23 May 2019
As a part of the same supplementation program the University of Queensland is running, a comprehensive literature review as been undertaken and what follows are the ‘golden nuggets’ dug up.
For obvious reasons there has been a lot less research conducted on goats vs sheep and cattle. Consequently, a lot of the scientific information that is necessary to support a well organized and developing goat meat industry in Australia has been fragmented, non-existent or difficult to access despite some great work being performed over the years.
Apart from establishing and confirming the formula for estimation of maintenance requirements for both metabolisable energy and protein of Australian goats, Associate Professor Barry Norton’s review shed light on other aspects of goat production that all producers need to be aware of. They include:
- Photoperiod, particularly day-length decline between the autumn equinox (greatest rate of decline) and winter solstice (shortest day), has a significant impact on the growth of young growing weaners and mature males in rut. The principle effect was a decrease in voluntary feed consumption which was significantly correlated with decreasing live weight changes (Walkden-Brown 1994b) especially from April to June. This ‘photoperiod effect’ appears to decrease an animal’s appetite without affecting the animal’s basic maintenance requirement for energy. This phenomenon requires consideration when planning supplementary or lot feeding of goats in the autumn period. It also has implications when determining optimum joining time for does to achieve maximum conception rates in breeding operations.
- Fibre is important. Goats are able to digest high fibre (low protein/quality) better than sheep, and the fraction that is better digested is the cellulose/lignin component. This allows goats to be more suited to browse and lower quality pastures than sheep. However, the fibre content of a ration is important when lot feeding goats or sheep on cereal-based rations as fibre ensures chewing and production of saliva and it is this saliva containing bicarbonate ions that helps reduce the risk of developing acidosis and digestive disturbances. A ration analysis report often provides information on the ADF content (acid detergent fibre is a measure of the amount of highly indigestible or slowly digestible fibre in the ration). The review indicated that a minimum content of ADF of around 200 g/kg DM will maintain effective rumen function. However, dilution of concentrate feeds with forages decreases the energy density of the ration and so the challenge is always to get the balance right – maximum energy intake at least cost while avoiding acidosis.
- Heavier does produce more milk than lighter does, and while does with twins do produce more milk than does with singles, there is not usually enough milk to satisfy the needs of both twins. This suggests that the poor growth rates of twin and triplets is mostly the result of limited milk availability. Dr Norton found no difference in the growth rates of male and female twins and singles offered artificial milk ad lib. This means that when multiple births occur, the kids will grow equally as well as singles if additional feed is provided.
- The full range of causal factors of kid loss in rangeland goats have yet to be identified but research has shown that supplementing domesticated rangeland pregnant does with 360g supplement (50% kibbled sorghum, 50% cotton seed meal) for just two weeks before kidding (early September) significantly can reduce the immediate (16 days after kidding) post-natal mortality of kids from 18% to 3 % of kids born. Dr Norton said that in the management system that he researched kidding occurred over six weeks Optimising the growth of young goats to market weight requires attention to all levels of management from maximizing doe milk production for kid growth to weaning, providing strategies to minimise weight losses after weaning and post weaning supplementary feeding to maximise growth rates to slaughter weight. Understanding the critical times of feed inputs is the first step but the challenge is always to determine if the cost benefits are positive.
- Very little evidence was found of rangeland goat growth rates exceeding 200g/day irrespective of age, gender, liveweight or feeding regime. Ass. Prof. Norton said these findings should put into perspective the potential for weight gains, and even for modest growth rates of 150g/day (1kg/week) need to be managed accordingly. For instance, it would take at least six months for a weaner goat to reach marketable weight (35kg).
It has been clearly shown that males consume more and grow faster than females when offered unrestricted intakes, and that increasing concentrations of protein in the ration promotes better intake and weight gains of both sexes offered both diets. While Dr Norton agrees that crossbreeds might provide better gains in most environments, he said the costs and problems of introducing such breeds into poor quality rangelands (where even the genetic potential of the local goats is not being achieved) needs to be approached cautiously and meticulously.