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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Genomics and Improvement Laboratory » Research » Publications at this Location » Publication #309857

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

item Baldwin, Ransom - Randy
item CAPUCO, A - Former ARS Employee
item Clover, Christina
item GROSSI, P - Catholic University Of The Sacred Heart Italy
item CHOUDHARY, R - University Of Kentucky
item VANZANT, ERIC - University Of Kentucky
item Elsasser, Theodore
item BERTONI, GIUSEPPE - Catholic University Of The Sacred Heart Italy
item TREVISI, ERMINIO - Catholic University Of The Sacred Heart Italy
item Aiken, Glen
item MCLEOD, KYLE - University Of Kentucky

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary: Ergot alkaloids produced by the endophyte fungus concentrate in the vegetative matter consumed by pasture fed cattle dramatically affect thriftyness with specific effects including weight loss, hair loss, spontaneous abortions, and loss of productivity. We evaluated the impact of feeding endophyte-infected fescue during late lactation and the nonlactating (dry) period between lactations on milk production characteristics and physiological parameters such as body temperatures, mammary tissue development during exposure, and blood bourne hormone concentrations. Milk yield of cows consuming endophyte-infected fescue was reduced during late lactation. But after consumption of endophyte-infected fescue throughout the dry period, milk yield tended to exceed that of controls. Possible increases in milk yield may result from observed hormonal changes that were analogous to those realized by exposing cows to short day length during the dry period. Feeding endophyte-infected grasses during late lactation and dry period may permit better utilization of feed resources, while potentially enhancing udder health and milk production.

Technical Abstract: Ergot alkaloids in endophyte-infected grasses inhibit prolactin (PRL) secretion and may reduce milk production of cows consuming endophyte-infected grasses. We investigated the effects of consuming endophyte-infected fescue during late lactation and the dry period on mammary growth, differentiation and milk production. Twenty-five multiparous Holstein cows were randomly assigned to 3 treatment groups. Starting at 90 d prepartum, cows were fed endophyte-free fescue seed (control, CON), endophyte-free fescue seed plus 3x/wk subcutaneous injections of bromocriptine (0.11 mg/kg BW; positive control, BROMO), or endophyte-infected fescue seed (INF), as 10% of the diet. Although milk yield of groups did not differ prior to 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 lower in INF and BROMO cows than CON cows. Three weeks after the end of treatment, circulating concentrations of PRL were equivalent across groups. Although treatment 4 wk prior to dry-off initially reduced milk yield in INF and BROMO cows, milk production in the ensuing lactation was increased in BROMO and tended to increase in INF cows by approximately 10% relative to CON. Quantitative histological analysis of mammary tissue during the dry period and next lactation was used to evaluate impact of treatment on the overall secretory cell number and activity. Immunohistochemical analysis of putative mammary stem cell markers and proliferation markers were used to assess the impact of treatment on mammary growth and stem cell activity. Fescue toxicosis did not significantly impact mammary growth and development at the times evaluated. We propose that this effect is due to a sustained reduction in PRL during the dry period, analogous to increased milk yield realized by exposing cows to short photoperiod (low PRL) during the dry period. Feeding endophyte-infected grasses during late lactation and dry period may permit effective utilization of feed resources. We suggest that feeding endophyte-infected fescue may be used to reduce milk yield before dry-off to promote udder health and during the dry period to potentially increase milk yield in the next lactation.