risk factors associated with dairy goats stayability

www.elsevier.com/locate/livprodsci

Livestock Production Science 89 (2004) 139–146

Risk factors associated with dairy goats stayability

M. Perez-Razoa,*, F. Sanchezb, G. Torres-Hernandezc, C. Becerril-Perezc,J. Gallegos-Sanchezc, F. Gonzalez-Cosıoc, C. Meza-Herrerad

aDepartamento de Zootecnia, Facultad de Estudios Superiores Cuautitlan, Universidad Nacional Autonoma de Mexico, Carretera Cuuautitlan,

Cuautitlan Izcalli, Mexico, 54700 MexicobDepartamento de Produccion Agrıcola y Animal, Universidad Autonoma Metropolitana Xochimilco, Calzada del Hueso 1100,

Villa Quietud 04960, Coyoacan D.F., Mexico, Mexicoc Instituto de Recursos Geneticos y Productividad, Colegio de Postgraduados, Montecillo Texcoco, Mexico, Mexico

dUnidad Regional de Zonas Aridas, Universidad Autonoma Chapingo, Bermejillo, Durango 35230, Mexico

Received 6 January 2003; received in revised form 16 February 2004; accepted 24 February 2004

Abstract

Data on 1044 Alpine, 773 Granadina, 1118 Nubian, 560 Saanen and 312 Toggenburg does, recorded from 1982 to 2001 at the

National Goat Center, Tlahualilo, Durango, Mexico, were used to examine breed differences and relationships between traits

observed at birth (date and weight) and at first kidding (age, litter weight and month of kidding) with stayability up to their 4th, 5th

and 6th kidding seasons from birth using logistic regression analysis. In general, Alpine breed showed the highest stayability

values and Saanen the lowest, while the other breeds showed intermediate values. Stayability estimates increased with the increase

in birth weight. Stayability also increased with the increase in litter weight at first kidding, but they decreased curvilinearly as

kidding season progressed. Goats whose first kidding was delayed showed an advantage in stayability, as compared to those

kidding early in life. Goat breeds in this study were different in their age at first kidding. Granadinas and Nubians showed a longer

kidding season than the other breeds. Compared to the other breeds, the Nubians showed the lower probability of kidding during

their first kidding season in life; therefore, cumulated litter weight favored the Alpine and Granadina breeds.

D 2004 Elsevier B.V. All rights reserved.

Keywords: Dairy goat; Age at first kidding; Kidding season; Longevity

1. Introduction

Herds of crossbred or upgraded goats from

imported germplasm during the second half of the

last century are becoming common in tropical devel-

oping countries. Such is the case in Mexico, where the

Anglo-Nubian, French-Alpine, Saanen and Toggen-

burg breeds have been introduced, mainly from the

0301-6226/$ - see front matter D 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.livprodsci.2004.02.008

* Corresponding author.

E-mail address: [email protected] (M. Perez-Razo).

United States, to upgrade local goats of Spanish origin

known as ‘‘Criollas’’. Among ‘‘Criollas’’, some herds

of Granadina-like goats are observed and the selection

towards the standard of this Spanish breed from local

goats has been practiced. Under stall-feeding condi-

tions, results on higher milk yield or body weight

argue in favor of the imported breeds (Montaldo et al.,

1995; Sanchez et al., 1994). However, the kidding

distribution pattern suggests that the length of the

breeding season is shorter in the Alpine, Saanen and

Toggenburg breeds than in Granadinas (Sanchez et al.,

Table 2

Means (F S.E.) of parity according to breed and stayabilities 4–6

Breed Stayability

4 5 6

Alpine 2.65F 0.03b 3.23F 0.04a 3.70F 0.05a

Granadina 2.78F 0.04a 3.35F 0.05a 3.80F 0.06a

Nubian 2.33F 0.03c 2.83F 0.04c 3.15F 0.05c

Saanen 2.58F 0.04b 3.00F 0.05b 3.29F 0.07bc

Toggenburg 2.55F 0.05b 3.08F 0.07b 3.49F 0.08b

a, b, c: Different letters within a column indicate significant

differences ( P< 0.05).

M. Perez-Razo et al. / Livestock Production Science 89 (2004) 139–146140

1984). Further, a report signaled a higher survival

from birth to 7 months of age in Granadina kids as

compared to the other breeds, a factor that has been

attributed to better acclimatization.

