Productive performance of F1 compared with other 50% European-zebu crossbred cows for dual purpose systems in the Venezuelan tropics

Lucía Vaccaro, Armando Pérez and Rodolfo Vaccaro

Universidad Central de Venezuela, Facultades de Agronomía y de Ciencias Veterinarias,
Maracay, Venezuela

The performance of Holstein-zebu (F1H) and Brown Swiss-zebu cows F1 (F1BS) was compared with that of mixed inter se (MIS) crossbreds of 50% European-zebu inheritance, using 5054 records from 10 dual purpose farms in Venezuela. The F1H cows were mainly progeny of 41 USA Holstein bulls of positive genetic value for milk yield, while most BS bulls were of unknown or average genetic merit. The MIS cows were progeny of crossbred bulls of various genotypes, generally unselected for performance traits. Records included lactation and 244-day milk yield, days in milk, days open, calf weight at 4 months and calf mortality from birth to 4 months. Data were analysed using linear models which included the effects of breed group (3), farm (10), calving year (1989...1997), calving season (wet, dry), calving number (1..6+), and the first order interactions involving breed group.

Overall adjusted mean values (± SE) were 1637 ±35 kg total lactation yield, 1436 ±27 kg 244-day yield, 246 ±5 days in milk, 139 ±5 days open, 60 ±0.7 kg calf weight at 4 months and 8.6 ±1.6% calf mortality. The only significant breed group effects were found for milk yield (P <0.01) and days in milk (P <0.05), but the breed group x farm interaction was highly significant for these traits and days open. The HF1 ranked first for milk yield on nine of the ten farms. Overall, they exceeded the MIS and F1BS cows by 19% and 14%, respectively, for total milk yield and by 10% and 13% for days in milk, and showed no disadvantage for any trait. There were no significant differences in performance between the F1BS and the MIS cows. Coefficients of variation were closely similar for all groups.

It was concluded that F1 cows may offer an important advantage over commercial-type inter se crosses. The 19% increase in milk yield per lactation of the F1H cows may well compensate the practical disadvantages of the mating system required to produce them. However, the F1BS results showed that the advantage of the F1's does not always occur and may depend on the European breed used, and/or the quality of the sires within the breed. The use of MIS cows offers important practical advantages, especially for small farms, and their performance should be improveable through more systematic selection. There was no evidence that the performance of the progeny of crossbred bulls is unusually variable for traits of importance in dual purpose systems.

Key words: Dual purpose, F1, crossbreeding, milk yield, fertility, mortality

Se comparó el comportamiento productivo de vacas F1 Holstein-cebú (F1H), F1 Pardo Suizo-cebú (F1PS) y cruces mixtos inter se (MIS), de 50% herencia europea-cebú, usando 5054 registros de 10 rebaños venezolanos de doble propósito. Las vacas F1H fueron mayormente progenie de 41 toros Holstein estadounidenses con evaluaciones genéticas positivas para la producción de leche, mientras que las F1BS fueron mayormente hijas de toros de valor genético promedio o desconocido. Los padres de las MIS fueron toros cruzados de varios genotipos, generalmente no seleccionados por producción. Se incluyó información sobre la producción de leche por lactancia y ajustada a 244 días, días en ordeño, intervalo entre parto y concepción, pesos de becerros a 4 meses de edad y mortalidad de becerros entre nacimiento y 4 meses. Los datos se analisaron con modelos lineales, incluyendo los efectos de grupo racial (3); finca (10); año (1989...97), época (seca, lluviosa) y número de parto (1...6+), más las interacciones involucrando grupo racial. Los valores medios ajustados (± ES) fueron 1637 ±35 kg de leche por lactancia, 1436 ±27 kg de leche en 244 días, 246 ±5 días en ordeño, 139 ±5 días entre parto y concepción, 60 ±0.7 kg peso de becerro y 8.6 ±1.6% mortalidad entre nacimiento y 4 meses. Los únicos efectos significativos de grupo racial fueron observados en el caso de la producción de leche (P <0.01) y días en ordeño (P <0.05), pero la interacción grupo racial x finca fue altamente significativa para éstas características, e intervalo parto-concepción. Las F1H fueron primeras en orden de mérito para la producción de leche en nueve de las diez fincas. En general, ellas superaron a las MIS y F1PS en 19% y 14%, respectivamente, en la producción de leche y en 10% y 13% en días en ordeño, sin mostrar ninguna desventaja en cuanto a otras características. No hubo ninguna diferencia significativa en el comportamiento productivo de las vacas F1B y MIS. Los coeficientes de variación fueron muy similares entre los tres genotipos. Se concluyó que vacas F1 pueden ofrecer ventajas importantes sobre cruces comerciales mixtos inter se. El incremento de 19% en la producción de leche manifestado por las F1H podría compensar las desventajas prácticas del sistema de apareamiento requerido para generarlas. Sin embargo, los resultados de los F1PS mostraron que la superioridad de las F1 no siempre se presenta, probablemente dependiendo de la raza europea y/o de la calidad genética de los toros usados. El uso de vacas MIS ofrece ventajas prácticas importantes, sobretodo para pequeños productores, y su comportamiento podría mejorarse mediante una selección más sistemática. No hubo evidencia de que el comportamiento de la progenie de toros cruzados es anormalmente variable para características de interés en sistemas de doble propósito.

