Review: the effects of dust on feedlot health and production of beef cattle

ABSTRACT

Dust in feedlots is detrimental to optimal cattle performance. Contributors such as climate, manure production, and animal behaviour can affect dust production and ultimately, cattle health. Bovine respiratory disease (BRD) and acute interstitial pneumonia (AIP) represented to 68% of death loss across 30 feedyards from 2015 to 2017. Bovine respiratory disease specifically costs producers between $800 and $900 million each year with the cost per animal varying based on number of treatments, occurrence, and performance differences. Altering feeding schedule, stocking density, and sprinkler systems have decreased dust concentrations. By using these methods, cattle feeders can limit dust production and promote animal health. This paper serves to consolidate previous research and data discussing the effects of dust on cattle health.

KEYWORDS:

• Cattle
• dust
• feedlot
• management

Introduction

Feedlot dust affects cattle health and performance. Feedyards, or an operation where a large number of cattle are fed to market weight in a concentrated area, produce organic dust and particulate matter (PM) at a relatively high concentration on a diurnal basis when manure is dry (Auverman et al., 2001). These materials increase the risk of Bovine Respiratory Disease (BRD) and Acute Interstitial Pneumonia (AIP) (Loneragan et al., 2001). Management protocols to reduce dust incidence include maintaining a greater stocking rate, permanent and portable sprinkler systems, and altering feeding schedule. The purpose of this paper is to explore previous literature concerning BRD and AIP as well as provide consolidated insights on how producers can combat these diseases with management practices.

When determining the origin of dust in feedlots, manure, climate, and animal activity are all considerations. Manure is a large source of airborne dust particles (Amosson et al., 2006). Each animal can produce approximately 900 kg of dry manure from the time they enter a feedlot, during the feeding period, and upon leaving for slaughter, (Sweeten et al., 1988; Sweeten et al., 1998). High temperature combined with low humidity and wind dries manure more rapidly. Dried manure then becomes dust particles and are emitted into the immediate atmosphere by cattle activity or wind (Amosson et al., 2006). In the United States, cattle activity in the Midwest typically increases during the dusk-evening hours when temperatures cool down (Mitloehner et al., 1999). This activity paired with dry, warm conditions contribute to dust production (Wilson et al., 2002). Purdy et al. (2007) reported a sharp rise in dust concentration in four feedlots at 1800h, a maximum concentration at 2100 h, and a sharp decline at 2200 h. Dust is stirred and sent into the atmosphere during this time, but its severity may be curtailed due to decreased wind speed during evening hours. In the spring, however, wind speeds increase and amplify dust production. Wind dries manure and soil faster, blowing particles into the atmosphere (Amosson et al., 2006). These wind events that are associated with dust instances are intensified by drought (Goudie, 2009). Respiratory issues are still prevalent in feedlots from around the United States today. Koers-Turgeon Consulting Service has collected data from feedlot clients during their operations; this data includes many performance parameters and causes of death records across the feedlots they service. These observations collected on 910,965 animals in 30 feedyards from 2015 to 2017 coincided with the seasonality of dust production. Total and respiratory death losses were highest from June to August (Table 1).

Table 1. Percentage^a of death loss in cattle (n = 910,965) recorded from 30 feedlots during 2015–2017 and their attributable causes.

Month	Respiratory^b, %	Digestive^c, %	Other^d, %	Total, %
January	0.26	0.06	0.08	0.42
February	0.21	0.05	0.08	0.34
March	0.19	0.05	0.07	0.32
April	0.18	0.06	0.08	0.32
May	0.22	0.07	0.1	0.39
June	0.4	0.06	0.11	0.57
July	0.44	0.06	0.11	0.6
August	0.42	0.05	0.11	0.58
September	0.38	0.05	0.09	0.53
October	0.37	0.06	0.08	0.52
November	0.38	0.06	0.08	0.53
December	0.38	0.07	0.1	0.55
Average	0.32	0.06	0.09	0.47

^a Koers-Turgeon Consulting Service, Inc. Amarillo, TX 79118, USA.

