Effects of restricted suckling versus artificial rearing on milk production, calf performance and reproductive efficiency of dual purpose Mpwapwa cattle in a semi-arid climate

Carlos E Mejia^*, Thomas R Preston^** and Pernilla Fajersson***

Livestock Production Research Institute (LPRI), Mpwapwa, Tanzania
*Centro pare la Investigacion en Sistemas Sostenibles de Produccion Agropecuaria (CIPAV), Carrera 35A Oeste # 3–66 Cali, Colombia. AA: 20591. (mejia@cipav.org.co)
** Finca Ecologica, College of Agriculture & Forestry, Ho Chi Minh City University, Thu Duc, Vietnam (tpreston@hcm.vnn.vn)
***Texas A & M University, Texas, USA

Abstract

Twenty purebred Mpwapwa and 16 crossbred Mpwapwa cows with calves were used in an experiment to compare restricted suckling (RS) versus artificial rearing (AR) of calves in Tanzania. A randomized design was used. Calves remained with their dams during the first five days and were then allocated to the RS or AR treatments; AR calves were weaned at 75 days of age and were provided with 4 1itres of milk daily for 70 days, while RS calves stimulated milk letdown of the cow and after milking were suckled by their dams for 30 minutes. All calves were grazed and were provided with concentrate, minerals and water ad libitum. Milk yield from cows and milk consumed by calves were recorded for 175 days after calving. Reproductive behavior of the cows was determined by Radio-immuno-assay (RIA) of milk progesterone.

Six of the 18 AR cows were affected by mastitis compared to only one of the RS group. Mean (±SE) daily yields of milk for Mpwapwa cows in RS and AR were 6.9 ± 0.45 litres and 7.6 ± 0.41itres (P>0.05), respectively. Corresponding values for crossbreeds were 8.6 ± 0.54 and 8.0 ± 0.59 1itres (P>0.05), respectively. The daily saleable milk for Mpwapwa cows in RS and AR was 6.9 ± 0.45 1itres and 6.0 ± 0.411 (P<0.05), respectively; while for crossbred cows the amounts were 8.6 ± 0.54 1itres and 6.4 ± 0.59 1itres (P<0.05), respectively. Mean daily total milk yields for Mpwapwa RS and AR cows were 8.9 ± 0.44 1itres and 7.6 ± 0.40 1itres (P<0.05) and for crossbreeds 10.6 ± 0.53 1itres and 8.0 ± 0.58 1itres (P<0.05), respectively. Means (±SE) for fat content in bucket milk and residual milk, for Mpwapwa were 3.56 ± 0.25 % and 4.97 ± 0.25% (P<0.05), respectively; and for crossbreeds 3.6 ± 0.31% and 6.3 ± 0.31% (P<0.05), respectively. Mean daily gains for RS and AR calves were 381 ± 16 g and 356 ± 16 g (P>0.05), respectively. Saleable milk from RS cows was 15.0 % higher for the Mpwapwa and 34.3 % higher for the crossbred cows compared to saleable milk from cows of either breed with calves under AR. Body weight of cows postpartum was not affected by restricted suckling.

Milk progesterone measurements showed that there was no significant between the RS and AR treatments for the interval from calving to initiation of oestrous (progesterone>0.5nmol/litre). However, RS cows took significantly longer to show a regular oestrous cycle (P<0.05).

Key words: Restricted suckling, milk production, reproductive performance, Mpwapwa cattle, semi-arid region, Tanzania.

Introduction

The strategy most frequently advocated for establishing a dairy industry in developing countries is the crossbreeding of native cows using imported semen of specialized dairy breeds (Preston and Leng 1987). As part of the "technological package" it is usually advocated that calves are removed from their dams within a few days after birth and bucket-fed either with cows' milk or milk substitute. In the majority of developing countries milk substitutes are either not available or more expensive than whole milk because they have to be imported (Knowles and Edwards1983; Ugarte 1989; Chamberlain 1989). In view of this it has often been the practice in these countries to adopt an artificial calf rearing system utilizing whole milk instead of milk substitutes. This is the case in Tanzania, and within Tanzania at the Livestock Production Research Institute (LPRI), Mpwapwa.

