Field of the invention

The invention relates to pastoral farming systems, particularly to extensive pastoral farming where livestock animals are born, generally unassisted, in the pasture, and to animal husbandry practices for improving mortality rate of newborn livestock populations in pastoral farming systems.

Background of the invention

Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art.

Pastoral farming systems for farming of livestock may be generally classified into intensive or extensive systems. Intensive farming systems generally involve high inputs of labour and capital throughout the animal growth cycle. In these systems, each animal may be independently intensively managed, in particular with regard to the commencement and completion of gestation.

For example, in intensive pig production, the commencement of gestation is known, which means that for any given animal the gestation age of the pregnancy is also known. This enables the farmer to know the exact time in which to induce labour, and the time at which to condition the animal in preparation for labour.

Such conditioning may include perianal analgesia for pain relief during parturition. Other treatments may be given to increase the chances of survival of the offspring, in particular during the days immediately following birth. For example, WO2007/021 189A2 (Provimi Holding B.V.) discusses the administration of caffeine to an animal as the animal is actually giving birth, or immediately before the mammal gives birth. In this example the actual gestational age is known, as is the time of parturition which tends to arise from artificial induction.

Superchi P et al. 2013 discusses that caffeine orally administered to sows with induced parturition showed a protective effect on the consequences of neonatal hypoxia in tissue ischemia-reperfusion injury piglets. This study administered caffeine to the pregnant sow at a known gestation date. Further, given that parturition was induced, the caffeine was also given in knowledge of the time of birth. The survival of piglets was not improved.

While some studies have demonstrated that caffeine given to neonate piglets improves metabolic variables of the neonate (Orozco-Gregorio H. et al. 2010; Orozco- Gregorio H. et al. 2012); more recent studies have demonstrated that caffeine increases neonatal body temperature and negatively effects survival at 24 hours of age (Nowland TL et al. 2016).

Maternal caffeine administration has been found to significantly decrease cerebral oxygenation in fetal sheep and it has been speculated that this could present a problem for newborn lambs otherwise compromised (Tomimatsu T et al. 2007).

Extensive pastoral systems generally involve much less farmer assistance in animal production. A particular point of difference is the focus on the performance and management of a herd or population of animals as a whole rather than management of individual animals per se. For example, in extensive farming systems, the actual gestation date of any one particular pregnancy of a flock or herd is not known. This is because, unlike an intensive farming system, the date of fertilisation of a given animal is not known.

The difference arises because in extensive farming systems, a population of females is joined with one or more males for a period that is estimated to be sufficient for all of the females of the population to be fertilised. The date that any one particular female is fertilised is not determined. All that is determined is an estimated commencement date of gestation as calculated from the period of joining.

Even if animals have been artificially inseminated, the time to natural parturition varies from animal to animal. For example, in sheep the time to natural parturition may vary by + 5 days of accepted gestation period which on average is about 147 days (although there are breed differences in gestation length).

One particularly important outcome is that the pregnant population is managed according to an estimated gestational age of the population, not according to the actual gestational age of any one particular pregnant female of the population. The population is generally managed according to an estimated parturition period, which is a period starting on the day on which a first birth is expected and finishing on the last date on which birth could be expected.

The above management practices enable the lower labour and capital input costs that are generally associated with extensive farming systems, including cattle, lamb and goat farming systems. However, one difficulty that arises in these systems is that the animals are born unassisted into a pasture and for at least the first few days post birth, are left to fend for themselves in that environment. This puts the newborns into a compromised position as revealed by an unacceptable high mortality rate on average of 20% of a newborn population as observed in sheep farming.

There is a need to reduce or otherwise to improve the survival rate in a population of offspring or progeny, particularly offspring or progeny produced in an extensive farming system, in particular offspring or progeny born in a pastoral environment. There is a need to reduce or otherwise improve the mortality rate in a population of newborn lambs born in pasture, particularly to reduce the mortality rate within 7 days post birth.

Summary of the invention

The invention seeks to address one or more of the above mentioned problems or needs and in one embodiment provides a method for conditioning a near term livestock population to minimise the mortality rate of an offspring population derived therefrom including providing caffeine to a pregnant livestock population before, during and/or after an estimated day of commencement of the parturition period for the population, thereby conditioning the population to minimise the mortality rate in an offspring population.

