The inability of the cat to convert significant quantities of linoleate [18:2(9,12)] to arachidonate [20:4(5,8,11,14]) in the liver makes the cat a useful model for studying the specific physiological roles of these two fatty acids. In these studies, cats were fed purified diets that were either deficient in essential fatty acids (EFAs) or that provided linoleate with or without arachidonate. Male cats that were fed the EFA-deficient diet for approximately 2 years exhibited extensive degeneration of the testes, and the fatty acid composition of testes changed in a manner consistent with EFA deficiency. Linoleate prevented testis degeneration. Levels of arachidonate, 22:4n6, and 22:5n6 were higher in testis phospholipids of cats supplied with linoleate than in the deficient cats, indicating that the testis of the cat has the capacity to desaturate and elongate linoleate. In contrast, female cats that were fed diets lacking arachidonate were unable to bear live kittens, whether linoleate was provided in the diet or not. Arachidonate, supplied by oral supplements of ethyl arachidonate or by animal fat in the diet, significantly improved reproduction. Thus, linoleate appears to meet the requirements for spermatogenesis in males, but dietary arachidonate is essential for adequate reproduction in female cats.

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ABSTRACT

Two experiments were conducted to produce Zn deficiency in, and to establish approximate Zn requirements of, the cat. In experiment 1, soy protein (SP)-based diets were fed for 8 months: diet 1, basal, without added Zn, 15 ppm; diet 2, basal, 15 ppm Zn plus 2% CaHPO4; and diet 3, basal with added Zn, 67 ppm. Gross Zn deficiency symptoms were not observed, although spermatogenesis in cats fed diets 1 and 2 was abnormal. There were no differences in food intake or growth rate between treatments. Mean plasma zinc levels (micrograms/100 ml) for cats fed diets 1, 2 and 3 were 55, 47 and 89, respectively. In experiment 2, the SP was washed with EDTA. Ten 8-week-old kittens were fed the following diets for 14 weeks: diet 4, SP without Zn, 0.7 ppm Zn; diet 5, containing 52 ppm Zn; or diet 6, an amino acid diet, 4.8 ppm Zn. Mean food intake (g/day) and weight gains (g/day) for cats fed diets 4, 5 and 6 were: 17.2, 0.4; 55.0, 19.5; and 31.5, 10.0, respectively. Mean plasma Zn levels (micrograms/100 ml) and liver Zn (ppm) for cats fed diet 4 had poor coats characterized by thinning and slow hair growth and scaliness of the skin and ulcerations of the buccal margins. The cat's requirement for zinc is probably between 15 ppm and 50 ppm.

Two experiments were conducted examining bilateral transfer of Hereford X Angus crossbred embryos to Angus, Hereford and Hereford x Angus crossbred recipients. In Exp. 1, both virgin heifers and parous cows were used as recipients, in Exp. 2, only virgin heifers were used. No differences in production of twins due to breed of recipient was observed. In Exp. 1, heifers had as high a twinning rate and proportion of pregnancies carried to term as cows. About 9% of the heifers in Exp. 2 experienced late gestation abortion (based on recipients pregnant at 42 d), a problem which was not observed among heifers in Exp. 1. No association between body weight at transfer and abortion was observed. Twin pregnancy was associated with a higher incidence of retained placentas (Exp. 1, P less than .05; Exp. 2, P less than .10), lower birth weight/calf (P less than .01 in both experiments) and shorter gestation period (P less than .01 in both experiments). Calf mortality at birth was similar among twins and singles and, in Exp. 2, a lower (P less than .02) incidence of dystocia was observed among heifers giving birth to twins than among those with single calves. The results of these experiments indicate that both beef heifers and beef cows of three common breed types are capable of maintaining twin pregnancies and successfully producing twins.