The effect on the performance of dairy cattle of plant protein concentration and of urea or urea-phosphate supplementation in the diet

Abstract

Sixty Israeli-Friesian cows were allocated, after calving, to five treatment groups of 12 cows per group according to the concentration and source of crude protein (CP) in the concentrate. Three groups received all their protein from plant sources: a basal control group (BP) was given concentrate containing 92 g CP per kg dry matter (DM), a medium-protein group (MP) was given a diet with soya-bean meal (SBM) added to give a CP concentration of 143 g/kg DM, and a high-protein group (HP) was given a diet with SBM added to give a concentration of 180 g/kg DM. Two groups were given the basal concentrate supplemented with urea (MU) or urea phosphate (MUP) up to approximately the same CP level as the MP group. The only roughage used was vetch-oats hay at a level of 350 g/kg total DM intake. The cows were given the experimental diets ad libitum throughout lactation.No difference was found between treatments in DM intake (kg/day), mean milk and fat-corrected milk (FCM; 40 g fat per kg) yields (kg/day), milk protein concentration, days from calving to conception or services per conception, during the entire lactation period. However, FCM yields during 60 days after calving were significantly higher for cows given the CP-supplemented diets than for the BP group. The FCM yield of the cows given the HP concentrate was higher than for those given the other concentrate mixtures only during the first 15 days after calving. Milk fat concentration was higher in cows given the BP and HP concentrates than in those given the MP ration, but only a trend in this respect was observed when part of the plant protein was replaced by urea or urea phosphate.The rate of body-weight loss after calving tended to increase with increase in amount of plant protein in the diet but was highest for the cows given the diets supplemented with non-protein nitrogen. Later in lactation, the body-weights of cows given the MP, HP and MUP diets increased immediately after they reached their lowest weight whilst cows given the BP and MU diets started gaining weight 165 and 120 days after calving, respectively.Rumen ammonia-N and blood urea-N concentrations (mg/1) for treatments BP, MP, HP, MU and MUP were: 56 and 101; 120 and 226; 143 and 269; 191 and 227; and 179 and 212, respectively. The relationship between rumen ammonia concentrations, blood urea concentrations and CP utilization for the different treatments is discussed. Supplying urea as urea phosphate tended to improve performance by an increase in annual milk and milk protein yields as well as in live-weight gain.

The effect of undegradable crude protein supplementation on milk production and composition and reproduction of early-lactating cows

“…Data presented in the present study confirm that dietary CP concentration could be raised without affecting blood urea level ( Table 5). Provided that the dietary ratio of EDOM:EDCP is not altered in the HP ration as compared with the lower CP ration, a maximal capture of soluble ammonia-N in rumen fluids and minimal escape of it into portal blood might occur (Bruckental et al, 1986). Under such conditions, when dietary CP is elevated by the addition of undegradable protein only, no reduction in fertility is expected.…”

“…It has been proven in many experiments that during the first period after calving, cows respond to additional CP by increasing milk yield (Roffler et al, 1978;Bruckental et al, 1986Bruckental et al, , 1989. According to the NRC (1989), it is recommended to feed cows during the first 3 weeks after calving a ration containing 19% CP.…”

Concentrações de nitrogênio na dieta, no sangue e no leite de vacas lactantes no período pós-parto

“…Em seguida, as amostras de leite foram adicionadas de cinco gotas de ácido acético e novamente centrifugadas para retirada da proteína, dando origem ao lactosoro isento de proteínas e de gordura. Neste material, estimou-se a concentração de NUL, utilizando-se o kit Sigma (urea nitrogen procedure), Sigma Diagnósticos, St. Louis, MO, conforme recomendado por Roseler et al (1993), Baker et al (1995) e Butler et al (1996). As pesagens foram feitas semanalmente, sempre pela manhã, após jejum pré-vio de água e alimentos por 10 horas.…”

“…Bruckental et al (1986) registraram incremento na produção de leite, apenas nos primeiros 60 dias pós-parto, à medida que aumentaram a quantidade de proteína da dieta, sugerindo que a produção obtida no início da lactação é mais sensível ao efeito da PB. Melhores produções resultantes de valores elevados de proteína dietética poderiam ocorrer pela disponibilidade de aminoácidos para síntese de proteína do leite, pela disponibilidade de energia por deaminação de aminoácidos ou por fatores como maior eficiência de utilização dos nutrientes absorvidos e incremento na ingestão de matéria seca (Macleod et al, 1984;Oldham, 1984).…”

“…Reduções nas taxas de fertilidade em vacas leiteiras recebendo excesso de proteína na dieta tem sido associadas a concentrações de NUP superiores a 19 mg/dL Butler et al, 1996).…”