The gestational ages of each pregnancy of the population may be the same or different at the time of provision of caffeine. In one preferred embodiment, the gestational ages of at least one or some of the pregnancies of the population are different.

Where the caffeine is provided to the pregnant population before the estimated day of commencement of the parturition period for the population, the population is typically a near term population at the time of provision of caffeine.

Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example.

Detailed description of the embodiments

As described herein, the inventors have shown that caffeine may be provided to a herd, flock or population of near term livestock to significantly decrease the mortality rate of a population of animals produced from the near term livestock. These findings are significant because they arise in circumstances where the gestational date of an individual pregnancy and/or the time to parturition for that pregnancy at the time of provision of caffeine is not known.

Previously, the circumstances where caffeine had been proposed for use was in those animal husbandry practices resembling intensive farming where each administration of caffeine was timed according to a known actual gestational age (arising from knowledge of fertilisation date) and/or according to a known actual parturition date (arising from knowledge of date of induction of parturition). The invention is a surprising finding to the extent that it demonstrates that caffeine and methylxanthine compounds can be used irrespective of knowledge of actual gestational age or actual parturition date. It therefore enables the use of caffeine and methylxanthine compounds in livestock animals, particularly those for whom offspring are born in pasture (i.e. without significant assistance) and where neither actual gestational age nor actual parturition date is known. Thus in a first embodiment the invention provides a method for conditioning a near term livestock population to minimise the mortality rate of an offspring population derived therefrom including providing caffeine to a pregnant livestock population before, during and/or after an estimated day of commencement of the parturition period for the population, thereby conditioning the population to minimise the mortality rate in an offspring population derived therefrom.

In a second embodiment the invention provides a method for conditioning a near term livestock population to minimise the mortality rate of an offspring population derived therefrom. The method includes the following steps: - providing a near term livestock population;

- estimating the day of commencement of the parturition period for the population;

- providing caffeine to the population before, during and/or after the estimated day of commencement of the parturition period. In this embodiment, the gestational ages of each pregnancy may be known or the same because the pregnancies may have arisen from artificial insemination. However, because parturition is natural (as compared with induced), the day of commencement of parturition for each pregnancy is not known. In this embodiment, the steps of providing a near term livestock population and estimating the day of commencement of the parturition period for the population may be carried out at the same time, and by the same person or group people. In a third embodiment the invention provides a method for conditioning a near term livestock population to minimise the mortality rate of an offspring population derived therefrom. The method includes the following steps:

- providing a near term livestock population in which at least one pregnancy has a different gestational age from other pregnancies in the population; - estimating the day of commencement of the parturition period for the population;

- providing caffeine to the population before, during and/or after the estimated day of commencement of the parturition period. In this embodiment, the gestational ages of each pregnancy is not known and are unlikely to be the same because the pregnancies arise from joining of males and females and the conception date is generally a function of the joining period. Further, because parturition is natural (as compared with induced), the day of commencement of parturition for each pregnancy is not known. In this embodiment, the steps of providing a near term livestock population and estimating the day of commencement of the parturition period for the population may be carried out at the same time, and by the same person or group people

According to the invention, the provision of the caffeine to the near term population, before, during and/or after the estimated day of commencement of the parturition period, treats or conditions the near term population so as to minimise the mortality rate in the offspring population delivered from the near term population.

"conditioning" with respect to a livestock population generally refers to bringing the animals of the population to a desired state in which the mortality rate of the population of offspring delivered from them is minimised or improved. This may generally be achieved by treating or preparing the animals according to the methods of the invention described herein.

"near term" with respect to a livestock population generally refers to a population of animals that are close to natural parturition. A near term ewe would be considered to have pregnancy with a gestational age of about 135 to 150 days, depending on breed. A near term cow would be considered to have pregnancy with a gestational age of about 260 to 300 days, depending on breed. A near term doe or nanny goat would be considered to have pregnancy with a gestational age of about 135 to 150 days, depending on breed. Generally, in a near term livestock population, the actual parturition date of any one particular pregnancy of the population is not known.