A long reproductive life may be one of the most

important components of goat profitability. Lengthen-

ing reproductive life may result in decreased replace-

ment costs and lead to a heavier proportion of goats

that is in later, high-producing kiddings. On this basis,

when age at first kidding occurs at 1 year instead of 2

years of age or older and successful pregnancies are

obtained in each breeding season, more kids and milk

can be expected from a goat during her lifetime, as

stated in beef cattle (Bergmann and Hohenboken,

1992; Buskirk et al., 1995), although some evidence

indicates that there is some antagonism between early

maturity and longevity (Essl, 1998).

There is a problem with the statistical analysis of

productive life because some animals are still alive at

the end of the study period and constitute censored

records (Vukasinovic et al., 1997). Furthermore, var-

iation in length of the breeding season in goats may

affect parity, as well as the cumulated number and

weight of kids born and weaned in a given period.

Under these conditions, other than censored data, a

non-normal (maybe multimodal) distribution can be

expected when longevity is considered by production

or age type variables. Therefore, stayability at given

periods seems to be more adequate, if periods or age

type variables consider the breeding season. Addi-

tionally, stayability measured at different periods can

provide evidence of how traits measured early in life

(such as birth weight and date of birth) or first kidding

traits (such as age, kidding date and litter weight)

influence longevity in does. Then comes the question

whether early reproduction implies a shorter or longer

productive life.

Table 1

Percentiles of kidding dates distribution by breed

Breed Date of kidding

5th percentile 50th percentile 95th percentile

Alpine December 30 February 16 May 7

Granadina November 17 January 31 May 4

Nubian December 3 February 2 April 19

Saanen December 9 February 18 May 21

Toggenburg January 11 February 25 May 23

The objective of this study was to examine breed

differences and relationships between traits observed

at birth (date and weight) and at first kidding (age,

litter weight and month of kidding) with stayability at

4th, 5th and 6th kidding seasons in five goat breeds.

2. Material and methods

Data for the study were provided by the National

Goat Center of Tlahualilo, Durango, Mexico. Data on

13,835 birth records of kids born alive from 3807

does in the period October 1982 to March 2001 were

used. History and management of herd have been

documented elsewhere (Sanchez et al., 1994; Mon-

taldo et al., 1995; Perez-Razo et al., 1998).

A data set was prepared with records from does

that met the following criteria: (1) a minimum age of

250 days at first kidding and a maximum of three

kidding seasons from birth; (2) a kidding interval from

a minimum of 200 days and a maximum of three

kidding seasons (two kidding seasons without kidding

records were tolerated); and (3) only records with data

on breed, tatoo, birth weight, birth date, birth type

(single, double, and higher), weaning weight, sire ID,

dam ID, kidding date, litter size and litter weight at

kidding and weaning were considered for the analysis.

There were 1044 Alpine, 773 Granadina, 1118

Nubian, 560 Saanen and 312 Toggenburg does in-

cluded in this study. For each breed, only does with no

less than three-fourths of the corresponding genotype

were included.

The year was considered from October (previous

year) to September (current year) according to the

kidding distribution pattern. Therefore, age at first

kidding was defined as the difference (in year units)

Table 3

Litter size and weight at birth and cumulated litter weight by breed at stayabilities 4–6 (meanF S.D.)

Breed Litter size Litter weight Cumulated litter weight

Stayability 4 Stayability 5 Stayability 6

Alpine 1.45F 0.52 4.65F 1.65 11.50F 0.16a 14.54F 0.22a 17.46F 0.30a

Granadina 1.56F 0.54 3.94F 1.33 10.54F 0.20b 13.17F 0.27b 15.63F 0.37bc

Nubian 1.66F 0.63 4.83F 1.73 10.65F 0.15b 13.32F 0.20b 15.28F 0.28bc

Saanen 1.44F 0.52 4.74F 1.70 10.80F 0.21b 12.99F 0.28b 14.94F 0.39c

Toggenburg 1.50F 0.55 4.62F 1.71 10.95F 0.27ab 13.69F 0.37b 16.21F 0.50b

a, b, c: Different letters within a column indicate significant differences ( P < 0.05).

