Impact of Porcine Enzootic Pneumonia and Pleuropneumonia lesions on Carcass Weight and Meatiness: Quantitative Insights from a Mixed-Model Analysis

doi:10.21203/rs.3.rs-4700132/v1

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Research Article

Impact of Porcine Enzootic Pneumonia and Pleuropneumonia lesions on Carcass Weight and Meatiness: Quantitative Insights from a Mixed-Model Analysis

https://doi.org/10.21203/rs.3.rs-4700132/v1

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Background

Porcine respiratory disease complex (PRDC) significantly impacts the global pig industry, causing substantial economic losses. This study aimed to quantify the effects of cranio-ventral pulmonary consolidation (CVPC) and pleurisy on carcass weight and meatiness in finishing pigs. We employed a mixed-model analysis to assess lung lesions at slaughter and their correlation with production parameters across seven pig farms.

Results

The mean prevalence of lesions was 23.8% for CVPC and 15.4% for pleurisy. Pigs with severe lung lesions (> 15.1%) showed significantly lower ADCWG compared to those without lesions (0.951 vs. 0.997 kg/day, p = 0.024). The mixed-effects model revealed that lesions in the right apical lobe and dorso-caudal pleurisy were associated with significant reductions in carcass weight (-2.77 kg and − 2.29 kg, respectively) and carcass meat (-1.76 kg and − 1.43 kg, respectively). An economic analysis under average market price conditions demonstrated that severe lung lesions could lead to losses of up to 11.53 EUR per affected pig.

Conclusions

This study provides quantitative evidence of the negative impact of CVPC and pleurisy on carcass weight and meatiness in finishing pigs. The findings underscore the importance of effective respiratory disease management in swine production, highlighting potential areas for targeted interventions to improve animal health and economic outcomes.

Porcine respiratory disease complex (PRDC) significantly impacts the global pig industry, primarily by affecting growing and finishing pigs. This multifaceted syndrome, characterized by a combination of pathogens and environmental conditions affecting the respiratory system, leads to substantial economic losses through decreased growth rates, increased feed conversion and mortality, and higher costs for medical treatments and management (1–4).

In compliance with legislation (5), all pig carcasses undergo routine meat inspection at abattoirs to ensure food safety and animal welfare. However, the data collected during this process holds value beyond immediate health and safety concerns (6). It provides crucial information for estimating the prevalence of specific conditions, informing herd health advisory services, and developing more effective disease management and prevention strategies (7–11).

Abattoir evaluation of lung lesions plays a pivotal role in assessing the prevalence and severity of respiratory diseases in swine herds (9, 12). These evaluations are instrumental in detecting subclinical states, providing insights into ongoing respiratory issues, and assessing risk factors and vaccine efficacy at the farm level (13, 14). The presence of lung lesions, particularly cranio-ventral pulmonary consolidations (CVPC) and pleurisy, is often associated with reduced animal productivity, such as decreased and uneven weight gain and poorer feed conversion efficiency (7, 8, 15, 16).

While the negative impact of these conditions on finishing pigs is well-documented, most studies quantify losses in terms of live animal production rather than meat quality or carcass traits. There is limited literature that comprehensively reviews the impact of lung lesions on pig production from both productivity and economic perspectives (Fig. 1).

Assessing the economic losses due to lung lesions presents unique challenges, given the various factors involved in calculations, including country-specific market prices of livestock, cost structure of the farm (e.g.feeding costs), and management practices (17, 18). Lung lesions are major causes of lung condemnation and slower slaughter line speeds, as more carcasses require trimming. This additional processing can lead to significant delays and increased labor costs at abattoirs (4). CVPC accounts for approximately 50.0% of lung rejections, underscoring its substantial role in affecting production efficiency (4).

Despite the recurring problem of CVPC and pleurisy in the global pig industry, detailed information about the scale of economic losses due to these conditions remains scarce in the literature. The impact of condemnations at abattoirs, though often overlooked, represents a significant factor in the overall economic burden of respiratory diseases in pigs.

This study aims to quantify the impact of CVPC and pleurisy on the production and economic performance of finishing pigs. Specifically, we seek to: (I) Assess the prevalence of CVPC and pleurisy in slaughter pigs from multiple farms. (II) Determine the relationship between lung lesions and key production parameters, including carcass weight, meatiness, and average daily carcass weight gain. (III) Evaluate the economic consequences of these respiratory conditions under various market price scenarios. By integrating data from abattoir inspections with farm-level production information, this research aims to provide a comprehensive understanding of how these common respiratory issues affect both animal performance and final product quality. The findings from this study will contribute to the development of more effective herd health management strategies and help improve the economic efficiency of pig production.

