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Revista MVZ Córdoba

Print version ISSN 0122-0268

Rev.MVZ Cordoba vol.22 no.1 Córdoba Jan./Apr. 2017

https://doi.org/10.21897/rmvz.921 

Originales

Effect of stocking rate and floor types on performance, skin temperature and leukogram in pigs raising

Efecto de la carga animal y el tipo de piso sobre el rendimiento, la temperatura de la piel y leucograma en la cría de cerdos

Diovani Paiano1  * 

Ivan Moreira2 

Arley R.B. Quadros3 

Natalia Cristina Milani1 

Maria Luisa A. Nunes Z1 

Gustavo Machado4 

Aleksandro S. Da Silva1 

1 Universidade do Estado de Santa Catarina, Department of Animal Science, 89815-630, Brazil.

2 Universidade Estadual de Maringá, Department of Animal Science, Brazil.

3 Universidade Federal de Santa Maria, Department of Animal Science, Brazil.

4 Federal University of Rio Grande do Sul, Veterinary Epidemiology Laboratory, Department of Preventive Veterinary Medicine, Porto Alegre, RS, Brazil.


ABSTRACT

Objective.

The aim of this study was to evaluate the performance, thermoregulatory characteristics and the leukogram of growing finishing pigs reared in different stocking rates kept on compact floor pens or with shallow pool pens.

Material and methods.

Thirty-six pigs were used in two steps (total of 72 animals were used). In the first step it was analysed performance pig (daily feed intake, weight gain and feed: gain ratio) and backfat thickness (P2). In the second step, the same analyzes were repeated, in addition, analysis of leukogram and skin temperature was performed in P2 and anal region, at the end of growing and finishing phase.

Results.

It was evaluated for differences between treatments and stocking. It was not found effect of floor type on growing phase, but the use of shallow pool had a negative effect on the gain and feed: gain ratio in the finishing phase, as well as lower surface temperature in the anal region on treatment with shallow pool in the finishing phase. No effect of treatments and type of floor on pig leukogram. Allowing more space/animal decreased backfat thickness. The use of shallow pool affected negatively the performance in the finishing phase.

Conclusions.

The shallow pool uses impair the finishing pig performance, despite improving thermolysis, with no effect observed on cell immune response.

Key words: Bioclimatology; feed; gain ratio; thermoregulation (Source: CAB, MeSH)

RESUMEN

Objetivo.

El objetivo de este estudio fue evaluar el rendimiento, las características de termorregulación, y el leucograma de cerdos de engorde, criados en diferentes densidad mantenidos en corrales de piso compactos o corrales con lámina de agua.

Material y métodos.

Treinta y seis cerdos se utilizaron en dos etapas (un total de 72 animales utilizados). En el primer paso, se analizaron las características zootécnicas (consumo diario de alimento, ganancia de peso y la conversión alimenticia) y el espesor de grasa dorsal (P2). En el segundo paso, los mismos análisis se repitieron, además, el análisis de leucograma y temperatura de la piel se realizó en P2 y la región anal, al final de la recría y terminación.

Resultados.

Se evaluaron las diferencias entre los tratamientos. No se encontró efecto del tipo de corrales en fase de recría, pero el uso de los corrales con lámina de agua tuvo un efecto negativo sobre la ganancia y conversión alimenticia en la fase de terminación, así como una menor temperatura de la superficie en la región anal en el tratamiento con lámina de agua en la fase de terminación. No hubo efecto de los tratamientos y tipo de corales sobre el Leucograma de los cerdos. Permitiendo más espacio/animal disminuyó el espesor de grasa dorsal. El uso de la lámina de agua afectó negativamente al rendimiento en la fase de terminación.

Conclusiones.

El uso de lámina de agua afectó el rendimiento de los cerdos de terminación, a pesar de la mejora de termólisis, sin efecto visible en la respuesta inmune celular.

