Post-partum Anoestrus in Bali cattle under low-input animal production systems in Eastern Indonesia

Abstract

Bali cows (Bos javanicus) are a common breed in Indonesia and are favoured by smallholders for their size and ease of husbandry. However reproduction rates can be low in some areas and poor nutritional and reproductive management including poor mating management, low availability of genetically superior bulls, poor oestrous detection, poor Artificial Insemination (AI) procedures and poor availability of inseminators at the proper time are crucial issues which are likely to affect this. This thesis examined factors affecting post-partum anoestrus (PPA) and inter-calving interval (ICI) in Bali cows and heifers. This was examined by using large data sets to identify the factors which affect pregnancy rates in villages, developing methods to detect oestrus and pregnancy in villages, examining the effect of body condition score (BCS) on hormonal patterns and by quantifying milk production in cows. A large scale analysis of records from across the eastern islands of Indonesia indicated that there was a median inter-calving interval of 380 days but that post-partum anoestrus could not be determined precisely because of poor observations of first return to oestrus and mating. These records used observational data over 2-4 years where cows under various village management procedures were observed for weight, BCS and at least dates of calving from which various reproductive parameters could be calculated. ICI proved to be most useful and accurate given the quality of observed data. The range in ICI was very large and low annual calving % were recorded. There was an association of high reproduction rate with body condition score (BCS) at calving such that a BCS g3.5 (out of 5) was associated with inter-calving intervals of approximately 380 days. The median ICI across all sites was 380 days but some sites recorded 75 percentile values in excess of 500 days. In controlled pen experiments, faecal progestogens and vaginal electrical conductivity were examined as techniques to detect oestrus and pregnancy in the field. Faecal progestogens could be used successfully but there were problems with vaginal electrical conductivity in routine application and this requires more work. Cycling heifers were observed over complete cycles and plasma progesterone and faecal progestogens examined every 2 days. The pattern of faecal progestogen concentration over an oestrous cycle mirrored that of plasma progesterone and hence could be used to monitor the oestrous cycle and pregnancy but the sensitivity was low and a number of samples would need to be taken to detect the cycling pattern and/or pregnancy. Similarly cows were monitored over the oestrous cycle and vaginal electrical conductivity measurements made but the association was not strong or sensitive enough to be used routinely. Associations between plasma leptin or plasma IGF-1 concentration and BCS were examined in another controlled pen experiment and plasma IGF-1 concentration was increased in response to higher BCS but plasma leptin concentration was not affected. Heifers were fed two diets to result in two groups of moderate (l3.1 out of a scale of 5) or high (g4) BCS. Plasma IGF-1 reflected level of nutrition (higher concentration in high BCS heifers) and the resulting BCS (high or moderate) had an effect on cycling in cows and PPA whereby moderate BCS first calf cows showed complete anoestrus up to 100 days post-calving. In a village based experiment, milk production was measured for 12 weeks after calving and found to be low (1.7kg/d) and not related to stage of lactation or first calf cow or mature cow status. There was no evidence of lactation anoestrus for extended periods in this experiment in all cows but some cows had not exhibited oestrus after 84 days. Bali cows and heifers are inherently highly fertile and a simple management system of a target BCS at calving (at least g3), access to a bull or AI from 40 days post-calving and weaning of calves at 5-6 months of age (or earlier if BCS is declining fast due to poor nutrition) will enable annual calving or weaning % of approximately 80-90% to be achieved.