The lack of information on practical mating systems for crossbred herds is an important limiting factor to the genetic improvement of tropical dual purpose populations. The superiority of F1 cows compared to crosses with different levels of European-zebu breeding has been demonstrated in many environments (Madalena 1993), but not all farms have access to F1 replacements. The use of crossbred bulls offers many practical advantages for farmers who wish to maintain their herds at the 50% European-zebu level, and is common practice in Venezuelan dual purpose herds. It is assumed that a decline in performance would result, based on evidence from comparisons between F1 and F2 generations (Cunningham and Syrstad 1987) and results of inter se matings of other grades of cross in Cuba (López 1998) and Brazil (Madalena 1993). However, most of this evidence is based on very small numbers of observations, or data sets where generation number is confounded with time period or selection intensity. It is therefore of practical importance to compare F1 animals with the mixed crossbreds which farmers produce under commercial field conditions. The results should indicate whether the productive advantage of F1´s compensates the practical disadvantages of the mating system required to produce them.

Records were taken from ten dual purpose farms in the Venezuelan lowland tropics. The Latin American dual purpose system has been described by Seré and Vaccaro (1985). All herds were kept on grazing. No feed supplement was given on four farms, and low to moderate levels of concentrates based on byproducts were provided on six farms. The cows were milked by hand with their calves in seven herds, mechanically with calves in two, and without the calves in the tenth. Artificial insemination was used to produce most of the F1 cows, but the milking herds were generally kept with several crossbred bulls simultaneously in uncontrolled natural mating.

The cows included in the study were all of approximately 50% European-zebu breeding. All breed groups were present on all farms and in all years (1989-97) studied.  The F1’s were the progeny of Brahman-type zebu cows and purebred Holstein (H) or Brown Swiss (BS) sires. The BS bulls were mainly of national origin and of unknown or average genetic value for milk yield. The H bulls included some national sires but also 41 US proven sires of medium or high genetic merit for milk yield (Vaccaro et al 1997b). The mixed inter se (MIS) crossbreds were all progeny of crossbred sires and crossbred dams. They were being produced on the farms routinely, well before the start of the period over which data were collected.  Their genetic composition could not be established precisely because of the uncontrolled mating system. . Most of the sires were F1H or F1BS, with the two European breeds about equally represented. Since most bulls were purchased, the F1 and MIS groups would usually not have been related. The MIS sires also included a few F1 European beef-zebu and F2 crosses. In general, the crossbred sires were unselected for performance traits. Because of the uncontrolled mating system, the precise numbers of sires represented in the data is not known. Judging by the approximate numbers in service in each farm/year before and during the period studied (1989-1997), it is estimated that about 50 Holsteins, 20 Brown Swiss and over 100 crossbred sires would have been involved.

