Population Structure Assessed Using Microsatellite and SNP Data: An Empirical Comparison in West African Cattle

A sample of 185 West African cattle belonging to nine different taurine, sanga, and zebu populations was typed using a set of 33 microsatellites and the BovineHD BeadChip of Illumina. The information provided by each type of marker was summarized via clustering methods and principal component analyses (PCA). The aim was to assess differences in performance between both marker types for the identification of population structure and the projection of genetic variability on geographical maps. In general, both microsatellites and Single Nucleotide Polymorphism (SNP) allowed us to differentiate taurine cattle from zebu and sanga cattle, which, in turn, would form a single population. Pearson and Spearman correlation coefficients computed among the admixture coefficients (fitting K = 2) and the eigenvectors corresponding to the first two factors identified using PCA on both microsatellite and SNP data were statistically significant (most of them having p < 0.0001) and high. However, SNP data allowed for a better fine-scale identification of population structure within taurine cattle: Lagunaire cattle from Benin were separated from two different N’Dama cattle samples. Furthermore, when clustering analyses assumed the existence of two parental populations only (K = 2), the SNPs could differentiate a different genetic background in Lagunaire and N’Dama cattle. Although the two N’Dama cattle populations had very different breeding histories, the microsatellite set could not separate the two N’Dama cattle populations. Classic bidimensional dispersion plots constructed using factors identified via PCA gave different shapes for microsatellites and SNPs: plots constructed using microsatellite polymorphism would suggest the existence of weakly differentiated, highly intermingled, subpopulations. However, the projection of the factors identified on synthetic maps gave comparable images. This would suggest that results on population structuring must be interpreted with caution. The geographic projection of genetic variation on synthetic maps avoids interpretations that go beyond the results obtained, particularly when previous information on the analyzed populations is scant. Factors influencing the performance of the projection of genetic parameters on geographic maps, together with restrictions that may affect the election of a given type of markers, are discussed.

PRE-AND POST-WEANING PHENOTYPIC RELATIONSHIP BETWEEN SOME N'DAMA CATTLE UNEAR MEASUREMENTS IN THE TROPICS

Data collected on 1438 male and 1492 female pure bred N'Dama calves calved between 1948 and 1961 at Fashola Stock farm were used to study the relationship between five N'Dama cattle linear measurements at pre and post Weaning ages. The measurements were Head to Shoulder (HDS); Shoulder to tail drop (STD); Height at withers (HTW); Heart girth (HGT) and Body length (BLT). All measurements had positive values which ranged from 0.2 - 91 except HTW and HDS which had a negative value (-02) in males at yearling age. There was a predominance of positive and highly significant relationship (P<0.01) between height measurement (HTW) and circumference measurement (HGT) which ranged from .04 - .76 with pre weaning measurements having higher values (.69 - .76) in both sexes. High and positive correlation values were also observed between length measurements (HDS, STD and BLT) which therefore shows that only one of such measurements is sufficient for length measurement Generally measurements taken at pre weaning had higher correlation values than those taken at post weaning.

Influence of inbreeding and some environmental factors on calving intervals in N'Dama cattle of Southwest Nigeria

Records of 4184 N'Dama calves born between 1947 and 1984 at Fashola Stock Farm, Oyo State, Nigeria was used to compute inbreeding coefficient and determine its effects on calving intervals of cows. Only 273 of the 4184 calves (6.53%) were inbred with an average inbreeding coefficient of 9.71%, while five out of 293 sires had inbreeding coefficient of 9.25% and 43 out of 1849 dams had inbreeding coefficient of 9.95%. The inbreeding coefficient for the entire population was 0.63%, respectively 0.70% and 0.58% for male and female calves. The average calving interval was 445.34 ± 2.68 days within the herd while year of birth, parity of dam, age of dam and dam's age at first calving all significantly (P<0.05) impacted calving intervals of cows. Season of birth and inbreeding coefficient of dam did not exert statistical (P>0.05) influence on calving intervals of dams. Although the number of inbred animals in the population is relatively low, however the inbreeding level of these animals is high, which may be attributed to the fact that breeding policy on the farm was not strictly adhered to, and lack of proper and adequate registration system coupled with inconsistent animal identification system on the farm may be responsible for the inbreeding observed in the N'Dama population at Fashola Stock Farm.

