**4. Components of beef cow efficiency**

An efficient cow herd is sexually precocious, with a high reproductive rate, low dystocia and has longevity with minimum maintenance requirements [24]. A herd's ability to reproduce in a given nutritional environment is the most important contributing factor to efficiency. Selection goals for efficiency in the cow-calf production systems include early sexual maturity

> with lean growth and minimal increase in mature weight [24]. The most efficient beef cow is therefore the one with the highest milk production that can yearly wean a calf with the

> **Figure 5.** Estimated breeding values (EBV) for reproductive traits in Bonsmara cows from 1990 to 2010 (source: ARC-API)

Effect of Bioregion on the Size and Production Efficiency of Bonsmara Cattle in Semi-Arid Parts…

http://dx.doi.org/10.5772/intechopen.72713

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Genetic trends for growth and maternal traits in the Bonsmara breed studied by [22] are shown in **Figure 4**. In this study, the genetic trends are presented for a 20 year period (1990–2010), which illustrates the consistent improvements in estimated breeding values for weaning weights (direct and maternal), 12- and 18-month weights, while estimated breeding values for birth and mature weights remained nearly constant. These improvements were obtained in well-managed cattle herds, which generally exhibit regional differentiation in mature size

Genetic trends for reproduction traits of the 20 years of Bonsmara breed data studied, are presented in **Figure 5**. Estimated breeding values for both age at first calving and inter-calving period increased since 1990–2010. It follows that the reproductive ability of cows decreased marginally during the same period during which marked progress was made in terms of growth traits, possibly since cow size still exceeded to production potential of the main beef

Reproduction and calf survival rates are the most important factors that determine the efficiency of a beef herd [10, 24]. In spite of the importance of reproduction it is generally

growth and carcass characteristics required by the market [20].

(*ICP ~ EBV of Inter-calving period; AFC ~ EBV for age at first calving*).

(e.g., optimum body size relative to bioregion, as illustrated in **Figure 1**).

cattle production regions in Southern Africa.

**5. Reproduction of extensive beef cattle**

**Figure 4.** Estimated breeding values (EBV) for growth traits in the Bonsmara cattle breed from 1990 to 2010 (source: ARC-API) (*Birth\_Dir ~ EBV for birth weight direct; Wean\_Dir ~ EBV for weaning weight direct; Wean\_Mat ~ EBV for weaning weight maternal; 12\_Month ~ EBV for 12-month weight; 18\_Month ~ EBV for 18 month weight; Mature\_weight ~ EBV for mature weight*).

Effect of Bioregion on the Size and Production Efficiency of Bonsmara Cattle in Semi-Arid Parts… http://dx.doi.org/10.5772/intechopen.72713 47

**Figure 5.** Estimated breeding values (EBV) for reproductive traits in Bonsmara cows from 1990 to 2010 (source: ARC-API) (*ICP ~ EBV of Inter-calving period; AFC ~ EBV for age at first calving*).

with lean growth and minimal increase in mature weight [24]. The most efficient beef cow is therefore the one with the highest milk production that can yearly wean a calf with the growth and carcass characteristics required by the market [20].

Genetic trends for growth and maternal traits in the Bonsmara breed studied by [22] are shown in **Figure 4**. In this study, the genetic trends are presented for a 20 year period (1990–2010), which illustrates the consistent improvements in estimated breeding values for weaning weights (direct and maternal), 12- and 18-month weights, while estimated breeding values for birth and mature weights remained nearly constant. These improvements were obtained in well-managed cattle herds, which generally exhibit regional differentiation in mature size (e.g., optimum body size relative to bioregion, as illustrated in **Figure 1**).

Genetic trends for reproduction traits of the 20 years of Bonsmara breed data studied, are presented in **Figure 5**. Estimated breeding values for both age at first calving and inter-calving period increased since 1990–2010. It follows that the reproductive ability of cows decreased marginally during the same period during which marked progress was made in terms of growth traits, possibly since cow size still exceeded to production potential of the main beef cattle production regions in Southern Africa.