Table 4

Odds ratios (OR) and 95% confidence intervals (CI) for age at first

kidding and stayabilities 4–6 by breed

Breed Kidding at first Stayability

season in life4 5 6

Granadina 1.23 1.17 1.36* 1.72***

(0.91–1.65) (0.91–1.50) (1.05–1.76) (1.28–2.30)

Nubian 0.25*** 1.34** 1.28* 1.21

(0.19–0.34) (1.07–1.68) (1.02–1.61) (0.93–1.57)

Alpine 1.05 1.38** 1.69*** 1.91***

(0.81–1.34) (1.10–1.73) (1.34–2.12) (1.47–2.47)

Toggenburg 1.25 1.10 1.36* 1.64**

(0.91–1.73) (0.81–1.49) (1.00–1.85) (1.17–2.30)

Saanena 1.0 1.0 1.0 1.0

95% CI for OR within parenthesis.

*P < 0.05.

**P < 0.01.

***P < 0.001.a Utilized as the reference breed.

M. Perez-Razo et al. / Livestock Production Science 89 (2004) 139–146 141

between their first kidding season and the season of

birth. Consequently, stayability, defined as the prob-

ability of survival up to 4th, 5th and 6th kidding

seasons, was expressed in year units. Kidding date

and birth date were calculated as the number of days

lapsed from October 1, within kidding or birth season.

For computation purposes, age at first kidding was

coded as zero (if a goat kidded during her first kidding

season in life) or 1 (if kidding occurred during their

second or third kidding season). Three categories of

stayability were defined, therefore, as the probability

of survival up to 4th, 5th and 6th kidding seasons.

Goats with kidding records during or after these

periods, indicating survival, were coded as zero or 1

otherwise. Breed and cohort were transformed into

dummy variables and were present in all statistical

models, irrespective of their level of significance. Five

levels were determined for breed: Alpine, Granadina,

Nubian, Toggenburg and Saanen. Fourteen levels

were determined for cohort according to year of birth,

1983–1996.

For indicative purposes, percentiles of kidding

dates distribution were extracted from the frequencies

of the overall data set. Further, the GLM procedures

of SAS (SAS, 1998), considering breed and year

effects (without interactions) were used to estimate

means (F S.E.) of parity and means (F S.D.) of litter

size and weight at birth and cumulated litter weight at

stayabilities 4–6 according to breed.

Statistical analysis was performed utilizing logis-

tic regression procedures (SAS, 1998). Age at first

kidding was analyzed as a function of birth weight

and date of birth as covariates (linear and quadrat-

ic). Stayability was firstly analyzed including birth

weight and birth date of dam as covariates (linear

and quadratic). A second model included traits

recorded at the first kidding as follows: age at first

kidding in terms of breeding seasons (1, 2, 3) as

dummy variables and litter weight at birth and

kidding date as covariates (linear and quadratic).

A forward stepwise variable selection method was

employed to develop the final logistic regression

model; the P value for variables entering or leaving

the model was 0.05.

3. Results

Some statistics must be considered as preliminary

remarks. It can be observed that seasonality in Gran-

adinas followed by Nubians is less marked than in the

other breeds (Table 1). Furthermore, differences be-

tween breeds were found in relation to means of parity

attained at stayabilities 4–6. In general, Granadinas

followed by Alpines attained the highest parities and

Table 5

Odds ratios (OR) and 95% confidence intervals (CI) from

probability of having the first kidding according to stayabilities

4–6

First kidding Stayability 4 Stayability 5 Stayability 6

3rd kidding season 2.92*** 2.18*** 1.88***

(2.30–3.71) (1.68–2.38) (1.68–2.38)

2nd kidding season 2.00*** 1.76*** 1.68***

(1.68–2.38) (1.46–2.12) (1.36–2.08)

1st kidding seasona 1.0 1.0 1.0

95% CI for OR within parenthesis.

***P < 0.001.a Utilized as the reference season.


Nubians the lowest in all stayabilities (P < 0.001;

Table 2). Despite the differences between breeds in

litter size and litter weight at birth and in cumulated

litter weight at birth, Alpines were in general superior

to the other breeds (Table 3).

Differences between breeds were observed on the

probability of kidding at the first season in life and

on stayability at 4th, 5th and 6th kidding seasons

from birth (Table 4). Odds ratios indicated that

Nubians had a lower probability of kidding at their

first kidding season from birth than the other breeds

(P < 0.001). Saanens showed the lowest values in

stayability and therefore they were used as the

reference breed. Stayability in Alpines was 1.4–1.9

times higher than in Saanens. The other breeds

showed intermediate odds ratios and were different

from Saanens (P < 0.05) at stayabilities 5 and 6.

