ORIGINAL ARTICLE

Milk production and reproduction in cows with different proportions of Bos taurus x Bos indicus genes

Producción de leche y reproducción en vacas con diferentes proporciones de genes Bos taurus x Bos indicus

Arelis Hernández, Raquel E. Ponce de León

ABSTRACT

In order to evaluate genetic and environmental factors that influence on milk production and reproduction in cows with different proportions of Bos taurus x Bos indicus genes, an amount of 19,643 lactations of Mambí de Cuba (3/4 Holstein ¼ Zebu) cows and 15,925 lactations of Siboney de Cuba (5/8 Holstein 3/8 Zebu) cows were used, which belonged to three cattle farms, during the parturition years, from 1987 to 2012. The studied traits were accumulated milk production up to 305 d (L305), lactation duration (LD), milk production per day (MPD), period between parturition and gestation (PPG), period between parturitions (PP) and milk production per day during the period between parturitions (MPPP). A linear mix model was applied with the use of MIXED procedure of SAS. Fixed effects included genetic groups, herd, lactation number, year, parturition season, interactions of genetic group x lactation number, genetic group x parturition year and genetic group x parturition season. The cow nested in the herd and the error were considered as random effects. Mambí de Cuba and Siboney de Cuba cows showed similar reproductive performance and lactation duration. However, milk productions were superior in Mambí de Cuba cows in 84.43 kg, 0.29 kg/d and 0.69 kg/d, for L305, MPD and MPPP, respectively. It can be concluded that there was better milk performance in Mambí de Cuba and similar averages for reproductive periods and lactation duration.

Key words: milk production, reproduction, genetic groups, environmental effects.

RESUMEN

Para evaluar los factores genéticos y ambientales que influyen en la producción de leche y la reproducción de vacas con diferentes proporciones de genes Bos taurus x Bos indicus se utilizaron 19 643 lactancias de vacas Mambí de Cuba (3/4 Holstein ¼ Cebú) y 15 925 lactancias del Siboney de Cuba (5/8 Holstein 3/8 Cebú), pertenecientes a tres ganaderías, durante los años de parto 1987 - 2012. Los rasgos estudiados fueron la producción de leche acumulada hasta 305 d (L305), duración de la lactancia (DL), producción de leche por día (LPD), intervalo parto gestación (IPG), intervalo entre partos (IPP) y producción de leche por día de intervalo entre partos (LIPP). Se aplicó un modelo lineal mixto mediante el uso del procedimiento MIXED del SAS. Como efectos fijos se incluyó el grupo genético, rebaño, número de lactancia, año, época de parto, interacciones grupo genético x número de lactancia, grupo genético x año de parto y grupo genético x época de parto. Los aleatorios fueron la vaca anidada dentro del rebaño y el error. Las vacas Mambí de Cuba y Siboney de Cuba mostraron similar comportamiento reproductivo y duración de la lactancia. Sin embargo, las producciones lecheras fueron superiores en el Mambí de Cuba en 84.43 kg, 0.29 kg/d  y 0.69 kg/d, para L305, LPD y LIPP, respectivamente. Se concluye que hubo mejor comportamiento lechero en el Mambí de Cuba y promedios similares para los intervalos reproductivos y la duración de la lactancia.

Palabras clave: producción de leche, reproducción, grupos genéticos, efectos ambientales.

INTRODUCTION

Development of new breeds is a very important resource for genetic improvement in tropical areas (López 1982). In Cuba, the program of genetic improvement for milk production started in the 60´s. It pursued the formation of new breeds from two more adapted breeds to the country: Zebu and Criolla (López & Ribas 1993). For the creation of Mambí de Cuba (3/4 Holstein 1/4 Zebu) and Siboney de Cuba (5/8 Holstein 3/8 Zebu), wide populations based on Zebu and semen of imported Holstein bulls, with high breeding values, were taken. Inter se mattings with selection were conducted to stabilize each crossing.

Crossings are a simple method to increase health and efficiency of plants and animals because they allow to introduce favorable genes from other breeds, remove depression caused by consanguinity, maintain genic interactions causing heterosis and complementarity (VanRaden & Sanders 2003). Most of females destined to milk production in Cuba, which belong to genetic herds, are crossbred animals. Out of them, 56.4% of all the females from milk producing breeds, included in genetic herds, are Siboney de Cuba and Siboney crosses, 15.5 % belong to Mambí de Cuba and Mambí crosses and 6.5% is Holstein. Genetic improvement is aimed to these breeds.

