Pasture-based Dairy Production Systems Research Articles

Developing breeding schemes for pasture based dairy production systems in Kenya: I. Derivation of economic values using profit functions

Economic values for milk production (milk yield, MY and fat yield, FY), reproductive (age at first calving, AFC and calving interval, CI), growth (preweaning daily gain, DG; postweaning daily gain, PDG; and mature live weight, LW), survival (preweaning survival rate, SR and postweaning survival rate, PSR) and longevity (productive lifetime, PLT) traits were calculated for a pasture based dairy production system in Kenya. Parameters in the profit functions reflected the production circumstances of pasture based dairy production systems, but can be modified to fit other production situations. Two evaluation bases were considered; fixed herd-size and fixed pasture-input. Within each of these evaluation bases, economic values were estimated under two situations of payment of milk; based on milk volume (VOLUME) and on volume and fat content (FAT). With a fixed herd-size and under VOLUME, economic values were KSh 18.93 (MY, kg), −2.76 (FY, kg), −2.72 (AFC, days), 2.65 (CI, days), 1.04 (DG, g/day), 3.40 (PDG, g/day), 7.95 (LW, kg), 9.96 (SR, %), 45.15 (PSR, %) and 0.07 (PLT, days). Under FAT, changes in the economic values were only observed for MY (KSh 16.05 per kg) and FY (KSh 79.44 per kg). With a fixed pasture-input, there was a significant reduction in the economic values for MY, FY and LW under both payment systems. Under VOLUME, economic values for MY, FY and LW were KSh 15.29, −140.46 and −43.15 per kg, respectively. The respective values were KSh 12.25, −62.76 and −45.03 per kg under FAT. Sensitivity analysis indicated that economic values for MY and FY increased significantly with higher prices of milk volume and fat content, respectively. With higher feed prices, the economic values for the fertility traits and longevity increased but decreased for milk production traits, survival traits and LW. This study suggests that genetic improvement of milk production, growth, fertility, survival and longevity traits will have a positive effect on profitability of pasture based dairy production systems in Kenya, especially when the availability of pasture is not limited.

Developing breeding schemes for pasture based dairy production systems in Kenya: II. Evaluation of alternative objectives and schemes using a two-tier open nucleus and young bull system

A deterministic approach was used to evaluate alternative breeding objectives and schemes in a dairy cattle breed in Kenya. A two-tier open nucleus breeding scheme and a young bull system (YBS) were assumed with intensive recording and 100% artificial insemination (AI) in the nucleus and 35% AI in the commercial sector. The breeding objectives differed in the marketing scenario that each described and whether pasture feed for the cows was limited or not. Two marketing scenarios were distinguished; current (payment of milk is based on volume) and future (payment of milk would be based on volume and fat content). Therefore, four breeding objectives were considered: current no limitation (CUNL), current with limitation (CUWL), future no limitation (FUNL) and future with limitation (FUWL). The breeding schemes differed in the records available for use as selection criteria. The schemes ranged from one that only utilised fertility criteria (scheme 1) to one that incorporated fertility, weights, milk and fat yield (FY) criteria (scheme 5). The annual monetary genetic gain and profit per cow for all schemes varied within breeding objectives but were highest in CUNL. Within each marketing scenario, the annual monetary genetic gain and profit per cow was higher in a no limitation situation than in a situation with limitation on pastures. Within each breeding objective, the annual monetary genetic gain and profit per cow was highest for the breeding scheme with the highest level of investments. In all objectives, the difference in the profit per cow between a scheme that incorporated fertility, weights and milk yield (MY) criteria (scheme 4) and scheme 5 was small (0.4–1.2%) indicating that there is little benefit including FY as a selection criterion. Therefore, a breeding scheme that requires records on FY seems not to be reasonable from an economic point of view. This study showed that a well-organised breeding programme utilising an open nucleus, YBS and the smallholder farms as the commercial sector could sustain itself. The practical implications of the results and how sustainable breeding programmes can be established are discussed.

Breeding objectives for pasture based dairy production systems

The aim of the study was to derive economic weights for milk production traits (milk, fat, and protein yield), survival, and mature body size for pasture based production systems. Economic weights were derived using a herd model and differentiating a profit function with respect to the traits of interest. Scaling was taken into account by assuming that the total feed supply per farm was constant and at an economically optimum level. Relative economic weights were expressed in genetic standard deviations. To investigate the robustness of the method to derive economic weights, economic weights were calculated for 11 different sets of herd parameters, varying production levels, average herd life, costs and returns. Protein yield had the highest relative economic weight, followed by survival and mature body size. The latter traits were approximately half as important as protein yield, with the economic weight for body size negative. Fat and milk yield were approximately equally important and 40% as important as protein yield. Milk (volume) yield had a negative economic weight. Economic weights were fairly robust to changes in herd parameters, and it was concluded that the method of calculating economic weights, using a herd model and constraining the total energy supply, was appropriate for pasture based production systems.