The probability of kidding at the first kidding

season showed a linear increase with birth weight

(P < 0.01) and a linear decrease with month of birth

(P < 0.001; Fig. 1). Early-born does (November) with

high or low birth weight have a 3.2–3.8 times higher

probability of kidding at their first kidding season as

compared to late-born does (April).

The quadratic effect of birth weight on stayabilities

4–6 was not significant (P>0.05); therefore, this

variable was excluded from further analysis. The linear

effect of birth weight was significant (P < 0.05) only on

stayability 5. Stayability estimates from birth weight

Fig. 1. Probability of kidding at first kidding season according to

birth weight and date of birth.

(b = 0.1502F 0.0692) indicate a roughly relative in-

crease of 0.05 for each 0.5 kg increase in birth weight.

Goats whose first kidding was in the second or

third breeding season showed odds ratios indicating

1.7–2.9 times higher stayability than goats that kid-

ded at their first kidding season (Table 5).

A linear litter weight effect at the first kidding on

stayabilities 5 and 6 (P < 0.05) was observed. An

average increase of 0.01 in stayabilities 5 and 6,

associated with each kilogram of increase in litter

weight at first kidding, is shown in Fig. 2.

A curvilinear effect of kidding month on stayabil-

ities 4–6 was found (P < 0.01). Stayability in does

whose first kidding was by November 1 was 1.4–1.6

Fig. 2. Effect of litter weight at first kidding on stayabilities 4–6.

Fig. 3. Effect of month of kidding on stayabilities 4–6.


times higher than in does whose first kidding was by

April 1 (Fig. 3).

4. Discussion

The Saanen and Alpine breeds showed the lowest

and the highest values in stayability, respectively;

therefore, Saanens were used as the reference breed

for odds ratios. The other breeds showed intermediate

values. Stayability estimates indicated a direct in-

crease with the increase in birth weight. Furthermore,

it was observed that there is an increase in stayability

in line with the increase in litter weight at first

kidding and a curvilinear stayability decrease as

kidding season advances was observed. Finally, goats

whose first kidding was delayed showed an advan-

tage in stayability as compared to those kidding early

in life.

From available data, barren does and aborting

ones were not distinguishable. We also could not

conclude if milking was extended in barren goats,

although this is a common practice in this herd as in

many herds in Mexico. Thus, it is assumed that

abortion, infertility and extended milking affected

the five breeds equally.

Differences in stayability or longevity between

breeds or genetic groups have been reported in dairy

cattle (Hocking et al., 1988; Vollema, 1998), beef

cattle (Arthur et al., 1993; Riley et al., 2001) and

pigs (Lopez Serrano et al., 2000; Xue et al., 1997).

The increase in stayability with the increase in birth

weight found in this study agrees with a report on

replacement rate in goats (Arun et al., 2001) and

differs with a work in beef cattle where no effect of

birth weight on longevity was found (Tanida et al.,

1988). The direct relationship of litter weight with

stayability, as found in this study, has been reported

in pigs (Tholen et al., 1996); sows with smaller

litters at first parity had a higher risk of being culled

(Guo et al., 2001; Yazdi et al., 2000). Litter size and

weight are criteria of selection in sows; however, in

Mexico, there is a high demand of meat from goat

kids and this could account for these results. The

curvilinear decrease observed in stayability according

to month of kidding indicates that early-kidded goats

had a higher probability of survival than late-kidded

goats. This effect has been reported in dairy cows

(Boettcher et al., 1997; Gahlot et al., 2001; Mukher-

jee et al., 1999; Raheja, 1997).

In general, an older age at first kidding is associ-

ated with a shorter reproductive herd life, lower

parity at removal and lower life time production in

cattle and pigs, which may be explained by selection

and voluntary culling (Bergmann and Hohenboken,

1992; Buskirk et al., 1995; Cozler et al., 1998;

Koketsu et al., 1999). However, in this study, does

whose first kidding was delayed showed higher

stayabilities, although lower parities at culling, which

suggests from moderate to a lack of selection on this

issue.

