Desmame precoce em leitões: Estudo do desenvolvimento corporal, epigenética e comportamental

Abstract

The hyperprolificity of the female swine achieved through genetic improvement allows greater profitability for the producer due to the increase in the efficiency of the sow and the high number of piglets weaned/female/year. However, there is an imbalance between the greater number of piglets born and the sow's ability to meet the nutritional needs of her offspring. Therefore, challenges exist in the lactation phase, such as the demand of the female being greater than her physiological capacity to acquire nutrients. Therefore, early weaning combined with the use of milk substitutes become an alternative to compensate for this disparity. Therefore, the present study aimed to measure animal performance and behavioral and neuroendocrine changes in early weaned pigs, in order to measure the acceptability of this practice in terms of animal welfare. The thesis was divided into five chapters, the first referring to general considerations related to the theme, and the second related to the techniques and analyzes used in the work. In chapter three, the objective was to evaluate the productive performance of early weaning at ten days of age, and to compare it with conventional weaning on the farm at 21 days of age. The experimental design was in six randomized blocks with 24 repetitions, and two treatments. The control group was the conventional weaning used on the farm, at 21 days, and the treatment group considered early weaning at ten days of age. Weights from birth to the end of the farm's production cycle were evaluated, and in the slaughterhouse, carcass yield was analyzed. Piglets weaned at 21 days of age showed greater growth potential compared to animals aged 10 days, and the carcass of these animals showed greater muscle depth and weight. It is concluded that early weaning induced intense deleterious effects on the physiology and development of piglets. In chapter four, the behavior of the animals was evaluated by measuring lesions at weaning at ten days at different times, open field test and new object at 21 days, and time of loading the animals for transport to the slaughterhouse. The hippocampus was collected in the refrigerator and the epigenetic effects of the NR3C1 gene and the expression of stress-related genes were analyzed, namely NR3C1, NR3C2, FKBP5, HTR1A and BDNF. As a result, pigs weaned at ten days of age increased the amount of lesions and aggressiveness at 24 and 48 hours after weaning. In the open field and new object tests, these early weaned animals show greater habituation. Furthermore, there was no epigenetic alteration in the region of exon 1(7) of the NR3C1 gene, and there was no significant difference between the groups in the expression of the genes studied related to stress. It is suggested that it may have occurred due to maternal care until ten days of age were sufficient to not cause epigenetic and gene expression changes in the animals. The last chapter of this work refers to the final considerations, with the synthesis andperspective of the hyperprolificity of the female swine and the alternative managements for numerous litters.