To evaluate the effect of using urea in the diet on ovarian follicular dynamics and plasma urea and progesterone concentration, an experiment was carried out with 29 Alpine goats randomly distributed into four diets, each one containing 0%; 0.73%; 1.46% or 2.24% of urea on total dry matter. The follicular dynamics was monitored daily by ultrasonography. The estrous cycles were characterized by occurrence of two, three, four or five follicular waves. The emergence day of the first follicular wave in cycles with two waves, the length of the third wave and the maximum diameter of the largest follicle of the third wave in cycles with three waves presented a quadratic behavior according to the percentage of urea in the diets. In cycles with four waves, the urea intake did not influence the follicular dynamics. The interestrus and interovulatory periods and the luteal and follicular phases length did not differ among treatments. The plasma urea concentration did not differ among diets neither among collection weeks. Plasma progesterone concentration on the estrus day and on the 11th day after estrus presented quadratic behavior, and on the 15th day after estrus, it linearly reduced acording to the percentage of urea in the diets. The supply of urea in diets at levels up to 2.24% in dietary dry matter did not influence the dry matter intake and the urea plasma concentration. For goats, the emergence day and the length of the waves, the follicular diameter and the plasma progesterone concentration on the estrus day and in the latter stages of diestrus were altered when there was supply of urea in the diet.

A suplementação com levedura pode melhorar a eficiência digestiva de ruminantes. Entretanto, a resposta depende da cepa de levedura e da composição da dieta. Silagem de milho e polpa cítrica são fontes frequentes de carboidratos para vacas leiteiras no Sudeste do Brasil. Avaliou-se a suplementação de vacas leiteiras alimentadas com dieta baseada em silagem de milho e polpa cítrica com Saccharomyces cerevisiae cepa CNCM I1077 (Lallemand SAS, Toulouse, França). Vinte vacas Holandesas multíparas em meio de lactação foram alocadas a uma seqüência de dois tratamentos em delineamento de reversão simples. Os tratamentos foram: 10 g de levedura viva em farinha de ostra para fornecer um mínimo diário de 1 × 10(10) ufc por vaca ou farinha de ostra fornecidos sobre a refeição matinal. A dieta continha (% da matéria seca): 16,8% de proteína bruta, 30,9% de fibra em detergente neutro, 43,9% de silagem de milho, 2% de feno de tifton, 14,4% de milho floculado, 16,9% de polpa cítrica e 21,7% de farelo de soja. A suplementação com levedura aumentou as produções diárias de leite (29,4 vs. 28,5 kg, p = 0,11), proteína (0,939 vs. 0,908 kg, p = 0,05) e lactose (1,264 vs. 1,241 kg, p = 0,06), e não teve efeito sobre a gordura do leite (p = 0,53). O consumo diário de matéria seca foi 21,4 kg com levedura e 20,7 no controle (p = 0,11). A digestibilidade aparente da fibra em detergente neutro no trato digestivo total foi 48,1% com levedura e 43,2% para o controle (p = 0,08). Houve tendência de aumento no consumo de matéria orgânica digestível com a suplementação de levedura (p = 0,07). A resposta positiva em secreção de proteína do leite à suplementação com levedura parece ter sido resultado do aumento na digestibilidade da fibra, mas o mecanismo para a resposta não pôde ser elucidado.

Dietary yeast supplementation may improve the digestive efficiency of ruminants, but responses depend on the yeast strain and the diet composition. Corn silage and citrus pulp are usual carbohydrate sources for dairy cows in southeast Brazil. This study evaluated the supplementation of dairy cows fedding on corn silage-citrus pulp-based diets with Saccharomyces cerevisiae CNCM I-1077 (Lallemand SAS, Toulouse, France). Twenty multiparous, midlactation Holstein cows were assigned to two treatments in crossover design. Treatments were: live yeast on oyster meal capable of supplying a daily minimum of 1 × 10(10) CFU per cow or oyster meal top-dressed at 10 g to the morning meal. Diet contained (% of dry matter): 16.8% crude protein, 30.9% neutral detergent fiber, 43.9% corn silage, 2% tifton hay, 14.4% steam flaked corn, 16.9% citrus pulp and 21.7% soybean meal. Yeast supplementation increased daily yields of milk (29.4 vs. 28.5 kg, p = 0.11), protein (0.939 vs. 0.908 kg, p = 0.05), and lactose (1.294 vs. 1.241 kg, p = 0.06), but did not affect milk fat contents (p = 0.59). Daily dry matter intake was 21.4 with yeast and 20.7 kg for the control (p = 0.11). Total tract apparent digestibility of the neutral detergent fiber was 48.1% with yeast and 43.2% for the control (p = 0.08). There was a trend for increased intake of digestible organic matter with yeast supplementation (p = 0.07). The positive milk protein yield response to yeast supplementation may have resulted from the increased fiber digestibility, but the response mechanism could not be elucidated.