January, 1921. 



SCIENTIFIC AGRICULTURE. 



Mendelian lines, the two parents were not pure. 

 As t,he Merino ram-s were alniast certainly pure, it 

 almost certainly followed that the erossinfj results 

 showed a strain of Merino blood in the .Shropshire 

 ewe.s. Many ero«s-hred s^eep ai-e produfcd in 

 Australia, New Zealand and South America liy 

 crossing the Merino with Lustre or Down siieep. 

 In some few cases — for example, in the case of the 

 well-known Corriedale breed — it is claimed that by 

 many years of careful selection of rams and cul- 

 ling of ewe-s a stable breed ihas been pro<luced. 

 Mendelian research makes one very chary of ac- 

 cepting this claim without most careful substan- 

 tiation, but certainly suggests the truth of a 

 Colonial saying "tjiree generations to find a new- 

 breed and twenty to fix it." 



(d) The Merino breeds which, in a rongili form. 



were probably developed along the shores of the 

 Mediterranean and carried by the JMoons into 

 Spain, were so successfully developed that for 

 many years Spain supplied the wool manufacturer 

 of tjie world with practically all his fine wool. 

 Then SjLxony and Silesia ousted Spain from the 

 wool mai-kets of tihe world and were in turn 

 custed by Australasia. Today the Merino sheep is 

 sti-ongly in evidence in Australasia, South Africa, 

 South America the United States, and. as a spec- 

 ial breeding sheep, in France (the Rambouiilet). 

 It .still varies very much even in its pnre form. 

 Thus, the South American merinos usually pro- 

 duce t.he strongest merino wool, and the merino 

 .sheep of the inland districts of Australia and 

 Tasmania and the Cape some of the finest merino 

 wool grown. 



Efficiency of the Agglutination Test for Contagious 



Abortion of Cattle 



DAN. 11. JONES, Professor 



Agricultural C 



The agglutination test for contagit)US abortion of 

 cattle has been recommended liy various investigators 

 as a fairly satisfactory aiul practical method for de- 

 termining which animals in a herd are likely to give 

 trouble, cither hy aborting or acting as carriers of the 

 infection, thereby causing others to abort. Thus the 

 test should be an aid in the eradication of the infection 

 from a herd, as it indicates which animals should be 

 segregated. 



During tiie summer of 1920 it was the writer's privi- 

 lege to nuike the agglutination test for contagious abor- 

 tion on a herd of 33 pure-bred beef cattle, including 

 Shorthorns, Aberdeen-Angus and Herefords. and a 

 herd of 34 pure-bred dairy cattle including Holsteins, 

 Ayrshires and Jerseys. After the tests were completed 

 the previous history of the individual cows was ob- 

 tained from the herd liooks to determine to what extent 

 the positive and negative findings of tlie test were con- 

 firmed thereby. 



The test fluid used was a mixture of five strains of 

 "7?. aborfKs". Three of tlhese strains were obtained 

 from Dr. Huddleson. of Michigan Agricultural College, 

 and the otlier two from Dr. Rettger, of Yale. Cultures 

 of these strains were niade on nuti'ient agar slants and 

 grown for 72 hours at .'J7°C. The growth was then re- 

 moved and mixed with physicihigical salt solution, 

 filtered and diluted until a light clouded condition 

 obtained. The blood samples were obtained from the 

 jugular vein with sterile hypodermic needles. Tliese 

 were clotted in the ice-box over night, then centrifuged 

 and the seinim added to test tubes containing the test 

 fluid, giving dilutions of the serum 1-100 and 1-50 in 

 duplicate. The samjiles were then incubated at 37°C. 

 for 48 hours. Negative i-esults wei'c recoi'ded if both 

 dilutions remained (douded same as control, positive if 

 both cleared with formation of agglutiiuited clumps of 

 bacteria, and doubtful if the higher dilution I'enuiined 

 clouded and the lower dilution cleared. 



The beef lierd was made up of 22 breeding cows 2 

 years old ov over, 8 calves and 'A yearlings not bred. 

 The results of the test in this herd are as follows: 



)f Bacteriologv, Ontario 

 liege. 



Breeding cows that gave a positive reac- 

 tion and had history of abortion. . . . 



Breeding cows that gave a negative reac- 

 tion and had no history of abortion. . 



Value of test confirmed by 



Breeding cows that gave a positive reac- 

 tion and had no hi.story of abortion. . 



Breeding cows that gave a negative reac- 

 tion and had history of abortion .... 



Value of test negatived bv 



4 

 12 



8 

 1 

 9 



The group of 8 that gave a positive reaction and !iad 

 no hist(u-y of abortion included a 3-year-old that had 

 had 2 calves but was now difficult to breed, and an 

 ll-year-old that had had 9 calves and was again in calf 

 after rccjuiring tsix services. There is a possibility that 

 an invasion of "B. oborhis" might have been respon- 

 silde for the difficulty in breeding in these cases, 

 though, needless to say, other factors nnght have been 

 responsible. All the rest of the animals in the group 

 had had calves and were again in calf without any 

 trouble, notwith.standing t.iie fact that they gave a 

 positive reaction. 



Taking the above figures as they stand in con.iune- 

 tion with the al)ortion history of these lu-eeding animals, 

 the efficiency of the test is as 12 to 9. or a percentage 

 efficiency of 63.6. 



Calves that gave a negative reaction .... 8 



Calves that gave a jxisitive reaction .... 

 , Yearlings not lired tluit gave a positive 



reaction 2 



Yearlings not bred that gave a negative 



reaction 1 



One of the two positive reacting yearlings was from 

 a dam 13 years old that had had 12 calves and gave a 

 negative reaction; the other was from a 4-year-oId dam 



