Please read the abstract in the section 00front of this document / Dissertation (M Inst Agrar (Animal Production Management))--University of Pretoria, 2006. / Animal and Wildlife Sciences / unrestricted

No abstract available / Dissertation (MSc (Agric) Animal Nutrition)--University of Pretoria, 2006. / Animal and Wildlife Sciences / unrestricted

To investigate the whole body metabolism of selenium (Se), isotope kinetic studies were undertaken in which indwelling catheters were implanted in the jugular veins of pregnant and nonpregnant ewes as well as the inferior vena cava and saphenous veins of 110-120 day (d) old ovine fetuses. A single injection of ⁷⁵Se-sodium selenite was administered and blood samples were obtained at various times. A 5 d Se balance trial, which commenced on the day of tracer experiment, was also undertaken. The plasma ⁷⁵Se specific activity data were used for determining the kinetic parameters of Se metabolism and the placental transfer rates. Using the Se balance and tracer data the net absorption and the fecal losses of Se were calculated. The fractional rate constants and T½ Se utilization in individual tissues were estimated by sacrificing the ewes and the fetuses at different times after the tracer injection and determining the tissue ⁷⁵Se specific activities. The effect of Se deficiency on the kinetics, placental transfer, net absorption and tissue metabolism was studied in a similar manner by feeding the ewes with Se deficient rations. The mean plasma Se concentrations in the positive nonpregnant and pregnant ewes were 142 187 ng/ml and were significantly higher than Se and the corresponding values (82 and 69 ng/ml) in the Se deficient ones respectively. The plasma Se levels in the Se positive fetuses (46 ng/ml) were not significantly different from the deficient ones (53 ng/ml). The irreversible disposal (ID) rates of Se were 7 ug/d/kg body weight (B.W.) in both nonpregnant and pregnant ewes, whereas, these values declined to 2 ug/d/kg B.W. under deficiency conditions. The ID values in the Se positive and deficient fetuses were 20 and 11 ug/d/kg B.W. respectively. These results indicated that the plasma Se turnover was lower in Se deficient animals than in the positive ones and that the fetuses had a higher turnover than adult ewes irrespective of the maternal Se status. Values for net Se absorption (% Se intake) and fecal Se losses (ug/d) in the Se positive nonpregnant ewes were 51% and 272 ug/d versus 97% and 25 ug/d in the Se deficient ones. The corresponding values for the Se positive pregnant ewes were 56% and 241 ug/d as against 84% and 27 ug/d in the deficient ones. These results suggested that the efficiency of net Se absorption expressed as the percent of Se intake decreased with increasing Se intakes and that the fecal route exerted a homeostatic control on Se metabolism in ewes. The tissue Se concentrations were significantly higher in the Se positive animals than in the deficient ones, whereas, the tissue fractional rate constant values were higher in the Se deficient animals than in the positive ones. These results implied that the tissue Se concentrations were significantly decreased under Se deficiency conditions and that the Se turnover was higher in tissues when the dietary Se intake was minimal. The placental transfer studies showed that there was a bidirectional exchange of Se across the placenta. The placental Se transfer rates from ewe to fetus declined from 53 ug/d in the positive ewes to 29 ug/d in the deficient ones. The rate of Se transfer from fetus to ewe also decreased from 24 ug/d in the positive ewes to 12 ug/d in the deficient ones. The net placental Se transfer was found to be reduced under conditions of decreased maternal dietary supply. The nutritional implications of Se status of the pregnant ewes on the availability of the trace mineral to the fetus have been discussed. / Land and Food Systems, Faculty of / Graduate

