Stress and subfertility in dairy cows

Jerome Morris, Michael (2008) Stress and subfertility in dairy cows. PhD thesis, University of Liverpool.

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Abstract

In commercial dairy cattle farming, stressful disease conditions, such as high somatic cell count (SCC), poor body condition score (BCS) or lameness, are associated with subfertility. The objective of this thesis is to identify key areas in the reproductive cycle associated with each condition which contribute to this subfertility. Cows 30-80 days post partum from two commercial dairy farms were scored for SCC, BCS and lameness over a 5 week period prior to the implementation of an oestrous synchronization programme. Blood and milk sampling, trans-rectal ultrasonography and oestrus behaviour monitoring were conducted. Follicular development from emergence to deviation was unaffected as all cows produced a dominant follicle, which continued to grow beyond lOmm. In the following period, mean follicular growth, maximum follicular diameter and time to ovulation were not influenced by any of the 3 conditions (p> 0.05). In the animals that ovulated (irrespective of clinical status), follicles grew faster and achieved a greater diameter than in the animals that failed to ovulate (p< 0.05). Fewer lame animals ovulated compared to healthy animals (p< 0.05) and fewer high SCC animals with concurrent lameness ovulated than cows with only high SCC (p< 0.05) In cows with high SCC, progesterone concentrations prior to PG injection, over the peri-ovulatory period, on Days 5 and 7 or during the mid luteal phase after ovulation were unaffected, as was mean oestradiol concentration prior to ovulation. In the cows that ovulated, the dominant follicle grew at the same rate and ovulated at a similar size and at the same time regardless of high SCC, lameness or both. High SCC cows tended to (p< 0.07) and lame cows did express an oestrus of lower intensity and had a lower maximum intensity score than healthy animals (p< 0.05). High SCC cows started displaying oestrus signs and stood to be mounted (STBM) later than their healthy counterparts (p< 0.05) while lame animals displayed oestrus and STBM earlier than non lame cows (p< 0.05).

Item Type:	Thesis (PhD)
Depositing User:	Symplectic Admin
Date Deposited:	20 Oct 2023 09:24
Last Modified:	20 Oct 2023 09:43
DOI:	10.17638/03174429
Copyright Statement:	Copyright © and Moral Rights for this thesis and any accompanying data (where applicable) are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3174429