Results in this study showed breed differences in

the kidding distribution pattern, as it has been previ-

ously reported in this flock (Sanchez et al., 1984) and

elsewhere (Amoah et al., 1996). The longer kidding

season observed in Granadinas and Nubians may be

related to early age at first kidding, which was true for

the former breed, but not for the latter. Reproductive

success in the first kidding season may depend on

both size and body condition. The observed effect of

the date of birth within the previous season may

influence a goat’s size and body condition at their

first breeding season in life. Thus, goats born early in

the kidding season will show an advantage over late-

born goats, as this has been observed in the kid’s

survival (Perez-Razo et al., 1998).


The optimal strategy involves not breeding when

body condition is below a certain critical level (Essl,

1998; McNamara and Houston, 1996). When a goat’s

body condition at her first breeding season is below a

critical level, there will be delayed reproduction until

this condition improves sufficiently. This may be

explained by differences in body weight (Majid et

al., 1993), as Nubians are clearly heavier than Gran-

adinas (Sanchez et al., 1994; Montaldo et al., 1995).

In contrast to Granadinas, Alpines showed a similar

ability to reproduce at their first breeding season in

life despite a shorter kidding season. These results

can be explained by evolutionary theories suggesting

that the acquisition of longevity involves significant

metabolic costs and there may be a trade-off between

reproductive success and longevity because resources

invested in longevity assurance may be at the ex-

pense of reproduction (Westendorp and Kirkwood,

1998).

A delayed reproduction seems favorable to stay-

ability, but it is incompatible with intensive produc-

tion systems. A constraint to the approach taken in

the present study is the lack of data on milk traits.

However, the literature indicates that goats kidding

early within a season yield more milk because the

lactation length is increased (Gall, 1981). Goats that

have a delayed first kidding may be less profitable

because of the increase in rearing costs, even if they

produce more kids and milk in their first lactation

than first parity goats starting their productive life

during their first breeding season. The lifetime

potential to produce kids and milk can be reduced

when goats had a late start because they had less

kiddings and lactations. However, stayability and

longevity traits are mainly affected by environmen-

tal effects as low estimates of heritabilities are

generally reported for both traits (Buenger et al.,

2001; Jairath et al., 1994; Yazdi et al., 2000).

Although heritabilities for age at first kidding tend

to be from medium to high (Aboul Naga and

Hanrahan, 1992), late kiddings usually may be a

consequence of suboptimal management (feeding

and reproduction) or accidents (abortions) and these

factors likely increase the risk of being culled (Durr

et al., 1999).

Under intensive production systems where defi-

ciencies in goat rearing have been overcome, such

environmental factors may be lowered and a program

to obtain the first kidding at 1 year of age is well

documented (Majid et al., 1993) and can be envis-

aged. When this is not feasible, a question that arises

may be the possible effect of epigenetic factors that

leads to the concepts of genomic imprinting, meta-

bolic imprinting, and thrifty phenotype documented in

human and laboratory animals (Falls et al., 1999), a

fact that certainly needs further research in animal

science.

5. Conclusions

Differences between breeds regarding stayability

were found; the Saanen and Alpine breeds showed

the lowest and the highest values, respectively.

Increasing birth weight had a direct impact on

stayability. Furthermore, it was observed that there

is an effect on stayability in line with the increase in

litter weight at first kidding and a curvilinear stay-

ability decrease as the kidding season advanced. In

addition, late age at first kidding was related with

higher values in stayability. Finally, goats whose

first kidding was delayed had an advantage in

stayability compared to goats that kidded early in

life. With excellent management and controlled

feeding throughout breeding lifetime, puberty can

be stimulated to start at young ages and first

parturition can be expected during their first kidding

season without reducing life expectancy of does, but

increasing productive longevity. These does will

reproduce similarly to females conceiving for the

first time at their second or third sexual season, even

though they have fewer body reserves accumulated

by the time they are first bred. Therefore, goats

development programs designed to increase birth

weight and litter weight may achieve higher stay-

ability values. Future research on the development

of such an evaluation and the relationship of such a

trait with other economically important traits, such

as milk yield and composition, needs to continue.

During economic comparisons of genotypes aimed

at offering recommendations for implementation

under smallholder dairy production systems in the

tropics, the profitability of any genotype given

certain constraints reflects the ability to make max-

imum utility of scarce resources for survival and

production.


Acknowledgements

The authors wish to thank Mr. Jose Pilar Regalado

and Centro de Crıa Caprino Tlahualilo. Dgo. for

allowing to access to data files.

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