9 April 2013

8 minute read

Introduction

Animal welfare is an increasing concern for citizens around the world, writes the Food and Agriculture Organisation (FAO) who say that farming systems must now take animal welfare into account.

Farm animal welfare can be assessed by a number of measures including: deviations from normal behaviour typical for the species, production level based on expectations from genetic merit and diet, and health status.

The FAO acknowledge that farmers recognize the importance of addressing concerns related to animal welfare and desire solutions to animal welfare concerns that do not compromise the economic sustainability of their production system.

Numerous studies have shown the impact of animal management on welfare. For example, in order to promote weight gain during fattening, beef cattle are usually fed highenergy diets that are rich in fermentable carbohydrates but low in effective fibre. These diets increase concentrations of lactate and volatile fatty acids in the rumen which depress ruminal pH (about 5.5 to 5.0) and increase the risk of cows for disorders such as subacute ruminal acidosis, liver abscesses and laminitis.

The interaction between feeding behaviour and rumen function should be considered in addition to diet management to assess risk of ruminal acidosis and thus welfare status (Gonzalez et al., 2012). Subacute acidosis can also contribute to major economic losses for farmers due to treatment of sick animals, reduced productivity and feed efficiency, and increased feed costs.

In lactating animals, subacute acidosis can reduce milk production leading to costs estimated at US$1.12/day per cow (Stone, 1999). Nutritional strategies aimed at decreasing acidosis risk in beef-fattening operations would not only improve animal welfare but would also likely benefit the economic sustainability of these production systems.

In this case study, a high-concentrate diet is compared with two other diets characterized by a higher proportion of fibre, through their impact on the welfare of fattening bulls and overall economic profitability of the feeding system. These diets differed by expected animal weight gain, forage-to-concentrate ratio, and by the proportion of feed produced on-farm.

Welfare was assessed through indicators of behaviour (activity and feeding behaviour), of digestion (ruminal pH) and of performance (weight gain and carcass yield) of the animals. Economic profitability was calculated as economic margin per animal. Information on the environmental impacts of these three bull-fattening systems is available in Doreau et al. (2011) and Nguyen et al. (2012).

Animals and Diets

Twenty-four ‘Blond d’Aquitaine’ bulls (267 ± 22 days old and weighing 326 ± 21 kg) were assigned to six group pens of four animals (two pens per fattening diet). Each bull had access to an individual feeding place and free access to drinking water; straw was used for bedding. In the pre-experimental period, the bulls were fed a maize silage and soybean meal diet.

Over a two-week feeding transition period, the three experimental diets were introduced gradually, such that by the end of this period cattle were completely transitioned to the new diet.

The three experimental diets were composed of: 8 percent straw - 92 percent concentrate (Diet C), 44 percent hay – 56 percent concentrate (Diet H), and 58 percent maize silage - 42 percent concentrate (Diet MS) on a dry matter (DM) basis. Diets were fed ad libitum until animals reached the same average target live weight for slaughter (650 kg).

The concentrate mix was composed of ground maize grain and soybean meal. Percentages of starch and neutral detergent fibre (NDF) on a DM basis in the diets were: 44.8 and 19.1 for diet C, 28.9 and 38.4 for diet H, and 31.3 and 36.4 for diet MS. Further details on diet compositions are given in Mialon et al. (2008).

For diet C, maize was fed ad libitum and the bulls had free access to a straw rack. For the other two diets, forage was dispensed ad libitum and concentrate was adjusted to achieve the expected age-to-concentrate ratio. These diets correspond to systems representative of three regions of France (Aquitaine, Auvergne and Brittany for diets C, H and MS respectively) that differ in the nature of feeds produced locally and the normal fattening programmes for young bulls.

Indicators of Welfare

The behaviour of each bull was scanned every 10 minutes from 24-hour video recordings at several stages of the fattening period (Weeks 0, 5, 9 and 14). Individual feed offered and refusals were measured and recorded on five consecutive days per week throughout the experiment to evaluate dry matter intake (DMI).

Feeding behaviour was estimated from the electronic gate recordings taken over seven days (24 hours/day) over the same periods. The daily eating time of each bull was estimated as the mean daily time during which its feeding gate was open. A minimum interval of four minutes between feeding events was considered as the criterion for defining a new feeding meal (Mialon et al., 2008).

