Reproduction in female cattle in a communal farming area of Zimbabwe.

Cattle in a communal farming area of Zimbabwe were identified and examined in the late dry and mid wet season of 1985/86. Ovarian activity rates were 17.9% and 38.6% in the dry and wet season respectively. Pregnancy rates were 16.1% and 24.6% respectively. A major limitation to reproduction was the percentage of anoestrous females. There was no evidence of a seasonal calving pattern. Median body condition score was 2.0 in the dry season and 1.5 in the wet season. Adult females of body condition score 2.5 and above had ovarian activity rates of 41.9% and pregnancy rates of 41.9 per cent. Those with a body condition score below 2.5 had rates of 26.8% and 16.4% respectively. Serum progesterone levels in pregnant animals were positively related to body condition score, with some animals having progesterone levels similar to non-pregnant animals. Metabolic profiles suggested that the major limiting nutrient in both seasons was nitrogen, although other micronutrients might also be involved in low reproductive rates.