Effect of restricted suckling on performance of Shorthorn and Sahiwal cows and calves in Pakistan

Effect of restricted suckling on performance of Shorthorn and Sahiwal cows and calves in Pakistan

*Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria, AA 20591 Cali, Colombia

Twenty cows drawn from a mixed population of Australian Illawara shorthorn (AIS), Sahiwal (S), their first crosses (F1) and back crosses to AIS (B1) were allocated to either artificial rearing (AR) or restricted suckling (RS) treatments. The breed make up of the treatment was slightly confounded with AR and RS having S: 2, 6; F1:1, 1; B1: 6, 2 and AIS: 1,1. Feeding of the cows was based on green fodder and concentrates. The calves received whole cows' milk by nipple pail (AR) or restricted suckling for a 30 minute period following milking (RS); both groups (AR and RS) were housed together and had free access to green forage and concentrates. Milking was by machine twice daily. Experimental data were collected for the first 92 days of lactation/calf growth, then milk feeding/suckling was stopped for both treatments.

Calves reared by restricted suckling gained weight faster (552"32 vs 370"32 g/d)and a greater proportion of weight was in the form of tissue (better condition score) as compared with artificial rearing. They consumed less milk (2.67 vs 3.04 kg/d) and had a much better conversion (4.97 vs 8.98) of milk into liveweight. Sahiwal cows gave more than double the quantity of milk when they suckled their calves after milking as compared to the artificial rearing system. The milk yield of AIS cows and their crosses was not affected by the calf rearing method.

KEY WORDS: Calf, restricted suckling, artificial rearing, cow performance, Bos indicus, Bos taurus, breeds

Pakistan has 17 million cattle (mostly Bos indicus breed) and about 14.3 million buffaloes (mostly Nili/Ravi milk type). Approximately 60% of the liquid milk consumed is from buffaloes and the rest from cattle. Apart from large colonies of buffaloes around the major cities, buffaloes and cattle are traditionally kept in small herds (3-5 heads) by smallholder farmers. The traditional management system employed by farmers uses the calf to stimulate milk "let down"; after hand milking is completed the calf is allowed to suckle the residual milk staying freely with the dam for a limited period of 15 to 30 minutes.

By contrast in herds owned and managed by institutions, such as the Military farms and Government experimental stations, calves are almost always removed from their dams a few days after calving and fed milk from open pails or occasionally nipple bottles.

Research in Latin America (Ugarte and Preston 1975; Alvarez et al 1980) and in Asia (Gaya et al 1977) has shown that the restricted suckling system is superior to artificial rearing in terms of both cow and calf performance. Total saleable milk yield is increased, mastitis is reduced and calves grow faster with less disease and mortality.

In view of the priority given by the Government of Pakistan to increasing milk production from cattle and buffaloes it was considered to be important to document the affect of artificial rearing compared with restricted suckling in both cattle and buffaloes. The experiment reported here was done with a mixed herd of Bos taurus and Bos indicus cattle.

The two treatments were: (AR) artificial rearing in which the calves were separated permanently from the dams and fed cows' milk from a nipple bottle; and (RS) restricted suckling where calves were suckled by their dams for period of 30 minutes after milking. Cows and calves were allocated alternately to the treatments after calving. The herd comprised a mixed population of Australia Illaware Shorthorn (AIS), Sahiwal (S), their first crosses (F1) and back crosses to the AIS (B1). The final breed make up of the treatment was slightly confounded with AR and RS having AIS: 1,1; S: 2, 6; F1: 1,1; and B1: 6,2, respectively.

During the first 5 days the calves were continually with their dams in order to consume the maximum amount of colostrum. On the sixth day they were separated and kept as one group in a semi-covered yard. On (AR) the calves were given whole cow's milk by nipple bottle twice daily up to 30 days and then once daily up to 92 days. On (RS) the calves were suckled by their dams for 30 minute periods after milking in the morning (4-5 am) and afternoon (2-3 pm). After 30 days the suckling frequency was reduced to once daily. After 92 days, suckling for (RS) and milk feeding for AR were terminated.

The cows were grazed from 8-12 am mainly on pasture but sometimes on crop residues. The remainder of the time they were in semi-covered yard with access to cut green forage or silage. They were fed 6.5 kg daily of the following concentrate mixture: cottonseed cake 25, mustard cake 5, wheat bran 20, maize gluten 20, rice polishing 15, molasses 13, urea 0.25, salt 0.25, mineral mixture 1.0). All the calves had free access to green forage and the following concentrate mixture (cottonseed cake 20, wheat bran 24, rice polishing 12, maize gluten 20, mustard cake 11, molasses 12, limestone 0.5, urea 0.25 and salt 0.25)

The calves were weighed within 24 hr after calving. Subsequently, body weight was recorded at weekly intervals. RS calves were weighed before and after suckling of milk in order to determine their milk consumption. The amounts of milk given to the AR calves were recorded daily.

Composite samples of the milk were analyzed on a weekly basis for fat (Gerber), protein and total solids (AOAC 1984). Milk for the AR calves was taken from the total quantity given at milking. For the RS treatment, samples were taken from the dam during the suckling process.

The circumference of the body (belly girth) was measured for all calves on a weekly basis. Liveweights taken weekly before suckling (RS) or milk feeding (AR) were used to calculate growth rate by linear regression of weight on age according to the method described by Steel and Torrie (1980).

Condition score was calculated as: 100 x [liveweight (kg)/ belly girth (cm)]. The rate of increase in condition score was calculated by linear regression of the weekly condition score on age.

The calves on the RS treatment gained liveweight 49% faster with 12% less milk consumption compared with the AR treatment (Table 1). The efficiency of converting milk into liveweight was improved by 80% in the calves reared by restricted suckling. The body condition score also increased at a significantly faster rate (17%) on this treatment. There were no apparent difference in the composition of milk consumed by the calves on the different treatments.

