Lactation performance on-station of F1 crossbred cattle in The Gambia

A Diack^*, F B Sanyang and S Münstermann

International Trypanotolerance Centre, PMB 14, Banjul, The Gambia, West Africa
*Permanent address: c/o DIREL, 37 avenue Pasteur, B P 67, Dakar Sénégal
adiack89@yahoo.com   ;   adiack@itc.gm

Abstract

The lactation performance of 47 Friesian and Jersey crosses over one to five calvings on station was evaluated. Their overall total lactation and daily milk yields were 1,188 ± 458 kg and 3.78 ± 1.1 kg. Their mean daily milk peak yield, time to peak and persistency were 4.16 ± 2.51 kg, 3.8 ± 4.7 weeks and 84.0 ± 32.3 %, respectively. In addition, restricted suckling or the death of the calf did not cause the lactation to cease, which is a major positive change in the Gambian traditional husbandry system. These figures equated four to five times that of the N'Dama but were probably below their potential due to management limitatons.

Key words: Dairy cattle, F1 crossbreds, Friesian, Jersey, lactation, N'Dama, The Gambia

Introduction

In The Gambia, like many other West and Central African countries, the Government has heavily depended these last decades on imports to bridge the gap between demand and supply of animal products, specially milk, stretching on its meagre financial resources. The N'Dama breed which forms the basis of the agriculture in the country is well adapted to the prevailing harsh environmental conditions for it is tolerant to trypanosomosis and other enzootic diseases and can thrive on poor quality grasses available during the dry season giving it the comparative advantage over European breeds in a low input farming system. However, the breed is genetically a poor milk producer yielding only 400 kg per lactation (Agyemang et al 1997) whereby large numbers are required to produce sufficient quantities of milk to meet the demand of the urban population. Management of such large herds around urban settlements requires much more grazing land which is now becoming less and less available. An alternative to this is the introduction of high yielding European breeds or their crosses - provided their survival and maintenance at a certain level of their superior productive potential - associated with improved animal husbandry practices. In many places in the tropics crossbreeding European dairy cattle with local breeds has been advocated to gain time in increasing productivity per animal unit in order to tackle the challenge of an increasing gap between demand and supply in milk. Hence, in many places programmes based on the continuous production of F1s (Madalena 1993) are being implemented, crossbreeding high-yielding European dairy cattle with local breeds (Vaccaro 1974; McDowell 1985; Syrstad 1989; Syrstad 1990; Rege et al 1994; Tawah et al 1999), including The Gambia.

Located at the furthest point of the African continent westwards, The Gambia lies between latitude 13° and 14° North and longitude 13° 47 and 16°50 West, juxtaposed to Banjul island the capital city and stretching eastwards as a narrow strip from the Atlantic ocean on both sides of the river Gambia. The climatic conditions vary less throughout the land mass than throughout the year, due to the small physical size of the country covering 11,000 km² (IFAD 1995a). The northern part is under the influence of the Sahelian climate with open savannah while the southern part falls into the Guinea zone with higher humidity (IFAD 1995b; Ridder 1991). The Atlantic ocean influences both of these climates in the areas near the coast. The rainfall is unimodal starting in June until mid October and ranging from 660 to 1,108 mm per annum.

In The Gambia, the crossbreeding programme was based on artificial insemination (AI) of N'Dama cows using deep-frozen semen of European dairy breeds (Jersey, Holstein-Friesian). Since 1994, three generations of F1 have been produced and managed on station at the site of the headquarters of the International Trypanotolerance Centre (ITC) situated at Kerr Serign village. Kerr Serigne is located on the West coast of The Gambia along the Atlantic Ocean coastline. It lies between the latitude 13° 45' N and longitude 16° 45' W. The climate is sub-humid and of the drier tropical type with average minimum and maximum daily temperatures of 20°C and 33°C respectively. Two distinct seasons exist: the short but intense rainy season occurring between June and October and the long dry season which covers parts of October and extends until June. The rainfall ranges between 650 and 1,200 mm per annum. As Kerr Serigne is a settlement within the Greater Banjul Area the vegetation is one of new settlement within an open savannah area but with a reserve forest park between the settlement and the Atlantic ocean. The Greater Banjul Area lies on the south-west along the Atlantic coastline and covers an area of about 1,000 km². It consists of a conglomerate of big towns and villages extending from the small island of Banjul to Brikama town some 40 km eastwards. It is cosmopolitan and habitat for over 40% of the 1.3 million national human inhabitants whose livelihood is mainly based on commerce, industry and peri-urban agriculture (including livestock).