This system has been strongly questioned as being inappropriate under the conditions of feeding and management in most developing countries (Preston 1977). According to Ugarte and Preston (1972), artificial rearing not only needs experienced workers, but also a high investment in buildings and individual pens,. Morever, it is necessary to keep a high hygienic level, otherwise calf mortality can be high (Chamberlain 1989). Preston (1977) reported that restricted suckling appears to be a more viable option, because it results in increased performance of both the cow and the calf.

The purpose of the present study was to compare the effects of restricted suckling (RS) versus artificial rearing (AR) of calves on milk production and reproductive efficiency of purebred or crossbred Mpwapwa cows in Tanzania and on the performance of the calves.

Materials and methods

Location

The research was carried out at the Livestock Production Research Institute (LPRI), Mpwapwa, which lies in the semi-arid zone in central Tanzania. Mpwapwa is on latitude 6° 21'S, and longitude 36° 32' E, and is in Dodoma Region (Mchau 1988), and at an altitude of 1100 m above sea level. The average annual rainfall is 660 mm and varies greatly in distribution and amount from year to year. Drought years with low erratic rainfall are frequently experienced About 90% of the rains fall between December and April, and there is usually a dry spell in February. The average minimum temperature is 15.5° C, the coolest month being August (13.8° C). The average maximum temperature is 27 5° C, the warmest month being November (30.2° C). Soils are clay loams, low in nitrogen and phosphorus but adequate in potassium. The pH of the topsoil ranges between 5.6 and 7.7 (LPRI 1983).

Duration

The experiment was started in December 1992 and continued through the end of August 1993. For all animals data were recorded for 175 days.

Animals

Twenty purebred Mpwapwa cows and 16 crossbred Mpwapwa cows, which calved between December 1992 and February 1993, and their young calves were used in the experiment. The Mpwapwa breed is made up of: 92 % Bos indicus (32 % Red Sindhi, 30 % Sahiwal, 19 % Tanzanian Shorthorn Zebu, 11 % Boran) and 8 % Bos taurus mainly Ayrshire. (Kiwuwa 1971). The Mpwapwa crossbred cows were estimated to have been derived from 66% Mpwapwa and 34 % Bos taurus breeds, either Ayrshire, Friesian or Jersey (Macha 1986).

Management of the cows

The cows were divided into two groups, comprising Mpwapwa crosses and purebred Mpwapwa according to the breeding program at the institute and were bred naturally. Bulls grazed with the cows for the whole duration. These animals were grazing during the day in paddocks of mixed pasture, mainly Chloris gayana, Cenchrus ciliaris and Cynodon spp. From May 15 to the end of the experiment (August 26), all cows had access to maize stovers in crop areas.

Two herdsmen were responsible for herding a group of grazing cows during the day time. Cows were kept in a fenced paddock with similar pasture during the night time and provided with fresh water ad libitum. Cows were weighed twice a month to determine body weight changes during the experimental period. Hand milking was done twice a day at 7.00 am and 4.30 pm. All cows were supplemented with 2 kg of concentrate, which was a mixture of maize bran (50%) and milled sunflower seed cake (50%), at each milking time, giving a total of 4 kg/cow/day. The analysis of the concentrate was (% of dry matter): crude protein 16.8, neutral detergent fibre 50.8, ash 5.8. (%).Minerals were given to all cows as a mixture composed of sea salt (50%) and commercial mineral mix (50%) at milking time. The commercial mineral mixture contained (%): Ca 20.5, P 12.0, Na 10.3, Cl 15.8, Mg 2.0, Cu 0.16, Co 0.02, Fe O.5, K 0.006, I 0.02, Zn 0.5, Mn 0.4, S 0.33 and Se 0.001.

Management of calves

The calves that were born beween December 1992 and February 1993 remained with their dams for the first five days, and thereafter were put in individual pens until the completion of two paddocks in February 1993. All calves were then kept in paddocks in groups according to the treatment. The predominant grass in the calves' paddocks was Chloris gayana. Calves were provided with concentrates and minerals ad libitum throughout the study. The composition was the same as that fed to the cows. Fresh water was provided ad libitum. Shelter was built in the paddocks for protection from rain and sun. The groups of calves were moved between the paddocks weekly. During the study period the calves were dewormed twice. All calves were weighed once a week to determine the daily growth rate.