"mortality rate" (also known as "death rate") generally refers to a measure of the number of deaths in a particular population, scaled to the size of that population, per unit of time. For example, the methods of the invention described herein may reduce the mortality rate of a population of newborn lambs over a period of 3 days from birth from 20% to 3%.

"offspring population" or "progeny population" is a population of animals that are delivered from the near term population. "natural parturition" refers to birth without the administration to the pregnant animal of a substance to induce parturition, such as for example oxytocin. Natural parturition may occur in pasture and may be substantially unassisted by the farmer.

"parturition period' is a time period in which all animals of a given population have undergone natural parturition. Put in other words, it is the time from commencement of natural parturition in a population to the time to completion of natural parturition in the population. A "lambing period' is an example of a natural parturition period applying to sheep production. In other farming systems, a natural parturition period may be defined as a "calving period' and "kidding period' for cattle and goat production respectively.

"estimated parturition period' generally refers to a natural parturition period as an estimate because the period is calculated from an assumed time at which fertilisation of all animals of a population have occurred, the latter having regard to the duration of time when males are given opportunity to mate with females. In the case of artificially inseminated females, the time of natural parturition is still estimated due to expected variation between individuals in the time of parturition.

"estimated day of commencement of parturition period' refers to the first day on which natural parturition of an animal of the population is expected.

"estimated day of completion of parturition period' refers to the last day on which natural parturition of an animal of the population could be expected.

"comprise" and variations of the term, such as "comprising", "comprises" and "comprised', are not intended to exclude further additives, components, integers or steps.

In the first, second, third, fourth or fifth embodiment of the invention described herein, a methylxanthine compound may be used instead of caffeine. The term "methylxanthine compound" as used herein generally refers to a compound having methylxanthine structure, i.e. having or being derived from the purine base xanthine, and being other than caffeine. Examples of methylxanthine compounds include theophylline, aminophylline, enprofylline, dyfylline, pentoxifylline, paraxanthine and theobromine.

In the first, second, third, fourth or fifth embodiment of the invention, a methyl xanthine compound may or may not be administered together with caffeine.

Preferably caffeine may be administered in the absence of a methylxanthine compound.

In the first, second, third, fourth or fifth embodiment of the invention described herein, it is preferred that the actual gestational age of each pregnancy of the population is not known.

In the first, second, third, fourth or fifth embodiment of the invention described herein, it is preferred that the actual gestational ages of at least some of the pregnancies of the population are different. Preferably, the longest gestational age is about 1 to 56 days, preferably about 20 to 50 days longer than the shortest gestational age.

As described herein, the caffeine or methylxanthine compound may be provided to the near term population before the estimated day of commencement of the parturition period. In one embodiment the caffeine or methylxanthine compound is provided no more than 14 days, preferably no more than 7 days, preferably no more than 1 or 2 days, before the estimated day of commencement of the parturition period. In one embodiment the caffeine or methylxanthine compound is provided at least 14 days before the estimated day of commencement of the parturition period for the population. In this embodiment, caffeine is provided before any of the animals in the population undergo natural parturition.

In another embodiment, the caffeine or methylxanthine compound may be provided to the near term population on the estimated day of commencement of the parturition period. In this embodiment, at the time that caffeine or methylxanthine compound is provided, a minor proportion of animals (less than 5%) may have undergone natural parturition.

In another embodiment, the caffeine or methylxanthine compound may be provided to the near term population on the 1 ^st day following the estimated day of commencement of the parturition period. In this embodiment up to 20% of animals of the population may have undergone natural parturition.

Preferably the caffeine or methylxanthine compound is provided to the near term population on the estimated day of commencement of parturition and also after the estimated day of commencement of parturition. More preferably the caffeine or methylxanthine compound is provided to the near term population 1 or 2 days before the estimated day of commencement of parturition, also on the estimated day of commencement of parturition and also after the estimated day of commencement of parturition. In one embodiment the caffeine or methylxanthine compound is provided during the estimated parturition period. Preferably the caffeine or methylxanthine compound is provided during the parturition period for a period until at least 80% of the population has undergone natural parturition.