The whole country constitutes an ecological niche for tsetse flies and is classified of low tsetse challenge in the western coastal area (actual target area for promotion of the crossbred cattle) to medium in the middle and high to the east - with two main species, i.e., the widespread Savanah Gossina morsitans submorsitans and riveraine G. Palpalis gambiensis.

Urbanisation has had great impact on the environment of this area. It has transformed a one-time dense forest area to large settlements, orchards and gardens, farmland and open shrubby woodland. As a result, 6 remnants of forest are found in some areas such as Abuko Nature Reserve and Pirang Natural Forest Park. The River Gambia, with its fringing mangrove vegetation and the Ocean has great influence on the climate of this area. These hydrological systems give this area a cool weather in the dry season and higher rainfall (>1000mm). In the area, agriculture and the farming system in general are changing as a sequel to the rapid urbanisation. Land for human settlement has encroached into areas left for agriculture and fallow lands formally used for communal grazing of livestock. Consequently less land is available for cropping and livestock production. Most cattle herds that depended on extensive grazing of the natural grasslands have moved into rural areas. On the other hand, the conservation of forest and the creation of orchards also provide the microhabitat for biting flies especially the tsetse fly and ticks, which are vectors of trypanosomosis and other livestock diseases. The management of disease risks vis-à-vis the introduction in such an environment of specialised animals such as crossbred dairy cattle, which are more susceptible to such infections, is an unavoidable exercise. For all these reasons, preliminary studies were conducted on the adaptation, health and productive performances of this new animal population, kept on - station under vigilant health surveillance and improved nutrition conditions.

The second phase of that project, planned to move from station to peri-urban farms, started in The Gambia in 1999 with insemination of 187 N'Dama cows. A subsequent census allowed the identification of forty calves born in 2000. In addition, nine F1 cows that had already completed a lactation on-station were handed over to farmers in the peri-urban area on a loan scheme in 2001. Establishment of F1 cattle at peri-urban farms in Western Division of The Gambia continued henceforth. In addition to the justification given above to the on - station preliminary studies, the emergence of a significant number of F1 on farms dictates the collection of information on their performances and constraints in view to establish yard-sticks for their performance capability, their optimal management and exploitation options in a small-scale peri-urban farming environment.

Materials and Methods

Animal management and data collection

All animals were identified at birth using ear tags. The F1 heifers were reared as a separate group from the age of 12 months. At an approximate age of 20 months, a N'Dama service bull was introduced to, and stayed in the group, throughout. The cows were kept in a large kraal with a shed containing concrete troughs for feed and water. Groundnut (Arachis hypogea) hay (crude protein 12.8% in DM) was offered ad libitum and a concentrate supplement given after each milking.  The concentrate (crude protein 29.8% in DM) , which was a mixture of groundnut cake and rice bran was given to cows at a at flat rate regime whereby all lactating cows received the same quantity daily.

All matings and calvings were recorded. Prophylactic treatment for control of gastrointestinal parasites was given twice during the rainy seasons (from June to October) to calves and heifers. Acaricide treatment for tick control was applied to all categories of animals throughout the year. Vaccination was performed against anthrax, black quarter and haemorrhagic septicaemia, which are endemic. All clinical cases were attended to. At calving, the cow and calf stayed together until after one week when milking began. Milking was done by hand twice daily (i.e., morning and evening). The traditional method of using the calf to suckle for stimulation of milk letdown was practised. In case the calf died, the stockmen conditioned the cow and were able to continue extracting milk from her (something that was not possible to do with the N'Dama cow). Cows were dried eight weeks before parturition. All animals were weighed monthly and the cow milk yield was recorded weekly. All events during the week (e.g., matings, deaths, treatments) were recorded on prescribed forms and computerised.

