Kikuyu pasture was fertilized at low and high levels of nitrogen (N), namely 50 and 200 kg N/ha, after mowing and clearing the plots, to induce low and high levels of N in the herbage. The subsequent growth was harvested at 20-, 30- and 40-d re-growth. These treatments were conducted in spring, summer and autumn. Treatments included level of N, stage of re-growth and season as variables in digestion trials using sheep and voluntary feed intake (VFI) trials using long yearling heifers in pens equipped with Calan gates. Nitrogen fertilization level had no impact on herbage dry matter digestibility (DMD). Stage of re-growth influenced digestibility in the spring and summer, the highest values recorded in the 30-d treatment. However, in the autumn, the 20-d re-growth recorded the greatest digestibility. Digestibility declined as the season progressed. Digestibility was not correlated to any of the chemical fractions measured in the herbage, including in vitro DM digestibility (IVDMD). Voluntary feed intake (VFI) followed a similar trend to digestibility, with peak values recorded for the 30-d treatment in the spring and summer, while the 20-d material induced the greatest intake in the autumn. Nitrogen fertilization had a negative impact on VFI over all seasons. Similarly to digestibility, VFI was not correlated to any of the chemical fractions measured, but was correlated to digestibility and moisture concentration of the herbage. Nitrogen degradability was determined using the in situ bag technique. Differences (p<0.05) were recorded for the quickly degradable N (a) and potentially degradable N (b) fractions within season, but not for the degradation rate of the slowly degraded fraction (c) per hour. The effective degradability (dg) was not influenced by N fertilization level in the spring, while N fertilization increased the dg values in the summer and autumn. Stage of re-growth exerted a positive effect (P<0.05) on the dg values. Rumen pH, rumen ammonia and blood urea nitrogen (BUN) levels were measured in rumen fistulated sheep. Rumen pH increased also with increasing level of N fertilization and declined with advancing stage of herbage re-growth in the autumn. Rumen ammonia increased with time of sampling post feeding to 4 hrs and then tended to decline by 6 hrs. Nitrogen fertilization level influenced rumen ammonia levels (p<0.05), with the low N level producing the lowest rumen ammonia levels. Rumen ammonia levels were highest at 20-d re-growth stage in summer and at the 40-d re-growth stage in autumn. DM concentration of the herbage had an inverse relationship with rumen ammonia. BUN levels were increased by high N fertilization and were positively correlated to rumen ammonia levels. Five years of digestibility data (82 digestion trials) and three years of intake trials (38 trials) data was pooled. These data, chemical composition of the herbage and the daily maximum temperatures, rainfall and evaporation recorded at and prior to the digestion and intake trials at Cedara were analysed using multiple regression techniques. Rainfall and temperature in the period of cutting and fertilization had a negative effect on digestibility, irrespective of the stage of re-growth at harvesting, 20, 30 or 40 days later, and a combination of the two proved significant, accounting for the most variance in DDM. Temperature depressed DMD by 11.4 g/kg DM per degree rise in temperature (Degrees C). Temperatures recorded during the cutting and fertilization phase were highly negatively correlated to VFI, irrespective of stage of re-growth. The DM concentration of the herbage as fed accounting for 32% of the variance in DMD, the NPN content of the herbage accounting for only 12.2% of the variance and the ash concentration of the herbage accounting for 15.9% of the variance in digestibility. Non-protein nitrogen was negatively correlated to VFI. Both DMD and VFI were highly negatively influenced by the moisture concentration of the herbage. Overall, the results of these trials demonstrated that environmental factors such as rainfall and temperature had a far greater impact on the digestibility of kikuyu herbage than the chemical composition, which had a minimal effect. Nitrogen fertilization did not influence herbage digestibility overall, but exerted a highly negative impact on voluntary intake. / Thesis (Ph.D.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Goats are found in almost every country and are an important source of protein and produce lactose-free milk. In South Africa, survival rates of goat kids are low, mainly due to malnutrition. Intensive goat production systems based on cultivated pastures were evaluated, at various stocking rates to evaluate the effects of improved nutrition on goat production. The pastures chosen to be evaluated for goat production were Pennisetum clandestinum (Kikuyu) and Secale cereale (Stooling rye). Kikuyu is one of the more important dryland summer pasture species in KwaZulu-Natal. Three stocking rates of goats on kikuyu were evaluated using ewes with kids. When analysing the period to weaning, the ewes lost weight in all stocking rate treatments and for both years. The years had a significant effect on weight loss (P<0.001; R²=95.7%) with a mean ADG of -0.0267 kg.animalˉ¹.dayˉ¹. There was a significant difference between ADGs between stocking rates, with ADGs of -0.0157, -0.026 and -0.0384 kg.animalˉ¹.dayˉ¹ at stocking rates of 30, 45 and 60 goats.haˉ¹ respectively (P<0.001; R²=95.7%). The analyses of the entire grazing period showed no significant difference in ewe ADGs between treatments, but a significant difference between the two years (P=0.03), with a mean ADG of -0.0205 kg.animalֿ¹.dayֿ¹. There was no significant difference between kid masses between treatments. There was a significant difference between kid performance between years (P<0.001; R²=21.8%). However, factors such as ewe start mass (P<0.001) and whether the kid was a singleton or a multiple (P=0.015) had an influence on kid ADG, while gender had no significant effect (P=0.446). Interpretation of the combined ewe plus kid weight revealed that the high stocking rate produced the highest total mass per hectare (P<0.001) with an overall mean of 2377 kg.haˉ¹. Kid ADG was positively correlated to ewe ADG (P=0.013; R²=5.8%) although this was not a strong relationship. Protein was negatively correlated to pasture height (P=0.036; R²=30.8%) and had a quadratic relationship with ADG (P<0.001; R²=48.4%) with maximum ADG occurring