Climate change and its effects on existence on earth are becoming more and more relevant as physical evidence of change in our climate is beginning to mount. Livestock production and our dependence on it for survival is a reality. It is also a reality that this global source of food and income will be prone to the effects of climate change. Historic climate changes have already played a role in the demise or development of agricultural production systems. This review article will give insight into the most important livestock production species and the possible effects of climate change on their production parameters. The species to be discussed are dairy cattle, beef cattle, small ruminants and monogastric production animals. The results and predictions of global studies and simulations are summarized with special emphasis, where possible, on the southern African scenario. This review deals with these changes and possible adaptations and mitigations. All predictions indicate that livestock production at local, national and regional level may undergo changes in the foreseeable future. _______________________________________________________________________________________

The purpose of this review is to define possible breeding objectives for Southern African beef cattle farmers and to review different means of expressing genetic reproductive merit. The breeding objective considered was to maximize the number of calves born or weaned for a given number of cows in a herd under prevailing environmental and management conditions. This is a complex trait that has many components. While this trait is clearly a function of the reproductive ability of each cow, it is also affected by the age structure of the herd. A number of auxiliary or index traits are used to assess this objective and their merits, shortfalls and requirements in terms of data collection are discussed. It was evident that the trait of choice was influenced by the management system. Fewer component traits can be measured and incorporated as variables in a genetic model in more extensive systems. Since South African beef cattle production systems tend to be semi-extensive or extensive, traits to consider include calving rate, calving success, calf survival, days to calving, age at first calving, calving date, calving ease and calving interval. _______________________________________________________________________________________

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Field data for the period 1976 to 1998 from South African and Namibian Afrikaner, Drakensberger, SA Angus and Simmentaler beef cattle breeds was used to investigate two fertility traits, calving rate (CR) and calving success (CS). Calving rate, a lifetime reproduction trait of the dam, was defined as number of calves produced by the dam divided by the age of the dam in years. For CS, a score of one was allocated for successful calvings and zero for failure to calve. All variances were estimated using REML procedures. The heritability estimate for CR was low (0.04) and that for CS was zero for all four breeds. After analysing CS using GFCAT (sire model) a heritability of 0.27 was estimated for the Afrikaner, suggesting that additive genetic variance does exist for CS in southern African beef cattle populations. _______________________________________________________________________________________

________________________________________________________________________________ AbstractThe utilization of non-linear threshold models and linear animal models to estimate variance components for categorical reproductive traits in beef cattle was investigated. Three traits, retention (RET), stayability (STAY) and calf tempo (CT) were defined. The data set consisted of 36 880 Afrikaner beef cattle measurements recorded over a period of 10 years. After editing, the records of 7 746 females from 473 sires were available for the genetic parameter estimation for RET. The corresponding number of records for STAY and CT were 3 018 (243 sires) and 7 653 (465 sires), respectively. Using GFCAT, sire variances for RET, STAY and CT were estimated as 0.202, 0.072 and 0.114, respectively. With error variances pre-set to one, the heritability estimates on the underlying scale were calculated as 0.67, 0.27 and 0.41 for RET, STAY and CT, respectively. From the three traits analyzed in this study CT probably reflects the true fertility of the bull's female progeny best.________________________________________________________________________________