The effect of genetic upgrading of Kenana (Sudan Zebu cattle) with European Friesian of calf performance, milk yield and milk composition

Deux expériences ont été réalisées afin de déterminer l’effet du croisement de la race indigène Kenana avec 50 ou 75 p. 100 de race Frisonne sur la aerformance des veaux. la nroduction et la comnosition du lait. Dans l’expérience 1, la consommation de matière sèche, le gain de poids vif et l’indice de consommation ont été étudiés avant et après le sevrage. Concernant la consommation de matière sèche, aucune différence significative n’a pu être mise en évidence entre les deux groupes de génotypes. En revanche, durant la période de présevrage, le poids vif est statistiquement plus éleve chez les croisés Frison à 75 u. 100 aue chez les croisés Frison à 50 a. 100. tandis aue durant la p&iode de post-sevrage, il est signiiïcati;ement plus élevé chez les croisés à 50 p. 100 que chez ceux à 75 p. 100. En ce qui concerne l’indice de consommation. les croisés Frison à 50 D. 100 nrésentent des valeurs supérieures à celles des croisés à 75 p. iO0 duiant la période de pré-sevrage, tandis qu’il est plus élevé chez les croisés à 75 p. 100 que chez ceux à 50 p. 100 durant la période de post-sevrage. Dans l’expérience II, les vaches Kenana croisées avec 50 p. 100 de Frison ont produit significativement plus de lait que les croisés à 75 p. 100, mais avec une teneur moins élevée en matitres grasses et en protéines. Les meilleures performances ont généralement été enregistrées chez le génotype à 50 p. 100 Frison. Il apparaît ainsi que les plans de croisements futurs devront faire l’objet d’une gestion attentive. Mots clés : Bovin Frison x Kenana Croisement Veau Sevrage Croissance Production laitière Lait Teneur en lipides Teneur en protéines Soudan.


INTRODUCTION
It is now a widely accepted practice in many countries in the tropics to upgrade the indigenous dairy cattle by crossing with exotic temperate breeds to improve the productivity of the former. In these countries much information has been gathered and published on the performance of the crossbreds regarding parameters like milk yield, lactation length, age at first calving and calving interval (3,10,14,19,31). Amongst the other important traits in dairy cattle are viability and milk composition.
In a recent review on crossbreeding 60s indicus and Bos faurus for milk production in the tropics, CUNNINGHAM and SYRS-TAD (9) indicated that records on such parameters have rarely been reported.
The Kenana cattle is a subtype of the Northern Sudan Shorthorn Zebu (130s indicus) introduced many centuries ago with migrants from Asia (6, 17). They are generally considered to have resulted from interbreeding with Sanga cattle and Shorthorn Zebu (25). The average milk yield of large herds has been reported to be 1 500 kg/lactation (8). Mature cows may be 130 cm high at shoulder and weigh up to 450 kg. They are light blue grey with graduation from nearly white to steel grey and they are found East of the confluence of the Blue and White Niles as far as the Ethiopian border (26). The crosses described in this work result from artificially inseminated Kenana cows with impotted Friesian semen from Great Britain. The aim of the present work was to study the calf performance, milk yield and composition of 50 and 75 % Friesian upgraded Kenana (Sudan indigenous Zebu) cattle. The investigation was carried out in the Central Region of the Sudan where a developing dairy industry is being based on crossbred cattle.

MATERIALS AND METHODS
Two experiments were carried out at the University of Gezira Farm (latitude 14"30', longitude 33'39') during the years 1985 to 1987. Experiment I was carried out during the period of January 1985 to March 1986. The average temperature and humidity during this period was 31 "C and 42.5 %, respectively. Experiment II was carried out during the period January to March 1987, the average temperature and relative humidity during which was 26.9 "C and 32.3 %, respectively.
In experiment 1, Friesian x Kenana crossbred calves were used to study the effect of genotype on feed intake, liveweight gain and feed conversion efficiency by calves up to the age of 26 weeks. In experiment II, milk yield and composition (fat and protein) were studied in Friesian x Kenana crossbred cows.  After delivery, the calves were weighed and transferred to individual feeding pens where they received colostrum by nipple pail feeding system within, at most, one hour. The quantity of colostrum offered in the first 4-6 h was about 10 % of the calves' birthweight. Colostrum feeding continued for 48 h. The calves were then bucket-fed from their mothers' milk for the following five days after which they received farm milk till weaning. The daily amount of milk was given in two equal portions, one in the morning and one in the evening. The calves were weaned at ages of 6, 8, 10 and 12 weeks. Starter concentrate rations composed of cottonseed meal, groundnut meal, wheat bran, molasses, oyster shell and common salt providing 175 g/kg DM of crude protein and 11.4 MJ/kg DM metabolizable energy (ME) were introduced to the calves at the end of their first week of age and continued till weaning. During the post-weaning period, the calves were reared collectively in group pens. Supplement rations composed of the same dietary ingredients as those used for the starter rations were used. However, the diet provided a crude protein content of 155 g/kg DM and 11.3 MJ/kg DM (ME). Table I shows the ingredients and their chemical composition (starter and supplement feeds). Forage sorghum (Sorghum vulgarae var. Abu70) was offered to the calves. The forage was daily tut in the preblooming stage and offered fresh and green. The daily feed intake and fortnightly liveweight were recorded. This period continued till the age of 26 weeks. All calves were vaccinated against rinderpest, blackquarter, haemorrhagic septicaemia and anthrax. They were sprayed weekly with an acaricide against ticks.

