A comparison of farmers' sow culling decisions and model recommendations.

Culling data on sows recorded on the database of the State Veterinary Faculty, Netherlands were analysed, using an economic replacement model. The model determines a sow's optimum lifespan, and then calculates an economic index, called the retention-pay-off, which is the extra profit to be expected from keeping her until the optimum age and not replacing her immediately. For 1617 sows culled in 12 farms during 1985-86, the loss due to premature culling averaged Dfl. 124 per sow. The retention-pay-off for sows culled due to old age or low litter size was only Dfl.21, while for sows culled due to reproductive problems, it was Dfl.161. Further analysis of sows culled due to reproductive problems showed that those culled for failure to return to oestrus after weaning were being culled too early, while those culled for failure to conceive were being culled too late. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Experimental studies on seed production tropical grasses in Kenya. 6. The effect of harvest date on seed yield in varieties of Setaria sphacelata, Chloris gayana and Panicum coloratum.

Setaria sphacelata cv. Nandi I and Nandi III, Chloris gayana cv. Mbarara, Masaba and Pokot, and Panicum coloratum cv. Solai were grown for seed and harvested on a range of dates beginning 3-4 weeks after initial head emergence (defined as 5-10 heads/m2). Harvesting date was not very critical, and harvesting could normally be spread over 1-2 weeks. The interval between initial heading and optimum harvest date was normally 6-7 weeks. In most crops considerable shedding of spikelets (up to 30-50% in P. coloratum, rather less in the other 2 species) could be tolerated before yield of pure germinating seed fell with delay in harvesting. It was suggested that most of the spikelets which were shed early were empty. Cultivars which headed early produced nearly twice as much seed as those which headed late. (Abstract retrieved from CAB Abstracts by CABI’s permission)