Comparative analysis of hatching rates and clutch sizes of Nile crocodile (Crocodylus niloticus) eggs collected on- and off-farm in Zimbabwe

The Nile crocodile (Crocodylus niloticus) is a large aquatic reptile predominant in the tropics in Africa and Zimbabwe in particular. Clutch sizes and hatching rates of Nile crocodile eggs collected from the wild and on-farm in Lowveld, Highveld and Kariba regions of Zimbabwe were evaluated. A total of 274 egg records for the period 2000 to 2008 from 39 farms were collected from the Crocodile Farmers Association of Zimbabwe. The effect of source of eggs was analysed using the non-parametric one way analysis of variance procedure of SAS Version 9.1.3. Wilcoxon signed rank test for independent samples was used to compare the mean hatching rates and clutch sizes for eggs collected from the different sources by region. The degree of association between clutch sizes and the hatching rates by source and region was determined using the Spearman’s rank correlation test. Source of eggs had no effect (P > 0.05) on hatching rates in all the regions but significantly influenced (P < 0.05) clutch sizes in Lowveld and Kariba. In these regions, clutch sizes in the wild were significantly (P < 0.05) higher than those on-farm. Correlation estimates between clutch size and hatching rates were weak and non-significant (P > 0.05) for the different sources of eggs in all regions. Full utilization of the wild resource would reduce challenges relating to shortage of captive breeders and high cost of rearing breeders and hence increase productivity.     

Production and economic performance of F1-crossbred dairy cattle fed non-conventional protein supplements in Zimbabwe

The effects of supplementing crossbred cows with non-conventional protein sources on dry matter intake, milk yield parameters and economic returns were investigated. Twenty-five lactating F₁ Holstein-Mashona crossbreds averaging 115?±?24 days in milk were used. Five treatments, total mixed ration (TMR), urea-treated maize stover, untreated maize stover, Macroptilium atropurpureum (Siratro) hay and veld hay, were randomly assigned to cows and replicated five times in a completely randomised design. Nutrient composition, intake, milk yield and economic returns were determined. M. atropurpureum hay, urea-treated maize stover and TMR had equal crude protein content. Daily dry matter intake and yield differed significantly among the treatment diets (P?<?0.05). Cows on TMR, urea-treated maize stover and M. atropurpureum consumed more (P?<?0.05) than cows on untreated maize stover and veld hay. Supplementing with TMR, urea-treated maize stover and M. atropurpureum hay increased (P?<?0.05) milk yields. Mean daily milk yield was highest for cows supplemented with urea-treated maize stover. Percent fat, protein and total solids in milk from cows fed urea-treated stover compared favourably to that of milk for cows supplemented with TMR. Income over supplement cost was highest for cows supplemented with M. atropurpureum hay and urea-treated maize stover. Urea-treated maize stover and M. atropurpureum can therefore be used as a replacer protein supplements for dairy cattle in Zimbabwe.     

Perspective on crop modelling in the management of intercropping systems

The risk to food security is particularly dire in rural sub-Saharan Africa, where a third of the world’s undernourished people reside. Intercropping has the potential to improve rural livelihoods through better resource utilization and improved resilience to current and future challenges. This paper reviewed the concepts in intercropping and outlined how resources are captured and utilized within the system. Crop simulation models (CSMs) as decision support tools for intercrop/multicrop systems and future directions for modelling multicrop systems are the focus of the review. Through increased crop biodiversity, intercropping improves resilience, food security and nutrition. This is achieved through improved resource capture and utilization due to differences in spatial and temporal distribution of component crops. For farmers to maximize on these advantages, they need to have a thorough knowledge of species combination, arrangements and proportions. A major drawback to intercrop systems is that most of the existing agronomic recommendations are tailored on monoculture practices. This is also evident in the structure of most CSMs that cannot account for heterogeneous crop stands. In conclusion, there is a need to enhance agricultural research on intercrop systems, combining conventional and modern research approaches. Moreover, CSMs should be multidimensional in order to simulate system diversity accurately.