**4.3 Special considerations in animal handling**

578 A Bird's-Eye View of Veterinary Medicine

Serial imaging also can be used to determine the extent and persistence of the vascular constriction response to toxicants. Following a reduction in luminal area and blood flow rate in heifers consuming diets consuming 0.4 or 0.8 mg ergovaline/kg DM, Aiken et al. (2007) reported adjustments in luminal area and blood flow velocity to original baseline measures, taken when heifers were on a 0 mg ergovaline/kg DM diet concentration adjustment diet, as air temperatures increased (Fig. 10). However, animals on control diets have shown greater variation in blood flow than those on treatment diets containing ergot alkaloids. Aiken et al. (2007; 2009b) concluded there was greater variation in caudal artery luminal areas and blood flow rates among control cattle compared to those on treatment diets (refer to standard error bars in Fig. 10), making it necessary to evaluate deviations from baseline measures for determine alkaloids effects. Low variation in caudal artery luminal areas among cattle on the treatment diet was suggested to be associated with persistent vasoconstriction causing

an inability to adjust their vasculature to changes in ambient temperature.

Fig. 10. Trends in luminal area of the caudal artery (a) and blood flow rate through the caudal artery (b) in heifer calves flowing placement of cattle on experimental diets (0, 0.4, or

Aiken et al. (2011) used color Doppler ultrasound to determine constriction of the auricular and carotid arteries in ewe lambs after they were switched from endophyte-free perennial

0.8 mg ergovaline/kg DM) (from Aiken et al., 2009b).

Accuracy and precision of measurements of blood flow characteristics in livestock are vastly improved if the measurements are collected in controlled environments with halter broke animals that are at ease with human contact. Furthermore, controlled diets fed in pens with know concentrations of toxicants will be necessary if research objectives are focused on determining sensitivities and strength of response to the toxicant. Blood flow measurements for pastured animals with minimal contact with humans will be affected by animal nervousness (e.g. increases in heart rate). However, measurements from ultrasound images are possible in uncontrolled environments and without halter-broke animals if control animals (e.g., animals grazing toxicant-free pastures) are measured and special animal handling procedures are followed.

Pastured cattle are typically handled in squeeze chutes with narrow alleys (Fig. 11) leading to the chute. Cattle are gregarious and individuals become nervous when singly separated from the group. When imaging cattle in squeeze chutes, the time individuals spend in the alley prior to being imaged should be minimized. Rather than crowding the alley, cattle should be placed in the alley in groups of three, with subsequent groups of three being placed in the alley such that an animal is not alone in the alley. Once in the chute, the sides of the chute should be reduced to not squeeze the animal to a point of discomfort, but reduce the area containing the animal. Potential nervousness of cattle worked in chutes makes it difficult to image cranial regions; therefore, imaging is better done if restricted to caudal regions (e.g., caudal artery or vein). The area should also be as quiet of sound, as possible, to minimize animal startling and raising of heart rates. Further, any sample collections (e.g., blood) or measurements (e.g., rectal or skin temperatures) should be done after imaging.

Imaging of horses can typically be done in stanchions with those that are haltered and at ease with humans (Fig. 12). Sheep and goats tend to also be gregarious, but do not present the same degree of nervousness as cattle. Small ruminants can be worked on cradles (Fig. 13) and provide opportunities to reliably image the cranial vessels (Aiken et al., 2011).

Imaging animals in an uncontrolled environment requires that images be collected over a period of time during the day with minimal changes in air temperature and humidity (Kirch et al., 2008). Imaging quality also is a major consideration in providing reliable interpretations and measures. Time must be taken to correctly place tranducers over the vessels, with sufficient gain and focus settings to optimize B-mode and color Doppler images, and Doppler spectra, Therefore, time of day and time necessary to collect quality

Doppler Ultrasonography

Fig. 13. Cradle used to restrain sheep.

nervousness and tension effects on vasculature blood flow.

(January 2009), 371-374, ISSN 0021-8812

179-184, ISSN 0048-0169

**5. Summary** 

**6. References** 

for Evaluating Vascular Responses to Ergopeptine Alkaloids in Livestock 581

Color Doppler ultrasonography is a non-invasive procedure that is routinely used to assess normal and abnormal blood flow in human and veterinary medicines. It also has application as a research tool in determining vascular responses to toxicants that can effect the vasculature. These studies are ideally performed in controlled environments with animals that are at ease with human contact and do not require restraint that can cause discomfort. However, reliable measures can be collected with pastured animals with minimal human contact if control animals with no exposure to toxicants are measured for comparisons with treatment animals, and special handling procedures are employed to reduce animal

Aiken, G.E., Sutherland, B.L., & Fletcher, L.R. (2011). Haemodynamics of lambs grazing

Aiken, G.E., Kirch, B.H., Strickland, J.R., Bush, L.P., Looper, M.L., & Schrick, F.N. (2007)

perennial ryegrass (*Lolium perenne* L.) either infected with AR6 novel, wild-type endophyte, or endophyte-free*. New Zealand Veterinary Journal*, Vol*.* 59, (June 2011),

Hemodynamic responses of the caudal artery to toxic tall fescue in beef heifers. *Journal of Animal Science*, Vol. 85, (September 2007), 2337-2345, ISSN 0021-8812 Aiken, G.E., Klotz, J.L., Kirch, B.H., Strickland, J.R., & Boykin, D.L. (2009a). Technical note:

Comparison between two tracing methods with ultrasonography to determine lumen area of the caudal artery in beef cattle. *Journal of Animal Science*, Vol. 87,

images must be considered. For each animal, five images for each cross-sectional and longitudinal section should be collected at each scanning session. A minimum of 5 animals per treatment should be scanned to account for the variation in blood flow characteristics between animals.

Fig. 11. Squeeze chute and alley used for to retrain cattle.

Fig. 12. A haltered horse in a wooden stanchion.

Fig. 13. Cradle used to restrain sheep.
