Heterosis for birth weight in N'dama F₁ crossbred calves in South western Nigeria

 

Antigha Essien

 

Department Of Animal Science, College of Agriculture and Forestry
Cross River University of Technology, PMB 1123,Calabar,Nigeria
antigha2000@yahoo.com

Abstract

Birth weight records from 106 pure bred and 1060 crossbred N'Dama calves (503 males and 663 females) from the Fashola stock farm Oyo, in south-western Nigeria, were analysed. Crosses were made with two indigenous breeds, Muturu and Keteku, and five exotic breeds namely, Brahman, Angus, Charolais, Jersey and Santa Gertrudis. Individual Heterosis (IH) for Birth weight of N'Dama Crossbreds was calculated, first, on the basis of their Parental means, and secondly, on the basis of the birth weight of the Pure bred N'Dama.

 

On the basis of the Parental means, the highest IH with a local breed was recorded between 50% Muturu and 50% N'Dama (14.2%), while the highest IH with an exotic breed, was between 50% Jersey and 50% N'Dama (6.98%), followed by 50% Brahman and 50% N'Dama (1.54%). The rest of  IH values were all negative. On the basis of the mean of the Pure bred N'Dama, all the IH values were positive. The highest IH between N'Dama and a local Breed was between 50% Keteku and 50% N'Dama (19.3%), while the highest IH between an exotic breed and Pure bred N'Dama was 44.4%, between 50% Brahman and 50% N'Dama

 

It can therefore be recommended that because of the high IH for F₁ birth weight between 50% Brahman and 50% N'Dama, this foreign breed can be used to upgrade the N'Dama, producing trypanotolerant F₁ offsprings, superior in birth weight to the parental mean and the mean birth weight of pure bred N'Dama.

 

Keywords: Birth weight, individual heterosis, N'Dama

 

Introduction

 

Birth weight is very important in beef production. Jefrey and Berg (1972) stated that birth weight is important because cows heavier at birth, tended to excel in both pre-weaning and post-weaning growth rates. A 1 kg increase in birth weight can result in an increase of 2.86 to 4.42 kg at 365days of age (Jefrey and Berg 1972).  The rate of an animal's maturity for weight not only affects how soon an animal can be bred (which has a positive correlation with age at first calving), but also affects certain dam-offspring relationships like dystocia (Brody 1945). Body weight and growth are two factors that govern the onset of puberty and until heifers reach a particular weight, oestrus will not occur (Boyd 1977). The weight at which oestrus is attained is positively correlated with birth weight  (Jefrey et al 1971).

 

Most of the land in the humid zone of  Nigeria have been observed as being able to support forage all the year round, hence offering a great opportunity for animal production. But this great potential is largely constrained by the infestation of the tsetse fly, the most common trypanosome in the study area being Trypanosoma vivax (Essien 1998). But the N'Dama, an indigenous tropical breed found in West and Central Africa with an estimated population of 4,862,000, and an estimated 26,000 in Nigeria, possesses an exceptional combination of productivity and hardiness and is inherently trypanotolerant (FAO 1980).

 

Crosses between local and exotic breeds result in heterosis. Cunningham and Syrstad (1987) defined heterosis as the deviation (positive, negative, or zero) of an individual from the mean of its parents. Heterosis (hybrid vigour) is the result of non-additive gene effects (Gregory 1969). McDowell (1972) defined heterosis as the superiority of the hybrids over the average of the parental types or over either of the parental types. Crossbreds were 3.1% heavier at birth than the average of straightbreds in a study reported by Leagate and Gregory (1990).

 

The research on which this paper is based aimed to investigate the amount of heterosis for weight in the F₁crosses between purebred N'Dama with some indigenous and exotic breeds of cattle with the objective of obtaining heavier trypanotolerant calves.

 

 

Materials and methods

 

Data for this research were obtained from birth weight records collected at the Fashola Stock Farm, Oyo from1962 to 1983. The farm was established in 1947 as a multiplication and improvement centre for N'Dama cattle to be distributed to local farmers and for research purposes. The farm is on Latitude 7⁰ 54¹N and Longitude 3⁰43¹E,  immediately north of the tropical rain forest zone of Nigeria. Its total land area is 1,200 hectares and it falls within the Derived Savannah belt of Nigeria, in the tsetse fly belt where Trypanosoma vivax is the most prevalent trypanosome. The area has a bimodal rainfall pattern, peaking in June and September, with a slight break in August.

 

Birth weight records from 106 purebred N'Dama calves and 1060 N'Dama crossbreds (503 males and 663 females)  from 1962 to 1983 were analysed. In collaboration with the United States Agency for International Development (USAID), the crossing of N'Dama with exotic breeds like the Brahman and the Santa Gertrudis, began in 1964. Semen from Angus, Hereford, Jersey and Charolais was also imported under this upgrading programme in 1964. Bulls were allowed to run freely with the cows for a substantial period to ensure successful mating and the imported semen of some of the exotic breeds was used to inseminate mature N'Dama cows that showed signs of heat.

