Citation of this paper |
The effect of Temporary Interruption of Suckling (TIS) on weight change at 24 and 45 days after treatment, and at weaning, in Zebu calves was evaluated. The experiment was repeated up to 3 times, depending on the occurrence of heat in the dams. The treatments were: TIS in a silvopastoral system of A. mangium and B. humidicola plus supplementation with Cratylia. argentea and cottonseed (TIS-S); TIS in B. humidicola without trees and no supplementation (TIS); and no TIS, in B. humidicola without supplementation (CTL).
The calves subjected to TIS in the traditional grazing system (without supplementation and grazing a monoculture of Brachiaria humidicula) were 24 kg lighter at weaning than those in the improved management system (TIS-S) with supplementation and a sylvopastoral grazing system. Calves in this latter treatment appeared to be slightly heavier at weaning than those in the control group not subjected to TIS. Similar trends were seen in the weight gains of the calves between the beginning of the first and the end of the third TIS, and from the beginning of the first TIS to weaning.
The results suggest that TIS can be practiced without affecting the weight gain of the calves, provided an improved management system is employed, such as silvopastoral grazing plus supplementation.
Various strategies of reproductive management have been implemented with the aim of reducing the period of open days in beef cattle production systems. Included among these is temporary interruption of suckling (TIS). However, the calves subjected to this practice suffer considerable stress during the interruption and this results in a reduction in the average daily weight gain until weaning compared with control animals not subjected to TIS (Browning et al 1994; Prieto et al 1997; González 2000). Although the reproductive effect on the dam is generally positive, the deleterious effect on the calf has limited the adoption of this practice by cattle producers. Nevertheless the implementation of temporary interruption of suckling, accompanied by adequate supplementation for the calves and provision of shade, as in a silvopastoral system, could be a viable alternative to improve the reproductive performance of the dams without altering the weight gain capacity of the calves.
This hypothesis was studied in an experiment with Zebu dams and their calves in a silvopastoral system of Acacia mangium and Brachiaria humidícola, with forage supplementation of Cratylia argentea.
Acacia mangium is a leguminous tree originating in Australia and its use for timber as well as for shade is gaining popularity in Colombia, especially on the acidic and aluminiferous soils. Cratylia argentea is a bushy leguminous shrub originating from the Amazon region and is also well adapted to acidic and aluminiferous soils.
This study was carried out at La Candelaria Ranch of the University of Antioquia, dedicated to raising Zebu cattle and located in north-western Colombia between 8°0' north latitude and 76º 12' west longitude. The ranch is situated at an elevation of 50 m above the sea level, with average temperature of 28°C, annual rainfall of 2382 mm and relative humidity of 75%. This ecological zone is categorized as tropical rain forest. The soils are acidic, with low availability of phosphorous and high concentrations of exchangeable aluminium. The predominant pasture was Brachiaria humidicola. The experiments were carried out during the months of October, November and December, that coincide with the end of the rainy season and the beginning of the dry season.
Calves were separated from their mothers and confined for 72 hours. If the cow came in heat the treatment was terminated. Otherwise, the procedure was repeated up to two more times at 21 day intervals, simulating the estrous cycles.
The treatments were:
TIS-S: TIS and grazing in a sylvopastoral system of Acacia mangium and Brachiaria humidicola with ad libitum supplementation with chopped fresh foliage of Cratylia argentea (a small quantity of molasses diluted with water was spread over the foliage to stimulate intake. The calves also received 1 kg/animal/day of cottonseeds. There were nine calves and their dams during the first TIS, seven during the second TIS and five in the third TIS.
TIS: TIS and grazing on Brachiaria humidicola. This treatment followed the traditional management system in which temporary interruption of suckling is carried out in Zebu cattle in the Colombian lowlands (without supplementation and with no trees). Nine calves were evaluated in the first TIS, 6 in the second and 5 in the third.
CTL: The calves remained with their dams (no TIS) and grazing was on Brachiaria humidicola. There were 14 calves in this treatment.
On all treatments, the animals had free access to water and mineralized salt. During the 3 days of each TIS the calves were in an adjacent grazing area of B. humidicola with no trees or supplementation.
The calves were weighed at the beginning of the each TIS, at the end of the last TIS and at weaning. The variables that were analysed were:
Weight change between the first and the second TIS (24-day-interval), and between the first and third TIS (45-day-interval).
Consumption of Cratylia argentea and cottonseed (amount offered minus the leftover, divided by the number of animals)..
Weight changes in the calves during 24 days and 45 days, after first TIS, and at weaning were analyzed using a probabilistic experimental model of classification with multiple variables using the SAS statistical package. The variables were transformed using the Box-Cox model. The differences among the treatments were analyzed using Tukey's statistical test.
The calves subjected to TIS in the traditional grazing system (without supplementation and grazing a monoculture of Brachiaria humidicula) were 24 kg lighter at weaning than those in the improved management system (TIS-S) with supplementation and a sylvopastoral grazing system (Table 1). Calves in this latter treatment appeared to be slightly heavier at weaning than those in the control group not subjected to TIS. Similar trends were seen in the weight gains of the calves between the beginning of the first and the end of the third TIS, and from the beginning of the first TIS to weaning.
