Effect of Housing Design and Location on Production and Economic Performance of Broiler Chickens during Summer in Botswana

ABSTRACT Botswana experiences long, hot summer periods which negatively affect broiler productivity and results in economic losses. To determine these negative effects, two parallel broiler production studies were conducted in the North eastern (NE) and South eastern (SE) regions. In each region, three large scale commercial broiler farms were randomly selected based on similarities in bird management and housing systems. In each farm, one house type (Gable, Hoop and See-saw) was selected for long term flock monitoring (1 to 35 days) over three production cycles. Results showed that the production performance of the broilers in the SE region was superior to that in the NE region, with temperatures on being average higher in the NE than in the SE. The European Production Efficiency Factor (EPEF) was significantly higher (p<0.05) in the SE (209) than in the NE (174). In the NE region, the broilers reared in the Hoop structure performed significantly better (p<0.05) than in both the Gable and See-saw structures in regards to feed consumption, average daily gain, and water consumption. In the SE region, only water consumption was significantly higher (p<0.05) in the Gable structure as compared to the other house structures. At the point of slaughter (35 days), there were significant differences (p<0.05) between the bird masses across the different house types. Mortality was not significantly different (p>0.05) between the regions at 9.0% and 7.4% for the NE and SE, respectively. In the NE, the Gable structure had the highest profitability and economic efficiency and was thus superior in comparison to the other house structures.


INTRODUCTION
Studies involving commercial broiler chickens (Gallus gallus domesticus) show that housing (Dawkins et al., 2004) and environmental conditions (Zhao et al., 2014) affect bird welfare much more than the stocking density.From 26.7 ºC and above, chickens experience heat stress and begin to pant (Oloyo & Ojerinde, 2019).Panting results in reduced feed intake, body weight gain, meat quality, immunity and increased disease incidences (2014; Zhang et al., 2012;Bhadauria et al.), and these effects escalate with age.Increased relative humidity compounds these negative effects as it reduces evaporative cooling of the chickens through panting.For day old chicks, Katelaars (2005) recommended a temperature of 30-32 ºC, which should be reduced by 3-4 ºC until 4 weeks old.Growing broilers are comfortable at temperature range between 18-22 ºC (Daghir, 2008) and 18-24 ºC (Holik, 2015).
The summer period in Botswana occurs from October to March.Areas in the South east around Gaborone city (24°39'29'S and 25°54'44"E at 1,010 m above sea level) experience an average high summer temperature of 32.7 o C in January.On the other hand, the

Effect of Housing Design and Location on Production and Economic Performance of Broiler Chickens during Summer in Botswana
North eastern areas around Francistown city (21° 10' 24.9996'' S and 27° 30' 45.0036'' E at 1,010 m above sea level) experience an average summer hightemperature of 30.0 o C in November.In summer, the relative humidity ranges from 60 to 80% in the morning and drops to 30 to 40% in the afternoon.
Housing and management of broilers are designed to ensure optimum performance (Mesa et al., 2017).In tropical regions, naturally ventilated open housing systems, with dwarf sidewalls and chicken mesh along the open side walls, are common due to their simplicity, economic implications, and ease of heat generation management through natural ventilation (Oloyo & Ojerinde, 2019).Design considerations that take into account the orientation; house width, length and height; roof slope and overhang; ridge and sidewall openings, and insulation of walls and roofs are helpful in attaining better indoor conditions during the hot weather (Daghir, 2008;Clark, 2013).
In the past, the poultry industry used to focus on growth rate and feed conversion efficiency as measures of performance.Samarakook & Samarasinghe (2012) suggested that biological performance as well as economic parameters are important in the evaluation of real broiler performance then and in the future.Furthermore, they indicated that there are few indices that measure performance of broilers, with most only depicting the biological performance of the birds where they account for genetic potential, feed quality and technical efficiency of the farm.
The rising cost of poultry feed is a major concern to the development of the poultry industry in developing countries (Hagan, 2013).Kondo et al. (2015) and Karangiya et al. (2016) indicated that about 70% and 80%, respectively, of the total cost of poultry production is attributed to feeding costs.Hence, giving due attention to proper utilization of feed without adversely affecting the growth performance of broilers (Saiyed et al., 2015) is important, as feed constitutes the major input determining the profit margin (Kalia et al., 2017).
The main objective of any business enterprise is profit maximization.Various approaches have been used to assess the profitability and efficiency of broiler production units, including net return on investment and input-output analysis (Karangiya et al., 2016;Abdurofi et al., 2017), cost-benefit analysis (Adeyemo et al., 2016;Odeh et al., 2016;Abdurofi et al., 2017;Dwivedi et al., 2020), and farm budgetary analysis (Olorunwa, 2018) using gross margin analysis.
Hence, the objectives of this research were to determine if there were: (i) regional environmental and production differences, (ii) house type production differences, and (iii) profitability differences between the house types in a large scale commercial setting in the summer season.

