The objective of this study was to identify the risk factors associated with 3 presentations of hock lesions (hair loss, ulceration, and swelling) in freestall-housed lactating cattle. By independent identification and scoring of, and analysis of the factors associated with, hair loss, ulceration, and swelling, the aim was to identify whether risk factors were common to all 3, or differed among the presentations. A cross-sectional study was conducted on 76 herds in the UK during the winter housing period of 2007 to 2008, with a total of 3,691 cows examined for hock lesions. A randomly selected sample of approximately 50 cows in each herd were scored for body condition, lameness, cleanliness, rising behavior, and lesions at the hocks. For all cows, hair loss, ulceration, and swelling were scored separately on 4-point scales, with both left and right hocks scored. Based on a review of the literature, potential risk factors were identified and measured, collected from milk-recording data, or obtained through interviews with the farmers. Risk factors associated with hocks lesions in cattle were examined using data from the 2,982 cows housed in the 63 freestall-housed herds visited. Risk factors for each of the 3 lesion presentations were considered separately in multilevel logistic regression models, with moderate or severe hair loss, any degree of ulceration, and moderate or severe swelling as the outcome variables. Thirty risk factors were identified, none of which were common to all 3 lesion presentations. Five risk factors (locomotion score, number of days of winter housing, mean milk yield, freestall base material, and herd size) were common to both hair loss and ulceration. The stall bedding material was a common risk factor for both hair loss and swelling. A further 8, 5, and 11 risk factors were unique to hair loss, ulceration, and swelling, respectively. The existence of several differential risk factors between the 2 lesion presentations suggests that ulceration may not always be a direct extension of hair loss, as has been implied in previous scoring systems. Of the 12 risk factors associated with swelling, only 1 was common to another lesion presentation, which suggests that swelling may have a different etiology than hair loss and ulceration. The variables associated with the lesions indicate the importance of factors that affect the lying and rising behavior of the animal, including freestall structure and design, and the lying surface.

RX 821002 is the 2‐methoxy congener of idazoxan. In binding and tissue studies it behaves as a selective antagonist of α₂‐adrenoceptors, with at least 5 times greater affinity for these receptors than any other binding site. It does not select between the different types of α₂‐receptor. Although this drug probably has no future as a therapeutic agent, it remains a good probe for physiological activity at α₂‐adrenoceptors in animal experiments. A particularly useful feature of this compound is its lack of binding at I₁and I₂imidazoline receptors. However, it has relatively high affinity for 5‐HT_1Areceptors (at which it acts as an antagonist) and a tendency to behave as an inverse agonist at α_2A‐adrenoceptors in some cell culture systems. These potential drawbacks may be overcome by careful design of experiments, and the greater selectivity of RX 821002 renders it much superior to yohimbine or idazoxan as a tool for probing physiological actions at α₂‐receptors. It can be compared favorably with other selective antagonists such as atipamezole.In physiological studies, RX 821002 augments norepinephrine release in the frontal cortex and increases drinking behavior in rat. In rabbit, intrathecal administration of this drug enhances somatic and autonomic motor outflows, showing that tonic adrenergic descending inhibition of withdrawal reflexes and sympathetic pre‐ganglionic neurons is strong in this species. The potentiation of reflexes may be considered a pro‐nociceptive action. In the same model, RX 821002 antagonizes the inhibitory effects of the μ opioid fentanyl, indicating that exogenous opioids synergize with endogenously released norepinephrine in the spinal cord. Thus, the careful use of RX 821002 has revealed several aspects of the physiological activity of α₂‐adrenoceptors in rabbit spinal cord and rat brain. We recommend that RX 821002 and/or compounds with similar selectivity for α₂‐adrenoceptors (atipamezole, MK‐912, RS‐79948) should be used in preference to yohimbine or idazoxan in all future studies of this type.

1. Recordings were made from gastrocnemius medialis (GM), semitendinosus (ST) and tibialis anterior/extensor digitorum longus (TA/EDL) motor nerves during mechanical and electrical stimulation of the skin of the foot in decerebrated and spinalized rabbits. 2. GM motoneurones were excited from the heel and not from the toes, whereas TA/EDL responded to stimulation at the toes but not at the heel. ST also responded to electrical and mechanical stimulation at the toes, but there was a disparity between the effects of the two types of stimuli when they were applied at the heel: ST motoneurones fired in response to electrical stimulation of the heel but showed only an ‘off’ response to mechanical stimulation at this site. 3. The opioid antagonist naloxone caused a dose‐dependent increase in all reflexes evoked by electrical stimulation of the skin. The heel‐GM, toes‐ST and toes‐TA/EDL reflexes all increased to more than 3 times control levels with naloxone, which also caused significant decreases in the latencies of these reflex responses. On the other hand, the heel‐ST response increased to just 1.4 times control levels and showed no decrease in latency with the opioid antagonist. 4. These data suggest that segmental withdrawal reflex pathways in the rabbit are suppressed by endogenous opioid peptides. This opioid‐mediated inhibition seems to operate non‐selectively on reflex pathways between cutaneous afferents and motoneurones.