Masters Degrees (Animal Sciences)

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Browsing Masters Degrees (Animal Sciences) by browse.metadata.advisor "Coetzee, J."

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    Development and evaluation of polymer coated urea as a potential slow-release urea supplement for ruminants
    (Stellenbosch : Stellenbosch University, 1999) Upton, Erlanda; Coetzee, J.; Cruywagen, C. W.; Sanderson, R. D.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science .
    ENGLISH ABSTRACT: The rate of hydrolysis of urea in the rumen of animals is a major limitation when considering the substitution of natural protein with urea in the formulation of rations. The aim of this study was to evaluate polymer coated urea prills with variable coating thickness and evaluate its potential as a slow-release NPN compound. A new slowrelease urea compound, made by coating prilled feedgrade urea with a co-polymer of urea-formaldehyde resin and a castor-coconut alkyd was initially evaluated for urea-nitrogen concentration in distilled water in order to evaluate its potential as a slow-release urea product for ruminants. Amino/alkyd or polyester blends are among the cheapest of the modern synthetic systems and are considered because it is non-toxic, low-cost, biodegradable and easy to manufacture. A 2 x 2 x 2 x 2 factorial design was used and 16 individual products were made and evaluated. The Wurster method was used to encapsulate urea prills. The slopes of the urea release curves represented the release rate of the encapsulated products and were compared to identify the process variables, which had an effect on release rate. Two of the coating variables, coating weight and alkyd: resin ratio, had a major effect (P = 0.0001) on the release rate of urea. The crushing strength of encapsulated products was significantly (P = 0.0001) higher than that of untreated urea. Results motivated the evaluation of the products in the rumen of sheep in terms of rumen ammonia and blood urea N concentrations. Four slow-release products were made after interpreting results from the first study, and differed on account of the coating weight and the composition of the co-polymer. Fifteen fistulated wethers were randomly allotted into 5 groups and intraruminally received an equivalent of 15g urea. Rumen ammonia and blood ammonia were taken at 0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 and 48 h after administration of the various treatments. Slow release urea (SRU) resulted in significantly lower rumen ammonia peaks (P = 0.0001) than untreated urea, while the peaks were also significantly delayed. Untreated urea resulted in the maximum concentration at two hours after administration of the urea (P = 0.0685) while the SRU's reached a maximum at six hours after administration in the rumen. No significant differences between the four different SRU types were found. Responses in blood urea-N was similar to that observed for rumen ammonia nitrogen. The encapsulation was effective in decreasing the rate of ammonia release from the urea for up to six hours after administration. In a third trial four Dehne Merino wethers were used in a 2 x 2 Latin square design. They received a SRU product equivalent to 0.4 g urea per kg body weight orally. Rumen liquor and blood samples were taken at 0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 and 48 h after intake. Difficulty was initially experienced with ingestion and palatability of the SRU products due to the strong formaldehyde and butanone odour present in the coating. The maximum rumen ammonia (NH3) concentration for the SRU were lower than that of untreated urea (17.5 mg N/dl vs. 66.9 mg N/dl). The time to reach blood urea levels also differed considerably (6 h vs. 24 h for blood urea nitrogen) between treatments. The encapsulation of urea prills shows potential solutions to reduce the solubility of urea and also reduce the hygroscopic nature of urea and improve the palatability and storage characteristics thereof. Keywords: Slow-release urea, encapsulate, copolymer, urea formaldehyde rumen ammonia, blood urea nitrogen, solubility, palatability, storage characteristics.
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    Effect of forage type and cottonseed supplementation on the production of dairy cows
    (Stellenbosch : Stellenbosch University, 1997) Breytenbach, Stephan; Coetzee, J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
    ENGLISH ABSTRACT: The type of forage seems to influence the production response of dairy cows receiving supplements of whole cottonseed. Literature indicated that supplementation of whole cottonseed in diets with maize silage as the only dietary forage resulted in improved milk yields but depressions in the milk fat content. It was also indicated in the literature that milk fat depression was alleviated when 10 to 20% of the maize silage were substituted with luceme hay. Oat silage is the main source of forage for large numbers of lactating dairy cattle in the Western Cape. The question that needs to be answered is whether this depression in milk fat is a property of maize silage, or also of oat silage. Diets containing approximately 7% fat (DM), mainly from whole cottonseed, and approximately 3% fat (DM) were used to evaluate the in sacco degradability of oat silage, maize silage and luceme hay. The degradability of the samples in the rumen was fitted on the exponential equation p =a+ b(l - e-ct). Effective degradation ofDM, OM, NDF and ADF was calculated for each treatment by introducing fractional outflow rates of 0.02, 0.05 and 0.08/h. There was no difference in the degradability of the three forages within the same diet. Effective degradability of DM, OM and ADF did not differ in effective degradability between the two diets. The effective NDF degradability was lower (p < 0.05) in the cottonseed supplemented diet at an outflow rate of 0.08/h. The oat silage in six commercial diets was substituted at different rates by luceme hay. Diets contained either whole cottonseed supplemented at 18% of DM or no inclusion of cottonseed. Twelve lactating dairy cows were used in a change-over experimental design. The inclusion of whole cottonseed did not affect milk yield, improved (p < 0.05) milk fat percentage from 3.09 to 3.33% and decreased (p < 0.05) milk protein percentage from 2.84 to 2.75%. Dry matter intake was significantly lower (p < 0.05) on the whole cottonseed diets (17.8 vs. 18.2 kg/cow/day). As expected, the inclusion of whole cottonseed shifted the fatty acid composition of milk fat from short chain fatty acids to more longer chain fatty acids. It was difficult to quantify this change in fatty acid composition due to interactions between the levels of forage and the cottonseed inclusion. The inclusion levels of oat silage and luceme hay were compliments of each other. Significant differences could therefore be due to the increasing levels of luceme hay or the decreasing levels of oat silage. An increase in the amount of luceme included in the diets led to significant differences in almost all the production responses measured Milk fat percentage being the only exception. Even milk fat percentage showed an increase, although not significant. Whole cottonseed can be included in diets with oat silage as the only dietary forage. The price of whole cottonseed, the milk price structure of the milk buyer and the genetic potential of the cows will determine the economic viability of whole cottonseed inclusion.
