Protein has been identified as a major reason that people purchase a horse feed, with anecdotal explanations offered for the poor prediction of response of horses to their rations, particularly in the sport horse market. The current research identifies through hierarchical cluster analysis that the myriad of riding feeds offered on the South African market fall into only four simple categories on the basis of wet chemistry. Feeds were subjected to the in vitro gas production technique (IVGPT) described by Pell and Schofield (1993), using equine faecal inoculum. Gas profiles, corrected for control fermentation profiles in the absence of substrate, were fitted to the model described by Campos et al. (2004) to derive GP kinetics. Gas production kinetics, and information in respect of pH, degradation efficiency, lag time and apparent and true digestibilities were obtained. The feeds were tested for glycaemic response in miniature horses using the hexokinase method with deproteinization using an auto analyser (Roche Diagnostics). Blood glucose parameters of feeds (mean, peak, slope and time to peak and area under the curve) in each group were compared by analysis of variance and regression with covariates. In vivo analysis of rates of passage and digestibility using using post-prandial percentages of acid insoluble marker collection was used to study the gastrointestinal process, to indicate foregut and hindgut compartmental flow. The need to balance nitrogen levels with a proportional supply of fermentable carbohydrate contradicts widely used protein intakes in the horse. In vitro fermentation was used in an analysis of nutrient synchrony, to identify optimal fermentative capacity for utilization of horse feeds. The characteristics of horse feeds were related to requirement and were composited in an analysis of the representation of horse feeds that would best reflect optimal utilization in the horse, to produce a method of feed characterisation that would lead to the optimal prediction of response of horses to feeds offered to South African horses. / Thesis (Ph.D.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Kikuyu pasture (Pennisetum clandestinum) is potentially the most important source of roughage used to feed dairy heifers in summer in KwaZulu-Natal. It is commonly believed that on kikuyu pasture beef breed females grow at a faster rate than those from dairy breeds when no supplementation is given. Little conclusive evidence is, however, available to support this. Explanations as to why such differences may exist are also limited. Eight Hereford and eight Holstein heifers of similar age and maturity stage were used in a trial. The trial was run over a twenty week period. For the first ten weeks all the animals in the trial grazed ad libitum kikuyu pasture with no supplementation except for a mineral lick. Over this (grass only) period the two breed groups formed the two treatments. During the second ten week period of the trial all of the Holsteins and four of the Herefords were fed a restricted but equivalent amount (1 .7 kg) of a maize meal based concentrate. The use of a computerized, mobile feeding system allowed concentrate intake of individual animals to be measured. Animal height, weight and condition score readings were taken weekly over the grass only and the concentrate (final seven weeks) periods of the trial. Herbage intake and digestibility were estimated using n-alkanes as indigestible markers in two experiments conducted during the grass only and concentrate periods. The Herefords had a significantly higher ADG than the Holsteins (0.82 vs. 0.04 kg/day; P < 0.01) over the grass only period. During the concentrate period the rate of mass gain of the Holstein treatment did not differ significantly (P >0.05) from the Hereford treatment receiving concentrate. The Herefords receiving concentrate were also not significantly different (P > 0.05) in rate of mass gain from the Herefords not receiving concentrate. Rate of height gain was not significantly different (P> 0.05) between treatments over either the concentrate or the grass only periods. During the grass only period the Holsteins lost condition (0.07 condition score units per week) whilst the Herefords gained condition at an equivalent rate. The voluntary intake of concentrates was not significantly different (P > 0.05) between the Herefords and Holsteins (19.19 vs. 16.40 g/kg/L.W(liveweight) (0.75)). Regression coefficients relating level of concentrate intake to rate of mass gain were also not significant (P > 0.05) for either of the treatments receiving concentrate. The use of n-alkanes as indigestible markers showed the intake of the Holstein treatment to have an intake 55% (P < 0.0 1) higher than the Herefords (185.4 vs. 120.5 g/kg L.W(0.75)) over the first experiment where both treatments were grazing ad lib. kikuyu alone (grass only period). During the concentrate period intake of the Herefords receiving concentrate exceeded that of the Holsteins (P < 0.01) by 23% (139.1 vs. 113.1 g/kg L.W(0.75)). Review of the literature, suggests that the double alkanes technique greatly over-estimated intake. Errors in herbage sampling (accentuated by pasture rotation in the first experiment), a low daily dose of the synthetic alkane (C(32)) and incorrect estimation of the C(32) content in the daily doses are identified as possible causes of the over-estimation of intake. Faecal recoveries of the herbage n-alkanes were demonstrated to increase with increasing chain length and hence C(35) was proposed as the most reliable herbage alkane for dry matter digestibility determination. Digestibility differences between treatments estimated using the C(35) alkane were not significantly different (P > 0.05) in either the first or second experiments. The mean digestibility estimates (using the C(35) alkane) for the first and second experiments were 64.9 and 56.61 %, respectively. In conclusion, higher growth rates of Herefords on kikuyu pasture would seem to be primarily due to differences in the dry matter intake of the grazed herbage. Further work using other breeds of dairy and beef animals is required. The underlying cause of differences in dry matter intake between breeds also requires investigation. / Thesis (M.Sc.Agric.)-University of Natal, Pietermaritzburg, 1995.

