamin E concentrations at slaughter. The level of inclusion of lucerne chaff in the basal diet is an important factor in improving the redness of meat indicated by the a*-value; a higher level of lucerne chaff intake is more likely to be associated with increased intake of vitamin E. Thus colour and lipid oxidative stabilities of meat can be improved in red meat animals that are on poor quality diets by the inclusion of lucerne chaff in their diet. The sensory properties of cooked meat evaluated in the present study were not affected by the significant increase in muscle long-chain omega-3 fatty acid or omega-6 fatty acid content with fish oil and protected canola seed supplements, respectively. Addition of protected sunflower meal as a protein supplement together with fish oil significantly lowered the ratings of flavour and overall acceptability of meat compared with the control lambs. The results demonstrate that the common `lamby' and `muttony' flavour and aroma attributes were not hidden by any of the dietary treatments. These two characters associated with the species flavour and aroma were recognised by the panellists as a distinct attribute. Dry matter intake was not adversely affected by any of the lipid supplements used in the present study. Feed conversion efficiency was highest with fish meal diet on both low and medium quality roughage diets. At medium quality roughage-based diet, Feed conversion efficiency was modestly improved by protected canola seed diet but other supplements providing either natural (unprotected rapeseed) or protected protein (protected sunflower meal) did not support significant differences compared with basal diet. The significant increase in liveweight gain with fish meal diet reflected a significant increase in hot carcass weight compared with all other supplemented lambs either on low or on medium quality roughage diet. Protected lipid and protein offered by protected canola seed diet significantly and moderately increased liveweight gain and hot carcass weight from control diet but not different from unprotected rapeseed diet. The greatest muscle deposition was with the fish meal diet and is attributed mainly to the increased amount of protein and energy absorbed from the small intestine of those lambs. In addition to energy and protein absorption, the alteration of omega-3 polyunsaturated fatty acids in muscle membranes may have a further influence in lean meat production. In terms of carcass gain and intramuscular fat deposition of fishmeal and fish oil fed lambs, the results also lead to a hypothesis that modifying omega-3 polyunsaturated fatty acid of muscle membrane phospholipids may have an influence in improved muscle deposition in lambs by improving the insulin action at skeletal muscle site.
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ItemRoasted legumes for lambs( 1997)Whole lupin (Lupinus angustifolius) and narbon bean (Vicia narbonensis) seeds were dry roasted at 100, 110, 120, 130, 140, 150 and 160C for 15, 30 and 45 minutes. The effect of roasting on in vitro solubility of crude protein (CP) and 'dry matter digestibility (IVDMD) were determined. From the solubility results, seeds roasted at 130C for 15, 30 and 45 minutes were chosen to study the effect of roasting on in situ ruminal disappearance of CP and dry matter (DM). From the in situ results seeds roasted at 130C for 45 minutes were chosen to be fed to crossbred wethers for nine weeks in a 2 (grain legumes) x 2 (raw vs roasted) experiment, in rations consisting of 70% concentrate (legume seed + barley) and 30% roughage (lucerne + oaten chaff). The effect of roasting on feed intake, growth, dry matter and nitrogen digestibility, nitrogen utilization, carcass weight and fat thickness were determined. For both legumes, CP solubility decreased with increasing temperature and time of roasting. The decrease was slightly lower in narbon than in lupin. CP solubility of lupin was decreased from 84.7% (raw) to 17.3% (160C, 45 min) and that of narbon from 68.0% (raw) to 18.3% (160C, 45 min). Dry roasting had no significant (P<0.05) effect on IVDMD measured over 72 hours. In situ DM and CP disappearance was estimated by incubating nylon bags in the rumen of sheep for 2, 6, 12 and 24 hours. Dry roasting significantly (R<0.05) reduced disappearance of CP from the bags with the reduction being slightly greater for lupin (a difference of 17.8% between the raw and 45 min sample after 24 hours of incubation) than narbon (a difference of 15.0% between the raw and 45 min sample after 24 hours of incubation) but had no significant effect on DM disappearance after 24 hours of incubation. Feed intake, growth, feed conversion ratio, dry matter digestibility, carcass weight and fat thickness were not affected (P>0.05) by roasting. Nitrogen retention, expressed as a percentage of nitrogen intake or as a percentage of nitrogen absorbed, was significantly (R<0.05) higher for lambs fed diets containing roasted narbon than for lambs fed diets containing raw narbon (as % of intake 20.3 is 12.3; as % of absorbed 25.6 vs 15.4), but was lower for lambs fed diets containing roasted lupin than those fed diets containing raw lupin (as % of intake 23.1 vs 30.9; as % of absorbed 27.3 vs 37.4). Dry roasting of lupin and narbon bean seeds decreased in vitro CP solubility and reduced ruminai disappearance of CP. Nitrogen utilization in lambs fed diets containing roasted narbon seeds was improved. Roasted lupin significantly (R<0.05) reduced nitrogen utilization in lambs. However, roasting these legumes had no significant (R>0.05) effect on growth.
