Genetic selection modulates feeding behavior of group-housed pigs exposed to daily cyclic high ambient temperatures

This study was conducted to evaluate the effect of genetic selection (Lines A and B; Line A pigs have a greater proportion of Pietrain genes than those from Line B and therefore, selected for improved lean tissue accretion) on the feeding behavior of group-housed pigs exposed to daily cyclic high ambient temperatures. Feeding behavior of 78 barrows housed together in a single room was recorded in real time by five automatic feeders. The feeders registered each visit of each pig (day, hour, min, and second) and the amount of feed requested. Daily cyclic high ambient temperature was induced exposing pigs at 22˚C from 18.00 to 10.00 h and 30˚C from 10.01 to 17.59 h. From this temperature variation, dayperiod was divided into: 22˚C(06-10h), from 6.00 to 10.00 h; 30˚C(10-18h), from 10.01 to 17.59 h; and 22˚C(18-06h), from 18.00 to 5.59 h. Meal criteria was estimated based on the probability of animals starting a new feeding event within the next minute since the last visit (Pstart). After defining the meal criteria, the number of meals (n), feed intake rate (g/min), feed intake (g/meal), feeder occupancy (min/meal), and interval between meals (min) of each animal were calculated. Greatest probability of starting to feed was observed at 22˚C(06-10h), followed by 30˚C(10-18h) and then 22˚C(18-06h). Regardless of time period, pigs from line A had greater feed intake rate and lower feed intake, feed occupancy per meal and probability of starting a meal when compared with line B pigs. Only line A pigs had greater feed intake and feeder occupancy per meal at 22˚C(18-06h) than remainder of the day. This indicates that pig feeding pattern is strongly related to the circadian rhythm. However, the genetic selection for improved lean tissue accretion may modulate pigs feeding behavior under daily cyclic high ambient temperatures

Sequential feeding with diets varying in amino acid content for growing-finishing pigs

This study aimed to evaluate the effects of daily phase feeding (DP) and sequential feeding (SEQ) on the feeding behavior, performance, and body composition of growing-finishing pigs. Sixty barrows at 29.7 ± 2.8 kg body weight (BW) were assigned to one of four treatments: DP with a blended proportion of feeds A (high nutrient density) and B (low nutrient density) was adjusted to match 100 % of daily amino acid (AA) diet recommendations (DP100); a negative treatment, which matched 70 % of daily AA diet recommendations (DP70); and two SEQ with a blend of feeds A and B, adjusted twice a day (at 00h00 and 12h00), to match 70 or 110 % of daily AA diet recommendations during two 12 h intervals: SEQ110-70 and SEQ70-110. DP70 and SEQ showed a lower feed consumption rate compared to DP100 (p < 0.05). Compare to DP100, pigs in both SEQ programs had a similar average daily feed intake (ADFI), average daily gain (ADG), feed efficiency ratio (G:F) and body fat and lean mass ( p > 0.05). SEQ110-70 and SEQ70-110 showed similar ADFI, ADG, G:F and body lean mass (p > 0.05). However, fat gain was greater in SEQ110-70 than in SEQ70-110 (p < 0.05). Overall, the SEQ program does not improve performance and body composition. Furthermore, feeding pigs a diet with a higher AA level during the first 12 h of the day and a lower AA level during the remainder of the day increases fat deposition

Efeito da aclimatação a altas temperaturas em suínos selecionados para consumo residual

