Gene expression patterns in anterior pituitary associated with quantitative measure of oestrous behaviour in dairy cows

Abstract

Intensive selection for high milk yield in dairy cows has raised production levels substantially but at the cost of reduced fertility, which manifests in different ways including reduced expression of oestrous behaviour. The genomic regulation of oestrous behaviour in bovines remains largely unknown. Here, we aimed to identify and study those genes that were associated with oestrous behaviour among genes expressed in the bovine anterior pituitary either at the start of oestrous cycle or at the mid-cycle (around day 12 of cycle), or regardless of the phase of cycle. Oestrous behaviour was recorded in each of 28 primiparous cows from 30 days in milk onwards till the day of their sacrifice (between 77 and 139 days in milk) and quantified as heat scores. An average heat score value was calculated for each cow from heat scores observed during consecutive oestrous cycles excluding the cycle on the day of sacrifice. A microarray experiment was designed to measure gene expression in the anterior pituitary of these cows, 14 of which were sacrificed at the start of oestrous cycle (day 0) and 14 around day 12 of cycle (day 12). Gene expression was modelled as a function of the orthogonally transformed average heat score values using a Bayesian hierarchical mixed model on data from day 0 cows alone (analysis 1), day 12 cows alone (analysis 2) and the combined data from day 0 and day 12 cows (analysis 3). Genes whose expression patterns showed significant linear or non-linear relationships with average heat scores were identified in all three analyses (177, 142 and 118 genes, respectively). Gene ontology terms enriched among genes identified in analysis 1 revealed processes associated with expression of oestrous behaviour whereas the terms enriched among genes identified in analysis 2 and 3 were general processes which may facilitate proper expression of oestrous behaviour at the subsequent oestrus. Studying these genes will help to improve our understanding of the genomic regulation of oestrous behaviour, ultimately leading to better management strategies and tools to improve or monitor reproductive performance in bovines.

Central genomic regulation of the expression of oestrous behaviour in dairy cows: a review

“…TTR has been linked to anxiety (Sousa et al, 2004), MOBP to mood disorders (Sokolov, 2007), LTA4H to depression (Zhao et al, 2009), and KCNN2 to anxiety and stress responses (Mitra et al, 2009). A number of oestrous behaviour score-associated genes (Kommadath et al, 2010 and may be grouped in the fourth GAPPS module -Permission. For instance, the association between oestrous behaviour scores and the expression of acetylcholinesterase (ACHE) and several cholinergic receptors (CHRM1, CHRM3 and CHRNA5) can be explained by the effect of the neurotransmitter acetylcholine on arousal, plasticity and reward.…”

“…However, in a recent series of studies, gene expression in the anterior pituitary and four brain areas (amygdala, hippocampus, dorsal hypothalamus and ventral hypothalamus) in oestrous and luteal phase cows, respectively, has been measured, and the relation with oestrous behaviour of these cows was analysed (Kommadath et al, 2010(Kommadath et al, , 2011(Kommadath et al, and 2013Kommadath, 2012). Oestrous behaviour was recorded in 28 healthy primiparous Holstein Friesian cows in several consecutive cycles between 30 days in milk (DIM) until they were killed.…”

“…Day 0 of the cycle was determined on the basis of ultrasonographical examinations of luteal regression and dominant follicle development, which were performed daily in the days before the expected day of oestrus (expected oestrus was based on the previous oestrus and previous cycle lengths), while using observations of vaginal mucous and oestrous behaviour as additional information. In these studies (Kommadath et al, 2010(Kommadath et al, , 2011(Kommadath et al, and 2013Kommadath, 2012), a number of genes or gene clusters were found to have expression levels associated with the heat score. In the rest of this section, we describe how the results of these studies can be integrated within the framework of the GAPPS modules in rodents described in the previous section (see Table 3).…”

“…Several of the genes found associated with the heat score in cattle are related to synaptic plasticity (Kommadath et al, 2010(Kommadath et al, , 2011. These genes can therefore be considered to be part of the Growth module, which is characterized by oestradiol-dependent outgrowth of hypothalamic neurons.…”

“…For instance, the expression of oxytocin and arginine vasopressin genes in several brain areas of cows were associated with oestrous behaviour (Kommadath et al, 2010 and. Oxytocin, produced by the supraoptic and paraventricular nuclei of the hypothalamus, is released within the brain where it acts on specific oxytocin receptors to elicit effects such as female sexual receptivity, grooming behaviour and partner bonding (Leng et al, 2008).…”