Palabras clave: Alimento; bioclimatology; ganancia; termorregulación (Fuente: CAB, MeSH)

INTRODUCTION

Compared to other domestic species, pigs are more sensitive to high temperatures. The pigs have not functional sweat glands, had double layer of fat and smaller contact area with the environment when the animals reach mature age 1. In addition, breeding pigs are selected for high deposition of lean tissue and high performance, what ends up selection animals with intense metabolism and greater sensitivity to heat 2. These characteristics, when combined with the confined production systems, may result in losses to thermoregulation, with consequent damage to performance, animal welfare and greater emission of odors and ammonia 3.

At the same time, the reduction in performance, heat and social stress can depress the pig’s health 4. In this sense, the high ambient temperatures associated with the intensification of pig production lead to the need to develop alternative systems to mitigate the production problems related to heat stress.

The use of pens with shallow pool is one way to mitigate the problems related to high temperatures; it can facilitate heat loss by evaporation from the wet skin, conduction and convection 1. However, in this system the animals may be more susceptible to etiologic agents due to greater contact with the feces 5, which can be higher when the shallow pool pens are interconnected.

A thermally favorable environment makes the animal capable of maintaining its healthiness, consume and absorb nutrients properly 6. However, immunological activation cans changes in the requirements and relationships between amino acids and reduction in the growth rate and muscle tissue synthesis 7, with a reduction up to 70% of the productive potential 8.

A recent study found lower deposition of dust and less accumulation of organic matter in pens with shallow pool, features that can be beneficial in terms of air quality of the facilities 9. The presence of excess powder, and gas in installations create problems in cellular defense mechanism because overwhelm the phagocytic activity of macrophages. Besides the fact, many particles when suspended for possessing biological activity (such as endotoxin) can induce ciliostasis or direct toxic effect on the hair cells with damage to the mucociliary defense mechanism 10. However, the same research group stresses that the presence of shallow pool can be a detrimental factor for air quality, as the highest concentration of gases inside facilities 10.

Despite the described health challenges, the use of this system meets the natural habits of the species with the habit of wallowing, important behavioral pattern in thermoregulatory processes of swine 11. However, the daily water exchange of the shallow pool can increase the dilution of waste 12; which leads to the actual desrecommendation. Although the use of shallow pool pens without water renewal is common in swine production in south of Brazil.

We point out that the number of researches on the subject is small and sometimes do not studied all the variables or diversification that may exist in shallow pool system. One of these aspects is the smallest water renewal of the pool, aiming at reducing the dilution of waste and a consequent improvement in the environmental aspect of the system. Another important variant is adopted stocking rate, aspect that can greatly impact the performance of production systems and scientific exploration does not exist when it comes to the shallow pool systems. Therefore, this study aimed to evaluate the growth performance, carcass traits, thermoregulatory and immunological aspects of pigs kept pens with shallow pool or compact floor pens at different stocking rates.

MATERIAL AND METHODS

Site of study. The study was conducted in an experimental pig farm (23°25›S, 51°57›W at an altitude 542 m). In this study, it was used 72 pigs (36 barrows and 36 gilts), with initial weight of 35.1±4.9 kg, from high-lean commercial line.

Pens (4x2 m) had semi-automatic feeders (feeders with two accesses 0.35 m) in front of the pen (area of 0.4 m2) a drinking (nipple type) at the back. The shallow pool located at the back of pens (0.8 m wide and 0.1 m deep), as described by Moreira et al 1. To compact floor treatment, shallows pool were covered with wooden pallets, called compact floor treatment. Treatment with shallow pool, the water channels at back pens were kept under running water. Shallow pool area were drained, washed and filled with clean water twice a week (Mondays and Thursdays). In compact floor treatment, area at the back pens was cleaned and dried daily.

Experimental design and analysis. Experiment was carried out in two phases, consisting of three group sizes (2, 4 and 5 pigs/pen representing stocking rates 3.0; 2.0 and 1.5 m² of total area of compact floor available per pig, respectively). Were used, two types of surface (with or without access to shallow pool), and two blocks (according to gender barrow and gilt) by treatment, and initial weight, with 36 animals per step and two steps.