Preferably the caffeine or methylxanthine compound is provided to the near term population daily, but could be given every 2 ^nd , 3 ^rd , 4 ^th , 5 ^th , 6 ^th or 7 ^th day, or once weekly, the latter particularly if the caffeine or methylxanthine compound is provided in a sustained release formulation adapted for the relevant timing of administration. As explained further below, caffeine or methylxanthine compound may also be given once only to each pregnant animal of the population, particularly where the estimated parturition period for the population is relatively short.

Preferably the caffeine or methylxanthine compound is provided to an animal of the population to provide an amount of about 1 to 50 mg, preferably about 20 to 25 mg caffeine (or methylxanthine compound)/ kg animal of the population.

Preferably the caffeine or methylxanthine compound is provided to the population in the form of a product selected from feed, feed additive, lick block, rumen bolus, drench or sustained release device or formulation. In one embodiment the product is adapted to provide caffeine or methylxanthine compound in a dose of less than 50mg/day.

Preferably the livestock is sheep, cattle or goat, more preferably sheep. Thus in a fourth embodiment the invention provides a method for conditioning a near term ewe population to minimise the mortality rate of an offspring lamb population. The method includes the following steps:

- providing a near term ewe population in which at least one pregnancy has a different gestational age from other pregnancies in the population;

- estimating the day of commencement of the parturition period for the population;

- providing caffeine or methylxanthine compound to the population before, during and/or after the estimated day of commencement of the parturition period; thereby conditioning the near term ewe population to minimise the mortality rate in an offspring population.

In a fifth embodiment there is provided a method for conditioning a near term ewe population to minimise the mortality rate of an offspring lamb population. The method includes the following steps:

- providing a near term ewe population in which: - each pregnancy arises from artificial insemination; and/or

- each pregnancy of the population has substantially the same gestational age, or the same gestational age, as other pregnancies in the population;

- estimating the day of commencement of the parturition period for the population;

- providing caffeine or methylxanthine compound to the population before, during and/or after the estimated day of commencement of the parturition period; thereby conditioning the near term ewe population to minimise the mortality rate in an offspring population.

Preferably the mortality rate of the offspring population is reduced by up to 50% of the mortality rate that would otherwise be observed in absence of caffeine administration according to the invention. The invention may in certain embodiments provide for a reduction in the mortality rate of the offspring population within 7 days from birth from 10 to 90%, preferably about 50%, or 60%, or 70% or 80%. For example, of the proportion of the offspring population that (without application of the invention herein) die within 7 days from birth, that proportion can be reduced by up to 90%.

In further embodiments there are provided caffeine -containing products or methylxanthine compound -containing products for consumption by, or for administration to a pregnant population of animals. These products may be formulated according to whether the population is estimated to have a short parturition period or a long parturition period.

A short parturition period generally applies where the animals have been artificially inseminated on the same day. In this embodiment the variance in the date of natural parturition from animal to animal may be less than 7 days, for example 1 to 3 days. In this embodiment, the product may be formulated as a sustained release formulation for once only administration (such as a bolus) to each animal, to provide a given daily dose of caffeine or methylxanthine compound to each animal for each day of the estimated parturition period. Examples of such products include sustained release capsules, pastes etc. The amount of caffeine or methylxanthine compound to be provided in such a formulation and the substrate for controlling release profile of the caffeine or methylxanthine compound can be determined by the skilled worker, having regard to the weight of the animal and the period over which release is required. For example, a slow release intra-ruminal device containing 30 grams of caffeine or methylxanthine compound, releasing 20mg/kg/day, would cover a 70kg pregnant ewe for 3 weeks. A longer parturition period generally applies where the animals have been naturally mated over a joining period which may be up to 8 weeks. In this embodiment the variance in the date of natural parturition from animal to animal may be up to 8 weeks. In this embodiment, the product may be formulated as a formulation for consumption by the animal, preferably on a daily basis, to provide the animal with a given daily dose of caffeine or methylxanthine compound to each animal for each day of the estimated parturition period. Examples of such products include a lick block, or a feed. Where caffeine or methylxanthine compound is provided in the form of a feed, it may be formulated as a premix formulation which is to be added to feed. Thus in one embodiment there is provided a lick block or feed including caffeine or methylxanthine compound in an amount enabling a reduced mortality rate of an offspring population derived from a near term population when said block or feed is consumed by said near term population, said block or feed further including an agent for masking or reducing a caffeine or methylxanthine compound flavour or texture.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text. All of these different combinations constitute various alternative aspects of the invention.

