Section D. The Diseases of Dairy Cattle

Abstract

As the tuberculin test forms the most important method of diagnosing tuberculous infection, the need for the adoption of a reliable and uniform technique in its application is obvious. The three methods most commonly employed are (1) the ophthalmic, (2) the subcutaneous, and (3) the intradermal test. Following the issue of a publication by Buxton and MacNalty(i) the so-called double intradermal test has become widely recognised as the most satisfactory method of diagnosis. Its reliability and superiority over the ophthalmic or subcutaneous test is not, however, entirely unchallenged. Few workers place much reliance on the ophthalmic test, especially when used alone, but many well-known veterinarians retain considerable confidence in the subcutaneous test. Wilson (2) gives a comparison of results obtained by the subcutaneous and double intradermal tests. He points out that there is a greater degree of uncertainty in the interpretation of the double intradermal test than the subcutaneous test. In his opinion the double intradermal test errs, if at all, on the side of safety. That is, it will be more likely to indicate that a non-infected animal is a reactor than to give a negative reading in an infected animal. This opinion is shared by Smith (3). Tweed(4) mentions the difficulties involved in the interpretation of borderline cases diagnosed by the double intradermal test. He states that difficulties occur most frequently in thickskinned animals, and suggests that all genuinely doubtful cases should be retested at a later date using a broth control. Verge (5) holds that, while the double intradermal test is more complicated than the single intradermal, it is only slightly more reliable, since doubtful reactors still occur. The subpalpebral test is regarded by Smythe(6) as the most satisfactory. It consists of the subcutaneous inoculation of 3-5 minims of concentrated tuberculin into the base of the lower eyelid. Reaction is visible at the 24th hour but more marked at the 48th. Smythe maintains that this test eliminates the so-called doubtful reactors which are encountered with other tests. The present author has carried out this test on a number of animals, both reactors and nonreactors to the double intradermal test, and has found it quite satisfactory. He could not obtain, however, any evidence of its superiority over other methods, and he found its application more difficult. Gofton (7) maintains that the subcutaneous test, when carefully carried out and faithfully interpreted, is a most reliable and trustworthy diagnostic agent. Malcolm (8) gives it as his opinion that, if the human element could be eliminated in the manufacture of tuberculin and also in the application and interpretation of the tuberculin test, this test would become 100 per cent, efficient. Balozet, Zottner and Deviras(9) reported that, owing to the wide disagreement in the interpretation of both the double ophthalmic and single intradermal test, the results should always be confirmed by the subcutaneous test. Glover (10) stresses

Stressors Inherent to Beef Cattle Management in the United States of America and the Resulting Impacts on Production Sustainability: A Review

“…Conversely, others have reported that earlysummer calving resulted in adequate forage availability due to the higher crude protein concentrations that met nutritional requirements for the female with minimal supplementation [76,77]. During times of drought, the potential for aflatoxins is increased due to the growth of some species of mold [78][79][80]. This poisonous by-product can lower reproductive efficiency through abnormal estrous cycles and abortions, a reduced growth rate, and decreased feed efficiency [80].…”

“…During times of drought, the potential for aflatoxins is increased due to the growth of some species of mold [78][79][80]. This poisonous by-product can lower reproductive efficiency through abnormal estrous cycles and abortions, a reduced growth rate, and decreased feed efficiency [80]. The quality of the forage determines cattle forage intake, forage protein content, and mineral content, so when only low-quality forage is available, supplementation is often required [61,[81][82][83].…”