Livestock Production

The sigmoid curve is an S-shaped curve (Gardener et al., 1985), which can be used to describe the life-cycle of products, organizations, empires, and even human relationships. As the curve predicts, nearly all of life's endeavors start slowly. The growth curve progresses to an exponential stage before rising to its maximum, after which there is decline (Handy, 1994). The sigmoid curve can be divided into three typical steps: slow-rapid-slow growth stages, or early-middle-late growth stages. The middle growth stage is also called the grand growth period. The time frame may vary from minutes to years depending on the selected organism or organ, but the S-shaped accumulation pattern (Figure 2) typifies every single individual including human beings, every single organ, and even every single cell (Gardener et al., 1985). The growth curve provides us an insight and opportunity to set up our production strategy and planning. For grain production, there is only one grand growth period with early and late growth stages. However, for vegetative production, there can be more than one grand growth period. For example, vegetative growth may contain a short early growth stage with or without a late growth stage.

Vegetative production has two objectives: to produce forage for herbivore consumption; and to produce livestock with its attendant products. During livestock production, the herbivorous animals convert plant crude protein and other constituents into livestock products such as meats and woolen goods. Accordingly, the late plant growth stage should be avoided because lignin (Table 3) is formed during this stage, reducing conversion efficiency from forage to livestock products. During the grand growth period, plants may have more than 7fold greater photosynthesis efficiency (Jiang et al., 1994). Greater efficiency translates into better and more forage with the potential for conversion into additional livestock products. Based upon the literature, forage crops should be grazed or cut just before or at the flowering stage (Table 3) to avoid the late growth stage and reduce or control lignin content in the forage. Accordingly, one or two more grand growth periods can be gained in the growth season (Table 2) because grain production had only one grand growth period but vegetative production could be harvested two to three times. Every harvest could have one grand growth period. Every increase in number of harvest times could increase one grand growth period for forage production.

Vegetative production is a coupled system linking plant and livestock production. The S-shaped curve is also very important in livestock production for efficient bioconversion from forage to livestock products because the growth of herbivore may also follow a similar function. For example, research results conducted in Inner Mongolia showed that lamb yield per sheep was 13.8, 21.8, 25.8, and 27.6 kg for slaughtering at ages of 10, 24, 48, and 60 months, respectively. The yield at age of 60 months was just as much as two-fold that at age of 10 months. The corresponding feed consumption for the 60 months was as much as 11.2 times that of the 10 months. This observation indicated that the efficiency of the feed conversion of the lambs at 10 months was 4.6 times greater than that of lambs at 60 months. Thus, butchery of 10-month-old lambs can maximize economic return, assuming demand for products from the younger lambs is equivalent to that of 60-month lambs. However, local herdsmen desire to have the maximum lamb yield per sheep because they are not familiar with the S-shaped growth curve; and traditionally the maximum weight yield provides the great feeling of success. In this case, traditional practices led to uneconomical returns, despite the apparent belief that the herdsmen were successfully producing lamb products.

Time (day)

Figure 2. Growth curve of leaves of pinto bean (Ting, 1982).

Time (day)

Figure 2. Growth curve of leaves of pinto bean (Ting, 1982).

Table 3. Changes in components (%) of ryegrass (Lolium L.) at different stages

Crude Crude Mineral Nitrogen-free Crude Lignin protein fat extract fiber

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