| Summary: | 碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作系 === 105 === In a bid to achieve food security with the increasing world population, commercial pig producers aim for high lean content or increase number of surviving piglets to slaughter in a farm. The abrupt changes experienced by piglets in the modern weaning practice jeopardise production performance as it leads to growth checks or even death in extreme cases. Post-weaning growth check, caused by reduced or zero feed intake at weaning, is an economic and welfare concern. Following inconsistent conclusions from available literature pertaining effects of weaning weights on growth performance in piglets at weaning, it was hypothesised that weaning weight variation within a litter has high influence on growth check intensity. Relative growth check intensity in this study was defined as the degree of reduction in relative average daily gain (ADG) on day 2 post-weaning as a percentage of relative ADG of the last week pre-weaning. Relative ADG was defined as daily weight gain (grams/24hrs) expressed as percentage of initial bodyweight (kg). The objective of this research was to verify the effects of weaning weights on growth check intensity during the first week post-weaning. Three experiments were conducted, using a total of 56 weaned piglets, to determine any significant differences in post-weaning growth check intensity between heavy and light piglets. Using 12 healthy piglets which were crosses of Landrace, Large White and Duroc, weaned at 28 days, the first experiment investigated the effects of body energy reserves on growth check of pre-weaning. General behaviour for energy balance was observed in heavy (7.65 ± 0.38 kg) and light (6.47 ± 0.42 kg). A total of 5 males and 7 females were distributed within the 2 groups of heavy and light piglets. Animal growth performance was expressed in terms of relative ADG and relative growth check intensity. Heavy piglets significantly had high relative ADG (p < 0.05). Body energy reserves were determined by measuring relative blood glucose concentration. Relative blood glucose concentration was expressed as percentage of initial glucose concentration. There were significant differences (p < 0.05) in blood glucose concentration with less glucose concentration in heavy piglets from day 0 – 4. Blood glucose was not sufficient to explain body energy reserves, so behaviour for body energy balance was examined. Weaning weights affected energy intake (p < 0.01), conservation (p < 0.001) and expenditure (p < 0.05) frequencies but not energy elimination (p > 0.05. Body size affected growth check intensity with heavy piglets experiencing low growth check intensity than light piglets. As another factor thought to contribute to growth check intensity, instinctive learning ability to eat after weaning was assessed in experiment 2 by using 12 piglets grouped into heavy (11.10 ± 0.32 kg) and light (7.64 ± 0.73 kg) experimental groups. Instinctive learning behaviour was observed for 7 days post-weaning in 12 continuous hours per day (7:00a.m. - 7:00p.m.). In each group there were 3 castrated males and 3 females to make 6 animals per group. Again, relative ADG and growth check intensity were used to estimate animal growth performance. There were no significant differences (p > 0.05) in both relative ADG and relative growth check intensity between heavy and light piglets weaned at 35 days of age. However, heavy piglets significantly had high feed intake (p < 0.001) because they needed more energy to maintain their body weight. Heavy piglets significantly had shorter time to start eating (p < 0.01), allowing them to have significantly high eating frequency (p < 0.01) yielding to significantly high eating time and shorter meal intervals per given 12-hr day. Thus, weaning weights affected instinctive learning ability with heavy piglets being better learners. This proved that even without transition, piglets can learn to cope with weaning stress in a given environment. Effects of weaning weights on conditioning learning ability to eat was assessed by conditioning piglets to creep feeding in experiment 3. This experiment used principles of classical conditioning. In a 2 x 2 factorial design, 32 Meinung piglets with 17 castrated males and 15 females were used in this study. Grouping by weaning weights was used as main factor to form heavy and light piglet groups. Two creep feeding levels (with or without creep feed) was used as a within group factor. ‘Without creep feed’ piglets were control groups that were not conditioned for hourly creep feeding. At 28 days of age ‘with creep feed’ piglets were conditioned to eat creep feed at hourly intervals during the last week pre-weaning. At weaning (35 days of age), all four experimental groups were tested on feeding behaviour highlighting latency to start eating, meal duration, daily eating duration and eating frequency. Each trial lasted for 0.5hr with 1hr feed withdrawal periods making 5 trials per day. Weaning weights alone had no significant (p > 0.05) effects on relative ADG and growth check intensity. Creep feed conditioned piglets did not suffer growth check. Within group effects, weaning weights significantly affected growth check intensity in which light pigs had high growth check intensity (p < 0.001) because they were not habituated to creep feeding and low body energy reserves. Increase in weaning weights reduced growth check intensity. Heavier body weights improved conditional reflex learning ability in piglets. A feeding regime offering creep feed gives piglets the possibility to cope better with transition at weaning.
|
|---|
