| Livestock Research for Rural Development 9 (4) 1997 | Citation of this paper |
National Institute of Animal Husbandry, Hanoi, Vietnam
* Finca Ecologica, University of Agriculture and Forestry, Ho Chi Minh City, Vietnam
Twenty four crossbred F1 cows (Friesian x Local) with their newborn calves were used in an experiment to evaluate the effects of restricted suckling (RS) on growth rate of the calves and milk yield and reproductive rate of the cows compared to artificial rearing (AR). The animals were randomly divided into two groups: RS and AR according to calving date. Cows and calves in both groups were kept under the same conditions. Calves under AR treatment were removed from their dams 3 days after calving and fed milk from buckets. Calves under RS treatment were allowed to suckle their dams twice daily for 30 minutes after milking.
The average daily weight gain of the RS calves was higher (P<0.05) than that of AR calves (445 vs 422 g/day). Milk conversion per kilogram weight gain was 4.2 kg for RS calves and 4.7 kg for AR calves. Average total milk yield of RS cows was 15% higher (P<0.05) than that of AR cows (10.9 vs 9.5 kg/day). Saleable milk of RS cows was 20% higher (P<0.01) than that of AR cows (9.0 vs 7.5 kg/day). There was no difference in postpartum interval to first oestrus (111 days for RS cows and 108 days for AR cows). Twenty five percent of the cows in AR treatment had mastitis while no cases were observed in the RS cows.
Restricted suckling is considered to be a more appropriate system than calf removal and artificial rearing for managing cows and calves and can be recommended especially for small-scale farmers.
Cattle in tropical developing countries are mainly Bos indicus and milk production is frequently based on dual purpose, or even triple purpose management, where the cows are also used for draught as well as meat production (Preston and Murgeitio 1992).
There are different ways of rearing calves, such as suckling ad libitum, different regimes of restricted suckling (RS) and artificial rearing (AR). Artificial rearing systems have been applied largely in industrialized countries. Calves are removed from their dams and cows are milked by machine, and then the calves are bucket fed with milk from their dams or with a milk replacer. This system is frequently inappropriate under the conditions of feeding and management in most developing countries (Preston 1984). In addition, no matter how efficiently a cow is machine-milked, there is always residual milk left in the udder which cannot be utilized. This can be as much as 15% to 25% of the total milk (Ugarte 1977). The incidence of mastitis and calf mortality is often higher under the AR system than under RS (Ugarte and Preston 1975; Knowles and Edwards 1983).
The restricted suckling system allows the calves to suckle their dams for a limited period after milking and the calves also use residual milk in the udder of the cows, which is milk not utilized in the AR system. According to a number of investigators (Ugarte and Preston 1972a,b; Alvarez et al 1980; Knowles and Edwards 1983), RS increases growth rate of the calf, milk yield and saleable milk of the cow, while reducing the incidence of mastitis and has little or no negative effect on reproduction compared to AR.
Restricted suckling also appears to stimulate the cow's milk production and may increase the total amount of milk produced by the cow. Restricted suckling is often a more viable option than AR, as it reduces labor requirements, capital outlay and calf mortality (Preston and Leng 1987).
This experiment was undertaken to evaluate the effects of RS compared with AR on the
growth rate of calves, milk yield and reproductive rate of crossbred F1 (Friesian*Local)
cows. The objective was also to determine which of the two calf rearing systems could best
be applied in conditions of smallholder farming.
The experiment was carried out at Caudien state farm which is situated in the suburbs of Hanoi with an annual rainfall of approximately 2000 mm, falling mainly from June to October, and an average annual temperature of 25C.
The experiment was conducted for two years. It was started in June1995 and lasted until the end of December 1996.
Twenty four crossbred F1 cows (Holstein*Chinese Yellow) with newborn calves were used in the experiment. They calved in the period from June, 1995 to June, 1996.
The animals were distributed to two treatments:
Allocation of cows and calves to treatments was in blocks of two according to calving date and with the following procedure. The first cow to calve was allocated to treatment AR and the next to RS, the next calving cow and calf were allocated to treatment AR and so on.
