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  • Cambridge University Press  (4)
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  • 1
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    Response of lactating goats to low phosphorus intake 1. Milk yield and faecal excretion of P and Ca (1988)
    Cambridge University Press
    Details
    Publication Date: 1988-10-01
    Description: SummaryIn weeks 1–6 of lactation, 11 goats were fed diets adequate in phosphorus content, supplying a basal intake of 2·8 g P/day plus 1·4 g P/kg milk produced. In group 1 (three goats), this scheme was continued until week 16. In group 2 (four goats), P supply was changed from an adequate one to a reduced amount by restricting the variable intake to 1·0 g P/kg milk during weeks 7–16 and the basal intake to 0·8 g P/day during weeks 12–16. In group 3 (four goats), P deficiency was caused during weeks 7–11 by a basal intake of 0·8 g P/day plus only 0·4 g P/kg milk. During weeks 12–16 these goats received the same supply of P provided in weeks 1–6.Milk yield was depressed in group 3, but not in group 2. Composition of milk was not affected by P intake in either group. Digestibility of organic matter was reduced from 0·73 to 0·64 by P deficiency treatment. Reduction of faecal P excretion in group 2 appeared to enable P homoeostasis even at the reduced level of P intake. The amounts of P and Ca secreted in milk during P deficiency in group 3 clearly exceeded the corresponding net absorptions. During this period, daily faecal P excretion was reduced to 17 mg/kg live weight. P concentrations in blood plasma, saliva and particle-free rumen fluid were also drastically reduced. Faecal excretion of P increased after the animals returned to the diet supplying adequate P. The increase occurred before the pre-depletion P status had been restored.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 2
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    Dietary phosphorus depletion in sheep: effects on plasma inorganic phosphorus, calcium, l,25-(OH)2-Vit.D3 and alkaline phosphatase and on gastrointestinal P and Ga balances (1985)
    Cambridge University Press
    Details
    Publication Date: 1985-12-01
    Description: SUMMARYExperiments were carried out to study the effects of dietary P depletion on plasma concentrations of inorganic P (P1), calcium, 1,25-(OH)2-Vit.D3 and alkaline phosphatase, and to investigate the effects of P depletion, in comparison with P repletion, on intestinal flow and net disappearance of Ca and P in sheep. The animals were adapted to an experimental diet of pellets and chopped straw providing between 0·91 and 1·04 g P/day for depletion. They were repleted by single infusions of phosphate into the duodenum raising total P supply to about 4·1 g/day. During P depletion plasma P1, concentrations decreased significantly whereas those of Ca increased. The development of hypercalcaemia is discussed with respect to intestinal absorption and bone accretion and resorption. Plasma 1,25-(OH)2-Vit.D3 and alkaline phosphatase were not affected by P depletion.In P depletion the flow through the gastrointestinal tract of total P contained in the digesta and faecal P excretion were significantly reduced and the P balance was slightly negative. Calcium net absorption from the gut was also reduced. Daily flow of total P and P1, contained in the particle-free intestinal fluid was markedly lower in P depletion as compared with P repletion. The percentage of net disappearance from the small intestines of total P and P1, in the particle-free fluid was 57 and 70 % in the depleted state and 79 and 93% in the repleted state.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 3
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    Response of lactating goats to low phosphorus intake 2. Nitrogen transfer from rumen ammonia to rumen microbes and proportion of milk protein derived from microbial amino acids (1988)
    Cambridge University Press
    Details
    Publication Date: 1988-10-01
    Description: SummaryFive rumen-cannulated dairy goats were fed diets supplying 2·8 g P/day plus 1·4 g P/kg milk (adequate P) for weeks 1–6 of lactation. Two goats then continued to receive this adequate P supply while three goats were fed deficient diets supplying only 0·8 g P/day plus 0·4 g P/kg milk. Solutions containing CrEDTA and (15NH4)2SO4 were infused into the rumen continuously for 96 h during weeks 5–6 and 11–12, respectively. At intervals following the intraruminal infusion, 15N enrichments of rumen ammonia-N, rumen bacteria-N and milk protein-N were determined. Cr concentration was measured in particle-free rumen fluid.P deficiency did not significantly affect rumen fluid kinetics. It caused a significant increase in pH and reduced the size of the rumen ammonia pool and its outflow rate. Digestibility of organic matter as well as efficiency of microbial protein synthesis were decreased significantly and thus net microbial yield was reduced from 34·1 to 13·7 g N/day. The transfer of N of microbial origin to milk protein decreased from 5·3 to 2·7 g/day, whereas secretion of N in milk protein not originating from rumen microbes remained unchanged at 5·6–5·8 g/day.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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  • 4
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    Flow of thiamin to the duodenum in dairy cows fed different rations (1981)
    Cambridge University Press
    Details
    Publication Date: 1981-06-01
    Description: SUMMARYFour lactating Friesian cows with cannulae in the rumen and in the proximal duodenum were subjected to each of four different dietary treatments. Treatments differed with respect to concentration of crude protein, supply of urea nitrogen and frequency of feeding. The rations used consisted of hay, maize silage and concentrates and were offered to the animals according to milk yield.During the last 5 days of each experimental period (5 weeks), ingesta flow at the proximal duodenum was estimated by Cr-EDTA. Samples were taken from the duodenum at 2 h intervals and were analysed for thiamin, total nitrogen and microbial nitrogen. Labelling of microbial N was achieved by continuous infusion of 16N-urea into the rumen.With treatment 2 (26% less N than with treatment 1) thiamin net synthesis in the forestomachs and total thiamin entering the duodenum were significantly reduced whereas treatment 3 (substitution of 26% plant N by urea-N) and treatment 4 (six times instead of twice feeding daily) had no effect on synthesis and flow of thiamin to the small intestines. There were significant linear regressions between flow of microbial N and flow of thiamin to the duodenum and between organic matter digested and flow of thiamin.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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