Data preparation and analysis

At the time that calculations were done, incomplete lactations that were abbreviated for one reason or another, as well as on-going ones that did not allow estimates of at least 100-day milk yield, were excluded. There were 15 lactations that lasted less than 200 days, including 2 that did not last 100 days, and therefore could not allow the calculation for 300-day milk production. Of these 15 lactations 12 were from Jersey (JN) F1 breed (2 of parity 1, 3 of parity 2, 1 of parity 3, 5 of parity 4 and 1 of parity 5) and 3 from Friesian-Holstein (FN) F1 breed (1 of parity 2, 1of parity 3 and 1 of parity 4). These lactations were then excluded from the analysis of 300-day milk yield.

Since milk recording was done weekly, estimation of weekly milk production was done by multiplying the average milk production of two consecutive measurements by the interval. Total milk yield was estimated summing up the weekly estimates. Analysis of variance of milk yields was performed using a General Linear Model (SAS. version 8.0, SAS Institute inc. 1999-2000) with the following models:

M_ijklm =μ + B_i + A_j(B_i) + YC_k + α(u_1ijk - ū₁) + β(u_2ijk - ū₂) + ε_ijklm (model 1)

Where

μ = population mean yield;
B_i = _ith breed (_i=1=FxN, _i=2=JxN);
A_j(B_i) = _jth animal nested within _ith breed;
YC_k = year of calving _k: (_k = 1998, 1999, 2000, 2001, 2002);
α(u_1ijk - ū₁) = regression coefficient of milk yield on age at first calving in days;
β(u_2ijk - ū₂) = regression coefficient of milk yield on calving interval in days;
ε_ijklmn = random error.

M_ijklmn = μ + B_i + A_j(B_i)+ P_k +YC_l + α(u_1ijk - ū₁) + β(u_2ijk - ū₂)+ ε_ijklmn (model 2)

Where

μ = population mean;
B_i = _ith breed (_i=1=FxN, _i=2=JxN);
A_j(B_i) = _jth animal nested within _ith breed;
P_k = _kth parity (_k =1, 2, ...,5);
YC_l = year of calving _l: (_l = 1998, 1999, 2000, 2001, 2002).
α(u_1ijk - ū₁) = regression coefficient of milk yield on calving interval in days;
β(u_2ijk - ū₂) = regression coefficient of milk yield on previous calving interval in days;
ε_ijklmn = random error.

Model 1 was applied to first lactations whereas model 2 was used for second to fifth lactations.

The daily milk yield for each cow in each lactation was estimated as a mean of the daily milk yield of each week of the considered period. In order to determine peak daily milk yield, the incomplete gamma function (equation α) from Wood (1967) and the bi-exponential function (equation β) from Cappio-Borlino et al (1995) were applied to fit the milk yield data of individual lactations. These functions are as follows:

y = a_*x^b_* e^-c*x (α)

y = a_*x^(b_* ^exp(-c*x)) (β)

Where y = daily milk yield in week x from calving, e is the base of natural logarithm, and a, b and c the parameters which characterise the shape of the curve and which were estimated from a non-linear regression analysis using the NLN procedure of SAS (1999-2000). As indicated in the reports mentioned in the section above (Wood 1967; Cappio-Borlino et al 1995), peak yield and time to peak were calculated for each lactation as a_*(b/c) ^b _*e^-b and b/c, respectively.

Persistency was estimated, using the expression

P= (A-B)*100 /B

Where A is the milk yield during the first 180 days and B is the milk yield during the first 90 days (Kozelskii and Ivanova 1981; Danell 1982). Persistency is the key parameter in the lactation curve as it determines the extent to which milk production in early lactation is maintained during the rest of the lactation period. Due to the various types and nature of the data presented for peak, time to peak and persistency, brief descriptive statistics are given on these variables, whereas an analysis of variance of milk yields was performed using a General Linear Model (SAS. version 8.0, SAS Institute inc. 1999-2000) with above-mentioned models including factors such as breed type, animal number nested within breed (since the same number is recorded for several lactations), parity, year of calving, calving interval and previous calving interval (both characterised as covariates) and their interactions. When none of the studied interactions were proven significant, they were all removed from the model.

Results

First lactation

100 - day milk production

All 47 cows that calved could be used to estimate the 100 and 300-day milk yield and the whole lactation milk yield of the first lactation. Twenty lactations were from Friesian type F1 (F x N) and the rest, i.e., 27, from Jersey type F1 (J x N).

