The quantity and composition of milk taken by calves 
reared by restricted suckling in smallholder 
dairy farming areas of Zimbabwe

 W Mandibaya, C Mutisi, H Hamudikuwanda and Marrion Titterton

 
Abstract

A study was conducted to determine the quantity of residual milk sucked by calves for 5 weeks post partum and the composition of the milk immediately before milking in the Nharira-Lancashire smallholder farming areas of Zimbabwe. Seven communal area (CA) and 6 small scale commercial area (SSCA) farmers owning 49 cow-calf pairs of 3 breeds participated in the study. 

There were no significant differences in the morning milk intake by beef, dairy and dairy x beef (DxB) calves in both CA (mean: 1.39 kg) and SSCA (1.51 kg). Mean pre-weaning growth rates of calves from the 3 breeds were not significantly different in each area (mean: CA = 0.256 and SSCA = 0.343 kg/d). In the CA, the total morning milk yield (milk off-take + calf intake) was 3.5 kg for beef, 4.0 kg for DxB and 5.7 kg for dairy cows; the differences were significant. In the SSCA farms the beef and DxB cows had a lower yield (4.8 and 5.4 kg, respectively) than the dairy cows (7.3 kg). Differences in protein and lactose contents were significant among the 3 breeds in the CA. 

These results show that for a 30-minute suckling period, calves from the 3 breed groups consumed similar quantities of milk of a similar nutritive value.

 Key words: smallholder, restricted suckling, milk intake, milk composition

 
Introduction

Mandibaya et al (1999) observed that most smallholder farmers in Zimbabwe used restricted (partial) suckling as a method of feeding milk to calves. The commonly practiced suckling periods in both the communal farming areas (CA) and small scale commercial farming areas (SSCA) were either 30 minutes or one hour after the cows had been hand milked. However, the quantity and composition of milk consumed by the calves is not known. This knowledge is important considering the various breeds of animals kept and the different feeding and management regimes practiced in the smallholder farming areas. The amount and composition of milk fed influences: the solid (concentrate) feed intake and development of the rumen (Roy 1980); growth rate and health status of calves (Radostits and Bell 1970; Foldager et al 1997); weaning age and weight (Little et al 1989); nutritional, health and reproductive performance of the dam (Preston 1989; Mukasa-Mugerwa et al 1991) and the milk ultimately available to the household for sale and consumption (Preston 1989; Tegegne et al 1994). In addition, the level of milk fed to female calves is known to subsequently affect their milk production in first lactation (Foldager et al  1997).

The objective of this study was to establish the amount and composition of milk from different breeds available to calves reared under restricted suckling in smallholder areas.

 Materials and Methods

 Study area and participating farmers

The study commenced in February 1996 on smallholder farms in the CA of Nharira and the adjacent SSCA of Lancashire, both in Chivhu. Chivhu is located in Chikomba District of Mashonaland East Province and is 170 km south east of Harare, the capital city of Zimbabwe. This district is characterised by poor sandy soils of granitic origin, and infrequent, heavy rainfalls totalling 570 to 750 mm during an average season. Land holdings are much larger in the SSCA (125 ha) than in the CA (0.4 to 0.7 ha) (Chiduza 1994; Francis et al 1996). While farmers in the SSCA own the land, ownership of land in the CA, including the grazing land, is communal. Communal area farmers mostly practise subsistence farming whereas SSCA farmers have a commercial orientation.

 Ten farmers from the CA and 8 farmers from the SSCA were randomly selected to participate in the study. These farmers were selected on the basis of a representative domain as described in Mandibaya et al (1999). The CA farmers collectively owned 25 cow-calf pairs and the SSCA collectively owned 24 cow-calf pairs. The determination of milk composition was based on data from 23 and 24 multiparous cows from the CA and SSCA farms, respectively.

 Monitoring procedure and measurements

The quantity of milk obtained by the calves was estimated by means of the weigh-suckle-weigh technique (Williams et al 1979). During the estimation of milk intake, only the weights of calves that did not defaecate or pass urine were recorded. Calves were allowed to suck residual milk after the morning hand milking of their dams. Estimation of the milk intake was only carried out during the morning milking because all the farmers milked the cows during the morning (Mandibaya et al 1999). The differences in the weights of the calves before and after suckling and the time allowed (not exceeding 1 hour) by the farmer for the calf to be suckled by its dam were noted for a period of five weeks post partum.

