Call number: LD2668 .T4 1956 T38 / Master of Science

Please read the abstract in the section 00front of this document / Dissertation (MSc (Agric))--University of Pretoria, 2006. / Animal and Wildlife Sciences / unrestricted

In the first part of this study, the relative in situ rumen degradabilities of some common Kenyan feedstuffs were estimated using two fistulated steers. The second part of the study attempted to manipulate rumen fermentation processes by heat treating dietary protein, and also by varying the hay particle size. The in situ dacron bag technique was used to estimate the feeding value of some common Kenyan forages. The rate and extent of dry matter (DM) and crude protein (CP) degradation in the rumen was then determined from the incubated samples. Effective DM and CP degradation was also estimated at various rumen digesta flow rates. Green maize chop, fodder sorghum, napier grass, kikuyu grass, Pennisetum trachyphyllum, rhubarb leaves, banana leaves, sweet potato vines, desmodium and lucerne had moderate to high DM and CP degradability (>50%). These feedstuffs would therefore offer greater potential for conservation for feeding dairy cattle in the dry season. Wheat straw, maize stover, red oats grass and naivasha stargrass had significantly (P<0.05) lower rumen degradability. This last group would require supplemental energy and nitrogen in order to meet the dairy cow's nutrients requirements. Wheat bran had a high DM degradability but its CP degradability was low. The digestibility and amino acid availability of its protein requires further investigations. The effects of forage particle length and heat treatment of protein sources on intake, milk yield and composition and, ration digestibility were determined using dairy cows. Normal or heated canola meal and dehydrated alfalfa were fed together with orchard grass hay to 24 lactating Holstein cows. Orchard grass hay was chopped to two mean cut lengths i.e 14.19 and 1.71 mm. In situ results showed that both canola meal and alfalfa proteins in the supplement was made indigestible by heat. Heat treatment did not affect in vivo dry matter (DM), crude protein (CP) and acid detergent fibre (ADF) digestibility for the complete canola rations. Milk yield was also not significantly affected by heating canola meal. However, neutral detergent fibre (NDF) digestibility, voluntary feed intake, butter fat and milk protein contents decreased with heat treatment. Reduced forage particle size in combination with heat treatment resulted in significantly lower DM, CP, and ADF digestibility. There was no significant change in voluntary feed intake, milk yield or its components, (except lactose content), with reduced hay particle size. Lactose content was significantly higher with long chop hay. Heat treatment of "alfalfa and short hay particle size resulted in lower DM and CP digestibility of the complete rations. ADF digestibility and voluntary feed intake were reduced with heat treatment. Hay particle size did not affect voluntary feed intake significantly. Milk yield and its components increased with heat treatment of alfalfa. Only total milk fat increased with the longer chop hay. / Land and Food Systems, Faculty of / Graduate