Examples

1 . Aim

The aim of this study was to evaluate whether feeding caffeine to ewes during the lambing period would increase lamb survival in a flock managed under normal commercial conditions.

2. Materials and methods 2.1 Location and design

An experiment was conducted with the approval of the Charles Sturt University Animal Ethics committee during 2016 (project A16009) on a commercial property (34°48'S; 147°26'E) 40 km north of Wagga Wagga, NSW. The experiment included two treatments with three replicates of each. The caffeine treatment was ewes fed caffeine (1 .6 g/ewe per day) at an estimated mean 20 mg/kg liveweight for the first 14 days of the lambing period, and the control was not supplemented with caffeine for the same time.

The design was a randomised block, using three paddocks as replicate blocks which were subdivided to provide paddocks for each treatment. Replicate 1 grazed 17 ha paddocks containing annual grasses, subclover (Trifolium subterraneum) and lucerne (Medicago sativa); replicate 2 grazed 1 1 ha paddocks containing oats, subclover and annual grasses; and replicate 3 grazed 7 ha paddocks containing annual grasses, with a large quantity of dead pasture.

2.2 Management A flock of mature (2.5 to 6.5 years when mated) Merino ewes which had been joined with Merino rams between 14 February and 26 March was used. Ewes (n=493) which had been determined to be pregnant using trans-abdominal ultrasound, or which by abdominal size were considered likely to be pregnant, were stratified on age, then randomly allocated to replicates and treatments on 6 July, prior to the expected start of lambing on 14 July. Unfasted liveweights and body condition score (scale 0 (emaciated) to 5 (obese)) (Jefferies 1961 ) of ewes was recorded before ewes were placed in paddocks. Numbered plates were tied around their necks for identification during lambing.

Lambing commenced the day after caffeine supplementation began, and is defined as day 1 of the lambing period. During the lambing period, the ewes were checked once daily each morning. Newborn lambs were identified to their mothers, ear- tagged, and their sex recorded. Assistance to deliver lambs was provided to ewes if necessary, and recorded. The day dead lambs were found was recorded, and these lambs removed from paddocks, weighed, and a post-mortem examination conducted (McFarlane 1965) to determine the cause of death, with lambs which had not breathed fully being classified as 'born dead'.

When lambing was complete the sheep were brought to yards (1 -3 September, 2016), the ewes were weighed (unfasted) and condition scored, and the weight of lambs recorded. The survival of lambs to marking age was determined by presence at this time, since all lambs which died earlier may not have been found.

2.3 Feeding

An oral supplementation method for caffeine which was potentially suitable for commercial application was used. Caffeine was fed to the supplemented treatment for 14 days from 15 July (the day before lambing commenced) to 28 July, as this was expected to achieve supplementation to approximately 80% of ewes on the day before lambing if the ewes were all naturally cycling at the start of joining. Caffeine (96.8% + 5% SD purity assayed by HPLC) was fed at a rate of 1 .6 g/ewe per day, based on a rate of 25 mg/kg liveweight (mean 63 kg) on 6 July, with an estimated rate of 20 mg/kg at term.

To facilitate caffeine intake, the ewes were introduced to barley grain from 7 July. During the period of caffeine supplementation, the caffeine was mixed into a molasses and water (3:1 ) solution, and this was mixed with barley grain (320 g/ewe per day) in a cement mixer. The same quantity of barley grain and molasses solution was mixed and fed to control ewes. The supplement was placed in 12.5 m troughs in each paddock to minimise wastage, and feed refusals were collected daily. Ewes without newborn lambs were encouraged to the feed troughs, if they did not come directly, to minimise the risk of individuals achieving excess intake of either caffeine (toxicity) or barley (acidosis).

Replicate 3 ewes were also given a magnesium supplement for the duration of the lambing period due to the lack of legumes in the pasture. Lick blocks (grass tetany blocks, Olssons) were supplied.

