|
290. Calf size is probably the greatest influence on ease or difficulty of calving but this can, to a large extent, be controlled by choice of sire and feeding management in the last four months of pregnancy.
291. Average gestation is usually from 275 days to 292 days but with the use of continental sires may lengthen to 300+ days. This will often result in large calves and calving difficulties. However, some breeds are renowned for producing small calves (35-45 kgs) and are widely used on maiden heifers. There is also considerable variation within a breed and it is difficult to predict ease of calving when using natural service, in contrast to AI where bulls with easy calving records are widely used.
292. Over-fatness is likely to lead to calving difficulties and subsequently infertility. Dairy cows should have a condition score at calving of between 2.5 and 3.0 depending on breed.
293. To reduce calving difficulties, care should be taken in the selection of sire. Cows should not be over-fat at drying off or parturition.