Genetic lines and precision feeding system as a sustainable alternative for swine production in tropical countries

Author(s)

Luan Sousa dos Santos

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2019-03-11.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2019-02-05
• Advisor: Luciano Hauschild

Abstract

Developing countries, located in regions of predominantly warm tropical climate with little investment in infrastructure, expose animals to heat stress conditions. In turn, heat stress generates significant losses in animal production, especially for pigs, because of their limited ability to dissipate heat. In addition, the spread of disease vectors by heat also increases the challenges in swine farming. The investment for complete climatization of a facility can lead to an increased production costs and less competitive prices for the pig farmer. Because of this, the choice of an appropriate genetic linked to a good plan of nutrition become indispensable in the swine industry worldwide. Thus, with this thesis we aimed to evaluate the effects of heat stress first on different genetics. After defining the genetics most sensitive to heat stress, a second study was performed using two nutrition techniques (conventional and precision feeding) to evaluate the performance responses and body composition of the animals. In the first study the objective was to evaluate the robustness in the performance and body composition of progenies from two sire genotypes (G) commonly used worldwide (AGPIC 327: pure Hampshire and AGPIC 337: synthetic line) under heat stress (33 ºC). A total of 24 barrows (initial weight 32.0 ± 2.0 kg) were housed in individual pens and then submitted to one of two environments (AT), being thermoneutral at 22 ºC (TN) and high temperature at 33 ° C (HT). Feed intake and weight gain were evaluated weekly throughout the experimental period (55 days). The pigs’ body composition was assessed at 28 and 56 days of the experiment through a dual X-ray bone densitometry equipment. During days 0 and after each assessment of body composition, the back fat thickness and the muscle depth were also measured by an ultrasound equipment. As expected, animals submitted to heat stress reduced feed intake (35%; P < 0.01) in relation to the animals in the thermoneutral environment during both experimental phases (0-27 and 28-56 days). Also in a heat stress environment, synthetic line animals reduced their feed intake by 50%, while in Hampshire animals, this reduction was approximately 24% (P < 0.05 for G × AT interaction). On days 27 and 55, body weight, composition of lipids, phosphorus, and bone mineral content reduced (P < 0.05) in animals submitted to heat stress when compared to animals in thermoneutral environment. On these same days, under heat stress the back fat thickness was 26% lower in synthetic animals when compared to Hampshire (P < 0.10 for the G × AT interaction). Higher temperatures influenced both genetics evaluated. In this first study, it can be concluded that potential interactions between commercial lines and the environment might influence the performance and composition of pig carcasses in heat stress inversely as expected under thermoneutral conditions. The objective of the second study was to evaluate the responses of individual daily precision feeding (IPF) and conventional phase systems (CON) in terms of performance, nutrient balance, serum parameters and meal patterns of pigs raised under thermoneutral conditions ( TN: 23 °C) and heat stress conditions (HT: 30 °C). The animals in each treatment were distributed in the experimental treatments according to their initial weights (12 animals per treatment and 41.0 ± 4.87 kg body weight). The experiment lasted 55 days (phase I - 0 to 27 days and phase II - 28 to 55 days). The pigs in the CON group received at each phase a constant mixture of diets with high and low nutrient density, meeting the nutritional requirements of the group, while the IPF animals received daily a personalized mixture providing the estimated amount of nutrients. Bone mineral content, lean and fat mass were assessed by a dual X-ray bone densitometry equipment at the beginning and at the end of each phase. The data were analyzed including the following fixed effects: feed system (FS), ambient temperature (AT) and their interactions. The effects of AT were significant (P < 0.01), reducing daily feed intake by 28%, daily weight gain by 25%, protein gain by 14% and lipid gain by 14% in animals under HT compared to TN. In relation to CON treatment, IPF animals reduced their lysine intake (19%), protein intake (16%) and P intake (14%) without compromising (P > 0.05) the body composition. Nitrogen excretion was 24% lower (P < 0.05) in the IPF group when compared to CON pigs, with the same nitrogen retention efficiency throughout the experimental period. Feeding time, feed intake rate and feed consumption per meal were 15% lower (P < 0.05) in pigs raised under HT than under TN conditions. During the second growth phase, only feeding time, feed intake rate and feed consumption per meal decreased (P < 0.05) in pigs under HT conditions during the nocturnal and diurnal periods. Haptoglobin levels were affected by AT, showing a 70% and 43% increase in HT at 28 and 55 days of the experiment, respectively. The pigs raised under HT conditions presented a 10% lower serum albumin concentration (P < 0.05) at 55 days than those in TN conditions. For serum urea concentrations, animals in the IPF system presented 28% lower levels (P < 0.01) than the CON pigs. Although HT conditions have considerably reduced the growth of the animals and activated their inflammatory responses, it has been demonstrated that the IPF system is an excellent tool to achieve adequate nutrient utilization in both HT and NT conditions without compromising the animals' body composition. (AU)

• FAPESP's process: 15/05241-1 - Precision-feeding system as alternative for pig production in hot climate countries
• Grantee: Luan Sousa dos Santos
• Support Opportunities: Scholarships in Brazil - Doctorate