School of Agriculture, Food and Ecosystem Sciences - Theses
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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.