2.4 Pasture and weather measurements

The quantity of live pasture available was estimated on 7 July 2016 prior to the lambing period. The visual estimation method of Haydock and Shaw (1975) was used, with 60 visual estimates taken in a diagonal transect across each paddock. The estimates were calibrated against 20 quadrats cut at ground level with electric clippers.

Weather data (temperature, wind speed) was accessed from the Wagga Wagga airport meteorological station (number 072150) (www.bom.gov.au/climate), approximately 40 km south. Rainfall data was recorded manually on the experimental site.

2.5 Statistical analyses

Data for ewes which gave birth to triplets was excluded as the numbers were small and differed between treatments (1 1 caffeine, 6 control). Data for two lambs which were born with fatal congenital deformities, one lamb which was born as a twin to a mummified fetus, and 3 lambs dying due to fox predation were excluded. Lambs for which birth type (single or twin) or date of birth was not determined were also excluded from all analyses. Data for 474 ewes and 701 lambs were available for analysis.

Prior to analysis, data were assessed for assumptions of normal distribution and homogeneity using Genstat® 16th edition (VSN International 2013). Data comparing proportions were analysed using generalised linear mixed modelling using a binomial distribution. The proportion lamb mortality was analysed with treatment x lambs born x week of birth as the model fitted and replicate + day of lambing (where day 1 = the day the first lamb was born) as the random effect. The effect of replicate on lamb mortality was assessed using the same fixed effects, and day of lambing as the random effect. The logit transformation meant standard errors for backtransformed means were not available. Available live pasture, ewe weight and condition score were analysed using linear mixed modelling, with treatment x time, where relevant, as the fixed and replicate as the random effects. Changes in ewe weight and condition score were also analysed using linear mixed modelling, with treatment as the fixed and replicate as the random effects. Lamb weight at marking was analysed using linear mixed modelling using birth- rear class (single, twin, twin reared as single) + treatment x period of supplement (born during the first two weeks of lambing or later) as the fixed effect, and replicate as the random effect. A P-value of 0.05 was considered significant. The results are presented as mean + SEM where appropriate.

3. Results

3.1 Weather during lambing

Cold, windy weather occurred during the first week of lambing. However, conditions declined for the entire second week of lambing, with cooler temperatures, strong winds and rain falling on all days (Table 1 ), and a sheep graziers alert (indicating high chill conditions and risk to sheep) being issued by the bureau of meteorology. Subsequent weeks remained cool but wind speeds and the occurrence of rainfall declined. Table 1. Mean daily weather conditions during weekly lambing periods.

Week 1 Week 2 Week 3 Weeks 4 to 6

Dates 16 Jul to 22 23 Jul to 30 Jul to 4 5 Aug to 30

Jul 29 Jul Aug Aug

Minimum temperature (°C) 6.5 4.5 4.7 3.8

Maximum temperature (°C) 16.9 1 1 .0 13.1 15.1

No. days rain (No. days > 5) (mm) 1 (1 ) 7 (4) 1 (1 ) 1 (1 )

Wind speed at 9 am (km/hr) 12 14 9 1 1

Maximum wind gust (km/hr) 25 40 28 27

No. days maximum wind gust >20 km/hr 4 7 3 18

3.2 Availability of pasture

The quantity of live pasture available pre-lambing was similar (P=0.334) in the caffeine (767 ± 189 kg DM/ha) and control (742 ± 189 kg DM/ha) plots.

3.3 Ewe weight and condition

The mean unfasted live weight of ewes was similar between treatments and the interaction with time was not significant (P=0.053). The ewes were heavier (P<0.001 ) before lambing (62.7 ± 1 .30 kg) compared with after the lambing period (60.7 ± 1 .30). The mean weight loss over the lambing period was less (P=0.006) in the caffeine (-1 .2 ± 1 .86 kg) than in control ewes (-2.8 ± 1 .86 kg).

The mean condition score of ewes was also similar between treatments, but was higher (P<0.001 ) pre-lambing (3.1 ± 0.07) than post-lambing (3.0 ± 0.07). The loss in condition score over the lambing period was similar (P=0.628) between treatments (caffeine -0.1 ± 0.12; control -0.1 ± 0.12).

