No abstract

Milk yield traits and lactation length of two breeds of cattle raised on natural pasture with little or no supplementation were assessed. A total of 42 573 daily milk records on 98 Friesian-Sanga cows collected over a period of 10 years and 17 790 daily milk records on 72 Sanga cows spanning a 6-year period were used in the study. Traits examined for each breed were daily milk yield, total milk yield, 305-day milk yield, 305-day milk yield/day and lactation length. Friesian-Sanga cows outperformed their Sanga counterparts in all traits studied. Friesian-Sanga cows had an average daily milk yield of 1.35 +/- 0.00 kg; average total milk yield of 266 +/- 12 kg; average 305-day milk yield of 339 +/- 10 kg; average 305-day milk yield/ day of 1.11 +/- 0.03 kg and mean lactation length of 201.1 +/- 6.9 days. Average values for Sanga cows were 1.01 +/- 0.00 kg as daily milk yield; 162 +/- 12 kg as total milk yield; 244 +/- 10 kg as 305-day milk yield; 0.80 +/- 0.03 kg as 305-day milk yield/day. Mean lactation length for Sanga cows was 164.1 +/- 9.4 days. Season of calving significantly (P < 0.05) influenced daily milk yield of Friesian-Sanga cows and all traits of Sanga cows with animals calving in the major rainy season surpassing those that calved in the minor and dry seasons. Daily milk yield for both Friesian-Sanga and Sanga cows was significantly (P < 0.05) influenced by season of lactation. Daily milk yield gradually declined from second parity towards the sixth parity for Friesian-Sanga cows. A gradual increase in daily milk yield from first to third parity was observed in Sanga cows. Year of calving significantly influenced all traits for both breeds. Genetic improvement in milk yield traits and lactation length is achievable for both breeds of cattle as co-efficient of variation of traits were moderate to high.

Data collected from 1993 to 2006 at the Animal Research Institute of Ghana was used to compare the performance of Sanga and Friesian-Sanga crossbred calves on natural pasture. Performance traits analyzed were birth weight (BWT), weaning weight adjusted to 210 days (WW7), preweaning average daily gain to 210 days (ADG 1), weight at 12 months adjusted to 365 days (W12), weight at 18 months adjusted to 540 days (W18) and postweaning average daily gain (ADG 2, from weaning to 540 days). Effects in the model describing these traits were breed, season, sex and first-order interactions between these effects. With the exception of heavier birth weight of Friesian-Sanga crossbred calves (19.98 kg vs. 19.18 kg), body weights of Sangas at weaning, 12 months and 18 months exceeded those of the Friesian-Sanga crossbred calves by 3.76 kg, 35.06 kg and 46.24 kg respectively. The Sangas were also superior in preweaning average daily gain (0.35 kg/day vs. 0.26 kg/day) and postweaning average daily gain (0.28 kg/day vs. 0.21 kg/day). There was a tendency of increasing weight difference between the two breeds with advancing age. It was suggested that improved nutrition such as supplementary feeding would be necessary for crossbreds to express their potential for growth.

The typical cattle production system in Ghana is predominantly pasture-based. Cattle are grazed all year round on natural pastures with minimal feed supplementation. The animals kept in this production system often experience inadequate nutrition and fluctuating nutrient supply affecting their productivity. There is presently limited information on the growth and reproductive performance of the Friesian x Sanga crossbred cattle (Plate 1) and factors influencing these performance traits. The growth and reproductive performance records of 150 Friesian x Sanga crossbred cattle, kept at the Animal Research Institute station in the Accra Plains of Ghana from April 1993 to October 2009 were evaluated to determine the effect of parity of cow, season of calving and sex of calf on birth weight, weaning weight, growth rate, age at first calving and calving interval. The birth weight and weaning weights of the calves averaged 21.8 ± 0.5 kg and 94.2 ± 3.8 kg, respectively, and were not (P > 0.05) affected by sex of calf, parity of cow or season of calving. Parity of cow affected (P < 0.05) weight of calf at 12 months. Calf weight at 12 and 18 months averaged 128.0 ± 3.4 kg and 159.9 ± 4.5 kg, respectively. Pre-weaning and post-weaning average daily gains were 0.33 ± 0.02 kg/day and 0.23 ± 0.03 kg/day, respectively, and were not significantly (P > 0.05) affected by sex of calf, parity of cow or season of calving. The mean age at first calving was 41.2 ± 1.2 months. Calving interval was prolonged averaging 441.6 ± 10.3 days and was significantly (P < 0.05) affected by parity of cow. Calving interval decreased with increasing parity of cow. The age at first calving and calving interval were not (P > 0.05) affected by either sex of calf or season of calving. The growth and reproductive performance of the Friesian x Sanga crossbred cattle was less than optimum. Improving their nutrition could impact, positively, on their productivity through fast growth, increased milk yield and early resumption of ovarian cycles after calving. Thus, results from this study should guide the development of appropriate strategies for increased meat and milk production in Friesian x Sanga crossbred cattle.

No abstract