Effects of dietary cation-anion difference on ruminal metabolism and blood acid-base regulation in dairy cows receiving 2 contrasting levels of concentrate in diets.

Dietary cation-anion difference [DCAD=Na+K-Cl in mEq/kg of dry matter (DM)] increases DM intake (DMI) in cows fed diets containing rapidly degraded starch. Increased DMI of diets containing rapidly degraded starch could potentially exacerbate subacute acidosis. The objective of this study was to determine metabolic effects of increasing DCAD in low and high starch diets.

Changing dietary cation-anion difference for dairy cows fed with two contrasting levels of concentrate in diets.

High-producing dairy cows are commonly fed diets containing a high proportion of rapidly degradable starch, which can cause subacute acidosis and reduce dry matter (DM) intake. Because of the properties of nonmetabolizable cations and anions, increasing the dietary cation-anion difference (DCAD = Na + K - Cl - S in mEq/kg of DM) may prevent a drop in DM intake. To test this hypothesis, 48 Holstein cows were blocked into 2 groups of 24 and assigned to two 3 x 3 Latin squares in a split-plot design.

III. Quantitative aspects of phosphorus excretion in ruminants.

Ruminant phosphorus excretion and metabolism were studied through a database. Faecal endogenous phosphorus is the main pathway of phosphorus excretion and averages 0.85 of total faecal phosphorus.

II. Quantitative aspects of phosphorus absorption in ruminants.

Phosphorus absorption in ruminants was analysed from a database described in a previous article. For common values of ingested phosphorus (2.5-5.

I. A bibliographic database for quantitative analysis of phosphorus flow in ruminants.

The present study describes a quantitative analysis of phosphorus metabolism in ruminants. The database compiles 100 sources either published (95) or unpublished (5) involving studies on true or apparent phosphorus balances carried out before 1999. The database reports 652 distinct experimental conditions (lines) described with experimental variables (column) involving a total of 2982 animals: 414 lambs (33 references), 1078 sheep (37 references), 64 pregnant ewes (3 references), 212 lactating ewes (5 references), 528 calves (20 references), 4 maintenance cows (1 reference), 519 lactating cows (6 references), 42 kids (1 reference) and 121 lactating goats (3 references).

Lactation response and nitrogen, calcium, and phosphorus utilization of dairy goats differing by the genotype for alpha S1-casein in milk, and fed diets varying in crude protein concentration.

Twenty-four dairy goats were used in a preliminary trial to evaluate the effect of the genotype for alpha S1-casein (alpha S1-CN) in milk [homozygous variant A/A (n = 12) or F/F (n = 12)] on milk yield and composition for 2 wk from kidding. After this period, the main trial aimed at determining the effects of the genotype for alpha S1-CN in milk, the dietary crude protein concentration on milk yield and composition, and utilization of N, Ca and P. The goats within each genotype were allocated to a 3 x 3 Latin square for 14 wk with three crude protein concentrations in the total mixed ration (13.

Effects of copper supplementation on the copper status of peripartum beef cows and their calves.

The effects of copper supplementation on the copper status of 40 late-pregnant Aubrac beef cows grazing a copper-deficient pasture and later fed a marginally deficient diet were studied for five months. They were divided into four equal groups; the control group received no copper supplement, groups 1 and 2 received copper as copper sulphate at 10 and 30 mg/kg of diet dry matter (DM), respectively, for five months, and group 3 received 120 mg/kg of diet dry matter for 10 days. Plasma copper concentration and the activity of erythrocyte superoxide dismutase (eSOD) were measured at the beginning of the experiment, in the cows and calves during weeks 1 and 3 after calving, and in the calves before they were turned out to pasture at a mean (sd) age of 51 (26) days.

Utilisation of phytate phosphorus by rumen bacteria in a semi-continuous culture system (Rusitec) in lactating goats fed on different forage to concentrate ratios.

Experimental data on phytate phosphorus utilisation by ruminants are scarce. The aim of this study was to estimate the phytase activity of rumen micro-organisms when phytate phosphorus supply is high. A semi-continuous culture system fermentor (RUSITEC) was used.

Ruminal phosphorus availability from several feedstuffs measured by the nylon bag technique.

The present study was aimed at determining rumen phosphorus availability of some feedstuffs assessed with the nylon bag technique: forage (alfalfa), cereals (control-C wheat, formaldehyde treated-FT wheat, barley, corn), cereal by-products (wheat bran, wheat distillers, corn distillers) and meals (C and FT soya bean meals, rapeseed meals and sunflower meals). Rumen phosphorus availability was not uniform amongst the feedstuffs, varying from 33.1% (FT rapeseed meal) to 84.

[Minimal requirement of phosphorus for maintenance in lambs].

The purpose of the present study was to determine the minimum level of endogenous fecal loss of P in sheep receiving a P-deficient and Ca-rich diet composed of natural feedstuffs. The low fecal endogenous loss of P (15 mg/kg/d) was obtained under abnormal physiological conditions and did not correspond to the minimum requirement for maintenance.