A total of 5054 lactation records were used which included information on total lactation milk yield; 244-day milk yield and days in milk. Data also included 4005 records on days open; 3306 records of calf weight at 4 months of age, corrected for age and sex; and 3630 records of calf survival from birth to 4 months of age. The calf data refer to records of the progeny of the F1 and MIS cows, mated to the same crossbred bulls. All milk records were included, irrespective of length. Data were analysed using linear models (Harvey 1988) which, besides breed group (3) and first order interactions involving breed group, included the effects of farm (10), year of calving (1989...1997), calving season (wet, dry), and calving number (1...6+). However, since the object of the study was to determine the effects of breed group, the results relating to the other sources of variation, though presented, are not discussed. Separate analyses were then carried out within each breed group, using the same model except for breed group, to calculate the within-group coefficients of variation.

Table 1 shows the results of the overall analyses of variance for milking traits and days open. Differences due to breed group were found for total and adjusted lactation milk yield (P <0.01), for days in milk (P <0.05), but not for days open. The breed group x farm interaction was highly significant for all traits. In the case of days open, no clear trend could be distinguished but in the case of milk yield the interaction was due to changes in ranking between the BSF1 and MIS groups, according to farm. The F1H cows were consistently superior to the others, ranking first for milking traits in nine of the ten herds studied.

Table 1: Results of the analyses of variance of lactation milk yield, days in milk and days open
	F - values
	Milk yield (kg)		Days	Days
	Total	244 days	in milk		open
Adjusted mean	1637	1436	246		139
± SE	35	27	5		5
n	5054	5054	5054		4005
Source of variation
Breed group (B)	4.9**	6.6**	3.1*		0.1
Farm (F)	310.4**	400.4**	13.8**		79.8**
Calving year (Y)	8.7**	8.6**	8.2**		6.6**
Calving season (S)	5.9**	8.8**	13.5**		1.1
Calving number (N)	11.5**	34.4**	4.9**		75.7**
BxF	2.1**	2.4**	2.5**		2.2**
BxY	1.1	1.6*	1.9*		0.6
BxN	3.4	2.7**	1.5		0.4
** P < 0.01; * P < 0.05

Table 2 summarises the results of the analyses of calf weights and mortality. No significant effect was found for breed group in either case and, although the breed group x farm interaction was significant for calf weight, no interpretable trend could be distinguished.

Table 2: Results of the analysis of variance of calf weight and mortality
	F - values
	Calf weight (kg, 4 months)	Calf mortality (%)
Adjusted mean	69	8.6
± S.E.	0.7	1.6
n	3306	3630
Source of variation
Breed group (B)	1.4	0.4
Farm (F)	242**	7.1**
Calving year (Y)	6.4**	2.7**
Calving season (S)	0.0	6.7**
Calving number (N)	17.0**	0.4
Sex	78.9**	3.8**
BxF	2.9**	1.0
BxY	0.9	0.9
BxN	0.9	1.1
** P < 0.01; * P < 0.05

The performance of the two F1 groups and the MIS cows is compared in Table 3. The outstanding difference was for milk yield, with the F1H cows producing 226 to 290 kg more milk per lactation than the other two groups, in a 25 to 30-day longer lactation. The performance of the F1BS and MIS cows was remarkably similar.

Table 3: Comparative performance traits of F1 and mixed inter se crossbred cows (Mean values and SE)
	Holstein-Zebu F1	Brown Swiss-Zebu F1	Mixed inter se
Cows (n)	1697	1594	1763
Milk yield, (lactation,kg	1809±76a	1583±54b	1519±53b
Milk yield (244 day,kg)	1583±58a	1398±41b	1328±40b
Days in milk	264±10c	234±7d	239±7d
Days open	140±9	139±8	136±7
Progeny
Calf weight (kg, 4 months)	68±2	71±1	69±1
Calf mortality (%, 0-4 months):	10.1±3.3	6.8±2.4	9.0±2.3
a,b Differences between groups significant at P < 0.01; c,d Differences between groups significant at P < 0.05.

Table 4 shows the coefficients of variation for the six traits, which were closely similar across the breed groups. There was no evidence that the MIS cows were more variable than the F1’s with respect to their own performance or that of their calves.

