Three lactating cows fitted with rumen cannulas and three cows fitted with proximal duodenal cannulas were used to determine the effect of in situ rumen degradation on the AA profile of rumen-undegraded protein of 12 feedstuffs. Intestinal digestibility of rumen-undegraded protein was determined using the mobile bag technique. The absorbable AA profile of rumen-undegraded protein for each feedstuff was compared with profiles of the original feedstuff and the rumen-exposed undegraded protein. Branched-chain AA in particular seemed to be rather resistant to degradation in the rumen, as was Phe. Lysine concentrations decreased in the undegraded protein fraction in 9 of 12 feedstuffs; the degradation of Met depended on the feedstuff. The absorbable AA profiles of undegraded protein, in general, closely reflected the AA profiles of the rumen-exposed residues, which suggests that rumen degradation had a greater influence than postruminal digestion on the postruminal provision of specific absorbable AA. Intestinal digestibility of undegraded protein varied from 37.8% for Eragrostis curvula hay to 98% for soybean meal; the constant digestibility factor used by most protein systems should be reconsidered.

The effect of energy and N synchronization in the rumen on microbial growth was investigated. The same daily amount of readily available energy and N sources (19 g of ruminally degradable N/kg of fermentable OM) was supplied intraruminally to sheep, according to different patterns, namely both energy and N as 12-hourly pulse-doses (fast synchronized supply), energy as 12-hourly pulse-doses and N as a continuous infusion (unsynchronized supply), energy as a continuous infusion and N as 12-hourly pulse doses (unsynchronized supply), and both energy and N as continuous infusions (slow synchronized supply). The study was done near maintenance (Exp. 1) and at a higher level of nutrition (Exp. 2). The degree of energy and N synchronization affected neither microbial flow nor efficiency of growth (P > .2 for energy x N interaction). Continuous infusion of energy resulted in a 17% (P < .05) and 14% (P = .18) higher efficiency of microbial growth than did pulse dosing in Exp. 1 and 2, respectively. This coincided with lower (P < .01) ruminal pH and higher (P < .05) ruminal lactic acid concentration for energy pulse-dose treatments. The results suggest that merely improving the degree of synchronization between energy and N release rates in the rumen does not increase microbial yield. Dietary manipulation, rather, should be aimed at first obtaining the most even ruminal energy supply pattern, and then at providing the appropriate amount of ruminally available N. Thereafter some further advantage may be gained in also ensuring a more even N supply pattern, particularly avoiding too rapid a ruminal N release.

Livestock production in South Africa contributes substantially to food security. It is also a topic of public debate because of lack of knowledge and wrong information. This article aims to provide information on the worth and impact of the livestock sector; information and statistics providing a baseline to guiding sustainability towards 2050. Seventy percent of agricultural land in South Africa can be utilized only by livestock and game and species are found in all provinces with high concentrations in the eastern higher rainfall regions. Statistics in 2010 indicate 13.6 million beef cattle, 1.4 million dairy cattle, 24.6 million sheep, 7.0 million goats, 3 million game species (farmed), 1.1 million pigs, 113 million broilers, 31.8 million layers and 1.6 million ostriches. The gross value of livestock products increased by 185% from 1995/2000 to 2006/2010. In relation to field crops and horticulture, livestock products increased their position from 42% to 47% of gross agricultural value. The main reason was a rise in the value and demand for livestock foods, particularly meat. Livestock foods contribute 27% of the consumer food basket on a weight basis. Consumption of livestock foods resembles that of developing countries with meat consumption being 50 -90 g/capita/day, milk and dairy products 120 -130 g /capita/day and eggs 15 -20 g/capita/day. Since this is the average for the country with consumption by the rich and poor often differing tenfold, consumption of livestock foods by the poor is of concern, given the many health attributes of livestock foods. The livestock sector in South Africa is a major role player in the conservation of biodiversity through a variety of welladapted indigenous and non-indigenous breeds and rare game species. It has also shown commitment to rangeland/ecosystem conservation through conservative stocking rates, with several studies and observations reporting improvement in the condition of the natural resource. The sector has always been a major employer, but employment rate has declined steadily since 2000 because of increased minimum wages, fewer commercial farmers and increased property size. Some 245 000 employees with 1.45 million dependants, in addition to dependants on communal land and emerging farms, are employed on 38 500 commercial farms and intensive units with wages amounting to R 6 100 million (South African rand). Livestock farming is the backbone of the socio-economy and provides the sustenance of most nonmetropolitan towns and rural communities. ________________________________________________________________________________

Faecal phosphorous and nitrogen can be used as indicators of the nutritive content of the veld. Dietary P concentrations can be predicted with reasonable accuracy from faecal P concentrations in faeces of caged impala rams using a simple linear regression model, Y = 0.393X (r2 = 0.97). This regression holds whether impala are grazing or browsing as well as for high and low levels of intake. The regression equation used in the prediction of dietary P in zebra, blue wildebeest and cattle, did not differ significantly from this simple regression and a combined regression equation could be formulated. A faecal P concentration of less than 2 g P/kg OM would appear to indicate a P deficiency in most species. The prediction of dietary N is influenced by the intake of phenolic compounds and different regression equations exist for grazers and browsers. For prediction of dietary N concentrations, both the concentration of N and P in the faeces should be taken into account. This multiple regression equation is applicable for grazing impala at all levels of intake. For impala utilising browse, a regression model with faecal Acid Detergent Insoluble Nitrogen (ADIN) and Acid Detergent Lignin (ADL) should be used to predict dietary N concentration. For grazers, a faecal N concentration of less than 14 g/kg DM would indicate a deficiency. Dietary digestibility can be predicted accurately in some species using faecal N, P and ADL concentrations. However, more work needs to be done to quantify their effects

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