The Impacts of Integrating Livestock into Cropping Systems on Soil Health and Crop Production

Effects of integrating livestock into small scale vegetable farming systems:

RESULTS

Tables and Charts for livestock and vegetable systems

Soil Bulk Density
There was no significant difference in bulk density measurements between the grazed and ungrazed treatments at Black Cat (P = 1.00), 13 Mile Lamb and Wool (P = 0.98), and Strike Farms (P = 1.00; Fig. 2a-2c).

Soil Nutrients
From 2017-2018 Strike Farms increased in Nitrate-N in both the grazed and un-grazed sampling areas (P< .01). There was no significant difference between Nitrate-N (ppm) when comparing grazed and un-grazed sampling areas within any year from 2017-2018. 13 Mile Lamb and Wool NH4+ (mg/kg) increased from 2017 to 2018 (P< .01), and then decreased from 2018-2019(P< .01). Nitrate-N ppm decreased from 2018 to 2019 (P< .01) at Black Cat Farms, but there was no significant difference between treatments (Table 2a – 2c).

Soil Microbial Diversity
Soil microbial ASV profiles clustered by location (ANOSIM Global R= 0.87, P(perm)=0.001; PERMANOVA F=9.4, P=0.001; Fig. Farm plot), this explained 24.7 % of the total variation observed. While all farms were very distinct from one another, Black Cat was less similar to either 13 Mile (R=0.952) or Strike (R=0.926) than these later farms were to one another (R=0.784). Samples also exhibited farm × year effects (R=0.739, P=0.001; F=6.2887, P=0.001; Fig. 3b., 12.4 % of total variation). Weak year effects were detected by ANOSIM between 2020 and either 2017 (R=0.237, P=0.001) or 2018 (R=0.229 P=0.001) and between 2019 and 2017 (R=0.275, P=0.001) and 2018 (R=0.285, P=0.001). No differences were seen overall between 2020 and 2019 or 2018 and 2017. No effects were detected for treatment, farm × treatment, or farm × year × treatment (P> 0.05). Consistently, no ASV was found to differ with treatment.

DISCUSSION

Soil chemistry, biology, and physical properties are all invaluable to the overall function of soil, as they drive the soil’s ability to hold water, sustain plant life and assist in resisting disturbance (Doran, 1999; Parr et al., 1992). Due to this, we sought to evaluate nutrient cycling, microbial communities, and compaction in response to grazed versus un-grazed vegetable cropping systems and understand the interaction between soil biology, nutrient cycling, and livestock when integrated into a variety of vegetable production systems.

Integrating livestock into each of the farms studied had no significant effect on bulk density when comparing the grazed and un-grazed sampling areas across all three years of the study (2017-2020). This finding is similar to other studies involving integrated livestock operations. In 2011, Liebig et al. (2011) found that at the USDA-ARS Northern Great Plains Research Laboratory southern research station in Mandan, SD soil infiltration rates (another measurement of soil compaction) were not significantly different among the livestock integrated annual cropping sequence and residue management that was hayed or left in place (CONTROL). Liebig et al. (2011) indicated that infiltration and compaction issues were not of concern when livestock were integrated into winter grazing systems due to the soil being frozen during grazing. Additionally, it was noted that soil in the Great Plains experience freeze and thaw cycles which mitigate any compacted areas created during grazing (Liebig et al., 2011).

On the contrary, other studies have indicated that integrating livestock into farming systems may have a negative effect on soil bulk density. When studying three farm locations in the Southern Great Plains, Krenzer et al. (1989) reported that cattle increased soil bulk density by as much as 16% when the livestock were allowed to graze red winter wheat (Triticum aestivum L.) during the fall and winter, following summer harvest (Krenzer et al., 1989). Soil compaction may be influenced by soil type, grazing level, precipitation, and location, so all variables must be taken into consideration when developing a grazing plan (Mapfumo et al., 1999).

