3 results
Characterization of growth traits of Greenland and Silver coypus under captivity conditions
- C. FAVERIN, C. A. MEZZADRA, H. M. FERNÁNDEZ, L. M. MELUCCI
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- Journal:
- The Journal of Agricultural Science / Volume 143 / Issue 2-3 / June 2005
- Published online by Cambridge University Press:
- 20 July 2005, pp. 199-207
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Brody, Gompertz, Logistic, Richards and von Bertalanffy functions were compared as descriptors of growth in 319 coypus (Myocastor coypus) of Greenland and Silver varieties, from birth to 10–19 months of age. Several criteria were considered for the selection of the model: (a) bias in the asymptotic weight; (b) bias in birth weight; (c) error sum of squares; (d) error mean squares weighted by the number of animals converging in all functions; (e) determination coefficient. To adjust the curves NLIN procedure from SAS and iterative method of Marquardt were applied. A mixed model was used to analyse the parameters of the selected growth curve (asymptotic weight, A; constant of integration, B; and maturation rate, k) which included effects of farm, variety, sex, sire within farm and variety, reproductive status within sex, birth season and first order interactions. The effect of sire was considered as random. The von Bertalanffy function was selected and mean values for the parameters of this function were 8016 g and 0·008 g/g per day, for A and k respectively. There were differences in the estimated parameters between sexes; males had larger values of A and k than females.
Weights at fixed ages (birth, weaning, 6–7 months) were analysed, as well as the final recorded weight and average postweaning gain. The model of analysis was similar to the previous one. There were no differences between varieties. Significant differences between sexes for almost all studied traits were detected. With age, weight difference between males and females increased. At 6 months of age, males were 37% heavier than females. Male average daily gain was higher than that of females, sexual dimorphism being evident in all analysed traits.
In vitro ruminal digestibility of oat hay and cellulolytic activity in the presence of increasing concentrations of short-chain acids and glycerol
- R. A. PAGGI, J. P. FAY, C. FAVERIN
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- Journal:
- The Journal of Agricultural Science / Volume 142 / Issue 1 / February 2004
- Published online by Cambridge University Press:
- 07 July 2004, pp. 89-96
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The effects of acetic, propionic, butyric and lactic acids (short-chain acids), and of glycerol, on the in vitro dry matter digestibility (IVDMD) of oat hay, and on cellulolysis by a protein extract of rumen fluid were studied. The objective was to gain information on the impact of increasing the concentrations of those compounds in the medium on degradative activities carried out by rumen microorganisms. Short-chain acids were assayed as sodium salts and, for all compounds, the concentrations were 50, 100, 200 and 300 mM. The volatile fatty acids (VFA: acetic, propionic and butyric acids) were tested separately or in two mixtures A and B that contained different proportions of each VFA. The IVDMD was assayed according to a modified Tilley & Terry (1963) technique while cellulolysis was assessed by the hydrolysis of carboxymethylcellulose (CMC) in 1-h incubations at 39 °C. Parallel incubations with NaCl were utilized as controls for ionic strength and osmolarity changes in the incubation medium. Increases of 100–300 mM of short-chain acids decreased IVDMD between 7 and 39%. The inhibitions produced by increases of 200 and 300 mM of acetic acid were smaller than those caused by the same concentrations of either butyric or lactic acids. Increases of 100, 200 and 300 mM of glycerol reduced by 8–15% the IVDMD, and the inhibitions produced by increments of 200 and 300 mM of this compound were smaller than the ones elicited by the short-chain acids, with the exception of 200 mM of acetic acid that did not differ. The IVDMD was inhibited by NaCl only when concentrations were increased by 200 (12%) and 300 mM (26%). The degradation of CMC was reduced by 7–20% by 200 and 300 mM increases of the short-chain acids or glycerol, the exception being lactic acid that had no effect. One hundred mM increases of acetic and butyric acids inhibited the CMC degradation by 7 and 9%, respectively, whereas only butyric acid was inhibitory (7%) at 50 mM. Greater concentration increases of both VFA mixtures A and B than of the individual VFA were necessary to inhibit the hydrolysis of CMC. Cellulolytic activity was decreased 6 and 9% by increases of 200 and 300 mM of NaCl, respectively, and these drops of activity were smaller than those obtained with increases in any of the other compounds. Since osmolarity and/or ionic strength changes in the medium cannot completely account for the observed inhibitions of IVDMD and cellulolysis, it is suggested that glycerol and the anions of short-chain acids produce changes in the reaction media polarity that contribute to the inhibitory effects observed. Alterations in the media could also bring about conformational changes in the degradative enzymes leading to reduced rates of reaction and subsequent decreases in IVDMD and cellulolysis. Since most of the effects were observed with concentration increases that were larger than the physiological concentrations in the rumen, it is suggested that the compounds tested have little impact in vivo on the ruminal degradative activities that were evaluated.
Slaughter traits of adult coypus grown in captivity
- C. FAVERIN, P. M. CORVA, F. A. HOZBOR
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- Journal:
- The Journal of Agricultural Science / Volume 138 / Issue 1 / February 2002
- Published online by Cambridge University Press:
- 05 February 2002, pp. 115-120
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The objective of the current study was to undertake a preliminary characterization of liveweight components in adult coypus at slaughter. Greenland (14 females, 7 males) and Silver (78 females, 36 males) breeds were grown on a farm south-east of Buenos Aires, Argentina. The animals were slaughtered aged 419±22 days. Liveweight at slaughter was measured and the weights of hot carcass, fur, head, liver, lungs plus heart, digestive tract (with contents) plus reproductive organs and fur length were recorded. The weights of these body components were also expressed as proportion of liveweight, except for the fur length. Data were analysed and the effects of sex, variety, reproductive state within sex and rearing management within sex were included in the model. The age of the animals at the time of slaughter was used as covariate. Breeds differed only in liver weight (P<0·05), where Greenland was 15·9% heavier than Silver; however when comparisons were made as proportion of liveweight, no differences between breeds were found in the variables analysed. Sexual dimorphism was evident in almost all of the characteristics analysed, values for males being higher than for females. Males were 29% heavier at slaughter than females and their carcasses 31·7% heavier. When body components were expressed as proportion of liveweight, male heads were heavier but fur was lighter compared to females. In conclusion, there were differences in body components due to sex but not due to breed. However, most body components when expressed as proportion of liveweight showed no significant differences.