3.4 Supplement intake

All supplement was consumed in replicates 1 and 3 during the period of caffeine supplementation. In replicate 2, control ewes consumed all of the supplement, but caffeine ewes only consumed approximately half of their feed - 155 ± 18 g barley and 0.8 ± 0.09 g caffeine per day. The majority of ewes appeared to consume supplement daily in replicates 1 and 3, while in replicate 3 a larger portion of ewes may not have consumed the supplement due to the large quantity of live pasture in that replicate reducing the interest of ewes in grain.

3.5 Lamb production The ewes commenced lambing on 16 July, with the last lambs born on 25 August

(day 41 of lambing). The percentage of ewes which lambed during week 1 , 2, 3 and 4 plus (4 to 6) was 16, 34, 28 and 22%, respectively. The percentage of ewes giving birth to twins was 56% and 54% in the caffeine and control treatments, respectively.

The proportion of lambs dying to day 1 , day 3 or marking age was higher (P<0.006) for twins compared with single-born lambs, but the interaction with either treatment or week of birth was not significant. The mean proportion mortality to marking was 0.13 and 0.18 (n= 98, 104) for singles, and 0.26 and 0.33 (n=251 , 248) for twins in caffeine and control treatments, respectively. The mean proportion mortality to marking for lambs born in week one of lambing was 0.06 and 0.28 (n= 16, 1 1 ) for singles, and 0.13 and 0.38 (n=36, 54) for twins in caffeine and control treatments, respectively.

Birth type was therefore included as a covariate with treatment x week of birth as the model. The proportion mortality to day 1 for singles (0.08) was lower (P<0.001 ) than for twins (0.16), and mortality to marking age of singles (0.16) was also lower (P<0.001 ) than that of twins (0.30). The proportion mortality of lambs to day 1 , day 3 or marking age was 15, 17 and 21 % lower (P<0.05), respectively, in the caffeine compared with the control treatment for lambs born in week 1 of lambing, but not in later weeks, as shown in Table 2.

The response to caffeine supplementation was similar (P=0.976) between replicates, despite replicate 2 ewes consuming only half the caffeine dose. The proportion mortality to marking age for lambs born in week 1 of lambing was 0.06 or 0.23, 0.06 or 0.46, and 0.14 or 0.32 for caffeine and control treatments in replicates 1 to 3, respectively.

The proportion of lambs born alive (breathed fully) during the period of supplementation (weeks 1 and 2 of lambing) was similar between the caffeine (0.97) and control (0.97) treatments, and was similar to that of lambs born in later weeks (0.99 caffeine, 0.98 control), with no interaction between treatment and period (P=0.425).

Table 2. Proportion mortality of lambs to 1 or 3 days after birth (tagging), and to marking age for lambs born in weeks 1 to 4 plus from the start of lambing. Number of lambs in brackets.

^* Weeks in which caffeine supplement was fed.

a,b: Indicates means differ significantly within rows at P=0.05.

Assistance to deliver lambs was required by two caffeine and three control ewes during the first 2 weeks of lambing, the period of caffeine supplementation. After this period, a further 2 caffeine ewes and 3 control ewes required assistance for delivery.

A total of eight ewes died during the lambing period, comprised of three control ewes and five caffeine ewes. Prior dystocia was considered to have contributed to the deaths of three of the caffeine treatment ewes, but none of these deaths occurred during the period of caffeine supplementation. Prolapsed intestines caused one death in the caffeine treatment, while the cause of the other death was unclear. 3.6 Weight of lambs

The live weight of lambs at marking age varied (P<0.001 ) between birth and rearing classes, and was heaviest in lambs born and reared as singles (14.9 ± 0.63 kg), less in lambs born as twins but reared as singles (13.3 ± 0.66 kg), and least in lambs born and reared as twins (10.7 ± 0.62 kg). The live weight of lambs at marking age was higher (P=0.042) in the caffeine treatment (13.2 ± 0.62 kg) compared with control lambs (12.7 ± 0.62 kg). There was a trend (P=0.089) for lambs born during the period of supplementation (the first two weeks of lambing) to be 0.8 kg heavier in the caffeine than in the control treatment, but this difference did not occur for lambs born in later weeks.

