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Biomedical subjects

G W Reid

Publications and source records attributed to G W Reid.

13 recordsLinked to original sources
PubMed1994

Parturient hypocalcaemia in dairy cows: effects of dietary acidity on plasma minerals and calciotrophic hormones.

Mature Friesian cows were given silage plus either an alkaline or an acidic concentrate mix during the last 28 days of pregnancy in two experiments. There were no significant differences in plasma calcium, phosphorus or magnesium concentrations before parturition but the blood ionised calcium and plasma chloride concentrations were significantly increased, together with a lower blood pH and acid-base excess in the cows on the acid diet. The mean 1,25-dihydroxyvitamin D concentrations tended to increase before parturition in the cows on the acid diet compared with the alkali diet in experiment 1 and were significantly higher in experiment 2. At parturition, the acid-fed cows had higher mean plasma calcium concentrations and significantly more of them had values > 2.0 mmol litre-1 than the alkali-fed groups, and the plasma 1,25-dihydroxyvitamin D and parathyroid hormone concentrations were related to these different plasma calcium concentrations. The acidic diets therefore appeared to prevent the onset of hypocalcaemia at parturition by increasing the plasma 1,25-dihydroxyvitamin D concentration before parturition.

Analysis of Variance↗
PubMed1985

Use of by-products and supplementary protein in dairy cow nutrition.

The new systems of protein evaluation distinguish clearly between the requirement of the rumen microbes and the need of the host animal. While the requirement of the rumen microbes and the production of microbial protein is related to fermented energy, the need of the host animal varies with type and level of productivity. In dairy cows microbial protein is insufficient for the host animal, particularly when the animals are in negative energy balance, and in order to efficiently utilise body energy reserves undegraded protein must be given. Several experiments are discussed in which dairy cows have been given ammonia treated straw as the only source of roughage and where milk yields have been maintained. It is emphasised that increased use of high roughage diets in early lactation increases the demand for undegraded proteins. The converse is also true: that undegraded protein increases the proportion of roughage that can be used for high yielding dairy cows.

Animal Feed↗
PubMed1985

Treatment, waste management and cost for removal of radioactivity from drinking water.

The processes (costs, efficiencies and reliability) used in treating drinking water for removal of radioactive contaminants and the disposal of wastes generated by the treatment processes are analyzed and discussed. The study was limited to U, Ra and Rn. Initially concepts of water and waste treatment in terms of their applicability to the drinking water industry were established. The alternative processes for treatment of Ra, U, Rn, water and sludges were described and evaluated, in terms of cost, efficiency, reliability, process control and feasibility.

Adsorption↗
PubMed1981

Effects of feeding level in late pregnancy and dietary protein concentration during early lactation on food intake, milk yield, liveweight change and nitrogen balance of cows.

Thirty-nine British Friesian cows and 17 British Friesian heifers were used to measure the effects on milk yield, food intake and digestion, and N balance of increasing the protein concentration in the diet from 111 to 147 g crude protein/kg day matter during the first 16 weeks of lactation. The comparison was made for animals given food either ad lib. or at a level which allowed them to gain 0.5 kg/d during the 8 weeks before parturition, and for animals given ad lib. diets of either 60:40 or 40:60 hay:concentrate ratio during early lactation. Milk yield was increased by a higher protein concentration in the diet (P less than 0.01) and the increase was evident from the first week of lactation. Mean increases over the first 8 weeks of lactation were 3 kg/d for animals on the diet of high roughage content and 7 kg/d for animals on the diet of low roughage content. A higher crude protein content in the diet also increased food intake (P less than 0.05) and digestion (P less than 0.05), and the increases were greater for animals given the diet of low compared with high roughage content. Level of feeding before parturition did not influence food intake or milk yield and there were no differences between cows and heifers in their response to treatments. N balance over the first 10 weeks of lactation averaged -13 g/d for cows and 6 g/d for heifers (P less than 0.025), and was not significantly altered by treatments. Mean N balance of all animals was estimated to increase from -37 g/d immediately after parturition to zero at 8 weeks of lactation. The results demonstrate that an increased protein concentration in the diet during early lactation is associated with increased food intake and digestibility of food, which are in the turn largely responsible for higher levels of milk production.

Animal Feed↗
PubMed1981

The effects of protein degradability and food intake on milk yield and composition in cows in early lactation.

1. In two experiments measurements were made of food intake, live-weight change, milk yield and milk composition in early lactation when dairy cows were given diets containing varying proportions of protein as fish meal (low rumen degradability) or as groundnut meal (high rumen degradability). In a preliminary trial measurements were also made with cows given supplements of either fish meal or barley and fed at a restricted level of feeding. 2. When metabolizable energy (ME) intake exceeded 160 MJ/d there was no evidence of responses to changes in protein degradability, ut at ME intakes below 135 MJ/d increases in the supply of undegradable protein led to increases in fat-corrected milk yield, protein content and live-weight loss. 3. The interaction between energy intake and protein degradability is unexpected because net protein:net energy requirement increases as milk yield increases, but may be explained in terms of differential effects of changing rumen outflow rates on degradabilities.

Animals↗