In the first step, growth performance (feed intake, daily gain and feed: gain ratio) was analyzed, in addition to fat thickness at position 2 (P2). In second phase, the same analyzes were repeated and added further analysis as leukogram (held at end of the experiment) and skin temperatures at the end of the growing and finishing phase.

Air temperatures and relative humidity were collected daily in a Weather Station located 50 meters from the experimental facilities (Table 1). To measure the surface skin temperatures, the air temperature in the days of collection, were 24.8 and 21.8ºC, for growing and finishing phase, respectively.

Table 1 Air temperature and relative humidity (maximum and minimum) and average precipitation recorded in experimental period. 

Phases Temperature, ºC Relative humidity, % Precipitation mm
max min max min
First step
Growing 27.7 ±3.6 17.5 ±3.0 76.5 ±15.3 57.1 ±17.2 4.1 ±11.4
Finishing 28.7 ±2.8 18.9 ±2.0 82.6 ±10.4 60.3 ±16.1 5.0 ±8.2
Second step
Growing 24.5 ±3.6 15.0 ±3.8 71.3 ±11.1 50.8 ±14.6 2.6 ±12.1
Finishing 23.5 ±4.7 12.1 ±4.1 73.0 ±16.4 50.4 ±16.5 1.8 ±4.2

Diets were fed ad libitum, and formulated based on corn and soybean meal with the use of specific basemix for each phase, having the following percent composition: 72, 24 and 4% for corn, soybean and basemix for growing phase, respectively. In the finishing phase, the percent composition was 79, 18 and 3% for corn, soybean meal and basemix, respectively.

Daily intake (DI), daily weight gain (DWG), feed: gain ratio (FGR) and backfat thickness were evaluated at the end of the growing and finishing phase. Backfat thickness (P2) by Sono-Grader (Renco®) apparatus was performed. Statistical analysis were performed to the DFI, DWG, FGR and P2 with the pens as experimental unit. For the other variables, each pig was considered an experimental unit.

In second step of the study, at the end of the finishing phase was harvest 2 mL of blood by cranial vena cava puncture of two animals per pen, to perform white blood cell count, which was used in Vacutainer® tubes (EDTA). Leukocyte count was done manually in Neubauer chambers 13. Blood smears were prepared and stained by the Romanowski method for evaluation of differential leukocyte.

Statistical analysis. Data were evaluated according to the statistical model:

Yijk = µ+Ti+Dj+ eijk,

in which: µ = mean, Ti = effect of floor type, Dj = effect of stocking density, and eijk = random error.

Polynomials were tested until the first order, and it was used the statistical package SAEG, 2007. For the skin temperature analysis and leukocytes were implemented in the model the effect of sex. Data for white cell count was tested by Shapiro Wilk for normality, and did not present the requirements of parametric analysis, so we used nonparametric approach by Kruscal Wallis, which was considered as a random effect sex, and as fixed effect of floor and stocking density.

RESULTS

Performance and carcass: In this study, there were no differences between the first and second steps (p>0.05). There was no interaction between stocking rate and floor type, and there was no effect on growth performance in the growing phase (p>0.05). In addition, there are no effects of floor type in P2 (p>0.05). We found lower gain and worst feed efficiency of pigs (p<0.05) with the use of shallow pool in the finishing phase (Table 2). Stocking rates did not influence (p>0.05) on the performance of pigs (Table 3).

Table 2 Growth performance of pigs in different stocking rates and floor types: initial weight (Kg), growing weight (Kg), finishing weight (Kg), daily feed intake (Kg), daily weight gain (kg), feed:gain ratio and backfat thickness (mm). 