Table 4: Coefficients of variation (%) for performance traits of F1 and mixed inter se crossbred cows and their progeny
	Holstein-Zebu F1	Brown Swiss-Zebu F1	Mixed inter se
Cows
Milk yield:
Total lactation	58.4	59.6	58.5
244 days	52.9	53.7	49.4
Days in milk	43.3	41.0	44.4
Days open	68.1	67.8	61.7
Progeny
Calf weight (4 months)	16.6	17.5	18.7
Calf mortality (0-4 months)	313	353	287

Discussion

The overall adjusted mean milk yield obtained in this study, 1637 ±35 kg in 246 ±5 days, is acceptable for tropical grazing systems with calf suckling and little or no supplementary feeding. The average days open, 139 days, suggesting a calving interval of about 14 months, and calf mortality of 8.6% is also close to expected values (Vaccaro 1989). The mean 4-month calf weight, 69 kg, represents a daily gain of 0.33 kg, but slow growth in dual purpose herds has consistently been found to be a limiting factor (Martínez and Vaccaro 1996).

Earlier evidence from the same population showed that crossbreds with an intermediate grade of European-zebu inheritance performed as well or better than other breed groups in dual purpose systems with widely varying degrees of intensity (Vaccaro et al 1997a). This coincides with results from many other studies (Cunningham and Syrstad 1987; Madalena 1993), although most of them refer specifically to F1 crosses.

The MIS cows described here could not be defined precisely in genetic terms, but they are considered to be representative of the mixed, commercial 50% European-zebu crossbreds which farmers in Venezuela and throughout other parts of the Latin American tropics are producing of their own initiative, with little or no tecnical advice. The great advantage to the farmer is the simplicity of the mating system. Female replacements are produced continually on the farm, which is of major importance in the tropics, and bulls can be used in natural service.

The performance of the MIS group was exceeded only by the F1H cows, but the difference in this case was of major practical importance.The F1H cows produced 19% more milk in 25-day longer lactations with no apparent disadvantage in terms of days open or calf performance. However, the relatively poor results of the F1BS group show that the advantage of F1’s over commercial inter se crosses is not necessarily guaranteed. In the present case, the difference may have been due to the superiority of the Holstein over the Brown Swiss breed for crossing with zebu (Vaccaro 1984), to the genetic merit of the individual sires used, or both. Therefore, care should be taken in setting up programmes for the production of F1's for dual purpose replacements. There is some evidence that Holstein sires of high genetic merit for milk yield may be better suited than average sires, for this purpose (Vaccaro et al 1998).

The production of F1 replacements for dual purpose herds is increasing in beef and large dual purpose farms in Venezuela, and is well established in parts of Brazil (Madalena et al 1997). The fact that records of F1 cows made up 65% of the total sample in the present study (Table 3) indicates that farmers are finding ways to overcome the logistical problems of producing them. The availability of zebu dams is not a limiting factor, providing beef herds participate in the production of replacements for dual purpose farms. In a Brazilian survey, farmers produced F1´s from 63% of their zebu cows (Madalena et al 1997), which is not sustainable but since huge areas of the Latin American tropics are covered by poor grazings unsuitable for milked cows, the supply of zebu dams appears unthreatened. A more serious obstacle is that the production of F1’s in the lowlands depends on artificial insemination (AI), because of sire fertility and genetic quality considerations. In one such program on seven Venezuelan farms, only about 25 F1 heifer calves were raised alive to eight months of age for every 100 zebu dams inseminated, despite a pregnancy rate of 72%, which is high for the tropical lowlands (Vaccaro et al 1997b). Such results underline the difficulty of providing adequate management levels under prevailing conditions.

Whatever the potential benefits of F1’s, many farms in the lowland tropics, particularly small ones, will continue either to have no access to F1 replacements, or to prefer the simplicity of producing their own heifers using crossbred bulls. The fact that the MIS cows performed as well as the F1BS in the present case, with yields well above the national average (FAO 1995) shows that MIS cows provide an option for these farmers which is well worthy of consideration. There was no evidence from this study that the offspring of crossbred bulls was unusually variable for production traits. Although this would not be expected in theory for polygenic traits of relatively low heritability, the results refute a widely popular belief among farmers and technical advisers who have reservations about using crossbred bulls. Far more could be done to improve the performance of MIS groups, compared with the best F1's, if rational selection procedures were systematically applied. Widespread progeny testing seems unlikely to be feasible in the near future, but at least it could be ensured that the crossbred bulls are sons of superior local dams and even of progeny tested Bos taurus sires. Genetics research in this area is urgently needed, especially to fulfill the needs of the small farmers of the region.

