Table 46. --Gross composition of fur seal milk, average 

 of six samples collected in 1963-66, St. Paul Island 



Component 



Percentage 

 of total 



Total solids 



Fat 



Protein 



Reducing sugars 



Ash 



Calcium and magnesium 



Phosphorus 



Chlorine 



63. 5 

 51.6 

 9.6 

 0. 11 

 . 51 

 .054 

 . 50 

 . 124 



pH - 6. 1 



CRYOGENIC MARKING 



Cryogenic or "freeze" branding is a rela- 

 tively new-*--"^ method of marking animals. When 

 extreme cold is applied to skin from which 

 the hair has been shaved to reduce insulation, 

 melanocytes (pigment cells) of the hair fol- 

 licles and dermis are selectively destroyed 

 without damage to the skin. Hair follicles so 

 treated produce only white hairs. In the sum- 

 mer of 1966, cryogenically induced white 

 hair had persisted for 10 months through two 

 shedding and regrowth periods in dairy cows 

 (Farrell et al., 1966). 12 Reversion to pig- 

 mented hair is not expected because hair that 

 turns white, for whatever reason--old age, 

 saddle sores in horses, and X-irradiation in 

 other animals--persists for life. 



Freeze branding has several advantages 

 over hot branding. Hot branding is painful 

 and causes inflammation, swelling, and scar- 

 ring which distorts the marks and restricts 

 their size. Freeze branding is relatively 

 painless and causes very little inflammation, 

 swelling, or scarring so that legible figures 

 as small as 1 cm. high and 2 mm. wide can 

 be produced. Wounds caused by hot brands 

 have a greater tendency to beconne infected 

 than wounds caused by freeze brands. White 

 hair marks produced by freeze branding are 



The first legible mark made on any animal by this 

 process was a 1.9-cm. high letter H formed from white 

 hairs produced by a superchilled, copper, horn branding 

 instrument applied to the hind limb of a dog by R. Keith 

 Farrell on 5 May 1965 (Farrell, Koger. and Winward, 

 1966). 



■"■^By 1968, when this manuscript was edited, the white 

 hair had persisted for 3-1/2 years and through seven 

 shedding and regrowth periods. 



legible at greater distances than hot brands, 

 depending on the size and the degree of con- 

 trast achieved. 



Disadvantages of freeze branding are: The 

 refrigerants are dangerous to personnel if 

 carelessly handled; "runs" may result if 

 too much refrigerant remains on the branding 

 instrument as it is applied; smears or blurs 

 may result from an animal's movement; and 

 contact may be incomplete when the surfaces 

 to be marked are uneven (Farrell et al., 1966). 



After preliminary tests by R. Keith Farrell 

 on black swine and a captive elephant seal, 

 cryogenic marking of fur seal pups was 

 tested on St. Paul Island in 1966. A round- 

 faced copper instrument in the form of an "S" 

 was chilled to -70° C. in a mixture of absolute 

 isopropyl alcohol and dry ice and applied to 

 both the naturally bare skin of the front 

 flipper, and the furred skin of the forearm. 

 The naturally bare or shaved surfaces were 

 first wet with alcohol. The struggling move- 

 ments of the pups during the process seemed 

 to be random attempts to get free and did not 

 necessarily coincide with application of the 

 instrument. From this we concluded that the 

 process was not painful. Exposure times 

 tested were 15, 20, 25, and 30 seconds. By 

 positioning the brands differently in relation 

 to the axis of either the right or left flipper, 

 we were able to distinguish the marks made 

 at each exposure time, during observations 

 of the pups from 13 July to 14 November. 



We applied brands to the dorsal surface of 

 either the left or right front flipper (manus) 

 of each of 40 pups on Zapadni Reef Rookery 

 13 July. The results are illustrated in figure 

 27. The frozen impression left on the skin 

 was visible for only a few minutes. An "S"- 

 shaped blister formed in 8 days, then peeled, 

 exposing a light pink "S" on the 13th day. 

 Healing was complete by the 22d day, but 

 partial or complete repigmentation was evi- 

 dent on the 41st day. We concluded that 

 cryogenic marking of the naturally bare skin 

 of the flipper is unsatisfactory because de- 

 pigmentation is not permanent. 



On 14 July, brands were applied to the 

 furred forearms (antebrachiums) of an addi- 

 tional 40 pups on Zapadni Reef Rookery. A 

 small patch of fur was first removed from 

 each marking site with electric clippers. The 

 results are illustrated in figure 28, One day 

 after branding there was some barely recog- 

 nizable "S"-shaped erythema and edema, but 

 initial scab formation produced legible marks 

 by the 7th day. The legibility of the marks 

 changed little between the 12th and 41st days. 

 During this time the scab and hairs exfoliated 

 and epithelium healed. White hair began to 

 show on the 41st day. Twenty seconds of ex- 

 posure produced the most distinct marks. 



""^^ Refrigerant runs off the instrument and freezes 

 skin next to the brand. 



47 