This study was conducted to investigate the effects of varying levels of dietary lysine and feed allocation, on the performance of female broiler breeders. In trial 1, 900 Cobb breeders from 26 to 45 weeks of age were used. The first four treatments had a fixed level of lysine throughout the experimental period, with 1200, 1070, 930 and 800 mg Lysine/bird/day and the last two treatments had their levels of lysine changed every two weeks, with treatment five started off with 1200 mg lysine/bird/day followed by a gradual decrease up to 975 mg lysine/bird/day at 45 week old, while treatment six started with the lowest level of lysine, 800 mg/bird/day and at 45 week old the intake was 1025 mg/bird/day. The rations provided 1900KJ ME/ day, the birds received 160 g of feed/day. Dietary lysine did not affect body weight, egg production, or egg composition. There were no significant differences in age at 50%, or peak production. Birds receiving 1070 and 1025 mg lysine/bird.day had a slightly, but not significantly, higher production in the current study. Birds receiving 1200 mg lysine/bird.day had the highest body weight and the lowest egg production. In trial 2, 900 broiler breeder hens were used. Protein intake and feed allocation were changed for each treatment at 26, 38 and 50 weeks and ending at 60 weeks. Birds on T1 were fed a constant CP content (145 g protein/kg) but a decreasing feed allocation (175 to 145 g/d). Those on T2 had a constant feed allocation (160 g/d) and a decreasing CP (166 to 124 g/kg) while those on T3 had varying levels of protein (166, 124 and 166 g/kg) and feed allocation (160, 160, 145 g/d). Mean cumulative protein intakes were 5.2, 5.3 and 4.8 kg/bird and mean energy intakes were 417, 412 and 402 MJ/bird for T1, T2 and T3 respectively. Body weights differed significantly at the end of the trial (P<0.05) with T2 showing the highest weight gain. However, egg production, egg weight and egg output were not affected by treatment. These breeders did not benefit from the additional protein and energy provided in the first and second periods by T1 and T2 (vs. T3), nor did they benefit from the additional energy provided in the final ten weeks of production by T2. / M.Sc.Agric. University of KwaZulu-Natal, Pietermaritzburg 2013.

