School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemComposition of commercial pig diets and utilization of piggery wastes( 1977)The work presented in this thesis was part of an integrated study conducted by the School. of Agriculture and Forestry into various aspects of piggery waste utilization. Particular attention was given to the occurrence and source of mineral elements in pig diets and piggery wastes. Results of analysis of commercial pig diets and piggery wastes are discussed in relation to nutritional requirements and toxicities and from environmental and legislative aspects. The Literature Review in Chapter 2 describes how similarities in the atomic orbital configurations of some transition elements and oxy-anions can explain the synergisms and antagonisms displayed by these chemical entities in biological systems. In particular, the concept of orbital equivalence is used to explain some of the better known cases of mineral antagonisms affecting the health and nutrition of livestock. The antagonism between sulphate and molybdate ions is discussed relative to their ionic structures and to their respective involvements in copper metabolism. The interactions of copper, zinc and iron are examined, particularly in relation to pig nutrition. Interactions between copper, zinc and cadmium are related to their orbital structures and to their ability to form metallothioneins. The ability of high levels of copper and zinc to induce selenium deficiency in chicks is discussed and associated with the similar orbital configurations of zinc, copper and selenate ions. Caution is proposed in the formulation and mineral supplementation of multi-constituent diets used in intensive animal production. Procedures used in the development and calibration of analytical techniques for the determination of eleven elements in pig faeces and pig diets are described in Chapter 3. Copper, zinc, iron, cadmium, lead; sodium, potassium, magnesium, calcium and phosphorus were measured from a single sample digestion using a nitric-perchloric acid mixture. Phosphorus content in the digest was determined colorimetrically and the remaining elements by atomic absorption spectrometry. A separate digestion procedure was required for arsenic which was then measured by atomic absorption spectrometry after generation of arsenic as its hydride. Accuracy and precision of the techniques were rigorously tested using standard addition and recovery procedures- and comparison of values obtained after analysis of the U.S. National bureau of Standards Reference Material ''Orchard Leaves". Chapter 4 reports the chemical composition of pig diets, ingredients of diets and mineral-vitamin supplements collected from 24 commercial piggeries in Victoria. An evaluation of the diets relative to the suggested dietary mineral requirements for grower pigs proposed by the Agricultural Research Council (A.R.C.) indicated that mineral imbalances occurred in many of the diets. High levels of cadmium and lead found in some diets originated principally as contaminants of mineral additives and from meat meals, meat and bone meals and fish meals. The mineral content of the diets was found to be highly variable and indicated differences in choice of dietary ingredients and in the practice of mineral supplementation. Copper, zinc, and iron levels in the diets were particularly variable and in the case of zinc and iron were present at concentrations far in excess of the levels suggested by.the A.R.C. Chapter 5 describes the chemical composition and in vitro organic matter digestibility (OMD) of pig faeces samples collected from 24 piggeries in Victoria. Pig faeces are shown to be highly variable in chemical and nutrient content and, in some instances, to contain high levels of potentially toxic mineral elements such as copper, cadmium, lead and arsenic. Wide ranges in in vitro OMD values, proximate constituent concentrations and cell wall composition were also recorded. Multiple regression analysis associated low in vitro OMD with high values of cell wall content, phosphorus, copper and lignin/cell wall. Standard additions of phosphorus and copper to pig faeces samples undergoing in vitro fermentation significantly lowered the OMD values of these samples, contributing further evidence of the possible inhibitory effects of these elements to the digestive processes of the ruminant. Some health aspects of refeeding pig faeces as an ingredient in diets for ruminants are discussed, particularly in relation to the presence of toxic minerals such as copper, cadmium and lead. In Chapter 6 a procedure is described for calculating the chemical composition of pig manure using dietary composition, recommended feed intakes, published retention values for each element and estimated excreta outputs fin. an "average" pig of 45 kg liveweight. The variability in the calculated composition of manure is discussed in relation to existing and proposed guidelines limiting the rates of application of pig manure to land. Some aspects of the proposed guidelines for Victoria are discussed; particularly in relation to the suggested maximum rates of manure application to provide not more than 500 kg of nitrogen or 300 kg of potassium/hectare/ annum. Because of the range in the estimated nitrogen content of pig manures, the quantities of manure supplying 500 kg of nitrogen were calculated to range from 46 - 123 tonnes with an average of 63 tonnes. Included in these quantities were widely varying amounts of other elements which would be applied to land with 500 kg of nitrogen; some of which are known to pose environmental problems through leaching to ground water, as run-off to waterways or through ingestion by grazing animals. The potential environmental hazards of applying large amounts of minerals, including heavy metals, to land are discussed and a method is proposed which would permit a more accurate estimate of manure loading rates to provide 500 kg nitrogen/ hectare of land.
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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.
