The objective of this study was to investigate the effects of chitosan (CHI) on ruminal and cecal fermentation and on apparent digestibility in sheep. In a first trial, 4 ruminally fistulated sheep fed an alfalfa hay and concentrate diet formulated to meet 1.2 times their maintenance energy requirements were assigned to 2 treatments [no-additive control (CTR), or 136 mg/kg of BW of CHI] for 19 d in a 2 x 2 crossover design. Samples of ruminal fluid and feces were taken for VFA and NH(3)-N concentrations. At the end of each period of the crossover, ruminal fluid was used as inoculum for batch cultures (24 and 96 h), and the effects on rate and extent of gas production and on fermentation variables for starch, cellulose, and the same diet fed to the animals were calculated. In a second trial, 4 sheep fed the alfalfa hay and concentrate diet were assigned to 2 treatments (CTR and CHI), as for the first trial, but this time for 14 d in a 2 x 2 crossover design. Apparent digestibility was studied. In the first trial, in terms of ruminal fermentation, CHI did not affect (P = 0.12) total VFA concentration or acetate proportion, but increased propionate proportion (P = 0.004) and propionate-to-acetate ratio (C3:C2; P = 0.007) and decreased branched-chain VFA (BCVFA) proportion (P = 0.003) and NH(3)-N concentration (P = 0.045). In feces, CHI decreased total VFA concentration (P = 0.01) and acetate (P = 0.045) and butyrate (P = 0.025) proportions, and increased propionate (P = 0.04), valerate (P = 0.01), and BCVFA (P = 0.032) proportions and C3:C2 ratio (P = 0.045). In batch cultures, when starch was used as substrate, CHI decreased acetate proportion (P = 0.016) and methane production (P = 0.03) and increased propionate and valerate proportions and C3:C2 ratio (P < 0.001). When cellulose was used as substrate, CHI decreased in vitro OM digestibility (P = 0.033), total VFA concentration, propionate proportion (P < 0.001), C3:C2 ratio (P = 0.006), methane production (P < 0.001), NH(3)-N concentration (P = 0.019), and gas production rate (P = 0.002), and increased butyrate (P = 0.029) and BCVFA (P = 0.004) proportions and pH (P < 0.001). When the alfalfa hay and concentrate diet was used as substrate, CHI decreased butyrate (P < 0.001) and BCVFA (P = 0.008) proportions, methane (P = 0.005) and asymptotic gas production (P = 0.02), and gas production rate (P = 0.05). In the second trial, CHI decreased NDF apparent digestibility (P = 0.09). In conclusion, CHI shifted ruminal fermentation toward energetically more efficient routes, without reducing OM apparent digestibility.

The objectives of this work were 1) to compare the goodness-of-fit of empirical models of the lactation curve and 2) to analyze the factors affecting the shapes of the lactation curves, the parameters describing them, and the overall milk yield of Latxa dairy sheep. A total of 14,699 records from 2711 ewes, collected during three consecutive years (1995 to 1997) by the milk recording program of the Latxa ewe of the Basque Country (Spain), were used. Six mathematical models and three fitting procedures were compared. The estimation of model parameters by nonlinear fitting procedures was superior to that by linear regression methods. A nonlinear variable decay model fitted the data better than the other models, as judged by lower mean square prediction error, residual sums of squares, and a lack of first-order positive autocorrelation as assessed by the Durbin Watson coefficient. The effects of the flock, flock-year interaction, month of lambing, length of lactation nested within month of lambing, parity, and number of live lambs born had significant effects on the parameters of the model and the total milk yield (P < 0.01). The prediction of milk yield from the selected model was similar to the estimates obtained with the Fleischmann method currently used by the national breeding program for the Latxa breed.

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The relationships between body weight (BW), body condition score (BCS) and internal fat deposits were studied in Latxa dairy ewes. In 2 years, the BW and BCS of 20% of the ewes in 14 flocks were recorded at the beginning of the mating period (pre-mating), and in the 1st month of lactation (post lambing). BW increased with age (BW = 54-05 X (l-e-°9 88Xa z e ), and the mature weight was not reached until 4 years, after which weight did not differ between pre-mating and post-lambing periods. Body condition score, however, differed between the two periods. The regression coefficients (b) of BW on BCS, when flock-year and age were included in the regressions, differed significantly (P < 0-05) in the pre-mating and post-lambing periods, and were 5-3 (s.e. 0-31) and 6-3 (s.e. 0-43) kg per unit BCS, respectively. The correlation coefficients (r) were 0-77 and 0-71 respectively, compared with 0-42 and 0-38 when the flock-year and age of the ewes were not included in the regression.Thirty-seven of these ewes, with BCS between 0-75 and 4-00, were slaughtered, the weights of omental, mesenteric and kidney and channel fat recorded, and the lumbar fat thickness assessed at the last rib. The regressions between the weight of fat deposits and lumbar fat thickness and BW and BCS fitted to semi-logarithmic equations, except for mesenteric fat, in which the relationship was linear. Body condition score was a better predictor than BW for individual fat deposits, with proportionately 0-81 to 0-83 of the variation in the weight of the deposits accounted for by variation in BCS and 0-57 to 070 by variation in BW.

Atlantic mountain pastures are composed by mosaics of semi-natural grasslands and heathlands. A knowledge of their structure and feeding value is useful to understand their livestock use and improve management of these communities. This study was carried out in the Gorbeia Natural Park in northern Spain. Pasture composition, sward height and nutritive value were measured over four grazing seasons (spring, summer, late summer and autumn) in three plant communities: grassland (GR), open heathland (OH) and dense heathland (DH). The grassland community had lower sward height and better nutritive value. In less favoured grazing periods, when sward height in GR becomes limiting livestock move to OH with higher pasture height and lower sward cover and nutritive value. Even both heathlands have similar height and quality, the selection of OH, and avoiding of the dense one, could be due to its higher sward cover, which could make it easier to look for feed. Moreover, considering the woody component the estimated nutritive value of DH does not cover the minimum required for livestock production.

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