Effects of Birth and Weaning Weight on Variation in Growth Performance Parameters and Carcass Characteristics and Composition of Pigs

119 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008.The objective of the work presented in this dissertation was to determine the effects of birth weight and weaning weight on pig growth performance, fat and lean tissue accretion rates, and carcass characteristics and composition. Study 1 was a retrospective analysis of data collected in two studies conducted under commercial conditions. Individual pig body weights were collected at birth, weaning, and 8 and 20 weeks post-weaning, and carcass data was also collected on individual pigs. The pigs were sorted by birth weight, and assigned to quartiles on the basis of birth body weight. The data were then analyzed as a completely randomized design with four treatments (birth weight quartiles). Study 2 evaluated the growth performance, fat and lean tissue accretion rates, carcass characteristics and composition, and meat quality of barrows with Heavy, Medium, or Light birth weights housed in individual pens from 3 weeks post-weaning to an end body weight of 145 kg. This study was conducted as a randomized complete block design with three treatments (Heavy, Medium, and Light birth weight) and the blocking factor was day of weaning. Study 3 was conducted as a randomized complete block design with a 2 x 2 factorial arrangement of treatments [Birth weight (Heavy vs Light) and Weaning weight (Heavy vs Light), and evaluated the same parameters as Study 2. Heavy weaning weight pigs were reared in litters of 6 pigs during lactation and Light weaning weight pigs were reared in litters of 12 during lactation. The results of these studies indicate that light birth weight pigs grow slower during the wean-to-market period compared to heavy birth weight pigs. The results of Studies 1 and 2 also indicated there is a threshold level of birth weight above which there is no improvement in overall average daily gain. This was evidenced by a much larger difference in growth rate between quartiles 1 and 2 than between the other quartiles in Study 1, and a lack of a difference in growth rate between medium and heavy birth weight pigs in Study 2. There was no difference observed in feed intake among the birth weight classifications in either Study 2 or Study 3 and the light birth weight pigs had less percentage lean of the carcass compared to the heavier birth weight pigs in both studies. Additionally, weaning weight had no effect on growth performance or carcass characteristics. The results of these studies indicate that light birth weight pigs grow slower than heavy birth weight pigs and the reduction in growth rate is due to less potential for lean tissue accretion.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD