Preservation of Bull Semen at Sub-Zero Temperatures

by N. L. VanDemark; M. E. Friedman; W. C. Kinney; W. J. Miller; Carlos Rodriguez

The results shown in [Tables 9] and [10] were confirmed also in later experiments. Thirty-six samples were subjected to various levels of glycerol and no significant difference in freezability was found between 6 and 8 percent. Based on these findings, a glycerol level of 7 percent was adopted for use in all experiments described in this bulletin, unless otherwise indicated. Results in a number of other laboratories have agreed with our findings regarding the use of approximately 7 percent glycerol with the yolk-citrate diluent.[5],] [6],] [7],] [9],] [10] With milk as the extender, 10 to 13 percent glycerol has been preferred by some.[5],] [6],] [7]

Table 9.—Effect of Glycerol Level on Sperm Motility
After Freezing to -79° C. and Thawing

Glycerol level (percent)		Number of samples	Pre- freezing motility (percent)	Post- thawing motility (percent)	Survival (percent)
	2	10	53	2	4
	4	19	55	29	53
	6	19	55	34	62
	8	19	55	35	64
1	0	19	55	24	44
1	2	10	53	13	25

Table 10.—Effect of Glycerol Level and Storage
at 5° C. After Thawing on Sperm Motility

(Average of 13 ejaculates)

Glycerol level (percent)		Sperm motility (percent)
		Post- thawing	After storage at 5° C.
			1 day	3 days
	4	29	22	20
	6	38	34	24
	8	42	33	17
1	0	33	18	6

Table 11.—Effects of Temperature, Rate of Addition of Glycerol,
and Equilibration Time on Sperm Motility

(Average of 12 ejaculates)

Temperature during addition of glycerol (° C.)		Equilibration time (hours)	Post-thawing motility (percent)
				Glycerol additions
				5		3		1		Average
	4.5	2		48		48		45		47.4
		6		49		51		47		48.8
		18		46		47		46		46.3
		Average		47	.8	48	.6	46	.0	47.5
1	0.0	2		44		43		45		43.9
		6		48		50		46		47.9
		18		43		46		42		44.0
		Average		45	.0	46	.5	44	.3	45.3
1	5.5	2		41		38		38		39.1
		6		42		45		43		43.6
		18		42		43		42		42.5
		Average		42	.0	41	.8	41	.4	41.7