Survival, growth and reproductive performance in F1 crossbred cattle produced and managed on station in the Gambia

A Diack, F B Sanyang and N Corr

International Trypanotolerance Centre, PMB 14, Banjul,
The Gambia, West Africa
a.diack@itc.gm  ;  adiack89@yahoo.com

Abstract

In a trial whereby a large number of cows were needed to calve at approximately the same time, opportunity was taken to establish a crossbred cow population at the International Trypanotolerance Centre (ITC).

A slight improvement in the traditional husbandry system revealed a great productivity potential of these crossbreds. Their survival rate to one year (i.e., 90.0 % for the Jersey x N'Dama (J x N) and 71.2 % for the Friesian x N'Dama (F x N)) was proved satisfactory in the local environment, though conclusions are that more attention is needed for rearing Friesian type F1 calves in the tropical environment. With an overall mean birth weight of 17.7 ± 4.1 kg and an overall mean daily weight gain (DWG) of 0.220 ± 0.104 kg they attained an average weight of 100.6 ± 29.9 kg at one year. Their relatively retarded growth recommended a better management. Puberty was attained at 478.2 ± 13.9 days, age at first calving 970.5 ± 94.1 days and the overall mean calving interval and open period were 400 ± 82.5 and 117 ± 83.2 days, respectively.

These reproduction data showed that the crossbreds mature earlier and have shorter calving intervals than the N'Dama breed.

Key words: Crossbreds, Friesian, Jersey, N'Dama, growth, reproduction

Introduction

In 1994, at the International Trypanotolerance Centre (ITC) a disease-nutrition trial (Bennison 1997) was planned in which a large number of cows which had to calve at the same time were needed. This could only be achieved by synchronising all open N'Dama cows available at the time. It was then decided that this opportunity be taken to use semen from exotic dairy breeds in order to produce F1 animals for the purpose of peri-urban milk production. The programme envisioned was a continuous F1 production scheme as proposed by Madalena (1993). The resulting males would just be a by-product and therefore destined to slaughter or used for draught purpose after castration. At that time the methods of synchronising N'Dama cows were still not perfect and as a consequence quite a few twin births resulted, something which naturally occurs extremely rarely in N'Dama cows. In order to get a reasonable number of F1 cows the synchronisation and insemination was then repeated in 1995 and to a lesser degree in 1996. The first phase of that scheme focussed on producing, rearing and managing F1 crosses on station to evaluate their productivity and adaptability to the peri-urban small-scale farms. The data generated are analysed here so as to constitute a reference for small-scale farmers involved in producing and exploiting F1 crossbreds.

Materials and methods

F1 production and rearing

The production of the F1 population was done by artificial insemination following oestrus synchronisation of the N'Dama cows. Deep-frozen semen of the Jersey type was obtained from New Zealand and that of Holstein-Friesian through FAO from an AI station in Italy. In both cases semen from test bulls was requested, since the aim was to determine the value of the breed and not of any individual sire. The synchronisation was done so that the calves were born at the end of the rains when feeding for both calf and dam was optimal. Out of the synchronised N'Dama cows 142 crossbred calves were obtained of which 77 of the Friesian type (43 males and 34 females) and 65 of the Jersey type (30 males and 35 females).

The new-born calf was allowed to suck colostrum and milk ad libitum during the first week. The calves, until weaning at ten months, were raised in the traditional way. They were used to stimulate the milk let down effect and were allowed to feed on residual milk left after milking during mornings and evenings. The calves were then reared as a group in a single pen and offered groundnut hay and water ad libitum. At weaning, males were castrated to be sold when they attained a 100-kg target live weight. The heifers were removed from their male counterparts by twelve months of age and reared as a separate group. Dry season feed comprised groundnut hay offered ad libitum and a supplement consisting of a mixture of groundnut cake, rice bran and cottonseed. During the rainy seasons the animals grazed the natural pastures within the station premises. The same feeding system was applied for the rest of the station herd. When the heifers reached the age of 20 months, a N'Dama service bull was introduced and stayed with the herd throughout. Prophylactic treatment for control of gastrointestinal parasites was given twice during the rainy seasons (from June to October) to calves and heifers and acaricide treatment for tick control applied to all categories throughout the year. Vaccination was done against anthrax, black quarter and haemorrhagic septicaemia, and all clinical cases were attended.

Data collection and analysis

All animals were identified using ear tag numbers at birth and their birth weights were recorded in the herd book. All animals were weighed monthly. All matings and calvings were recorded based on the observations of the herdsmen. Thus, mating and calving dates were used to compute gestation lengths and open periods from calving intervals. Calving interval was determined as the number of days between two consecutive calvings for the same cow. Records of matings were reviewed to calculate the gestation length and open period in each calving interval. In case the service date was unknown, only the calving interval was considered. Therefore, the data set used to determine open periods and gestation lengths represent only a subset of data used to calculate calving intervals. Therefore, unequal numbers of records were used for computing the measurements of the various traits.