During the experimental period all cows were kept in the house and fed the same basal diet of cut green grass, hay or silage given ad libitum. Cows were fed 5 kg/day of a concentrate mixture (rice bran, cassava meal and minerals). The concentrate was given at the time of milking. The cows were milked twice a day (6 am and 4 pm) and milk yield was recorded daily. Oestrous of the cows was detected daily in the morning, afternoon and evening by visual observation of oestrous signs. Cows showing oestrous were mated artificially at the point of standing oestrous.
Calves in the AR groups were kept with their dams until three days of age. On the fourth day, cows and calves were separated and cows were milked by hand. Calves were kept in pens which contained an area of shelter, feeding and water troughs and a simple design for individual bucket feeding of milk through the wooden fence surrounding each enclosure. Calves were weaned at 6 months of age. During the six months before weaning, each calf was fed a total of 360 kg milk in declining amounts. Milk was given twice daily (morning and evening). Also, each calf was fed a total of 200 kg concentrate in increasing amounts. In addition, calves received green grass and water ad libitum throughout the experiment.
Calves in the RS group were also separated from their dams three days after calving, when milking of the cows began. Cows were then milked by hand. After each milking, calves suckled their dams for 30 minutes. After suckling, calves were separated from their dams and kept in pens similar to the pens of AR calves. They were given the same amount of concentrates as the calves in AR groups (200 kg during 6 months in increasing amounts) and given free access to green grass and water throughout the experiment. The calves were weaned at 6 months of age.
Milk yield was recorded daily. Body weight of cows and calves at calving was recorded and subsequently they were weighed every month throughout the experiment. Cow and calf health was monitored by recording any diseases and subsequent treatments given to the animals during the experiment.
Analysis of milk composition (protein and fat content) was done every month. Nitrogen content was analyzed by the Kjeldahl method and fat content was analyzed by the Gerber method, following the procedure of Richardson (1985). The amount of milk consumed by the calves in the restricted suckling groups (weighed before and after suckling) was determined every month. Samples of suckled milk were taken at monthly intervals. This was done by interrupting the suckling process about 5 minutes after suckling began and drawing by hand a small amountof milk into a container. These samples were analyzed for protein (N*6.25) and fat content.
The data were analyzed using the General Linear Model in Minitab statistical software version 8.2 (Minitab Inc.,7081 Enterprise Drive, State College, PA 1680-7008, USA). The analysis of variance was done for all production parameters. Differences in composition of milk due to suckling, in cows on the RS treatment, were analysed by "t" test.
| Table 1: Mean values of weight gain and milk conversion of the calves | |||
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| Restricted suckling | Artificial rearing | SE/Prob | |
| Birth weight (kg) | 29.0 | 29.2 | 0.40/0.70 |
| Weight at 6 months (kg) | 109.2 | 105.3 | 1.44/0.07 |
| Daily gain (g) | 445.4 | 422.1 | 7.9/0.05 |
| Milk intake (kg/day) | 1.9 | 2.0 | |
| Milk conversion (kg milk/kg live weight gain) | 4.2 | 4.7 | |
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Mean values for growth rate of the calves are in Table 1. For birth weight of the calves, there was no significant difference between the management systems. Body weight at 6 months of age tended (P=0.07) to be higher for RS calves than for AR calves. Average daily weight gain from birth to 6 months for RS calves (445 g/d) was higher (P=0.05) than for AR calves. Mean milk conversion per kg weight gain was better for the RS calves.
Data for milk yield and milk consumed by the calves are in Table 2.
| Table 2: Mean values of daily milk yield and saleable milk of the cows and amounts taken by the calf (kg) | |||
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| Restricted suckling | Artificial rearing | SE/Prob | |
| Milk yield at milking time (kg/d) | 9.0 | 9.5 | 0.55/0.54 |
| Milk consumed by calf (kg/d) | 1.9 | 2.0 | |
| Total milk yield (kg/d) | 10.9 | 9.5 | |
| Saleable milk (kg/d) | 9.0 | 7.5 | |
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Milk produced at milking was similar for both treatments (P=0.54). However, total milk production was 15% higher for RS cows and milk available for sale was 20% higher for the RS treatment.