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

The effect of increasing the calcium content of a hay-grain diet fed to postparturient dairy cattle was studied. Mineral apparent digestibilities, serum concentrations and apparent mineral retentions were monitored while the animals were under the stress of peak lactation. Nine Holstein and seven Ayrshire cows were randomly assigned to the control (0.7% Ca) or the Ca-treatment (1.5% Ca) based on calving order. The diets otherwise contained adequate nutrients. Each animal was fed to appetite for 80 days with no difference (p > . 05) occurring between treatments in intake when expessed as a percentage of body weight. Daily milk production (4% FCM) was higher (p < .05) as was the average body weight (p<.01) for the control animals reflecting the disproportionate number of young animals on the calcium treatment. After a minimum of 60 days on trial, 5 cows from each treatment were exposed to a 5 day digestibility collection period. No change in organic matter or nitrogen apparent digestibility occurred (p>.05) but there were higher (p<.05) levels of calcium and iron, increased (p<.01) levels of copper, and lower (p<.05) zinc and molybdenum apparent digestibilities for animals on the Ca-treatment. Fecal pH was higher (p<.05) in the calcium treated cows indicating a buffering effect occurred as a result of the addition of the calcium carbonate. No change (p>.05) was evident in the secretion of minerals into the milk but urinary phosphorus excretion was significantly higher (p<.05) in the control group. Milk progesterone was analyzed to correspond blood samples (average of 14 per animal) to specific regions of the estrus cycle. Serum phosphorus, iron, copper and zinc varied with reproductive cycling as phosphorus dropped (p<.01) at the onset of regular estrus while the other minerals fluctuated with the cycle (copper and zinc (p< .05), iron (p<.01)). In the serum of Ca-treated animals, calcium and zinc concentrations were higher (p<.01), copper increased (p<.05), and phosphorus was lower (p<.01) than the levels for the control animals. Breed effects were apparent as both phosphorus and copper were higher (p< .01) in the serum of Ayrshires than of Holsteins. Plasma glucose concentrations proved not to be different (p>.05) between treatments. Calcium supplementation of the diet allowed the animals to go from a negative to a positive calcium balance (p<.01). It also increased (p<.05) the amount of phosphorus apparent retention. In all, 6 essential minerals had altered apparent digestibilities and/or serum concentrations with possible long term effects on animal metabolism / Land and Food Systems, Faculty of / Graduate

No description available.

<p>For this dissertation, four experiments were conducted to evaluate the effect of dietary addition of exogenous protease and amylase enzymes on growth performance and nutrient utilization in broiler chickens. An additional fifth experiment was designed to determine the role of central and peripheral appetite regulators in birds fed diets deficient in dietary phosphorus (P). This arose from consistent reports in literature of a direct effect of dietary P concentration on feeding response in broiler chickens. </p><p>Experiment 1 examined the growth performance and protein utilization responses of broiler chickens to purified trypsin inhibitors (TI) and exogenous protease additions. Experimental diets were arranged as a 2 × 2 factorial with factors being dietary TI (1,033 or 10,033 TIU/g) and exogenous protease (0 or 15,000 PROT/kg). Protease supplementation improved BW gain (<i>P < </i>0.01) and gain to feed ratio (<i>P < </i>0.05) of birds. The relative weight of pancreas increased (<i>P < </i>0.05) with added TI on d 14 and 21 but was reduced (<i>P < </i>0.001) with protease supplementation. Apparent ileal digestibility (AID) of all amino acids (AA), except methionine, decreased (<i>P < </i>0.001) with added TI, but increased (<i>P < </i>0.05) with protease supplementation. Duodenal trypsin and chymotrypsin activities were reduced (<i>P < </i>0.05) with added TI but increased <i>(P < </i>0.01) with protease supplementation. It was concluded that dietary addition of purified TI negatively affects nutrient utilization by broiler chickens and that the efficacy of the exogenous protease might be