Fertility and production in dairy cows

Authors: Dawson FLM
Publication: New Zealand Veterinary Journal, Volume 20, Issue 9, pp 168-169, Sep 1972
Publisher: Taylor and Francis

Animal type: Cattle, Livestock, Production animal, Ruminant
Subject Terms: Animal production/wastage, Reproduction, Mammary gland/udder, Milk
Article class: Correspondence

---

Abstract: I have just read with interest the article by Dr Simpson on the relationship between production and infertility in dairy cows. I appreciate the notice he has taken of my work but I cannot feel that his method of analysis is fully valid. The shapes of individual lactation curves vary widely, hence it would be preferable to use completed 305-day lactation figures rather than two test yields at 6-monthly intervals. There is evidence (e.g., Dawson, 1968) that non-return at 49 days is more disappointing as an evidence of pregnancy in higher than in lower yielding cows. Hence a record of the birth of a full-time calf would be a more satisfactory basis of assessment than non-return. It might be relevant to know what proportion of cows in the herds surveyed was excluded because first served at less than 65 days after calving…

---