Livestock Research for Rural Development 14 (6) 2002

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A note on the effect of molasses/urea lick blocks  on the production of milk and corporal conformation of dairy cows maintained in the urban environments of Iztapalapa, Mexico City: A case study

L Arias, M López, H Losada, J Cortés, J Vieyra, R Soriano and D Grande

Sustainable Agricultural Development Area. Department of Biology of Reproduction.
Division of Biological and Health Sciences, Autonomous University Metropolitan-Iztapalapa.
CP 09340. Mexico City, Mexico


Multi-nutritional blocks (molasses /urea) were manufactured and fed to Holstein cattle in a stable located in Iztapalapa in the East of Mexico City.  The aim was to improve low milk yield and poor corporal conformation caused by unbalanced feeding.

Total milk production of the stable increased from 358 litres/day to 418 litres/day, with a slight indication of improved corporal conformation.

Key words: Cattle, milk production, multi-nutritional blocks


The use of molasses/urea blocks for supplementing livestock has been documented in beef cattle (Sansoucy 1989; Waliszewski 1994; Araquey and Cortes 1998) in sheep and goats (Mejía et al 1991; Dinh Van Binh and Preston 1995). However, their use in milk production has been little investigated (Chen Yuzhi et al 1993). In the small-holder milk production systems of Iztapalapa, wastes of food industry and markets are the basis of the diet (Losada et al 1996) with the result that a frequently restrictive factor is the supply of protein. A possibility to improve this deficiency and to diminish production costs would be by supplementation with molasses/urea blocks.

The objective of the present study was therefore to study the response to supplementation with blocks of molasses/urea in a herd of cows maintained under commercial conditions and fed with vegetable wastes.

Materials and methods 


The production unit was a stable located in the Iztapalapa delegation, situated in the eastern portion of the Valley of Mexico, in what was previously the Lake of Texcoco, and which occupies an area of 117 square kilometres at an altitude of 2240 masl. The predominant climate is temperate sub-humid with high humidity, and temperate semi-arid. The mean annual temperature ranges between 12 and 16 °C, with an average precipitation of 1500mm, falling in the summer and winter (Anon 1992). The population of the area is 2.5 million people, equivalent to a residential density of 21 persons per km². Based on data of mean incomes, the eastern part of the city is classified as extremely poor (Anon 1992), and the principal economic activities are manufacturing, commerce and services. The “Central Food Depot” of Mexico City is located in the centre of Iztapalapa, covering 328 ha. This area receives and sells 40% of the national agricultural produce for consumption in the city and neighbouring states (CEDA 1993).

Animals and management  

The stable included a herd of 28 cows in production, 3 heifers and 1 bull of the commercial Holstein breed. The cows had an average of 550 kg live weight and were kept loose in an open sided building annexed to the house of the producer. The pen had a cement floor and there was free access to water and feed. The lactating animals were milked by hand twice a day at 8:00 am and 3:00 pm when they were tied by chains to the feed trough, later being released to remain free in the pen.


The animals received a diet made up of cauliflower leaves coming from the Metropolitan Central Food Depot, maize silage, sun-dried lucerne and brewery waste (Brewer’s grains) as forage sources and tortilla, bread scraps, coconut meal and wheat bran as the source of concentrate.

Multi-nutritional blocks  

The approach to define the ingredients for block manufacture was the access to the inputs by the producer. The blocks contained (% air dry): sugar cane molasses 46, maize stover 23, urea 9, common salt 4, cement 4, lime 4 and water 10. For 100 kg of block, the urea (9 kg) was first dissolved in 5 litres of water and this solution then added to, and mixed with, the molasses (46 kg). The maize stover (23 kg) was chopped and mixed with the molasses/urea solution. The salt, cement and lime were dissolved in the remaining 5 litres of water and the resulting suspension added to the mixture of stover  and molasses/urea. The final mixture was poured in wooden block moulds of 30*30*30 cm lined with acrylate sheets and pressed during a period of 5 minutes. The resulting blocks were allowed to dry at ambient temperature during 24 h and were then removed from the moulds and stored at ambient temperature for a 6 day period before being given to the animals. Each block had an average weight of 20 kg. The blocks were offered to all the animals in the pen after morning milking during a period of 2 h. One block was consumed on average every two days.

Duration of the experiment, variables and statistical analysis  

The study was carried out over a period of 6 weeks. Milk production from the stable was measured during three periods: the first two weeks were considered as pre-experimental yield, the three following weeks were evaluated as the experimental test and the remaining week was considered as the post-experiment yield. The weight of the animals was calculated using a metric tape according to the procedure described by Bath et al (1985). Changes in corporal conformation were assessed in terms of a classification scale of 1 to 5 (1 poor  to 5 excellent) following the procedure designed by Wildman et al (1982) and Brawn et al (1985). The proximal composition (DM, crude protein and fibre) of the diet components was determined following  conventional procedures (AOAC 1990).  

Data regarding milk production and corporal conformation were analysed according to the procedures described by Daniel (1991).

Results and Discussion   

The blocks were observed to be of good quality (ie: did not absorb moisture, did not become mouldy and did not lose shape when exposed to sunshine). 

Table 1. Dry matter (% of air-dry), crude protein (% N*6.25 in DM) and crude fibre (% in DM) of the feeds offered



Crude protein

Crude fibre

Cauliflower leaf




Maize silage




Sun-dried lucerne




Brewery waste




Tortilla* scraps




Bread scraps




Coconut meal




Wheat bran




*  Mexican bread

The cauliflower leaf and brewery waste had lower content of DM and higher crude protein than the maize silage (Table 1). Tortilla scraps were low in protein with very low fibre. The bread scraps had a medium level of protein and almost no fibre.  The other ingredients (Lucerne hay, coconut meal, wheat bran) had values similar to those in the literature (Gohl 1981). 

Table 2. Feeds offered to the cows in the commercial stable of Iztapalapa

Total, kg

Per animal, kg

Cost, Pesos/animal

Cauliflower leaf *




Maize silage




Sun-dried lucerne




Brewery waste




Tortilla scraps




Bread scraps




Coconut meal




Wheat bran








* Only includes price of transport 

The major part of the diet was formed by the cauliflower leaves followed by brewery waste and maize silage (Table 2). Wheat bran was the major source of concentrate feed. The highest costs corresponded to the brewery waste, maize silage and wheat bran. 

Estimates of total milk of the stable, production per animal and the corporal conformation (Table 3) indicated a positive effect due to the blocks. Total milk produced in the stable increased from a mean value of 358 litres to 418 litres with the use of the blocks. There was a slight improvement in the conformation of the animals when they were supplemented with molasses/urea blocks. 

Table 3. Total milk production for cows supplemented with molasses/urea blocks in Iztapalapa
Week No







Supply of block

No block

No block




No  block

Total milk of the stable, l/day







Milk/cow,  litres/day







Body conformation







The results obtained in the present study showed a positive effect of the supply of the molasses /urea block on the production of milk that rebounded in a bigger quantity of milk for the sale and bigger economic earnings for the producer. In spite of this situation, the technology was not assimilated by the proprietor, as the cheese maker that purchased the milk complained that a bigger quantity of milk was needed  for the production of cheese, during the period when the blocks were fed. A detailed evaluation of this hypothesis constitutes the object of future research.


The authors wish to thank Mr Don Crisóstomo Tapia Aguilar for the access to his stable that made feasible the present study; and the authorities of the Metropolitan Autonomous University for the facilities. 


Anon 1992 Instituto Nacional de Estadística, Geografía e Informática Cuaderno de información básica delegacional Iztapalapa, Mexico. 

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Received 28 July 2002

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