4.1. Summary of Main Findings
Housing systems vary within the beef cattle industry by stage of production and production outcome. Loose barn housing, compared to pasture housing, presents advantages and disadvantages to cattle welfare. Cattle housed in the loose barn had greater final live weights, ADG and BCS [
17]. Loose barn housed cattle also performed fewer mounting events [
15], spent less time vocalizing [
17], spent less time walking [
15,
17] and spent more time engaged in lying behavior [
15]. However, loose barn housed cattle spent more time standing [
17], engaging in agonistic interactions [
17], and performing oral explorative and oral manipulative behaviors [
15,
17]. Stravaggi Cucuzza et al. (2014) [
21] conducted a study to compare loose housing to tie-stall housing. His research group demonstrated that tie-stall housing was stressful to cattle in the fattening stage, as animals housed in a tie-stall barn had greater levels of total serum protein, serum lysozymes, fecal corticosterone, serum corticosterone and cortisol. From these findings, loose housing was considered more favorable in comparison to tie-stall housing.
Studies examining feedlot housed cattle observed that cattle in feedlots engaged in agonistic behaviors more frequently and for longer durations (e.g., headbutting, pushing, displacement) [
19] compared to cattle with access to pasture. Similarly, feedlot-housed cattle spent more time standing and walking, as well as engaged in lying for a shorter duration of time paralleled to cattle housed in a hoop barn [
18]. Environmental enrichment may be an effective environmental intervention that is designed to change feedlot cattle behavior, as this may increase the diversity and appropriately distribute the cattle’s behavioral repertoire. The intervention of environmental enrichment will be discussed in further detail later on in this review. Although studies were limited that examined veal calf housing, the findings provided overwhelming support for group housing compared to individual crates. Housing veal calves in groups resulted in a greater expression of social behaviors [
16], a reduced expression of stereotypic behaviors [
20] and improved carcass traits [
20].
Cattle can benefit from an increased space allowance in the feedlot. Feedlot environments that provided animals with 3.0m
2 to 4.5m
2 per animal had greater live weight gains [
25], as well as greater ADG [
27] and lower feed conversion rates [
23]. These animals performed a greater amount of positive social behaviors [
25], spent a higher percentage of their day lying [
22] and performed fewer abnormal behaviors [
22]. However, Fisher et al. (1997) [
25] found that cattle housed at a space allowance of 3.0 m
2 per animal, compared to those in an environment of 1.5m
2 per animal, had a greater mean- and peak-ACTH cortisol concentration. The authors of that study hypothesized that animals housed in the 1.5 m
2 per animal housing were restricted in movement, and therefore exposed to chronic overcrowding, which may have resulted in adrenal fatigue (e.g., a reduction of responsiveness in the adrenal gland to ACTH). Overall, feedlots that provided cattle with 1.5 m
2 per animal fared the poorest. Cattle in this setting spent less time lying [
23,
24,
25], indicating a decreased comfort state, as this behavior is an indicator of cattle comfort and animal managers have a goal of promoting lying as part of good husbandry and to promote productivity. Hickey et al. (2003) [
23] determined that highly stocked cattle did not interact socially as often as cattle with greater space allowances. High stocking density also had a negative impact on productivity and performance. Cattle that were provided 1.5 m
2 per animal had reduced ADG [
26,
27] and final body weights [
26], and also had higher feed conversion ratios [
23]. However, animals at this space allowance did have greater kill-out proportions, or ratios of carcass weight to live weight [
25,
26]. The findings from these studies indicate that the difference between providing 2.5 m
2 per animal to 3.0 m
2 per animal could be substantial regarding the improvement of cattle welfare. However, there is not a clear understanding as to when increasing space allowances no longer provides additional benefits. Furthermore, future researchers investigating stocking density should consider providing the average space allowance in final weight per m
2 for all treatments, as this could allow for more thorough comparisons of results moving forward.
Rearing cattle for fattening in a feedlot requires consideration of how flooring surfaces impact cattle welfare. Concerns have been raised regarding the use of fully slatted concrete floors, as this flooring type has been viewed as suboptimal for the animals’ welfare needs, particularly with regards to incidence of injuries [
1,
2]. This claim is partially supported by the findings of this scoping review. Cattle housed on fully slatted concrete floors performed greater frequencies of abnormal behaviors [
22], had more unsuccessful lying attempts [
38] and had a higher prevalence of health issues (e.g., skin lesions, locomotor disorders) [
38,
39] in comparison to fully slatted rubber mats. Fully slatted rubber mats resulted in greater live weight gains [
38,
40], ADG [
38,
40], feed conversions [
40] and fewer health issues [
22,
41]. However, cattle housed on fully slatted rubber mats performed more agonistic behaviors compared to those on fully slatted concrete floors, which may be attributed to the animal’s pain status, as cattle in less pain possess the resources to engage in behaviors needed to establish and maintain a social structure [
38]. Animals housed on fully slatted concrete floors, as well as animals housed on fully slatted rubber mats, displayed mixed results in comparison to specific mat conditions (e.g., foam structure rubber, natural rubber structure, partial cover of a solid mat, etc.), displaying both welfare advantages and disadvantages as indicated through behavioral, performance and health measures. For further detail, see
Table 6. Cattle housed on straw had a greater frequency of lying behavior [
22], improved hygiene scores [
42] and enhanced performance measures (e.g., improved feed conversion ratio, higher ADG, greater carcass weight) [
27]. These results suggest that cattle housed on straw floors had an enhanced welfare state compared to those housed on flat concrete, fully slatted concrete, or fully slatted rubber mats. This review highlights that there are advantages and disadvantages to all evaluated flooring types.
