Harmonizing genetic type and environmental level in dual-purpose cattle herds in Latin America

Bibliography

L. Vaccaro, R. Vaccaro, O. Verde, H. Mejías, L. Rios and E. Romero

Work on Venezuelan Farms 1, 2, 3 and 4 was carried out thanks to financial support from the International Development Research Centre,

Ottawa, Canada, and with administrative assistance from the Inter-American Institute for Cooperation on Agriculture, Caracas, Venezuela.

The authors also express their gratitude to the farmers whose generous collaboration made the research possible.

The authors may be contacted at the Facultades de Agronomía and Ciencias Veterinarias, Universidad Central de Venezuela, Maracay, Venezuela.

After virtual complete neglect by Latin American scientists, dual-purpose animals are now becoming recognized as an excellent basis for cattle production systems in the lowland tropics. They are estimated to account for about 75 percent of the continent's tropical dairy cow population, and in some countries they produce over 90 percent of the total milk. Production from specialized dairy breeds is decreasing because of excessive costs, and beef cattle are being drawn increasingly into milking herds in an effort to intensify production. The challenge is to promote sustainable systems that are both attractive to the producer and able to maintain consumer prices at levels accessible to Latin America's high, and expanding, proportion of urban poor.

Dual-purpose systems are generally based on grazing and hand-milking of cows with the calf at foot; nevertheless, they vary widely in intensity, particularly with regard to the relative importance of natural and cultivated pastures, supplementary feeding with crop residues or concentrates, drinking-water supply, health control measures and overall management. Similarly, the range of genotypes employed is very large, combining genes from many zebu (Bos indicus), criollo and European (Bos taurus) breeds. In one sample of 20 Venezuelan herds, 63 different genetic groups were identified, with ten or more together on 12 of the farms. This partly reflects a genuine lack of information as to the comparative merits of different genotypes for the overall production of milk and meat in the environments involved. In common with scientists in other disciplines, animal breeders in some parts of the world have paid little attention to dual-purpose cattle up to now (Table 1), and their efforts contrast strikingly with the numerical and socio-economic importance of the dual-purpose populations. This paper attempts to summarize recent information on the comparative performances of the major genetic groups under different conditions, which should assist planners and producers to match genotypes more suitably to the resources available for systems of different intensities.

1. Distribution of papers on genetics and breeding presented at scientific meetings in Latin America by species and production system
1. Ventilation, par espèce et par système de production, des documents sur la génétique et la sélection présentés à des réunions scientifiques an Amérique latine
1. Distribución de estudios sobre genética y mejoramiento presentados en reuniones científicas de América Latina, por especies y sistemas de producción

Species/production system		Percentage of total
Cattle
	- Specialized: dairy	37.6
	beef	39.7
	- Dual purpose	4.2
Pigs		7.9
Sheep and goats		6.6
POULTRY		1.9
Others		2.1
Total (529 papers)		100.0

1. Comparative profits from four different grades of European x zebu crossbred cows at two management levels in Brazil - Comparaison des rendements obtenus avec quatre types de vaches croisées européennes x zébu a deux niveaux de conduite de l'élevage au Brésil - Beneficios comparativos de cuatro clases de cruzamiento de vacuno europeo y cebú a dos niveles de explotación en Brasil

An important element of recent work by Latin American animal breeders has been the effort to combine biological and economic information in performance analyses, or at least to provide data on a range of traits to produce a clearer picture of overall merit than that resulting from traditional studies devoted to one or two production characteristics. Wilkins et al. (1979) were pioneers in this regard. They combined biological and economic data to demonstrate that local crossbred cattle in the Bolivian lowlands were more profitable than European imported purebreds, chiefly because of their higher survival and reproduction rates, as well as lower production costs. More recently, two other studies have led to similar conclusions. The first of these was carried out by Madalena et al. (1990a; 1990b; 1993) in Brazil, where different groups of European x zebu crossbreds, as well as European purebreds, were distributed to commercial farms. The herds were classified according to two levels of management medium and high - which supported 2 450 and 1 731 kg per cow, respectively, in the first lactation without calf suckling.