Several studies have been related to milk production and reproduction of Siboney de Cuba and Mambí de Cuba (Ribas et al. 2004, González et al. 2008, Fernández & Tronco 2011, Hernández et al. 2011, Portales et al. 2012). However, there are no studies that evaluate the animals of both breeds together under production conditions, with the objective of comparing the advantages of the use of one or the other breed proportion. The objective of this study was to evaluate genetic and environmental factors that influence on milk production and reproduction of cows with different proportions of Bos taurus x Bos indicus genes.

MATERIALS AND METHODS

Records of milk production and reproduction of genetic groups of Mambí de Cuba (3/4 Holstein ¼ Zebu) and Siboney de Cuba (5/8 Holstein 3/8 Zebu) were used, from digital information from the Centro Nacional de Control Pecuario (CENCOP). These records, from 1987 to 2012, belong to animals from three cattle enterprises (Empresa Pecuaria Genética de Matanzas, Camilo Cienfuegos and Los Naranjos), located at the occidental region from the Republic of Cuba.

The feeding system of cows was based on grazing. Lactating cows consumed, mainly, star grass (Cynodon nlemfuensis), pangola grass (Digitaria decumbens) and guinea grass (Panicum maximum), and some natural grasses. After 2000, the introduction of Penisetum purpureum cv. Cuba CT-115 began, which was destined to grazing and as strategic reserve during drought periods. From 2001, the offering of dehydrated dry grains with solubles (DDGS), at a rate of 0.46 kg/L since the second liter produced, approximately.

During dry period, it was supplemented with sugar cane (Saccharum officinarum), king grass (Penisetum purpureum) in form of forage and citric peel, according to availability. Urea and mineral salts were part of the complementary feeds, according to the requirements of the diet.

Lactations with less than 100 d (4.57 % of data) were eliminated, as well as with parturition ages inferior to 24 months (0.31 % of data), milk productions with less than 300 kg (3.98 % of data) and lactations superior to the tenth (0.16% of data). The combination herd-year-parturition season was considered as contemporary groups. Parturition season was grouped in rainy (from May to October) and dry (from November to April).

Studied sample showed 35,568 lactations, from 13,270 cows. Out of them, 19,643 lactations corresponded to Mambí de Cuba (7,089 cows) and 15,925 to Siboney de Cuba (6,181 cows). The studied traits were accumulated milk production up to 305 d (L305), lactation duration (LD), milk production per day (MPD), period between parturition and gestation (PPG), period between parturitions (PP) and milk production per day during the period between parturitions (MPPP). The MPD was estimated as the quotient of L305 between LD and the MPPP was calculated as the quotient of L305 between PP. 

A mix linear model was applied through the use of MIXED procedure of SAS, 9.3 version (SAS Institute 2013). This model included fixed effects of genetic group, herd, number of lactation, year, parturition season, and interactions of genetic group x lactation number, genetic group x parturition year and genetic group x parturition season. The cow nested in the herd and the error were considered as random effects. The used model was:

Y_ijklmn= µ+ G_i+ R_j+ NL_k+ AP_l+ EP_m+ (GxNL)_ik + (GxAP)_il + (GxEP)_im + V_n(R_j) + e_ijklmn

Where:

Y_ijklmn= vector of cow observations,

µ= common means for all the observations,

G_i= fixed effect of the i-th genetic group of the cow (i= 1, 2)

NL_k= fixed effect of the k-th number of lactation (k=1,…, 10)

AP_l= fixed effect of the l-th year of parturition (l= 1987,…, 2012)

EP_m= fixed effect of the m-th parturition season (m=rainy, dry)

(GxNL)_ik = effect of the interaction of i-th genetic group of cow with the k-th lactation number (ik=1,..,20)

(GxAP)_il = effect of the interaction of i-th genetic group of cow with the l-th parturition year (il=1,..,52)

(GxEP)_im= effect of the interaction of i-th genetic group of cow with the m-th parturition season (im=1,..,4)

V_n(R_j) = random effect of the n-the cow (n=1, …,13 270) nested in the j-th herd (j= 1,…, 216) ~ NID (0, σ²v),

e_ijklmn= random error associated to each observation ~ NID (0, σ²e).

RESULTS AND DISCUSSION

The analysis of variance (table 1 and 2) showed that studied fix effects were significant, except the effect of genetic group on lactation duration, period between parturition and gestation and period between parturitions, as well as the effect of the interaction of genetic group and parturition season, in which none of the studied traits were affected.

