| dc.description.abstract | Meat production in Uganda relies grossly on the local animal genotypes raised under extensive production systems. The productivity of the animals varies widely with changes in pasture quantity and quality in different seasons. In an effort to improve productivity, two studies were conducted to evaluate genotype and feeding system effects on the performance of the indigenous animals (i.e. Ankole cattle and Mubende goats) and their respective crossbreds. Study I evaluated effects of feeding system on performance of Ankole cattle and its crossbreds with Boran and Friesian, while study II evaluated growth and slaughter characteristics of grazing Mubende and Mubende x Boer goats supplemented with concentrates.
In study I, one hundred forty four bulls comprising 48 purebred Ankole (ANK), 48 Ankole-
Boran (AXB) crossbreds and 48 Ankole-Friesian (AXF) crossbreds were each assigned to three feeding systems (FS). The bulls, average 18 months in age had initial weights of 182.3 ± 27, 205.9 ± 26 and 188 ± 22 kg for ANK, AXB and AXF, respectively. Bulls were stratified by weight and randomly allocated within strata to a 3 X 3 factorial treatment structure. Feeding systems comprised: T1 (Grazing alone), T2 (Grazing + overnight concentrate supplementation) and T3 (feedlot finishing with ad libitum maize stover and concentrate which accounted for 60% of daily estimated feed intake). After 120 days of feeding, 8 out of 16 bulls per treatment were selected by weight for slaughter. Data collected was analysed using the general linear model procedures of SAS, 2003. Genotype and feeding system affected (P<0.05) DM intake, growth and slaughter characteristics. Feed efficiency was 6.5, 7.1 and 7.3 for AXF, ANK and AXB, respectively, at the feedlot. Among blood metabolites measured, plasma glucose (P<0.01) and lactate (P<0.01) were affected by genotype while feeding system affected glucose (P<0.05), lactate (P<0.05), albumin (P<0.01) and BUN (P<0.01). Highest glucose level (i.e., 7.5 mmol/L) was observed in grazing AXB, although glucose levels generally ranged between 5.1 and 5.9 mmol/L. Lactate levels ranged between 9.6 and 13.8 mmol/L, the levels were higher in T1 than T2 which was also higher than T3 in all genotypes. Blood urea nitrogen (BUN) was higher in T3 than T2 and T1, in that order except in AXF where lowest BUN was observed in T2. Data on rumen fermentation characteristics showed that rumen pH (P<0.05), propionate (P<0.001), isobutyrate (P<0.01), isovalerate and valerate (P<0.01) varied between genotypes. Feeding system affected rumen pH (P<0.05), acetate (P<0.01), propionate (P<0.001) and acetate:propionate ratio (P<0.01). Growth rates were affected by both genotype (P<0.01) and feeding system (P<0.001). Average daily gains were; 0.93, 0.80 and 0.75 kg live weight gain per day for AXF, ANK and AXB, respectively, at the feedlot. Feedlot finishing (T3) also resulted in heavier carcass and non-carcass components than T2 and T1. Hot carcass weights were; 134.4, 134.7 and 138.1 kg for ANK, AXB and AXF, respectively, at the feedlot. Hot carcass dressing percentages were; 52.3, 51.8 and 51.8 % at the feedlot and 50.0, 53.1 and 50.1 % in supplementation of grazing (T2) for ANK, AXB and AXF, respectively.
In study II, 96 castrate goats (48 pure Mubende (MDE) and 48 Mubende-Boer crossbreds
(MXB)) were randomly allocated to three dietary treatments in a 2x3 factorial treatment structure. The dietary treatments were: GZ (solely grazing as control), MCC (grazing animals supplemented with concentrate without molasses) and MCM (grazing animals supplemented with concentrate containing molasses). Ten out of the 16 goats per treatment were randomly selected and slaughtered after 90 days of feeding. Concentrate DM intake and feed efficiency varied between genotype (P<0.001) and dietary treatment (P<0.001). Concentrate dry matter (DM) intake was higher in crossbreds in MCC diet. Intake was 1.4 kg DM/animal/day and 1.6 kg DM/animal/day for pure Mubende and the crossbreds, respectively. Efficiency of MCC concentrate utilisation was 27.6 and 19.9 for MDE and MXB, respectively. Feed efficiency of MCM was 22.5 and 25.7 for MDE and MXB, respectively. Cost of supplementation per animal per day was higher in the crossbreds than the pure Mubende. There were no genotype and dietary treatment effects on most blood metabolites measured except albumin (P<0.001) and BUN (P<0.001). Genotype affected hot carcass weight (P<0.001) but did not affect dressing percentage. However, dietary treatment affected both hot carcass weight (P<0.001) and hot carcass dressing percentage (P<0.001). Carcass weights were higher in MXB (GZ=19.2, MCC=23.0 and MCM=21.7 kg) than in MDE (GZ=17.4, MCC=20.9 and MCM=20.8 kg). Dietary treatment affected (P<0.05) all non-carcass components except head, skin plus feet and
tail, heart, kidney, empty intestines and empty stomach.
These results provide evidence that under improved feeding management, the growth rate and meat yielding potential of the Ankole cattle are comparable to their Boran and Friesian crossbreds. Further evidence also suggests that feedlot finishing offers a better opportunity to increased growth rates and meat yield compared to supplementation of grazing. A higher meat yielding potential of the Mubende goat and its Boer crossbred under improved finishing was also demonstrated. | en_US |