The production characteristics of the fattening pigs from the seven different swine batches showed notable variability. The number of pigs per batch was mostly consistent at 100, except for batch 4 and 5, which had 99 and 80 pigs, respectively. Average fattening pig weight ranged from 115.73 kg in batch 5 to 122.66 kg in batch 3. The fattening period varied, with the shortest period being 86.60 days in batch 2 and the longest being 99.40 days in batch 7. Average daily gain (ADG) was highest in batch 2 (982.00 g/day) and lowest in batch 1 (925.40 g/day). Carcass weight also differed among the batches; it was highest in batch 7 (94.10 kg) and the lowest (88.90 kg) in batch 5. Meatiness percentages ranged from 58.86% in batch 7 to 60.82% in batch 2, indicating variations in the proportion of meat among the different batches (Table 1).

Table 1

Production characteristics of fattening pigs from seven different farms.
Swine batch	No pigs	Pig weight [kg]	Duration of fattening period [days]	ADG [g/day]	Carcass weight [kg]*	Meatiness [%]
1	100	117.85	97.10	925.40	84.40	59.18
2	100	117.81	86.60	982.00	90.50	60.82
3	100	122.66	97.50	978.80	92.90	60.01
4	99	117.55	88.20	966.00	90.50	60.53
5	80	115.73	93.4	940.90	88.90	59.50
6	100	120.81	94.00	969.90	92.60	60.17
7	100	121.29	99.40	940.30	94.10	58.86
ADG- average daily gain; Swine batch - each batch comes from a different farm.
* the weight and meatiness was measured 45 minutes after slaughter, thus weight reveled to hot carcass

Assessment of macroscopic lung lesions

The prevalence of lesions among different swine batches showed significant variability, as indicated by the Chi-square test results (χ² = 96.387, p < 0.001) (Table 2). Batch 1 had the highest overall prevalence of lesions (55%), with 45% of pigs having no lesions, 17% with 0.1%-5% lesions, 26% with 5.1%-15% lesions, and 12% with more than 15.1% lesions. In contrast, Batch 2 had the lowest overall prevalence (11%), with 89% of pigs having no lesions, 6% with 0.1%-5% lesions, 4% with 5.1%-15% lesions, and only 1% with more than 15.1% lesions. Batch 5 had an intermediate prevalence of lesions, with 67.50% having no lesions, 17.50% with 0.1%-5% lesions, 13.75% with 5.1%-15% lesions, and 1.25% with more than 15.1% lesions.

Table 2

Distribution of number of lungs per batch according to prevalence of CVPC lesions.
		Prevalence of lesions
		0% lesions	0.1–5.0%	5.1–15.0%	≥ 15.0%	≥ 0.1%
Swine batch	No lungs	Count (total %)
1	100	45*	17*	26*	12*	55*
2	100	89	6	4*	1	11
3	100	85	8	5	2	15
4	99	76	11	11	1	23
5	80	54	14*	11	1	26
6	100	88	2*	6	4	12
7	100	80	5	10	5	20
Total	N = 679	517 (76.14)	63 (9.28)	73 (10.75)	26 (3.83)	162 (23.86)
Indicates p-value less than 0.05 for each group of lesions.

Weighing of carcasses, assessment of meatiness, and average daily carcass weight gain (ADCWG)

The analysis of variance for carcass weight, carcass meat, and average daily carcass weight gain (ADCWG) across different categories of lesions revealed significant differences (Table 3), particularly between category 1 and 4. Pigs with no lesions (category 1) had the highest values, with an average carcass weight of 92.70kg (SD = 6.69), carcass meat of 55.57 kg (SD = 4.12), and an ADCWG of 0.997 kg/day (SD = 0.08). In contrast, pigs with more than 15.1% lesions (category 4) had the lowest values, with an average carcass weight of 91.32 kg (SD = 7.36), carcass meat of 54.60 kg (SD = 3.73), and an ADCWG of 0.95 kg/day (SD = 0.07, p = 0.024).