For the analysis of gestation length, birth weight and mortality rates the following model was used:

y = year_i + sex_j + type of birth_k + breed_l + ε_ijklm

For weight development, the same linear model was applied but included in addition herd, month and age.

Calving interval was analysed with the following model:

Y_ijkl = breed_i + birthtype_j + year_k + ε_ijkl

Results

Birth types in the F1 cattle herd

A total of 142 crosses was born in three crops from 1995 and 1997 (Table 1). There were more multiple births in 1995 and 1996 than in 1997 (P<0.001)..

Gestation length and birth weights

In cattle, the gestation length is largely determined by the genotype of the foetus. In this study, gestation time was known for 117 pregnancies which had a mean gestation time of 279.6 days with a standard deviation = 5.7 days. There were 133 available birth weights of the crossbreds of which the overall mean was 17.7 kg with a standard deviation of 4.1 kg (Table 2).

As a baseline value the 1995 born (F x N) single males were carried 284.1 ±1.8 days and had a mean birth weight of 22.2 ± 0.8 kg.The different contrasts obtained between levels of major factors and their respective significance are summarised in Table 3 for gestation length and birth weights.

Mortality

Out of the total of crossbreds born 18 animals (13.1%) died at or shortly after birth; therefore, there were 124 animals left. Mortality was significantly higher (P<0.0004) in males than females, and in the group born in 1996 (P<0.02) compared to the others. For the factor breed type only a tendency could be suspected (P<0.08). Up to one year the mortality of (J x N) was 10.0% and that of (F x N) was 28.79%, a difference that was significant by Fisher's exact test (P<0.013). The most frequent cause of death was diarrhoea. All other causes arose only sporadically.

Growth

There were great differences in weights between breeds and sexes. Live weights at specific ages are shown in Table 4 whereas the weight development expressed as daily weight gain at specific periods is illustrated in Graphs 1 and 2.

Both breed crosses maintained approximately similar weights up to three years. However, (J x N) had a greater daily weight gain than (F x N) over the period. The mean daily weight gain reached maximum values of  0.550 ± 0.145 and 0.511 ± 0.150 kg at the ages of 16 and 17 months for (F x N) and (J x N), respectively (Figure 1). The males up to two years performed better than the females but the latter out-performed the males from the third year (see Figure 2).

The average adult weights irrespective of sex, were 324 ± 63 and 286 ± 48 kg for the (F x N) and (J x N), respectively (Figures 3 and 4)

Reproduction

There were 47 crossbred females that calved between one and six times. Altogether there were 184 calvings. The age at first calving was 970.5 days with a standard deviation of 94.1 days (Table 5). The range was from 872 days to 1211 days. None of the factors breed, year and birth type was significant. The mean calving interval found was 400.1 days with a standard deviation of 82.5 days. The factors breed (P<0.005) and year of dam birth (P<0.05) were significant.

A total number of 92 open periods could be computed out of the 184 calvings. The mean open period found was 117.1 ± 83.2 days with only breed being significant (P<0.001). The (J x N) had a shorter open period than the (F x N) crosses (96.3 ± 62.9 versus 160.2 ± 102.7 days), the mean difference  (F x N) - (J x N) being 59.0 ± 20.25 days.

Up to 20 months of age purposely no animal was served, since an age of first calving of about 30 months was targeted. However, the mean age at puberty as shown by the first serum progesterone rise in 19 F1 heifers was 478.2 ± 13.9 days (equivalent to 15.9 ± 0.5 months) and weight at puberty 113.8 ± 22.7 kg. A one-way analysis of variance did not show any difference between Jersey and Friesian F1 type.

Discussion

Gestation length is largely determined by foetal factors, among others (parity, maternal environment, etc.). Estimates of its heritability in taurine cattle are between 0.25 and 0.50 (Andersen and Plum 1965). In comparison, early reports on the N'Dama breed give estimates of 288.2 to 288.5 days (Sada 1968; Ralambofiringa 1978). The data found in this study are consistent with the findings of Rodriguez et al (1983) who observed that gestation averaged 281.5 ±7.25 days in dairy cows, compared with 287.7 ± 9.23 days for beef cattle. The same observations were found that the gestation of male calves were one to five days longer than that of females, though these differences tended not to be significant (Jainudeen and Hafez 1980). The same conclusions were reached as with Bazer and First (1983) that gestation tended to be shorter for twins than for a single birth by three to six days.

The survival to one year, estimated as the proportion left out of each cohort after deduction of mortality cases at one year, amounted to 90.0 % for the (J x N) and 71.2 % for the (F x N). Female calves in all breed types survived better than their male counterparts. These results, in line with a previous report in Tanzania (Said et al 2001) on crossbred mortality tend to show that the crossbred calves in harsh tropical environment suffer severe mortality before the age of one year. Observations of over 50% mortality before one year were reported in tropical x exotic crossbreds (Said et al 2001). However, the corresponding mortality rates in this study are higher than those observed in N'Dama either on station in Senegal (Fall et al 1982), Ghana (Tuah and Yaa Nyamaa Danso 1985) and The Gambia (Njie and Agyemang 1991) or in village production systems (Fall et al 1999). As can be expected this may be inferred to the fact that the N'Dama breed is well adapted to its environment. The fact that Jersey crosses survived better than Friesian crosses support the fact that the Jersey breed has been extensively used for crossbreeding in tropical regions as it has a higher heat tolerance among European breeds (Letenneur 1983). Therefore, more attention is needed for rearing Friesian type F1 calves in the tropical environment.

