Effects of early weaning on postpartum resumption of reproduction in mother buffaloes and growth of their calves

Cu Thi Thien Thu and Nguyen Xuan Trach

Faculty of Animal Science and Aquaculture.
Hanoi University of Agriculture. Vietnam
cttthu@hua.edu.vn

Abstract

An experiment to determine the effects of early weaning on postpartum resumption of reproduction in mother buffaloes and growth of their calves was carried out concurrently in 2 localities in North Vietnam, viz. Ha Nam and Phu Tho, with different grazing conditions. In each locality, 12 buffalo-calves pairs were equally allocated into 2 groups of 6 pairs each; in one group calves were allowed to suck their mothers as long as they could according to the traditional practice (control group) and in the other group (early weaning) calves were weaned at 120 days post calving (experimental group).

Results showed that early weaning improved postpartum reproduction in the mother buffaloes, shortening the periods from calving to first estrus and to conception. Postpartum resumption of reproduction came earlier in the locality with better nutritional conditions. It was also shown that although early weaning suppressed calf growth to some extent right after weaning, the early weaned calves spent more time grazing and thus grew faster later on compared to those in the control group. 

Key words: Buffalo, calves, early weaning, growth, reproduction

Introduction

In Vietnam, almost all buffaloes belong to small-holders. After birth, the calf is allowed to follow its mother, with suckling continuing until 1-2 years old because the farmer has no way to wean the calves. That may be one of the reasons for long calving intervals in buffaloes as it has been proven that suckling causes delayed postpartum resumption of ovarian activity (Lamb et al 1997) and removal of the nursing calve results in hormonal changes in the buffalo that stimulate estrus (Short et al 1990, Lamb et al 1999). Beside hormonal changes, buffaloes must have energy to support all body activities, but some functions have a higher priority for energy use than others. Buffaloes can only direct energy toward resuming the estrous cycle after calving if energy intake exceeds the combined requirements for maintenance, growth and lactation (Rae et al 1993). This is why body condition is strongly related to the length of the postpartum anestrous period in beef cattle (Laster 1973, Houghton et al 1990). Since body condition influences reproductive performance, early weaning or restricted suckling can be utilized to improve the chance that a buffalo is in a proper body condition and thus reproduction post calving.

As far as the calf is concerned, the quantity of mother's milk in late lactation is very low and thus energy supply is not enough for calf growth. In addition, the suckling reflex inhibits the feeling of hungrer and this will lead to the result that the calves will be very thin and emaciated. At the same time, if the calf is weaned late, the rumen should develop very slowly because the main feed is mother’s milk. When the calf begins to eat dry feed, the rumen begins to supply nutrients produced by fermentation and the population of rumen bacteria begins to grow. The rumen bacteria themselves also provide an important source of protein as they are washed out of the rumen, digested, and absorbed in the small intestine. Microbial protein is highly digestible and contains a favorable profile of amino acids relative to the needs of the growing calves. This is the reason why the sooner dry feed is digested by the calves, the sooner rumen development occurs and early weaning improves cow-calf performance (Randel 1981; Peterson et al 1987).

However, the above mentioned effects of early weaning have been so far shown from studies on cattle. Therefore, the present study was undertaken to test the hypothesis that early weaning of the calves could also shorten the postpartum interval in the mother buffalo and enhance growth of the calves due to better grass intake and digestion.

Materials and methods

The study was carried out from February to August 2010 concurrently in 2 localities in North Vietnam, viz. Ha Nam and Phu Tho, with different grazing conditions. In Ha Nam natural green grass was abundantly available; whereas, in Phu Tho buffaloes were suffering from harsh grazing conditions. In each of the two localities, 12 buffalo-calf pairs were selected and equally allocated into 2 groups of 6 pairs each: Group 1 (control): Calves were allowed to suck their mothers as long as they could and follow the traditional practice.

Group 2 (early weaning): Calves were weaned at 120 days post calving, using a plastic anti-suckling device (Photo 1), and being allowed to follow their mothers to graze.

Photo 1. Anti-suckling device

In both groups, the mother buffaloes were allowed to graze natural grass along road sides and common lands together with their calves as traditionally practiced. The mother buffaloes were observed for standing oestrus twice daily since the weaning of the calves in group 2 until 210 days postpartum. Pregnancy was detected by rectal palpation at 65 to 110 days after breeding. The calves were weighed at the time of weaning (120 days of age) and every 15 days thereafter till 210 days of age.

Data were subjected to analyses of variance (ANOVA) for a 2x2 factorial model with interactions using the General Linear Model (GLM) of Minitab 16. Pair-wise comparisons of means were done using the Tukey test.

Results and discussion

Early weaning had a strong effect on the time from calving to first estrus, reducing it by 24.8 days in Phu Tho and 48.2 days in Ha Nam. Similarly, the time from calving to conception was shortened by 32.8 and 46.7 days, respectively, in the two localities as a result of early weaning.. There was an interaction between early weaning and locality, indicating that the effects of early weaning on postpartum resumption of reproduction in buffaloes would depend on the locality or, in other words, the feeding condition.

Live weight gain of the calves was strongly affected by locality, indicating the importance of grazing conditions. However, early weaning did not affect the weight gain of the calves when calculated for a long time (75 days after weaning).  Nevertheless, a closer observation on the growth pattern of the calves after weaning (Table 2) shows that early weaning influenced the growth pattern of the calves. Right after weaning average daily gain of the calves was dramatically reduced compared to those not weaned, but later on the growth rate of the early weaning calves gradually increased and reached a level higher than that of the control calves, after a certain time (one month) of weaning. This can be explained that after weaning the calves received no nutrients from the mother’s milk with a nutritionally stressful period during which they had to rely on grazing for living, resulting in retarded growth. However, when the calves overcame this stressful period, they became adapted to the new weaning living condition and resumed weight gain.  The early weaning calves grew very fast then, even faster than the control group, and as a result, they became heavier later on (Figure 1).

Figure 1: Growth pattern of buffalo calves with and without early weaning in Ha Nam

Figure 2: Daily grazing time spent by buffalo calves with and without early weaning

Figure 2 shows the changes in the calves’ grazing behaviour after weaning that can help explain the earlier mentioned changes in growth rate.  The most critical time was the time right after weaning as the calves must overcome the stress of weaning. In the first weeks of weaning, the early weaning calves spent less time grazing than the control calves. That was probably because at the beginning of weaning, the early weaning calves had to wear the anti-suckling device on their nose, which was not comfortable for the calves to graze. However, when the early weaning calves forgot suckling and the device was removed, they spent more and more time grazing to meet their nutritional demands, and from 4 weeks of weaning onwards the early weaning calves spent longer time grazing than the control calves, indicating that when relying on the mother’s milk the control calves did not feel so hungry to graze as much as the early weaning group. Since the early weaning calves consumed more grass and utilized it better their growth rate was higher than that of the control calves in the long run.

Conclusions

• Early weaning (at 120 days after calving) was an effective way to shorten postpartum resumption of reproduction in mother buffaloes and enhance growth of their calves after a short period of nutritional stress.

Acknowledgements

The authors are very grateful to the Swedish International Development Cooperation Agency, Department for Research Cooperation (Sida-SAREC), through the regional MEKARN Project, for the financial support of this study.  

References

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Received 7 December 2011; Accepted 30 December 2011; Published 4 January 2012

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