A deterministic simulation model was developed to estimate biological production efficiency and to evaluate goat crossbreeding systems under tropical conditions. The model involves 5 production systems: pure indigenous, first filial generations (F1), backcross (BC), composite breeds of F1 (CMP(F1)), and BC (CMP(BC)). The model first simulates growth, reproduction, lactation, and energy intakes of a doe and a kid on a 1-d time step at the individual level and thereafter the outputs are integrated into the herd dynamics program. The ability of the model to simulate individual performances was tested under a base situation. The simulation results represented daily BW changes, ME requirements, and milk yield and the estimates were within the range of published data. Two conventional goat production scenarios (an intensive milk production scenario and an integrated goat and oil palm production scenario) in Malaysia were examined. The simulation results of the intensive milk production scenario showed the greater production efficiency of the CMP(BC) and CMP(F1) systems and decreased production efficiency of the F1 and BC systems. The results of the integrated goat and oil palm production scenario showed that the production efficiency and stocking rate were greater for the indigenous goats than for the crossbreeding systems.
Growth performance data of the local goats of Malaysia and their crossbreds with the German (Improved) Fawn goats were analysed using animal models with maternal effects, in order to estimate additive genetic and crossbreeding parameters. Two different genetic models, the Dickerson (1969, 1973) model and the Kinghorn (1980, 1983) model, were used to estimate crossbreeding parameters. Coefficients of additive breed, heterosis (dominance), and recombination (epistatic) loss were fitted in the animal models as covariates. In general, the individual breed effects for birth, 6-month, and 9-month weights, and maternal breed effects for traits until weaning, were significant, indicating large differences for growth performance between the German Fawn and the local breeds. Heterosis effects by the Dickerson model were small and non-significant, while dominance effects by the Kinghorn model, for some of traits, were large and significant. Highly significant individual recombination loss effects by the Dickerson model, and epistatic loss effects by the Kinghorn model, were obtained for birth and 9-month weights. The estimates of total heritability by an animal model incorporating maternal effects were moderate (0.18-0.35). The differences between heritabilities, estimated by different genetic models (the Dickerson model vs. the Kinghorn model), were small. ZUSAMMENFASSUNG: Genetische Parameter von Wachstumseigenschaften Malaysischer Lokalziegen und ihrer Kreuzung mit Deutscher Rehbrauner Ziege Die Daten wurden mittels Tiermodellen mit Maternalwirkung zur Schätzung additiv genetischer und Kreuzungsparameter analysiert. Zur Schätzung letzterer wurden Modelle von Dickerson (1969, 1973) und Kinghorn (1980, 1983) angewendet. Koeffizienten der additiven Rassenwirkungen, Heterosis (Dominanz) und Rekombinations-wirkungen wurden im Tiermodell als Kovarialbe berücksichtigt. Im allgemeinen waren individuelle Rassenwirkungen für Geburts-, 6- und 9-Monatsgewicht und maternale Rassenwirkungen für Merkmale während der Säugezeit signifikant, eine Folge großer Rassenunterschiede. Das Dickerson Modell führte zu geringen, nicht signifikanten Heterosiswirkungen, während beim Kinghorn Modell diese sich für mehrere Merkmale als groß und signifikant erwiesen haben. Hoch signifikante individuelle Rekombinationsverluste und epistatische Verluste ergaben sich bei beiden Modellen für Geburtsgewicht und 9 Monatsgewicht. Heritabilitätswerte waren mäßig hoch (0.18 bis 0.35), enthielten auch die maternalen Wirkungen und unterschieden sich zwischen beiden Modellen nur geringfügig.
The first objective of this study was to investigate the relationship between concentrations of beta-hydroxybutyrate (BHBA) in milk and blood to assess the reliability of the BHBA concentrations in milk measured by a semi quantitative keto-test paper to detect subclinical ketosis (SCK) in 50 fresh high-producing Iranian Holstein cows in Golestan Province, Iran. The second objective was the effects of SCK on milk yield and components. Concentrations of nonesterified fatty acids (NEFA) and BHBA were analyzed quantitatively in blood plasma and commercial keto-test paper was used for semi quantitative determination of BHBA concentration in milk. Milk yield was measured until 60 d after calving but milk compositions were measured until 30 d after calving. The mean plasma BHBA, milk BHBA, plasma NEFA, milk yield, milk fat percentage and milk fat: protein ratio were 1,234 micromol/L, 145 micromol/L, 0.482 mEq/L, 29.5 kg, 3.9% and 1.4, respectively. Fifty eight percent of the cows had SCK during the first month of lactation. High correlation coefficients were observed between blood BHBA and blood NEFA, and between blood and milk BHBA. The milk yield of cattle with SCK decreased (P < 0.01) but the fat percentage and milk fat: protein ratio increased (P < 0.01). The commercial keto-test paper used had a low false positive result at a cut-off point of 200 fmol of BHBA/L of milk. The results showed that the best time to assess SCK using the commercial keto-test paper was d 10, 14 and 17 after calving.
The effect of parental genotype and paternal heterosis on litter size (LS), total litter birth weight (TLW) and average litter birth weight (ALW) was analysed utilizing data from a crossbreeding programme involving the exotic German Fawn goats and local Katjang goats in Malaysia. In this study, these traits were regarded as traits of the litter to consider the effect of service sire genotype. The results revealed that LS was significantly influenced by the genotype of sire. The genotypes of sire and dam had significant effects on TLW and ALW. Estimates of crossbreeding parameter showed significant and negative influence of paternal heterosis on TLW and ALW while there was no significant effect of paternal heterosis on LS. The results of this study stress the need to reconsider the use of local males in the tropics.