RESUMO: A urolitíase é uma desordem comum na clínica veterinária, considerada como uma das maiores causas de morbidade. Esta desordem está intimamente associada ao pH urinário sendo que a nutrição desempenha papel fundamental no controle dessa doença, pois através da manipulação dietética é possível modificar o pH urinário. O enxofre é considerado um macroelemento com forte influência no equilíbrio ácido-básico e pode ser crucial para controlar o pH urinário em gatos. O objetivo deste estudo foi avaliar os efeitos da adição de diferentes fontes de enxofre (S) na dieta de gatos nos parâmetros urinários e no equilíbrio ácido-básico destes animais. 42 gatos adultos saudáveis foram divididos em 3 grupos e cada grupo de 14 gatos recebeu 7 dietas em um delineamento de blocos ao acaso. O sulfato de cálcio (CaSO4), a DL-metionina (DLM) e a metionina hidróxi-análoga (MHA) foram adicionados a uma dieta controle em dois níveis (1,28g S/kg e 2,56g S/kg) para formular outras 6 dietas experimentais. O equilíbrio ácido-básico foi avaliado por hemogasometria em amostras de sangue venoso. O DLM no teor mais alto e MHA diferiram da dieta controle em relação ao pH urinário (P<0,05). O sulfato de cálcio, embora não tenha diferido da dieta controle, demonstrou alterar o pH urinário apesar do seu equilíbrio eletrolítico nulo. Aparentemente, o efeito alcalinizante do cálcio não foi suficiente para anular a acidificação da urina pelo sulfato. Os tratamentos não apresentaram alteração do equilíbrio ácido-básico dos animais e não afetaram o consumo das dietas experimentais.

ABSTRACT: Urolithiasis is a common disorder in the veterinary clinic and is considered as one of the most frequently cause of morbidity. This disorder is closely associated with urinary pH and nutrition plays a key role in the control of this disease, because through dietary manipulation it is possible to modify the urinary pH. Sulfur is considered macroelement with a strong influence on the acid-base status and may be crucial to control urinary pH in cats. The purpose of this study was to evaluate the effects of addition of different sources of sulfur (S) in the diet of cats on the urinary parameters and acid-base balance. Forty-two healthy adult cats were divided into 3 groups, and each group of 14 cats received 7 diets in a complete randomized block design. Calcium sulfate (CaSO4), DL-methionine (DLM) and methionine hydroxy analog (MHA) were added to a control diet in two levels (1.28g S/kg and 2.56g S/kg) to formulate 6 other experimental diets. The acid-base balance was evaluated by hemogasometry in samples of venous blood. The DLM at the highest level and MHA differed of the control diet in relation to urinary pH (P<0.05). Calcium sulfate; although, not differentiated from the control diet, has been shown to alter urinary pH despite its zero electrolyte balance. Apparently, the alkalizing effect of calcium was not sufficient to avoid sulfate acidification of the urine. Treatments showed no alteration of the acid-base balance of the animals and no affect the consumption of the diets.

ABSTRACT The objective of this study was to evaluate the effects of polymer coated slow-release urea (SRU) in high-forage diets of beef steers on nutrient intake and digestibility, ruminal fermentation, microbial protein synthesis, and energy balance. Eight 24-mo-old rumen-fistulated castrated Nellore steers (average body weight = 418.0±40.0 kg) were used in a replicated 4 × 4 Latin square design. Animals were randomly distributed to receive one of the following diets: no urea inclusion; 1.0% inclusion of feed grade urea in the diet (dry matter [DM] basis); 1.0% inclusion of slow-release urea 1 in the diet (DM basis); and 1.0% inclusion of slow-release urea 2 in the diet (DM basis). Slow-release urea 2 had a similar composition to that of slow-release urea 1 and differed in that it contained 2.95% sulfur. A high-forage diet was provided (75% of total DM) and corn silage was used as the forage source. Diets with urea had increased crude protein (CP) intake, and CP and total digestible nutrients total tract digestion. Urea sources increased ruminal concentrations of ammonia nitrogen and acetate, and decreased butyrate concentrations. The polymer coated urea did not alter ruminal fermentation when compared with feed grade urea. Diets did not affect the energy balance of steers. Feed grade urea presented greater microbial protein synthesis than polymer coated slow-release urea. The partial replacement of soybean meal by 1% slow-release urea in a diet with 75% forage does not improve ruminal fermentation and microbial protein synthesis, and shows similar results as feeding feed grade urea to beef steers.

ABSTRACTThe objective of this experiment was to quantify the effects of feeding polymer-coated slow-release urea on nutrient intake and total tract digestion, milk yield and composition, nutrient balances, ruminal fermentation, microbial protein synthesis, and blood parameters in dairy cows. Sixteen Holstein cows (580±20 kg of live weight (mean ± standard deviation); 90 to 180 days in milk (DIM); and 28 kg/d of average milk yield) were used in a replicated 4 × 4 Latin square experimental design. The animals were assigned to each square according to milk yield and DIM. The animals were randomly allocated to receive one of the following experimental diets: 1) control (without urea addition); urea (addition of 1% on the diet DM basis); polymer-coated slow release urea 1 (addition of 1% on the diet DM basis); and polymer-coated slow release urea 2 (addition of 1% on the diet DM basis). All diets contained corn silage as forage source and a 50:50 forage:concentrate ratio. Milk and protein yield, production of volatile fatty acids, and propionate decreased when cows were fed diets containing urea. Addition of urea decreased nitrogen efficiency and nitrogen excreted in the feces. However, the diets did not change the cows' microbial protein synthesis, ruminal pH, or ammonia concentration. The inclusion of urea in cow diets decreases milk and protein yield due to lower production of volatile fatty acids. No advantages are observed with supplementation of polymer-coated slow-release urea when compared with feed-grade urea.