Economic Indicators

Only feed costs were taken into account in this analysis; it was assumed that other costs such as veterinary, rearing, farming and working costs did not depend on the diet. We also ignored the difference in time of building use due to different lengths of the fattening period. The prices of animals were €2.70/kg LW at calf purchase and €3.90/kg carcass sold.

Differences in carcass fat did not result in a difference in selling price. For feed costs (Table 1), we considered market prices for concentrate because concentrates were purchased by the farmer. For forage costs, we considered two options: forage was either bought (market price) or produced on the farm (cost price). Since there is no official price for forages, market prices were estimated by experts, except for maize silage where market price was estimated from the market price of grain maize. The cost of forage was based on the costs associated with crop production (seeds, fertilizers, pesticides, sowing and harvest).

The balance (economic margin, i.e., sale of the carcasses minus purchase of calves minus feed cost) was highest for diet MS regardless of which set of assumptions was used (Table 2). With the market price option, the balance was 14 percent and 24 percent higher than for systems C and H respectively. With the cost price option, diets C and H had an equivalent balance, which was one-third lower than the balance for MS.

Due to its high-energy value, use of the MS diet during fattening provides cattle with a readily available energy source without the need to use readily fermentable concentrates, a major risk factor for acidosis. The MS feeding programme not only results in highly productive cattle with efficient growth rates but is also economically profitable.

Although the forage component of diet H can be obtained with low input grassland, this diet still required a high amount of concentrate supplementation (814 kg/bull) and was associated with lower growth rates; therefore, this is not an optimal feeding programme. This experiment showed that for the ‘Blond d’Aquitaine’ breed, diet C is very efficient although expensive due to the high consumption of concentrates (1 021 kg/bull). Overall, the production of maize grain on farm could improve the margin for farmers.

Other Considerations

The environmental, social and societal evaluation of diets should also be taken into account. Using an extreme diet such as C reduces greenhouse gases emissions (Doreau et al., 2011) and allows farmers to maximize the growth potential of the ‘Blond d’Aquitaine’ breed, but it also leads to the ethical debate of whether cereal production should be prioritized for use in animals or humans.

Diet based on maize silage leads to a lower energy demand but an increased risk of eutrophication and acidification (Nguyen et al., 2012). A hay diet which results in limited environmental impacts allows for the enhancement of grasslands, and is adapted to regions where grass is the major home-grown feed, as in mountain areas.

In summary, feeding high-concentrate diets in order to maximize growth performance in young bulls may lead to nutritional disorders of digestive origin and result in economic losses for farmers. In this case study, three bull-fattening systems utilizing different diets based on either maize silage (MS), hay (H) or concentrates (C) were compared.

Diets differed in their forage-to-concentrate ratio (58/42, 44/56 and 8/92 for MS, H and C respectively). Diet C was associated with the highest live weight gain (1 860 g/day); however, live weight gain and feed intake were more variable with diet C than with the other diets. While on diet C, bulls modified their feeding behaviour by spreading meals throughout the day; this may be evidence of bulls engaging in a feeding strategy aimed at lowering their risk of digestive disorders associated with rapid consumption of a highly digestible feed. Diet H was associated with the lowest weight gain (1 490 g/day) but the economic margin was not different from that of diet C.

Bulls adapted better to MS diet than to diets C and H, as demonstrated by less variable intake and live weight gain and higher ruminal pH values. The economic margin of the MS feeding programme was also one-third higher than the other two feeding programmes. This suggests that good animal welfare and high economic margin are compatible, particularly when using the MS feeding programme.

Conclusion

Under the conditions of this case study, diet C resulted in the highest live weight gain thereby allowing for a shorter fattening period. This diet was also found to be more risky for overall health and welfare as demonstrated by lower ruminal pH during the first four weeks of feeding and more variable feed intake.

Although diet H does not appear to increase cattle risk of health disorders, performance might have been impaired by the low intake capacity of the breed which contributed to lower average daily gains. The economic margin for farmers is lower for diets H and C than for diet MS. Diet MS thus appears to be the most beneficial option from both an economic and animal welfare perspective.

Intake of the highly digestible MS diet increased consistently over the fattening period without cattle demonstrating behavioural or physiological indicators of digestive disorder (acidosis). These results demonstrate that animal welfare and good economic results are compatible.

Further Reading You can view the full report by clicking here.

April 2013