independent of dietary TI concentration. A follow-up experiment was conducted (Experiment 2) to evaluate the impact of TI and exogenous protease supplementation on endogenous AA loss in broiler chickens. Four diets were arranged as a 2 × 2 factorial with factors being dietary TI (0 or 8,000 TIU/g) and exogenous protease (0 or 15,000 PROT/kg). There was no effect of TI, exogenous protease, or their interaction on growth performance of birds. Endogenous nitrogen (N) loss and all AA (except Cys) increased (P < 0.05) due to added dietary TI. Exogenous protease had no effect on endogenous loss of N and all AA. The AID of Ca, Fe, Mg, Mn, and Cu was reduced (P < 0.05) by added dietary TI. Protease supplementation improved the AID of Cu (P < 0.01) and K (P < 0.05). Secretion of crude mucin and sialic acid (g/kg DM intake) increased (P < 0.05) with increased dietary TI and was not recovered by protease supplementation. It was concluded from this study that TI increases the endogenous loss of AA, reduces the digestibility of minerals in broiler chickens, and that exogenous protease had no effect on endogenous AA flow, irrespective of added dietary TI. </p><p>In Experiment 3, the responses of broiler chickens fed corn-soybean meal-based diets to dietary α-amylase supplementation during 4 growth phases were evaluated. Birds were assigned to 8 treatment diet in a 2 × 4 factorial arrangement of 2 dietary levels of α-amylase supplementation (0 or 80 kilo-Novo alpha amylase units (KNU) per kg diet) and 4 post hatching growth phases (d 0 to 11, d 11 to 21, d 21 to 42, or d 42 to 56). Body weight gain and feed efficiency of birds improved (<i>P</i> < 0.01) with α-amylase supplementation. There were main effects of α-amylase, growth phase and interaction (<i>P</i> < 0.01) on AID of starch. The total tract retention (TTR) of starch increased (<i>P</i> < 0.05) with amylase supplementation but was not different across growth phases. Amylase supplementation improved (<i>P</i> < 0.05) gross energy utilization in birds, and specifically, during d 11 to 21 post hatching, the viscosity of jejunal digesta and pancreatic amylase activity increased (<i>P</i> < 0.01) with amylase supplementation. The conclusion from the study was that the growth phase of birds may affect the response to exogenous amylase. Following the result of this study, Experiment 4 was conducted to evaluate the effect of amylase supplementation on starch and energy digestibility at various intestinal sites in broiler chickens. Experimental diets comprised 3 concentrations of α-amylase supplementation (0, 80, or 160 KNU/kg diet) and sampling was done on 4 intestinal sites: anterior jejunum (AJ), posterior jejunum (PJ), anterior ileum (AI) and posterior ileum (PI). There were linear and quadratic (<i>P</i> < 0.01) responses of increasing α- amylase supplementation on starch and energy digestibility at the PJ and AI, with only linear effects on TTR of starch (<i>P</i> < 0.05). A linear increase in starch disappearance and digestible energy (kcal/kg) was observed (<i>P</i> < 0.01) with digesta flow from AJ to PJ with increasing amylase supplementation, which may be related to the observed decrease in the viscosity of the jejunal digesta (<i>P</i> < 0.05). Results from this experiment demonstrate the efficacy of exogenous amylase to improve starch, and energy digestibility in broiler chickens, with the highest impact observed in the posterior jejunum.</p><p>A final study (Experiment 5) was conducted to evaluate the impact of dietary phosphorus (P) concentration on hypothalamic molecular regulation of appetite by broiler chickens. Birds were randomly assigned to 3 experimental diets which contained 1.2 (P-deficient), 2.8 (P-marginal) or 4.4 (P-adequate) g/kg non-phytate P (nPP). A decrease in feed intake and BW gain was observed (P < 0.001) in birds fed the P-deficient diet. There was upregulation (P < 0.05) in the mRNA expression of Sodium-phosphate cotransporter (NaPi-IIb), anorexia-related hypothalamic cholecystokinin receptor (CCKAR) and melanocortin receptors (MC3R and MC4R) in birds fed P-deficient diets, whereas cholecystokinin (CCK) mRNA was downregulated (P < 0.01). It may be concluded that a deficiency in dietary P decreases feed intake in broiler chickens by altering the expression of anorexigenic genes in the gut and hypothalamus.</p>