The overall average of 100-day milk yield of the total herd was 494 ± 98.2 kg. The highest mean milk yield in 100 days was 543 ± 62.6 kg during the third lactation and the lowest 473 ± 182 kg during the fifth lactation. Of the factors considered only breed (P< 0.005) and animal (P<0.05) had a significant effect (Table 1):

The best performance of a group occurred in 1998 when the 1995 born (F x N) cows produced on average 731 ± 40.7 kg milk in 100 days. The maximum individual performance was 871 kg achieved by an F x N F1 type single born in 1995. The lowest individual performance was 239 kg in 1999 by a J x N F1 type single born in 1996.

A summary of yields during all lactations is given in Table 2.

300 - day milk yield

Out of the 47 F1 cows that calved between one to five times, 38 (16 Friesian type and 22 Jersey F1 type) could be used to estimate the higher lactation (lactation 2 to 5). There were a total number of 120 lactations (44 from the Friesian type F1 and 76 from the Jersey type F1). They were produced between 1999 and 2002.

The overall mean 300 - day period production during first lactation was 1188 kg with a standard deviation of 411 kg (Table 7). Of the considered factors only breed showed a significant difference (P<0.005) as indicated in Table 2. The best performance of a group occurred in 1998 when maximum individual performance was 2152 kg achieved by an (F x N) F1 type single born in 1995. The lowest individual performance in 300 days of first lactation was 466 kg in 1999 by a (J x N) F1 type single born in 1996.

Whole lactation milk production

The overall mean total lactation production was estimated as 1255 kg with a standard deviation of 457 kg. Of the considered factors only breed showed a significant difference (P<0.005). The best performance of a group occurred in 1998 when the 1995 born (F x N) cows produced on average 1898 ± 193 kg milk. The maximum individual performance was 2535 kg achieved by a (J x N) F1 type single born in 1995. The lowest individual whole lactation performance during first lactation was 454 kg in 1999 by a (J x N) F1 type single born in 1996.

All lactations

100 - day milk production

For this analysis 167 lactations (64 and 103 of the Friesian and Jersey F1 types, respectively) from 47 cows (20 Friesian and 27 Jersey F1 types, respectively) were considered. They were produced between 1998 and 2003.

The mean overall 100 - day period production was estimated at 494 kg with a standard deviation of 158 kg (Table 9). No significant differences were found between lactations though the third (the highest) exceeded by 53 kg the first (lowest). The best performances of a group was 731 ± 46.6 kg achieved in 2000 by a (F x N) F1 type group born single in 1995. The maximum individual performance was 993 kg achieved by an F x N F1 type single born in 1995 during third lactation. The lowest individual performance was 131 kg in 2002 by a J x N F1 type single born in 1996 during fifth lactation. Table 4 shows results of the analysis of variance:

300 - day milk production

The mean 300 - day production was estimated at 1167 kg with a standard deviation of 348 kg. Of the factors considered, only breed was significant (P<0.001). When compared, the five lactations of successive parities, though not significantly different, appeared to follow a typical « bell » curve the second and third being the epicentric points. The best performances of a group was 1672 ± 104 kg achieved during first lactation in 1998 by a (F x N) F1 type group born single in 1995 . The maximum individual performance was 2295 kg achieved by an (F x N) F1 type single born in 1995 during third lactation. The lowest individual performance was 346 kg in 2000 by a J x N F1 type single born in 1996 during second lactation.

An analysis of variance was performed and the results are shown in table 5:

The whole lactation herd overall mean production was 1189 kg with a standard deviation of 458 kg. With respect to studied factors, a significant effect could be detected for breed (P<0.005), animal within breed (P<0.05) and year of calving (P<0.001) as shown in Table 5. Though there were no significant differences between lactations, it could be noticed that the second lactation had the highest yield, out-producing the first, third, fourth and fifth by 85.3 ± 110 (P = 0.439), 44.4 ± 119 (P = 0.711), 142 ± 124 (P = 0.256) and 352 ± 156 kg (P = 0.026), respectively. The best performance of a group occurred in 1998 when the 1995 born (F x N) cows produced on average 1770 ± 125 kg milk during first lactation. The maximum individual performance was 2685 kg achieved by a (J x N) F1 type single born in 1996 during second lactation. The lowest individual whole lactation performance during first lactation was 303 kg in 2002 by a (J x N) F1 type single born in 1996 during fourth lactation. The results of the analysis of variance are shown in Table 6.

Table 7 gives a summary of milk yields of the two breed types during their different lactations: