3. Feeding

The purpose of this section is to provide guidance on best practice for feeds and feeding management required for young lambs to support their survival, growth, health and wellbeing. The welfare criteria and indicators associated with the Welfare Principle of a “Good Feeding” as described by Richmond et al. (2017) are shown below. These may be useful animal-based indicators of good feeding practices during rearing.

Good nutrition is one of the easiest strategies to support health, production and welfare of lambs. It is important to note that the growth performance and health of lambs will be influenced by many factors other than the amount of milk or milk replacer offered. Such factors include, breed, birth rank (single, twin, triplet etc), quality of the ingredient used in milk replacer formulations, the frequency of feeding, animal health issues, stocking density, the amount and quality of starter diets (solid feeds) and rearing environment (e.g. climate). Nutrition provides fuel for growth and development, and is a key determinant of the immune response. Undernutrition, or inadequate nutrition, can impair growth and development including immune function, with lifelong consequences for health, productivity and welfare.

Newborn ruminants have 3 critical periods affecting their immune system in the first 3 months of life: 

1. Colostrum feeding 

2. Milk feeding 

3. Weaning

3.1 Colostrum Feeding 

Colostrum is the first milk produced by the ewe and has high levels of nutrients, bioactives, energy and immunoglobulins which play crucial roles in defence against external pathogens. It is essential that lambs receive an adequate amount of colostrum within the first few days of life. This is because lambs are born with no natural immunity as the ruminant placenta prevents transfer of immunoglobulins from the dam to the fetus. These immunoglobulins protect lambs until their own immune systems are fully functional which is not until they are 3-4 months old. 

The amount of immunoglobulins within the colostrum and the concentration of nutrients decreases as the time post lambing increases. Further, the gut of the lamb loses the ability to absorb immunoglobulins from colostrum over the first day of life. Therefore, consumption of sufficient colostrum soon after birth is critical. Insufficient neonatal absorption of colostral immunoglobulins within the first day of life is associated with failure of passive transfer of immunity, leading to increased risk for neonatal diseases, mortality and lasting negative effects on health, longevity and performance. Higher mortality and morbidity rates have been observed in colostrum deprived lambs (up to 80%) compared with colostrum-fed lambs (up to 20%).

Recommended Colostrum Feeding Regimes 

· Data generated to date from our research indicates good levels of colostral transfer when lambs remain on the ewes for at least 48 hours. 

· It is essential for lambs to get sufficient colostrum early (within 6-8 hours of birth). The colostrum must be of good quality, and continue to be given for at least 2 days, preferably 3-4 days. 

· If lambs are removed from the mother at birth, it is essential to feed gold colostrum (first colostrum produced in the udder on the day of birth) on day 1, followed by a transition from colostrum to milk by day 4 (mixing gradually). 

· If they need to be fed artificially, ideally colostrum would be fed at a level of 15% of birth weight split into 5-6 feeds for the first few days.

· If fresh sheep, goat or cow colostrum is used, it is essential to ensure the colostrum is of good quality (Brix value greater than 22; a Brix meter is available from veterinary supply stores), and that it is stored appropriately to minimise microbial contamination. Colostrum must be mixed well (the components can settle during storage) and warmed to body temperature prior to feeding. Colostrum can also be frozen in small quantities and thawed (do not microwave!) in warm water, mixed well and fed warm. Powdered colostrum is also available from rural supply stores for use when fresh colostrum is not available. 

· Quality will decline substantially within 24 hours even if refrigerated, so prioritise feeding the freshest colostrum to the youngest lambs for best results. 

 · Experience in the dairy sheep industry indicates that hoggets often have very thick colostrum on day 1 of lactation which can be hard for the lambs to extract from the udder. Therefore, extra care is required to ensure that newborn lambs from hoggets receive sufficient good quality colostrum. 

 · It is also important to remember that competition for the udder between littermates (i.e. in triplets and quads) or poor mothering ability and/or ewelamb bond, can affect the ability of all lambs to receive sufficient colostrum. It is important to carefully check newborns for signs of hunger and if required, manually feed colostrum.

3.2 Milk Feeding 

 The newborn relies completely on milk to provide the nutrients and energy required to support growth and development. At birth, the rumen is nonfunctional so the small intestine plays a key role in driving nutrient metabolism, immune function and thus survival and growth until the rumen is fully developed. It is essential that lambs receive adequate levels of milk. In naturally reared lambs, competition between littermates (e.g. triplets and quads) and poor lactation performance of ewes as a result of underfeeding and/ or animal health issues, can reduce milk intake. In such cases, lambs may require assistance with feeding in the first few days of life, or artificial rearing. 