Floor tipes Stocking rates, animals/pen Effect*
Phases Compact Shallow pool 2 3 4 D P D*P
Initial weight, kg 34.86 35.04 34.84 34.50 35.52 - - -
Growing weight, kg 59.46 60.34 59.21 59.24 61.25 - - -
Finishing weight, kg 88.98 86.90 86.53 88.74 88.55 - - -
Growing
Daily feed intake, kg 0.781 0.801 0.773 0.785 0.815 ns ns ns
Daily weight gain, kg 2.037 2.142 2.157 2.061 2.051 0.22 ns ns
Feed:gain ratio 2.62 2.68 2.79 2.63 2.53 0.15 ns ns
P2, mm 9.3 9.2 8.6 9.4 9.8 L<0.05 ns 0.21
Finishing
Daily feed intake, kg 2.632 2.629 2.608 2.714 2.570 ns ns 0.33
Daily weight gain, kg 0.896 0.804 0.828 0.892 0.830 ns <0.05 ns
Feed:gain ratio 2.95 3.27 3.18 3.05 3.10 ns <0.05 ns
P2, mm 13.2 12.7 11.9 13.0 13.8 L<0.05 0.30 ns
Growing and finishing
Daily feed intake, kg 2.341 2.392 2.391 2.397 2.313 ns ns ns
Daily weight gain, kg 0.839 0.804 0.801 0.842 0.822 0.14 0.19 ns
Feed:gain ratio 2.79 2.98 2.99 2.85 2.81 ns 0.07 0.29
*D= Stoking rate (linear effect); P= Effect of floor type; D*P= Interaction stoking rate and floor type.

Table 3 Skyn temperatures in the back (P2) and the anal area in pigs housed in shallow pool or compact floor in different stocking rates. 

Region Floor Types 1 Sex Stocking rates, animal/pen Effects 2
CF SP 2 3 4 P S D*P
Skyn temperature in growing, ºC.
P2 32.2 31.0 31.6 31.6 32.2 32.3 30.9 0.10 ns 0.09
Anal 32.9 32.2 32.3 32.8 32.6 32.5 32.6 0.30 0.3 ns
Skyn temperature in finishing, ºC.
P2 39.8 39.1 39.9 39.0 38.3 39.8 39.7 ns ns 0.31
Anal 39.2 36.9 38.2 37.8 39.0 38.0 37.6 <0.05 ns 0.18
1 CF= compact floor, SP=shallow pool pen; 2P= Effect of floor type; S= Effect of sex; D*P= Interaction density and floor type.

This experiment showed lower (p<0.05) backfat thickness in pens with more space per pig.

Skin temperature and leukogram: There were no differences (p>0.05) for the skin temperature in P2 and anal region in growing phases. Temperature in the anal region at the end of the finishing phase (Table 3) was lower in shallow pool treatment (p<0.05).

In leukogram analysis was not possible to reject any null hypothesis, so there was no difference (p>0.05) obtained leukocyte count in the blood, so the numbers of neutrophils, lymphocytes, eosinophils, and monocytes were not affected by treatments and stocking rates (Table 4).

Table 4 Leukogram of pigs housed in pens with shallow pool or compact floor in different Stocking rates. 

Variables, µL Type of floor Sex Stocking rates, animal/pen Effects 2
CF SP 2 3 4 P S D*P
Leukocyte 9000 10100 9300 9800 9200 9800 9700 ns ns ns
Rod 114.3 115.3 78.0 134.9 88.4 72.2 179.5 ns ns ns
Neutrophil 2637.9 3570.4 3440.5 2963.1 2839.2 2826.3 3680.5 ns ns ns
Eosinophil 278.6 277.3 187.7 327.2 418.2 229.0 210.0 ns ns ns
Basophil 68.6 31.1 73.5 35.3 48.2 66.8 31.2 ns ns ns
lymphocyte 4874.8 5844.6 4385.0 5935.4 5613.4 6284.8 4303.8 ns ns ns
monocyte 215.6 161.1 125.2 220.4 120.2 163.3 265.7 ns ns ns
1 CF= compact floor, SP=shallow pool pen; 2D=The density linear effect; P= Effect of floor type; D*P= Interaction density and type of floor.