^b Respiratory deaths are a combined sum of respiratory diseases including pneumonia, chronic pneumonia, bovine respiratory disease, bovine virus diarrhea, bovine respiratory syncitial virus, acute interstitial pneumonia and diphtheria.

^c Digestive deaths are a combined sum of digestive disorders including bloat, acidosis, enterotoxemia and rumenitis.

^d Other deaths include coccidiosis, salmonella, urinary calculi, polioencephalomalacia, hardware disease, peritonitis, pericarditis, septicemia, dystocia, buller, heart failure, liver failure, kidney failure, mechanical related deaths and euthanasia.

Dust effects on cattle health

Respiratory tract diseases are one effect of excess dust in feedlots (Loneragan et al., 2001). Loneragan et al. (2001) also identified BRD as the largest cause of death in feedlots and responsible for approximately 75% of feedlot morbidity. Between 2015 and 2017, records from 30 feedlots across the United States attributed 68% of total death loss to respiratory causes (O. A. Turgeon, personal communication, February 20, 2018). BRD consists of a complex of diseases characterized by many types of infection. Each have their own causes, clinical signs, and economic impact. Viruses predispose cattle to bacterial infection via one of two mechanisms. Viral agents can either cause direct damage to respiratory clearance mechanisms and lung parenchyma, which facilitates translocation of bacteria to the upper respiratory tract, or by interfering with the immune system’s ability to respond to bacterial infection (Czuprynski et al., 2004; Taylor et al., 2010). The most common scenario in BRD development involves stressed or immunocompromised calves that are exposed to an immunosuppressive viral agent, such as bovine diarrhea virus or infectious bovine rhinotracheitis virus (Edwards, 2010). This primary infection of the upper respiratory tract results in a compromised innate immune system and allows commensal bacterial pathogens to migrate and colonize the lower respiratory tract (Edwards, 2010).

In the feedlot environment, dust irritates the animals’ respiratory tract and subsequently carries airborne bacteria and fungi to the lungs (Wilson et al., 2002). While most deaths attributed to BRD occur within the first 45 days in the feedlot, with newly received cattle having the greatest risk, the effects on profits are far-reaching (Loneragan et al., 2001; Sanderson et al., 2008; Taylor et al., 2010). The source of cattle can also have an impact on morbidity in the feedyard (Taylor et al., 2010). Calves procured through sale barns are often more at risk than those arriving directly from ranch sources due to increased exposure to pathogens and increase shipping stress (Step et al., 2008). The sale barn process also lends itself to the spread of BRD associated pathogens. By commingling calves from different locations and exposure levels to different pathogens, the likelihood of BRD increases (Taylor et al., 2010). Ribble et al. (1998) attempted to determine this association. In a study in which all calves were purchased through sale barns, calves that came from smaller sources, which meant introduction to more calves in order to fill pens, had a higher incidence of BRD (Ribble et al., 1998). While mixing, group size, and timing of the movement of animals to the feedlot are all factors that affect instances of BRD (Hay et al., 2014), the goal of this paper is to discuss BRD and its relationship to dust in the United States. Genetics is also thought to have a role in BRD (Taylor et al., 2010). While heritability of BRD susceptibility seems to be low, with a heritability estimate (h²) ranging from 0.04 ± 0.01 to 0.08 ± 0.01, some breed differences have been detected (Snowder et al., 2005). While there are claims that certain breeds have a higher or lower incidence rate of BRD, these claims and results are conflicting among each other (Durham et al., 1991; Muggli-Crockett, 1992; Snowder et al., 2005; Cusack et al., 2007; Hägglund et al., 2007).

It is estimated that BRD causes between $800 million to $900 million in economic losses each year (Brooks et al., 2011). Medicinal costs associated with BRD treatment can be substantial. Of the profit losses measured in their study, Brooks et al. (2011) reported medicinal costs accounted for 21% of profit loss of the carcass while 79% of profit loss was attributed to lower carcass weight and lower quality grade. A Ranch-to-Rail study found cattle with BRD had a 3% less gain with a cost of $111.38 per sick animal (Griffin, 1997). Snowder et al. (2006) estimated that BRD economic losses, in a 1,000 head feedlot, were approximately $13.90 per animal. To combat these losses, vaccination and proper health protocols are key. Nyamusika et al. (1994) reported vaccination programs targeting the treatment of BRD increased net revenues by $44 per animal.