There are many different options for milk feeding of artificially-reared lambs from restricted milk feeding to ad libitum milk feeding systems with both manual and automatic feeding equipment. Explore which system fits your budget, facilities, staff availability and skill level of the staff you have available (do this in advance of the lambing season so you can be prepared).

General key points: 

· Always ensure milk replacer is prepared and fed fresh. 

· Feed warm milk replacer (skin temperature, i.e. no more than 37o C), especially to very young lambs as this reduces the requirement to partition energy towards heat production. Mix to a consistent temperature for each feed. 

· Always follow the manufacturer’s instructions for milking of milk replacer and do not mix at levels below the recommendations. It is important to note that if an instruction states “200g/L”, this means 200g of powder made up to a total of 1 L of reconstituted milk replacer. Milk replacer can be concentrated (up to no more than 250 g/L) to reduce milk volume and increase nutrient delivery to the lamb especially in restricted milk feeding systems. 

· Do not over feed lambs – a maximum of 350ml per feed depending on the size of the lamb. Monitor the stomach of the lamb and stop feeding if the stomach begins to protrude beyond the ribs. Overfeeding can cause animal health issues such as scours and bloat (see Chapter 05, Animal Health). 

· Ensure all equipment is thoroughly cleaned with warm soapy water and rinsed after use. 

· Always feed lambs either standing or held in a position where their head is in the natural position when feeding naturally (see photos below). Do not place the lamb on its back and feed like a human baby. This can cause milk to go into the lungs and for the lamb to develop pneumonia or drown. 

· Always ensure ad libitum fresh water is available, even when feeding milk.

3.3 How much milk to feed? 

The amount of milk fed, will largely depend on the feeding system (e.g. restricted versus ad libitum milk allowance) and equipment (e.g. bottles/cafeteria vs automatic feeder) used. In general, it is recommended to feed lambs milk at a minimum of 20% of their birth weight (e.g. 1L per day for a 5kg lamb split into multiple feeds) to meet the minimum requirements for growth. It is advisable to weigh lambs on entry to the rearing unit to determine how much milk they should be fed if individual bottle feeding. 

This can be achieved by using a set of small scales with a box on top or putting the lamb in a bucket on its rump (do not leave in this position for more than 1 minute) and using a hand-held luggage or fish scale, or in a container placed on top of a flat scale (see photo insert for ideas). In general, the more milk a lamb is fed, the faster it will grow. However, care must be taken not to overfeed lambs when feeding with bottles or cafeteria feeders as this may cause scours or bloat (see Chapter 05, Animal Health). As stated in the previous section, a general rule of thumb is that no more than 350ml of milk should be offered in a single feed to bottle-fed lambs. 

3.3.1 Study 1 

Restricted vs ad libitum milk feeding systems? 

International studies have shown that ad libitum feeding can increase growth rates compared to restricted milk feeding but effects on post-weaning performance of lambs grown in pasture-based production systems had not been evaluated. 

In our MBIE-funded research program, we undertook a study to compare the performance of artificially reared lambs from two systems:

 1. Ad libitum milk feeding for 5 weeks followed by gradual weaning over 7 days (group 1), and

 2. Restricted milk feeding (20% of entry body weight per day) with a 3-week weaning process to wean at 4 weeks (group 2).

Thirty (n=15/group) mixed sex single and twin-born Romney x East Friesian lambs of 2-4-days old (average weight of 5.2 kg, range from 2.8 – 7.7kg) were enrolled in the study and reared using automatic feeders where individual intake was recorded. A commercially available 100% milk protein-based milk replacer (25% crude protein, 25% fat) was used. Concentrate starter, chopped meadow hay and water were available ad libitum during rearing. Lambs were reared indoors in a temperaturecontrolled room (~18o C) that was well ventilated, and lambs were managed in 3 x 6m pens on kiln dried untreated pine wood shavings.

 Lambs in group 1 were weaned using a system where milk allowance was reduced by 14% per day (programmed for each lamb using a computer-controlled system) to enable weaning over a 7-day period by the end of week 6. Milk allowance of group 2 was restricted to 20% of their initial body weight (on trial entry) offered in 4 equal periods during the day. They were weaned over 3 weeks by reducing milk replacer allowance by 25% per week (computer-controlled) with complete weaning at the end of week 4. This system was designed to mimic the restricted milk-feeding and weaning system in our other studies (see Chapter 04, Solid Feeds and Weaning).

