Production and Reproduction Evaluation

Foreword

Reproductive management is the centerpiece of any production system. Tremendous progress has been made in the last 2 decades in our understanding of reproductive phenomena in camelidae and their interaction with the environment and disease processes. This knowledge should allow the practitioner and the breeder to work together to optimize production. Herd health management is a continuous process by which the veterinarian and the breeder monitor the herd in order to meet production goals. The herd is evaluated through a set of indices which are compared to production and reproduction targets set according to physiological and economic criteria. It is very difficult to cover all possible facets of herd health management in this chapter because of the multitude of systems under which camelidae are raised. However, we hope to give the reader guidelines on how to approach herd health monitoring in these species.

The primary objective in any camelidae production system is to obtain the maximum number of offspring from the reproductive herd. Thus, evaluation of reproduction is critical for the herd economics. Reproductive efficiency can be determined using several indicators which address specific concerns.

Reproductive performance indicators

Many reproductive indices have been defined to evaluate the fertility of the herd. These indices are generally of two types: those which give a general estimation of the reproductive performance (reproductive rate, birth rate, etc.) and those that address specific problems of reproduction such as abortion rate and embryonic rate. It should be kept in mind that reproductive performances are affected by several factors including the age structure within the herd.

Fertility indices

Annual reproductive rate

Annual live birth rate is the number of births in one year (365 days) divided by the number of females joined (mated) at the beginning of the year. Because the pregnancy duration in llamas and alpacas is less than a year, and these animals are rebred soon after parturition, this rate should be 100% if there are no reproductive problems.

Annual Reproductive Rate has been used by some authors as a measure of fertility of camel herds. This rate is calculated according to the formula: number of young bom x 365 divided by the interval between parturitions (days), and represents the number of young born to a group of females in reproduction in one year.⁽⁶⁹⁾

Reduplication rate

The reduplication rate, which is equal to 100% when 50 births are recorded for 100 females in reproduction, has been used in the evaluation of nomadic herds of dromedary camels. This rate takes into consideration that because the birth interval in the dromedary is 24 months, only half of the females in the breeding herd can give birth in the same year.⁽¹⁷⁾

Fecundity rate

Fecundity rate is the number of viable offspring bom divided by the number of females in reproduction. This rate is very close to the annual reproductive rate when calculated for one year.⁽⁵⁴⁾

Conception and pregnancy rate

The conception rate is the number of pregnant females divided by the number of females joined. This rate can be calculated for a specific period, for the whole year, or for a group of females bred to a particular male. The conception rate should be calculated for the herd and for different categories of females: maiden, primiparous and weaned. The accuracy of this rate depends on the accuracy of the method used for pregnancy diagnosis. This rate allows a detailed investigation of early pregnancy loss when compared to confirmed pregnancy rate and parturition rate. Some authors prefer to differentiate between the overall conception rate which is calculated for the whole herd at the end of the breeding season and the first-service conception rate which is the percentage of females becoming pregnant after one service. Fertility of the herd can also be analyzed through the evaluation of the average number of services per conception.

Birth rate

Birth or parturition rate is the proportion of bred animals that deliver an offspring at the end of the breeding cycle. This rate is calculated by the formula: number of females that deliver an offspring divided by the number of females bred during the whole season.

Culling rate for infertility problems

Fertility of the herd can also be measured by the proportion of animals culled for reproductive problems. The fertility of animals is expected to decrease after a certain age. Culling age has not been defined for camelidae and depends on many factors. In milk- or meat-production dromedary herds, the culling age would be around 16 years of age, at which point the fertility of the female seems to drop. In racing dromedaries the animals may be kept for a longer time. In Tunisian herds, the maximum number of offspring in the life of a dromedary is 7 and the end of the female reproductive life is 17.⁽⁴⁵⁾ The most important aspect of culling is to determine the reason and age of animals at culling. High involuntary culling rate in breeding animals (> 5%) is usually an indication of severe management problems. In nomadic dromedary herds, culling rates for sterility range from 5% to 28%.⁽⁵⁴⁾

Reproduction intervals

Intervals between reproductive events are the result of management decisions as well as reproductive efficiency. The two most important aspects in the evaluation of herd reproductive performance are the age at first parturition in primiparous females and the interval between parturitions in pluriparous females.

Ages at first mating and first parturition

In all breeding systems, young females should not be bred until they reach 60% of their adult weight (cf. Physiology). The age at which they reach this size and consequently the age at parturition depends mainly on the management of replacement animals. Age at first parturition can be delayed by poor growth due to nutritional or disease factors. Therefore, the determination of these two ages enables the veterinarian to evaluate the young-animal rearing program.

