Milk production of South African boer and indigenous feral goats under intensive and extensive feeding systems

[摘要] English: The primary aim of this study was to investigate the milk production potential(quantity and quality) of Indigenous feral and Boer goat does under intensiveand extensive nutritional regimes. The study was carried out at two differentlocations to accommodate the nutritional regimes. The extensive group wasmaintained at the Paradys experimental farm of the Department of AnimalScience (Faculty of Agriculture), which is situated 20 km south ofBloemfontein. Whilst the intensive group was maintained on campus, at theFaculty of Agriculture, Bloemfontein. The animals used were 36 multiparousgoat does, out of which 18 were Boer and 18 were Indigenous feral goats.Half (n = 9) of the Boer goats and half (n = 9) of the Indigenous goats wereeach randomly allocated to an extensive and intensive group.The intensively fed group received a complete diet. Each doe was given 2kg/d and daily feed intake was recorded. In the extensive group, does weremaintained on natural pastures with no feed supplementation. All does weremilked twice a week. During each milking does were subjected to two milkingperiods. The first milking was done to empty the udder, and no records ofmilk production were taken. The second milking was undertaken two hoursafter the first milking, and the milk output from each teat was recorded andmilk samples collected. The percentage milk fat, solids non-fat, lactose andprotein in the samples were determined. Blood samples were taken once aweek, to determine the serum progesterone concentrations, as an indicator ofoestrous activity. All animals (does and kids) were weighed weekly todetermine live weight changes during the post partum lactation period.Weekly teat measurements were also done.The Boer goat does produced more milk than Indigenous goats (P<0.05).The intensively fed Boer goat does produced their maximum quantity of milk(3.7 ± 1.4 I/day) during Week 4, compared to the extensive group that peaked(1.1 ± 0.7 I/day) at Week 8. Similarly, the. intensively fed Indigenous goatshad their highest milk yield (1.9 ± 70 I/day) during Week 5, compared to theextensive group (1.1 ± 7.1 I/day) at Week 11. The intensively managed doeshad a maximum milk fat yield (8.79 ± 2.58% and 8.86 ± 3.68%) in Weeks 1and 8 for Boer and Indigenous does, respectively. This maximum yield (notsignificantly different) was achieved in Weeks 1 and 5 for the same respectivebreeds in the extensive group. A correlation coefficient (r) of 0.073 betweenmilk production and milk fat content was observed. Boer goats showed atrend of producing a higher milk lactose content throughout the trial. Boergoats fed intensively yielded maximum (5.6 ± 1.6%) and minimum (3.8 ±0.7%) milk protein contents in Weeks 1 and 7, respectively, while for theextensive group these values were attained during Weeks 11 (7.2 ± 4.9%)and 6 (3.6 ± 0.5%), respectively. A correlation coefficient of 0.125 wasrecorded between milk protein content and the daily milk yield. The Boergoats in the extensive group produced the highest mean daily SNF content(10.7 ± 5.1%). The larger Boer goats had a significant (P<0.05) higher feedintake. The correlation coefficient between feed intake and milk productionwas 0.7 for the Boer goat and r = 0.4 for the Indigenous goat. The meanbody weight was 45.0 ± 8.7 kg vs 32.3 ± 6.1 kg for Boer and Indigenous goatsunder the intensive feeding regime, and 42.3 ± 8.0 kg vs 29.3 ± 4.5 kg forthose under an extensive feeding regime. Considerable variation in teatlengths was recorded. Peak serum progesterone concentration wasrecorded during Week 7 for the Boer goats (intensive group) and Week 12 forthe Indigenous goats (intensive group). Ovarian activity (progesterone levels)remained low in the extensive groups throughout the observation period. Milkyield was significantly related to the nutritional status and the breed of thegoat. The Boer goat produced more milk than the Indigenous goat. It is,thus, suggested that it can be used for milk production in the rural areas ofSouth Africa. This may improve the nutrient intake of the rural communities.

[发布机构] University of the Free State