Animals and management
Fourteen milking cows were used in this experiment. Ten cows were 50 % Friesian, 50 % Kenana while the other four were 75 % Friesian, 25 % Kenana. All the cows were; in their third lactation and were hand-milked twice daily at, 03:OO and 13:OO h. Milking was initiated by offering the~ concentrate diet and was carried out at the milking par-i leur. The animals were kept in a spacious shaded pen The cows were let to graze from 09:OO to 12:OO hic Grazing was on swards of Berseem (Trifolium alexanch-, num L.) and Clitoria (Chtoria ternafae). In addition to gra-' zing, a concentrate ration composed of wheatbran (530 g/kg), groundnut meal (350 g/kg), molasses' (100 g/kg), minera1 and vitamin supplements (20 g/kg),' providing 250 g/kg DM crude protein was offered. The' quantity of concentrate per cow was calculated according~ to its milk production. Individual milk yields were recor-~ ded. The experimental period lasted 75 days.

Chemical analysis
The chemical composition of the feeds was determined~ by proximate analysis according to the standard methods adopted by the A.O.A.C. (4).
An aliquot sample of milk was taken from each cow in the morning every three days, during the whole period of the experiment. The milk samples were analysed for fat and protein (N x 6.38) by the standard Gerber's and formol (formaldehyde reaction) methods, respectively.

Statistical analysis
The data in experiment I were analysed by analysis of variante using Duncan's Multiple Range Test according to STEEL and TORRIE (30). T-Test was used for the analysis of the data in experiment II according to .

RESULTS
The effect of genotype (75 and 50 % Friesian Zebu crosses) on feed consumption and performance of the~ crossbred calves during the whole experimental period is shown in table II. During the preweaning period (O-12 weeks) the dry matter intake which included that of milk, supplement and forage, although it was slightly higher for the 75 % Friesian group showed no significant difference between the two genotypes. However, the 75 % Friesian genotype showed a significantly (P c 0.001) higher live; weight gain than the 50 % Friesian group. On the other hand, the feed conversion ratio was significantly (P c 0.01) higher for 50 % than for 75 % Friesian crosses.' During the postweaning period (12-26 weeks), there was no significant difference in dry matter intake between both genotypes. The 50 % Friesian group of calves showed a significantly (P' c 0.001) higher liveweight gain than the 75 % Friesian group. Feed conversion ratio was signifi-ZOOTECHNIE, GENETIQUE ET REPRODUCTION cantly (P c 0.01) higher and favourably (P c 0.001) lower for 50 % than for 75 % Friesian crosses, during the preweaning and postweaning periods respectively.
The mean values of milk yield, fat and protein for both groups of genotypes are shown in table III. The 50 % Friesian group produced a significantly (P c 0.001) higher milk yield than the 75 % Friesian group. On the other hand, the fat and protein content of their milk was significantly (P c 0.001) lower than that of the 75 % Friesian group.

