Workers at All fresh-CFL a modern milk processing plant in Nyambari, Kiambu County. [Fidelia Kabunyi, Standard]
Dear Dr Othieno
I have a dairy cow that is five months in-calf. The cow is being milked but off late, its producing yellowish milk that appears like colostrum. Is this normal at this stage of lactation? What factors determine the quantity and quality of milk from a cow. The cow is a jersey/fresian cross in its first lactation.
Kindly advise. [Ibrahim]
Dear Ibrahim, Thank you for reading The Smart Harvest and for your question. Milk is a white opaque fluid secreted by animals. Milk varies in colour from yellowish white to white. Milk is made up of water, fat, proteins and milk sugar or lactose. In addition, milk has little amounts of other substances like pigments, enzymes, vitamins and gases. Water constitutes 87 per cent while solids account for 13 per cent of milk. These individual components are normally written on the milk container. Milk colour has some commercial value as many people prefer yellowish milk, thinking it to be richer in cream (butter fat) than whiter milk.
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The yellowness of the milk is determined by the proportion of fat present. Milk colour is an important property that affects buyer’s choice. Other than colour, other aspects of milk that determine its value are the flavour and aroma. It is good to note that adulterated milk has funny colour.
So what determines colour and the quality of milk?
· Species and Breed
The milk yield and colour vary from species to species. The quantity of milk Holstein Friesian cows produce is more than that from Kenyan zebus. Dairy breeds will produce more milk than dual-purpose breed.
Among cows the amount of milk produced is relative to the body weight. Normally cows will produce milk that is equivalent to 8-10 per cent of their body weight. On the other hand, goats can secret milk equivalent to 20 per cent of their body weight.
Jersey breed milk is unique in many ways. It contains 18 per cent more protein, 20 per cent more calcium, 25 per cent more butterfat than milk from other breeds. This may explain the colour observed by Ibrahim.
· Frequency of Milking
When milk accumulates in the udder it sends a stimulus that gradually inhibits milk secretion. Frequent removal of milk by milking tends to favour more milk secretion and prevents mastitis. Research shows that milking cows three times a day increases milk production by up to 20 per cent but this must be tied to good nutrition.
· Gestation
In the first five months of pregnancy, the decrease in milk production in pregnant cows is comparable to non-pregnant cows. In the subsequent months the decline is however rapid in pregnant cows.
Towards the end of pregnancy, (when nearing drying off) there is a significant reduction in milk yield. This may be explained by the increasing nutrient needs of the foetus and the hormonal changes that the animal is undergoing. High amounts of estrogen and progesterone released lower milk letdown.
Other physiological status like when a cow is on heat or sick will also see a reduction in the daily yield of milk from a cow.
· Parity
Cows will increase their milk production with every pregnancy. This is attributed to their increase in body size and also additional growth of the secreting cells of dairy cows. This increases up to seven years. This is only possible with good udder health. Mastitis destroys milk secreting tissues and can significantly lower milk production.
· Ambient Temperature
Extreme weather condition are stressors to a dairy animal and will subsequently reduce milk production. At high temperatures, feed consumption is reduced while water intake is increased. This alters the milk quantity and colour by lowering milk fat content. Minimise any form of stress in lactating animals to boost milk yields.
· Udder health status
Udder is the milk secreting unit. When infected, there will be reduced milk production or the milk will be adulterated. Mastitis is a common udder disease that significantly reduces milk produced. Pus, blood and somatic cells can be found in milk from diseased udders.
· Diet
Feed is the raw material that goes into milk production. Inadequate feeds or poor-quality feeds will affect the quality and quantity of milk produced by a dairy animal. However, this should be viewed together with the other factors like breed, parity and gestation. A diet high in carotene (the pigment found in carrots and pumpkins) will result in yellowish milk.
