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The Carotene and Vitamin A Content of Plasma and Liver of Range Hereford Cows and Their Calves in the Northern Great Basin¹

Squaw Butte-Harney Range and Livestock Experiment Station^,2

Abstract

Blood plasma and hepatic levels of carotene and vitamin A are reported for cows with carotene intakes of 1.5, 5, 15 and 25 mg. per 100 lb. body weight, respectively by groups I to IV.

Plasma and liver carotene showed a direct relationship to carotene intake during the four-month winter feeding period, and when cows grazed range forage. Hepatic vitamin A reserves were not maintained even at the highest rate of carotene intake during the winter feeding period. Liver vitamin A levels of cows in these high groups increased when they grazed green sagebrush-bunchgrass range during early summer. A continual decrease of the plasma and liver components was noted for cows that were maintained on bleached hay for 10 months and straw for 2 months.

Plasma and liver values of carotene and vitamin A of cows and their calves on the usual range management regime were also investigated. Increased levels were noted when they grazed green range forage, and decreased levels when they grazed cured range forage. Carotene levels increased slightly when they grazed meadow aftermath and continued to increase on green meadow hay. A delay in peak hepatic vitamin A reserves compared to plasma carotene and vitamin A and liver carotene values on summer range was noted.

Cows in group I showed vitamin A deficiency symptoms only after 350 days on the bleached hay and straw ration. In 1955 night blindness was manifested in one-month-old-calves from cows on carotene intakes of 1.5 and 5 mg. per 100 lb. of body weight. The response in plasma and liver levels of these calves to grazing green meadow for one month is presented.

These data indicate that pregnant cows accumulate large stores of vitamin A when grazing spring range which will supply their vitamin A needs during winters even when very low levels of carotene and vitamin A are available in their rations. Vitamin A deficiency may be expected in young calves that are nursing their dams when they are not permitted to consume at least small quantities of hay or other carotene bearing feeds. Such conditions are unusual.

¹ Approved for publication as technical paper 999 by the Director of Oregon Agricultural Experiment Station.

² Burns, Oregon. Jointly operated by the Agricultural Research Service, United States Department of Agriculture and Oregon Agricultural Experiment Station. Oregon State College, Corvallis.

³ Department of Agricultural Chemistry, Corvallis.

⁴ Formerly Animal Husbandman, Squaw Butte Station, present address: Department of Animal Husbandry, Cornell University, Ithaca, N. Y.

⁵ Formerly Animal Husbandman, Squaw Butte Station, present address: Department of Animal Husbandry, Iowa State College, Ames.