Milk samples were collected once per month for the duration of the lactation period in order to assess their nutritive value over the year. The collection commenced at 7 days post partum. About 30 ml of milk was obtained from all four quarters of the udder at the start of milking. The milk was collected into vials containing a preservative (sodium dichromate). The contents of the vials were mixed thoroughly and refrigerated for later analysis. Samples of the supplementary feeds offered to the calves and cows were also collected for later chemical analysis. The weights of the calves were estimated (using a weigh band) once per month until they were weaned.

Chemical analyses

The milk samples were analysed for total solids (TS), fat, protein and lactose contents using the methods described in AOAC (1990). Solids not fat (SNF) were calculated from the difference between TS and fat content. The conventional proximate analysis (AOAC 1990) and fibre analysis (Goering and Van Soest 1970) methods were used to determine the chemical composition of the supplements.

Statistical analyses

The data were analysed using the general linear models procedure of SAS (1996). Based on the available breeding records and visual appraisal, the animals were classified into three breed group types. These were beef (all non-dairy breeds such as Mashona, Brahman, Sussex, Simmental, Africaner and Tuli), dairy (mainly Friesian, Jersey, Red Dane, Sahiwal and crosses between them) and dairy x beef (DxB) breed groups. Averages of milk intake and milk yield for the five weeks and the pre-weaning growth rate were used in the analyses with each area treated separately. Comparison of means from the response variables (milk intake, milk yield and pre-weaning growth rate) was done using Duncan’s Multiple Range test. The models used for the analysis were:

(i) Y_ijkl (milk intake) =  m + F_i + A_j + B_k + C_l + e_ijkl,

(ii) Y_ijk (milk yield) = m + F_i + B_j + J_k + e_ijk,

(iii) Y_ijk (milk composition) = m + F_i + B_j + D_k + e_ijk, and

(iv) Y_ijklmno (pre-weaning growth rate) = m + F_i + A_j + C_k + G_l + H_m + I_n + J_o + e_ijklmno,

where Y_i..._o is the dependent variable, m is the overall mean, F_i is the effect of the i^th farm, A_j is the effect of the j^th birth weight, B_j (j = 1, ... 3) is the effect of the j^th breed group of the dam, C_k (k = 1, ... 3) is the effect of the k^th breed group of the calf, D_k is the effect of the k^th month of sampling, G_l is the effect of the l^th treatment, H_m is the effect of m^th season of birth (wet or dry), I_n is the effect of the n^th sex of the calf, J_o is the effect of the o^th quantity of milk consumed by the calf and e_ijklmno is the random error.

Results

Supplementary feeding

Table 1 shows the chemical composition of the supplementary feed and commercial feeds which were fed and a farm-grown meal which was offered to the calves. The supplementary feeds given  to the cows were usually offered during milking in the milking shed. The recommended feeding level was 0.5 kg per litre of milk produced. However, this was frequently not followed. Feed was offered in order to calm the animals during milking since soon after milking the animals were taken out of the shed. The supplements offered to calves were rarely weighed. Where farmers made an effort to estimate or weigh the supplement offered, the quantity refused (usually from the calves) was rarely estimated.

Table 1. Chemical composition (%) of the supplementary feeds1
	DM	Ash	CP	NDF	ADF	EE	Ca	P	Fed in
Snapcorn & sunflower meal	93.2	4.8	12.8	47.3	31.3	18.9	0.20	0.34	SSCA
Maize grain2	94.5	1.4	7.9	43.2	3.8	2.91	0.04	0.85	CA & SSCA
Urea-treated maize stover	93.1	5.7	11.9	83.6	56.7	0.99	0.16	0.04	more in SSCA
Empty maize cobs	97.7	2.3	2.0	98.1	52.4	0.60	0.03	0.02	CA
Groundnut stover/tops3	93.4	30.0	7.4	67.5	48.3	1.29	0.83	0.11	CA & SSCA
Groundnut shells2	91.9	10.9	6.2	87.1	77.5	1.98	0.39	0.11	CA & SSCA
Cow pea stover2,3	93.0	21.6	9.2	67.4	44.1	2.34	1.04	0.06	CA & SSCA
Commercial dairy meal4	91.8	5.7	23.0	39.5	13.8	2.22	1.50	0.60	more in SSCA
Commercial calf meal	92.7	6.8	15.5	29.3	13.9	4.16	6.0	3.3	more in SSCA
Farm-grown calf meal	92.1	4.4	9.6	43.7	20.2	5.51	3.1	3.1	CA & SSCA
1 The supplements are usually coarsely milled or chopped. 2 Quantities are limited. For maize grain there is competition with the household needs. 3 Soil contamination is a common problem. 4 A concentrate mixed with crushed maize grain at a ratio of 1:3.