DISCUSSION

Performance and carcass: Performance result in this study (Table 2) differ from those obtained by Moreira et al 1, found best results for pigs housed in pens with shallow pool during the growing. However, in this study the authors report the water of “shallow pool” was renewal daily, different from the present study, in which the renewal was performed twice a week.

Difference in the results of DWG and FGR between the phases of growing and finishing may be associated with the combination of two factors. In the finishing phase is greater demand for shallow pool, a result of increased sensitivity to heat this stage of life 1,2. Moreover, in the final phase is higher feed intake, and consequent increased production of waste, which increases the challenge of thermoregulation and health for this phase.

Lower performance in the treatment with shallow pool (Table 3), may also be associated with other factors such as shorter shelf/animal space (because pigs do not use the area with shallow pool to sleep, especially in situations of thermal comfort or cold stress), and the most contact with waste and consequently worse health status 5. Likewise, Kich et al 14 reported that increased contact with the waste into pens with shallow pool, is a factor associated with increased serological prevalence of Salmonella in pig farms. Moreover, Oliveira et al 15 found no relationship between the uses of shallow pool with increased prevalence of Salmonella.

Stocking rates did not influence on the performance of pigs. However, according to NRC 16 the area for pigs must be at least 1.1 m2 for animals over 50 kg body weight, and low space/pigs may cause decrease in productive performance. It should be noted in the experimental pens, the treatment with shortest space/pig (1.5 m2/pig) there are values greater than normally recommended and contributed to the similar results in performance between the different densities.

Backfat thickness for pigs in pens with more space (m2/pig) was lower and can be explained the larger space may have favored exploratory behavior and increased physical activity or less stimulus for consumption because the smaller size of the group and as a result less fat deposition. Similar results were obtained by Lunen 17 in an experiment with compact floor and slatted floor in different densities for weaning piglets to 25 kg, being observed lower depth of fat in piglets with the largest area available. However, differ of other studies with a pool, in which no differences were found in P2 1,18.

Skin temperature and leukogram: Temperature in the anal region at the end of the finishing phase (Table 3) showed lower in shallow pool treatment. Differences of these results between the phases may be related to the factors previously discussed, with more thermosensibility of animals in the finishing phase, which leads to increased demand for water in order to skin wetting for favoring thermoregulation. According to literature, the temperature of the skin can be a physiological indicator of heat stress in pigs 19, suggesting improved thermal comfort for the pens with water.

Absence of floor effects in the temperature in the P2 region was similar to the results observed by Biazzi et al 9 and may be linked to problems with wetting the dorsal region, given the low depth of water in shallow pool, and the lowest blood supply in the region P2 when compared to the anal area.

In Leukogram analysis was not possible to reject any null hypothesis, so there was no difference (p>0.05) obtained leukocyte count in the blood, so the numbers of neutrophils, lymphocytes, eosinophils, and monocytes were not affected by treatments and stocking rates (Table 4). The air quality related to the concentration of gases such as ammonia, H2S and CO2, can be worsened in shallow pool pens systems and result in damage to the protective mechanisms of the lower airways and alveoli, mucus cleaning-ciliar and the activity of alveolar macrophages 10. Moreover, Biazzi et al 9 observed less dirt and dust accumulation in the compact part of the pens, with the use of shallow pool, which could have benefited the air quality. Thus, the combination of a lower concentration of gases in compact floor and lower dust in the pens with shallow pool may have contributed to the lack of difference regarding the number of leukocytes.

Finally, it can be concluded pig production in low stocking rates, regardless of the floor type decreased fat thickness. Keeping pigs in pens with shallow pool, washed and filled with clean water just twice a week, reduced growth performance in the finishing phase, although it improve the thermal comfort, evidenced by lower skin temperature values in the anal area.

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Received: October 2015; Accepted: June 2016

* Correspondence diovani@hotmail.com

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