The use of a Latin square change-over design with dairy cows to detect differences in the quality of tropical pastures
ABSTRACT The value was investigated of a latin square change-over design for detecting differences in herbage quality in terms of milk production and milk composition from Jersey cows grazing pure stands of three tropical grass pastures, Digitaria decumbens, Setaria sphacelata cv. Kazungula, and Chloris gayana CV. Pioneer. Relatively small differences in milk production could be measured using limited resources of land and cows, and estimates were calculated of the number of cows required to detect true differences in milk yield. A 9-day standardization period was shown to be more desirable than a 4-day standardization period. Residual effects of previous treatments, although small, were significant. Suggestions are made for improving the efficiency of change over experiments using cyclic designs to estimate residual effects. The overall level of milk production from these pastures was low (8-10 kg/cow/day). Cows grazing Digitaria decumbens produced significantly more milk than those on Chloris gayana and Setaria sphacelata, most probably due to a higher consumption of herbage. Similar milk production was obtained from cows grazing Chloris gayana and Setaria sphacelata although milk from the latter tended to contain a lower percentage butterfat.
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ABSTRACT: The net energy values for growth and fattening of two artificially dried tropical grasses-, pangola (Digitaria decumbens) and setaria (S. sphacelata var. sericea cv. Nandi), of similar estimated metabolizable energy content (8·07 and 7·96 MJ/kg D.M.) were determined with cattle using a slaughter technique. Growing cattle with a mean initial weight of 175 kg were given equal quantities of dry matter of the two grasses at each of three planes of nutrition above maintenance for a period of 152 days.The initial energy, fat and protein content of the total body of the 24 test animals was estimated from regressions relating fasted live weight to theśe components, derived from 12 similar cattle slaughtered at the beginning of the feeding period. The final energy, fat and protein content of the test animals was determined directly by chemical analysis. The metabolizable energy (ME) content of the grasses was estimated from the level of digestible energy (DE) determined with eight cattle, assuming that ME = 0·815 DE.The cattle fed pangola gained more live weight, empty-body weight, fat, protein and energy than animals fed similar quantities of setaria. The net energy value for growth and fattening (NEf) was determined using regressions relating energy retention to the quantity of dry matter eaten. NEf in MJ/kg dry matter was 2·27 for pangola and 1·31 for setaria.Efficiency of utilization of ME for growth and fattening (kf) was.27·7% for pangola and 16·9% for setaria. These values for tropical grasses are lower than any values reported for temperate pasture species. Thus the lower efficiency of utilization of ME may cause the lower production of cattle which graze tropical grasses.It was concluded that as the kf values of different tropical grasses are not constant, kf values should be measured on a wider range of tropical grasses so that this factor can be taken into account when evaluating grasses in animal production systems.The Journal of Agricultural Science 03/1982; 98(02):395 - 404. DOI:10.1017/S0021859600041940 · 2.89 Impact Factor
- J Dairy Res 03/1984; 51(1):149-96. DOI:10.1017/S0022029900023414 · 1.39 Impact Factor
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ABSTRACT: An elite genotype of Digitaria milanjiana, which had been selected on the basis of improved leaf digestibility, was compared with pangola grass (Digitaria eriantha ssp. pentzii, formerly Digitaria decumbens) in terms of milk production, at Mutdapilly in south-eastern Queensland. Unsupplemented Holstein-Friesian cows grazed nitrogen-fertilised, irrigated swards of 2 grasses using a switch-back experimental design. Pasture management and stocking rate were adjusted to provide the animals with 15 kg of green leaf (on a dry matter basis) per cow per day, so that any differences in milk yield could be attributed to differences in leaf quality rather than to total dry matter yield. Cows grazing the selected genotype produced 0.9 kg more milk, 0.07 kg more butterfat and 0.05 kg more protein per cow per day (5.8, 13.0 and 10.9%, respectively) than those grazing pangola grass. These increases were associated with a small increase in leaf digestibility, a faster rate of breakdown of leaf (in an artificial masticator) and a higher proportion of leaf in the diet chosen by the cows grazing the selected genotype. The results of this experiment demonstrate that a tropical grass selected on the basis of digestibility increased milk production of grazing cows. However, factors other than higher digestibility (such as leafiness) contributed to the improvement in production over that from pangola grass.Australian Journal of Experimental Agriculture 01/1991; 31(5). DOI:10.1071/EA9910603 · 1.62 Impact Factor