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    Evaluering van die insluiting van 'n kommersiele stadig vrystellende ureum-melasseproduk (ureied) in lekke vir skape op laegraadse ruvoer
    (Stellenbosch : Stellenbosch University, 1998-03) Bohme, Heinrich Martin; Cruywagen, C. W.; Coetzee, J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
    ENGLISH ABSTRACT: An experiment was conducted to study the potential of a liquid slow-release urea-molasses product (Bonded Urea Plus®) for the inclusions in licks for ruminants. Six ruminal fistulated Merino wethers receive low-quality wheat straw (<3% crude protein) ad lib during Phase 1. Each sheep received 6 different licks over six 11-day treatment periods in a crossover design, which contained different sources of carbohydrates together with urea/molasses or Bonded Urea Plus® (BUP) Licks U & BU served as controls and did not contain any carbohydrates, while Licks UME & BUME included molasses meal (sugar source) and Licks UMI & BUME maize meal and starch (starch source) in addition to either urea/molasses or BUP.
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    Die verbetering van die benutting van laegraadse ruvoer vir wol- en vleisproduksie deur aanvulling van beskermde proteienbronne en/of aminosure
    (Stellenbosch : Stellenbosch University, 2002-04) Burger, Willem Jacobus; Cruywagen, C. W.; Coetzee, J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
    ENGLISH ABSTRACT: Low quality roughage is often used in the Western Cape as the only source of roughage for the young growing ruminant. Production levels of these animals is unsatisfactory and therefore supplementation is required. It is necessary when small grains are fed to also include protein sources in the diets. For high production, these protein sources must also be protected against rumen degradation. Good results are reported with the treatment of sunflower oilcakemeal (SFOCM) with formaldehyde (0.86 g formaldehyde per 100 g protein). Protecting methionine with 2-methyl maleic anhydride results in an increase in wool production. This study looked at the effect on dry matter intake (DM-intake), wool production and live weight change with supplementing a low quality diet with urea, SFOCM and formaldehyde protected SFOCM (FSFOCM). These diets where also supplemented with no methionine, methionine and 2-methyl maleyl methionine (MMM). The DM-intake of total diet are increased (P<0.05) with the supplementing of oats straw and barley (1.1% of live weight) diet with SFOCM and FSFOCM (949 & 935 vs 848 gis/d). Supplementing MMM decreased (P<0.05) the DM-intake with 9 %. Supplementing FSFOCM increased (P<0.05) live weight change from 19 to 44 gis/d. Wool production are increased (P<0.05) with 38 % with supplementation of MMM. The apparent digestibility of crude protein (CP) of the urea diet are increased (P<0.05) by supplementing methionine when compared with no methionine supplementation (67.28 vs. 71.23 %). The apparent digestibility of crude protein (CP) of the SFOCM diet (63.71 and 64.96 vs. 70.15 %) and FSFOCM diet (66.39 and 66.26 vs. 70.89 %) are increased (P<0.05) by supplementing MMM when compared with no methionine and methionine supplementation. The apparent digestibility of fat of the SFOCM diet (61.01 and 65.65 vs. 48.33 %) and FSFOCM diet (60.93 and 63.83 vs. 38.14 %) are decreased (P<0.05) by supplementing MMM when compared with no methionine and methionine supplementation. The apparent nitrogen balance of the SFOCM diet (-0.15 and 5.41 vs. 4.62 gis/d) and FSFOCM diet (2.93 and 5.60 vs. 6.02 gis/d) are increased (P<0.05) by supplementing MMM when compared with no methionine and methionine supplementation. The DM- and CP-degradability of barley and DM-degradability of oats straw did not differ (P<0.05) between different protein treatments. The higher production with the supplementation of amino acids and proteins can be associated with more amino acids available in the lower digestibility tract and not as a result of better rumen function.