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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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ItemThe influence of concentrations of dietary lysine and energy offered during lactation on the lactation and subsequent reproductive performance of the first-litter sow( 1996)The first-litter sow has lower lactation and subsequent reproductive performance than older parity animals. The experimental work in this thesis was conducted to elucidate the influence of dietary energy and protein concentration during lactation on the lactation and subsequent reproductive performance of first-litter sows, whose litters were weaned at 3-4 weeks of age. In the first experiment, 140 first-litter sows were offered one of five diets, ranging in lysine content from 6.2 to 15.1 g/kg. Voluntary feed intake and sow liveweight loss were unaffected by dietary lysine concentration. However sow backfat loss was lowest for sows offered the lowest lysine diet and tended to plateau at a dietary lysine level of 10.6 g/kg. Piglet preweaning growth responded in a curvilinear manner to increasing lysine concentration. The results also indicated for sows nursing 9 or more piglets, that weaning to mating interval decreased with increasing sow dietary lysine concentration. Subsequent litter size was significantly higher for sows offered the two higher lysine diets during lactation, compared to the two lower lysine diets (10.7 vs 9.6 born alive, P<.05; s.e.d. 0.5). In the second experiment, 175 first-litter sows were offered one of five diets with a similar lysine:digestible energy (DE) ratio (0.88 to 0.85 g/MJ) but ranging in DE content from 12.6 to 15.1 MJ/kg. Voluntary food intake and piglet growth rate during lactation were unaffected by DE content of the diets. Sow liveweight loss during lactation declined with increasing energy content up to 13.8 MJ DE/kg. Backfat loss during lactation tended to be highest for sows offered the diet of lowest DE content and declined with increasing energy content up to 15.1 MJ DE/kg. The subsequent weaning to remating interval and litter size were unaffected by dietary DE content. In the third experiment, 204 first-litter sows were offered diets containing either 8.1 or 13.3 g lysine/kg during lactation. Voluntary food intake in lactation, piglet preweaning growth, sow liveweight and backfat loss during lactation, weaning to mating interval and subsequent litter size, were unaffected by dietary lysine concentration of the lactation diet. The number of corpora lutea and embryos were also not influenced by dietary lysine concentration during the preceding lactation. However, the data from those sows whose preweaning litter growth was in excess of 40 kg demonstrated a significant improvement in number of corpora lutea at the higher dietary lysine level. The results indicate that sow liveweight and fat losses during lactation appear to be more responsive to changes in DE concentration than changes in dietary lysine level. However, lysine concentration may limit piglet growth rate, weaning to mating interval and subsequent litter size. The results also suggest that improvements in subsequent litter size, observed when sows are offered high dietary lysine levels during lactation, may be due to an improvement in ovulation rate. These experiments suggest that current amino acid recommendations for lactating first-litter sows are inappropriate and may be constraining both milk production and subsequent reproductive performance.