384 



SCIENCE 



[N. s. Vol. XXXVI. No. 925 



that the ewes should be iu prime physical con- 

 dition at the time of mating. 



To secure this point we breed in October; 

 and it has also been our custom for some years 

 past to provide the ewes with extra nourish- 

 ment in the form of oats, oil-cake, etc., for 

 two or three weeks before mating. 



In order to be perfectly sure that each ewe 

 receives her proper share, individual feeding 

 pens have been provided. 



When a common trough is used the larger 

 and stronger sheep, who need it least, get 

 most of the food; and the smaller and weaker, 

 who need it most, get least. 



Nutrition After Mating. — Our records of 

 weight indicate that there is a characteristic 

 difference in the weights of twin-bearing and 

 single-bearing ewes after mating. 



The twin-bearing ewes, on the average, 

 show a marked and even sudden dropping ofE 

 in weight within two or three weeks after 

 mating, which is not found in the ease of the 

 average single-bearing ewe. 



This may be translated to mean lowered 

 nutrition after mating as a characteristic of 

 the twin-tearing ewe; and a consequent lessen- 

 ing of the growth of the unborn lambs, so that 

 when the twin lambs are ultimately born they 

 are of smaller size and weight than the aver- 

 age single lamb. 



We sometimes find that twin lambs are 

 very unequal in size at birth. If one is large 

 the other is likely to be small and even de- 

 formed, indicating a struggle for existence 

 between the unborn lambs. 



This led me to suspect that many of our 

 largest single lambs might be the survivors 

 of twins; and a few years ago I had a young 

 physician from Washington (Dr. Phelps) 

 visit Beinn Bhreagh at the lambing season 

 to see what he could discover bearing upon 

 the point. 



He was able to examine quite a number of 

 the after-births of the sheep; and in several 

 cases where single lambs had been produced 

 he found indications in the after-birth of an 

 aborted twin. 



In this connection it is suggestive that our 

 best twin-bearing ewe, No. 1505, which has 



given us already four sets of twins, produced 

 this year a single lamb weighing ten pounds 

 at hirth! It is notorious also, that fat stock 

 are remarkably infertile, and rarely bear 

 twins. 



All these considerations led to the belief 

 that lessened nutrition during the period of 

 gestation is a condition that is favorable to 

 the preservation of unborn twins. Good nu- 

 trition at the time of mating favors the con- 

 ception of twins; and diminished nutrition 

 after mating favors their retention. 



It is obvious, upon reflection, that ewes can 

 not successfully bear twins, or a litter at birth, 

 unless the lambs born are small; and lessened 

 nutrition during the period of gestation is 

 eminently favorable to the production of 

 lambs that are small at birth. 



These considerations led to the policy of 

 giving the ewes extra nourishment in the 

 form of oats, oil-cake, etc., for some time be- 

 fore mating; and then cutting off the extra 

 feed soon after mating so as to throw the 

 ewes back on the pasture alone for support. 



A better, and certainly more economical 

 plan, affecting the condition of nutrition in 

 the same way, would be simply to mate in 

 October when the pasture is at its best, and 

 then give hay alone for winter feeding. The 

 giving of oats, oil-cake, roots and other milk- 

 promoting food might weU be postponed until 

 about the time of lambing, so as to avoid 

 stimulating the growth of the lambs until 

 after they are born. 



In order to raise twins and triplets success- 

 fully the lambs should be small at birth, and 

 grow large afterwards. 



If we had a large number of twins from 

 which to choose, it would be a good plan in 

 the spring to retain only those lambs which 

 are under the average weight at birth; and 

 then, in the autumn, select from these those 

 that are over the average weight. This proc- 

 ess carried on through a series of generations 

 would probably result in a breed of sheep pro- 

 ducing, as a normal condition, lambs that are 

 small at birth and which grow large after- 

 ward. 



Alexander Graham Bell 