By understanding the interaction between livestock grazing and soil nutrient cycles we can improve the knowledge base of how integrated livestock grazing impacts soil microbial communities and plant growth, as microbes are essential to nutrient cycling and nutrient cycling is essential for plant growth (Bhowmik et al., 2017; Wang et al., 2016). From 2017-2018 Strike Farms significantly increased in Nitrate-N (ppm) in both the grazed and ungrazed sampling areas. NH4+ (mg/kg) increased from 2017 to 2018 at 13 Mile Lamb and Wool and then decreased from 2018-2019 (Table 3.1a –c). Sheep grazing during fallow periods in wheat fields for weed control had some impact on NH4+ and NO3- when compared to tillage and herbicide weed management during a study conducted in SW Montana (Sainju et al., 2010). NH4+ and NO3- may increase with livestock grazing in grasslands (Wang et al., 2016). On the contrary, during our study Nitrate-N ppm decreased from 2018 to 2019 at Black Cat Farms (Table 3.1a-c). While some soil nutrients changed throughout the years of the study, no soil nutrients measured were affected by management type (grazed or un-grazed). Taking into consideration that each study site was tilled after grazing had occurred, tilling the soil may have made it difficult to observe any differences between treatments and only made it possible to detect differences between years.

While some research has explored the impacts that livestock grazing have on soil microbial diversity, little has been studied in terms of how integrated livestock grazing impacts soil microbial communities, specifically in horticulture systems (Chillo et al., 2017; Yang et al., 2013). Our study, which focused on changes in soil microbial diversity in livestock integrated systems, indicated that significant differences in soil microbial diversity were detected between farm locations, but no significant effects were detected for treatment, farm × treatment, and farm × year × treatment. Due to the size of the sampling areas (1-m2), the sampling plots may not have been large enough to distinguish between the effects of the treatment and environmental effects on the soil microbial communities. Such environmental effects known to impact soil microbial communities may include precipitation, climate, and other soil physical factors (Ishaq et al., 2017; Kaiser et al., 2016). Since soil microbial communities are affected by changes in soil and plant properties, it is understandable why the soil microbial communities are clustered by farm location, as each farm location had different soil properties (Table 3.1a-c; Fig. 3.1a).

It has been shown that plant composition may positively correlate with beta diversity, even after removing environmental factors, as was reported in a study conducted in temperate grasslands across four continents (Prober et al., 2014). With this understanding, it is possible that the plant composition at each of the farm locations had a larger effect on soil microbial diversity than the management of the farms. Another study in Eastern Australia indicated that any effects livestock grazing had on soil microbial community diversity were also indirectly impacted by changes in plant and litter cover and soil pH and N levels, so it may also be difficult to parse out any effects livestock grazing may have on soil microbial communities within the sampling sites as there are many other factors involved (Eldridge et al., 2019).

Soil microbes are quite mobile, and can move by active, passive and large organism facilitated transport. Passive movement occurs by water flow and wind and can move bacteria up to 400 mm with water flow and possibly up to 5,000 km with wind. Active movement allows microbes to move through the soil at much shorter distances than passive movement where they can move up to 7mm with the presence of water and the use of flagellates. Large organism facilitated transport occurs with the assistance of organisms such as earthworms, nematodes and protozoa where microbes can be transported throughout the soil while attached to these organisms (Yang and Dirk van Elsas, 2018). It is also possible that due to the small size of the sampling locations and the proximity of the grazed and ungrazed sampling locations that the microbial communities could have traveled between the areas. Along with environmental factors, soil microbial movement, and the size of the sampling areas, all the grazing exclosures were removed at the end of the grazing season to allow the landowners to till the study sites in preparation for seeding. The action of tilling may have also moved soil microbial communities around the study sites.

CONCLUSION

Results from this study indicate that integrating livestock into small scale vegetable farming systems in the Northern Great Plains does not have a negative impact on soil health measurements, including bulk density, soil nutrients and soil microbial communities. Further research utilizing larger sampling areas may assist in parsing out the environmental factors that play a large role in changes to soil microbial communities and could give a better understanding of the role livestock grazing plays on these communities. While no consistent differences in soil nutrients, bulk density and soil microbial diversity were found due to the treatments, grazing did not negatively impact any of the soil measurements among the years studied (2017-2020).
With the lack of research looking at the impacts of livestock integrated systems on small scale vegetable farms, there is a need for a better understanding of the relationship between livestock grazing of farming systems and soil health. Results from this study may help to demonstrate to farmers and livestock operators the importance of an integrated approach, for those that already practice this approach, they will have the affirmation that what they are exercising is feasible and purposeful and also become the starting point for further research into a little studied topic.