Quantity of milk suckled by the calf

The pre-weaning growth rate, estimates of milk intake, milk yield and the milk sucked by the calf as a percentage of the dam’s morning milk yield are shown in Table 2. Average milk intake for 30 minutes and one hour suckling periods was first analysed to investigate any differences. No differences (P>0.05) were observed between the milk intake when suckling duration was less than or equal to 30 minutes and when suckling lasted up to an hour. Thereafter further analyses were undertaken using the means from the 30-minute suckling duration. The morning milk intake was affected (P<0.05) by the dam’s morning milk yield in both areas and by the breed group of the dam (P<0.01) in the SSCA. In the CA, milk yield was affected by the breed group of the dam (P<0.001) and the amount of milk suckled by the calf (P<0.05); in the SSCA, only calf milk intake affected milk yield (P<0.01). No farmer differences (P>0.05) were observed in the morning milk intake and yield in both areas.

Table 2. Calf milk intake (MI), total morning milk yield (MY), the calf MI as a percentage of the total MY (MI/MY) of the dam and the pre-weaning calf growth rate in the communal area (CA) and small scale commercial area (SSCA)
	CA	CA	CA	SSCA	SSCA	SSCA	SEM
	Beef	DxB	Dairy	Beef	DxB	Dairy
Calf MI (kg)	1.63	1.50	0.91	1.36a	0.89a	2.30b	0.50
Total MY (kg)	3.52a	4.00ab	5.72b	4.83a	5.39a	7.34b	0.83
MI/MY (%)	46.3	37.5	18.4	28.2	16.5	31.3	-
Milk offtake1 (kg)	1.89	2.50	4.67	3.47	4.54	5.04	-
Growth rate (kg/d)	0.345	0.230	0.194	0.392	0.334	0.305	0.11
DxB = Crosses between dairy and beef animals. SEM = Standard error of means. ab Means in each row in each farming area with different superscripts are different (P<0.05). 1 Total MY – Calf MI. (Milk obtained by hand milking).

There were no breed group differences (P>0.05) in the milk intake by calves in the CA. In the SSCA, dairy calves sucked a higher (P<0.05) quantity of milk than beef and dairy*beef (DxB) calves. In the CA, the proportion of milk sucked by the calf was high in the beef calves and decreased with increasing proportion of the dairy blood in the calves. However, in the SSCA, the beef and dairy calves sucked a similar proportion of milk while the DxB consumed less. Milk yield was higher (P<0.05) in the dairy cows compared to the DxB and beef cows in both areas. Milk off-take followed a similar trend as milk yield. There were no significant differences in the growth rates of the calves from the three breed groups within each area.

Composition of milk from the dams

The fat, protein and TS of the milk were affected by month of sampling (P<0.001) and the lactose content was affected (P<0.05) by management (the farmer), breed group and month of sampling (Table 3 and Figure 1).

Table 3. Mean composition (%) and milk energy1 content (ME; MJ/kg) of the hand-milked morning milk of cows in the communal area (CA) and small scale commercial area (SSCA)
	CA	CA	CA	CA	SSCA	SSCA	SSCA	SSCA
	Beef	Dairy	DxB	SEM	Beef	Dairy	DxB	SEM
Fat	3.55	4.27	3.97	0.571	4.19	2.34	3.05	1.295
Protein	3.70a	3.62ab	3.22b	0.162	3.76	3.56	3.53	1.102
Lactose	4.51a	4.20b	4.93c	0.141	4.81	4.75	5.00	0.319
TS	12.52	13.14	13.11	0.543	13.84	11.65	12.59	1.231
SNF	9.16	8.88	9.14	0.156	9.65	9.31	9.55	0.353
ME1	2.95	3.25	3.19	0.213	3.57	2.59	2.91	0.482
DxB = Crosses between dairy and beef animals. SEM = Standard error of means. abc Least square means in each row in each farming area with different superscripts are different (P<0.05). 1 The ME was calculated using the following equation; Milk Energy (MJ/kg) = 0.0386*Fat (g/kg) + 0.0206*SNF (g/kg) - 0.23 (Tyrrell and Reid 1965).

