Dairy cows experiencing heat stress have reduced intake and increased reliance on glucose, making feeding strategies capable of improving diet digestibility plausible for improving postrumen nutrient flow and performance. The effect of yeast on digestion and performance of lactating cows during the warm summer months of southeastern Brazil was evaluated. Cows were individually fed in tie stalls and temperature-humidity index was above 68 during 75.6% of the experiment. Twenty-eight Holstein cows (207±87 d in milk) received a standard diet for 14 d and then a treatment for 70 d, in a covariate-adjusted, randomized block design with repeated measures over time. Treatments were yeast (Saccharomyces cerevisiae) or control. Yeast was top dressed to the diet in the morning, equivalent to 25×10(10) cfu of live cells and 5×10(10) cfu of dead cells. The diet contained corn silage (37.7%), Tifton silage (7.1%), raw soybeans (4.1%), soybean meal (16.5%), finely ground corn (20.7%), and citrus pulp (11.9%). Yeast increased milk (26.7 vs. 25.4 kg/d) and solids yield (3.06 vs. 2.92 kg/d), especially lactose. Response in milk yield was consistent over time and started at d 5. The daily intake of digestible OM, total-tract digestibility of nutrients, urinary allantoin excretion, chewing pattern throughout the day, and dry matter intake did not respond to yeast. A trend was observed for increased plasma glucose with yeast (62.9 vs. 57.3mg/dL), lowered respiratory frequency (48 vs. 56 breaths/min), and increased plasma niacin content (1.31 vs. 1.22 µg/mL), though cows had similar rectal temperature. Ruminal lactate and butyrate as proportions of ruminal organic acids were reduced by yeast, but no effects on other organic acids, ruminal pH, or protozoa content were detected. Plasma urea N over 24h was increased by yeast. On d 72 to 74, citrus pulp was abruptly replaced with finely ground corn to induce acidosis. The increased load of starch increased dry matter intake between 0700 and 1300 h, jugular blood partial pressure of CO2, HCO3-, and base excess, and decreased blood pH for both treatments. The yeast treatment had a higher blood pH compared with the control, 7.34, and 7.31, respectively. Yeast supplementation improved lactation performance of dairy cows under heat stress. Improvement in lactation performance apparently involved the regulation of body homeothermia, rather than improved digestibility.

27Studies that optimize the haploid technique in the removal of maize lines are necessary. 28Between the stages that mostly requires attention and it is directly related to the success of 29 the technology is the correctly separation of induced haploids and diploids. Morphological 30 markers are commonly used but have strong influence of the environment, and laboratory 31 methods have been developed and may be more efficient. Thus, the objective was to study 32 the use of the anatomical analysis tool, through the analysis of young maize leaf for use as 33 the indirect markers in the identification of ploidys. The hybrids were crossed with the KEMS 34 haploid inducer. The seeds crossed, were selected according to the R-navajo marker and 35 submitted to two different protocols of chromosome duplication. Plants that survived to the 36 duplication protocols were acclimated in greenhouse and then transferred to the field. After 37 the self-polinization of the DH0 plants, the DH1 seeds were taken to the field, divided into 38 treatments according to the parentals and duplication protocols. At the vegetative stage V4 of 39 the plants, leaf tissue samples were collected to the evaluation of the amount of DNA and 40 identification of ploidys and anatomical analysis. The nuclear DNA review of each sample 41 was performed for the comparison in histograms of the position of G1 peak to the G1 peak of 42 the internal or external reference standard. A high accuracy came to validate an anatomical 43 tool, through the variables studied in this work, as a marker in the differentiation of ploidis in 44 maize plants, and it can be used in selection programs. The anatomy made in some letters is 45 a non-destructible technique and, together with a flow cytometry technique, can be used as 46 an indirect method in haploid cutting programs at the initial stage of the identification of 47 seedlings. 48 49 50 51 3 52