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This article was published in 1988
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Dairy Goats - Constraints to Milk Production
HC GRANT-FROST, B.V.Sc Veterinary Inspector MUDGEE
INTRODUCTION
The first milking goats arrived in Australia with the early settlers. They provided milk during the long voyage and later to the colonists. They were a popular choice as the goat is relatively small, hardy, and thrives on natural vegetation and herbage.
Since those days there have always been dairy goats in Australia. In more recent years goats, milk has been in such strong demand that there has been an upsurge in organised goat dairying. Today each major Australian population centre supports an expanding dairy goat industry.
This demand exists because goat milk is more easily digested than cows milk. Also, many people especially children, are allergic to cow's milk, but can readily digest goats milk as the protein fraction differs and does not as readily cause allergic reactions.
An average dairy goat in Australia will produce 2-3 litres of milk per day over a lactation period of 7-10 months. Production depends on the breed, as well as the care and nutrition each goat receives. Under selective Breeding in optimum conditions, far higher production levels are possible. There is an increasing demand for goat milk products such as yoghurt and cheese.
There are four major breeds of milking goats in Australia. These are the Saanen, Anglo-Nubian, British Alpine and Toggenburg. Crossbred animals are also becoming popular in commercial herds.
PRODUCTION PROBLEMS
To illustrate some of the factors which influence milk production, problems encountered in one typical dairy goat herd are described.
General The milking herd consists of 60 Saanen does, which are machine milked twice a day in a 10-a-side Herring-bone dairy. Management and milking hygiene are excellent. Does in the herd kid about 15 months of age and are introduced into the milking herd about 10 days after kidding. Average milk production is approximately 3 litres per day, and lactation averages 9 months, followed by a dry period of about 8 weeks. Feeding consists of grazing on improved pasture of oats, white clover and rye grass, supplemented by daily access to good quality hay, as well as browsing. About one kg of oaten grain is fed during each milking.
MASTITIS
This is the most common disease problem in the herd, especially since a high proportion of clinical cases are maiden does, coming into the milking herd for the first time. More often than not only one half is affected by swelling, heat, pain and reduced milk production. Abnormalities in the milk are not always evident, and this is an important point of difference from Bovine mastitis, where clots, discolouration etc. are one of the first signs of disease. Blood et al. (1) state that in the goat severe inflammatory changes can occur in the udder without any apparent abnormality in the milk. In fact these authors consider it reasonable to define mastitis as a disease characterised by the presence of a significantly increased leucocyte content i.e. Somatic Cell count of more than 1 x 106. Culture of milk is the best method of diagnosis. Bacteria isolated from mastitis does in the herd have included Bacillus cereus, Staph. aureus, Staph epidermidis, Pseudomonas aeruginosa and Streptococcus sp. However, false negative cultures can be obtained due to the fact that bacteria may only be intermittently shed from some mastitic udders.
The RMT is also a useful diagnostic aid. Only the ++ and +++ reactions are positive in goats.
Another useful aid to diagnosis is the Petra Film; this is a disc containing a bacterial growth medium. Suspect milk is placed on the disc, which is then incubated in an ordinary oven for 24-48 hours. The presence of bacteria is indicated by coloured spots on the plate.
Treatment consists of the infusion of antibiotic into the affected gland. Systemic antibiotics are used only in those few cases where does show systemic involvement 'Dry Cow' preparations do not appear to have a significant effect on the number of infected udders at kidding.
HARD UDDER
Baxendell (3) defines this condition as Afebrile Post-parturient Udder Oedema. This is a gross, hard enlargement of the udder, which always occurs in recently kidded does, from the day of parturition until softening about 6 weeks later. The swelling is always bilateral. Milk production is severely reduced, but the milk shows no other abnormalities. The cause of the condition is unknown, but genetic or hormonal factors have been suspected. CAEV may also be involved. Goats showing Hard Udder are always affected at their first and then all subsequent lactations. Bacteriology on milk is always negative.
Treatment of Hard Udder has in the past consisted of systemic injections of a Phosphorus preparation (Phosfort 5% ®) and Vitamin D3 (Duphafral D3 1000 ®) - (Baxendell (2)). Results have, at best, been variable in this herd. More recently, however, excellent results have been obtained with intramuscular injection of a Phosphorus - Vitamin B12 combination (Coforta 10% ®). Softening of the udder has occurred within days of this treatment, with return to normal milk production at the same time. Furthermore, the injection of 5 ml of this product a few days prior to kidding has prevented the appearance of 'Hard udder' in previously affected does.
UDDER OEDEMA
This condition occurs in the first few days after kidding (it may be present before parturition) and is similar to the oedema seen in parturient heifers. Swelling is bilateral, but milk production is near to normal. The swelling reduces after each milking. Treatment is by twice daily injections with a diuretic until the swelling subsides.
MILK TAINT
There are many reasons for goat milk not being 'sweet' although there is disagreement as to whether it should taste the same as cows milk or have a distinctive flavour of its own. Causes of taint include:
Poor Hygiene and Animal Husbandry. Dirty bedding, milking utensils and surroundings.
Slow Cooling of Milk. Milk should be refrigerated immediately milking is completed. Vessels should be sealed to prevent tainting from other foodstuffs.
Failure to discard foremilk.The first 2-3 streams of milk should always be discarded.
Genetic factors.In Norway, certain lines of goats are bred which produce milk of a 'flavour' that is considered desirable for cheese production.
Bucks. Presence of bucks has been blamed on does producing tainted milk.
Food Taint. Silages, turnips, kale, and garlic.
Poor Health. Goats in poor health are more likely to produce milk of an abnormal composition or taste.
DISCUSSION
At the present time the Dairy goat industry is relatively unregulated as regards to milk composition and quality. The majority of producers would prefer the present status quo to continue, since consumers of goat milk and goat milk products prefer these to remain as 'natural' as possible i.e. not pasteurised etc. Goat dairymen and women thus have to be even more aware of their responsibilities to produce a high quality, healthy and wholesome product, so as to counter the inevitable push from Health Departments for compulsory regulations and treatment of milk and milk products which apply to the Dairy cow industry.
In August 1987 a workshop on Quality Standards for the NSW Goat Milk Industry was held, and attended by about 60 people. This meeting endorsed the model for self-regulation put to them by Paul Greenwood, Livestock Officer (Dairy Goats). This involves the establishment of a seal of excellence for milk producers who meet strict industry microbiological and chemical standards. A sub-committee was elected and asked to establish standards suitable for certification of milk being of premium quality at the farm gate. The establishment of a certification scheme is seen as vital in the fight to prevent the introduction of compulsory pasteurisation. The National Health and Medical Research Council is likely to come out in favour of compulsory pasteurisation, and it is up to NSW producers to support a certificate on system to protect the raw milk market by producing top quality milk.
REFERENCES
- Blood, Radostits and Henderson - Veterinary Medicine, 6th Ed. 451
- Baxendell SA, Post - Graduate Committee Control and Therapy No.1614
- Baxendell, SA - Vade Mecum Series B, No. 9 Post - Graduate Foundation in Veterinary Science