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Ovarian follicular dynamics were monitored in 12 surgically modified red deer hinds (ovaries adhered to vaginal wall) by transvaginal real-time ultrasonography during the luteal cycle, anoestrus and induction of superovulation. All 12 hinds showed evidence of regular luteal (plasma progesterone) cyclicity during the breeding season, although luteal tissue was not observed on the ultrasonograms. During the normal luteal cycle (14-22 days) total numbers of follicles > 3 mm did not vary significantly by day (range of means: 1.8-3.4; P > 0.05). A single large (> or = 6 mm) follicle was usually present on all days except immediately after ovulation (day 0). However, the appearance of new follicles (> or = 3 mm) was not random, and was greatest on day 1 and day 14 (P < 0.05). Tracking of individual follicles revealed irregular waves of emergence and disappearance of the largest follicle, with either one (n = 1), two (n = 3) or three (n = 5) waves observed across nine luteal cycles. New follicles (> or = 3 mm) emerged after regression or ovulation of a large follicle, suggesting a dominance effect. There were no significant differences in the overall mean numbers of follicles during early, mid- and late anoestrus (September, November and April, respectively) but follicle turnover was more rapid during mid-anoestrus as evidenced by a significantly greater number of new small (> 3 mm) follicles (P < 0.001). Administration of superovulatory doses of ovine FSH during the breeding season resulted in a marked increase in the appearance of new follicles within 48 h of initiation of the injection regimen. By termination at 96 h, the time of progesterone withdrawal, the mean number of follicles > 3 mm was significantly higher than for control hinds (9.8 versus 3.0; P < 0.0001). While most follicles ovulated progressively 2-7 days later, about 40% persisted beyond this period. The study demonstrated the presence of discrete patterns of antral follicle growth and regression during the breeding and non-breeding seasons, with the luteal cycle characterized by a variable number (1-3) of dominant follicle waves. Anoestrus represents a period of dynamic changes in follicular turnover.

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0.11 ± 0.10. The repeatability of plasma CC across seasons was 0.64 ± 0.02. The genetic correlation between spring plasma CC and milk CC g -1 fat was 0.66 ± 0.22, whereas genetic correlation estimates for spring plasma and milk CC g -1 fat with other traits were: with milk volume -0.01 ± 0.16 and 0.41 ± 0.35, with fat yield 0.06 ± 0.22 and 0.29 ± 0.54, and with fat% 0.03 ± 0.13 and -0.26 ± 0.29. It was concluded that plasma CC was a repeatable and heritable trait, whereas milk CC g -1 fat was lowly inherited; plasma CC was essentially uncorrelated with the standard milk production traits; if bulls were selected for lower plasma CC, there would be reduced CC in both the plasma and milk of their daughters.Keywords cattle; carotenoid concentration; heritability; genetic correlation; milk; plasma Abstract Blood and milk samples were collected in 1992/93 from 2-year-old heifers in the Livestock Improvement Corporation's Sire Proving Scheme, for analysis of carotenoid concentration (CC). The trial comprised heifers in 127 spring-calving North Island dairy herds, where blood samples were taken from a total of 2744 heifers (Holstein-Friesians (F), Jerseys (J), and their crosses) in early/mid lactation (spring), and from a sub-group of the same animals in autumn. These heifers were the daughters of 157 young F and J sires, and 15 older sires. Wholelactation yields of milk, fat, and protein, and fat% and protein% were also obtained. Sire-model restricted maximum likelihood (REML) analyses were carried out to estimate genetic and phenotypic parameters. Purebred F and J breed means for plasma CC in spring were 14.1 and 17.9 µg ml -1 (P < 0.001), respectively, and for milk CC 5.24 and 7.50 µg g -1 fat (P < 0.001), and corresponding heritabilities for the two traits were 0.46 ± 0.08 and A01025