Three experiments were conducted to study the sensitivity of the pH-stat (in vitro) method in the prediction of true digestibility (TD), as measured by amount of base added, of plant proteins, either alone or in the presence of specific additives (nitrogen-free mixture, vitamin mixture and/or mineral mixture) as part of a complete diet of plant proteins that had been subjected to various levels and forms of heating. The in vitro TD values were then compared with TD values obtained in. vivo (Wistar rats). In experiment 1, the effect of temperature (dry-heating at 80, 100, 120, 150, 180 and 240° C or autoclaving at 121° C) and time (30, 60, 120 and 240 minutes) of heat application on in vitro base consumption (BC) was measured in 3 grains (wheat, barley and sorghum) and whole defatted soybeans. The largest increase in BC measured by the pH-stat method was that of soybeans in response to 30 minutes of autoclaving. Dry heating had various effects on the BC by soybeans, depending upon temperature and time of application, but none of the treatments was as beneficial as autoclaving. Mild, dry-heating of grains at 80-120° C improved BC slightly. The improvement was most marked for wheat. Both dry-heating of grain at temperatures above 120° C and autoclaving reduced the BC significantly for all durations. In experiment 2, the effect of inclusion of non-protein dietary components (minerals, vitamins and a nitrogen-free mixture, singly and in combination) on in. vitro BC measured by the pH-stat method of wheat and fat-extracted soybeans (both proteins in the raw and autoclaved forms) was monitored. For the wheat treatments, the inclusion of a mineral mixture significantly (p<0.001>) increased digestibility. This effect was greatest with autoclaved wheat. It was concluded that, in general, the presence of minerals increased the rate of hydrolysis. With raw soybeans, the distinction between treatments was less well-defined. The treatments containing vitamin or nitrogen-free and mineral combination mixtures were digested to a significantly greater extent than the raw soybeans alone. With autoclaved soybeans, additives had no effect. This lack of response to additives may have been due to the rather large amount of base required by the autoclaved soybean protein alone. In experiment 3, a series of rat-feeding trials were conducted in conjunction with in. vitro digestions. Diets were fed to groups of Wistar rats to determine TD, Biological Value (BV), and Net Protein Utilization (NPU) in vivo. Although BV was measured it was not relevant for this work. Concurrently, the same diets were tested for in. vitro TD by the pH-stat method. Specific regression equations were developed for each protein-type tested, after it was determined that a much lower correlation coefficient was obtained when one general equation was utilized. The newly-developed equations followed the format y = a + bx, where y = TD (as a part of one), a = the y-intercept, b = slope of the function and x = ml 0.10N NaOH added during the 10-minute digestion. Regression equations, correlation coefficients (r) and standard errors for each regression (s) between in. vitro and in vivo true digestibility of proteins were as follows; Soybean, soybean (autoclaved), soybean/wheat combinations (n = 6) r = 0.93 TD = 0.7868 + 0.2175x s = 0.018 Sorghum (raw, autoclaved, 90° C, 120° C, 180° C dry-heated, steamed) (n = 6) r = 0.92 TD = 0.4575 + 1.8841x a = 0.058 Alfalfa pellets/hay in combination with either wheat or barley (n = 13) r = 0.91 TD = 0.3446 + 1.0356x s = 0.046Alfalfa hay and barley combinations (n = 5) r = 0.96 TD = 0.2360 + 1.3194x s = 0.048 Grains (19 barleys, 10 triticales, 6 sorghums, and 2 wheats) (n = 37) r = 0.74 TD = 0.7419 + 0.4759x s = 0.044 In general, it can be stated that the pH-stat method is a useful method for screening proteins for the effect of various treatments on digestibility. Damage due to abnormally severe processing conditions (i.e. heating) is readily detected by the pH-stat technique as indicated by a decrease in the amount of base consumed during enzymatic hydrolysis. / Land and Food Systems, Faculty of / Graduate

This study is a comparison of the growth of albino rats fed on a diet containing beef protein with the growth of albino rats fed on a diet containing peanuts as the source of protein.

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No description available.

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M. S.

Captive gray squirrels were fed acorns or diets containing commercial tannins to determine the effects of tannins on digestion and detoxification (glucuronidation) activity. In the Acorn experiment, Northern red oak acorns (Quercus rubra), white oak acorns (Q. alba), or rat chow were fed to squirrels. Levels of phenols, condensed tannins, and hydrolyzable tannins were higher in red oak acorns than white oak acorns and were likely responsible for the lower dry matter intake, lower apparent protein digestibility, lower digestible protein and energy intakes, and higher glucuronidation activity observed in squirrels fed red oak acorns. Although apparent protein digestibility and digestible protein intakes were reduced on a white oak acorn diet, this diet did not continuously suppress dry matter intake or stimulate glucuronidation. It appears that gray squirrels may not be able to subsist on red oak acorns alone, but may require other foods to dilute tannin intake and provide additional nutrients. In the Tannin experiment, squirrels were fed rat chow containing no tannins, 4% or 8% tannic acid (hydrolyzable tannin), or 3% or 6% quebracho (condensed tannin). Apparent protein and energy digestibilities of tannic acid-containing diets were lower than the control. These reductions were likely due to the formation of strong complexes between protein and high molecular weight gallotannins. These complexes may have simultaneously protected these gallotannins from hydrolysis and allowed tannic acid to reduce digestive efficiency. Apparent protein and energy digestibilities of quebracho-containing diets were reduced, indicating protein complexing by these nonhydrolyzable tannins. Consistent with the hypothesis that hydrolyzable tannins are more likely to be broken down and absorbed internally than condensed tannins, only the 8% tannic acid diet tended to increase glucuronide excretion. / Master of Science