Calves on AR

Calves on the AR treatment were suckled by their dams for the first five days and then were given 4 litres of milk daily derived from the bulked total milk from the AR dams. The milk was fed by bucket twice a day until weaning at 75 days of age.

Calves on RS

The RS calves were started on the trial at five days of age. Thereafter, they were used to stimulate milk letdown by sucking each of the cow's teats for a few seconds before the cow was hand milked. Milk in one quarter of the udder, plus the residual milk in the other quarters, was left to be consumed by the calf immediately after hand milking was completed. After each milking, the calves were allowed to be suckled by their dams for about 30 minutes in a group pen where all RS cows and their calves were put together until 45 days of age. After 45 days all four quarters of the cow's udder were milked and the calves continued with the milk "let down" stimulation and sucked the residual milk in the four quarters until weaning at six months of age. Milk consumption by calves was recorded by weighing them once a week during the two milking times. Weighing was done before the stimulation of milk let down and after completing the suckling of the residual milk. The procedure was repeated on the next day for those calves that urinated or defecated between the weighings.

Data collected

Daily milk production was recorded for morning and afternoon milking for 175 days. Cases of clinical mastitis were recorded according to the number of animals and the number of quarters affected. Milk consumption by the RS calves was recorded once a week by weighing the calves before and after suckling.

In order to analyze milk composition, from April 27 to June 22 1993, a milk sample of 50 cc from each RS cow was taken twice monthly from the bucket and another from the teat just before suckling by calves. Samples were preserved by adding 0.5 ml of a mixture of 2% bromopol and 0.05 % methylene blue and were stored in a deep freezer. The samples were analyzed for fat by the Gerber Method (Richardson 1985) and protein by the Kjeldahl procedure (Richardson 1985). In order to monitor the ovarian activity, 10 ml milk samples were collected twice a week on Monday and Friday mornings from all cows. This was done from 45 days post-partum until the end of the project on August 26 1993. To these samples about six drops of a preservative (2% bromopol and 0.05 % methylene blue) were added and they were put in a cool box until the end of the collection on each respective day. The samples were centrifuged in order to remove the milk fat. The skim milk obtained was stored in a deep freezer and later analyzed using radio-immuno-assay analyses (RIA) kits for milk progesterone. The Coat-A-Count progesterone kits of Diagnostic Products Corporation (DPC) were used and standards were supplied by the International Agency of Atomic Energy (IAEA). The progesterone concentration was calculated by the RIAPC program (Rieger 1988).

Detection of oestrous in cows was done daily by the herdsman who herded the animals during the day time. Pregnancy diagnosis was done by rectal palpation on October 21 1993, and the diagnosis was only to determine whether or not the cows were pregnant. The number of days from calving to conception was determined by progesterone concentration in skim milk.

Experimental design and statistical analysis

A completely randomized design with two factors, calf rearing system (RS and AR), and breed (purebred Mpwapwa and Mpwapwa crossbreds), was used. The statistical analysis was done by using the General Linear Model procedure in Minitab version 8.

Records from the following cows (and their calves) were removed from the data set before analysis: three AR cows which had a very serious mastitis problem, two RS cows that were sick from anaplasmosis, and one RS cow that damaged its udder. Also the records from one AR calf which died and another two that became sick were also taken out of the data set.

Results

Performance of cows

In a restricted suckling system "total production" is comprised of milk extracted by the milker (person or machine) plus that sucked by the calf after milking. The milk sucked during the stimulation period (before milking) is very small and is ignored because it cannot be detected by the weighing "before and after" method. For artificial rearing "total production" is the milk extracted by the milker. production of the cows from the AR and RS groups is shown in Table 1. There was a significant difference in total milk production between treatments (P<0.05). In purebred Mpwapwa cows, production was 17.1% higher for RS than for AR; in crossbred cows it was 32.5 % higher in RS than in AR. Comparable values for "saleable" milk (after deducting that consumed by the calf for the AR treatment) were 15.0 % higher for RS than AR in Mpwapwa , and 34.3 % higher in RS than in AR for crossbred (P<0.05). These relationships are illustrated in Figures 1 and 2.

