Consumption of endophyte-infected fescue seed during the dry period does not decrease milk production in the following lactation

Abstract

Ergot alkaloids in endophyte-infected grasses inhibit prolactin (PRL) secretion and may reduce milk production of cows consuming these grasses. We investigated the effects of consuming endophyte-infected fescue seed during late lactation and the dry period on mammary growth, differentiation, and milk production. Twenty-four multiparous Holstein cows were randomly assigned to 3 treatment groups. Starting at 90±4 d prepartum, cows were fed endophyte-free fescue seed (control; CON), endophyte-free fescue seed plus 3×/wk subcutaneous injections of bromocriptine (0.1mg/kg of body weight, positive control; BROMO), or endophyte-infected fescue seed (INF) as 10% of the diet on an as fed basis. Although milk yield of groups did not differ before treatment, at dry off (-60 d prepartum) INF and BROMO cows produced less milk than CON. Throughout the treatment period, basal concentrations of PRL and the prepartum increase in plasma PRL were reduced in INF and BROMO cows compared with CON cows. Three weeks after the end of treatment, circulating concentrations of PRL were equivalent across groups. In the subsequent lactation milk yield was not decreased; in fact, BROMO cows exhibited a 9% increase in milk yield relative to CON. Evaluation of mammary tissue during the dry period and the subsequent lactation, by quantitative histology and immunohistochemical analysis of proliferation markers and putative mammary stem or progenitor cell markers, indicated that feeding endophyte-infected fescue seed did not significantly affect mammary growth and development. Feeding endophyte-infected grasses during the dry period may permit effective utilization of feed resources without compromising milk production in the next lactation.

Effect of consuming endophyte-infected fescue seed on transcript abundance in the mammary gland of lactating and dry cows, as assessed by RNA sequencing

“…Consumption of ergot alkaloids was not assessed in the latter study and thus warranted additional study. We subsequently demonstrated that consumption of endophyte-infected fescue seed during the dry period did not significantly affect parameters of mammary growth nor decrease milk production in the subsequent lactation (Baldwin et al, 2016).…”

“…To ensure that treatment encompassed the final stage of mammary differentiation, treatment was continued until d 10 of the subsequent lactation, at which point it was discontinued. We concluded that although feeding endophyte-infected fescue during lactation decreased milk production, its consumption during the dry period did not affect milk yield in the following lactation after consumption of endophyte-infected fescue was terminated (Baldwin et al, 2016). In the current manuscript we used RNA sequencing (RNA-seq) to evaluate the influence of bromocriptine treatment and consumption of endophyte-infected fescue seed on gene expression in mammary tissue during lactation and the dry period, thereby revealing control mechanisms mediating these effects.…”

“…Tissue was immediately snap-frozen in liquid nitrogen for gene expression analysis by RNA-seq. The SCC at time of biopsy did not differ between treatments (Baldwin et al, 2016). An outline of processing for RNA-seq evaluation is provided in Figure 2.…”

“…As described previously (Baldwin et al, 2016), 24 multiparous Holstein cows from the Beltsville (Maryland) Agricultural Research Center Dairy were used in this investigation. Twenty-two of these 24 cows provided mammary tissue for the analysis of gene expression described in the current manuscript.…”

“…The treatment scheme, dry period, biopsy schedule (described below), and collection of milking records are illustrated in Figure 1. Additional experimental details are provided in our previous publication (Baldwin et al, 2016). All procedures involving animals were approved by the Beltsville Agricultural Research Center Animal Care and Use Committee.…”