<p>Carbohydrases have been used to improve fiber utilization in monogastric animals. However, their effects on animal performance and nutrient digestibility have been inconsistent in pigs. The efficacy of carbohydrases has been suggested to depend on enzyme activity and fiber composition, but recent evidence suggests other factors like environmental conditions may play significant role. The effect of heat stress (HS) on the efficacy of a multienzyme carbohydrase blend in growing pigs was investigated. It was hypothesized that HS alters the efficacy of carbohydrases. Ninety-six growing pigs (gilts:barrows; 1:1) (initial BW of 20.15±0.18 kg) were randomly assigned to 6 treatments, with 8 replicates of 2 pigs replicate pen in a 3×2 factorial arrangement: three levels of carbohydrase (0, 1X or 2X) and two room temperature conditions (20^oC constant or cyclical 28^oC night time and 35^oC daytime). The 1X is the recommended commercial dose of the enzyme (50g/tonne) and provides 1250 visco-units endo-β-1,4-xylanase, 4600 units α-L-arabinofuranosidase and 860 visco-units endo-1,3(4)-β-glucanase per kg of feed. The 2X dose was 100g/tonne. Pigs were fed ad libitum for 28 days and 1 pig per pen was sacrificed at d28. Heat stress increased the respiratory rate and skin temperature (P<0.001). There was no enzyme × temperature effect on response criteria. Enzyme treatment quadratically increased BW d28 (P=0.025), ADG (P=0.022) and average daily feed intake (ADFI) (P=0.032) with 1X being the highest. Heat stress reduced the BW at d14 (P=0.002) and d28 (P=0.006), average daily gain (ADG) (P=0.005) and ADFI (P<0.001). However, there was a trend of increased gain: feed ratio (G/F) (P=0.093) in the HS pigs compared to the thermoneutral (TN). Heat stress increased apparent jejunal digestibility (AJD) of energy (P=0.039) and apparent ileal digestibility (AID) of calcium (P=0.007). ADFI was positively correlated to ADG (r=0.57; P<0.001) but negatively correlated to G/F (r=-0.42; P=0.003). Enzyme supplementation increased in vitro viscosity at 3, 4 and 5 hours (P value). Heat stress reduced serum glucose concentration on d1 (P=0.0002) but increased serum non esterified fatty acid (NEFA) concentration (P=0.002). A similar trend to NEFA was observed in triacylglycride (TAG). In the jejunum, carbohydrases had trend for increased villi height (P=0.07) while HS reduced villi height (P=0.02). Heat stress increased the jejunal mRNA abundance of IL1β in the jejunum (P<0.001). There was a trend for a reduction in ileal MUC2 (P=0.092), occludin (P=0.091) due to HS, with the trend increasing in PEPT1 (P=0.064). There was no effect of HS on alpha diversity of fecal microbiome, but sampling day affected beta diversity. There was an increase in the abundance of pathogenic bacteria (like Clostridium) in the HS group. Heat stress did not alter the efficacy of carbohydrase but both carbohydrase and HS modulate pig performance independently.</p>