The benefits of implementing shade outweigh any possible negative impacts, and the findings from this review strongly support the implementation of shade in the feedlot setting. Access to shade allows cattle to have a choice to reduce thermal stress, in a manner that does not compromise their performance or welfare. Cattle housed in an environment with shade have lower respiration rates [
31,
32], and lower panting scores [
28,
29] compared to their counterparts without shade. Animals provided shade were more willing to eat, as shade reduced the impact of temperature highs during the middle of the day [
28]. Cattle with access to shade had numerous performance benefits, as well, including greater final body weights [
28,
29,
31], ADG [
29], DMI [
29,
30,
31] and G:F [
29]. The sole negative impact found of shade implementation was in conflict with another study. Gaughan et al. (2010) [
29] found that shaded cattle had a lower dressing percentage, in contrast to Hagenmaier et al. (2016) [
30], that showed that cattle in an environment with shade had greater dressing percentages. Therefore, the impact of shade on dressing percentage is unclear. As the EFSA Scientific Report (2012) [
2] recommended beef producers that housed cattle in confined houses or open feedlots implement structures to reduce the effects of thermal stress, the studies reviewed here demonstrate that providing shade could be a realistic solution, as overall, the listed benefits of shade outweigh the possible negative impacts, which were limited.
Inclusion of environmental enrichment in beef cattle housing systems may be the next step to advancing cattle welfare, as well as promoting a positive public perception of beef cattle production. Few studies were found that evaluated the impact of environmental enrichment on beef cattle, which is reflective of the scarcity of current literature available on the topic. However, the two studies that were evaluated demonstrated that environmental enrichment can have either a positive or neutral impact on cattle welfare. Ninomiya and Sato (2009) [
34] provided feedlot steers with a log and brush and found that steers with access to these items spent a greater percentage of time eating, yet no positive impact on productivity was observed. In another study, the impact of a grooming device was compared to different scent releasing (blank—no scent, lavender and milk) devices on feedlot heifers. Heifers interacted most frequently and for the longest duration of time with the rubbing device, followed by the milk-scent releasing device [
35]. The findings of this review suggest that, within a feedlot setting, environmental enrichment that allows animals to perform grooming behaviors may be biologically appropriate, as this is a behavior that cattle are highly motivated to perform and cattle willingly and regularly interact with a brush. Further research is needed to evaluate the long-term welfare consequences of environmental enrichment in all stages of beef cattle production.
This scoping review succeeded in investigating multiple research databases to gather the greatest number of studies related to the topic. More notably, the author (RMP) took additional approaches to review studies, by examining all the articles that were cited by accepted studies, as well as articles that cited the accepted studies. The consultation between the author (RMP) and a systematic review librarian (MF) was the greatest strength of this review. The National Academies of Sciences, Engineering and Medicine standard for systematic reviews calls for searches to be designed by information specialists and a recent study has shown that searches designed by librarians for systematic reviews improve the quality of reviews [
43,
44]. As the review was restricted to randomized controlled trials, there was the opportunity to assess the risk of bias for each individual study, which was viewed to be both an advantage and disadvantage. Conducting the risk of bias allowed for a more thorough analysis of these studies from a methodological standpoint, and it also assisted in determining features where beef cattle housing studies need improvement. However, this limited the review to only assessing randomized controlled trials, therefore excluding housing studies that did not fit the criteria of a randomized control design, which may have differing results that were not taken into account.
Conducting the Cochrane risk of bias analysis demonstrated that researchers in this field running randomized controlled trials are doing well in reporting results on all the measures obtained, as well as assessing animals on the same measures, regardless of what treatment they were allocated to. However, this analysis also determined areas in which beef cattle housing randomized controlled trials could improve. A statement of the random allocation of animals to treatment groups is inherent to randomized controlled trials and must be included in the communication of this research. There cannot be an assumption that readers will know that random allocation occurred. Additionally, researchers need to ensure the reader that there is not a deviation of data in the results due to the removal of animals from specific treatment groups. There was a lack of clarity in the majority of studies evaluated, as to whether animals were removed or not and if animals were removed, and no reference was made to how their removal impacted the study. Areas of the Cochrane risk of bias analysis that beef cattle housing studies did not excel in, and are not likely to improve in, include both allocation concealment and blinding of participants and personnel. There was a consensus in that no studies reported on whether the person enrolling cattle into the treatment had knowledge of the treatment allocation. In randomized controlled trials, knowledge of treatment allocation is considered to be selection bias. However, ensuring that the person enrolling cattle in treatments does not know of which treatment the animal are entering into would be difficult, due to the impossibility of blinding personnel to the treatments. In housing studies, the interventions were apparent, e.g., a clear distinction between fully slatted concrete flooring and deep litter. The differences of treatments were visual and obvious. While researchers were not able to change this concept in most housing studies, effort should be made to ensure readers understand the reasoning behind a non-blinded study, as well as knowledge of treatment allocation.