Interval between two successive parturitions

Increasing reproductive efficiency in a herd depends on decreasing the number of days open and shortening the inter-parturition interval. Parturition interval has two main components: pregnancy length and interval from parturition to a new conception. Pregnancy length is a set physiological parameter which cannot be changed. Thus, interval between parturitions is largely affected by the interval from parturition to breeding and establishment of a new pregnancy. Interval from parturition to breeding depends on the length of lactational anestrus, uterine involution and management decisions. Nutritional status and fertility of the female are the most important factors in the interval from parturition to establishment of a new pregnancy. In the llama and alpaca, females are usually bred soon after parturition (10 to 15 days) allowing a short inter-parturition interval (cf. Physiology). This is not the case for the dromedary where the interval between parturitions presents a high variability, especially in the traditional nomadic system. An interval from parturition to establishment of a new pregnancy of 25 to 50 days is physiologically possible in intensively-managed dromedaries but the decision to breed this early may not be economically justifiable in some breeding systems.^{(44, 70)}

Pregnancy loss indices

The incidence and nature of pregnancy loss can be determined from the following rates:

1)    Embryo or fetal loss rate = number of confirmed pregnancies divided by the number of total positive pregnancy diagnoses. Camelidae are reputed for a high incidence of early embryonic loss. Therefore a mechanism for the evaluation of the incidence of such losses should be put in place. This can only be done if the females are checked for pregnancy status at least twice during the period of high risk of fetal death and unobserved abortion (before 120 days). In poorly managed herds, the incidence of early embryonic loss can reach up to 40%. Incidence of early embryonic death should be analyzed in light of the herd's age structure because the incidence of this type of loss tends to be higher in very young and in aged females.

2)    Abortion rate = number of abortions divided by the number of confirmed pregnancies

3)    Stillbirth rate = number of stillbirths divided by the number of confirmed pregnancies

Total pregnancy loss rate in the herd = embryo or fetal loss + abortion + stillbirths

Neonatal loss

The ultimate productivity measure of the herd is the number of offspring weaned per female in the breeding program. This evaluation is approached by the analysis of the mortality of young animals in different age groups (e.g. pre-weaning and yearling).

Reproductive performance in camelidae, limitations and possibilities

Reproductive performance in the dromedary

Age at first mating and first parturition

Age at puberty is greatly affected by the system of management and probably by the type of camel. In Russia, age at puberty was reported to be as low as 8 to 12 months.⁽³⁾ In most cases, puberty is reached at 2 years in relatively well-fed dromedaries^{(6, 7)} and at 4 to 5 years in most traditionally managed herds.

Reported ages at first parturition vary between 3 and 7 years (Table 1) and depend on several factors including the breed and management system. In one study on the dromedary, this parameter was found to have very low heritability and most of the variation could be explained by management factors.⁽¹¹⁾
 

Age at first parturition was improved in herds that were provided adequate nutrition and veterinary care.^(37,63) Improvement of age at puberty and age at first parturition by nutritional and management intervention are well illustrated by Tunisian studies.^{(34, 35)} Ten out of twelve females conceived at 31.8 months at a body weight of 64% and a body size of 81% to 94% of those of the adult animal, respectively. The ration consisted of wheat straw ad libitum and a concentrate ration of 500 g/ 100 kg /day (one UF and 191 g protein per /kg). In another study, all females receiving a concentrate ration and weighing more than 250 kg showed follicular activity earlier and were successfully bred at 2 years of age.⁽⁴⁵⁾

Reproductive rates

All fertility indices indicate that the reproductive performance in the dromedary camel is poor especially in areas where there is no veterinary care. The annual reproductive rate and the reduplication rate vary according to years and herds from 21% to 47% and from 11.5% to 84.6%, respectively.^{(62, 63, 69)} In Kenyan commercial herds with improved ration or artificial pasture and presence of a health program, the birth rate varies between 55% and 80%, whereas in traditional herds this rate rarely surpasses 40%.^{(48, 56, 58, 59)} In well-managed herds, fertility rate can be as high as 85% with a parturition rate of 96%.^(1,2) Conception rates are 38% after one breeding and 64% after two breedings with an overall conception rate of 66.7% in primiparous females and 60% in pluriparous females.⁽⁸⁾ In Morocco, the average annual reproductive rate and fecundity in different dromedary herds were respectively 62% and 53.3%.^{(18, 60)} In the United Arab Emirates the number of services per conception is 1.63 ± 0.2 with a first-service conception rate of 58%.⁽⁴⁾ In our experience, when the animals are well nourished, the most important factor in the first-service conception rate is management of breeding. Most breeders still reiy on behavioral signs of heat to determine time of breeding. We have shown that these are not very accurate. In herds where the males are left with females, conception rates can be higher than in herds where hand mating is practiced. However, in herds with close veterinary monitoring, first-service conception rate can reach 72% with a birth rate of 82%.

Fertility rates vary greatly according to age groups. In Niger, where fertility rate is defined as (the number of parturitions + abortions) divided by the number of females in reproduction, fertility rate is between 31% and 48% in animals aged older than 3 years and fecundity rate is 42%.⁽⁵⁴⁾ In Sudan, fecundity rate in the dromedary varies between 0% and 5% for females aged 3 to 4 years, 2% to 26% for females aged 4 to 5 years, and 8% to 41% for females aged 5 to 6 years. Fecundity rate increases and plateaus between 6 and 10 years of age and depends on the type of management.⁽⁵³⁾ In Tunisia the parturition rate averages about 39% and varies according to age of the animals. Birth rate of females in age groups 2 to 3, 3 to 4, 4 to 5, and 5 to 6 years was respectively 4%, 21%, 37%, and 61%. The birth rate in females that are 7 to 13 years old ranged from 29 to 56%.⁽²⁰⁾

Fecundity can also be influenced by the heath status of the herd, particularly with regard to trypanosomiasis and brucellosis incidence. ^{(9, 10)}

Abortion rate

In nomadic herds of dromedaries, the pregnancy losses due to early embryonic death and abortions vary from 3% to 33%.^{(54, 70)} These losses are certainly underestimated because many abortions go unnoticed.

