Observation on the Age at First Calving in the Savannah Breeds of Cattle in Northern Nigeria

A total of 35 herds of cattle from 2 inistitutional farms, and 6 privately-owned farms which were semi-intensively managed, and 17 nomadic Fulani herds were studied between January 1984 and December 1993 to evaluate the age of first calving (AFC) in the three major indigenous breeds of the Savannah zone of Northern Nigeria: the White-fulani (bunaji), Sokoto-Gudali (Bokoloji) and red Fulani (Rahaji). The AFC of heifers at first calving ranged from 30 to 42 months (mean, 37±0.57 months) with no breed differences. The AFC of heifers from Semi-intensively managed herds (institutional and privately-owned farms) was 30 to 40 months ( mean, 36±1.05 months) and that from nomadic herds was 33 to 42 months (mean, 37±1.31 months). The much lower AFC range observed in this studycompared to the highervalues (33 – 60 months) reported by pervious investigators is due to the increased awareness of livestock owners for the need to improve feed supplementation for livestock in particular during the dry season. The nomadic herdsmen ensure a ready supply of cereal bran, cotton seed (meal or cake) crop residues such as groundnut and bean hulls, corn stalks in addition to salt (mineral) licks during the harsh dry season. Institutional and private herds are provided with legumes and grass silages and hay in addition to cereal bran, cotton seed meal and salt licks during the dry season. Nomadic herdowners now realize the importance of supplementary feeding and maintenance of good herd health in the prevention of malnutrition and diseases. This results in a consistent improvement in growth and productivity as evidenced by the lower AFC values observed in this study

A saturated map of common genetic variants associated with human height

Common single-nucleotide polymorphisms (SNPs) are predicted to collectively explain 40–50% of phenotypic variation in human height, but identifying the specific variants and associated regions requires huge sample sizes1. Here, using data from a genome-wide association study of 5.4 million individuals of diverse ancestries, we show that 12,111 independent SNPs that are significantly associated with height account for nearly all of the common SNP-based heritability. These SNPs are clustered within 7,209 non-overlapping genomic segments with a mean size of around 90 kb, covering about 21% of the genome. The density of independent associations varies across the genome and the regions of increased density are enriched for biologically relevant genes. In out-of-sample estimation and prediction, the 12,111 SNPs (or all SNPs in the HapMap 3 panel2) account for 40% (45%) of phenotypic variance in populations of European ancestry but only around 10–20% (14–24%) in populations of other ancestries. Effect sizes, associated regions and gene prioritization are similar across ancestries, indicating that reduced prediction accuracy is likely to be explained by linkage disequilibrium and differences in allele frequency within associated regions. Finally, we show that the relevant biological pathways are detectable with smaller sample sizes than are needed to implicate causal genes and variants. Overall, this study provides a comprehensive map of specific genomic regions that contain the vast majority of common height-associated variants. Although this map is saturated for populations of European ancestry, further research is needed to achieve equivalent saturation in other ancestries

A saturated map of common genetic variants associated with human height.

Common single-nucleotide polymorphisms (SNPs) are predicted to collectively explain 40-50% of phenotypic variation in human height, but identifying the specific variants and associated regions requires huge sample sizes1. Here, using data from a genome-wide association study of 5.4 million individuals of diverse ancestries, we show that 12,111 independent SNPs that are significantly associated with height account for nearly all of the common SNP-based heritability. These SNPs are clustered within 7,209 non-overlapping genomic segments with a mean size of around 90 kb, covering about 21% of the genome. The density of independent associations varies across the genome and the regions of increased density are enriched for biologically relevant genes. In out-of-sample estimation and prediction, the 12,111 SNPs (or all SNPs in the HapMap 3 panel2) account for 40% (45%) of phenotypic variance in populations of European ancestry but only around 10-20% (14-24%) in populations of other ancestries. Effect sizes, associated regions and gene prioritization are similar across ancestries, indicating that reduced prediction accuracy is likely to be explained by linkage disequilibrium and differences in allele frequency within associated regions. Finally, we show that the relevant biological pathways are detectable with smaller sample sizes than are needed to implicate causal genes and variants. Overall, this study provides a comprehensive map of specific genomic regions that contain the vast majority of common height-associated variants. Although this map is saturated for populations of European ancestry, further research is needed to achieve equivalent saturation in other ancestries