The data summarized in Figure 1 show the results in terms of profit per day of herd life for four of the genetic groups. A clear advantage may be seen for the 1/2 European animals at both levels of management. The greater economic benefit of the medium level for all breed groups is also illustrated. The low-grade 1/4 European crosses, which are typical of many traditional systems produced reasonable profits at the medium level, but as they could not respond to environmental improvements they were the least profitable of all groups at the higher management level. In contrast, the European purebreds at the medium level generated the heaviest losses of all genotypes included in the study. These changes in ranking were quantified in the statistical analysis, with significant interactions between breed group and management level for a range of traits related to milk yield, milk-solids content and calving interval.

The economic benefits of the 1/2-European group were mainly the result of their high milk yields per day of calving interval, superior survival rates and lower production costs. Even though the economic value of males over ten years of age was not taken into account, experience suggests that their inclusion would have inclined the results even more strongly in favour of the intermediate group and against the higher-grade European animals.

Strong support for these results was obtained in a second study, by Holmann et al. (1990) in Venezuela. Using survey data from 157 herds, cattle were classified as European purebred cows on highland farms and as approximately high- or medium-grade European x zebu crosses on lowland farms. Mean milk yields in the lowland herds averaged about 2 650 kg per cow per year and were thus similar to those obtained at the higher level of management in the Brazilian case. As shown in Table 2, medium-grade crosses in the lowland systems generated the highest annual net margins per cow. The gross income figures for beef production are of special interest because of the scarcity of this kind of information in the literature. They highlight once again the advantages of the medium-grade crosses, which now also include longer herd life combined with lower fixed and variable costs. Table 2 also highlights the contrast between the high gross income from milk of the European cows in the highlands and their relatively low net margins. These results help explain why milk production throughout tropical Latin America tends to be displaced from specialized herds in the highlands to dual-purpose systems in the lowlands.

Both the above studies were carried out in environments capable of supporting milk yields in the order of 1 750 to 2 500 kg per lactation or more. This is well above the national average yields in Latin American tropical countries which range from 240 kg (Haiti) to 1 930 kg (Cuba) per cow per year, with an overall mean of 958 kg (FAO, 1990). It is therefore also important to examine the more traditional systems, to identify the range of responses in existing livestock to improvements in feeding and management and to attempt to define the conditions necessary for crossbreds to become more productive.

In search of more information, four herds (Farms 1 to 4) with widely differing levels of management and in which the three main cattle breed groups were represented were chosen for study in the Venezuelan lowlands (Vaccaro et al., 1993). The first group comprised zebu and low-grade European crosses, classified together as zebu type, while medium- and high-grade European crossbreds formed the other two groups. Typical representatives of each type on Farm 2 in the rainy season are shown in Figures 2, 3 and 4. The environmental differences between the farms were partly attributable to differences in rainfall distribution, with six to seven months of dry season on Farms 1, 2 and 3, compared with less than three months on Farm 4. Farm 1 relied heavily on natural pastures and maize or sorghum stubbles with no supplementary feeding, and inadequate health programmes and a shortage of drinking-water in the summer were evident. Conditions were better on Farms 2 and 3, while on Farm 4 the cattle were kept permanently on sown pastures with moderate supplementary feeding and good health control programmes. Overall mean lactation milk yields ranged from 678, 822 and 1 010 kg (with calf suckling) on Farms 1, 2 and 3, to 2 461 kg (without suckling) on Farm 4, therefore, conditions on Farm 4 are likely to be similar to those covered by the Venezuelan survey and by the higher management level in the Brazilian study. Farm 4 was defined as dual-purpose, even though calves were reared artificially as all males are reared for sale as beef.

The results showed significant breed group/farm interactions for milk yield and days open. As indicated in Figures 5 and 6, this was mainly because of the very low milk yields of the high-grade cows on Farms 1 and 2, which had the lowest overall mean yields, and because of their comparatively poor reproductive performance on Farms 3 and 4. There was little change in the ranking of the breed groups for calf weight (Figure 6), with the high-grade dams generally at a disadvantage. It was also found that the high grades were exceedingly sensitive to the calving season. Their milk yields in lactations initiated by wet season carvings were 22 percent lower than those started in the dry season, whereas the difference between seasons in the other two breed groups was less than 3 percent.