Although the model was highly significant (P=0.0001), it accounted for less than half of the variation in fat, lactose and total solids (R² = 0.47) and only 25% of the variation in protein. In the CA there were no differences (P>0.05) in the fat and TS contents of the milk among the three breed groups. The protein content was highest in milk from the beef cows (3.7%) and lowest in milk from the DxB cows (3.2%) while lactose content was highest (P<0.05) in milk from the DxB cows (4.9%) and lowest in the dairy cows’ milk (4.2%). In the SSCA there were no differences (P>0.05) in the chemical contents of the milk from the three breeds, although the protein content of the milk from the dairy cows was rather low (2.34%). 

 The milk fat content in the CA declined from February (6.5%) to October (1.9%), then began to rise in December (3.1%) whereas in the SSCA it seemed to fluctuate markedly but peaking in May (5.9%) and was generally lower than that from CA cows (Figure 1). In both areas, the milk protein content followed a similar pattern to changes of the fat content, but the seasonal fluctuations were less marked (Figure 2). 

The lactose profile in the CA was the opposite of the fat content since it rose steadily from 4.1% in February to 5% in December. In the SSCA, the lactose content trend was opposite to that in the CA as it declined steadily from 5% in February to 4.6% in October and began to rise in December (Figure 3).

 In both areas, SNF declined from February to reach a trough in August-September and began to rise, but the values were higher in the SSCA during the early months of the year (Figure 4). This was mainly due to the corresponding low fat content in the milk of the SSCA cows during this period.

Discussion

The differences in the performance of the calves in the CA and SSCA were not due to differences in milk intake because the calves consumed similar amounts. The absence of significant breed group differences in milk intake in the CA was probably due to the small genetic differences in the breed groups as a result of uncontrolled crossbreeding in this area (Mandibaya et al 1999). This is supported by the small differences in the mornimg milk yield of the three breed groups in the CA. When calves were suckled for one hour they did not obtain a significantly different quantity of milk from those that were suckled for 30 minutes. Similar results have been obtained (Preston 1989) in other smallholder farms. This implies that there was no benefit to the farmers for letting the cows suckle their calves for periods longer than 30 minutes. 

The five-week post partum period was chosen in order to monitor calf milk intake from birth up to peak milk yield of the dam. This period is also very critical in calf survival and growth, especially in smallholder areas where supplementary feeding is inadequate and inconsistent as noted previously (Mandibaya et al 1999). In addition, the reliance on the liquid diet starts to decline by five weeks of age for calves allowed access to solid feed and pasture early in life. 

The farm-grown supplementary feeds had lower crude protein and higher fibre contents compared to the commercial supplements. Feeding home grown supplements was inconsistent and inadequate due to financial constraints at the household level. As a result, quantities offered to animals were limited. The tendency by farmers to offer supplementary feeds to cows during milking in order to calm the animals has also been reported in smallholder dairy farms in Uganda (Kabirizi and Drania 1996).

 A large proportion of the unexplained variation in the composition and milk yield may be accounted for by the dry matter intake and feed type offered to the animals. The effects of the amount of protein, fat, metabolisable energy and roughage:concentrate ratio in dairy rations on milk yield and composition are well established. Other factors that may account for the unexplained variation in the amount of milk consumed by the calves include the dam’s parity and the solid feeding regimes of the calves. Venkatasubramanian and Fulzele (1996) observed that the performance of crossbreds and indigenous cattle in India was affected by the feeding management, calf management, housing and breeding management practised on the farm.

Differences in the proportion of the milk yield accounted for by the calf could have been due to the differences in the extent of milk let down between specialised dairy breeds (Bos taurus) and the “indigenous” B. indicus breeds despite the fact that indigenous cows suckled their calves for about one minute just before the commencement of milking. While dairy breeds readily release most of their milk during (hand) milking, the B. indicus breed tend to voluntarily suppress milk ejection during milking (Preston 1989). However, dairy calves in the SSCA sucked an equal proportion of the milk as indigenous calves (31.3 vs 28.2%). This high proportion could be due to the high milk yield of the dairy cows and a possible high residual milk content in the udders of these cows. The percentage milk intake by calves was higher in beef calves from the CA and lower in beef calves from the SSCA compared to the 35.7% sucked by ”indigenous” (beef/dual purpose) calves in early lactation in Sanyati CA in Zimbabwe (Pedersen and Madsen 1998). However, this figure (35.7%) was for the total daily calf milk intake. Mejia et al (1998) obtained an average of 20.1% of daily milk yield in Mpwapwa and Mpwapwa crossbred calves (suckled for 30 minutes twice per day) in Tanzania, which is higher than the figure obtained for DxB calves in the SSCA and lower than that for DxB calves in the CA in this study.