Table 3

Impact of the extent of the macroscopic lung lesions on carcass weight, carcass meat, and average daily carcass weight gain (ADCWG)
Group	Carcass weight kg/animal (SD)	Carcass meat kg/animal (SD)	ADCWG kg/day (SD)
1	92.702 (6.685)	55.568 (4.119)	0.997^A (0.076)
2	92.940 (5.821)	55.449 (3.908)	0.995^AB (0.072)
3	93.271 (6.745)	55.281 (3.929)	0.988^AB (0.072)
4	91.315 (7.365)	54.597 (3.727)	0.951^B (0.068)
ADCWG p = 0.024; Group- based on the extent of the macroscopic lung lesions, the pigs were categorized into four groups: Group 1 – no macroscopic lesions; Group 2–0.1–5% of lesions; Group 3–5.1–15% of lesions; Group 4 – more than 15.1% of lesions; Carcass meat = carcass weight (kg) * meatiness (%) / 100; ADCWG (Average Daily Carcass Weight Gain) = carcass weight (kg) / fattening period (days); Explanation: Different letters (^A, ^B) indicate statistically significant differences at a significance level of less than 0.05.

The analysis of the relationship between ADCWG and the lung lesion percentage revealed a statistically significant negative correlation (r=-0.19, p = 0.015) (Fig. 2).

Specific lung regions were frequently affected by lesions independently of other regions e.g. lesions were most found in the dorso-caudal pleurisy area with 105 cases (15.5% of the total population of 679 pigs). The intermediate and right cardiac lobes were also frequently affected namely 80 cases (11.8%) and 81 cases (11.9%), respectively (Fig. 2).

Significant co-occurrences between different lung regions were identified, highlighting strong associations between lesion occurrences in certain areas. The right diaphragmatic lobe and the intermediate lobe had the highest co-occurrence with 42 cases (6.2%), followed closely by the right diaphragmatic lobe and the right cardiac lobe with 39 cases (5.7%). The right cardiac lobe and the intermediate lobe had 37 cases (5.4%) of concurrent lesions, suggesting these regions are commonly affected together. Other notable co-occurrences include 33 cases (4.9%) between the intermediate lobe and the left cardiac lobe, and 33 cases (4.9%) between the right cardiac lobe and the right apical lobe. The right diaphragmatic lobe and the right apical lobe had 32 cases (4.7%) of concurrent lesions, while the right cardiac lobe and the left cardiac lobe co-occurred in 30 cases (4.4%). Finally, there were 27 instances (4.0%) of co-occurrence between the left cardiac lobe and the right apical lobe, and 26 cases (3.8%) each between the intermediate lobe and the right apical lobe, and the right diaphragmatic lobe and the left cardiac lobe (Fig. 2).

Economic analysis

The economic loss analysis revealed significant financial impacts associated with lung lesions. The analysis considered three price scenarios: minimum (201.86 EUR/100kg), average (221.77 EUR/100kg), and maximum (235.59 EUR/100kg) observed prices.

The results showed that pigs with 0.1-5% lesions incurred losses of 2.62, 2.88, and 3.06 EUR/pig under the minimum, average, and maximum price scenarios, respectively, compared to pigs with no lesions. Pigs with 5.1–15% lesions showed slightly higher losses of 2.83, 3.10, and 3.30 EUR/pig. The most substantial economic impact was observed in pigs with more than 15.1% lesions, with losses of 10.50, 11.53, and 12.25 EUR/pig under the three price scenarios. The maximum loss relative to the group with no lesions was 11.53 EUR/pig under the average price scenario, highlighting the significant economic consequences of severe lung lesions (Fig. 4).

For carcass weight and carcass meat, significant negative associations were found with lesions in the right apical lobe and dorso-caudal pleurisy (Table 4 and Table 5). Specifically, lesions in the right apical lobe were associated with a decrease in carcass weight by 2.77 kg (p = 0.01), while dorso-caudal pleurisy was associated with a decrease of 2.29 kg (p < 0.001). These reductions in carcass weight translate to significant economic losses across different price scenarios. At the minimum price of 201.86 EUR/100kg, lesions in the right apical lobe resulted in losses of 5.59 EUR/pig, while dorso-caudal pleurisy caused losses of 4.62 EUR/pig. Under the average price scenario of 221.77 EUR/100kg, these losses increased to 6.14 EUR/pig for right apical lobe lesions and 5.08 EUR/pig for dorso-caudal pleurisy. In the maximum price scenario of 235.59 EUR/100kg, the losses further rose to 6.53 EUR/pig and 5.39 EUR/pig for right apical lobe lesions and dorso-caudal pleurisy, respectively.