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Feedlot on Fields:

Link to published journal article with results tables here:

RESULTS AND DISCUSSION:

Performance
In North America, confinement-finished lamb-meat production promotes rapid growth and is based on diets containing high levels of grain concentrates. The majority of research has reported that lambs grow faster on concentrate-based diets than on forage-based diets (1-10) and ad libitum consumption of concentrates results in fatter lambs compared to those fed forage diets when the lambs are slaughtered at a constant final weight (2, 11, 12). However, there is a rapidly increasing demand for grass-fed or organically produced livestock (13) and in the U.S. retail sales of pasture-finished beef have risen from $17 million in 2012 to $272 million in 2016 (14).

A year × location interaction was detected for ending BW, ADG, and DMI; therefore results are presented by year. In yr 1, there were no interactions between location and feed (p> 0.29) for all response variables (Table 2). There was also no effect of location (p> 0.42) on ending BW, ADG, DMI, gain to feed, and cost of gain. Cost of gain and DMI were greater for CALF and FALF than for CBAR and FBAR feed treatments (p < 0.01) across all years. Gain to feed ratio was greater for CBAR and FBAR than CALF and FALF (0.15, 0.14, 0.12, and 0.13 G:F respectively; p = 0.01).

In yr 2, there were no interactions between location and feed (p> 0.32) for all response variables (Table 3). Location had an effect on ending BW and ADG, and both FALF and FBAR were greater than CALF and CBAR (p< 0.01). Dry matter intake, gain to feed ratio, and cost of gain had both a location and feed effect and differed among all treatments (p < 0.01; Table 3).

In yr 3, there was a location × feed interaction for ending BW and ADG (p=0.09 and p=0.08, respectively) (Table 4). Ending BW and ADG were greater for both FALF and FBAR than CALF and CBAR (p< 0.01). Feed had an effect on DMI and was greater for FALF and CALF which were similar (p= 0.03). This difference in DMI was expected as it has been reported that the decrease in DMI as a result of feeding higher proportion of concentrate can be attributed to the regulatory effect of dietary energy intake. Generally, animals eat food mainly to satisfy their desire for energy(15).Gain to feed did not differ among treatments (p=0.53). Cost of gain had both a location and feed effect and was highest for CALF and FALF ($4.15/kg and $3.72/kg, respectively; p< 0.01) than CBAR and FBAR with FBAR having the lowest cost of gain ($2.75/kg; p< 0.01). Even though the cost of gain was greater for alfalfa fed lambs, a survey conducted by Ripoll et al. (16) reported that 70.4% of consumers surveyed believe that grass-fed lamb is better and may be willing to pay a premium price for what they perceive as a “higher-quality product”. Also, Jacques et al.(17)concluded that using forage finishing systems may improve processing efficiency by reducing the amount of external fat to be removed by preventing excessively fat carcasses from lambs slaughtered. However, in our study there was no difference in back fat thickness among treatments (p≤0.33; Tables 5 and 6).

In yr 2 and 3, both field treatments had greater ending BW and ADG than the confinement treatments. In yr 1, extreme weather conditions (temperatures down to -29°C for ~ 1 week) may have affected animals in the field and had an impact on animal performance. Our results are in agreement with those of Phillips et al. (18) who reported that lambs can be adequately finished on a forage-based diet (alfalfa or kenaf) and doing so does not adversely affect performance or feed intake. McClure et al. (7) and Aurosseau et al. (19)also determined that finishing lambs on high-quality forages can yield similar ADG to those achieved in confinement feeding a concentrate diet while producing comparable carcasses.

