150 days, which is characteristic of Bos indicus/Bos Taurus cattle, resulting in a prolonged calving index. The average calving index was 16.8± 5.2 months in Rwandan cattle. Late onset of puberty,
Table 2 Effect of BCS on reproductive performance BCS
% not cycling on rectal palpation*
<2.5 2.5–3.5 >3.5
64.5 44.6 28.9
* Total of 150 cattle examined
Trop Anim Health Prod (2008) 40:181–184
prolonged anoestrus and calving index were the cause of poor reproductive performance in Rwandan cattle, which is in agreement with similar studies on Bos indicus, Bos Taurus and B.indicus/B.taurus crosses (Baruselli et al. 2004; Azage et al. 1993; Lyimo et al. 2004 respectively). The poor reproductive performance caused a reduction in the number of calves produced in the cow’s life time, the number of lactations and therefore milk production. This results in economic losses. (Butler et al. 1981; Savio et al. 1990a,b; McDougall et al. 1995; Opsomer et al. 1996) Table 1, shows the effects of breed on reproductive performance. Crossbred cows are younger at first oestrus compared to Ankole cows (t=1.94; df=121; p<0.05). Ankole cattle had a later onset of puberty compared to Crossbred cattle, 28.4 and 23.4 months respectively. However, there was no difference in the length of postpartum anoestrus and calving index in Ankole and Crossbred cattle in this study, suggesting that the poor reproductive indices are more likely to be due to environmental conditions and husbandry practices rather than genetics. On the whole, cattle were in good condition and had an average BCS of 3.2±1.1 because the study took place at the end of the rainy season when grass had been widely available. Further studies would benefit from monitoring changes in BCS throughout the year to determine the effect of seasonal variation in quantity of grass. The effect of BCS on proportion cycling is presented in Table 2. Thin cows are 1.45 times more likely to be in anoestrus as normal cows and 2.23 times more likely than fat cows (χ2 =9.476; df=2; p<0.01). The low BCS reflects a poor availability of nutrients and periods of negative energy balance. This is in agreement with other studies reporting that under nutrition due to dependency on poor quality natural forages and high parasite burdens is the main hindering factor in cattle reproduction in tropical regions (Lyimo et al. 2004; Montiel and Ahuja 2005; Shiferaw et al. 2005). Pearson’s correlation co-efficient showed no significant correlation between milk yield and interval from parturition to first oestrus (Coefficient=−0.038; p<0.185) and calving index (Coefficient=−0.002; p< 0.246). However, there was a positive correlation between the weaning age and interval from parturition (Coefficient=0.26; p<0.05) and calving index (Coefficient=0.54; p<0.01). This is in agreement with other studies of tropical cattle demonstrating that, late wean-
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ing of calves is a common occurrence due to financial constraints and to aid milk let-down in the cow, and is a major cause of prolonged anoestrus (Lyimo et al. 2004; Msanga and Bryant 2004). In conclusion, to make farming more profitable in Rwanda it is vital that the reproductive performance of cattle improves. There are many challenges facing Rwandan farmers if they are to succeed. The major constraints, according to this study, are the age of weaning, poor oestrus detection and poor nutrition. To improve these factors, many farmers would benefit from increased training and experience in cattle rearing. Acknowledgements The author thanks Stan Lee for his help in translating the questionnaire, acting as a translator and helping in all matters practical, special thanks to Marlene Lee for her hospitality during my stay with them in Rwanda.
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