Table 4

Coefficients of the mixed effects model for carcass weight and lung lesions. Table presents the coefficients, standard errors, p-values, and confidence intervals for the fixed effects in the mixed effects model examining the relationship between various lung lesions and carcass weight. The model also includes a random effect for the group variable supplier. The asterisks (*) denote statistically significant coefficients p-value < 0.05.
Parameter	Coefficient	SEM	p-value	95% CI
Left apical lobe	-1.46	1.70	0.39	[-4.79, 1.87]
Left cardiac lobe	1.43	0.88	0.10	[-0.29, 3.16]
Left diaphragmatic lobe	-0.16	1.31	0.90	[-2.74, 2.41]
Intermediate lobe	-0.45	0.84	0.60	[-2.09, 1.20]
Right diaphragmatic lobe	1.26	1.03	0.22	[-0.75, 3.28]
Right cardiac lobe	-0.19	0.86	0.82	[-1.88, 1.49]
Right apical lobe *	-2.77	1.12	0.01	[-4.96, -0.58]
Cranial pleurisy	-0.35	0.70	0.62	[-1.73, 1.03]
Dorso-caudal pleurisy *	-2.29	0.63	< 0.001	[-3.53, -1.06]
Scar	-1.38	1.99	0.49	[-5.29, 2.53]
Carcass weight (kg)

Table 5

Coefficients of the mixed effects model for carcass meat and lung lesions. Table presents the coefficients, standard errors, p-values, and confidence intervals for the fixed effects in the mixed effects model examining the relationship between various lung lesions and carcass meat. The model also includes a random effect for the group variable supplier. The asterisks (*) denote statistically significant coefficients p-value < 0.05.
Parameter	Coefficient	SEM	p-value	95% CI
Left apical lobe	-0.37	1.10	0.74	[-2.53, 1.79]
Left cardiac lobe	0.76	0.57	0.19	[-0.36, 1.88]
Left diaphragmatic lobe	-0.09	0.85	0.92	[-1.76, 1.58]
Intermediate lobe	-0.41	0.55	0.46	[-1.48, 0.66]
Right diaphragmatic lobe	0.80	0.67	0.23	[-0.52, 2.11]
Right cardiac lobe	-0.05	0.56	0.93	[-1.14, 1.04]
Right apical lobe *	-1.76	0.72	0.02	[-3.18, -0.34]
Cranial pleurisy	-0.22	0.46	0.63	[-1.12, 0.68]
Dorso-caudal pleurisy *	-1.43	0.41	< 0.001	[-2.23, -0.63]
Scar	-1.43	1.29	0.27	[-3.97, 1.11]
Carcass meat = carcass weight (kg) * meatiness (%) / 100

In terms of ADCWG, lesions in the right apical lobe and dorso-caudal pleurisy also showed significant negative effects (Table 6) namely a reduction in ADCWG by 30 g/day (p = 0.01), and a decrease of 30 g/day (p < 0.001), respectively.

Table 6

Coefficients of the mixed effects model for ADCWG (average day carcass weight gain) and Lung Lesions. Table presents the coefficients, standard errors, p-values, and confidence intervals for the fixed effects in the mixed effects model examining the relationship between various lung lesions and ADCWG. The model also includes a random effect for the group variable supplier. The asterisks (*) denote statistically significant coefficients p-value < 0.05.
Parameter	Coefficient	SEM	p-value	95% CI
Left apical lobe	-0.01	0.02	0.43	[-0.05, 0.02]
Left cardiac lobe	0.01	0.01	0.13	[-0.00, 0.03]
Left diaphragmatic lobe	-0.00	0.01	0.91	[-0.03, 0.03]
Intermediate lobe	-0.01	0.01	0.54	[-0.02, 0.01]
Right diaphragmatic lobe	0.01	0.01	0.26	[-0.01, 0.03]
Right cardiac lobe	-0.00	0.01	0.80	[-0.02, 0.02]
Right apical lobe *	-0.03	0.01	0.01	[-0.05, -0.01]
Cranial pleurisy	-0.00	0.01	0.65	[-0.02, 0.01]
Dorso-caudal pleurisy *	-0.03	0.01	< 0.001	[-0.04, -0.01]
Scar	-0.01	0.02	0.49	[-0.06, 0.03]
ADCWG (average day carcass weight gain) = carcass weight (kg) / fattening period (days)

This study focused on assessing impact of CVPC and pleurisy changes in lungs on production and economic parameters of fattening pigs. Our findings reveal significant implications for the swine industry, highlighting the importance of respiratory health in maintaining optimal production and economic outcomes.

The mean prevalence of lesions observed in our study was 23.86% for CVPC and 15.46% for pleurisy. These figures are lower than those reported in previous studies conducted in Poland, where a 45.10% prevalence of macroscopic lung lesions for CVPC at the slaughterhouse was observed (19). However, our study's prevalence falls within the range reported for different European countries, which varies from 19–74%, depending on the source (13, 20–25).

