COBALT-FEEDING EXPERIMENT AT AROHENA.

New Zealand Journal of Agriculture, Volume 54, Issue 6, 21 June 1937, Page 344

COBALT-FEEDING EXPERIMENT AT AROHENA.

C. S. M. Hopkirk,

Veterinary Laboratory, Department of Agriculture, Wallaceville.

In the latter part of 1936 an attempt was made to get representative farmers on the different volcanic showers of the centre of the North Island where bush sickness exists to carry out drenching trials with cobalt. This was considered necessary in order to find out whether there was a response to cobalt in the North Island ■ similar to that found by workers of Cawthron Institute in the South Island at Glenhope. Farmers in all areas where bush sickness was known to exist in cattle or sheep had become accustomed to feeding out limonite-salt licks, and on this account were rather loath to undertake the additional work which a drenching experiment would entail. An experiment became possible in two areas, however, the one the Government farm at Mamaku and the other the property owned by Mr. A. R. Weal, Arohena. Mamaku experiments are not yet sufficiently advanced to report. These two farms represented two different volcanic showers, that at Arohena being on the large Taupo shower. • Mr. Weal, who had had considerable trouble with bush sickness in his sheep in the past, very kindly offered to place ewes with lambs at the disposal of the Department of Agriculture and to carry out the necessary drenching of the sheep and lambs. Four groups were decided upon : • - (1) Four ewes to be dosed twice weekly with 3-5 c.c. of a solution of cobalt sulphate at the rate of 1 mg. of the cobalt salt per day ; four lambs to receive 3-5 c.c. of the same solution once a week. (2) Four ewes to be drenched with a solution of similar strength weekly, in doses of 7 c.c. ; four lambs to receive 3-5 c.c. once weekly. (3) Four ewes to be dosed once a month with 30 c.c. of the stock solution, while four lambs received 15 c.c. once a month. (4) Nine ewes and nine lambs to be left as controls.

All sheep were to be weighed once a month, and the state of health noted. Examination' of blood-samples was, unfortunately, not possible, because of the difficulty of obtaining samples and getting them to a laboratory.

Discussion. .The first two groups of ewes did well, and were at the last weighing in splendid condition. Their lambs also put on weight, and, except for the unaccountable death of lamb 619 after the first weighing, are in good order. The third group, where monthly dosing was carried out, did not do nearly so well. One ewe died, but not from bush sickness, while the lambs put on weight slowly. This group is intermediate in appearance between the first two and the last. The fourth group did badly, two ewes and four lambs dying. Others, which were getting extremely weak, were dosed with cobalt to save their lives. These are marked in the table. In appearance the group is very poor, and if cobalt had not been given the majority would have died. The experiment has shown that cobalt is efficacious in preventing bush sickness in the Aroliena district if given at regular intervals of once or twice a week. From previous work on elimination of the metal carried out by Askew and Josland, the optimum period for drenching has been shown to be twice a week, but with the amount given in this trial dosing once a week was quite sufficient. Dosing once a month was tried out because of the fact that some farmers have been giving large doses of 500 mg. and more at long intervals. Group three shows that the practice of dosing at intervals of a month is not sufficient to keep lambs growing at an optimum, although they remain healthy.

It should be pointed out that, although drenching with cobalt has been tried experimentally, it is not a practical method of control of bush sickness, as the labour involved is irksome and impossible when numbers of sheep have to be kept in health. The training of sheep and cattle to take limonite licks of high cobalt content is, as yet, the only practical means of controlling the mortality. . , • ■ ’ The thanks of the author are due to Mr. A. R. Weal, who made the experiment possible, and to Mr. G. Melrose, Inspector of Stock;. Te Awamutu, who weighed the sheep and supervised the experiment carefully and who supplied the photographs.

* Dosed on 15/1/37, 16/2/37, 17/3/37, and 16/4/37 with 30 c.c. cobalt owing to their showing signs of weakening. ' 1 Dosed on 15/1/37, 16/2/37, 17/3/37, and 16/4/37 with 15 c.c. cobalt owing to their showing signs of weakening.

— 13/11/36. 15/12/36. 15/1/37. 16/2/37. ’ 17/3/37. 16/4/37. Lot No.. r .- 4 Ewes, 4 Lambs. Ewe — No. 604 . . 129 135 131 137 143 126 No. 606 . . . . 139 145 140 142 : 151 . 159 No. 608 . . 119 126 122 . / ' 132 138 138 No. 610 .. . . 154 140 126 131 139 • 142 . Average weight .. I35-25 136-5 129’75 135-5 I42-75 141-25 Lamb No. 605 .. .. 36 51 61 72 80 88 NO. 607 : . . 35 47 - 66 81 88 84 No. 609 . . . . 16 21 34 43 49 53 No. 611 . . .. 29 42 . 55 • 58 73 81 Average weight ... 29 4 o -25 54 63-5 72-5 '76-5 Lot No. 2 .- 4 Ewe s, 4 Lam bs. Ewe No. 612 . . 114 124 118 148 . 134 144 No. 614 . . . . 115 123 98 ' .110 122 128 No. 616 128 . 142 121 130 141 141 No. 618 136 131 136 135 142 146 Average weight . . 123-25 13° 118-25 130-75 134-75 139’75 Lamb — ... No. 613 ... - . 3i 40 58 70 74 81 No. 615 25 39 55 . 65 70 77 No. 617 ... 28 43 61 78 82 87 No. 619 . . . . 19 . Dead Average weight 25-75 40-7 58 ' 71 75’3 81 -7 : Lot No. 5 1 . • 1 : 4 Ewes, 4 Lambs. s, 4 Lambs. Ewe No. 620 .. .'... 121 128 113 118 122 130 : No. . 622 . . ... 113 125 109 in . 17 120 ■ No. 624 ... 118 118 105 102 103 100 No. 628 123 126 107 ■ 81 Dead Average weight 118-75 124-25 108-5 103 114 116-7 Lamb — No. 621 ... 38 .59 . 76 80 79 80 No. 623 39 53 59 65 ' 60 63 No. 627 .. . . 22 28 35 34 35 40 No. 629 .. . . 27 44 57 60 ' 54 53 Average weight 31-5 . 46 5 6 -25 59-75 - 57 . ■ 59

— ■ . ■' 13/11/36. 15/12/36. 15/1/3716/2/37. 17/3/37. 16/4/37. Lot 4 ; . 9 Ewes, 9 Lambs. Ewe No. 630 . . 150 142 121 125 117 108 No. 632 .. 138 144 121 121 131 125 *No. 634 .. . . 118 106 ’ 90 88 85 ■ 88 No. 636 .. 138 • 152 133 . 130 139 128 *No. 638 . . . .. . 128 III 92 93 93 99 No. 640 118 104 Missing ‘ *No. 642 . . . 93 87 76 88 92 93 No. 644 . . .. . . 86 79 86 Missing *No. 646 . . . . 89 8.3 68 69 80 81 Average weight 117'5 112 98-4 102 105-3 103-1 Lamb — No. 631 . . 15 21 Dead No. 633 37 52 66 63 60 60 fNo. 635 24 29 20 Dead No. 637 35 53 62 71 73 70 fNo. 639 19 21 25 27 30 31 . fNo. 641 25 - 32 37 43 42 47 fNo. 643 3i 33 32 28 Dead No. 645 17 Dead : No. 647 ■ 22 29 28 3i 32 35 Average weight 25 33’7 38-6 43’8 47’4 48 • 6

Weights in pounds were obtained as follows:-