Cow Efficiency, Relative-Birth Weight and Subsequent Pre-Weaning Growth Performance of Nguni Cattle

The objective of this study was to evaluate factors influencing Cow Efficiency (CE), Relative-Birth Weight (R-BW), and subsequent pre-weaning growth performance of Nguni cattle in Limpopo Province, South Africa. Factors that were considered were dammed weight at calving, agro-ecological zone, the season of birth, sex of calves, parity, and dam age. Data from Nguni cows and their calves (n = 826) consisting of calf Birth Weight (BW), Weaning Weight (WW), and Dam Weight at calving were used in this study. Dams were classified according to their weights at calving into high (>385 kg), medium (326-385 kg), and low (<326 kg) categories. The General Linear Model (GLM) procedure of SAS (2015) was computed to analyze data; the means were separated using Fisher's Least Significant Difference (LSD) test. Dam weight at calving influenced CE, R-BW, WW, and P-ADG, but did not influence BW. Lighter and average dams had higher CE (36.74; 35.04 Vs 30.01%), R-BW (8.04; 7.12 Vs 6.28%), WW (116.80; 116.62 Vs 115.13 kg), P-ADG (0.447; 0.446 Vs 0.438 kg/day) and P-WG (91.72; 91.40 Vs 89.77 kg) compared to heavier dams. Animals in the humid zone had higher CE (35.32%), WW (117.53 kg), P-ADG (0.452 kg/day), and P-WG (92.86 kg). Animals in arid yielded lower CE, WW, P-ADG, and P-WG compared to those in humid zone. Season of birth influenced R-BW and pre-weaning performance traits, however, it did not influence CE. Higher WW (116.78 kg), P-ADG (0.448 kg/day), P-WG (91.96 kg) were recorded for summer calves. The sex of calves, parity, and damage influenced all traits except R-BW and BW. Dams with male calves had higher CE (34.79%), WW (126.20 kg), P-ADG (0.491 kg/day), and P-WG (100.71 kg) compared to their female counterparts. Dams on the fifth (5th) parity had higher CE (37.00%), R-BW (7.18%), WW (127.01 kg), P-ADG (0.495 kg/day) and P-WG (101.53 kg). Seven (7) years old dams had higher CE (42.32%), WW (143.33 kg), P-ADG (0.590 kg/day), and P-WG (121.17 kg). The findings indicate that breeding with lighter cows would result in calves with comparable or even better growth traits than heavier cows.