The discrepancy between our findings and previous Polish studies could be attributed to several factors. Firstly, our study had a limited number of investigated animals, which may have led to an underestimation of the true prevalence. Secondly, improvements in herd management practices, vaccination programs, and biosecurity measures implemented in recent years could have contributed to a reduction in the prevalence of lung lesions. Despite these potential explanations, our results confirm that CVPC and pleurisy remain important lesions, affecting swine productivity, as noted by Petri et al. (2023) (26).

The variability in lesion prevalence among different batches in our study (ranging from 11–55%) underscores the complex nature of respiratory diseases in swine. This variability could be attributed to differences in farm management practices, environmental conditions, and the specific pathogens present in each herd (23). Such findings emphasize the need for farm-specific approaches to respiratory disease control and prevention.

Our study provides strong evidence for the association between lung lesions and decreases in productivity, as expressed by various production characteristics. This relationship has been consistently reported in previous studies (16, 27–29). The impact of lesions on the performance was particularly evident in Batches 2 and 5. Batch 2, which had the lowest overall prevalence of lesions (11%), demonstrated the highest average daily gain (ADG) and meatiness, as well as the shortest fattening period among the investigated population. This observation aligns with the general understanding that healthier lungs contribute to better feed conversion and growth rates. Conversely, Batch 5, which had a higher prevalence of lesions, presented the lowest liveweight and carcass weight, reaching only 115.73 kg and 88.9 kg, respectively. Other productive parameters such as ADG and fattening period in Batch 5 were at average levels, suggesting that the impact of lung lesions may be more pronounced on final weight rather than on daily gain in some cases.

Our findings are consistent with previous research reporting that the ADG of animals with CVPC was reduced by 7–9% during the fattening period (30). Our results also support the more detailed findings of Hill et al. (1992) (31), who reported that ADG decreased by 41.1 g for every 10% of the pig's lung surface affected by CVPC. Regarding pleurisy, our observations align with those of Pagot et al. (2017) (32), who found that pleurisy at slaughter was associated with an ADG decrease of 39g.

Our study focused on the calculation of daily ADCWG, carcass weight, and meat weight as related characteristics describing pig performance impacted by lesions. The results clearly showed that pigs with a higher category of lesion had decreased daily carcass weight gain compared to pigs with no lesions. The significant difference in ADCWG (p = 0.024) between lesion categories indicates that the severity of lung lesions negatively impacts overall production efficiency.

This relationship is further supported by the statistically negative correlation (r=-0.191, p = 0.015) between ADCWG and the severity of lesions. While this correlation is considered weak, it nonetheless demonstrates a clear trend: as the severity of lung lesions increases, the daily carcass weight gain tends to decrease. This finding has important implications for the swine industry, as it quantifies the direct impact of respiratory health on a key production metric.

Our productive analysis revealed that CVPC and dorso-caudal pleurisy could cause substantial weight losses in carcass weight, specifically 2.77 kg and 2.29 kg in animals with lesions, respectively. These results are in line with other studies investigating declines in carcass weight associated with lung lesions' severity (19, 27, 33–35). The consistency of these findings across multiple studies and geographical regions underscores the global significance of respiratory health in swine production.

It's worth noting that our results diverge from those reported by Escobar et al. (2004) (36), who found no consistent impact on carcass weight associated with CVPC severity. This discrepancy could be attributed to differences in study design, particularly the use of experimental infection conditions by Escobar et al. (2004), which may not accurately reflect field conditions. Our study, conducted under real-world production conditions, may provide a more realistic assessment of the impact of lung lesions on carcass characteristics.

The economic analysis demonstrates the significant financial impact of lung lesions on pork production. By considering three price scenarios, we quantified the economic losses associated with different severities of lung lesions. The most substantial impact was observed in pigs with severe lesions (more than 15.1%), with losses reaching up to 12.25 EUR per pig in the maximum price scenario. Even mild lesions result in noticeable economic losses, while severe lesions can lead to losses exceeding 10 EUR per pig. When extrapolated to the scale of large commercial pig operations, these losses can amount to substantial sums, potentially affecting the profitability and sustainability of pig farming enterprises. These findings highlight the considerable economic burden that respiratory diseases place on the swine industry, emphasizing the potential for substantial cumulative losses in large-scale operations.

Moreover, our study provided detailed calculations of meat weight impacted by lung lesions. Since revenue depends on carcass weight and meatiness, and the percentage of meat tissue in the carcass defines its quality class, the reduction of meat weight caused by lung lesions is of economic significance. We found substantial losses in carcass meat weight correlated with CVPC and dorso-caudal pleurisy, with declines of 1.76 kg and 1.43 kg, respectively.

