Index selection of beef cattle for growth and milk production using computer simulation modelling

The Texas A&M University (TAMU) Beef Cattle Production model was expanded to include basic concepts of quantitative genetics. The traits simulated were birth weight, yearling weight, mature weight and milk production. The progeny inherited attributes from both the sire and the dam. The incorporation of genetic concepts into the model allowed for the introduction of variation between individuals and generations. This was achieved by interfacing the original model with stochastic genetic subroutines including a restricted selection index for desired genetic change. The index included birth weight and yearling weight. In addition, a function for estimating dystocia was also added. The model was used to simulate selection strategies for a small-to-moderate size breed of cattle and a large-size breed using a restricted selection index. There was an increase in both birth and yearling weight after 20 years of selection in the small-to-moderate size breed, and there was also an increase in dystocia. Antagonistic selection to decrease birth weight and increase yearling weight was simulated for the large breed. Birth weight and dystocia problems declined while yearling weight increased for all classes of animals. In both experiments correlated responses were recorded for mature size and milk production. It was concluded that the modified TAMU Beef Cattle Production model offers breeders an opportunity to compare different selection strategies and evaluate different breeding plans. (South African Journal of Animal Science, 2001, 31(2): 65-76

The Texas A&M Sheep and Goat Simulation Models

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SE 03. Financial projections for the evaluation of technological alternatives in the Mexican dual purpose production system

The overall objective of this work was to perform an economic analysis of technological alternatives for the dual purpose production systems under Mexico’s tropical conditions. This production unit was based on grazing 100 ha of improved species of grass and supplemented with Napier grass and corn silage during the dry season. Two alternative scenarios were analyzed: 1) the use of BST and 2) the purchase of a milk cooling tank. A farm level, income and policy simulation model (FLIPSIM), developed at Texas A&M University was used to analyze the production and financial conditions of the production unit over a six year planning horizon (1995-2000). The results indicate that to pay for the use of BST, on average, the milking herd should increase milk production by 21.38 % for the first year in the planning horizon. As inflation decreases and financial conditions improve over time, smaller increments in milk production would be necessary to pay for the hormone. The initial investment necessary for the purchase and associated facilities for a milk cooling tank and operation costs associated to cooling the milk required the net income to increase to US$12,500 over the baseline during the first year for the farm to break-even. The more dramatic effect is realized in the first year because of the 20$ 4,000 to US$5,700 over the rest of the planning horizon. The effect of this on the unitary BE milk price is a difference of US$ 0.046 /liter of milk in the first year and a range of US$ 0.015 - 0.0213 /liter of milk over the rest of the planning horizon

Breeding strategies for genetic improvement

The SR-CRSP staff at the Ol Magogo Estate is developing a synthetic breed of dual-purpose goat to meet the requirements of small-scale farm families. The objective was to build a goat that has acceptable milk yield, growth rate, fertility, adaptation, and rate of survival under western Kenya conditions. The synthetic dual purpose does were capable of producing 1.1 kg per milking in the day. The toggenbury and Anglo Nubian crossing with that of Galla and East African goats continued in the synthesis of the Dual purpose Goat

Genetic resistance to gastrointestinal nematodes, with special reference to Haemonchus contortus, in three breeds of goats in Kenya

An experiment was carried out to compare the susceptibility to haemonchosis of three breeds of goats and to seek indications of genetic resistance. Twelve East African, nine Galla and 13 East African X Toggenburg crosses were artificially infected with 500 Haemonchus contortus larvae per kg live weight. Liveweights, haematocrit and worm eggs were measured twice a week for 13 weeks. Clinical signs were recorded; postmortem and worm counts were done for animals which died. Mortality was lowest for East African (25%), intermediate for East African X Toggenburg. (46%) and highest for Galla (67%). Statistically, however, there were no signifIcant differences amongst the breeds in mortality rates, liveweights, haematocrit and egg counts. It was inferred that due to lack of challenge resulting from their selective (browsing) habits, goats have not been subjected to natural genetic selection for resistance to haemonchosis. The results of the present study and various studies relating to the selective feeding habits of goats are discussed