Trinta e seis suínos machos castrados, Large White, pertencentes a duas linhas genéticas divergentes no consumo alimentar residual, com peso inicial de 50,5 ± 0,9 kg e aproximadamente 92 dias de idade, foram utilizados para avaliar os efeitos da aclimatação ao calor no desempenho, nas respostas termorregulatórias e nos parâmetros sanguíneos de suínos selecionados para alto e baixo consumo residual. O experimento foi conduzido em dois ensaios consecutivos de 18 animais. O primeiro ensaio foi composto por dez animais pertencentes à linha de baixo consumo residual e por oito pertencentes à linha de alto consumo residual e, o segundo ensaio, foi composto por nove animais de cada linha genética. Os suínos foram alojados em uma sala climatizada na qual a temperatura ambiente foi mantida em 24,2 ± 0,4oC durante os primeiros sete dias do experimento e, posteriormente, mantida em 30,4 ± 0,7oC durante 14 dias. O aumento da temperatura da sala ocorreu no oitavo dia do experimento em um intervalo de tempo de três horas. Os animais foram pesados no início, no oitavo e no vigésimo primeiro dia do experimento. O consumo de ração foi determinado diarimente com base na diferença entre a quantidade de alimento fornecido e a quantidade de sobras. Animais com baixo consumo alimentar residual consumiram menos ração, tiveram menor consumo metabólico, melhor eficiência alimentar e ganho de peso similar aos animais de alto consumo alimentar residual. O consumo de ração diário, consumo metabólico de ração, ganho de peso diário e a eficiência alimentar diminuíram no ambiente de calor. A temperatura retal não foi influenciada pela linha genética, no entanto foi maior a 30oC. A temperatura cutânea e a freqüência respiratória não diferiram entre as linhas genéticas em ambiente termoneutro, no entanto, foi observado um aumento desses parâmetros com o aumento da temperatura ambiental, sendo este aumento superior na linha de alto consumo alimentar residual. Maiores valores de freqüência cardíaca foram observados em animais de alto consumo residual e tanbém em ambiente termoneutro. Amostras de sangue foram coletadas, por meio de cateteres, para mensurar os hormônios tireoidianos, glicose, glicerol, &#945;-aminoácidos, lactato, hematócrito,insulina, IGF-I e leptina. A concentração plasmática de lactato foi superior nos animais de alto consumo residual. Maiores níveis de insulina e menores níveis de hormônios tireoidianos foram observados em ambiente de calor em ambas linhas genéticas. Conclui-se que os efeitos negativos das altas temperaturas ambientais são menos pronunciados em suínos de baixo consumo residual e que estes necessitam de uma menor ativação dos mecanismos termorregulatórios para manter a homeotermia em ambiente de calor quando comparados à suínos de alto consumo residual.Thirty-six Large White castrate males belonging to two divergent lines in residual feed intake, with average initial body weight of 50.5 ± 0.9 kg and approximately 92 days of age, were used to evaluate the effects of acclimation to high temperature on the performance, thermoregulatory responses and blood parameters of pigs divergently selected for low and high residual feed intake. The experiment was conducted in two successive replicates of 18 animals each. The first replicate was composed by ten animals with low residual feed intake and eight animals with high residual feed intake and, the second one, was composed by nine animals of each line. Pigs were housed in a climatic-controlled room where the ambient temperature was maintained at 24.2 ± 0.4oC during the first seven days and thereafter at 30.4 ± 0.7oC during 14 days. The temperature change was achieved over three hours on the eighth day of the experiment. Pigs were individually weighed at the beginning, on the eighth and on the twenty-first day of the experiment. Feed intake was daily determined by the difference between the feed allowance and refusals. Low residual feed intake pigs consumed less feed (P0.05) than high residual feed intake pigs. Average daily feed intake, metabolic average daily feed intake, average daily gain, and gain:feed ratio were lower (P0.05), whereas it was higher (P<0.001) at 30oC. Cutaneous body temperature and respiratory rate were similar for both lines at termoneutrality and increased with the ambient temperature increase, with a higher increase being observed in the RFI+ line (P<0.001). Heart rate was higher (P<0.05) in RFI+ line and higher (P<0.001) at 24oC. Blood samples were collected via catheters to measure thyroid hormones, glucose, glicerol, &#945;-amino acids, lactate, hematocrit and plasma concentrations of insulin, IGF-I and leptin. Plasma lactate concentration was higher in RFI+ pigs than in RFI- (P<0.01). Higher levels of insulin (P<0.05) and lower concentration of thyroid hormones (P<0.001) were observed at high ambient temperatures. In conclusion, this study suggests that RFI- pigs tended to be less negatively affected by high ambient temperature and also require a lower activation of thermoregulatory mechanisms to maintain homeothermy in hot conditions than RFI+ pigs

