Newborn lambs depend entirely on the immune factors provided in the mother’s colostrum for their initial immunity ^[1]. For this reason, it is key to the survival and subsequent health of the lamb that she receives plenty of clean and high-quality colostrum from its mother during the first 2 days. Milk replacer (MR) cannot be used as a substitute for colostrum!

After this, if it is necessary to rear lambs away from their mother, a good quality MR can adequately substitute the ewe’s milk. It must be emphasized that calf MR are not suitable for use with lambs. This is because the composition of ewe’s milk is markedly different from that of cow’s milk ^[2]. Ewe’s milk has a much higher solids content than cow’s milk and is particularly high in fat. Lamb MR based on cow’s milk can be used to rear lambs successfully ^[3,4], as long as the MR is formulated such that it reflects the higher solids content of ewe’s milk.

The importance of curding

The protein in ewe’s milk, as in cow’s milk, consists of casein and whey proteins. Caseins are the proteins that form curds in the young animal’s abomasum or “stomach”. Once inside the stomach a combination of acids and enzymes (rennet), produced by the stomach wall, transform the milk within minutes into a solid plug or curd. This gives suckling-induced enzymes (lipases) produced by salivary glands and deposited into saliva and in the stomach a chance to properly digest and release lipids and other nutrients – the curd really acts as a slow-release mechanism. The nutrients then slowly, together with whey protein squeezed from the curd by stomach contractions, pass to the small intestine, where they will be absorbed into the blood. The curding process in the newborn ruminant, which has evolved over millions of years, performs an important function in milk digestion and nutrient absorption.

In the newborn the ability to secrete digestive enzymes in saliva and from the stomach is high, whereas the secretion of pancreatic enzymes and bile into the small intestines is low ^[5,6]. Over the next 3 to 4 weeks this process slowly reverses and digestion in the small intestine becomes more important (Fig. 1) – this coincides with the lamb starting to eat more solid feed.

Types of Lamb MR

Because of the importance of curding, lamb MR based on whole milk powder (WMP) or skim milk powder (SMP), both containing casein, are preferrable. Unfortunately, due to a high demand for WMP and SMP in nutritional formulas for human consumption, their availability and price increasingly make them less available for use in MR. This means that different lamb MR are now available:

1.      WMP-based lamb MR, such as Anlamb™, are made from 100% bovine milk-derived powders and are formulated to contain a nutrient profile almost identical to raw whole milk, containing both milk casein and milk whey protein. It has milk fat as the sole fat source – milk fat is the only fat that contains butyrate, which is important for rumen development.

2.      SMP-based lamb MR contain the same milk proteins (casein and whey protein), but must have added fat, because SMP contains less than 1% milk fat. Ideally the added fat is from a milk fat source. However, it is not uncommon to use a mixture of milk fat and cheaper plant oils or just plant oils and often also some of the milk protein is replaced with plant-derived protein.

3.      Whey-based lamb MR, which contain milk whey proteins (no or very little caseins). Sometimes the protein may be partially substituted with cheaper plant protein. The fat is usually a mixture of milk fat and cheaper plant oils.

Plant-derived protein and fats (or oils) are not desirable in young animals (< 3-4 weeks old) as they are difficult to digest.

Benefits of a WMP-based lamb MR

In a recent New Zealand study ^[3] with 206 East Friesian 2 to 5-day old male lambs feeding a WMP-based lamb MR was compared with feeding one that had a reduced casein content and increased whey protein content. In addition, it also contained a small (10%) amount of plant protein and all the fat was plant-derived.

Key findings from the study, indicated that feeding the WMP-based lamb MR resulted in:

-        The highest growth rate (thus, reaching their target weaning weight sooner);

-        Lower incidence of scours (by 88%);

-        Lower incidence of Pink Eye (by 46%);

-        Reduced use of total antibiotics (by 57%) during the trial;

-        Lamb mortality did not differ between the 2 groups.

In another recent New Zealand study with 294 East Friesian lambs, the importance of a curding lamb MR was studied. Lambs were fed a WMP-based lamb MR (i.e., curding) or a whey-based lamb MR (i.e., non-curding) ^[4]. Even though both MR were milk-based, the curding WMP-based lamb MR again resulted in increased daily growth rates, improved health, resulting in less overall use of antibiotics and anti-inflammatories and this time mortality was significantly lower in the WMP-baser MR group. These are all factors that reduce rearing costs and improve animal welfare.

The incidence of bloat was not measured in the above studies. Abomasal bloat is not well understood and can have a number of causes, including a slow abomasal emptying ^[7]. However, this does not mean that curd-forming MR lead to increased abomasal bloating.  In a study with calves, fed whole milk (i.e., high curding) or a whey-based MR or a whey-based MR with soy-protein (i.e., both with low or no curding), the abomasal emptying rate was the slowest in the 2 low/non-curding whey-based MR ^[8]. It was concluded that the slow emptying rate was most likely linked to a higher osmolality in the two whey-based MR.

In conclusion

It is important to allow the lamb to suckle high-quality colostrum during the first 2 days. Subsequently, feed, ideally, a high-quality WMP-based lamb MR that allows for curding to occur in the abomasum, during the first 3 to 4 weeks.  Avoid lamb MR that contain plant-derived protein and fat or oils during this time.

Find out more about the benefits of Anlamb, click here

References (copies of papers available upon request):

1.       Agenbag B, Swinbourne AM, Petrovski KR and van Wettere WHEJ. Lambs need colostrum: A review. Livestock Science 251: e104624.

2.       Jenness R. 1986. Lactational performance of various mammalian species. Journal of Dairy Science 69: 869-885.

3.       McCoard SA, Hea S-Y, Karatiana D, Triggs J and Macdonald T. 2021. Comparison of milk replacer composition and effects on growth and health of preruminant lambs, and health-associated costs of artificial rearing. Applied Animal Science 37: 176-185.

4.       McCoard S, Ryrie J, MacDonald T, Hea S-Y., Pacheco D and Stevens D. Impact of casein- versus whey-based milk replacers on growth and health of lambs artificially reared lambs. New Zealand Journal of Animal Science and Production 81: 22-28.

5.       Hamosh M. 1979. A review. Fat digestion in the newborn: role of lingual lipase and preduodenal digestion. Pediatric Research 13: 615-622.

6.       Edwards-Webb JD, Thompson SY. 1977. Studies on lipid digestion in the preruminant calf. 2. A comparison of the products of lipolysis of milk fat by salivary and pancreatic lipases in vitro. British Journal of Nutrition 37: 431-440.

7.       Burgstaller J, Wittek T and Smith GW. 2017. Invited review: Abomasal emptying in calves and its potential influence on gastrointestinal disease. Journal of Dairy Science 100: 17-35.

8.       Constable PD, Ahmed AF and Misk NA. 2005. Effect of suckling cow's milk or milk replacer on abomasal luminal pH in dairy calves. Journal of Veterinary Internal Medicine 19: 97-102.