Effect of dietary calcium level on plasma proteins and calcium flux occurring during a 24 h ovulatory cycle

An experiment was carried out to determine whether feeding different calcium levels from the onset of production has an effect on medullary bone reserves, plasma proteins and ultimately shell formation. A total of 80 Single Comb White Leghorn hens photostimulated at 17 wk of age were fed a 2.5% Ca diet until the appearance of the first egg. Thereafter diets providing 2.5, 3.0, 3.5, 4.0, or 4.5% Ca were fed to groups of 16 hens. At 6, 12, 18, or 24 h post-ovrposition, blood was collected from four hens per treatment, which were then euthanized and developing shells and bones sampled. As dietary Ca increased, plasma Ca, protein, and protein-bound phosphorus concentrations also increased (P < 0.05). Dietary Ca level had no effect (P > 0.05) on the % Ca or total Ca content of bone ends or medullary bone. As dietary Ca concentration increased, both shell ash and shell Ca increased (P < 0.05). Regardless of dietary Ca, shell secretion was most rapid during 12–18 h of the ovulatory cycle (postoviposition). Key words: Calcium, medullary bone, shell calcification, plasma proteins

COMPARISON OF BARLEY GROWTH IN NATURALLY AND ARTIFICIALLY SALINIZED SOILS

An experiment was conducted under controlled conditions to compare the growth of barley in naturally and artificially salinized soils. In two Chernozem soils, a Whitney clay loam and a Cavendish sandy loam, the decline in barley yield per unit increase in salinity was the same in naturally and artificially salinized treatments. These findings suggest that artificially salinized soils accurately simulate the effects of naturally saline soils in their effect on barley growth. The results further substantiate previous findings that growth response to salinity appears to be related to the availability of calcium in the soil. Key words: Calcium, salinity, Chernozem

CALCIUM SOAPS OF FATTY ACIDS WITH VARYING UNSATURATION AS FAT SUPPLEMENTS FOR LACTATING COWS

Calcium salts of fatty acids with varying unsaturation were fed to lactating cows. Low rumen pH depressed milk fat percent; low linoleic acid in milk fat with dietary soya soap suggested rumen dissociation and biohydrogenation of the soap fatty acids. Calcium soaps may require maintenance of rumen pH above 6. Key words: Calcium soaps, unsaturated fatty acids, milk fat, biohydrogenation

INFLUENCE OF DIETARY CALCIUM-PHOSPHORUS LEVELS ON APPARENT ABSORPTION OF MINERALS AND NITROGEN DURING GROWTH AND REPRODUCTION IN GILTS

A higher Ca-P intake during finishing, gestation and lactation periods increased (P < 0.05) the apparent absorption (g/day) of Ca and P during all three periods. Nutrient absorption appeared to differ for Lacombe and Yorkshire gilts. Key words: Calcium, phosphorus, nitrogen, absorption, gilts