Physicochemical properties of different fibrous ingredients were used to determine the influence of feed bulk on voluntary feed intake and gut capacity in weaner and finishing pigs. Physicochemical measures of bulkiness determined on feed ingredients were DM, crude protein (CP), ether extract, ash, water holding capacity (WHC), bulk density, crude fibre (CF), neutral detergent fibre (NDF) and acid detergent fibre (ADF). Among the fibre sources, maize stover had the highest WHC, followed by veld grass, then lucerne hay, maize cob, sunflower husks, groundnut haulms, rice bran and saw dust. The greatest bulk densities (1.4 g DM/ml) were observed in lucerne hay and saw dust, whilst sunflower husk had the lowest (0.7 g DM/ml) (P < 0.001). Rice bran, maize cob and groundnut haulms were the most fermentable fibrous ingredients (P < 0.05). Based on differences in physicochemical properties, six fibres namely lucerne hay, maize cob, maize stover, veld grass, saw dust and sunflower husk were selected and used in formulating fibrous diets fed to growing pigs based on wideness in ranges of their bulk properties. Thirty-one complete diets were formulated by dilution of a conventional weaner feed with increment levels of each fibre source at 0, 80, 160, 240, 320 and 400 g/kg. Each of the diets was offered ad libitum to four of 124 pigs weighing 18.1 (s.d. 1.37) kg body weight, in individual pens, for four weeks. There was a linear decrease in scaled feed intake (SFI) (P < 0.001) as bulk density of the feeds increased. There was a quadratic relationship between SFI and WHC, NDF and ADF, respectively, whereby SFI increased up to a point when it reached its maximum and then started to decrease as bulkiness increased (P < 0.001). By use of the broken stick model, the maximum SFI marking the gut capacity of pigs was attained when WHC = 4.5 ± 1.25 g water/g DM (P< 0.001), NDF = 367 ± 29 g/kg DM (P < 0.001) and ADF = 138 ± 77 g/kg DM (P < 0.01), respectively. The SFI decreased linearly with an increase in bulk density of the feeds (P < 0.001). Four of 84 finishing pigs in individual pens, at 65 (s.d. 1.37) kg body weight were given, ad libitum to each of 21 diets containing graded levels of lucerne, maize cobs, saw dust and sunflower husk. There was a linear decrease in SFI (P < 0.001) as WHC increased. There was a quadratic decrease in SFI as CF (P < 0.001) and NDF (P < 0.01) increased. As CP increased, there was a quadratic increase in SFI (P < 0.01). In weaner pigs, an increase in WHC, NDF, ADF and bulk density constrains feed intake, thereby providing relationships that can be used to predict gut capacity. Conversely, measurements of feed bulk cannot provide relationships with intake that can be used to predict gut capacity in finishing pigs. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg.

Physicochemical properties of fibre-based diets were used to determine the influence of feed bulk on physicochemical properties of digesta within each segment of the gastrointestinal tract and digesta in pigs. In the first experiment, three pigs (14 ± 1.2 kg body weight (BW) were allocated to each of six diets containing maize cob levels at 0, 80, 160, 240, 320 and 400 g/kg DM inclusion levels for four weeks. All pigs were fed ad libitum. They were slaughtered, eviscerated and weights of the gut compartments were recorded, then contents of digesta from each segment were sampled for the determination of water concentration, water holding capacity (WHC) and swelling capacity (SWC). The WHC of digesta in the stomach, ileum and caecum decreased (P < 0.05) with maize cob inclusion level. The SWC in the stomach decreased with the inclusion level of maize cob meal. The SWC of caecal digesta increased with maize cob inclusion (P < 0.05). Physicochemical properties of digesta increased (P < 0.05) from the stomach to ileum then decreased as the digesta moved through the hindgut. In the second experiment, four fibres namely maize cob, lucerne hay, sunflower husk and citrus pulp were used. These fibres were used in formulating diets for finishing pigs. Twenty-one complete diets were formulated by dilution of a conventional feed with increment levels of each fibre source at 0, 80, 160, 240, 320 and 400 g/kg. Each of the diets was offered ad libitum to four of 84 pigs weighing 80.8 ± 8.15 kg body weight, in individual pens, for 30 days. Stomach weights increased linearly with an increase in neutral detergent fibre (NDF) but increased with quadratic functions with an increase in SWC of the diet (P <0.05). An increase in WHC of the fibrous diets increased linearly the WHC of the proximal colon (P <0.01) at a faster rate compared to the WHC of the distal colon (P <0.001). As the SWC of the diets increased, linear increases in SWC of the digesta in the stomach (P <0.01) and caecum (P <0.001) were observed. The WHC of the digesta was negatively correlated to SWC (P < 0.001) in the stomach. Scaled feed intake (SFI) decreased linearly with an increase in SWC of the diet (P < 0.001). There was no relationship between WHC of the diet and SFI (P > 0.05). There was a linear decrease (P < 0.01) in SFI of finishing pigs as the SWC of the digesta. It can be concluded that the swelling capacity of the diets and stomach digesta in stomach are accurate predictors of scaled feed intake. Swelling capacity had great influence in the stomach weights whilst other bulking properties, such as WHC and neutral detergent fibre, affected the weight and digesta properties in the caecum, proximal and distal colon. / M.Sc.Agric. University of KwaZulu-Natal, Pietermaritzburg 2013.

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