Our study's findings may have significant implications for herd health management in the swine industry, emphasizing the critical importance of respiratory disease prevention and control for optimal production efficiency and economic outcomes. The results highlight the need for comprehensive respiratory health programs, early detection and intervention strategies, and regular monitoring of respiratory health. The variability in lesion prevalence and severity among different batches suggests that farm-specific factors play a crucial role, necessitating tailored approaches to disease prevention and control. Our economic analysis provides a strong rationale for investing in respiratory health, with potential savings from preventing severe lung lesions justifying significant expenditures on preventive measures. Finally, the detailed analysis of lesion location and co-occurrence could inform more targeted intervention strategies, particularly focusing on high-prevalence areas such as the dorso-caudal pleurisy region.

While our study provides valuable insights into the impact of lung lesions on swine production, it's important to acknowledge its limitations. The sampling of herds was not done randomly, which may have introduced bias into our estimated prevalence of lesions. Our original intention to include only lungs from carcasses deemed fit for human consumption may have led to an underestimation of the true prevalence and severity of lung lesions in the overall swine population. The limited number of farms in our study may restrict the generalizability of our findings.

Future research could address these limitations by incorporating larger, randomly selected samples from a wider range of farms. Longitudinal studies tracking pigs from birth to slaughter could provide more detailed insights into the development of lung lesions and their impact on growth and production parameters over time. Additionally, studies investigating the effectiveness of various intervention strategies in reducing the prevalence and severity of lung lesions could provide valuable practical guidance for swine producers.

Moreover, future research could explore the potential synergistic effects of different types of lung lesions and their combined impact on production parameters. The co-occurrence of lesions in certain lung regions observed in our study suggests that such interactions may be significant and warrant further investigation.

This study highlights the substantial negative impact of CVPC and dorso-caudal pleurisy on swine carcass weight and meatiness, underscoring the need for enhanced respiratory disease management in pig farming. The findings emphasize the value of utilizing abattoir data to develop precise health strategies and tailored interventions specific to each farm. By addressing these respiratory health challenges, the swine industry can improve productivity, economic efficiency, and overall animal welfare, fostering more sustainable and profitable farming practices.

Animal management, housing conditions, and experimental framework

The study was conducted as part of a project by Ceva Animal Health Poland (Warsaw, Poland), which provided a diagnostic package to pig producers experiencing persistent respiratory disease problems in their herds. The data were collected from inspections in one abattoir fattening pigs originating from seven pig farms owned by a single producer. All pigs were of the Great White Polish breed. From each farm, one batch of approximately 100 pigs (the sex of the animals was not considered) was evaluated. The lung inspections were performed by two trained investigators. Production data of the fattening pigs from each batch were supplied by the pig producer.

Assessment of macroscopic lung lesions

Lung evaluations focused on the left apical lobe, left cardiac lobe, left diaphragmatic lobe, intermediate lobe, right diaphragmatic lobe, right cardiac lobe, right apical lobe, and regions affected by cranial pleurisy, dorso-caudal pleurisy, and scar presence.

CVPC were scored using a method adapted from Madec and Kobisch (1982) (37). Each lobe was scored on a scale from 0 to 4, based on the percentage of the lobe affected by lesions, with scores as follows: 0 for no lesions, 1 for less than 25% affected, 2 for 26–50% affected, 3 for 51–75% affected, and 4 for more than 76% affected. To account for the different volumes each lobe contributes to the total lung, the scores were adjusted according to the method described by Christensen et al. (1999) (38). The percentage of the affected area for each lobe was multiplied by its relative weight contribution to the total lung volume: right apical lobe (11%), right cardiac lobe (10%), right diaphragmatic lobe (34%), left apical lobe (5%), left cardiac lobe (6%), left diaphragmatic lobe (29%), and intermediate lobe (5%) (Fig. 3). Based on the extent of the macroscopic lung lesions, the pigs were categorized into four groups: Group 1 – pigs without macroscopic lesions; Group 2–0.1–5% of lesions; Group 3–5.1–15% of lesions; Group 4 – more than 15.1% of lesions.

Pleurisy in the dorso-caudal lobes was scored using a modified version of the Slaughterhouse Pleurisy Evaluation System (SPES) developed by Dottori et al. (2007) (39). Cranial pleurisy, characterized by adhesions between lobes or between the lung and heart, and the presence of scars indicating previous pneumonic lesions were recorded as either present or absent for further analysis. Data collection was facilitated by the digital Ceva Lung Program (Ceva Animal Health, France), ensuring consistency and accuracy in the evaluation process.