Multivariate Analysis for Morphological Characteristics of N’Dama Cattle Breed in Two Agro-ecological Zones of Côte d’Ivoire

Information on morphological characteristics is a prerequisite to sustainable breed improvement, utilization, and conservation. In this study, 108 N’Dama cattle cows from 11 farms of central and northwestern regions of Côte d’Ivoire were described using visual appreciation criteria and linear body measurements. The variables were studied using principal component analysis (PCA) and discriminant analysis. Results indicated that the most common N’Dama is fauve (83.33%) and it has straight back profile (69.44%) and lyre horn (74.07%). Agroecological zone has a significant (p˂0.01) effect on linear body measurements of N’Dama. The central region animals had higher head width (18.94 ± 2.18 cm), skull length (22.51 ± 2.18 cm), skull width (16.51 ± 1.72 cm), muzzle circumference (40.83 ± 2.58 cm), distance between horns (15 ± 1.90 cm), ear length (17.46 ± 2.57 cm), chest length (160.11 ± 15.8 cm), chest depth (71.55 ± 7.41 cm), and body length (125.13 ± 12.22cm) than those of northwestern region N’Dama. Thus, their respective values were: 15.41 ± 2.85 cm, 18.62 ± 2.6 cm, 12.44 ± 3.94 cm, 38.8 ± 2.61 cm, 13.72 ± 1.52 cm, 16.41 ± 1.61 cm, 143.84 ± 8.35 cm, 65.25 ± 4.1 cm, and 119.18 ± 12.38 cm. PCA revealed that N’Dama morphometric variability performed from the 9 variables (Lt, lt, Lc, lc, pt, hg, Pth, Lcp and Lf) were more associated with the first two factors. In regards to the discriminant analysis, these 9 variables distinguished the N’Dama significantly (p˂0.05) into two populations that corresponds with the two agroecological zones.

Effects of insemination timing and GnRH treatment on pregnancy rates of N’Dama cattle after estrus induction with progestin

Le but de cet essai clinique a été de quantifier les pourcen­tages de gestation de bovins N’Dama (n = 168) trypanotolé­rants après traitement avec un dispositif intravaginal libérant de la progestérone (CIDR ; 1,38 g de progestérone) inséré pen­dant sept jours. Une injection intramusculaire (IM) de prosta­glandine (500 μg de cloprostenol) a été administrée deux jours avant le retrait du dispositif. Par la suite, une injection IM de 400 UI de gonadotrophine chorionique équine (eCG) a été administrée lorsque le dispositif a été retiré. Les animaux ont été inséminés 48 (groupe 1) et 72 heures (groupe 2) après le retrait du CIDR. Dans les deux groupes, la moitié des animaux ont été traités avec 4,2 μg d’acétate de buséréline et l’autre moitié avec 1 ml de sérum physiologique. Quatre protocoles ont ainsi été testés : CIDR-PG-eCG/IA48h, CIDR-PG-eCG/ IA48h/GnRH+, CIDR-PG-eCG/IA72h et CIDR-PG-eCG/IA72h/ GnRH+. Un diagnostic de gestation a été réalisé par échogra­phie 45 à 60 jours après l’insémination. Le pourcentage de gestation moyen a été de 37,5 %. Celui des vaches adultes (43,2 %, n = 111) a été significativement (p < 0,03) plus élevé que celui des génisses (26,3 %, n = 57). Le pourcentage de gestation a été significativement plus élevé (p < 0,002) chez les animaux du groupe 2 (48,8 %) que chez ceux du groupe 1 (26,2 %). L’état physiologique et l’injection de GnRH au moment de l’insémination n’ont pas eu d’impact significatif sur le pourcentage de gestation. Le protocole hormonal utili­sant CIDR-PG-eCG (400 UI) et une insémination systématique 72 heures après ont amélioré les pourcentages de gestation chez la femelle N’Dama.