 The differences in the milk yield between the three breed groups were expected, especially in the SSCA, and are probably due to the different genetic potential and intra-breed variation. However, different planes of feeding can modify the performance of animals across and within breeds. In other smallholder areas, where feeding regimes are low to poor as in the CA, exotic dairy breeds are outperformed by crossbreds in terms of milk production (Preston 1989). The better feeding regimes found on the SSCA farms may account for the high milk yields observed in the beef cows in that area.

The quantity of milk obtained by calves did not affect their pre-weaning growth rate. This means that the differences in the growth performance of the calves was due to factors other than milk intake in the first five weeks of life. The rate of weight gain of calves in this study was moderate and is comparable to growth rates observed in other smallholder areas. Roy (1980), Preston (1989) and Little et al (1989) have shown rates of weight gain between 0.3-0.89 kg/d in calves fed similar levels of milk. In Sanyati CA, Pedersen and Madsen (1998) observed weight gains of 0.35 kg/d during the first 84 days of life by calves sucking 2.5 litres/d that decreased to 1 litre/d by the third month. These calves were not offered any supplementary feeds but grazed natural pasture only. This moderate growth rate achieved by the un-supplemented calves was probably due to the high fat content in residual suckled milk (Mejia et al 1998). Mejia et al (1998) recorded growth rates of 0.38 kg/d over 22 weeks in calves suckling 2 litres of milk per day and offered a concentrate meal containing 16.8% crude protein.

Although the calves from the three breed groups in both the SSCA and the CA consumed similar amounts of milk, the milk off-take was different due to the differences in the milk yields of the cows. These results demonstrate the advantages of using dairy breeds or upgrading indigenous animals in terms of milk production since these breeds had higher milk yields and milk offtake compared to the beef cows.

Monitoring milk composition until the end of the dry season was done to assess the quantity of the nutrients that pass the rumen. This is because milk is an important “catalytic” supplement to poorly fed calves (Preston 1989), especially during the dry season. Variations in the chemical composition of the milk reflected the differences in the feeding regimens between the CA and SSCA farms. While in the CA there was inadequate and inconsistent supplementary feeding of cows, the SSCA had better feed resources and pasture. The levels of milk fat and protein, in the CA, increased between February and May. This was in response to the improved quality of natural pasture during the rainy season (November to April), unlike in the SSCA where the milk composition did not fluctuate due to continuous availability of better pastures and consistent supplementary feeding. The lactose content of milk did not vary. This is expected since lactose plays an important role in maintaining the osmotic pressure of milk. The SNF content of milk decreased with advancing season. This was probably due to the decline in the protein content of the natural pastures, especially in inadequately supplemented herds. The general decline in ME content of milk meant that calves benefited more from a higher energy value of suckled milk during the rainy season compared to the drier months. The milk consumed might have had a higher energy content since residual milk has been shown to have a higher fat content than milk taken by milking (Mejia et al 1998). However, consistent trends in the components of the milk were distorted by the different parities and stages of lactation of the cows used in this study and the different breed composition of each breed group. In addition, besides different feeding regimes and breed variations, there is an appreciable within breed variation in the performance of dairy animals even under similar management.

Conclusions

The quantity of milk sucked by calves in the morning during the first five weeks of life did not significantly affect their growth rate up to weaning. Therefore, it is likely that restricting the suckling period to 30 minutes will have no negative effects on the performance of the calves from the three breed groups. Farmers in this study area may benefit more financially by restricting suckling duration to 30 minutes since milk intake significantly affected milk yield. This however, has to be confirmed in other experiments. In both areas, the amount of milk off-take was higher from the dairy cows, followed by the DxB with the beef cows having the lowest. There were no marked differences in the chemical composition and energy value of the milk from the three breed groups in the two areas. It is recommended, therefore, that similar suckling periods be practised in these smallholder dairy farms irrespective of breed types of the calves.
 

Acknowledgements

We thank The Danish Foreign Ministry for the financial support to the research co-operation between the University of Zimbabwe, the Royal Veterinary and Agricultural University and the Danish Institute of Agricultural Sciences. Farmers in Nharira-Lancahire are gratefully acknowledged for their co-operation during the study. The helpful comments from colleagues who reviewed this script are sincerely appreciated.
 

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