2. Gross incomes and net margins of different breed groups on 157 farms in three ecological zones in Venezuela
2. Revenus bruts et marges nettes que procurent différents groupes de races dans 157 élevages et dans trois zones écologiques du Venezuela
2. Ingresos brutos y márgenes netos de distintos grupos de razas en 157 granjas de tres ecozonas de Venezuela

Breed group	Ecological zone
	Highland	Lowland
		Wet	Dry
	Gross income from milk:*
European (KU)	664
European x zebu crossbreeds
- High-grade (H)	-	341	366
- Medium-grade(M)	-	331	423
	Gross income from beef:*
Eu	48	-	-
H	-	93	85
M	-	97	108
	Overall net margin:**
Eu	116
H	-	135	13
M	-	160	165

Source: Holmann et al., 1990.
* US$/cow/year.
** Net margins calculated after deduction of 30 percent subsidy on concentrate feeds.

The results obtained for Farm 4 coincide well with the Brazilian as well as the Venezuelan survey data (Figure 1 and Table 2), suggesting that medium-grade crossbreds are more productive than either lower or higher grades in environments capable of supporting yields as high as 2 500 kg per lactation. However, Figure 5 also shows that this was not the case on the three farms with average milk yields of about 1 000 kg or less per lactation. If correction was made for the milk consumed by the calves, the total mean yields would probably have been approximately 1 000 to 1 500 kg per lactation on Farms 1, 2 and 3. Under these circumstances, the zebu-type cows compared favourably with the medium grades for milk yield, days open and calf weight, and they may well have been more profitable because of their lower initial market value. Complementary information on calf mortality and nine-month live weights taken from these and neighbouring herds (Table 3) suggests a possible additional slight advantage for the zebu dams in terms of total weight of saleable calf.

2. A zebu-type cow on Farm 2, typical of those used as bull dams. This animal produced 269 kg more milk, 34 fewer days open and 3 kg more four-month calf weight per calving than contemporaries of all other breed groups - Vache de type zébu dans l'exploitation 2, représentative des mères à taureaux. Par rapport à ses contemporaines de tous les autres groupes, cette vache a produit 269 kg de lait en plus, est restée vide 34 jours de moins et le poids des veaux à 4 mois était supérieur de 3 kg - Un vacuno del tipo cebú, que habitualmente se utiliza para la cría, en la Explotación 2. Este animal producía 269 kg más de leche, con 34 días menos de no preñez libre, y 3 kg más de peso en los terneros de cuatro meses por parto que sus contemporáneas de todos los grupos de razas

3. A medium-grade European x zebu crossbred cow on Farm 2. Fifth in order of merit for milk yield in a herd of 280 cows, this one had 801 kg more milk, 52 more days open and 12 kg more four-month calf weight per calving compared with contemporaries of all other breed groups - Vache issue de croisements entre une souche européenne de niveau moyen et un zébu dans l'exploitation 2. Classée cinquième dans un troupeau de 280 vaches pour le rendement laitier, par rapport aux contemporaines, tous croisements confondus, cette vache a produit 801 kg de lait en plus, est restée vide 52 jours de plus et le poids des veaux à 4 mois était supérieur de 12 kg - Cruce de clase media de vacuno europeo y cebú en la Explotación 2. Quinta en la clasificación por rendimiento de leche en un hato de 280 vacunos, dio valores de más de 801 kg de leche, más de 52 días de no preñez y más de 12 kg del peso del ternero de cuatro meses por parto, frente a sus contemporáneas de todos los grupos de razas

4. A typical high-grade European crossbred cow on Farm 2, negative for milk yield, fertility and calf weight - Vache issue de croisement avec une souche européenne sélectionnée dans l'exploitation 2; elle a des performances négatives tant pour le rendement laitier que pour la fertilité et le poids des veaux - Un cruce típico de vacuno europeo de alta calidad en la Explotación 2; se han registrado resultados negativos en lo que respecta a la producción de leche, fecundidad y peso de los terneros