Table 1: Average (±SE) milk production (litres/day) during 175 days in Mpwapwa and Mpwapwa crossbred cows under restricted suckling (RS) and artificial rearing (AR) systems.
	Purebred Mpwapwa		Crossbred Mpwapwa
Litres/day	Restricted suckling	Artificial rearing	Restricted suckling	Artificial rearing
At milking	6.9±0.45	7.6±0.41	8.6±0.54	8.0±0.59
Calf consumption	1.9±0.14	1.6#	2.0±0.17	1.6#
Saleable milk	6.9±0.45	6.0	8.6±0.54	6.4±0.59
Total milk	8.9a±0.44	7.6b±0.4	10.6a±0.53	8.0b±0.58
ab Means in same row within breed with different superscripts differ at P<0.05 # 4 litres of milk fed during first 70 days equivalent to 1.6 litres/day over the 175 days of the experiment

Figure 1: Average milk production during 175 days in Mpwapwa cows under restricted suckling (RS) and artificial rearing (AR) systems. Figure shows calf´s milk consumption in each system.

Figure 2: Average milk production during 175 days in Mpwapwa crossbred cows under restricted suckling (RS) and artificial rearing (AR) systems. Figure shows calf´s milk consumption in each system.

Mastitis was the main health problem for the cows (Table 2). Incidence was higher in AR than in RS cows. Milk fat was significantly higher in suckled milk than in milk taken in the bucket (Table 3). There was no difference in the protein content of the milk.

Table 2: Mastitis incidence in Mpwapwa and crossbred cows under restricted suckling (RS) and artificial rearing (AR) systems (Data from 36 cows; 18 in each treatment)
	No of cows affected
No of quarters affected	Restricted suckling	Artificial rearing
One	1	4
Two	0	1
Four	0	1
Total quarters affected	1	10

Table 3: Average values (±SE) for fat and protein content in bucket milk and in residual (suckled) milk from Mpwapwa and Mpwapwa crossbred cows under restricted suckling system (data from 15 cows: 9 Mpwapwa and 6 Crossbred)
	Purebred Mpwapwa		Crossbred Mpwapwa
	Bucket milk	Residual milk	Bucket milk	Residual milk
Fat, %	3.56a±0.25	4.97b±0.25	3.60a±0.31	6.31b±0.31
Protein, %	3.46±0.11	3.33±0.11	3.23±0.11	3.20±0.13
ab Means in same row within breed with different superscripts differ at P<0.05

Reproductive performance

The data derived from measurement of milk progesterone (Table 4) showed that there was no significant between the RS and AR treatments for the interval from calving to initiation of oestrous (progesterone>0.5nmol/litre). However, RS cows took significantly longer to show a regular oestrous cycle (P<0.05).

Table 4: Effect of artificial rearing or restricted suckling on reproductive performance (15 cows in each treatment)
	Restricted suckling	Artificial rearing	Prob.
Calving to milk progesterone  0.5nmol/litre, days
Mean and SE	94±6.0	84.2±7.0	NS
Range	62-132	46-126
Calving to first regular cycle, days
Mean and SE	165±15	126±13	<0.05
Range	95-185	79-160

Nine cows from RS and 11 from AR showed oestrous signs which were detected visually; the mean intervals from calving were 162 ± 16 days and ranged from 87 to 202 days (RS), and 95 ± 15 ranging from 22 to 195 days (AR). This difference was significant (P<0.05). These observations were reflected in the data for pregnancy diagnosis (Table 5).

Table 5: Days from calving to conception in Mpwapwa and Mpwapwa crossbreed cows under restricted suckling (RS) and artificial rearing (AR) systems (18 cows per treatment).
	Restricted suckling	Artificial rearing
<100days	0	0
101-180 days	3	9
>180 days	4	4
Total pregnant	7	13

Body weight of cows.

There was no significant differences in changes of bodyweight of cows between AR and RS treatments (Table 6).

Table 6: Changes of body weight (kg±SE) of purebred and crossbred Mpwapwa cows under restricted suckling (RS) and artificial rearing (AR) systems during the first 180 days of lactation.
	Purebred Mpwapwa		Crossbred Mpwapwa
	Restricted suckling	Artificial rearing	Restricted suckling	Artificial rearing
Initial weight	282±1.1	305±12.44	360±0.31	317±17.6
Final weight	300±13.9	314±13.1	339±17.0	331±12.1
Weight gain	17.3±9.0	8.9±8.6	22.0±11.0	13.6±12.1

Performance of calves

The growth rates of the calves during the first 70 days, which was the period when both groups were fed milk, and for the total experiment (26 weeks) are shown in Table 7. AR calves were heavier than RS calves at 75 days. AR calves consumed almost 100 litres more milk than RS calves during this period. By 26 weeks body weights were similar for both treatments. The growth curves for AR and RS calves are shown in Figure 3.

