In spite of the large amounts of money invested in research, breeding, and the improvement of commercial egg-type strains, high environmental temperature (HET) has been identified as a major non-genetic constraint limiting expression of their full genetic potential. This environmental stressor has been implicated in adverse marked effects on egg production and eggshell quality of hens. Reports have conclusively indicated that poor performance (i.e. drop in egg production and poor eggshell quality) of layers reared in thermally-stressed environments could be adduced to a complex interplay of low feed intake, malfunctioning of the endocrine system, acid-base imbalance and poor physiological functioning of organs and mechanisms connected with the entire egg production process, via follicular recruitment and growth, ovulation, egg formation, shell formation, egg development, oviposition and oviposition interval.

SummaryPhenotypic description helps in assessing the physical attributes of species and is also an indicator of the relevance and importance attached to such attributes in their natural environments. This study was conducted to describe patterns and distribution of phenotypic diversity in Nigerian Muscovy ducks. One thousand and twenty (1 020) adult male and female Muscovy ducks reared extensively were randomly drawn from the Rain Forest, Derived Savanna and Guinea Savanna agro-ecological zones/ecotypes and were visually appraised and scored for plumage, skin, shank, feet/web, bill, bean and caruncle colours. Data on qualitative traits were analysed with descriptive statistics (percentages) while fixed effect model was used to investigate relationship between plumage and skin colours and body weight. Results revealed variations in qualitative traits; however, across ecotypes, the predominant plumage, skin, shank, feet, bill, bean and caruncle colours were mottled (45 percent), white (88 percent), yellow (50 percent), yellow (60 percent), black (58 percent), black (69 percent) and red (84 percent), respectively. Besides, significant (P < 0.05) association was observed between plumage and skin colours and body weight. The reported variations in phenotypic traits of Nigerian Muscovy ducks indicate diversity in their genome, absence of selection and the need for their selection and improvement.

Morphometric parameters and their indices are central to the understanding of the type and function of livestock. The present study was conducted to predict body weight (BWT) of adult Nigerian Muscovy ducks from nine (9) morphometric parameters and seven (7) body indices and also to identify the most important predictor of BWT among them using regression tree analysis (RTA). The experimental birds comprised of 1,020 adult male and female Nigerian Muscovy ducks randomly sampled in Rain Forest (203), Guinea Savanna (298) and Derived Savanna (519) agro-ecological zones. Result of RTA revealed that compactness; body girth and massiveness were the most important independent variables in predicting BWT and were used in constructing RT. The combined effect of the three predictors was very high and explained 91.00% of the observed variation of the target variable (BWT). The optimal regression tree suggested that Muscovy ducks with compactness >5.765 would be fleshy and have highest BWT. The result of the present study could be exploited by animal breeders and breeding companies in selection and improvement of BWT of Muscovy ducks.

SUMMARYThis study was designed to investigate the possibility of classifying Nigerian Muscovy ducks into distinct ecotypes using stepwise discriminant analysis and Euclidean distance. Data were collected on ten morphological traits (body weight, body length, body girth, wing length, shank length, shank circumference, thigh length, total leg length, bill length and bill width) of one thousand and twenty (1020) adult Muscovy ducks comprising 203, 598 and 289 randomly sampled ducks from the rain forest, derived savanna and Guinea savanna ecotypes, respectively. The results of the descriptive statistics revealed highly (p<0.001) significant effects of ecotype on eight of the morphological traits except bill width and body length. Stepwise discriminant analysis indicated that bill length and body length had highest discriminating powers among the six distinguishing variables. Result of the cross validation of the correct assignment of ducks into distinct ecotypes was low; 53.7, 41.8 and 42.3 % of samples drawn from the rain forest, derived savanna and Guinea savanna ecotypes were correctly classified into their expected ecotypes. Euclidean distance between ecotypes was small; shortest distance was between rain forest and derived savanna ducks (2010) while the longest distance (3758) was between rain forest and Guinea savanna ducks. It is evident that due to the low classification success rate of discriminant analysis and short Euclidean genetic distance between ecotypes, they could not be classified into distinct ecotypes on the bases of morphostructural traits and appreciable heterosis is practically impossible from crossing Nigerian Muscovy ducks originating from different ecotypes. RESUMENEste estudio fue realizado para investigar la posibilidad de clasificar los patos Muscovy nigerianos en distintos ecotipos utilizando el aná-lisis discriminante secuencial y la distancia euclidiana. Se obtuvieron datos de diez caracteres morfologicos (peso, longitud y perímetro corporal, longitud del ala, longitud y circunferencia del tarso, longitud del muslo, longitud total de la pierna, longitud y anchura del pico) de 1020 patos Moscovy adultos obtenidos al azar en los ecotipos de bosque lluvioso (203), de sabana derivada (598) y de sabana de Guinea (289). La estadística descriptiva reveló (p<0,001) la influencia del ecotipo sobre ocho de las medidas estudiadas, exceptuando la amplitud del pico y longitud corporal. El análisis discriminante secuencial puso de manifiesto que el mayor poder discriminante corresponde a las longitudes del pico y del cuerpo. La validación cruzada puso de manifiesto una baja asignación correcta a los correspondientes ecotipos; el 53,7; 41,8 y 42,3 % de las muestras fueron atribuidas correctamente a los ecotipos bosque lluvioso, sabana derivada y sabana de Guinea respectivamente. La distancia euclidiana entre ecotipos resultó pequeña, la más corta se Archivos de zootecnia vol. 63, núm. 243, p. 484. OGUNTUNJI AND AYORINDE registró entre el ecotipo bosque lluvioso y el savana derivada (2010) mientra...

SummaryCharacterization and genetic diversities among members of a species are fundamental to their improvement and conservation. This study was conducted to characterize and estimate genetic diversity in the ecotypes of the locally adapted Muscovy duck in Nigeria using blood proteins (haemoglobin, transferrin and albumin) and enzyme (carbonic anhydrase) markers. Blood samples collected from 20, 40 and 20 adult Muscovy ducks sampled randomly from the Rain Forest, Derived Savanna and Guinea Savanna ecotypes, respectively, were typed for blood proteins and enzyme polymorphism with cellulose acetate paper. Genetic variability in the studied population was accessed using heterozygosity (H), effective number of allele (ne) and polymorphism (percent P). All the 13 allelic variants expressed at the four loci were expressed in the Derived Savanna ecotype but 12 each in the Rain Forest and Guinea Savanna ecotypes. Results showed that all the four loci were polymorphic (100 percent) and the estimated heterozygosity among them was similar (0.424–0.481). Similarity in the estimated genetic variability parameters among ecotypes indicate that the sub-populations understudy was under similar evolutionary forces and there were no appreciable differences among them.