J. Duckworth

Studies of the skeleton of the sheep I. The effect of different levels of dietary calcium during pregnancy and lactation on individual bones

1. Three groups of mature ewes were fed during pregnancy and lactation on rations differing in their calcium content. The mean daily intakes of calcium were 1·4 g. (group A), 4·5 g. (group B), and 7·4 g. (group C). Blood samples were analysed monthly for calcium and inorganic phosphorus. The ewes were killed at approximately 100 days after parturition and the skeletons isolated. Individual bones, either whole or divided into definite fractions, were analysed. 2. The level of calcium intake was without effect on the number of lambs born, birth weight, or growth while milk fed. 3. Blood calcium was significantly lower in group A than in groups B and C, but blood inorganic phosphorus was unaltered. 4. The resorption of bone substance was greater in group A than in groups B and C. 5. The severity of resorption varied between bones, and in regions within certain bones. Resorption was most severe in the vertebrae and pelvis, and only slight in the metacarpal, the metatarsal and the shafts of other long bones. Resorption of intermediate magnitude was found for the remainder of the skeleton. 6. Resorption was accompanied by reductions in the percentages of ash in bones, but this effect was proportionately less than the ash weight reduction. 7. Radiological observations made on flesh-free bones at the end of the experiment gave a picture of resorption similar to that presented by the data for ash weights and percentages of ash, namely that resorption was much greater in group A than in groups B and C.

Economies in the use of animal by-products in poultry rations: II. Vitamin and amino-acid provision for laying hens

1. Birds fed on rations devoid of animal byproducts from hatching until 18 months of age were equal in laying performance and health to those that had received animal supplements. 2. The stimulation of early growth by feeding aureomycin did not affect the final weight of pullets, their egg production or the incidence of broodiness. 3. The ‘animal protein factor(s)’ was of limited importance for egg production. There was a suggestive indication of an effect of a deficiency of the factor(s) when birds on an all-plant ration had been laying for 6 months without access to their droppings. Limited access to ‘unfermented’ droppings, which provided the only dietary source of the factor(s) during both rearing and laying periods, was sufficient to meet the need of the birds for sustained egg production.

Nutrient interactions in pig nutrition I. Factors affecting the response to vitamin B 12 in growing pigs

In the United States many practical pig and poultry rations are characterized on the one hand by containing little or no protein of animal origin, and on the other hand by being fortified with a variety of supplements intended to be sources of essential vitamins and unknown growth factors. In pig feeding, where an animal by-product is used, it is frequently tankage, a material in which the protein is of variable and generally low nutritive value. The possibilities of following this trend in the United Kingdom have already been discussed with reference to the design of poultry rations (Carpenter & Duckworth, 1951 a; Carpenter, Duckworth & Ellinger, 1954). I t has also been clearly demonstrated that, for one closely denned system of pig feeding used in the United Kingdom, either groundnut or soyabean meal can be used satisfactorily as the sole source of supplementary protein in place of fish meal, and equal (or very nearly equal) results obtained without the inclusion of any special vitamin supplements (Woodman & Evans, 1951; Evans, 1952). The experiments described below were undertaken to study the effects of adding vitamin B12 supplements to practical rations, some of which resembled those of Woodman & Evans, and of using different feeding scales.

The nutritive value of herring ‘alkali-reduction’ meal for chicks

1. Herring ‘alkali-reduction’ meal—a by-product from the alkali process of herring oil extraction—has been tested as a protein supplement for chicks. 2. At high levels of feeding it was toxic. 3. At low levels of feeding its nutritive value was low compared with other fish meals. 4. The method of manufacture of reduction meal destroys vitamin B 12 and cystine, but supplementation of the material with vitamin B 12 and cystine did not greatly enhance its feeding value.

Studies of the skeleton of the sheep VII. A further comparison of skeletal resorption during pregnancy and lactation in ewes fed diets differing in digestible crude-protein value

1. An experiment has been carried out to compare the results of feeding the B-group diets of Parts II and III of this series to ewes during pregnancy and lactation. 2. The ewes fed a diet containing maize in place of dried molassed sugar beet pulp again maintained better bodily and skeletal condition. 3. The basis for other experiments in this series is discussed.

Studies of the skeleton of the sheep VIII. Studies of the effects of protein and energy intake on productivity and skeletal mineralization in the pregnant and lactating ewe

1. Effects on productivity and skeletal mineralization of high as opposed to moderate levels of protein and, or, energy intake by the ewe during pregnancy and lactation in the presence of adequate calcium, phosphorus and vitamin D have been studied. 2. Two experiments were undertaken. One experiment used 4½-year-old Cheviot ewes and the other used 3½- and 4½-year-old Scottish Blackface ewes. Weight records, blood samples and in vivo and flesh-free radiographs were obtained, and bone ash determinations were carried out. 3. The results showed that contrary to indications from earlier experiments in this series superiority in ewe weight, lamb growth, and mineralization of the ewe skeleton did not necessarily result from raising the protein and, or, energy values of the feed above the ‘moderate’ level. 4. Discrepancies between the in vivo and flesh - free radiological assessments were noted for consideration.