Carcass
A year × location and a year × location × feed interaction was detected for dressing percentage; therefore, results are presented by year. In yr 1, there was no interaction between location and feed (p> 0.09) for all response variables (Table 5). Dressing percent differed by location but not feed; dressing percent was greater for FALF and FBAR than for CALF and CBAR (51.92, 52.85, 49.18, and 46.45% respectively; p< 0.02). Ribeye area differed by location but not feed; ribeye area was greater for FALF and FBAR than for CALF and CBAR (6.03, 6.32, 5.30, and 5.33 cm2 respectively; p< 0.02; Table 5). WBSF was greater for CALF and FALF than CBAR and FBAR (3.8, 3.8, 2.7, and 3.1kg respectively; p= 0.01). All other carcass measurements did not differ among treatments. Nichols et al. (20) reported that lambs overwintered on stubble fields graded choice after confinement feeding; however, they did not investigate alternatives to confinement feeding. There was no difference in quality grade amongst treatments or years; all treatments graded in the good-plus to choice-minus range (p≤0.77; Table 5).

In yr 2, there were no interactions between location and feed (p> 0.23) for all variables. Lambs in FALF and FBAR treatments tended to have greater leg scores and conformation than CALF and CBAR (p= 0.09). All other carcass measurements did not differ among treatments (Table 6). In our study we observed lambs in the field treatments exercising more than lambs in confinement pens; further research should be conducted to corroborate these observations and determine if exercise has an effect on leg scores and conformation. Our results are in conflict with the results of Jones et al. (21), where confinement fed lambs produced heavier carcasses and larger ribeye areas than pasture fed lambs. Our results are also in disagreement with Purchas et al. (22) who reported that WBSF values were significantly lower for M. seminembranosus in the pasture vs. grain treatments of 50 kg harvest weight lambs (4.04, 4.67 kg, respectively). In our study, location did not have an effect on tenderness but WBSF was greater for CALF and FALF than CBAR and FBAR (3.8, 3.8, 2.7, and 3.1 respectively; p= 0.01). Both Duckett et al. (23) and Realini et al. (24) reported that WBSF values were similar between forage and concentrate-fed animals. In our trial the forage-based treatment diet and grain-based treatment diet were both in concentrate-form with the same particle size. Past studies have only investigated forage-fed (in pasture or hay form) vs. concentrate-fed diets and therefore may not be comparable to our study. Forage particle size influences feed intake, saliva production, rumination, and the passage rate of feed in the rumen, as well as bio-hydrogenation pathways and fatty acid composition in lamb meat (25).

Blood
A year × feed interaction was detected for ending white blood cell counts; therefore, results are presented by year. In yr 1, there were no interactions between location and feed (p> 0.12) for all variables (Table 7). Both hematocrit and mean cell hemoglobin concentration were affected by feed and were greater for CALF and FALF than CBAR and FBAR (p<0.08).This agrees with the results of Gawel and Grzelak (26)who reported that alfalfa concentrate may be important as a dietary supplement for animals and may improve the hematological indices of blood. Mean cell hemoglobin and red cell distribution width differed by location; FALF and FBAR were both greater than CALF and CBAR (p< 0.06). All other blood counts did not differ between treatments. The principal clinical sign of Haemonchus contortus(H. contortus) infections is anemia, due to the blood-letting activities of the parasite (27).The cool season parasite T. circumcinta (formerly Ostertagia circumcinta) interferes with absorption of nutrients and may cause weight loss and possibly diarrhea (28).

In yr 2, there were no interactions between location and feed (p> 0.38) for all variables (Table 8). Red blood cell counts were affected by feed and were greater for CALF and FALF than CBAR and FBAR (p<0.07). The tendency for CALF to have greater white blood cell counts in yr 2, compared to other treatments, may be influenced by its abomasum T. circumcinta worm burden which was greater in CALF than all other treatments (p= 0.07).This would agree with the results of Ebrahim (29)who reported that blood samples taken from sheep infested with gastrointestinal parasites had greater white blood cell counts than sheep that were parasite-free. Kowalczuk-Vasilev et al.(30) reported that the use of iron-rich alfalfa concentrate in feeding lambs significantly improved hematological blood indices: hematocrit, hemoglobin and erythrocytes(RBC), and may be due to more efficient iron absorption. Hematocrit and mean cell hemoglobin differed by location and FALF and FBAR were greater than CALF and CBAR (p< 0.08). Variation in factors that affect the rumen bacterial community (diet composition, feed types, feeding strategy) can have a robust effect on rumen metabolism, which can impact both productivity and health of ruminants (31).Hemoglobin and mean cell hemoglobin concentration had an effect of both location and feed therefore they differed between all treatments (p< 0.06). All other blood counts did not differ between treatments (Table 8).