One week after weaning (week 7 for group 1 and week 5 for group 2), the lambs were moved outdoors onto a ryegrass-white clover mixed sward pasture with shelter available. Solid feed supplements (concentrate and hay) were gradually removed over 10 days by week 9 of rearing. The animals were monitored until 18 weeks of age. All lambs were vaccinated against clostridial infections at week 4 and a booster provided at week 8. Anthelmintic was administered to all lambs 2 weeks after moving onto pasture and every 3 weeks thereafter to control internal parasites. Average milk intake of the ad libitum group pre-weaning was 91 L (range of 63-107 L) per lamb compared to 21 L (range of 12-26 L) per lamb in the restricted group. All lambs were healthy during the trial with minimal antibiotic use in both groups.

 Pre-weaning growth rate was much higher in the ad libitum compared to restricted group which reflects the greater milk intake. Post-weaning growth rate however did not differ between the groups. These differences in growth rate were reflected in the live weight profile, with a divergence in growth up to 6 weeks of rearing, with these live weight advantages remaining at 18 weeks of age. The cost to rear the lambs in the ad libitum group was higher due to the greater level of milk intake (91 vs 21 L per lamb on average) and the extra labour associated with care of the animals for a further 2 weeks of milk feeding prior to weaning.

The long-term benefits of ad libitum vs restricted milk feeding systems on growth, health and meat/milk production have not been quantified. The selection of feeding system depends on multiple factors such as the availability of skilled labour, capital costs (sheds, pens, automatic feeders etc.) and needs to be considered on a farm by farm basis. Furthermore, the availability of good quality feed post-weaning is an important consideration as lambs weaned at lower live weights will require greater post-weaning growth rates to achieve target weights for hogget mating (if used) or to reduce the time to slaughter (meat production systems).

 3.4 Which milk replacer to use?

There are wide range of lamb milk replacers commercially available. These vary in quality and price. The high cost of milk proteins has driven the development of cheaper formulations of lamb milk replacer. These formulations use whey proteins (by-product of cheese making) and/ or vegetable proteins and oils as cheaper alternatives to casein milk proteins and milk fat. Spray-dried milk proteins are recommended for formulation of milk replacers. Some research trials have suggested that non-milk protein sources such as soy protein can be used but high inclusion rates (up to 40%) can depress growth and ad libitum feeding should be avoided due to sedimentation issues with inclusion rates above 30% soy bean concentrate or full-fat soy flour. Most published research evaluating lamb milk replacer protein sources on lamb performance are over 30 years old and have focused on soybean protein. Inclusion of hydrolysed wheat protein as a cheaper alternative to soy protein is not common in commercially available milk replacer.

 We have undertaken two commercial-scale trials (at least 100 lambs per formulation) to evaluate the impact of substituting of high-quality casein protein with whey protein (Study 1) or hydrolysed wheat protein and whey protein (Study 2).

3.4.1 Study 2 

100% milk protein (casein-based) and fat vs. milk protein (whey) + hydrolysed wheat + vegetable oil

In study 1, we compared a 100% milk protein commercially available milk replacer made from 100% milk protein and fat (mostly casein with some whey protein; 100% milk protein and fat; MR1) with a commercially available milk replacer containing milk protein (mostly whey with a very small amount of casein), hydrolysed wheat protein and 100% vegetable oil (MR2). East Friesian 2-3-day-old cross-bred mixed-sex lambs were randomly allocated to eight replicated pens (16-20 lambs/pen per treatment). Milk replacer was mixed at 230g/L and was fed ad libitum using automatic feeders. Concentrate starter diet was freely available and intake did not differ between the groups. During the first three weeks of rearing (study period), lambs fed MR2 compared to MR1 had lower growth rates independent of birth rank, i.e. single, twin, triplet, greater mortality, required greater antibiotic treatment and had poorer feed conversion efficiency.

 3.4.2 Study 3 

100% milk protein (casein-based) and fat vs. milk protein (casein + whey) + hydrolysed wheat + vegetable oil

In this study we compared a commercially available 100% milk protein (casein; MR1 – the same formulation used in study 1) formulation with a commercially available formulation containing casein, whey and hydrolysed wheat protein and vegetable oil (MR2). For each formulation. Male East Friesian 2-4-day-old lambs were randomly allocated to eight replicated pens per treatment (10-12 lambs per pen). Milk replacer was mixed at 230g/L and was fed ad libitum using automatic feeders. Lambs were given free access to hay but no concentrate starter feed was offered.

 Overall, lamb growth was lower, and a greater percentage of lambs failed to reach the minimum weaning weight of 13.5 kg by 5-6 weeks of age (16 vs 4%) with MR2 compared to MR1. Mortality was similar, as was milk replacer intake, but poorer feed conversion efficiency was observed in MR2 compared to MR1 lambs. Incidence rate of several health issues were also greater in lambs fed MR2 than MR1: 7.6 times higher rate of scours, 1.9 times higher rate of pink eye, 2.5 times higher rate of pneumonia, 3.7 times higher rate of external infections, and 12.6 times higher rate of adverse behaviours such as navel sucking. As a result of these health issues, antibiotic use was 2.4 times higher in lambs fed MR 2 than MR1 as were the costs for animal health-related interventions.

Antibiotic use is an indicator of animal health and welfare and reducing antibiotic use is desirable in modern markets. Therefore, we also looked at the performance of the lambs not treated with antibiotics. Growth rates of lambs fed the milk replacer containing the hydrolysed wheat and whey protein and vegetable oil was reduced. This was associated with a lower proportion (48 vs 73%) of lambs that reached a minimum 13.5 kg live weight (commercial target for weaning).

The digestive system of the young ruminant is poorly developed at birth and can only digest a limited amount of carbohydrates, fats and proteins. The results of these studies illustrate that very young lambs have greater growth and better health when fed milk replacers formulated with 100% milk proteins (casein-dominant) and that milk replacer formulations containing mostly whey protein, or a combination of whey and hydrolysed wheat protein should be avoided. The impact of variable inclusion rates of these cheaper milk protein sources on animal performance has not been scientifically evaluated and requires further study.

It is interesting to note that in this study, a commercially available compound that claimed to prevent scours and optimise growth in young livestock, was available for all lambs. The incidence rate of scours was 23.5 vs 3.1 in lambs fed MR2 than MR1. Therefore, there was no evidence that this compound prevented scours in the lambs.

The key message from this work is that selection of milk replacer for lamb rearing should consider not just the cost, but also health and welfare implications of slower growth, increased use of antibiotics, impact on mortality and costs associated with animal health interventions when feeding different milk replacer formulations. Long-term benefits or trade-offs on lifetime performance have not been studied.

Does casein-based milk replacer cause abomasal bloat?

One health issue commonly observed in artificial lamb rearing systems is abomasal bloat. Anecdotally, claims have been made in both small and largescale rearing systems that casein-dominant milk replacer formulations cause bloat. The potential cause is thought to be the absence of curd formation that occurs in formulations based on whey or vegetable proteins prevents bloat. In both the studies described above and all other studies undertaken in our research program, no cases of abomasal bloat were observed with any of the milk replacers used. This suggests that factors other than milk replacer formulation or protein source likely causes abomasal bloat. Such factors to reduce bloat include preventing overfeeding, and maintaining good hygiene associated with feed preparation (see Chapter05, Animal Health).

3.5 Milk feeding equipment:

 There is a wide variety of milk feeders available. The choice of milk feeding equipment depends on the number of lambs reared, infrastructure available and the feeding system choice (see feeding system section).

Some general recommendations are as follows: 

· To reduce the risk of infection and animal health issues (e.g. bloat), all feeding equipment should be cleaned regularly. If using bottles or cafeterias, all equipment for mixing and feeding milk should be cleaned after each feed with detergent and rinsed thoroughly before drying. 

 · If using automatic feeders, these should be cleaned and calibrated at least weekly. Cleaning needs to include the mixing bowl as well as the milk lines that lead to the teats as milk residues can build up in the lines providing the perfect environment for pathogens. It is recommended to have two sets of milk lines so that the used set can be removed and replaced with the clean set. Between changes, the clean lines can either be dried and stored or remain soaking in a bucket (with a lid) containing sterilisation solution to keep them clean before use. Keep milk lines as short as possible. 

· The area around the teats mounted on feeding panels need to be kept clean and the teats themselves require regular cleaning. Monitor teats for damage daily and replace when required. 

· When using automatic feeders or cafeterias, often the area around the milk feeders becomes soiled with milk. It can be useful to have rubber matting or mesh under the feeding area to enable drainage and ease of regular cleaning to avoid pathogen build-up.

· Automatic feeders require teats to be mounted inside the pens to provide lambs with free access to milk. AgResearch trials have found that teats mounted within a feeding stall where other lambs cannot bully them away from the teat is desirable compared to mounting teats directly to the side of the pens. Competition between lambs when feeding from automatic feeders, especially when young, can reduce intakes and growth rates which in turn can affect health. If teats are mounted directly to the side of pens, it is recommended that they are mounted set back from the wall of the pen to reduce teat damage from lambs chewing the teats, and to ensure that there are no sharp edges as this can cause facial injuries to the lambs.