5. Comparative milk yields of three grades of European x zebu crossbred cows on four farms with different management levels in Venezuela (values are based on least square means, n=1843) - Comparaison du rendement laitier de trois types de vaches issues de croisement entre une souche européenne et un zébu dans quatre élevages appliquant un niveau de conduite différent au Venezuela (les valeurs sont fondées sur la moyenne des moindres carrés, n = 1 843) - Comparación del rendimiento de leche de las tres clases de cruces de vacuno europeo y cebú en cuatro explotaciones con diferentes niveles de explotación en Venezuela (los valores están basados en el método de las medias de mínimos cuadrados, n = 1843)

6. Comparative fertility and four-month calf weights of three grades of European x zebu crossbred cows on four farms with different management levels in Venezuela (values are based on least square means. n = 1843) - Comparaison de la fertilité et du poids des veaux à 4 mois entre trois types de vaches issues de croisement entre une souche européenne et un zébu dans quatre élevages appliquant un niveau de conduite différent au Venezuela (les valeurs sont fondées sur la moyenne des moindres carrés, n = 1843) - Fecundidad comparativa y pesos de los terneros de 4 meses de tres clases de cruces de vacuno europeo y cebú en cuatro explotaciones con diferentes niveles de explotación, en Venezuela (los valores están basados en el método de las medias de mínimos cuadrados, n = 1843)

3. Calf mortality and body weights in Venezuelan dual-purpose herds according to breed group of dam
3. Taux de mortalité et poids corporel des veaux des troupeaux vénézuéliens à aptitudes mixtes selon le groupe de race auguel appartient la mère
3. Mortalidad y peso corporal de los terneros en hatos de doble finalidad de Venezuela. según el grupo de raza de la madre

Trait	No.	Breed group
		Zebu type	Crossbreeds
			Medium grade European	High -grade European
Mortality (%)
0-4 months	2035	4.9	9.3	10.0
Body weight (kg)
Birth	495	32	34	34
4 months	796	67	67	63
9 months	1209	129	125	124

4. Ranges of estimated breeding values of "best' and "worst" cows for three traits in Venezuelan dual-purpose herds
4. Etendues de valeurs génétiques estimatives des «meilleures» et des «moins bonnes» vaches des troupeaux vénézuéliens à double fin selon trois caractères
4. Márgenes de los valores estimados de reproducción de las vacas «mejores» y «peores» con respecto a tres características, en rebaños de Venezuela de doble finalidad

Farm	Overall milk yield (Kg/lactation)	Estimated breeding value*
		Milk yield (kg)		Days open		Calf weight (kg)**
		Max.	Min.	Max.	Min.	Max.	Min
A	601	+143	-81	+23	-26	+5	-5
Ba	678	+ 200	- 139	+ 31	- 24	+ 11	- 6
C	781	+156	-153	+21	-10	+14	-24
D	818	+171	-236	+47	-24	+9	-8
Eb	822	+ 142	- 204	+ 50	- 25	+ 7	- 24
F	974	+ 849	- 286	+ 43	- 15	+ 9	- 16
Gc	1 010	+198	-119	+59	-18	+10	-6
H	1 117	+289	-180	+57	-14	+6	-5
I	1 971	+ 333	- 358	+ 33	- 14	+ 9	- 7
J	2 294	+ 527	- 474	+ 163	- 18	-	-
Kd	2461	+1 195	-508	+28	-15	-	-
L	2 860	+ 392	- 420	-	-	-	-
M	3 016	+ 653	- 694	+ 48	- 23	-	-
N	3316	+487	-551	+27	-15	-	-

Source: Vaccaro et al., 1993.
* Calculated as nk²/{[1+(n-1)r]} D, where n = number of records, h² = heritability, D = deviation of individual records from contemporary averages and r = repeatability for each trait.
** Corrected four-month weight.
^a,b,c,d Farms 1,2,3 and 4, respectively.

