The aim of this trial was to assess the effects of the administration ofdifferent combinations of mycotoxins in naturally contaminated maize grains ondairy heifer growth, blood measurements and puberty onset. A total of 35Friesian female heifers were randomly allotted to three experimental groups from18–21 to 42–45 weeks of age. During the 24-weekexperimental period (EP), heifers were fed the same diet, but with maize mealderived from three differently contaminated lots: very low contamination, ascontrol (C); medium–low aflatoxin-contaminated (A); and mixedaflatoxin–fumonisin contaminated (A-F). At the end of the EP, theyreturned to a common diet without contaminated maize, and they were monitoredfor an additional period of 12 weeks (post-experimental period, PEP). BW, witherheight, hip height, body length and heart girth were measured every 4 weeks fromthe beginning of EP to the end of PEP. At the same time, body condition scorewas evaluated and blood samples were taken from the jugular vein to be analysedfor haematological, serum protein and metabolic profiles. Age at puberty wasassessed by measuring weekly plasma progesterone levels from 40 to 52 weeks ofage. Body growth measurements were processed both by ANOVA of average daily gainof EP and PEP separately, and by the analysis of growth curve parameters.Haematological, serum protein and metabolic profile were evaluated using a mixedmodel, taking into account the repeated measurements in time on each animal.Heifers’ growth was delayed both in A and A-F groups during EP, asevidenced by the different linear coefficients of the BW growth curve in thethree groups. Differently contaminated diets did not affect the haematologicalprofile, so that it can be concluded that these levels of mycotoxincontamination do not determine any specific effect on haematopoiesis andimmunity in growing heifers. The main blood marker of mycotoxin chronic toxicitywas the γ-glutamyl transferase activity level inplasma, which appeared to be altered even after the removal of mycotoxins.During EP, plasma glucose was lower in the groups fed contaminated diet comparedwith C. The joint actions of an altered nutritional status and a long-lastingliver damage were probably the causes of the delay in puberty attainment in Aand, particularly, in the A-F group. The results from this trial evidenced thata chronic aflatoxin–fumonisin contamination in diets of dairy heiferscan determine an important delay in the reproductive career of theseanimals.