Weighing of carcasses, assessment of meatiness, and average daily carcass weight gain (ADCWG)

The animals were weighed at the beginning of the finishing phase to establish their initial weights, the mortality rate for each group was involved in calculation of initial weight. After slaughter, the carcasses were weighed to determine their final weights. Additionally, the meatiness of the carcasses was assessed and expressed as a percentage, representing the proportion of the carcass composed of meat, as opposed to fat and bone.

The meat content of the carcass was calculated using the following equation:

$$\:Carcass\:\text{m}eat\left(kg\right)=\frac{Carcass\:\text{w}eight\left(kg\right)\times\:Meatiness\left(\text{\%}\right)}{100}$$

Abattoir production data, including carcass weight and meatiness, were provided by the meat producer. The carcass was weighed immediately after splitting and final washing to obtain the carcass weight. Meatiness was measured with a portable Sydel CGM Fat/ Lean Sensor device (Syleps, France) on the musculus longissimus dorsi, pars lumbalis, on the left half of the carcass, at the level of the 10th and 11th ribs in accordance with applicable legislation (Regulation (EU) 2017/1182) (40). To evaluate the growth performance of the animals, the Average Daily Carcass Weight Gain (ADCWG) was calculated. The ADCWG provides a measure of the average daily increase in carcass weight over the fattening period. It was calculated using the following equation:

$$\:ADCWG\left(kg/day\right)=\frac{Carcass\:weight\left(kg\right)}{Fattening\:period\left(days\right)}$$

This equation divides the final carcass weight by the total number of days in the fattening period, yielding an average daily carcass weight gain. ADCWG could serve as a crucial parameter when adapted for assessing the efficiency of the fattening process and the overall growth performance of the animals.

Data Analysis and Statistical Methods

The statistical analysis was structured to ensure the reliability and validity of the results. Data were collected and stored in text files and MS Excel spreadsheets for efficient organization and accessibility. The analysis was carried out using Python 3.12.3 and R 4.3.3 within the JupyterLab environment, providing the necessary tools for managing statistical models and data visualization.

The normality of the data distribution was confirmed using the Shapiro-Wilk test, with a significance level set at 0.05. Additionally, we examined the homogeneity of variances using Levene's test to validate the assumptions required for parametric analysis. These steps were crucial for the application of parametric statistical methods and for ensuring the accuracy of inferential statistics.

Data from abattoir inspections of seven pig batches, comprising a total of 679 pigs, were analyzed using regression and mixed-model analyses, incorporating the batch a fixed variable. Statistical analyses were conducted with individual pigs as the experimental units

The differences in lesion prevalence among the swine farms were statistically analyzed using the Chi-square test. Following the Chi-square test, a post hoc test with z-score corrections was conducted to identify specific farms that showed significant differences. The Bonferroni correction was applied to adjust for multiple comparisons and control the family-wise error rate.

A regression model was developed using Python 3.12.3 to estimate the linear relationship between the weighted macroscopic lung lesion scores, as measured at the slaughterhouse, and the ADCWG of pigs during the finishing phase. The lesion scores were calculated by multiplying the percentage of the affected area for each lobe by its relative weight contribution to the total lung volume. This model included pigs with lesions categorized into Groups 2 to 4. Additionally, an analysis of variance was employed to estimate and compare the carcass weight, carcass meat, and ADCWG associated with each category of lesions. All multiple pairwise comparisons were performed using Bonferroni corrections to control for Type I errors. The mean and standard deviation (SD) of lesion score groups were calculated and presented in a table.

Additionally, a mixed-effects model was employed to estimate and compare the effects of different types of lesions on carcass weight, carcass meat, and ADCWG. The lesions considered in the model included those in the left apical lobe, left cardiac lobe, left diaphragmatic lobe, intermediate lobe, right diaphragmatic lobe, right cardiac lobe, right apical lobe, cranial pleurisy, dorso-caudal pleurisy, and the presence of scars.