Parasites
A year × location and year × feed interaction was detected for H. contortus worm counts along with a year × feed × location interaction for T. circumcinta worm counts, Nematodirus worm counts and small intestine total worm counts, therefore, results are presented by year (p<0.01). In yr 1, there were no interactions between location and feed (p> 0.72) for all variables. Ending Trichostrongyle egg counts differed at p< 0.05. Ending Nematodirus spp. egg counts did not differ between treatments, although there was a tendency (p = 0.11) for CALF and FALF to be greater than CBAR and FBAR (Table 9).

In yr 1, there was an interaction between location and feed for small intestine total worm count (p< 0.01). FALF had a greater small intestine total worm count than all other treatments, CBAR was intermediate, and CALF and FBAR had the lowest counts (176, 18, 2, 0 small intestine worm count; p=0.01).An interaction between location and feed was also present for Nematodirus worm counts (p< 0.01). FALF was greater (p< 0.03) than all other treatments, CBAR was intermediate and differed from all other treatments (p=0.03) and FBAR and CALF were the lowest (p=1.00). All other worm burdens in the abomasum and first meter of the small intestine did not differ among treatments (Table 10).

In yr 2, there were no interactions between location and feed (p> 0.24) for all parasite variables. Ending Trichostrongyle type egg counts did not differ between all treatments (Table 11). Ending Nematodirus spp. egg counts were affected by location and feed and were greater for FALF and CALF (20.62 and 9.99 EPG respectively; p> 0.30), however CALF did not differ from FBAR (5.60 EPG; p> 0.44), and CBAR was lowest and differed from all other treatments (0.52 EPG; p< 0.03). It is unknown why CBAR had the lowest EPG in yr 2 but there was a tendency for both barley treatment groups to have lower EPG than the field treatments. It is widely accepted that a high grain diet causes a drop in ruminal pH and may cause drastic shifts in the rumen microbial community(32-35). Ruminal bacterial and protozoal populations increase or decrease in response to pH changes (33), however, the effect of pH on internal parasites has not been studied. It is possible that a lamb’s rumen environment is less favorable to internal parasites while consuming a high grain (barley) diet and thus we see lower EPG in these lambs; more research is needed to investigate this relationship.

In yr 2, there were no interactions (p> 0.11) between location and feed for all parasite variables. Abomasum H. contortus worm burden was greater in CALF than all other treatments (p= 0.07). All other worm burdens in the abomasum and first meter of the small intestine did not differ among treatments (Table 12). Marley et al. (36) determined that legume forages have the potential to contribute to the control of abomasal but not small intestine nematode parasites in finishing lamb systems. This is in contrast to our results where alfalfa-fed lambs in confinement had greater abomasum T. circumcinta worm counts than other treatments.

Parasite results are in conflict with those of Cai and Bai (37) who reported that gastrointestinal nematode eggs per gram (EPG) were lowest in lambs fed in confinement and highest in grazing lambs. Fecal egg counts (FEC) in our study appeared to trend with barley fed animals having lower counts than those of alfalfa fed animals. Studies have shown that the degree of parasite infestation in sheep may be reduced by some plant species (38-40). Research has focused on the effects of secondary plant compounds (e.g. condensed tannins) (41) on the reduction of parasites in the gut but the underlying mechanisms for such effects have not been determined. Overall in our study FEC worm counts taken from all slaughtered lambs were low and likely did not adversely influence the weight gains and hematocrit levels of the lambs.

CONCLUSION

Integrated crop and livestock systems as an alternative to confinement feedlot operations may increase marketing opportunities for sheep producers. While field finishing lambs with a grain- or forage-based diet, we conclude that it is possible to produce a quality lamb product without adverse effects to animal performance, carcass quality or increasing parasite burdens.

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