Currently, livestock production in the Andean highlands of Bolivia is done with low food efficiency due to the free range grazing system. This in turn leads to nutritional deficiencies. Therefore, it is necessary to substitute these grass species for others that fulfill nutritional requirements. Our main objective was to determine the species of grass with the best nutritional quality. Of the 12 species, only 11 were analyzed because the species Didtichlis stricta did not germinate. Five monthly samples were taken after the cut (ddc) at the following intervals: 50, 81, 112, 141, and 176 days. These samples were analyzed in the Laboratory of Animal Nutrition via the Weende method. After analyzing the results statistically, it was determined that Agrophyrum elongatum and Festuca aranduniceae were the species that had the highest dry matter yields (9.74 and 8.78 t/ha-1 respectively). In addition, they had higher content of ash, fats, protein, fiber carbohydrates, total digestible nutrients, and digestible energy than the other species also considered as forage with good nutritional quality. We also found that dry matter yield was highest at 209 and 193 days after the cut (ddc).

The objective of this dissertation was to investigate areas that needed further research with regards to phosphorus, phytate, and phytase in monogastric nutrition. To fulfill this objective, a total of 6 studies were carried out.<br>Study 1 was designed to evaluate the additivity of apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of phosphorus (P) in mixed dies containing corn and soybean meal (SBM) and fed to broiler chickens. There were 7 dietary treatments in a randomized complete block design with body weight (BW) serving as the blocking factor. Treatments consisted of 4 semi-purified diets prepared to contain either corn or SBM as the sole source of P with or without phytase supplementation at 1,000 FYT/kg; 2 mixed diets containing corn and SBM with or without phytase addition; and a P-free diet (PFD) formulated to determine the basal endogenous loss (BEL) of P. A total of 512 day-old broiler chicks were fed a commercial starter diet for 21 days while experimental diets were fed for 3 days (day 22-24 post hatching). The BEL of P in broiler chickens as determined by the PFD was 166 mg/kg dry matter (DM). The SID of P in corn and SBM was 52.2 and 65.4 %, respectively. Phytase addition improved (P < 0.05) both the AID and SID of P in the ingredient and mixed diets. There was no difference between the predicted and determined AID and SID of P in the mixed diets and were thus additive. It was concluded that the AID and SID of P in corn and SBM were additive with or without phytase addition. However, we could not be certain if the assumption of additivity will hold true in mixed diets containing ingredients with a higher phytate content and if age of birds affected the BEL of P.<br>In the 2nd study, the additivity of AID and SID of P in mixed diets containing corn and canola meal (CCM) was investigated in broiler chickens at 2 ages. A total of 588 broiler chickens was used in this study. Dietary treatments were arranged as a 2 × 3 × 2 factorial with 2 ages (day 13 and 21), 3 diets (corn, canola meal, and CCM), and 2 levels of phytase (0 and 1,000 FYT/kg) in a randomized complete block design. A PFD was fed to birds at both ages to determine the effects of age on the BEL of P. A commercial starter diet was fed from day 1 to 10 or 18 post hatching and then experimental diets were fed for 3 days until day 13 or 21, respectively. The AID and SID of P was higher (P < 0.05) in birds at day 13 as compared with birds at day 21 regardless of phytase addition. Similarly, the BEL of P in younger birds was higher (P < 0.01) than in older birds at d 21. Regardless of age or phytase supplementation, the predicted and determined AID and SID of P in the CCM diets were similar and thus additive. In conclusion, age influenced the BEL of P and the utilization of minerals in broiler chickens while the assumption of additivity held true when mixed diets containing CCM was fed to birds at both ages with or without phytase addition.<br>In order to evaluate the efficacy of a new consensus phytase variant, the 3rd and 4th studies investigated the responses of broiler chickens to varying concentrations of phytate phosphorus (PP) and the new consensus bacterial 6-phytase variant (PhyG) in the starter and grower phases, respectively. Responses evaluated included growth performance, tibia ash, AID and total tract retention (TTR) of nutrients. A total of 1,152 and 768 day-old male broiler chickens were used in the starter and grower phases, respectively. Dietary treatments were arranged as a 3 × 5 + 1 factorial with a nutrient-adequate positive control (PC) (2.8 g PP/kg) and 15 nutrient-reduced negative control (NC) diets with 3 levels of phytate (NC1, NC2, and NC3 with 2.3, 2.8, and 3.3 g PP/kg respectively), and 5 levels of PhyG (0, 500, 1,000, 2,000, and 4,000 FYT/kg). Rice bran served as the main source of PP in the experimental diets. All treatments had 6 replicates with 12 birds/cage in the starter phase (day 1 to 11 post hatching) and 8 birds/cage in the grower phase (day 12 to 23 post hatching). Birds fed the PC had greater responses (P < 0.05) as compared with birds fed the NC2 diets without phytase at the starter and grower phases. There was no interaction between PP and PhyG on responses of birds in the starter phase but there was an interaction effect (P < 0.05) on the AID of some amino acids (AA) in birds at the grower phase. Increasing levels of PP reduced (P < 0.05) the growth performance, Ca and P utilization of birds but had no effect on the tibia ash in the starter phase and grower phases. Phytase supplementation improved (P < 0.05) the growth performance, AID and TTR of nutrients, and tibia ash of birds in the starter and grower phases. In conclusion, increasing PP levels reduced some responses of birds in the starter and grower phase while PhyG inclusion improved all responses of broiler chickens at both phases.<br>The time effects of phytase on the P utilization of growing and finishing pigs was investigated in the 5th and 6th studies, respectively using growth performance, apparent total tract digestibility (ATTD) of nutrients, P excretion, and plasma mineral concentrations as evaluation parameters. In both studies (Exp 1 and 2), treatments were arranged as a 3 × 4 factorial in a randomized complete block design with 3 corn-SBM based diets including a P-adequate PC, a low-P NC, and NC + 1,000 FYT/kg; and 4 sampling time points at days 7, 14, 21, and 28 in Exp 1 and days 14, 26, 42, and 55 in Exp 2. Ninety-six growing pigs were used in both trials with an average BW of 19.8 ± 1.16 kg in Exp 1 and 49.8 ± 3.21 kg in Exp 2. Each treatment had 8 replicates evenly divided between barrows and gilts, and 4 pigs per pen. There was an interaction (P < 0.01) between time and diet on some growth performance parameters in pigs in Exp 1 but none in Exp 2. Pigs fed the PC had greater (P < 0.05) growth performance and ATTD of nutrients as compared to pigs fed the NC in both trials. Phytase supplementation improved (P < 0.05) the ATTD of P and Ca in pigs as compared with pigs fed the NC. There was an interaction (P < 0.05) between time and diet on the total and water-soluble P lost from pigs in Exp 1. Supplementing the NC with phytase reduced the water-soluble P by 45, 32, and 35 % over the growing, finishing and the entire grow-finish period, respectively. In Exp 2, plasma concentrations of P were increased (P < 0.05) over time. In conclusion, phytase improved the responses of growing pigs however, some of these responses were influenced over time.<br>In summary, the AID and SID of P in corn, SBM, and canola meal are additive in complete diets with or without the inclusion of phytase. The BEL of P could be affected by the age of birds. A new consensus phytase variant seems to be efficient in improving the productivity of broiler chickens regardless of the presence of varying concentrations of PP and the growth phase of the birds. Phytase supplementation improves the P utilization and reduces the P loss of growing and finishing pigs however, this may be influenced by time within each growth phase.<br><br>