The effect of ecotype and season on the production and reproductive performance of Nguni cattle in Limpopo province of South Africa

Abstract

Nguni cattle have been a source of interest for several decades for researchers, breeders and farmers alike. The production efficiency potential, reproduction potential and adaptation of Nguni cattle are some of the most desired traits of the breed. The Nguni cattle breed has several ecotypes that are similar in other respects, and different in other characteristics. The production and reproduction characteristics among the three Nguni cattle breed ecotypes raised at Mara Research Station in Limpopo Province were investigated in this study. Data of these three Nguni cattle ecotypes (Pedi, Venda and Shangaan) calf births collected from 2009 to 2013 were used in the study. Data contained records of cow identities, monthly cow weights, shoulder heights, calf birth dates, calf birth weights, weaning weights and yearling weights. Data were used to derive the following parameters: inter calving period, weight of cow at breeding, weight of cow at weaning, days to reconceive and weaning efficiency. Data were edited to remove all calves that were born out of season and cattle that died within the first year of study. Only cows that were present in all the breeding seasons during the period of this study were included in the data set. The final data set amounted to 644 calf births with 264, 142 and 65 representing Pedi, Venda and Shangaan ecotypes respectively. Mixed models procedure of SAS was used to analyse for variance in production and reproduction parameters due to ecotype and season. Least square means were separated using PDIFF function for mixed models procedure and the Bonferroni multiple range test was used to compensate for the unbalanced nature of the data set. GPLOT procedure of SAS was used to generate a schematic representation of the distribution of reconception data for cows of each Nguni ecotype. The relationship between live weight and body measurements was explored using Procedure of Correlation and GPLOT procedure in SAS. A scatter plot for body measurements for all ecotypes was also done using GPLOT procedure of SAS to demonstrate the size distribution of the three ecotypes. No differences (p>0.05) were observed with regards to cow size variation among the three Nguni ecotypes. The Pedi ecotype had a higher (p<0.05) birth weight at 25.46 (0.26)kg and a higher (p<0.05) weaning weight at 156.87 (1.84)kg, the Venda ecotype had a lower (p<0.05) birth weight at 24.08 (0.38)kg and a higher (p<0.05) weaning weight at 144.04 (2.78)kg and the Shangaan ecotype had a higher (p<0.05) birth weight at 25.01 (0.70)kg and a lower (p<0.05) weaning weight at 136.36 (4.56)kg. Season 2012 had the highest (p<0.05) birth weight and weaning weight at 27.67 (0.47)kg and 159.78 (3.23)kg respectively. Season 2010 and 2011 experienced the lowest precipitation, however Shangaan ecotype in subsequent seasons 2011 and 2012 respectively, had the highest (p<0.05) birth weight at 26.93 (0.84)kg and 27.05 (1.11)kg respectively, of the three ecotypes. This high performance of the Shangaan ecotype was expected because a smaller framed animal allows for efficient utilization of energy during periods of scarce feed. The Pedi and Shangaan ecotypes had higher (p<0.05) weaning efficiency) at 0.407 (0.01) and 0.439 (0.01) respectively, and differed significantly (p<0.05) with the Venda ecotype which had a lower (p<0.05) weaning efficiency at 0.381 (0.01). The Pedi and Venda ecotypes had the highest (p<0.05) weights at breeding at 355.50 (3.55)kg and 349.68 (4.47)kg respectively which differed (p<0.05) from Shangaan ecotype at 328.28 (7.09)kg. Pedi and Venda ecotypes also had the highest (p<0.05) weights at weaning across all the years included in the model at 385.44 (7.38)kg and 377.79 (4.89)kg respectively; and were not statistically different (p>0.05) from each other but they were both statistically different (p<0.05) from the Shangaan ecotype at 341.35 (8.06)kg, which is generally smaller. No differences (p>0.05) were observed among the three ecotypes with regards to inter calving period and days to reconception. There were no differences (p>0.05) between seasons 2009, 2010 and 2013 for weaning efficiency but all these seasons differed (p<0.05) significantly from both seasons 2011 and 2012 at 0.33 (0.01) and 0.47 (0.01) respectively. The lowest (p<0.05) weaning efficiency 0.33 (0.01) and highest (p<0.05) inter calving period 545.08 (26.30) days were observed in season 2011; and the highest (p<0.05) weaning efficiency was observed in season 2012 at 0.47 (0.01). A reduction in cow weight at weaning and cow weight at breeding was observed in season 2012. The observed lack of statistical differences (p>0.05) between the Pedi, Shangaan and Venda ecotypes in terms of reproduction is important for Nguni cattle farmers, because either of the ecotypes would fare well in beef production systems in subtropical regions. The implication is that no differences are required in the management of these ecotypes for optimal production; thus farmers can choose either of the ecotypes, and if well managed they should be able to produce a calf each year. The lack of meaningful differences between the ecotypes indicates that there is no need to manage the Nguni ecotypes differently at Mara Research Station in Limpopo Province.