Physiological responses of growing pigs to high ambient temperature and/or inflammatory challenges

ABSTRACT Global warming is one of the major environmental threats facing the world in the 21st century. This fact will have a significant impact on pig production due to its direct effects on welfare, health, and performance of pigs. Besides, the effects of high temperatures will presumably become more important over the next decades due to the development of pig production in developing countries mainly located in tropical and subtropical areas, where animals are often exposed to ambient temperatures above their thermal comfort zone. Furthermore, pigs reared in tropical areas are often confronted to sanitary challenges including poor hygiene conditions, lack of respect for sanitary rules, and pathogens. This results in the stimulation of the immune system and, as a consequence, in the production of pro-inflammatory cytokines and neuroendocrine adjustments that, in turn, usually have a negative impact on growth and feed efficiency. Although the effects of high ambient temperature and disease on pig physiology and performance have been well documented in literature, little is known about the associated effects of both factors. This understanding may contribute to a better quantification and comprehension of the physiological and metabolic disturbances occurring in practical conditions of pig production in tropical areas and, more generally, in many other geographic areas that will be influenced by the perspective of global warming. Therefore, the objective of this work is to provide an overview of recent research advances on the physiological responses of growing pigs during acclimation to high ambient temperature and on the potential effects of high ambient temperature on the ability of growing pigs to resist, cope with, or recover from an inflammatory challenge

Modulatory effects of housing conditions on energy related metabolites and insulin in pigs divergently selected for residual feed intake

The ability of pigs to cope with a health challenge may depend on their ability to adapt their metabolism. The purpose of this study was to assess the impact of housing conditions on postprandial energy metabolism in growing pigs from two lines divergently selected for residual feed intake (RFI). The trial was based on a 2×2 factorial design (n=6/group) including low-RFI (LRFI) and high-RFI (HRFI) pigs housed in two contrasted hygiene conditions (Clean vs Dirty). After a 6-week challenge period, blood samples were collected during a 4-hour period after a test meal to measure insulin and energy related metabolites. Housing conditions did not affect average concentrations of insulin and energy related metabolites. Average plasma concentrations of insulin were greater and that of triglycerides were lower in LRFI than in HRFI pigs whatever the housing conditions. For these two variables and glucose, the two lines exhibited significant differences in postprandial profiles. Whether this may be related to a different partitioning of energy related nutrients deserves further investigations

Postprandial insulin and nutrient concentrations in lipopolysaccharide-challenged growing pigs reared in thermoneutral and high ambient temperatures