A study conducted by Brooks et al. (2011) explored BRD effects on various performance traits (Table 2). Three hundred and thirty-seven heifers were observed throughout the backgrounding and finishing phases and monitored daily for any signs of BRD. Heifers were placed into five separate groups to classify their incidence of BRD: receiving no medical treatment, receiving one treatment, treated twice, treated three times, and chronic cases. After the backgrounding phase, heifers were allocated to finishing pens based on the number of BRD treatments they received with six heifers per pen. Chronic heifers showed a significant difference in gain during the backgrounding phase by gaining 0.979 kg/day, 0.83 kg/day, and 0.557 kg/day less than heifers never treated, treated once, or twice, respectively. As the number of treatments increased, backgrounding net returns decreased significantly. Heifers with zero treatments had an average of $111.12 greater net returns compared to heifers considered chronic. Whereas, heifers treated once, twice, or three times had $92.51, $59.98, and $20.62, respectively, greater backgrounding net returns than chronics. With the finishing phase included, heifers classified as chronics had significantly lower net returns compared to those with zero, one, or two treatments. Chronic heifers lost significantly more, $143.28, than those with zero treatments and $153.40 and $132.20 more than those treated once or twice, respectively (Brooks et al., 2011).

Table 2. Least squares means for production characteristics by number of bovine respiratory disease treatments (Brooks et al., 2011).

Description	Number of treatments
	0	1	2	3	Chronics
Beginning Weight (kg)	242.84	240.47	239.65	241.33	235.65
ADG – Backgrounding (kg/day)	1.41^a	1.26^b	0.98^c	0.65^d	0.43^d
Backgrounding Feed:Gain Conversion	3.55^a	3.62^a	6.29^b	4.10^a	4.82^a,b
BRD Treatment Drugs ($/head)	0.00^a	9.63^b	23.62^c	35.71^d	35.34^d
Background Cost of Gain ($/kg of gain)	0.21^a	0.24^a,c	.60^b	0.43^b,c	0.53^a,b,c
Net Returns – Backgrounding ($/head)	8.63^a	−9.98^b	−42.51^c	−81.87^d	−102.49^e
ADG – Finishing (kg)	1.41	1.45	1.48	1.50	1.42
Finishing Feed:Gain Conversion	4.30^a	4.18^a,b	3.97^a,b	3.96^a,b	3.76^b
Finishing Cost of Gain ($/kg of gain)	0.46^a	0.45^a,b	0.43^a,b	0.42^a,b	0.40^b
Net Returns – Finishing ($/head)	−110.53	−73.73	−73.49	−92.71	−139.19
Overall Cost of Gain ($/kg of gain)	0.39^a	0.39^a	0.40^a,b	0.42^b	0.42^a,b
Overall ADG (kg)	1.42^a	1.39^a,b	1.37^a,b	1.31^b,c	1.19^c

^a,b,c,d,e Indicate means in the same row with a different superscript letter differ (P < 0.05).

