The objective of this experiment was to determine if nutrient utilization and energy partitioning by lactating dairy cows would differ in response to dietary corn grain (CG) types [steam-flaked corn (SFC) vs. high-moisture corn (HMC)] and to test if the types of CG would interact with slow-release urea (SRU) on lactational performance and energy utilization. Eight multiparous Holstein cows (32 ± 8.2 days-in-milk) were used in a duplicated 4 × 4 Latin square with one square consisting of ruminally cannulated cows. A 2 × 2 factorial arrangement was used to test 4 dietary treatments: SFC without SRU, SFC with SRU, HMC without SRU, and HMC with SRU. The experimental diets contained 60.5% dry matter (DM) of forages, whereas 12.9% or 14.4% DM of SFC or HMC was added in the diets, respectively. The SRU was supplemented at 0.46% DM, replacing a mixture of soybean meal and canola meal in a 50:50 ratio. Feeding HMC decreased intakes of DM, crude protein, and fiber compared with SFC. Supplementation of SRU did not affect intakes of DM and nutrients, whereas it tended to increase intakes of DM or increased crude protein intake under SFC but no effect under HMC, leading to CG ×SRU interactions on DM and crude protein intakes. Neither type of CG nor SRU supplementation affected milk production except that cows fed HMC-based diets tended to decrease energy-corrected milk yield compared to those fed SFC-based diets. Utilization of HMC in the diet had a tendency to increase dairy efficiency based on milk yield over SFC utilization. Cows fed HMC diets gained more body weight (BW) than those fed SFC diets, whereas supplementing SRU tended to reduce BW gain regardless of type of CG. Cows fed HMC diets shifted more net energy into BW compared with those fed SFC diets, whereas supplementing SRU tended to decrease a portion of net energy partitioned into BW gain under both SFC and HMC diets. Dietary treatments exerted minor impacts on ruminal fermentation profiles. Feeding HMC diets decreased fecal N excretion compared with SFC diets. In addition, supplementing SRU increased fecal N excretion under SFC, but it was decreased by SRU with HMC, leading to an interaction between CG and SRU. These collective results demonstrate that feeding HMC with SRU can be a practical option in high-forage lactation diets to maintain or improve nutrient and energy utilization efficiency and minimize negative environmental impacts.

L'objectif de la présente étude est l’évaluation des effets de l'exposition gestationnelle et lactationnelle aux anguilles contaminées aux POP dont la Σ6 PCB-NDL, sur la mémoire, la capacité d’apprentissage, l’activité motrice, le comportement de résignation, le statut oxydatif et l'activité de l'acétylcholinestérase des souris de génération F1. Pour ce faire, des souris femelles ont été exposées, à partir du sixième jour de gestation (JG 6) jusqu'au jour postnatal 21 (JPN 21), par voie d'ingestion, aux anguilles contaminées contenant Σ 6 PCB-NDL. Trois doses de la Σ 6 PCB-NDL ont été choisies : 85, 216 et 400ng/kg/j en se référant à un groupe de souris témoins. Nos résultats ont montré que l'exposition gestationnelle et lactationnelle, aux anguilles contaminées, contenant la Σ 6 PCB-NDL, n’a pas affecté la capacité d’apprentissage, ni la mémoire. Cependant, le traitement, utilisé dans cette étude, pourrait causer une hyperactivité tardive, persistante et sexe dépendante qui ne touche les souris femelles de la génération F1. En outre, un effet « depresive-like » de l’exposition gestationnelle et lactationnelle des souris de génération F1 aux anguilles contaminée par les POP y inclus la Σ 6 PCB-NDL, a été relevé de façon sexe dépendante. Le comportement « depresive-like » ne touche que les souris mâles et il était persistant au fil de temps. L’étude du statut oxydatif des trois régions cérébrales (cortex préfrontal, hippocampe et cervelet), a révélé que le traitement pourrait perturber, de façon sexe dépendante, l’activité des enzymes antioxydants (Cat, SOD) au niveau du cortex préfrontal et de l’hippocampe. Les conséquences du stress oxydant, dans cette étude se sont manifestées par une augmentation du taux des protéines carbonylées au niveau du cortex préfrontal et de l’hippocampe de certains groupes de souris mâles traitées. Cependant, aucune différence significative, n’a été enregistrée, au niveau des trois régions cérébrales étudiées, dans le taux de MDA, entre les souris traitées et les souris témoins. La perturbation du statut oxydatif a été sexe dépendante, elle n’a touché que les souris mâles. L’étude de l’activité de l’acétylcholinestérase a montré que l’ingestion des souris gestantes et puis allaitantes des anguilles contaminées contenant Σ6PCB-NDL aux doses 85 et 400 ng / kg / jour était à l’origine d’une inhibition significative, par rapport au témoin de l’activité de l’acétylcholinestérase, au niveau du cortex préfrontal de leurs progéniture femelles. Alors qu’au niveau de l’hippocampe, une inhibition significative de l’activité de cette enzyme a été enregistrée chez les souris mâles traitées aux anguilles contenant Σ6PCB-NDL à la dose de 85 ng / kg / jour et chez toute la progéniture de souris femelles des groupes traitées / The objective of the present study is the evaluation of gestational and lactational exposure to contaminated eels, containing Σ6 NDL-PCBs, on learning, memory, motor activity, resignation behavior, oxidative status and acetylcholinesterase activity of the offspring mice. For this purpose female mice were orally exposed during gestational and breast feeding period (from JG6 to JPN 21), through standard diet containing contaminated eel with Σ6 NDL-PCBs or no. Three doses of Σ 6 NDL-PCBs were chosen: 85ng / kg / day, 216 ng / kg / day and 400ng / kg / day. A control group of female mice, receiving the standard diet without fish, was used. Results showed that gestational and lactational exposure to contaminated eels, containing Σ6 NDL-PCBs, did not affect the memory and learning capacities. However the early-life exposure to polluted eels containing Σ6 NDL-PCBs caused late, persistent and gender dependent neurobehavioral hyperactive effects in offspring mice that affects only offspring females. Furthermore our results suggest that the consumption of polluted fish by pregnant and lactating dams might cause neurobehavioral depression only in their male offspring, at progressive life stage. Moreover the study of oxidative status on the three brain areas (prefrontal cortex, hippocampus and cerebellum), revealed that the treatment had affected the activity of antioxidant enzymes (Cat, SOD) only in the prefrontal cortex, hippocampus of male mice. The consequences of oxidative stress in this study were revealed by an increase of protein carbonyl levels in the hippocampus and the prefrontal cortex of offspring male mice, exposed to chemically contaminated fish containing Σ6 NDL-PCBs at the dose of 85 and 216 ng / kg / day, respectively. However the treatment had no effect on the lipids. Indeed there were no significant differences in the MDA rate, in the three studied regions of the brain, between treated and control mice. Moreover, gestational and lactational exposure to contaminated eels, containing Σ6NDL-PCB at the dose of 85 and 400 ng / kg / day, had inhibited acetylcholinesterase activity, in the prefrontal cortex, only of female mice. However, in the hippocampus, the enzyme activity was inhibited of male mice, exposed to contaminated eels, containing Σ6NDL-PCB at the dose of 85 ng/ kg / day and in all the treated female offspring mice