 

F₁ offsprings from crosses between purebred N'Dama and purebred indigenous breeds like Keteku and Muturu, and F₁ offsprings of crosses between purebred N'Dama and purebred exotic breeds like Jersey, Brahman, Angus, Charolais, and Santa Gertrudis were analysed. Data for F₁ birth weights with both sexes pooled together, were analysed using the Microsoft Excel 2000 programme .

 

Individual heterosis (IH) values based on the Parental Average were obtained thus:

 

% IH_P = [(MBWT_F1 -PA) / PA]  x 100

 

where:      % IH_P = Individual Heterosis based on Parental average

                MBWT_F1= Mean birth weight of F₁ crossbreds

                PA = Parental Average

 

Individual heterosis (IH)  based on the mean birth weight of purebred N'Dama were obtained thus:

 

% IH_N = [(MBWT_F1 - MBWT_N) / MBWT_N] x 100

 

where:       % IH_N = Individual heterosis based on mean birth weight of purebred N'Dama

                MBWT_F1 = Mean birth weight of F₁ crossbreds

                MBWT_N = Mean birth Weight of purebred N'Dama

 

Results and discussion

 

The highest IH between purebred N'Dama and a local breed (on the basis of the parental mean with regards to weight) was between purebred N'Dama and purebred Muturu (14.2%). Awobajo (1998) reported an IH of 17.7% for a similar cross between purebred N'Dama and purebred Muturu. The highest IH between purebred N'Dama and an exotic breed was recorded between purebred N'Dama and purebred Jersey (6.98%). Awobajo (1998), obtained an IH of 10.6% for a similar cross between purebred N'Dama and purebred Jersey. Table 1 shows the IH between different crosses of Purebred N'Dama and other Purebred breeds.

The next highest and positive IH between purebred N'Dama and an exotic breed, was recorded between purebred  N'Dama and purebred Brahman. All the other crosses had negative IH on the basis of Parental means.

 

Since the primary objective was to upgrade purebred N'Dama, a second set of values for percentage Individual Heterosis was calculated on the basis of the mean birth weight of purebred N'Dama (Table 2).

On the basis of the mean birth weight of purebred N'Dama, all the values for IH were positive. The highest IH between purebred N'Dama and an exotic breed was between Ndama and purebred Brahman, higher than obtained for a similar cross between purebred N'Dama and purebred Brahman by Awobajo (1998).

 

The highest IH between purebred N'Dama and a local cattle breed was recorded between N'Dama and purebred Keteku, higher than the value of 13.5% reported by Awobajo (1998) and the 9.9% reported by Olutogun (1976) for similar crosses.

 

 

Conclusions and recommendations

 

The cross between purebred N'Dama and purebred Brahman gave a positive (though low) IH on the basis of parental means and the highest IH on the basis of the birth weight of purebred N'Dama. It is therefore strongly recommended to use the Brahman breed to upgrade N'Dama, as this would ensure the birth of heavier trypanotolerant calves. A calf with a good birth weight is likely to have an excellent growth rate all through its productive life.

 

There is however, the need to investigate the effects of other factors that affect birth weight like birth year, season of birth, dam and sire effects, calf sex, type of birth (whether single or multiple), dam's nutritional plan before and during pregnancy, and interactions between these factors, to make appropriate adjustments for these factors.

 

Evidences abound in the literature pointing to the fact that the heritability of birth weight is very low (Osunsanya 1998; Tizikara 1988; Brown et al 1967), so birth weight is largely under the control of environmental factors. Good management practices should therefore be ensured to fully harness the heterosis of the hybrids.

 

A heavy birth weight can predispose the dam (in this case, the N'Dama) to dystocia, which can cause fatal injuries to the calf and the dam. This should be borne in mind whenever crosses to upgrade local breeds with exotic ones are made. The breeder should weigh the benefits accruable from IH for birth weight from crosses between the N'Dama and exotic breeds, with the possible cost of assisting the dam to calve through a caesarian operation. Nevile et al (1978) observed that pelvic dimensions and hip height, are two body dimensions most closely related to dystocia and these two body dimensions are closely affected by environmental factors like management and breed.

 

 

References

 

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Cunningham E P and Systad O 1987 Crossbreeding Bos indicus and Bos taurus for milk production in the tropics. FAO Animal production and Health Paper 68

 

Essien A 1998 Body dimensions of  N'Dama cattle at 12 and 18 months. MSc project. Department of Animal Science, University of Ibadan

 

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Jefrey H B, Berg R T and Hardin R T 1971 Factors affecting preweaning performance in beef cattle. Canadian Journal of Animal Science 51:561-577

 

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Nevile Jr W E, Mullinic Jr J B and McCormick W C 1978 Growth patterns for pelvic dimensions and other body measurements of Beef cattle females. Journal of Animal Science 47:1080

 

Olutogun O 1976 Reproductive performance and growth of N'Dama and Keteku cattle under ranching conditions in the Guinea savannah of Nigeria. PhD thesis, University of  Ibadan

 

Osunsanya O 1998 Linear body measurements of N'Dama cattle at Birth and Six months at Fashola Stock farm. M.Sc Project, Department of Animal Science, University of  Ibadan

 

Tizikara C 1988 Evaluation of Genetic parameters of some growth and reproductive traits in N'Dama cattle and their crosses. PhD thesis, Obafemi Awolowo University, Ile-Ife, Nigeria