Experiments on the nutrition of the dairy heifer: VII. Observations on the effect of the energy intake on the utilization of protein in growth and in lactation

The effect of altering the level of protein intake on urea excretion in ewes was assessed in two separate experiments.In Expt 1, 14 pregnant (during the last 20 days of gestation) and 10 non-pregnant ewes were each offered a different level of digested N intake in the range 5-25 g/day. At all levels of protein intake urea N excretion was lower in pregnant than in nonpregnant ewes.In Expt 2, 21 pregnant ewe lambs were each offered one of three diets supplying mean intakes of 83 (Tl), 113 (T2) or 147 (T3) g crude protein/day. During the last 100 days of gestation the mean levels of urea N excretion were 6-9, 11-0 and 15-2 g/day for T1, T 2 and T 3, respectively. The corresponding values for urinary N excretion were 9-3, 13-8 and 18-2 g/day. At all levels of protein intake urea N excretion was lower just prior to parturition than 95 days prepartum; the difference was correlated with lamb birth weight and maternal body-weight change.A notable feature of both experiments was the low level of urea N excretion by the pregnant ewes in late gestation, at low protein intakes. It would appear that when energy intake is adequate the decrease in urea N excretion associated with pregnancy is a direct result of an increased N requirement for maternal and/or foetal growth.

Section: Discussionsupporting

confidence: 71%

Observations on the effect of protein intake and stage of gestation on the proportion of urinary nitrogen excreted as urea in sheep

Robinson¹,

Scott²,

Fraser³

1973

“…Although dietary protein content is not normally considered as a factor likely to influence milk fat content, Sparrow et al (1973) and Grieve et al (1974) have recorded a response to increasing dietary protein. Feeding trials in mid-lactation usually do not show this response (Broster et al 1969;Gordon, 1977). In this experiment dietary protein content had a marked effect on milk fat content in early lactation, but not in mid-lactation, when the range of whole-ration CP contents was considerably narrower than in early lactation and the concentrate to forage ratio had been reduced.…”

Section: -86mentioning

confidence: 61%

Protein studies on maize silage as a basal ration for dairy cows

Phipps¹,

Weller²,

Smith³

et al. 1981

Self Cite

In Expt 1 40 lactating British Friesians, 20 cows and 20 heifers, were used to study the effect of crude protein (CP) content of the whole ration on milk yield, milk composition and live-weight change when maize silage was fed as the basal ration. There were four treatments with five cows and five heifers on each. During lactation weeks 4-12 the cows on treatments 1, 2, 3 and 4 all received 7 kg maize silage dry matter (D.M.) plus 8 kg D.M./day of a concentrate containing either 14, 18, 22 or 24% CP, respectively; heifers received 1 kg/day less of both silage and concentrate. This produced whole-ration CP contents of 11-7, 13-9, 16-0 and 17-1%. In the subsequent lactation weeks 13-20 silage feeding was increased to 9 kg D.M./cow/day and concentrate feeding decreased to 5 kg D.M./cow/day. Heifers again received 1 kg/day less of both silage and concentrate. This decreased whole-ration CP contents to 10-5, 11-7, 12-9 and 13-4%.During lactation weeks 4-12 and 13-20, with the exception of milk fat content in weeks 13-20, there were significant linear effects of whole-ration CP content on milk yield, milk fat, protein, lactose and total solids. There were no significant curvilinear relationships. Thus, despite the fact that the highest numerical values were generally recorded for the animals on treatment 3, the results indicate that a whole-ration CP content of at least 17-1 and 13-4% are required in early and mid-lactation respectively.In Expt 2 the loss of D.M., acid-detergent fibre and nitrogen from maize silage suspended in nylon bags in the rumen was measured. Compared with feeding either a low or high protein supplement, losses were greater for silage fed alone. If it is accepted that nitrogen loss can be approximated to protein degradability, then the value for maize silage was between 0-6 and 0-7. Using the same technique in Expt 3, comparable nitrogen losses for fish meal, decorticated groundnut meal and soya-bean meal were 0-3, 0-9 and 0-9, respectively, after 24 h incubation.

“…Urine passed through a perforated metal grid and was collected in glacial acetic acid. Subsampling and analysis followed the routine described by Broster et al (1969).…”

Section: Methodsmentioning

confidence: 99%

Experiments on the nutrition of the dairy heifer

Broster¹,

Smith²,

Broster³

et al. 1978

Self Cite

SummaryEight experiments, comprising four randomized-block feeding trials each with 20–45 animals and four changeover-design nitrogen (N) balance trials each with 6–10 animals, were used to study the effect of the addition of formaldehyde to fishmeal and to casein, of severe heating of fishmeal, and of tannin treatment of a mixture of vegetable protein-rich foods on the utilization of N for growth. Added in moderate amounts to rations demonstrated within the experiments to be deficient in N, quantities, but not the preparations, of N in the diet were critical to growth save at very low N intakes when the untreated foodstuffs were used more efficiently. Additional energy given in isonitrogenous rations increased growth, reducing N losses in the urine.