Herd effect was significant in all the studied traits. This performance may be caused by differences on management of milking groups, instability in the staff that performs this task and services, together with the variations in feeding due to availability and quality of grasses. It may be also caused by differences in the amount of grazing areas presenting paddocking and to the presence of breed groups with different potential for milk production, among other factors.

Estimated averages for traits of milk production and reproduction of Mambí de Cuba and Siboney de Cuba (table 3) cows show similar reproductive performance and lactation duration. However, milk productions of Mambí de Cuba were superior to those of Siboney de Cuba with 84.43 kg, 0.29 kg/d and 0.69 kg/d for L305, MPD and MPPP, respectively.

These results are in agreement with those of Ponce de León et al. (1988), who compared 424 first and second lactations of 5/8H x 3/8Z, ¾ H x ¼ Z and purebred Holstein through the use of a sample of 80 animals per genotype, in two cattle farm. Crossings had high potential for milk production (4,018 and 3,692 kg for ¾ H x ¼ Z and 5/8H x 3/8Z, respectively), superior to Holstein (3,533 kg) and good reproductive performance. There were no differences among crosses in liveweight and reproduction but milk production favored 3/4H 1/4Z. Holstein performance was affected due to their coexistence with the other crossed animals, mainly in the worst herd. Regarding the crossings, there were three times more losses due to reproductive and health problems up to the third lactation.

Researches conducted by López et al. (2009), in three herds of crossed bovines (¾ Holstein (H) x ¼ Zebu (Z), ¾ Brown Swiss (S) x ¼ Z, 1/2H x 1/2Z y 1/2S x 1/2Z) in Veracruz, Mexico, showed that the racial group also had significant effect on milk production. Cows of ¾H x ¼C cross showed better milk production per lactation and moderate performances in lactation duration, days open and periods between parturitions, compared to other racial groups, with an increase of 51.4, 50.8 and 29.5 % in milk production per lactation, time at the peak of lactation and lactation duration, respectively. These cited authors attribute this performance to the improvement of the environment due to the inclusion of concentrate complements and to milking management without the support of calves.

Results of this study coincide with those of Hernández et al. (2000), who, in a study in the Mexican tropic, reported that genotype (1/2 Holstein x ½ Zebu, ½ Brown Swiss x ½ Zebu and ½ Holstein x ¼ Brown Swiss x ¼ Zebu) had a significant effect on milk production, but it did not affect the period between parturitions. However, these results have no agreement with those of López et al. (2010), who evaluated the reproductive performance in different crosses of Bos taurus x Bos indicus in Mexico. These authors confirmed that, with increase of the percentage of Bos taurus genes, there was also an increase in the period between parturitions. In this respect, López et al. (2006, 2009)  stated, in previous studies, that the increase of  PPG in animals with higher proportion of Bos taurus genes is partially explained by the increase of milk production of these genotypes. In this research, despite of obtaining the best milk production in ¾ H x ¼ Z animals, regarding the 5/8 H x 3/8 Z, it had no negative influence on its reproductive performance, which evidenced the adaptation ability of this genotype to tropical environment.

Parturition season also affected all the traits studied in Mambí de Cuba and Siboney de Cuba cows, with higher means during dry season (table 4). A difference of 75 kg for milk production, in favor of dry season, was mainly because the environment during this season was fresher, which favored an appropriate metabolic comfort for milk production. Similar results were confirmed in other studies under different tropical conditions (García 2005, López et al. 2009). Regarding reproductive periods, it was concluded that those animals that delivered during rainy season showed shorter PPG and PP, with differences of 6.8 d regarding dry season. This performance agrees with reports of López et al. (2010) in different Bos taurus x Bos indicus crossings, in a Mexican commercial cattle farm, but with higher differences, 50 and 30 d for PPG and PP, respectively. This response is basically related to a higher food availability, which favors reproductive activity.

Regarding those studied genetic groups, it is necessary to analyze differences among them, taking into consideration lactation number and years of study because the interaction of genotype x lactation number and genotype x parturition year affected all the studied traits.

The effect of genotype x lactation number interaction on lactation duration showed differences among the studied genotypes during the third (282.12 ± 2.83 days vs. 293.93 ± 3.18 d) and fourth lactation (274.83 ± 2.93 d vs. 288.49 ± 3.34 d). Siboney de Cuba showed better lactations than Mambí de Cuba for the third and fourth lactation, with 11.81 and 13.66 d, respectively. However, studies conducted by López et al. (2009) in cows with different proportions of Bos taurus genes, and by Salamanca & Bentez (2012) in crossbred cows, demonstrated that lactation number had no influence on lactation duration.