The mixed-effects model was structured to account for the random effects of the farm and other potential confounders while focusing on the fixed effects of the specific lung lesions on the measured outcomes. The following equation was used to model the effects:

$$\:{y}_{i}={\beta\:}_{0}+{\beta\:}_{1}{X}_{i1}+{\beta\:}_{2}{X}_{i2}+\cdots\:+{\beta\:}_{10}{X}_{i10}+{u}_{j\left[i\right]}+{ϵ}_{i}$$

where:

yi represents the [carcass weight, carcass meat, ADCWG] for the i-th unit (animal),
X _i1,…, X _i10 are the independent variable values for the i-th unit corresponding to the areas: left apical lobe, left cardiac lob, left diaphragmatic lobe, intermediate lobe, right diaphragmatic lobe, right cardiac lobe, right apical lobe, cranial pleurisy, dorso-caudal pleurisy, scar,
β ₀ is the model's intercept,
β _1,…, β₁₀ are the fixed effect parameters corresponding to the coefficients for each of the areas,
u _j[i] is the random effect for the j-th supplier (here j is the index for Swine farm assigned to the i-th unit),
ϵ _i is the random error for the i-th unit.

Economic analysis

To assess the economic impact of lung lesions in finishing pigs, we conducted a financial loss analysis using data from the Polish pig market and our findings on ADCWG. Weekly prices for class S pig carcasses (EUR/100kg) were obtained from the European Commission's Meat Market Observatory, specifically from the "Pigmeat statistics" section (41), for the period from December 25, 2023, to June 10, 2024. Pigs were categorized into four groups based on the extent of lung lesions: 0%, 0.1-5%, 5.1–15%, and > 15.1%, with corresponding ADCWG values of 0.912, 0.899, 0.898, and 0.860 kg/day, respectively. We considered three price scenarios: minimum, average, and maximum observed prices during the study period. The revenue for each group and price scenario was calculated using the equation:

$$\:Revenue=\frac{ADCWG\times\:Days\times\:Price}{100}$$

where:

Revenue is the income for a pig in EUR,
ADCWG is the Average Daily Carcass Weight Gain in kg/day,
Days is the number of days in the finishing period (100 days),
Price is the carcass price in EUR/100kg for the given scenario.

Financial losses were then computed relative to the 0% lesions group, serving as the baseline, using the formula:

$$\:Loss=Revenu{e}_{0\text{\%}\text{\:lesions}}-Revenu{e}_{\text{group}}$$

where:

Loss is the financial loss for a pig in EUR,
Revenue_0%lesions is the revenue for a pig with 0% lung lesions,
Revenue_group is the revenue for a pig in the given lesion group.

This calculation was performed for each price scenario to provide a comprehensive view of potential losses under various market conditions. Descriptive statistics were used to summarize the financial losses across groups and price scenarios, with the maximum loss relative to the 0% lesions group identified to quantify the worst-case economic impact. A bar plot was generated to visually represent the financial losses for each group across the three price scenarios, facilitating result interpretation.

ADCWG average daily carcass weight gain

ADG average daily gain

CVPC cranio-ventral pulmonary consolidation

PRDC Porcine respiratory disease complex

SPES slaughterhouse pleurisy evaluation system

Ethics approval and consent to participate

Not applicable.

Consent for publication

All authors have read and agreed to the published version of the manuscript.

Availability of data and materials

None of the data was deposited in an official repository. All the data obtained in the present research are presented in this manuscript. The data that support the study findings are available from the authors upon request.

Competing interests

Although two of the authors PC and RLW are employed by Good Valley and Ceva Animal Health Poland, respectively, their employment did not cause any bias concerning the study. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Funding

Publication of this article was funded by the Minister of Science under the Regional Initiative of Excellence Program.

Authors' contributions

PP contributed to the conceptualization and experimental design of the study; PC and RLW conducted the study; PP and DT analyzed the data; DT designed and provided statistical analysis; PP was a major contributor in writing the manuscript with the support of DT; PC and RLW contributed to manuscript revisions before submission. DM revised the manuscript critically. All authors have read and agreed to the published version of the manuscript.

Acknowledgements

The authors are grateful for the kindness and collaboration of the producer and thank the technical managers for their cooperation in providing the data used in this study.

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No competing interests reported.

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Impact of Porcine Enzootic Pneumonia and Pleuropneumonia lesions on Carcass Weight and Meatiness: Quantitative Insights from a Mixed-Model Analysis

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Abstract

Background

Results

Conclusions

Figures

Background

Results

Assessment of macroscopic lung lesions

Weighing of carcasses, assessment of meatiness, and average daily carcass weight gain (ADCWG)

Economic analysis

Discussion

Conclusion

Methods

Animal management, housing conditions, and experimental framework

Assessment of macroscopic lung lesions

Weighing of carcasses, assessment of meatiness, and average daily carcass weight gain (ADCWG)

Data Analysis and Statistical Methods

Economic analysis

Abbreviations

Declarations

References

Additional Declarations

Status:

Version 1