Studies in ruminant nutrition with particular reference to non-protein nitrogen and phosphorus

Fishwick, Graham (1974) Studies in ruminant nutrition with particular reference to non-protein nitrogen and phosphorus. PhD thesis, University of Glasgow.

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The work described is concerned with investigations into the fortification of dried molassed sugar beet pulp with non-protein nitrogen, phosphorus, trace elements and vitamins. Materials containing between 3 and 11 % of added urea and with up to 17 and 40% crude protein and 0.55 % phosphorus were manufactured. The cubed products were evaluated in a wide range of nutritional studies with ruminants. The General Introduction gives an account of the metabolism of urea in the ruminant together with a review of the methods available for reducing the potential toxicity of dietary non-protein nitrogen. Section 1 describes investigations into the release rate properties of urea-containing molassed sugar beet pulp cubes. Experiments in vivo indicated that both the size and hardness of the cubes were important factors determining the rate and degree of ammonia production in the rumen. Whole hard molassed sugar beet pulp cubes were shown to have superior slow release properties to those of either a softer cube or a smaller barley based product containing similar quantities of urea. In Section 2 urea phosphate, mono-ammonium phosphate and a granular ammonium polyphosphate were evaluated in balance trials with growing sheep as possible combined phosphorus and nitrogen supplements for inclusion in molassed sugar beet pulp" When mixed with additional urea and compared with equivalent amounts of phosphorus and nitrogen supplied as dicalcium phosphate and urea each material promoted similarly improved nitrogen and phosphorus retentions. Section 3 describes the evaluation using growing sheep of a magnesium phosphate and a calcium magnesium phosphate as combined phosphorus and magnesium supplements. Comparisons were made with equivalent amounts of phosphorus and magnesium given as dicalcium phosphate and magnesium oxide. All three phosphorus sources promoted comparable daily retentions of phosphorus. The magnesium of both combined phosphorus and magnesium supplements was as well utilised as that of magnesium oxide, Magnesium phosphate was shown to be an effective prophylactic agent for the prevention of hypomagnesaeinic tetany in lactating beef cows. In Section 4 the effect of urea and phosphorus contained in molassed sugar beet pulp on the voluntary consumption of low-protein roughage feeds was studied. Inclusion of either 3.0 or 7.8 % urea in 1 kg per day of molassed sugar beet pulp containing 0.55 % phosphorus similarly increased the voluntary intake of oat straw by steers by about 20 %, Increased straw intake was accompanied by an improvement in the digestibility of the dry matter and crude fibre of the straw. The addition of 3.0 % urea to 2.7 kg per day of molassed sugar beet pulp increased the voluntary consumption of oat straw by pregnant beef heifers by about 21 %. Increasing the total phosphorus intake of the heifers from about 6 to 17 g P/day with dicalcium phosphate did not increase straw intake in either the presence or absence of additional urea. Supplementation with urea tended to increase the digestibility of the straw and the concentration of glucose in the blood plasma. The voluntary consumption of hay was reduced by about 20% in late pregnancy when no supplementary urea was given. A continued low protein intake in late pregnancy did not influence the immune lactoglobulin concentration in the colostrum of the heifers or the birth weight or quantity of immune lactoglobulin absorbed by their newborn calves. Section 5 describes experiments in which a molassed sugar beet pulp product containing 32 % crude protein was compared with a mixture of equal parts of decorticated groundnut and cottonseed meals as a protein source for rapidly growing 100 kg steers. Both forms of supplementation equally and significantly increased live-weight gains and improved food conversion ratios compared with those recorded for an unsupplemented diet. A high urea molassed sugar beet pulp product was somewhat less effective than a conventional protein source as a supplement for rapidly growing 20 kg sheep. In Section 6 molassed sugar beet pulp materials containing either 2.7 or 7.8 % of added urea were used to replace about one- half of the additional protein derived from vegetable protein sources in a milk production concentrate given to dairy cows. The concentrate mixture containing the high urea molassed sugar beet pulp material presented considerable palatability problems and was associated with a marked decline in milk yield. Fully satisfactory milk yields were obtained with the milk production concentrate which included 50 % of the molassed sugar beet pulp material supplemented with 2.7 % urea.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: R G Hemingway
Keywords: Animal sciences
Date of Award: 1974
Depositing User: Enlighten Team
Unique ID: glathesis:1974-72363
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:12
Last Modified: 24 May 2019 15:12

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