A recent study conducted by researchers at Royal Veterinary College in the United Kingdom investigated the effects of growth and metabolic indices during rearing on fertility. Heifers from 17 United Kingdom farms — representing a total of 428 animals — were involved in the study. Animals were measured at 30, 180 and 450 days of age for weight, height and girth, as well as metabolic indices including insulin-like growth factor-1 (IGF-1), insulin, glucose and urea.
    Fertility data collected included age at first breeding, number of services per conception, pregnancy rate and age at first calving.
    Researchers found the following in the study:

  • Average pregnancy rate to first A.I. was 67%.
  • Average age at first breeding was 473 days; average age at first calving was 791 days.
  • Body weight, girth, IGF-1 and skeletal growth increase were all associated with earlier age at first breeding.
  • Increased glucose concentrations at 180 days of age were associated with earlier age at first breeding.
  • No association between insulin and urea concentrations and fertility traits was identified.

Researchers concluded suboptimal growth associated with increased age at first calving can be improved through more intense heifer management during rearing.

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