Period between parturition and gestation (figure 2) only differed among genotypes of the first parturition (278.21 ± 7.21 d vs. 315.96 ± 6.82 d), with higher means for Siboney de Cuba. There was a similar performance in the period between parturitions, with differences in the first parturition and higher means for Siboney de Cuba (588.21 ± 6.81 d) regarding Mambí de Cuba (557.17 ± 7.19 d). In both breed groups, there was a progressive decrease of the period between parturition and gestation, and between parturitions, with increase of parturition number. This performance may be, generally, a consequence of the removal of cows with reproductive difficulties from the herd. García et al. (2002, 2003), López et al. (2010) also confirmed  a reduction on the period between parturitions, while parturition number increased.

The highest milk production were obtained in the period 1987-1990 (figure 3), with higher means in Mambí de Cuba cows, which surpassed those of Siboney in 935, 541, 622 and 633 kg every year. However, there was a general tendency to decrease in both breeds, which could have been motivated by a fast increase of the amount of animals. In the period of 1991-2001, similar results were obtained, with a tendency to radical decrease of production in general. This can be explained because this period corresponds to a time of economic limitations in Cuba, in which inputs decreased and could not maintain a consistent supply of feedstuff to lactating cows, so food was mainly based on pasture, without irrigation or fertilization. 

From 2002 to 2007, there was slight increase of productions and differences among breeds were observed. Mambí de Cuba from 2002 to 2004 was superior, with means of 1,850.30 ± 44.30, 1,917.56 ± 50.65 and 1,761.85 ± 35.41 kg. During the period between 2005 and 2007, Siboney de Cuba had higher productions with means of 1,717.45 ± 37.03, 1,969.33 ± 35.60 and 2,019.82 ± 33.64 kg.  In the period of 2008-2009, the performance was similar. In 2012, the Siboney de Cuba obtained higher averages (1,757.67 ± 34.12 kg) than Mambí de Cuba (1448.85± 32.07 kg).

Mejía et al. (2010) reported that the effect of year on milk production is difficult to explain, because it is usually a result of incorporation and exit animals, of their exposure to favorable environments during some years and unfavorable during others. It may also be a result of staff, management and administrative changes.

Lactation duration showed an irregular performance. There were only differences in the averages of both breeds in 1993 (242.46 ± 5.32 d vs. 298.06 ± 8.19 d), 1997 (280.80 ± 4.25 vs. 347.45 ± 4.57 d), 1998 (291.96 ± 4.51 d vs. 322.17 ± 4.90 d), 2004 (315.91 ± 3.88 d vs. 276.77 ± 3.88 d), 2009 (254.66 ± 3.39 d vs. 276.12 ± 3.54 d) and 2011 (263.39 ± 3.42 d vs. 283.42 ± 3.41 d). During these years, lactation duration was superior in Siboney de Cuba, except in 2004.

Values of the period between parturition and gestation (figure 4) were similar in the period from 1987 to 1990, with averages of 72.20 ± 19.31 and 128.07 ± 25.46 d. From 1991, these values increased and reached the highest averages in 1993, with 403.03 ± 10.81 d in Mambí de Cuba and 471.41 ± 10.87 d in Siboney de Cuba.

Later, they began to decrease. The remarkable increase of reproductive periods during this time was mainly caused by feeding limitations previously referred, which caused difficulties in cows to get pregnant, because, according to Peron (1975), there is an interaction between nutrition and the appearance of heat.

There were also problems of abortions and management. Reproduction was performed by direct mating, which affected the increase in the number of services per gestation. In the period 1996-2012, averages were between 152.73 ± 9.25 and 225.09 ± 9.52 d for Mambí de Cuba and between 117.00 ± 9.28 and 270.99 ± 10.63 days for Siboney de Cuba. In the studied period, there were only differences between breeds in 1998, averaging 213.64 ± 9.10 d for Mambí de Cuba and 270.99 ± 9.63 d for Siboney de Cuba, which corroborates a similar reproductive performance between the two breeds.

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Received: 2/2/2016 ]]> Accepted: 1/7/2016

Arelis Hernández, Instituto de Ciencia Animal, Apartado Postal 24, San José de Las Lajas, Mayabeque, Cuba. Email: arelishdez@ica.co.cu