There was no difference between treatments in change of live weight postpartum (Table 3).
| Table 3: Change in live weight postpartum (kg) of the cows | |||
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| Restricted suckling | Artificial rearing | SE/Prob | |
| Body weight, kg | |||
| At calving | 429.3 | 440.6 | 5.7/0.18 |
| At 6 months | 426.8 | 437.0 | 4.63/0.14 |
| Difference | -2.5 | -3.6 | 3.1/0.79 |
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There were no significant differences due to treatment in protein and fat content of milk taken at milking (Table 4). However, values for fat and protein were significantly higher in suckled milk compared with that taken at milking from the same cows (P=0.001 and P=0.02, for fat and protein, respectively)(Table 5).
| Table 4: Mean values of protein and fat content of milk taken at milking | |||
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| Composition (%) | Restricted suckling | Artificial rearing | SE/Prob |
| Protein content | 3.53 | 3.53 | |
| Fat content | 3.82 | 3.83 | |
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| Table 5: Composition of milk sucked by calf compared with milk taken at milking | ||||
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| Composition (%) | At milking | Sucked by calf | Difference | SE/Prob |
| Fat | 3.83 | 5.89 | 2.06 | 0.06/0.001 |
| Protein | 3.53 | 3.64 | 0.11 | 0.041/0.02 |
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The data in Table 6 show that there was no effect of treatment on postpartum interval to first oestrous. There were no cases of mastitis in the RS cows but 25% of the cows were affected in the AR treatment.
| Table 6: Mean values for days postpartum to oestrous and mastitis incidence of the cows | ||
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| Restricted suckling | Artificial rearing | |
| Postpartum to first oestrous (days) | 110.5 | 107.5 |
| Mastitis incidence (cows affected) | 0/12 | 3/12 |
| Mastitis rate (%) | 0 | 25 |
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Higher rates of weight gain and better milk conversion per unit weight gain of the RS calves in the present study could be related to the higher fat content in the milk consumed by those calves compared to the milk consumed by AR calves and also to the advantages for the digestive tract of young calves when they suck directly and slowly from their dam. When calves are suckled naturally, milk is channeled by the reticular groove reflex directly to the abomasum, which is the true stomach of a newborn calf. Both the energy and protein are utilized with considerably greater efficiency than if some of the milk passes first to the rumen. When drinking milk from a bucket (eg: in AR calvs) , it is probable that a part of the milk enters the rumen.
Alvarez et al (1980), working with crossbred European/Zebu cows, showed that RS calves had growth rates higher than calves reared with the AR system (446 g/day vs 277 g/day). Little et al (1991) studied the influence of RS in crossbred dairy cows (Friesian X Boran) and showed that RS increased calf growth rate to weaning by 0.22 kg per day. Gonzalez et al (1984) found that in Friesian calves the daily weight gain was 440 and 598 g for AR and RS calves. Carias and Vaccaro (1984) studied the two systems of calf rearing in Holstein-Friesian and Brown Swiss cattle and observed that the restricted suckling system produced heavier (P<0.05) weight gains than the bucket system (0.677 vs 0.555 kg/day).
Alvarez et al (1980) and Velazco et al (1983) demonstrated that growth rates of calves and conversion of milk into live weight gain were improved when calves were reared by RS rather than with milk from a bucket. Knowles and Edwards (1983) compared the effects of the RS and AR systems on dam and calf performance and showed that with the RS system, growth rate of the calf was 34% higher, while milk consumed for one kg of weight gain was 22.5% less during 70 days. These results are also similar to data reported by Ugarte (1978).