In cattle, AIP, or dust pneumonia in feedlots, is a sporadic respiratory condition lacking a well-defined cause. Many potential causes of AIP studied include tryptophan metabolism, fibrosing alveolitis, hypersensitivity, plant toxins, and viral and bacterial infections (Coggeshall et al., 1987). There are many etiologies that can be associated with AIP. Moving cattle from a heavily grazed pasture to a lush pasture in the fall may cause damage to the lung by pneumotoxins resulting from the ruminal conversions of forage derived L-tryptophan (Woolums et al., 2001). This disease can be easily confused with other forms of pneumonia, so a histological diagnosis is required (Woolums et al., 2001). The hallmark lesions or signs of AIP are fibrin accumulation and hyaline membrane formation in alveolar spaces, alveolar epithelial hyperplasia and congestion, and edema (Breeze et al., 1978). Regarding feedlot cattle, AIP is often a common disease observed. However, the cause of AIP in these feeder cattle is not as clearly defined. It is reported that most cattle that develop AIP in the feedlot have been on feed in a feedyard for longer than 45 days and is most prevalent in the summer or fall (Woolums et al., 2001). Climate can potentially increase incidence of AIP as cattle are susceptible to heat stress. Heat sensitivity may be the reason AIP is most often observed in the late spring through early fall (Griffin et al., 2017). When the ambient temperature reaches 21 degrees Celsius in the spring and cattle still have their winter coats, cattle may suffer heat stress, especially cattle with dark hides. High ambient temperatures can be associated with decreased feed intake, a change in eating patterns, and increased water intake (Griffin et al., 2017). In response to heat-stress, cattle modify eating behaviour and increase respiratory rate. Elevated ambient temperatures can cause changes in eating behaviour resulting in digestive upset which may increase AIP risk. This is especially true when daily ambient temperature approaches or exceeds the animal’s upper critical temperature of approximately 26 degrees Celsius (Berman, 1985).

Acute interstitial pneumonia generally occurs in 0.5–1.5% of cattle on feed during the months when cattle are at risk for the disease (Griffin et al., 2017). However, the rate of AIP during these months in cattle that have been previously treated for respiratory disease is 5–8% (Griffin et al., 2017). The risk for an animal developing AIP is 5–10 times higher if they have been treated previously for pneumonia than if never treated for respiratory disease (Griffin et al., 2017). Previous respiratory disease and AIP might be associated due to an incomplete healing of the earlier pneumonia in concert with ambient temperatures at or above the animal’s upper critical temperature (Taylor et al., 2010). The animal’s immune system walls off the remaining bacteria in small pockets. Although the animal may appear clinically normal, the bacteria may escape from their walled-off encapsulation via irritation by small particulate matter inhaled in feedlots. Because the animal’s immune system has been continuously stimulated by the encapsulated bacteria, should the bacteria break out and enter surrounding tissues, the animal’s immune system may react, which is considered a type of hypersensitivity. The surrounding lung tissue and spaces between the lung tissues, the interstitial space, will fill with fluid and reactive white blood cells. The animal’s immune response would then be responsible for the acute severe, life-threatening symptoms (Griffin et al., 2017).

PM is contained in every breath taken, by humans and by cattle. Particle size is of concern. The smaller the PM size, the deeper its deposition into the respiratory tract (Hartung & Saleh, 2007). While the nasal system can act as a preventive barrier to most foreign material entering airways, PM < 10 µm is generally small enough to enter the lungs and those <2.5 µm may penetrate into deep lung tissue and the subepithelial environment (Griffin, 2007). Dust clouds that contain this size PM might contain high concentration of organics composed of plant debris and even microorganisms such as fungal spores, viruses, bacteria, and pollen (Griffin, 2007). All of these constituents of dust can negatively affect animal health. Hartung & Saleh (2007) stated that inhalation of excess dust may overload the respiratory passages and mechanisms that facilitate infection. Antibiotics can also be observed in PM surrounding feedyards (Seltenrich, 2015). A study conducted by McEachran et al. (2015) sought to determine how feedyards specifically contribute to organics in dust. Dust was collected up- and downwind of 10 different cattle feedyards and showed significant increases in not only bacteria but also antimicrobial resistant genes in the downwind PM. McEachran et al. (2015) also determined that monensin was found in 100% of samples both up- and downwind, with a mean downwind concentration of 1800 ng/g PM. Tylosin was present in 80% of samples taken downwind and three tetracyclines were present together in 60% of downwind samples. Within the bacterial population in PM, six tetracycline resistant genes were significantly higher in the downwind samples (McEachran et al., 2015). With the ever growing concern of antibiotic resistance in livestock production, the presence of these materials in dust are an issue that may be addressed in future research.