Inter-parturition interval

Interval between two parturitions varies from one region to the other which suggests that management, and    particularly feeding and weaning, has a great influence on this parameter (Table 2). This interval is mainly affected by the duration of lactational anestrus and the fertility of the female after the beginning of ovarian activity. In an intensively managed system the first estrus after parturition takes place at 25 days and 40 days for non-lactating    and lactating females respectively.⁽⁷¹⁾
 

According to one study in Niger, the interval between two parturitions tends to decrease with increasing number of parturitions of the dam. This interval was 28.6, 24.0, 25.8, and 20.1 months for parturitions 1-2, 2-3, 3-4, and >4 respectively.⁽⁶⁹⁾ In the UAE, the inter-parturition interval tends to decrease from 27.5 months in animals with 1 to 3 parities to 23.1 months in animals with more than 3 parities.⁽⁴⁾

The interval between parturitions can be reduced by early weaning and artificial feeding of the young. In one study, the average interval from weaning to mating was 9.1 ± 7.8 days with a conception rate of 76.8%. The interval from parturition to mating in weaned females was 17.9 ± 9.1 days. This technique gives an interval between parturitions of 403.5 days instead of 714.6 ± 30.7 days.⁽⁴⁵⁾ The interval between parturitions can be considerably improved if nutrition is adequate and lactation length is not affected by early re-breeding.^{(33, 35, 41)}

Reduction of the interval between parturitions was achieved by early weaning and hormonal treatment (progesterone + eCG 2000 IU).^{(22, 44)} This treatment induces follicular activity in 58% of the females treated and results in a pregnancy rate of 40%.⁽⁴⁴⁾

Well-managed herds in the UAE achieve a conception rate of 85% with a parturition interval of 391 ± 21 days. The first estrus of postpartum occurs at 29.1 (10 to 41) days.^{(1, 2)} Conception rates of 62.5% were obtained when breeding took place 70 days after parturition.⁽⁸⁾

Neonatal mortality

Pre-weaning mortality rate and abortion rates are probably the areas where the greatest improvement can be achieved for the increase of productivity in nomadic dromedary herds.^{(16, 56-59, 67)} In one study, mortality rates in young varied between 7% and 15% in commercial herds or research stations and 25% to 90% in traditionally managed herds.⁽⁵⁸⁾ Pre-weaning losses amounted to 25.7%.⁽⁷⁰⁾ In Tunisia, mortality rates from 0 to 3 months and from 0 to 1 year of age were respectively 23% and 30%.⁽²⁰⁾ Mortality rate in the first year of life in Somalia is 19.6% due mainly to meconium retention,⁽¹²⁾ camel pox infection,⁽⁴⁰⁾ and salmonellosis.⁽¹⁰⁾

Reproductive performance in llamas and alpacas

Reproductive management of South American camelidae varies according to the system of production. Traditionally managed herds in South America are usually seasonal whereas small herds in developed countries tend to breed all year round. There are few thorough studies on reproductive performances of llamas and alpacas in their countries of origin probably because of the lack of adequate records and low veterinary input.

Mating practices vary from continuous presence of the male to joining at specific times after parturition. The sex ratio in these systems is usually 6 to 10 males for 100 females.⁽⁵⁵⁾ The free system of management may result in some females being bred several times per day for several days whereas others may be mated less or not at all.⁽⁵⁵⁾

The productive life of the llama in Ecuador has been estimated at a little more than 8 years. In these conditions the animals are kept by a small holder for transport,, fiber and food.⁽⁴⁹⁾ Lifetime production of the llama in Ecuador averages 2.8 to 3 offspring.⁽⁶⁸⁾

Age at first conception

Many author have demonstrated that the female llama and alpaca are capable of ovarian activity and conception as early as 6 months of age but that they should not be bred until one year of age. In Ecuador, a survey of several herds showed that the age at first conception in llamas is 20 months.⁽⁶⁸⁾ Many modem breeding farms use a target breeding age of 12 to 18 months in alpacas. The female should reach 60% of the adult weight (50 kg) at one year of age. Males should not be used before 2.5 years of age.^{(29, 64)}

Fertility

There are very few reports on the optimal conception rate to be expected in a herd of llamas or alpacas. Conception rates calculated on the basis of the number of pregnant females at the end of a joining period or following a single breeding vary from 45% to 90%.

Interval between parturitions

Well-managed llamas and alpacas should be able to breed and conceive as early as 10 days postpartum. However, maximum fertility is observed when the animals are bred 20 to 30 days after parturition.^{(5, 13, 14, 64)} Therefore a production target of one offspring per year is perfectly possible in these species.

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