RESUMO: Este estudo teve como objetivo avaliar a relação gordura:proteína (RGP) no primeiro controle leiteiro no pós-parto de vacas no estado do Paraná. Dados de 257.847 controles de 114.162 vacas leiteiras, realizados no primeiro controle mensal após o parto foram submetidos à análise estatística após edição dos dados. Os procedimentos MIXED, CORR e STEPWISE do programa estatístico SAS 9.4 foram utilizados. A fim de validar a RGP, um rebanho com monitoramento regular de β-hidroxibutirato (BHB) no sangue foi utilizado para estimar a correlação com RGP. Observou-se uma correlação forte e positiva entre a RGP e teor de gordura no leite (r = 0,85; P < 0,01) e uma correlação fraca e negativa entre a RGP e o teor de proteína (r = -0,23; P < 0,01). A equação de regressão que melhor se ajusta à RGP foi 1,1806 + 0,3304*%G - 0,3877*%P (R2 = 0,98), na qual a variável com maior influência foi a porcentagem de gordura (R2 = 0,72). Animais de 4ª e 5ª lactações ou mais, apresentaram maior (P < 0,01) RGP, seguidos dos animais de terceira, primeira e segunda lactações, com menores RGP. Vacas da raça Jersey apresentaram maior (P < 0,01) RGP que vacas da raça Holandesa e Pardo-Suíça. Animais com duas ordenhas diárias apresentaram maior (P < 0,01) RGP que os animais ordenhados três vezes ao dia. Observaram-se correlações positivas, mas de pequena magnitude, entre a RGP do leite e BHB no sangue no quarto, sétimo e 12 dias pós-parto (0,07, 0,13 e 0,14; respectivamente). Concluindo, o teor de gordura é o fator que mais impacta as variações da RGP do leite, mas a RGP tem valor limitado na avaliação da incidência de hipercetonemia no período de transição.

ABSTRACT: This study evaluated milk fat to protein ratio (FPR) in the first test-day after calving of dairy cows in Paraná State. Data from 257,847 first monthly test-days after calving of 114,162 cows were submitted to analysis after the data edition. Procedures MIXED, CORR and STEPWISE from SAS were used in the data analysis. In order to validate FPR, a herd with regular postpartum monitoring of blood β-hydroxybutyrate (BHB) was used to estimate the correlation with FPR. There was a strong positive correlation between FPR and fat content (r = 0.85; P < 0.01) and a weak negative correlation between FPR and protein content (r = - 0.23; P < 0.01). The regression equation that best fitted FPR was 1.1806 + 0.3304*%F - 0.3877*%P (R2 = 0.98), where the variable with the greatest influence was milk fat content (partial R2 = 0.72). Animals of 4th and 5th or more lactations had higher (P < 0.01) FPR, followed by animals of third, first, and second lactations. Jersey cows had higher (P < 0.01) FPR than Holsteins and Brown Swiss animals. Cows milked twice daily had higher (P < 0.01) FPR than animals milked three times daily. There were small positive correlations between milk FPR and blood BHB on days 4, 7 and 12 after calving (0.07, 0.13, and 0.14, respectively). In conclusion, milk fat content was reported to be the most important variable affecting FPR changes, but the milk FPR has limited value to evaluate hyperketonemia incidence during the transition period.

ABSTRACT We evaluated the association of monthly milk urea N (MUN) concentrations before conception and days open in high-producing dairy cows from commercial herds in Southern Brazil. Other herd traits were also investigated regarding their relationship with days open. A database containing 16,569 monthly test-day records (obtained from 3,926 lactations of 2,145 cows) for productive, reproductive, and milk quality data was assembled from three different herds. Maximum MUN before conception was divided into quartiles as follows: ≤15.5 mg/dL (1), from 15.6 mg/dL to 18.0 mg/dL (2), from 18.1 to 20.5 mg/dL (3), and >20.5 mg/dL (4). When cows calved in spring and winter, days open averaged (mean±SE) 171.2±2.71 and 155.4±2.31, corresponding to an increase in 12 and 2%, respectively, related to cows that calved in summer (152.7±2.44). When cows calved in fall, a 12% reduction in days open (135.5±1.79) compared with cows that calved in summer was observed. The estimated regression coefficients showed that multiparous cows are expected to have an increase of 12 and 6% in days open when compared with primiparous and secondiparous cows, respectively. Days open were positively associated with the highest MUN value obtained until conception. Cows in the highest quartile of maximum MUN (>20.5 mg/dL) had more days open (184.6±2.93) than cows in quartiles 1, 2, and 3 (123.7±2.12, 150.2±2.16, and 160.5±2.29, respectively), which represents reductions of 40, 21, and 14%, respectively. These results suggest that a maximum MUN concentration before conception higher than 15.5 mg/dL may negatively impact the fertility of high-producing dairy cows.

The present study was conducted to determine the relationship between milk urea nitrogen (MUN) and milk yield, fat and protein contents, breed and season effects, parity and days in milk in dairy cows from Paraná State, Brazil. A total of 127,428 test-days from 16,013 dairy cows belonging to 96 herds enrolled in an official milk recording program were analyzed. Multivariate mixed model methodology was used to determine the relationship between MUN and the fixed effects and the covariable milk production. Milk urea nitrogen averaged 14.45±4.60 mg/dL. Positive and intermediate association between MUN and milk yield (r = 0.34) were found. Holstein cows showed lower MUN adjusted means than crossbred, Jersey, and Brown Swiss cows: 14.18 vs. 15.49, 16.12, and 17.62 mg/dL, respectively. First-lactation cows showed higher MUN values than second-lactation and older cows: 16.16 vs. 15.95, and 15.45 mg/dL, respectively. MUN test-days collected during the winter were higher than those collected in the other seasons. The effects of the lactation stage on MUN were significant, with the highest MUN values observed in the sixth month of lactation. High-producing dairy cows showed higher milk urea concentrations but several environmental factors may contribute to reduce this important parameter of diet utilization efficiency.