Figure 3: Average daily gain Mpwapwa and crossbred calves from birth until 26 weeks old under restricted suckling (RS) and articial rearing (AR) systems. (1) Indicates point when all 4 quarters were milked (previously one had been left for the calf) and only residual milk available for suckling. (2) Indicates weaning.

Table 7: Performance of calves under restricted suckling (RS) and artificial rearing (AR) systems
	Restricted suckling	Artificial rearing
Birth weight, kg	24.2±0.82	23.5±0.81
70 days, kg	45.6a±1.3	52.6b±1.3
26 weeks, kg	92.7±3.0	87.9±2.9
Milk 5-75 days, kg	185±6.2	280
Milk 5 days to 26 weeks, kg	347±13.8	280
Milk conversion 5-75 days#	9.2±0.46	10.3±0.46
ab Means in same row with different superscripts differ at P<0.05; #kg milk/kg LW gain

Discussion

Milk production

There was no significant difference in milk taken at milking between the management systems, but since it was necessary to use 280 litres of whole milk to feed each AR calf, the amount of saleable milk was significantly higher in RS than in AR cows, the difference being 15.0 % for Mpwapwa and 34.3 % for the crossbreeds. This result agrees with Ugarte and Preston (1972; 1973) and Knowles and Edwards(1983) who reported similar findings. In this study the total milk production (in the case of RS this is milk at milking plus that sucked by the calves) was significantly higher for RS than for AR (17.1 % higher for Mpwapwa and 32.5 % higher for crossbred cows, respectively). This agrees with the report of Teeluck et al (1981) and was probably due to the increased stimulation to milk secretion caused by hand milking plus sucking for AR animals, as well as the high capacity of calves to suck deeply and remove all the residual milk. Lane et al (1970) reported that 15 % of the milk in the udder at start of milking remains as residual milk in conventional AR systems. Ugarte (1977), working on commercial farms with data obtained from 81,067 F₁ cows (50 % Holstein: 50 % Zebu) and 16,611 F₂ cows (75 % Holstein: 25 % Zebu) and using restricted suckling and artificial rearing, reported that F₁ and F₂ cows in restricted suckling produced more total milk than those in artificial rearing. Ugarte and Preston (1975) working with 60 Holstein cows and calves suckled twice a day, and 60 without calves found that from weaning (70 days) until the cows were dried off, milk production did not differ significantly between treatments, but there was a significant difference in total daily production throughout the lactation in favour of restricted suckling. For cows on restricted suckling the total production (milking and calf consumption) was 8.2 litres/day, while the cows without calves produced 7.3 litres/day.

Mastitis

The lower incidence of mastitis in RS compared to AR cows agrees with the previous reports by Ugarte and Preston (1972), Ugarte and Preston (1975), Alvarez et al (1980) and Ugarte (1989). The reason for this could be the high capacity of calves to suck all the residual milk and thoroughly evacuate the udder and also the cleaning (bacteriostatic) effect of the saliva (Ugarte 1989).

Milk fat content

The fat content in residual milk, compared with that taken at milking, was 39.6 % higher for Mpwapwa and 75.2 % higher for crossbred cows. Similar results were reported by Mai van Sahn et al (1997) working with Boran and European grade cattle in Morogoro, Tanzania. Chamberlain (1989) reported that the first milk removed from the udder is low in fat (1 to 2 %) compared with milk at the end of milking (7 to 9 %). Lane et al (1970) reported that residual milk contains 3 times more fat than normal milk. The higher amount of fat in residual milk can be explained by the fact that the fat globules are not evenly distributed in milk, and incomplete milking will tend to leave high-fat milk behind, lowering the milk fat percentage of the milk taken at milking (Chamberlain 1989).