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ItemGrowth and digestibility in finishing pigs fed various levels of raw mung beans (Phaseolus aureus [Roxb.] var. Berkin)( 1991)Two experiments were conducted to evaluate raw mung beans (Phaseolus aureus [Roxb] var. Berkin) as a source of protein and energy for finishing pigs. In the first experiment, 6 cross-bred (Landrace X Large White) boars of 53 kg liveweight were used to determine the digestible energy (DE) content of ground mung beans by substitution where 30% ground mung beans were included in a basal (wheat) diet at the expense of wheat. The DE content of mung beans was 16 � 0.9 MJ/kg DM. In the second experiment, 24 boars of 58 - 65 kg liveweight were allocated to 6 groups of four and individually fed diets containing 0% (control), 10%, 15%, 20%, 25% and 30% mung beans substituting for the same amount of soybean meal. All diets contained 14.5 MJ DE/kg and an estimated 0.65 g lysine/MJ DE.. Daily feed allowance was restricted to approximately 35 MJ DE. There was no significant difference (P>0.05) between treatments in average daily gain (ADG), feed conversion ratio (FCR), backfat (P2) or relative weights of pancreas, liver, kidney, stomach, small intestine and large intestine. The ADG and FCR were 0.96 � 0.02 kg and 2.60 � 0.05 units of feed/units of gain respectively, whilst P2 was 15.9 � 0.27 mm. The weight of the pancreas, liver, kidney, stomach, small intestine and large intestine relative to body weight were 0.15 � 0.01; 2.07 � 0.03; 0.39 � 0.01; 0.61 � 0.01; 1.96 � 0.03 and 1.41 � 0.03 per cent respectively. Organic matter (OM) and ether extract (EE) digestibilities were not affected by the levels of mung beans, but levels beyond 20% significantly (P< 0.05) decreased apparent digestibility of crude protein (CP) and increased digestibility of neutral detergent fibre (NDF). Under the condition of this study, this variety of mung beans can be incorporated in finisher diets up to 30% without negative effects on growth performance.
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ItemThe effects of lactation feed intake on subsequent embryo survival in sows( 1991)Large litter sizes at birth and weaning are desirable for the pig producer. Pigs have been continually selected for high fecundity for many years, but to express and maintain their full potential for production their nutrient requirements must be met. This thesis reviews the physiology of reproduction (follicular growth, corpus luteum formation, uterine changes and secretions and hormone changes in the mature sow) and the short-term and long-term effects of nutrition on reproduction. The short-term effect of nutrition is expressed in terms of sow performance during the period of feeding (e.g. effects of gestation nutrition on prenatal mortality). Long-term effects of nutrition include the effects of lactation nutrition on subsequent reproduction. While the effects of lactation nutrition on the length of the weaning to remating interval, ovulation rate and subsequent litter size have been extensively investigated, there is little information on the relationship between lactation feeding and subsequent embryo survival. The current study used different levels of feeding during lactation to determine whether lactation feed intake would affect subsequent embryo survival and other parameters of reproductive performance in the sow. A total of 30 multiparous sows (parities 4 to 10) were employed in this study. During a 28-d lactation, they were given either 3 or 6 kg per day of feed containing 14.2 MJ DE/kg and 19.4% CP. Between weaning and mating they were fed 3 kg/d of the lactation diet, and during gestation they were fed 2.3 kg/d of a gestation diet (12.5 MJ DE/kg, 16% CP). The number of piglets per litter were equalized by cross-fostering within 3 days after farrowing to minimize variation in litter size suckled. After weaning sows were checked for oestrus twice daily and were mated twice at their first postweaning oestrus. They were weighed and P2 backfat was measured by ultrasound at day 110 of gestation, within 24 h after farrowing, weekly during lactation, at weaning, at mating and every 5 days during gestation. Blood samples were collected by jugular venepuncture on days 2, 5, 8, 11, 14, 17, 20 and 23 post mating. Immediately after collection, samples were centrifuged at 3000 rpm for 10 minutes and plasma was stored at -20C until assayed for progesterone. All plasma samples were analyzed for progesterone concentration by direct progesterone Radioimmunoassay. All successfully mated sows were slaughtered between day 24 and 27 post coitus. After slaughter the reproductive tract was removed and examined within 3 h to estimate the number of corpora lutea, ovarian weight, number of viable embryos, space between embryos and uterine length. The results showed that lactation feed intake had significant effects on sow weight and backfat changes during lactation. Sows on the low treatment (L) lost considerable weight (-23.3�3.4 kg) while the high-fed sows (H) gained (+6.4�2.4 kg) weight (p < 0.001). During the same period sows in both groups lost backfat (-0.04�0.26, -2.39�0.47 mm for H and L sows, respectively), low-fed sows losing significantly more than their high-fed counterparts (p < 0.001). Between weaning and mating, while both groups gained backfat (0.13�0.13, 0.88�0.38 mm for H and L sows, respectively) (p< 0.05), the high-fed sows lost (-3.8�1.9 kg), but the L sows gained weight (2.3+1.3 kg) (p < 0.1). In the period between mating and slaughter, sows on the high and low treatments lost similar amounts of weight (-5.1�2.2, -3.8�5.8 kg for H and L sows, respectively) and backfat change during this period was also similar for the two groups (+0.06�0.26, -0.13�0.52 mm for the H and L sows, respectively). Lactation feed intake did not significantly affect the weaning to remating interval and proportion of sows that were pregnant at slaughter. However, it did influence the proportion of sows showing oestrus by 8 days postweaning (p < 0.05) (11/12, 5/10 for H and L sows, respectively). With the exception of space between embryos no parameter of reproductive performance measured at slaughter ( i.e. ovulation rate, ovarian weight, uterine length, number of viable embryos, embryo survival rate and embryo crown-rump length) was significantly affected by lactation feed intake. Progesterone change pattern and concentrations during early pregnancy were also not significantly influenced by level of feeding. For old sows which have low body fat reserves, and lose little weight and backfat during lactation, reproductive performance is unlikely to be affected by lactation feed intake.