DISCUSSION
The results of this study show a significant effect of the genotype on the growth of calves over both the preweaning and postweaning period. BHAT et a/ (5) reported that in Friesian Zebu crosses the genotype had a significant effect on body weight at all ages. In the study reported here, 75 % Friesian calves showed a significantly higher growth in the preweaning period than the 50 % crosses. PLANAS PEREZ (23) reported that growth rate was higher up to 12 weeks for the 75 % Friesian than for others. When considering the growth of the calves over the whole period of study (26 weeks) 50 % Friesian calves had a significantly higher growth than 75 % Friesian calves. Perhaps with time the 75 % Friesian became less able to withstand climatic conditions and  (11) reported that the slow growth rate of purebred Holstein calves in the tropics was due to the inability of such breeds to withstand the climatic conditions and the restriction of feed due to the inability of such animals to metabolize properly, at high temperatures, enough feed for normal existence. Other workers (22, 32) stated that the superiority of halfbred over 3/4 foreign blood animals was due to their high hybrid vigour. The results of this study is in agreement with the findings of RATHORE (24) who reported that 50 ,% Friesian, 50 % Zebu had faster growth than 75 % Friesian, 25 % Zebu. Also our results confirm the findings of ALRAWI and SAID (2) who found that daily gain decreases as the percentage of the Friesian blood increases. In this study the feed conversion efficiency was found to be significantly better for 50 % than for 75 % Friesian crosses in the postweaning period (12-26 weeks) and over the total period.
The results of this study show that 50 % Friesian crosses cows produced a significantly higher. milk yield than 75 % Friesian crosses. This agrees with what had been reported by NARAYANASWAMY (21) when he compared Friesian-Sahival crosses (1/2, 5/8 :and 3/4 Friesian) and found that the superiority of the total milk yield was in the order of half Friesian > 5/8 Friesian >.3/4 Friesian. ALBA and KENNEDY (1) showed that the Fl (Criollo x Jersey) crosses were superior to the Criollo breed and 1/4 Jersey. In India SHARMA et a/ (28) found that with 1/8, 1/4, 1/2. 5/8 and 3/4 Friesian blood, the average milk yield was higher for 1/2 Friesian than for the other groups. KALE et a/ (12) in their studies with different grades of Holstein-Friesian by Gir and Sahiwal crosses concluded that there was no advantage in increasing the Holstein-Friesian inheritance beyond 50 %. The same conclusion was reached earlier by NAIR (20) when crossing Zebu cattle with Brown Swiss.  (18), analysing data on a farm of Jersey and Jersey x Sahiwal showed that the crosses produced 16 % more milk than the purebreds. With Ayrshire and Sahiwal x Ayrshire crosses KIMENYE and RUSSEL (13) reported higher milk yield for the 50 and 75 % Ayrshire than for the high-grade Ayrshire and they concluded that a "fair portion of Bas indicus genes is desirable in this environment".
In the coastal region of Tanzania, MAHADEVAN and HUTCHINSON (16) comparing a range of crossbreds of Bos indicus and Bos taurus showed that the 50 % Bas taurus cross had slightly higher milk yield than the 25 and 75 % crosses.
The records collected from Northern Nigeria involving White Fulani and Friesian were analysed by BUVANENDRAN et a/ (7) and they showed that the milk yield in all lactations of the 50 % crosses of the two breeds exceeded the 75 % Friesian crosses by 100 % (287 kg vs 143 kg). On the other hand, the milk yield in the first and second lactation of Ndama and Jersey crosses in the Ivory Coast was higher for 75 % than for 50 % crosses Jersey crosses (15).
Although the 75 % cross benefit regarding milk production levels was clearly visible after the second lactation, the lack of resistance of these crosses towards the wet tropical environment made no progress beyond the 50 % cross with the Ndama x Jersey cattle and numerous health problems occurred from the third lactation (15). CONCLUSION It was shown that over the 26-week study period, the growth of 50 % Friesian calves was significantly faster than that of 75 % Friesian calves. It was also shown that 50 % Friesian cows exhibited a significantly higher milk yield but a lower milk protein and milk fat content than the 75 % Friesian CO~S. Hence, under the conditions of this study the 50 % Friesian crosses seemed to perform better than the 75 % crosses. These results indicate that future upgrading plans should be carefully and cautiously monitored. (B.A.), MOHAMED (T.M.), AL1 (T.E.). Efecto del cruce de ganado Kenana (ganado cebii de SudAn) para el mejoramiento genético del desarrc$lo de 10s terneros y de la production y composici6n de leche. Revue Elev. Méd. vét. Pays trop., 1992, 45 (3-4) : 329-333 Se llevaron a cabo dos experimentos con cruces de ganado Frison x Kenana, con el fin de estudiar 10s efectos de cruces a1 50 p. 100 y 75 p. 100 de ganado nativo, sobre el desarrollo de 10s terneros, la produccion y la composici6n de la leche. En el primer experimento se estudi6 el consuma de materia seca, la ganancia de peso y la tasa de conversion alimenticia en terneros pre y post destete. No se encontr6 una diferencia signifîcativa en cuanto a la ingestion de materia seca entre 10s dos genotipos.