Experimental sites and house description
Two geographical regions (South eastern, Gaborone, and North eastern, Francistown) were selected for long-term monitoring (2016 to 2017) due to their known different weather conditions and large human population offering lucrative market for broiler meat.They are about 430 km apart.Monitoring in each region was done the entire year and data for the summer period extracted.In each region, three large scale commercial farms were randomly selected for use in the study.In each farm, one chicken house was monitored and was classified by its roof design, namely Gable, Hoop or See-saw.The cross sections and the architectural details are illustrated in Figure 1 and Table 1, respectively.The walls of all the houses were constructed with plastered masonry blocks.The roofs were corrugated iron roof sheets.Bird proofing mesh were installed in all the sidewall openings.Large tarpaulin sheets were used to close the sidewalls during the winter or rainy periods.All the houses had their long axis oriented in the east-west direction and they were not insulated.

Bird management
Day old commercial hybrid Ross-308 chicks were obtained from local hatcheries and delivered at each farm as per the farm's production schedule.Upon arrival, the chicks were group-weighed to obtain their initial body mass before being placed in the houses, which had been previously prepared by cleaning, disinfecting and having rested for two weeks after the previous flock.About a quarter of the floor space, covered with wood shavings, was used during a twoweek brooding period at stocking density of 0.02 m 2 / bird.On the third week, half of the house floor was used at 0.04 m 2 /bird.From the fourth to the fifth week, the entire house floor was used at 0.08 m 2 /bird.The birds were vaccinated against Gumboro and Newcastle disease, and medicated for Coccidiosis at 3 days of age and again at the third week using Sulfadimidine Sodium 33% (Bremer Pharma GMBH, Germany) via the drinking water.Feed and water were provided ad libitum throughout the growth period.In the first 2 weeks, feed was provided via feeder troughs and water via bell drinkers.Thereafter, feed was provided via mechanical feeders and water via nipple drinkers.The feed nutrient composition as analysed at the National Food Technology Research Centre laboratories is shown in Table 2.

Data measurement and collection
The environmental parameters were monitored continuously during each 5-week production cycle using data loggers.These were indoor dry bulb temperature and relative humidity using a data logger (Model SSN-22 temperature/RH, Hairuis Instruments Co., Ltd, Shenzhen, China); and air velocity across the house using an anemometer (Model AZ8905 vane anemometer, AZ Instrument Corp. Taiwan).A wireless weather station (Model HP1000, Fine Offset Electronics Co., Ltd, Taiwan) was installed just outside each house to measure solar radiation, outdoor dry bulb temperature and relative humidity, wind speed and direction, and indoor barometric pressure.Water consumption was measured hourly using a water meter (Model V100-C020, Elster Metering Ltd., UK) connected to a pulse input data logger (Model OM-CP-PULSE101A, Omega, UK) which gave a pulse output for every 0.5 litre of water consumed.These data were measured on an hourly basis and downloaded at the end of each 5-week production cycle.Bird behaviour was observed and recorded during weekly visits.

Effect of Housing Design and Location on Production and Economic Performance of Broiler Chickens during Summer in Botswana
The bird data collected included weekly measurement of bird mass, daily mortality, and daily feed consumption.The derived variables were body weight gain (BWG), average daily gain (ADG), and FCR.The economic efficiency of growth was determined through the calculations of the European Broiler Index (EBI) and European Production Efficiency Factor (EPEF).A high EPEF value indicates a good overall technical efficiency of the broiler operation and is desirable for optimum returns (Samarakoon & Samarasinghe, 2012).
The derived variables were calculated using the following formulae:

Gross margin analysis
The average production and economic variables were computed from the three replications for each of the houses.To assess the profitability and evaluate the economic efficiency of the broiler production under the different housing structures, gross margin analysis was used.Gross margin, measured per unit, gives the difference between the gross income (total output multiplied by unit price of output), and the total variable cost.Gross margins are used to evaluate the economic viability of an enterprise (Karanja, 2010) and for current and future managerial decision-making.The farm activity with the highest gross margin per unit is considered the most viable.
Given that feed costs constitute almost 70% of broiler production costs, the return on feed costs per bird (ROFC) and per kg was computed as the difference between total income from the sold bird (pula per bird or kg) and the total feed cost (BWP/bird or per kg) (Karangiya et al., 2016).From the calculated return on feed costs per bird, the input-output ratio was computed across the different broiler production houses to evaluate efficiency.

Experimental design and data analysis
The experiment was a Completely Randomised Block Design (CRBD) with geographic regions acting as blocks.The data on BW, BWG, ADG, FCR, EBI and EPEF were subjected to analysis of variance (ANOVA) with p<0.05 significance level (SAS, Version 9.4, SAS Institute Inc, Cary, NC, USA, 2002USA, -2012)).If significant differences (p<0.05) were detected, the Least Significant Difference (LSD) was used to separate the means.The data used in the analysis were those collected in the years 2016 and 2017, each with three 35-day production cycles or replications.

Environment conditions
The analysis of variance (ANOVA) revealed significant interactions (p<0.05) between the regions (North east and South east) and House types (Gable, Hoop and See saw) with the mean indoor conditions (temperature and relative humidity).These are shown in Table 3.
In the North-eastern region, the average indoor temperature for the Gable-roofed house (28.3.0±0.3 o C) was significantly higher (p<0.05)than those for the Hoop and Seesaw-roofed houses, respectively (27.1±0.3 o C and 26.6±0.3o C).Oloyo (2018) reported that internal temperature above 26.7 o C combined

Effect of Housing Design and Location on Production and Economic Performance of Broiler Chickens during Summer in Botswana
with high RH adversely affected the feed efficiency and weight gain of the chickens.The Gable and Hoop roofs did not have ridge openings to allow escape of heat by thermal buoyancy, resulting in indoor heat build-up.
The mean wind speed measured about 5 m outside the sidewall openings of the houses averaged 1.09±0.07,0.94±0.07and 1.45±0.07m/s in the Gable-, Hoop-, and See-saw-roofed houses, respectively.In the South-east, the mean indoor temperatures were not significantly different (p>0.05) between the houses.The mean wind speed values were 1.27±0.07,1.22±0.07and 1.50±0.07m/s.Lacy & Czarick (1992) reported better growth rate for broilers reared at a temperature range between 25-30 o C with air velocity of 2 and 3 m/s.The higher air velocity of 3 m/s tends to favour older birds rather than younger birds, since the latter require higher temperatures especially at brooding age (Simmons et al., 2003).The air velocities recorded in both regions were below 2 m/s, which may have contributed to higher average indoor temperatures.

Production performance -Interaction effects
There were significant interaction effects found between the regions and house types for cumulative feed consumption (CFC, p=0.0031), average daily gain (ADG, p=0.0014) and cumulative water consumption (CWC, p=0.0062).The effect of house type contributed more to the interaction significance in the CFC (p=0.0393) and ADG (p=0.002), while effect of the region contributed more to the interaction significance for the ADG (p=0.0013) and CWC (p=0.0041).These are shown in Table 4.In the North-eastern region, CFC, ADG and CWC were significantly higher in the Hoop-roofed house as compared to the Gable-and See-saw-roofed houses (p<0.05), with the values of 1294.4 g/bird/day, 32.2 g/ bird/day and 4.9 L/bird, respectively.The Hoop-roofed house experienced relatively lower temperatures (29.1±0.3 ºC) during the day compared to the other houses, which perhaps encouraged birds to consume more feed and consequently gain more body mass.High ambient temperature is reported to suppress birds' appetite and cause reduced feed intake (Zhao et al., 2014).The same parameters were not significantly different (p>0.05) between the Gable-and See-sawroofed houses.In the South eastern region, both CFC and ADG were not significantly different (p>0.05) between the houses, while WC was significantly higher (p<0.05) in the Gable-roofed house as compared to the other houses.This could be due to the high indoor temperature (31.0±0.3 ºC) experienced in the Gableroofed house, where the birds responded by drinking more water to cool down.
Based on the 35 th day of grow-out, the bird stocking densities in the North-eastern region averaged 18, 23, and 16 kg/m 2 in the Gable-, Hoop-and See-sawroofed houses, respectively.Correspondingly, they were 16, 19, and 17 kg/m 2 in the South east.Aviagen (2016) recommends maximum stocking density of 20 to 25 kg/m 2 at processing during hot weather and 16 to 18 kg/m 2 during the hottest times of the year.Based on these recommendations, the farms were operating within acceptable limits.Stocking density is a decision based on economics, local welfare regulations, processing weight, and expected weather conditions (Aviagen, 2016;Buijs, 2009) and can be different in various countries and husbandry systems.Stocking density has critical implications in that higher returns can be obtained as the number of birds per unit area increases (Kryeziu et al., 2018).However, if densities are exceeded, economic profit may be reduced due to impairment of bird performance, health, and welfare (Adeyemo et al., 2016).

Production performance -Regions main effects
There were significant differences (p<0.05) between regions for the adjusted FCR, EBI and EPEF.These results are shown in Table 5.The birds'performance in the South-eastern region was superior to the North-eastern one as shown by a significantly lower (p<0.05)adjusted FCR and significantly higher (p<0.05)values of both EBI and EPEF, indicating high production efficiency (Mesa et al., 2017).This could be attributed to cooler temperatures experienced in the Southern region (Table 3), resulting in better feed utilization and conversion.

Production performance -House type main effects
There were significant differences (p<0.05)among house types for the body mass of the birds at 35 days of age (BM35d), adjusted FCR, EBI and EPEF.These results are shown in Table 6.
The Hoop-roofed house had the lowest adjusted FCR (1.53±0.06),indicating that the birds were most efficient in converting feed into meat; which is further supported by higher the BM35d of 1703.3±44.6 g/ bird when compared to the other house types.The corresponding EBI and EPEF for the Hoop-roofed house are also significantly higher (p<0.05)when compared to the other house types, which had lower values.The higher EBI and EPEF values correspond to higher average body weight, superior liveability and higher FCR, indicating overall superior economic feeding in birds (Saiyed et al., 2015) reared in the Hoop-roofed house.Furthermore, higher values indicate that the birds' body weight gain was uniform, and the flock was in good health (Bhamare et al., 2016).There were no significant differences (p>0.05)detected between regions and house types for mortality and liveability.This could be attributed to similar management practices between the regions, especially regarding routine vaccinations and medications.Generally, performance of human managers might vary greatly in livestock production, with some producing consistently better results than others (Mesa et al., 2017).Cumulative mortality at 35 days of age was 9.0±1.4% and 7.4±1.3%for the Northeast and South-east regions, respectively, and were not significantly different (p=0.4350).Correspondingly, liveability ratios were 91.0% and 92.6%, and were not significantly different (p=0.4350).For the house types, cumulative mortality rates were 8.0±1.8,8.7±1.6% and 7.9±1.6%for the Gable-, Hoop-and See-sawroofed houses, respectively, with no significant differences (p=0.9472).The corresponding liveability rates were 92.0±1.8%,91.3±1.6% and 92.1±1.6%, also with no significant differences (p=9472).

Economic performance -costs of production
Due to data loss in the Southern region, only data in the Northern region was used to perform an economic analysis (Table 7).It is evident that feed costs constitute the highest variable costs, averaging 48.75% and consisting of almost half of the total variable cost.This is in line with reports by Kondo et al. (2015) and Karangiya et al. (2016), who reported that feed costs constitute about 70% and 80% of total costs of poultry production, respectively, in developing countries.The second highest cost is for day-old chicks and processing costs, each of which constitutes about 17% of the total cost.The profitability was assessed based on the farm gross margin.From the gross revenue and total variable costs, the gross margin, and the gross margin per kilogram of carcass were computed.Table 7 also shows that the Gable-roofed structure had the highest gross margin and was thus the most profitable among the different broiler house structures.The specific housing features combined with better management procedures may have contributed to amelioration of broiler conditions, leading to high production efficiency (Jacobs et al., 2016).

Figure 1 -
Figure 1 -Cross sectional view of the broiler houses used in the study.

Table 1 -
Architectural details of the chicken houses monitored.

Table 2 -
Feed composition used in the experiment at both regions.

Table 3 -
Average indoor temperature ( o C) and relative humidity (%) across the regions.

Table 4 -
Average cumulative feed consumption (CFC, g/bird/day), average daily gain (ADG, g/bird/day) and cumulative water consumption (CWC, L/bird) of the birds across regions.

Table 5 -
Adjusted feed conversion ratio (FCR), European Broiler Index (EBI) and European Production Efficiency Factor (EPEF) of the birds across regions.

Table 6 -
Body mass at 35 days of age (BM35d, g/bird), adjusted feed conversion ratio (FCR), European Broiler Index (EBI) and European Production Efficiency Factor (EPEF) of the birds across house type designs.
Means within a column with different superscript differ significantly (p<0.05);SEM=Standard error of the mean.

Table 7a -
Revenue generation (BWP) for poultry production at the Northern sites.