The results described here point consistently to the merit of medium-grade European x zebu crosses for use in improved dual-purpose systems, where total milk yields are from 1 750 to 2 500 kg per lactation. Few tropical countries have the resources to base sustainable systems on levels of production higher than this. The results from Farms 1, 2 and 3, however, emphasize that crossbreeding for dual-purpose cattle production is not justifiable until environmental improvements are made and may indeed be economically detrimental. The numbers of inappropriate crossbreds on farms such as these throughout tropical Latin America demonstrate that this apparently well-recognized principle is not yet fully understood.

Once improved environments and suitable crossbred cattle are brought together, the results suggest that milk yields per lactation can be approximately doubled without apparent detriment to other essential traits. The evidence is quite clear that high grades of European crossbreeds have no advantage in these systems.

It may be argued that the data presented for the medium-grade crosses are of limited practical interest since F₁ animals cannot be generated continuously. While the Brazilian case referred specifically to F₁ crosses, the two Venezuelan studies classified the breed groups mainly according to appearance, therefore, the medium grades were probably quite mixed genetically. It is often possible to produce F₁ replacements for dual-purpose farms in a continuous fashion, using limited proportions of zebu herds kept on more marginal lands. Otherwise, practical mating systems that will maintain crossbred herds at an approximately intermediate level must be devised. Along with rational selection programmes with emphasis on bull dams in pilot herds, much can be done to achieve performance levels that, though possibly less than those achieved by F₁S, are still superior to those of any other genetic option. The enormous scope for selection in ordinary herds is illustrated in Table 4, which gives the range of estimated genetic values for the "best" and "worst" cows on 14 Venezuelan farms, including Farms 1 to 4. Wide variation between individuals is evident for all traits, even on the farms with lower levels of management, as judged by their average milk yields.

Emphasis must be placed firmly on practical mating and selection schemes rather than on ideal programmes that are too difficult to implement at farm level. Unproductive cows must be identified as such and culled. Research is in progress on the production of F1 (and other crossbred) bulls from genetically superior local dams and proven B. taurus sires, so that advantage may be taken of the continuous genetic progress in the temperate B. taurus populations and the need for local progeny testing minimized. Cows such as that shown in Figure 2 serve as dams, and the use of artificial insemination and performance recording is restricted to the bull-breeding herds.

The major challenge, therefore, is to intensify efforts to recognize the existence of the substantial interactions between genotype and environment that influence performance and to achieve a consensus on the goals and nature of lowland production systems. Cattle must be evaluated suitably for tropical conditions and matched to the level of available resources if sustainable production is to be achieved. Simple genetic principles can be harnessed to produce animals capable of greatly improving the status of human welfare on the continent.

Bibliography

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Madalena, F.E. 1993. A simple scheme to utilize heterosis in tropical dairy cattle World Animal Rev., 74-75: 17-25.

Madalena, F., Lemos, A.M., Teodoro, R.L., Barbosa, R.T. & Monteiro, J.B.N. 1990a. Dairy production and reproduction in Holstein-Friesian and Guzera crosses. J. Daily Sci, 73: 1872-1886.

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Mora, B., Vaccaro, L., Vaccaro, R., Verde, O., Alvarez, R., Mejías, H., Ríos, L. & Romero, E. 1992. Pérdidas de becerros hasta cuatro meses de edad en rehangs de doble propósito. VIII Congreso Venezolano de Zootecnia, Maturin: GR 12.

Vaccaro, L., Vaccaro, R., Verde, O., Alvarez, R., Mejías, H., Pérez, A., Ríos, L. & Romero, E. 1993. Dual purpose cattle breeding (Venezuela). Informe Técnico (Diciembre 1991-Diciembre 1992). Proyecto UCV/CIID/IICA, Facultades de Agronomía y de Ciencias Veterinarias, Universidad Central de Venezuela, Maracay. 27 pp.

Wilkins, J.V., Pereyra, G., Ali, A. & Ayola, S. 1979. La producción de leche en los llanos tropicales de Bolivia. Rev. Mundial de Zootecnia, 32: 25-31.