In conclusion, the study suggests that F1 cows may produce about 20% more milk per lactation than commercial 50% European-zebu crossbred cows, sired by crossbred bulls. However the advantage was only observed in the case of Holstein crosses, sired by bulls proven positive for milk yield. Brown Swiss F1’s, of presumably average genetic merit for milk, showed no advantage for any trait. There was no evidence that the performance of the progeny of crossbred bulls was any more variable than that of the daughters of purebreds. The superiority of the F1H group observed here may be sufficient to outweigh the practical disadvantages of artificial insemination and the discontinuous mating system required to produce them. But because the logistics of acquiring F1 replacements may present serious problems, especially to small farmers, additional research is required to show how far the performance of the commercial crosses could be improved by applying scientific selection procedures to the crossbred bulls.

The authors express their gratitude to the International Development Research Center (Canada) and the CDCH of the Universidad Central de Venezuela for financial support. They also acknowledge the generous support of the farmers who made the research possible.

Cunningham E P and O Syrstad 1987 Crossbreeding Bos indicus and Bos taurus for milk production in the tropics. FAO Animal Health and Production Paper No 68, FAO, Rome. 90 p

FAO 1995 Year Book (Production), FAO, Rome. 235 p

Harvey W 1988 User´s guide for LSMLMW,PC-1 Version. Ohio State University, Columbus. (mimeo)

López D. 1998 Evaluación de los cruzamientos en las ganaderías de doble propósito. Su desarrollo en Cuba. In: Mejora de la Ganadería Mestiza de Doble Propósito. Eds. González-Stagnaro C, Madrid-Bury N and Soto Belloso E. Ediciones Astro Data, Maracaibo. pp 59-75

Madalena F 1993 La utilización sostenible de hembras F1 en la producción del ganado lechero tropical. Estudio FAO No 111 Producción y Sanidad Animal, FAO, Rome. 87 p

Madalena F, Madureira A P and Silvestre J R A 1997 Características dos cruzamentos F1 para producao de leite em Minas Gerais. Cadernos Técnicos da Escola de Veterinária de la UFMG 18: 41-52

Martínez G and Vaccaro L 1996 Pesos y mediciones corporales de bovinos jovenes y adultos en rebaño de doble propósito. In: XII Cursillo sobre Bovinos de Carne. Eds Plasse D, Peña de Borsotti N and Romero R. Facultad de Ciencias Veterinarias, Universidad Central de Venezuela, Maracay. pp 185-208

Vaccaro L 1984 El comportamiento de la raza Holstein Friesian comparada con la Pardo Suiza en cruzamiento con razas nativas en el trópico: una revisión de literatura. Producción Animal Tropical 9: 93-101

Vaccaro L 1989 Sistemas de producción bovina predominantes en el trópico latinoamericano. In: Panorama de la Ganadería de Doble Propósito en la América Tropical. Eds. Arango Nieto L, Charry A and Vera R. ICA-CIAT, Bogotá, Colombia. pp 29-43

Vaccaro L, Pérez A, Mejías H, Khalil R and Vaccaro R 1997a Cuantificación de la interacción genotipo:ambiente en sistemas de producción con bovinos de doble propósito. In: Conceptos y Metodologías de Investigación en Fincas con Sistemas de producción Animal de Doble Propósito. Eds. Lascano C and Holmann F. CIAT, Cali, Colombia. pp 67-79

Vaccaro L, Pérez A and Vaccaro R 1998 Resultados recientes de investigación sobre el uso de vacas cruzadas en sistemas de doble propósito en Venezuela In: X Jornadas Técnicas de la Ganadería en el Estado Táchira. Eds. Montoni D, Cárdenas A and Parra J. Fondo Ganadero del Suroeste de Venezuela, San Cristobal. pp 83-94

Vaccaro L, Vaccaro R, Verde O, Pérez A, Mejías H and Khalil R 1997b Comparación entre dos clases genéticas de toros Holstein cruzados con cebú para uso en rebaños de doble propósito. Archivos Latinoamericanos de Producción Animal 5 Suplemento 1:467-469

Received 26 January 1999

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