Interpretation of treatment effect on cow performance is made difficult by the confounding in breed and treatments (Table 2) and the fact that the milking potential of the AIS and its crosses (represented in greater number on the AR treatments) was very much higher than for the Sahiwal animals. Nevertheless, there were clear indications that milk yield in the Sahiwal breed was considerably increased on the RS treatment. There were no apparent difference in milk yield due to treatment in the AIS cows and their crosses. Cows on both treatments lost liveweight during the first 90 days of lactation and there was a slight tendency for the loss to be less in the RS treatment.

The faster growth rate of the RS calves despite their lower daily milk consumption implies that either they ate more concentrates and roughage or that the way in which the milk was consumed had a significant effect on the efficiency of its utilization. The calves on both treatments were kept in the same pen, therefore it was not possible to determine the relatives intakes of forage and concentrates. Nevertheless, the explanation of a greater solid food intake by the RS calves can be discounted since they had a relatively smaller belly girth circumference (and therefore reduced rumen liquid volume) relative to their liveweight than was the case for the calves reared artificially. If the RS calves had consumed more solid food than their AR counterparts then rumen size should have been greater.

The more likely explanation for the faster growth of the calves raised by restricted suckling is that the method of consuming the milk had a direct effect on the efficiency of its utilization. Such an explanation is in line with the report by Orskov (1983) that the efficiency with which a liquid bypasses the rumen via the oesophageal groove is directly influenced by the psychological status of the animal. When the young ruminant is suckled by its dam then there is 100% efficiency in the passage of milk directly to the abomasum. By contrast, when the animal is forced to consume milk from the bucket then the reflex action controlling the closing of the oesophageal groove is not fully elicited and much of the milk spills over into the rumen. In the present experiment, it seems likely that in the case of calves given milk from a nipple bottle, that much of the milk found its way into the rumen rather than to the abomasum. The efficiency with which nutrients are utilized by fermentation compared with gastric digestion is considerably less and this could account for the poor milk utilization efficiency in the calves reared artificially.

The other explanation that is frequently put forward for better milk utilization by calves on restricted suckling is that the residual milk is higher in fat as compared with the average milk obtained by hand or by machine. This explanation can also be discounted since there were no differences in the composition of the milk consumed by the calves on the two treatments (Table 1). In the case of RS treatments the milk samples were drawn during the suckling operation so as to obtain representative samples of milk that was actually consumed.

Table 1: Performance of calves reared by restricted suckling or artificial rearing

	Artificial	Restricted	Significance
	rearing	suckling SEM	level

Liveweight, kg
Birth	32.6	30.9 1.63	NS
At 92 d	64.4	83.1 3.12	.001

Belly girth at
92 d, cm	102.0	111.0 2.7	.04

Condition score
at 92 d*	63.3	74.0 1.4	.001

Daily weight
gain, g	370	552 32	.001

Daily increase in
condition score	0.19	0.33 0.023	.01

Milk intake, kg/d	3.04	2.67 0.097	.05

Milk conversion**	8.98	4.97 0.79	.01

Composition of milk
consumed by calf, %
Fat	4.09	4.22 .21	NS
Protein	3.55	3.62 .57	NS
Total solids	12.90	12.70 .28	NS

* Condition score is calculated as 100 (liveweight/belly girth). A higher value indicates less gut fill per unit liveweight and therefore more of the liveweight in the form of tissue.

The effects of RS on cow performance (Table 2) were inconclusive due to the confounding of breeds and treatments which occurred. The apparent increase in total milk production in the Sahiwal breed due to the suckling treatment is nevertheless in line with all other reports in the literature which show consistent increases in total milk yield due to calf suckling (Preston and Vaccaro 1989).

The increased milk production of the Sahiwal calves on the restricted suckling treatment was unlikely to be due to differences in feed intake since a relatively high allowance of concentrates was given and this was provided individually to each animal; roughages were group fed but it is unlikely that differences occurred or of they did that they would have explained the greater milk yield. The increased milk production was also not obtained at the expense of bodyweight since there was an indication that the rate of bodyweight loss in the cows was slightly less on the restricted suckling treatment. The suggestion from these results that the efficiency of milk secretion was enhanced in the Sahiwal breed because of the restricted suckling treatment merits much closer investigation.

Table 2: Performance of cows whose calves were either weaned at 3 days and then reared artificially; or sucked their dams for 30 minute periods following milking

	Artificial	Restricted	SEM	Significance
	rearing	suckling		level

COW PERFORMANCE:
Total milk, kg/d
AIS and Xsses	13.0	11.7	2.2	NS
Sahiwal	2.67	6.99	1.09	.04

Saleable milk*, kg/d
AIS and Xsses	10.0	9.1	2.16	NS
Sahiwal	-.66	4.26	1.16	.05

Liveweight change, kg/d
AIS + Xsses	-.402	-.299	.16	NS
Sahiwal	-.226	-.150	.12	NS

It can be concluded that rearing calves by restricted sucking of their dams, compared with artificial feeding of cows' milk from a nipple bottle, not only leads to faster growth rates but more importantly it results in a much superior efficiency of utilization of the ingested milk for tissue growth. There appeared to be no differences in the response of the Shorthorn breed and its crosses compared with the Sahiwal breed due to the suckling treatment. However, because of the confounding of breeds between treatments this part of the study should be repeated with larger numbers of animals and with careful balancing of breed according to treatment.

The authors are grateful to the Head of the Animal Sciences Institute, Dr. Karam Shah for making available the facilities for carrying out this experiment. Dr T R Preston was consultant to the UNDP/FAO Project with the Government of Pakistan, Animal Sciences Institute, when this research was done.

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