Milk yield in RS cows was higher than in AR cows, which confirms the high efficiency of utilization of the cows' milk potential when milking is combined with suckling (Ugarte and Preston 1973). After milking, RS calves were suckled for 30 minutes, and got residual milk which is not utilized in the AR system. Another reason is that when the calves are suckled by their mother, the brain of the dam is stimulated and oxytocin continues to be secreted and affects the milk ejection. Paredes et al (1981), Alvarez et al (1980), Ugarte and Preston (1972a, 1975) and Gaya et al (1977) studied the effects of RS on milk yield of cows and showed that compared with AR methods, RS prolonged the lactation and increased the milk yield. Velazco et al (1982) showed that Holstein cows in Venezuela, milked by machine and with restricted suckling of their own calves after milking, gave more milk and lost less body weight after calving than cows whose calves were removed after three days and reared artificially. Little et al (1991) showed that milk yield was 15% higher for RS cows compared with those whose calves were artificially reared. Knowles and Edwards (1983) also compared the RS and AR systems and reported that milk yield was higher (2615 litres vs 1960 litres in 305 days of lactation, respectively), and saleable milk was 69% higher in the RS system. Teeluck et al (1981) studied Creole and Creole X Friesian cows and showed that compared to AR cows, RS cows had higher total daily milk yields (6.37 vs 8.55 kg) and saleable milk (3.06 vs 6.39 kg). Ugarte and Preston (1973) found that the average increase in milk secretion attributed to suckling was 31% in RS systems.
Milk consumed by restricted suckled calves in this study was 17% of total milk. Ugarte (1977) reported that there is always residual milk left in the udder which cannot be taken out by milking but is utilized by the calf that is suckled after milking. In his study this was 21% of the total milk.
There were no significant differences between treatments in change of liveweight of the cows. Similar results, reported by Gaya et al (1977), showed that there were no significant differences between RS and AR in live weight changes of the cows. Ugarte and Preston (1975) reported that live weight of dams changed from birth to weaning of calves (at 70 days), with a decrease of 17 kg for RS cows and an increase of 2.8 kg for AR cows.
Protein and fat content of the normal milk from RS cows was similar to AR cows. Fat content in the residual milk, which was sucked by calves, was much higher than that in normal milk. It is one of the important reasons explaining the higher growth rate of the calves reared in the RS system, although they consumed less milk compared to calves reared in the AR system. In the study by Ugarte (1977), similar results were obtained showing that fat content in normal milk with machine milking was 2.8% while the last stripping milk had 5.7% fat. These results are in agreement with data published by Topel (1976).
There were no differences between treatments in the interval postpartum to first oestrous. Little et al (1991) found that RS delayed return to oestrous (101 vs 41 days), but required fewer services per conception (1.3 vs 1.9). However, Alvarez et al (1980) studied the effects of RS and AR on time to first oestrous and calving interval of the dam and showed that RS had no or little effect on reproductive rate. Veitia and Simon (1972) studied F1 Holstein X Brahman cows and reported that there were no differences in time from calving to first oestrous for RS and AR cows (84 and 81 days respectively). Ugarte and Preston (1975) worked with Holstein cows and observed that the postpartum interval from calving to first oestrous was 89.6 and 88.5 days for RS and AR cows. A study by Leon and Vaccaro (1984) even showed that RS twice daily decreased the calving interval and services per conception, while milk yield of the cows and growth rate of calves increased compared with AR and RS once daily systems. Knowles and Edwards (1983) reported that there was no effect on the reproductive efficiency of the suckled and non-suckled cows.
There was no mastitis problem in RS cows, which can possibly be attributed to the greater stimulus for evacuating the udder when these cows suckle their calves. Alvarez et al (1980) reported that mastitis incidence was reduced when cows were milked with the calves reared by RS. These results are in agreement with findings of Ugarte and Preston (1975).
The restricted suckling system improved growth rate of the calves, increased total milk yield and saleable milk of the cows, and reduced mastitis incidence, but had no effect on the reproductive rate compared to the artificial rearing system.
Restricted suckling is therefore a more appropriate system for managing both cows and
calves, than is calf removal and artificial rearing, and can be recommended especially for
smallholder farmers.
This study was financed partially by the International Foundation for Science through a
grant (B/2294-1) to the senior author. The cooperation of the National Institute of Animal
Husbandry, Hanoi, Vietnam is acknowledged.
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Received 2 June 1997