Factors to mitigate dust in the feedlot

Producers can control the incidence of dust through different management methods varying in effectiveness and cost. Maintaining a damp feedlot surface has been shown to be one of the most effective methods of dust control (Sweeten, 1982). When the pen surface is between 7 and 10% moisture, severe dust problems occur; however, moisture levels above 40% create odour affecting employees and nearby properties. Therefore, it was noted previously that a pen surface moisture content between 25 and 35% is ideal (Sweeten, 1982). Foot rot is not cited to be an issue at this level of moisture, but producers are cautioned to be mindful of preventative measures regardless (Stokka et al., 2001). This can be accomplished with a variety of sprinkler systems. Permanent, fence-line, shade mounted, and portable sprinklers have each been shown to effectively reduce dust. Each sprinkler system has advantages and disadvantages depending on the operator and feedlot in which they are implemented (Sweeten, 1982). The time at which sprinklers are utilized also impacts dust control. By engaging sprinklers before dust producing occurrences or excess cattle activity, dust production can be reduced significantly (Amosson et al., 2006). Sprinklers have a large initial capital cost, but operating and labour costs are low during the lifetime of the equipment. Amosson et al. (2006) reported the initial project cost of a solid or permanent set sprinkler system for a 10,000, 30,000, and 50,000 head feedlot would be $30.74, $21.62, and $20.29 per head, respectively. However, the operational cost of these systems were $0.46, $0.40, and $0.39 per head marketed (Table 3). Water trucks are an effective method of dust control and have a lower initial capital cost (Darrington, 2016). However, labour and equipment costs are greater when compared to sprinklers. Ouapo et al. (2013) conducted a cost benefit analysis of a sprinkler system versus a water truck. The initial gross investment for a water truck is approximately $355,989 with an annual operational cost of $59,943. Whereas a sprinkler system has an initial gross investment of $785,260 and an annual operation cost of only $14,699 (Ouapo et al., 2013). When implementing a sprinkler system, it should be noted that the relative humidity increases. This prevents cattle from dissipating their excess body heat efficiently. In general, to increase the moisture content of a loose manure layer by 10% requires 21.19 liters per head per 2.54 centimeters (Auvermann et al., 2000). Therefore, scraping lots is also recommended in tandem with sprinkler systems for the greatest dust control effectiveness. It is recommended to thoroughly clean pens and remove excess manure to reduce dust production; loose manure should be kept at 5 cm or less (Darrington, 2016). To avoid the buildup of organic matter, scraping lots a minimum of once every 3–4 months is ideal (Darrington, 2016). A common practice is the scraping of lots once every turn of cattle, or 120–150 days (Auvermann et al., 2000). However, if machinery allows, manure should also be harvested at the midpoint of cattle feeding which improves dust conditions significantly (Auvermann et al., 2000). This can be accomplished with a variety of equipment including a tractor-drawn box or elevating paddle scrapers. The manure collected from pens should be removed immediately in order to prevent cattle from disturbing or redistributing the loose material collected (Auvermann et al., 2000). Introducing bedding is also a method that can mitigate dust without negatively impacting performance. Mader and Colgan (2007) showed that there was no negative impact on average daily gain (ADG) when implementing bedding to unsheltered feedlot surfaces while also significantly improving lot condition scores. However, during normal spring/winter months, reducing pen density proved to be more effective than bedding at maintaining a desirable lot score (Mader and Colgan, 2007).

Table 3. Total annual cost including fixed and operational costs ($/head marketed) for a solid-set sprinkler system based on a 25 year useful life for various feedlot capacities and turnover rates (Amosson, et al., 2006).

Head capacity	Turnover rate (head marketed/head capacity)	Fixed cost ($/head marketed)	Operational cost ($/head marketed)	Total cost ($/head marketed)
10,000	1.75	$2.08	$0.26	$2.34
	2.00	$1.82	$0.23	$2.05
	2.25	$1.62	$0.20	$1.82
30,000	1.75	$1.46	$0.23	$1.69
	2.00	$1.28	$0.20	$1.48
	2.25	$1.14	$0.18	$1.32
50,000	1.75	$1.37	$0.22	$1.60
	2.00	$1.20	$0.20	$1.40
	2.25	$1.07	$0.17	$1.24