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Table 1. Mean values for changes in liveweight (kg) of the calves |
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Treatments |
TIS-S |
TIS |
CTL# |
|
Number of animals (n) |
7 |
6 |
14 |
|
Weight at the beginning of the first TIS |
105 ± 9.58 |
109±10.7 |
104 ±10.4 |
|
Weight at the end of the second TIS |
120+9.82 |
119+12.1 |
121+9.7 |
|
Weight gain between first and second TIS |
0.628 ± 0.056 ab |
0.428 ± 0.062 b |
0.700 ± 0.055 a |
|
Number of animals (n) |
5 |
5 |
14 |
|
Weight gain between first and third TIS |
0.628 ± 0.056 ab |
0.428 ± 0.062 b |
0.700 ± 0.055 a |
|
Number of animals (n) |
9 |
9 |
14 |
|
Weight at weaning |
191+13.7a |
167+11.7 b |
178+12.5 a |
|
Weight gain from first TIS to weaning |
0.565 ± 0.056 a |
0.401 ± 0.062 b |
0.487 ± 0.055 a |
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abc Means in the same row without common letter are different at P< 0.05. # Calves in this group were weighed on the same days as those subjected to TIS |
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The consumption of Cratylia argentea by the TIS-S calves during the three TIS periods ranged from 500 to 1000 g/animal/day (Table 2). Cottonseed consumption was 102 g/animal/day. The calves were observed to browse on the Acacia mangium trees.
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Table 2. Consumption of Cratylia argentea by calves in TIS-S during each TIS |
|
|
|
Consumption fresh
foliage |
|
1st TIS |
0.597 |
|
2nd TIS |
1.070 |
|
3rd TIS |
0.790 |
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Table 3. Composition (on DM basis except for DM which is on fresh basis) of the forages (leaves only of Cratylia and A. mangium; leaves plus stems of Brachiaria) available to the animals. |
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Forages |
DM |
N*6.25 |
NDF (%) |
ADF (%) |
Ca |
P |
|
Brachiaria humidicola in silvopastoral system |
26 |
5 |
75.3 |
43.5 |
0.09 |
0.1 |
|
Brachiaria humidícola in tree-less pastures |
27 |
3 |
75.8 |
44.2 |
0.12 |
0.09 |
|
Cratylia argentea 1 |
23 |
17 |
54 |
39 |
0.43 |
0.27 |
|
Acacia mangium |
29 |
10.6 |
49.4 |
45.9 |
0.83 |
0.10 |
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1 The leaves were harvested at six months of age |
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TIS as a method to reduce the number of open days in beef cows, in the tropics, has not been very popular among farmers since they believe that this treatment decreases the weight gain of the calves, and this is generally true but there may be alternatives to improve this situation. This study is an effort to find such alternatives under very hot, lowland tropical conditions in a search for ecologically and economically sustainable cattle production.
The results of this study indicate that there are means to ameliorate the weight losses experimented by calves during TIS. A combination of a silvopastoral system and supplementation resulted in weaning weights that were not significantly different from the control animals not subjected to TIS. In contrast, the calves subjected to TIS, but without silvopastoral conditions and supplementation, were 24 kg lighter at weaning.
The greater comfort of cattle in sylvopastoral systems of Acacia mangium and Brachiaria humidicola. compared with pasture without trees, has been reported by Escobar et al (2001). They found that rectal temperatures, as well as the respiratory rates, were higher in the cows in the pastures without trees, and their grass intake was lower. Pezo et al (1992) also attribute the greater comfort in the sylvopastoral systems to the effect of the shade that helps to maintain a more stable temperature, to the tree barriers that decrease the effect of the wind, and to the improvement in the quality of the diet. Similarly, Ruiz and Febles (1998), in an observational study at the Institute of Animal Science of Cuba, found that there was an increase in milk production in cows grazing pastures containing shade trees.
Cratylia argentea has only
recently been introduced as a forage source for cattle. Holmann et
al (1999) indicated that C. argentea was an effective supplement;
given either fresh or as
silage, to partially replace commercial concentrates.
Acacia mangium is thought to be of limited value as a source of edible
biomass in view of the relatively low rates of rumen degradability of the leaves
(DM degradability of less than 30% after 48h incubation in the rumen according
to Bui Xuan An et al 1992a). There are reports of the foliage being fed to
goats (Nguyen Thi Duyen et al 1996) as well
as to cattle (Bui Xuan An et al 1992b) but the results were inconclusive.
In the present study, the calves in the TIS-S treatment were observed to
browse on this tree but it was not possible to quantify its possible
contribution to their diet.
Under the condition of the present study, it is concluded that a combination of a sylvopastoral system and supplementation with legume foliage and small amounts of cottonseed is a means of compensating for the negative effects of temporary interrupted suckling on calf growth rate.
The authors wish to express their appreciation to Mr J Arroyave, Administrator of La Candelaria Ranch; to the " Departamento Académico de las Haciendas" for their support in carrying out this investigation; and to the workers on the ranch for their valuable collaboration in the development of this study. This project was financed by the "Departmento de Haciendas, CODI y de Fisiología y Biotecnología de la Reproducción" of the University of Antioquia:
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Received 16 July 2003; Accepted 7 January 2004