The overall mean birth weights found in this study are below all those previously reported on crossbreds in Ethiopia (Kiwuwa et al 1983), Côte d'Ivoire (Letenneur 1983), Malawi (Agyemang and Nkhonjera 1986) and Tanzania (Said et al 2001), yet above values reported in N'Dama cattle on station (Fall et al 1982). This may be attributed to management-related performance since for the same genotype (i.e., ½Jersey x ½N'Dama), Letenneur (1983) reported 19.3 ± 1.8 kg when it was only 16.2 ± 3.5 kg in the present study.

The F1 crossbreds grew at 0.220 ± 0.104 kg to attain a mean weight of 100.6 ± 29.9 kg at one year. Agyemang et al (1997) reported a mean weight of 82 ± 17 kg at one year for N'Dama calves in the Gambian traditional husbandry system. In that context, the crossbreds performed better. However, the surprising observations are the retarded growth rate after two years and that there is hardly any weight difference between the two crossbreed types. These might be due to the scarcity of funds dictating a prudent management of feed stocks over an extended period overlapping with that of the growth of these animals.

Puberty was attained in this study at an average age of 478.2 ± 13.9 days, in contrast with values reported on N'Dama heifers on station in Côte d'Ivoire (Meyer et Yesso 1991) and Ghana (Gyawu et al 1989) that were 815 ± 104 and 856 ± 171 days, respectively. The lighter weight at puberty  of crossbreds in this study, (113.8-± 22.7 kg), compared to that of N'Dama heifers (175 ± 20 and 176 ± 24 kg, respectively, in the above-mentioned reports), is particularly indicative of the early maturity of the former. This assertion is supported by the mean age at first calving found in this study (32.4 months for the total herd) compared to that of 53.4 ± 7.4 months for N'Dama cows in Gambian traditional husbandry systems (Agyemang et al 1997). Age at first calving impacts on generation interval and, therefore, influences a cow's productive life. The results presented here are consistent with those in earlier reports from the African continent. Kiwuwa and Redfern (1969) and Compere (1963) found 29.4 and 36.5 months in Uganda and Rwanda, respectively for ½ Jersey whilst Knudsen and Sohael (1970) reported 31.9 months in Nigeria for ½ Friesian.

The overall mean calving interval and open period found in the study were 400.1 ± 82.5 (approximately 13 months) and 117.1 ± 83.2 days, respectively, for the whole herd. Calving interval can be divided into three periods: gestation, postpartum anoestrus (from calving to first oestrus) and the service period (first postpartum oestrus to conception). The postpartum anoestrus and service periods represent the "days open" period or "open period" which is the part of the calving interval that can be shortened by improved herd management. Ideally, the "days open" period should not exceed 80-85 days if a calving interval of 12 months is to be achieved (Peters 1984). The data reported here are consistent with data reported previously on crossbreds in the continent. Earlier reports in the African continent mentioned calving intervals of 488 (Agyemang and Nkhonjera 1986), 427 and 458 days (Kiwuwa et al 1983) for ½Friesian in Malawi and Ethiopia, and 403 days (Kiwuwa et al 1983) for ½Jersey in Ethiopia. In comparison, Menendez Buxadera et al (1983) found a calving interval and an open period of 421.6 and 138.9 days, respectively, for purebred Friesian in the Cuban tropical environment. Agyemang et al (1997) found a mean calving interval of 658 ± 225 days for N'Dama cows in the Gambian traditional husbandry system. Therefore, the data presented here reflect a sound physiological status of the overall herd associated with a prudent management system.

The data reported in the present study on reproduction parameters represent major improvements in performances in comparison to the local breed. The crossbreds grew faster, matured earlier and had shorter calving intervals than the N'Dama breed. These traits suggest an opportunity for performance improvement in small-scale farming systems. However, a forthcoming socio-economic evaluation of these performances will further enable us to come to a final appreciation.

Acknowledgements

The authors would like to thank Lamin Janneh, Jim Njie and all ITC support staff on station for their technical assistance. The creation of and other necessary operations on the herd on station were done with financial support from GTZ/BMZ, EU and the African Development Bank. The African Development Bank, the World Bank through the HIPC programme and EU supported the extension phase of the crossbreeding programme. The data preparation and analysis work was carried out with the financial support of the EU funded regional project Programme Concerté de Recherche-Développement de l'Elevage en Afrique de l'Ouest (Procordel). This work is published with the permission of the Director General of ITC.

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