Stocking rates are a potentially low-cost dust control strategy when properly managed (Table 4). By reducing the square meters per animal, or increasing stocking rates, from 9.29–16.25 square meters per head to 6.5–7.43 square meters per head, lot conditions can potentially be affected without sacrificing ADG (Mader & Colgan, 2007). While this information is related to mud and lot conditions, the added moisture from varying stocking rates can affect dust production. Cattle contribute to the moisture content of the lot surface via urine and feces (Table 5). A 454-kilogram steer at a spacing of 9.29 square meters per head produces 0.254 cm of moisture per day or 92.71 cm per year; whereas the same steer at a spacing of 6.96 square meters per head produces 0.33 cm per day or 120.52 cm per year (Sweeten, 1982). While Sweeten (1982) reported no detrimental effect on ADG, Auvermann et al. (2001) and Darrington (2016) warn improperly managed stocking rates may decrease ADG and feed efficiency.

Table 4. Performance and Carcass data of cattle housed with varying pen density (Mader & Colgan, 2007).

		Pen density^a
		Low	High	SEM	P-value
ADG, kg	Day 0 to 34	2.2	2.23	0.04	0.61
	Day 0 to 71	1.81	1.77	0.03	0.33
	Day 0 to 98	1.73	1.7	0.03	0.33
	Day 0 to 124^b	1.65	1.63	0.02	0.57
DMI, kg	Day 0 to 34	10.37	11.32	0.18	<0.01
	Day 0 to 71	10.17	10.9	0.17	0.01
	Day 0 to 98	9.9	10.62	0.16	0.00
	Day 0 to 124	10.03	10.83	0.18	0.19
F/G	Day 0 to 34	4.74	5.10	0.11	0.03
	Day 0 to 71	5.62	6.15	0.10	<0.01
	Day 0 to 98	5.72	6.28	0.11	<0.01
	Day 0 to 124	6.11	6.66	0.05	0.07
Marbling^c,d	–	563	527	7.6	0.00

^a Low = 46.45 m²/animal; High = 23.23 m²/animal

^b Final weight (d 124) calculated as hot carcass weight divided by a 62 dressing%age.

^c Carcass data was analyzed using the individual animal as the experimental unit.

^d Marbling score: 500 = Small⁰ (Low Choice); 600 = Modest⁰ (Average Choice).

Table 5. Manure moisture production in cattle feedlots (Sweeten, 1982).

Animal weight, kg	Average animal spacing, m^2/head
	6.96	9.29	11.61	13.93	16.25
	Moisture, cm/day
181	.127	.101	.076	.076	.050
272	.203	.152	.127	.101	.076
362	.279	.203	.152	.127	.101
453	.330	.254	.203	.177	.152
544	.406	.304	.228	.203	.177

Altering feeding schedule also impacts dust creation (Mitloehner et al., 1999). Cattle become more active in the evening hours. Dust-generating activity can be minimized by alternating the feeding schedule to encourage cattle to ruminate during this time. Mitloehner et al. (1999) reported 20% of cattle fed later in the day engaged in dust-generating behaviour compared to 69% of animals fed during conventional times.

Chemical agents demonstrating success in managing dust in poultry applications have shown little effectiveness in feedlots (Sweeten, 1982). Lignosulfate, sodium carbonate, calcium sulphate, calcium nitrate, and glycerol all have different modes of action controlling dust (Sweeten, 1982). However, limitations exist for each chemical. Chemical applications require a substantial amount of water to be effective as well as hindering the resale value of manure. Sweeten (1982) stated chemical application to feedlot surfaces at the rate of 0.2 kilograms per square meter resulted in effective dust control. However, the cost of this application was 50–80% more than treatment with only water.

Conclusion

Dust in feedlots can attribute to health concerns for cattle and ultimately profit losses for producers. Management methods exist to alleviate dust production in feedlots. By observing different practices such as increased stocking rate, sprinkler systems and/or altering feeding times, producers can potentially reduce the burden respiratory disease associated with dust.

Acknowledgements

PMU drafted the layout and writing of the first edition of the manuscript. BJJ, ZKS, AT, and FRBR edited the layout and content of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.