The aim of this study was to evaluate the associated effects of ambient temperature and inflammation caused by repeated administration of Escherichia coli lipopolysaccharide (LPS) on insulin, energy, and AA metabolism. Twenty-eight pigs were assigned to one of the two thermal conditions: thermoneutral (24 °C) or high ambient temperature (30 °C). The experimental period lasted 17 d, which was divided into a 7-d period without LPS (days −7 to −1), and a subsequent 10-d LPS period (days 1 to 10) in which pigs were administered 5 repeated injections of LPS at 2-d intervals. Postprandial profiles of plasma insulin and nutrients were evaluated through serial blood samples taken on days −4 (P0), 4 (P1), and 8 (P2). Before the LPS-challenge (P0), postprandial concentrations of glucose, lactate, Gln, Ile, Leu, Phe, Tyr, and Val were greater in pigs kept at 24 °C than at 30 °C (P < 0.05). In contrast, Arg, Asp, Gly, His, and Met postprandial concentrations at P0 were lower at 24 °C than at 30 °C (P < 0.05). At both 24 and 30 °C conditions, pigs had greater postprandial concentrations of insulin (P < 0.01) and lower concentrations of NEFA (P < 0.01) and α-amino nitrogen (P < 0.05) at P1 and P2 than at P0. Compared with P0, postprandial concentrations of glucose were greater (P < 0.05) at P1 in pigs kept at 24 °C, and at P1 and P2 in pigs kept at 30 °C. At both ambient temperatures, pigs had lower (P < 0.05) postprandial concentrations of Ala, Gly, His, Ile, Leu, Pro, Ser, Thr, Trp, and Val at P1 and P2 than at P0. Arginine postprandial concentration at P1 was lower than at P0 in pigs kept at 24 °C (P < 0.05), whereas no difference was observed in pigs at 30 °C. Relative to P0, Gln and Tyr concentrations were lower at P1 and P2 in pigs kept at 24 °C (P < 0.01), whereas lower Gln concentration was observed only at P2 (P < 0.01) and lower Tyr only at P1 (P < 0.01) in pigs kept at 30 °C. Our study shows a hyperglycemic and hyperinsulinemic state in LPS-challenged pigs and a greater magnitude of this response in pigs kept at 30 °C. Furthermore, LPS caused important changes in BCAA, His, Thr, and Trp profiles, suggesting the role these AA in supporting the inflammatory response. Finally, our results suggest that LPS-induced effects on postprandial profiles of specific AA (Arg, Gln, Phe, and Tyr) may be modulated by ambient temperature

Effects of lipopolysaccharide-induced fever on metabolic heat production

Fever is one of the most common clinical signs of infection and systemic inflammation and is an important component of non-specific acute phase response. However, its activation results in increased metabolic rate and energy expenditure with negative consequences on animal growth and feed efficiency. This study aimed at investigating the effect of repeated administrations of Escherichia coli lipopolysaccharide (LPS) on the internal temperature of growing pigs and its associated impact on metabolic heat production. In response to LPS, internal temperature of the animals increased from 38.7 to 40 °C within 150 to 200 min after the LPS administration. The corresponding increase in maintenance energy requirements was estimated in 100 kJ/kg BW0.60/d which is equivalent to 10% of the basal metabolic rate of growing pigs

Selection for feed efficiency elicits different postprandial plasma metabolite profiles in response to poor hygiene of housing conditions in growing pigs.

This study was conducted to compare postprandial plasma concentrations of insulin, energy-related metabolites, and amino acids measured after a 6-week challenge consisting of exposure to good or poor hygiene of housing conditions of 24 growing pigs divergently selected for low-RFI (LRFI) and high-RFI (HRFI). Blood indicators of immune responses were assessed from samples collected before 0 (W0), and 3 (W3), and 6 weeks (W6) after pigs transfer to their respective hygiene of housing conditions. Plasma haptoglobin concentrations and blood neutrophil granulocyte numbers were greater in poor than in good hygiene of housing conditions at W3. Plasma concentrations of total immunoglobulin G were greater (p = 0.04) in poor than in good hygiene of housing conditions at W6. At W6, pigs were fitted with an intravenous catheter for serial blood samplings. Low-RFI pigs had greater insulin (p < 0.001) and lower triglyceride (p = 0.04) average plasma concentrations than HRFI pigs in both conditions. In poor hygiene of housing conditions, the peaks of insulin and glucose were observed earlier and that of insulin was greater in LRFI than in HRFI pigs. Irrespective of genetic line, average plasma concentrations of histidine, isoleucine, leucine, methionine, threonine, valine, and alanine were greater in poor compared with good hygiene of housing conditions. Only HRFI pigs had greater lysine, asparagine, proline, and tyrosine plasma concentrations in poor than in good hygiene of housing conditions. Conversely, arginine, tryptophan, proline, and tyrosine plasma concentrations were lower only for LRFI pigs housed in poor hygiene conditions. Our results suggest that, contrary to HRFI, LRFI pigs increase or maintain their utilization of tryptophan, arginine, and lysine when housed in poor hygiene conditions. This indicates that this difference may contribute to the better capacity of LRFI to cope with poor hygiene of housing conditions