4. Discussion

This is the first study to show that feeding caffeine to ewes reduced the morality of their lambs. Lamb mortality to marking was reduced from 30% to 9% by feeding caffeine to ewes for lambs born during the first week of lambing. Survival was not improved during the second week of supplementation, however, this is considered due to the overwhelming influence of windy, wet, weather throughout that week. Rainfall combined with strong winds of the level experienced can lead to the deaths of 91 % of lambs born (Obst and Day 1968) due to lambs being unable to maintain adequate heat production for long periods (Alexander 1962). Such weather usually kills lambs soon after birth, but lambs up to 2 days of age are also susceptible (Alexander et al. 1980).

Lamb mortality was not reduced in week 3 of lambing after caffeine supplementation had ceased. This result was as expected, based on pharmacokinetics. Caffeine has a terminal elimination half-life of 8.9 hours in sheep (Danielson and Golsteyn 1996). After a drug is discontinued, concentrations in the body decline exponentially and by 4 half-lives (total 36 hours for caffeine in sheep) concentrations are less than 10% of that achieved during dosing. The lack of any effect of caffeine on mortality rates in week 3 is consistent with caffeine washout resulting in little or no drug remaining (beyond sub-therapeutic residue levels) in the dam and fetus to cause an effect. In addition, the expected low intake of caffeine in milk by lambs after birth imply that caffeine supplementation impacted lamb survival from ewe intake prior to, not after, parturition. Poor weather being the primary cause of lamb mortality and thereby masking any large effect of caffeine on mortality rates in week 3, is unlikely since the rate of mortality for control lambs in week 3 was lower than that in week 1 or 2, associated with an improvement in weather conditions. Therefore, the lack of benefit of caffeine in week 3 suggests that caffeine supplementation was only effective when ewes were fed caffeine on the day of or before parturition.

Importantly, the similarity of mortality in both treatments in week 3 and later also indicates that there was no adverse effect on lamb survival of a 14 day supplementation period during late pregnancy. A single dose may give a different response than repeated dosing. The similarity of marking weights of surviving lambs, and the lack of impact on ewe weight and condition also indicate the safety of at least a 14 day period of supplementation. Further studies are needed over longer periods, if it is assumed that feeding throughout the whole lambing period may occur in order to supplement all ewes on the day of lambing.

The cost-effectiveness of a longer period of supplementation will depend on the value of additional lambs, level of increase in survival, cost of feed carrier, and cost of caffeine. Caffeine is inexpensive in commercial bulk quantities, and the feeding technique would be highly profitable at current high sheep values if the same level of increase in survival as obtained in week one were obtained over 2 or 3 weeks of supplementation. Molasses was required in order to enhance palatability, as caffeine is bitter to the taste. Elimination or reduction of this bitterness, by chemical modification or some other means, would enhance palatability and reduce overall feed costs.

The mechanism by which lamb mortality was reduced was not examined in this study. However, since the number of lambs born alive did not differ, it is clear that at least most of the benefit was through increasing survival in the first day after birth. This timing is consistent with an improvement in either response to hypoxia, or some other short-term metabolic or behavioural adaptation to the post-uterine environment.

While the method of feeding caffeine used in this study is commercially feasible, more user-friendly methods are desirable which are less labour-intensive and remove the risk of pure caffeine dust being inhaled. Feeding methods which avoid the potential mismothering of lambs at feeding time would also make the practice more likely to be adopted by producers.

5. Conclusion The mortality of lambs to marking age was reduced from 30% to 9% by oral supplementation with caffeine to ewes during the lambing period, and the benefit was evident in both twin and single-born lambs. Supplementation was not effective in high chill weather conditions which caused large increases in mortality, and there was no benefit once supplementation ceased. The technique of caffeine supplementation used in this study is suitable for commercial sheep enterprises and has the potential to substantially improve lamb survival when used in appropriate conditions. While caffeine supplementation is low cost, producers need to consider the value of extra lambs, and feed costs to evaluate whether caffeine supplementation may be cost-effective.

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