at protein levels of 26.17%. Rainfall was different between the two seasons, which affected pasture growth, with the stocking rates in the second year being too low, so the maximum stocking rate per hectare was not reached. Stooling rye is a pasture used predominantly in South Africa and is a good source of high quality winter feed. Four stocking rates were evaluated over winter, using pregnant ewes. Rainfall was not an important variable since supplementary irrigation was given and the difference in temperatures between the years was negligible. The rate of weight gain showed a similar response for both years with the level of weight gain varying significantly between years (P=0.001; R²=90.2%). The regressions for ADG on stocking rate were determined and were y=0.2340-0.00293x for 2001 (P=0.151; R²=58.0%) and y=0.1292-0.002198x for 2002 (P=0.137; R²=61.6%). Gain per hectare was determined, as were the stocking rates at which maximum gain per hectare were achieved and this was determined to be 40 goats.haֿ¹ during 2001 and 29 goats.haֿ¹ for 2002. The respective ADGs at these stocking rates were 0.1168 and 0.0633 kg.dayֿ¹ and daily gains.haֿ¹ were 4.672 and 1.898 kg.haֿ¹.dayֿ¹ respectively. Herbage analyses revealed that there were extremely high levels of protein in the pasture (33.87%) even though the pasture was not excessively fertilised. Average daily gain was negatively related to NDF levels (P=0.006; R²=38.4%). ADF levels (P<0.001; R²=48.4%) and NDF levels (P<0.001; R²=60.4%) showed a quadratic relationship with pasture age. Blood serum revealed that selenium levels in all treatments were lower than the normal range, while all other minerals were within the normal range. To maximise animal performance, the highest quality pasture should be offered to producing animals, namely growing animals. The seasonal variation between years has a large effect on the performance of goats on pastures. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

In KwaZulu-Natal the production of beef in summer from veld is a common enterprise. Many techniques are available to optimise the productivity of this enterprise, from improving the quality of the grazing resource (planted pastures) to improving the diet of animals using nutritional supplements. To gain an insight into the production potential and financial returns possible from such improvements a trial was established at the Ukulinga Research Farm during two consecutive summer growing seasons (1997-1998 and 1998-1999). The aim was to determine the optimum beef production system for the area from both veld and kikuyu pastures. To evaluate the benefits of supplying supplementary nutrition, four alternate feed supplements, namely: 1) a Standard commercially available molasses-based protein/mineral/energy supplement; 2) a Brewers grain based protein/mineral/energy supplement, and two supplements consisting of the Brewers grain ration with either; 3) Avoparcin (an additive that improves dietary energy) or 4) Bentonite (an additive that increases the bypass of protein) were compared. As stocking rate has been shown to influence the quality of the diet consumed, the kikuyu pasture was grazed at both the recommended (1.92 LSD ha¯¹) and half the recommended stocking rate for the region. In addition, a commercial hormonal implant was applied to half of the cattle in each treatment. Grazing was monitored using the falling plate disc meter to measure pasture bulk density and laboratory analyses of herbage grab samples for digestibility and crude protein percentage. Cattle were weighed on a weekly basis and their condition was scored prior to slaughter. All enterprise costs and returns were recorded to facilitate financial analyses of the five treatments. Low rainfall and high midsummer temperatures had a detrimental effect on the productivity of the grazing and hence it was difficult to optimise production in either season. In the first season, a midsummer drought decreased the quality and quantity of both veld and kikuyu, limiting mass gain during the latter part of the season. A delay in the onset of rain at the start of the second season limited the available grazing season to 121 days as opposed to 154 days, though fodder production during the season was not limited. Trends in herbage production (quality and quantity) from veld showed moderate quality (Crude protein 7.02%; digestibility 50.2%) with an average available herbage of 1670 kg DM ha¯¹. As anticipated, kikuyu had higher quality (Crude protein 10.84%; digestibility 53.5%) and available herbage (2730 kg DM ha¯¹). These results were similar to regional benchmarks. The variable rainfall highlighted both the drought tolerance of veld and the minimum water requirements of kikuyu pastures. Lighter stocking rates tended to reduce the negative impact of moisture stress on Kikuyu pastures. The best method of producing beef (averaged over two seasons) was from heavily stocked Kikuyu pastures using the Standard supplement (1107.63 kg livemass ha¯¹). Cattle grazing veld and utilising the Avoparcin supplement produced beef at a rate of 95.96 kg ha¯¹. In comparison, the unsupplemented cattle grazing Kikuyu produced 834.87 kg ha¯¹, whilst veld grazing produced 64.43 kg ha¯¹. Hormonal implants significantly (P≤0.05) improved beef production from all sources of grazing. A lack of rain limited grazing time, causing all the cattle to be marketed whilst too lean - this negatively affected live mass gain and, hence, net financial. Although improved biological production is desirable, it is important to ensure that these gains are financially sustainable. Within the trial environment, implanted cattle fed the Standard supplement and grazing Kikuyu pastures at a high stocking rate provided the highest average gross margin of R 859.59 ha¯¹. Changing to this production system from unsupplemented veld improved expected profit by R 632.58 ha¯¹ (averaged over both seasons). Further financial analyses indicated that beef purchase price had the greatest influence on the added profit from switching from the control treatment. From a scientific standpoint these data are conclusive but it is important to remember that consumer pressure and concerns can often limit the introduction of production improvements. Such is the case with both hormonal implants and antibiotic feed additives (Avoparcin) although considering the impact of such limitations is speculative and beyond the scope of this trial. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.