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ItemThe influence of nutritional factors in the development of postweaning diarrhoea in early weaned pigs( 1984)1. The study concerned the significance of change of diet and feeding method on the clinical, pathological and growth responses of 3- to 4-week-old pigs when subjected either to challenge with an enterotoxigenic serotype of Escherichia coli or exposed to 'natural' infection with E.coli. It involved experiments with both hysterotomy-derived specific pathogen-free (SPF) piglets and conventionally reared animals. The dietary treatments involved comparisons between (i) wet versus dry feeding and (ii) skim milk versus soyabean (SB) meal as the major dietary protein source. 2. Under closely controlled SPF conditions, thirty-five 28-day-old piglets were used in five experiments. In the first four experiments, two groups were changed from a liquid cow's milk diet to a milk-based diet (termed the 'basal' diet), given either in wet or dry form. Within each group, half of the animals were orally challenged with enterotoxigenic E.coli (ETEC) bearing the K88 antigen and the remainder, serving as controls, were challenged with a non-pathogenic K12 E.coli strain. ETEC-infected piglets fed the dry, basal diet developed severe diarrhoea, depression and dehydration and at necropsy exhibited severe lesions in the small intestine associated with extensive bacterial adherence and marked reduction in intestinal lactase activity. Infected piglets fed the basal diet as a gruel had only mild diarrhoea, accompanied by limited bacterial adherence and minor mucosal and physiological changes. Control piglets, fed either dry or wet, remained clinically healthy and the morphology of the intestinal mucosa was normal. In the fifth experiment, two groups were changed from the liquid cow's milk diet to either a dry-fed basal diet or a dry-fed SB-based diet; each group consisted of both infected and control animals. Control piglets on both diets remained clinically normal with only minor mucosal changes; but the intestinal lactase activity of those fed the SB diet was depressed. Infected piglets fed the SB diet developed mild diarrhoea, depression and dehydration. Infected piglets fed the basal diet had no diarrhoea but were depressed. Bacterial colonization, mucosal and physiological changes were relatively more severe in the SB-fed animals than in those fed the basal diet. 3. Under conventional conditions, a total 0f one hundred and seventy-six piglets, from the Mt Derrimut herd, were used in three experiments. In each of these experiments, pigs were allocated among four dietary treatments: dry, basal; wet, basal; dry, SB; and wet, SB. In Expt 1, a total of twenty-four pigs were orally inoculated with K88 ETEC following their transfer at weaning to non-specialized pen accommodation (at the Attwood Institute for Veterinary Research). In Expts 2 and 3, (conducted at the Mt Derrimut Pig Centre), ninety-six and fifty-six pigs respectively were moved at weaning into specialized weaner accommodation that was routinely used for early weaning on a batch basis. No inoculations with ETEC were performed in these two experiments. In Expt 1, all pigs remained clinically normal except for one pig fed the SB diet dry. Post-mortem studies conducted on four selected pigs from each treatment group revealed very limited colonization by ETEC but without marked changes in gut morphology (although K88 ETEC were present in faecal materials). In Expts 2 and 3, natural infection with ETEC and manifestation of PWD (postweaning diarrhoea) occurred. As compared with the SB diet, the basal diet particularly when fed wet, resulted in a less severe diarrhoea. Morphological and physiological changes in the small intestine were less pronounced and bacterial adherence was less extensive. Whether the SB diet was fed wet or dry made little difference in these respects. In the first 14 days post-weaning pigs fed the basal diet, especially when this was fed wet, made faster and more efficient weight gains than those given the SB diet. The degree of infection was more widespread and severe in Expt 3 than in Expt 2. In Expt 3, the superiority of the milk-based diet compared to the SB diet was relatively greater during the first 14 days post-weaning. 4. The results indicated that both the type of diet and the form in which the diet was fed, significantly influenced the extent of colonization of the gut by ETEC, the severity of PWD and growth performance. The effects of feeding method were more apparent in the SPF piglets than in the conventional piglets. This was attributed to the greater influence of uncontrolled variables in the latter situation. 5. The greater variability of performance under the conventional rearing conditions and the marked difference in response to ETEC in Expt 1 compared with that in Expts 2 and 3 suggest that in addition to the dietary factors examined, other factors, such as the immune status of the animal, the level of 'background' pathogenic challenge and the physical environment were implicated in the pathogenesis of PWD.