Reproduction

Various factors have been identified as effective components on resumption of ovarian activity and uterine involution, including suckling (Chamberlain 1989), age, parity, under nutrition, calving season, intensity, milk yield and management system (Izaike 1990). Body weight at calving and weight changes during the post-partum period also affect the onset of reproduction in Zebu and crossbred Zebu cows (Garcia et al 1990). It is accepted that natural rearing produces long calving intervals and this has been more evident when increasing the age at weaning (Ugarte 1989). In this study, it was found that in the RS group there was a longer interval from calving to first behavioral oestrous than in the AR group. This is in agreement with Mukasa et al (1991) and Little et al (1991) who reported similar findings. In contrast Ferreira and Torres (1991) did not find any significant difference. Ugarte and Preston (1972) working with Holstein and F₁ (Holstein: Zebu) cows did not find significant differences between treatments in non-suckled cows, cows suckled once a day, and cows suckled twice a day, for the period between calving to first oestrous and percentage of pregnancy. The longer interval between calving to conception for RS cows compared to AR cows (see Table 5) agrees with Ugarte (1989) who reported that in F₁ and F₂ (Holstein: Zebu) cows on restricted suckling until 90 days, or without calves, the intervals between calving and conception were longer for restricted suckling compared to artificial rearing.

Body weight of cows

On average all cows gained body weight during the experimental period (see Table 6), which could be due partly to the high bypass protein content in the concentrate of maize bran and sunflower cake (Preston and Leng 1987). The good body condition of the cows is because dual purpose animals derived from crossing Bos indicus meat breeds with European dairy breeds partition nutrients more evenly between body stores and milk than do specialist milk breeds selected for milk yield. Thus dual purpose cattle maintain body condition on feeds which lead to body weight loss in dairy breeds. Ugarte and Preston (1972) working with lactating Holstein and Holstein X Zebu crosses, found that the crosses had greater gains in live weight than pure Holstein on the same feeding regime.

Performance of the calves

Total body weight gain at 75 days and milk consumption were higher in AR compared to RS calves (P<0.001); however, the milk conversion in RS tended (P=0.09) to be better. One reason for the good milk conversion, despite the lower growth rate, could be the higher fat content in the residual milk suckled by the RS calves. As calves in the RS group continued to be suckled until 175 days of age, the total lifetime milk consumption was higher for RS than for AR. This probably enabled them to compensate for their lower growth rate to 70 days, so that by 175 days there was no difference between the management treatments. This result agrees with that of Knowles and Edwards(1983), who worked with Malaysian F1 cows and Sahiwal X Friesian sires and found no significant differences in growth rate at 105 days between AR and RS calves.

The economic advantages of the RS treatment are that the calves grew as well as those on AR, but they used only residual (unsaleable) milk whereas on the AR treatment, the 280 litres of milk that were consumed could have been sold for human consumption.

Mortality

There was a very low calf mortality during the whole study; of 18 artificially reared calves only one died, while there were no deaths in the restricted suckling group. Ugarte (1989), analyzing deaths occurring in 195,000 births during a one year period in Cuba, found 9.9 %, 6.5 % and 7.2 % mortality in calves reared artificially, by restricted suckling and by natural rearing, respectively.

Conclusions

• The production of saleable milk was increased by 15.0 and 34.3 % when the restricted suckling system was applied to Mpwapwa and Mpwapwa crossbred cows, respectively.
• Restricted suckling extended the postpartum anoestrous and calving interval considerably in Mpwapwa and Mpwapwa crossbred cows.
• In Mpwapwa cows and crosses, mastitis incidence was reduced to minimum levels when cows were managed under a restricted suckling system.
• Daily gain was similar for restricted suckling and artificial rearing calves.

By applying restricted suckling, Tanzania and other developing countries, could increase the availability of milk for human consumption because this system reduces the competition for milk between people and calves.

Acknowledgments

We would like to thank the Swedish International Development Authority (SIDA) for its financial support of this study which was in partial requirement for the MSc degree in Sustainable Livestock-based Farming Systems, Swedish University of Agricultural Sciences, Uppsala, Sweden. We would like also to express our gratitude to the Commission for Research and Training, Ministry of Agriculture, Tanzania, for permitting us to conduct the project at the Livestock Production Research Institute, Mpwapwa.

References

Received 12 January 1998

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