The effects of inactive dry yeast (Saccharomyces cerevisiae) from sugar cane were studied in 18 primiparus Saanen dairy goats (51.07±1.43) on dry matter intake and digestibility, milk production and quality. Animals were distributed in a completely randomized design during 90 days (from day 60 of milking). Diets were composed of soybean meal; soybean meal + dry yeast; or dry yeast, as protein sources, and ground corn, mineral supplement and corn silage (40%). Animals fed the dry yeast diet showed lower intake of dry matter (DM), organic matter (OM), crude protein, ether extract and neutral detergent fiber. Diets did not influence milk yield; however the milk production efficiency (kg of milk produced/kg of crude protein ingested) was better in goats fed the dry yeast diet. Acidity, somatic cell counts and milk urea nitrogen values were not affected by treatments. Animals fed the soybean + dry yeast diet had higher fat and total solids than those fed the dry yeast diet. The digestibility of DM, OM and total carbohydrate was lower for soybean only and soybean + dry yeast diets. Total digestible nutrients were higher for dry yeast and soy bean diets than soybean + dry yeast diet. Dry yeast from sugar cane is a good alternative protein source for feeding lactating dairy goats and can be recommended because it maintains the production performance.

Avaliaram-se os efeitos de fazendas, ordem de parto (OP) e mês de parição sobre a produção de leite (PL), porcentagem de gordura, de proteína, contagem de células somáticas (CCS) e nitrogênio uréico no leite (NUL) de quatro fazendas leiteiras especializadas, totalizando 120 vacas em lactação. Estudaram-se, também, os efeitos do NUL sobre a taxa de gestação (TG) e taxa de inseminação (TIA) no início da lactação. Os parâmetros produtivos e de qualidade do leite foram semelhantes entre fazendas e não sofreram influência do mês de parição. A Fazenda D apresentou a maior taxa de NUL. A OP não influenciou a NUL, % de gordura, % de proteína e CCS. Os animais com NUL entre 10,1 - 13,0 mg/dL apresentaram as maiores TIA e TG, tanto nas fases de 55 - 70 dias como após 70 dias pós-parto. Conclui-se que o NUL é um parâmetro útil para monitorar o estado nutricional e reprodutivo de vacas leiteiras.

The effects of farm, parity (PO) and month of parturition on milk production, percentage of fat and protein, somatic cell count (SCC), and milk urea nitrogen (MUN) concentration were assessed on four specialized dairy farms using 120 cows. Also, the effects of MUN on gestation rate (GR) and artificial insemination rate (AIR) in early lactation were studied. The parameters of production and milk quality were similar among farms and were not influenced by the month of parturition. Farm D presented the highest MUN concentration. Concentration of MUN, percentages of fat and protein and SCC were not influenced by PO. Cows with a value of MUN between 10.1 and 13.0 mg/dL had the highest AIR and GR between days 55 and 70 postpartum and after 70 days in milk. These data suggested that MUN concentration was a useful parameter to predict the nutritional and reproductive stages of dairy cows.

O objetivo neste estudo foi avaliar a curva de lactação e a qualidade do leite de cabras Saanen recebendo rações com diferentes relações volumoso:concentrado. Foram utilizadas 20 cabras (59,59 kg ± 6,97) em lactação, distribuídas em delineamento inteiramente casualizado. Os tratamentos consistiram de cinco relações volumoso:concentrado nas rações (40:60, 50:50, 60:40, 70:30 e 80:20), correspondentes a 2,95; 2,83; 2,70; 2,58 e 2,46 Mcal de EM/kg MS. Os animais permaneceram alojados, durante 152 dias, em baias individuais com controle diário da ração ingerida e da produção de leite. Os tratamentos não influenciaram o peso vivo (kg) das cabras. A ingestão de matéria seca (kg/dia) variou ao longo do ciclo produtivo. A produção de leite foi influenciada pelos tratamentos, de modo que a ração com maior concentração energética proporcionou maior produção de leite. Não foram verificadas diferenças entre os tratamentos para os constituintes do leite, a produção inicial, a taxa de acréscimo de produção até o pico de lactação e a taxa de declínio de produção após o pico. No entanto, foi observado efeito linear negativo para o dia de produção no pico e a produção no pico. A relação volumoso:concentrado com maior concentração energética melhora o desempenho produtivo dos animais, sem alterar a qualidade do leite.

The objective of this study was to evaluate the lactation curve and milk quality of Saanen goats receiving diets with different forage:concentrate ratios. Twenty goats averaging 59.59 ± 6.97 kg of body weight were assigned to a completely randomized design. The following forage:concentrate ratios were used: 40:60, 50:50, 60:40, 70:30, or 80:20 and provided 2.95, 2.83, 2.70, 2.58, or 2.46 Mcal ME/kg DM, respectively. Animals were confined during 152 days in individual stalls with daily measurements of intake and milk yield. Body weight of goats fed increasing levels of forage did not change significantly in this trial but the opposite was observed for DM intake (kg/day) with the progress of lactation. Milk yield also was affected by treatments; in fact, milk production was highest in the diet with the greatest energy content. However, different forage:concentrate ratios did not affect milk components, initial milk yield, incremental production rate until lactation peak, and decline production rate after lactation peak. Conversely, day that goats reached peak production and production at peak were both reduced linearly when forage was increased in the diet. The diet with the greatest forage:concentrate ratio and energy level improved animal production with no compromise of milk quality.