PF 03. Sward characteristics and winter performance of growing steers on native pasture

To study the Influence of some swards characteristics on weight daily gain (GDM) of Holstein steers in winter a trial was carried out between 04.29.91 and 07.22.91. 24 steers with inicial live weight (PIE) of 110 ± 25 kg were randomly asigned to the following forage allowances: 2.5, 5.0, 7.5 and 10.0 kg DM/100kg LW/day, adjusted by put and take method. The rotative grazed was with 7 days ocupation and 35 days rest. The sward measures were forage availability (DM/ha), sward height (ALT) and ungrazed areas at the begining (DISP) and the end (RECH) of each grazing period. Live weight was recorded every 7 days after 12 hours fasted. The GDM g/animal/day) was determinated by regression anlisys. The models that fits better for the animals performance were: GDM= 0.27 + 0.06ALTDISP - 0.006PIE (r2 = 0.70; CMe = 0.001; P < .01) and GDM = 0.212 + 0.007ALTRECH - 0.004PIE (r2 = 0.60; Cme = 0.008; P < .01). It permit to conclude, for the local condition, it is possible for the animals not to loose weight in winter grazing sward height over 3 cm

Dried, Irradiated Sewage Solids as Supplemental Feed for Cattle

Sewage solids were collected as primary settled solids and then dried and gamma-irradiated (using /sup 60/Co or /sup 137/Cs) to absorbed dosage of about one megarad to minimize viable parasites and pathogenic organisms. Nutrient composition and bioassays with rumen microbes suggested prospective usage as supplemental feed for ruminants. Short-term experiments with sheep and then with cattle further suggested that usage of nutrients could be beneficial and that accumulation of heavy metals was not excessive. A longer-term feeding trial with cattle fed sewage solids as 20% of diet for 68 days demonstrated that tissue uptake of elements such as Cu, Fe and Pb was measurably increased, but not sufficient to exceed ranges considered normal. Likewise, of 22 refractory organic compounds having toxicological interest, only a few were detectible in adipose tissue and none of these exceeded levels that have been reported in tissues from cattle produced conventionally. In a large-scale experiment, beef cows grazing poor-quality rangeland forage during late gestation-early lactation were given either no spplemental feed or cottonseed meal or experimental supplement comprised of 62% sewage solids. Supplements were provided for 13 weeks until rangeland forage quality improved seasonably. Supplemental cottonseed meal for cows improved weaning weights of calves by about 11% over unsupplemented controls; whereas, supplement with 62% sewage solids improved calf weaning weights by about 7%. Hazards or risks to animals or to human health appear to be slight when sewage solids of this type are fed as supplemental feeds to cattle in production programs of this type

Produtividade e eficiência biológica de sistemas pecuários de cria diferindo na idade das novilhas ao primeiro parto e na taxa de natalidade do rebanho no Rio Grande de Sul Productivity and biological efficiency of beef cow-calf systems differing in age at first calving and herd calving rate in Rio Grande do Sul

Foi avaliada por intermédio da simulação a produtividade e eficiência de sistemas de criação de bovinos de corte no Rio Grande do Sul diferindo na idade das novilhas ao primeiro parto (IP, anos) e na taxa de natalidade (TN): "Sistema Tradicional" (ST) IP=4; "Sistema Melhorado" (SM) IP=3; e o "Sistema Um Ano" (SU) IP=2. Em cada sistema foi avaliado o efeito da TN variando entre 50 e 90%. Foi usado um modelo estático determinístico. A resposta em produtividade e eficiência à redução na IP foi dependente da TN. No SM e SU foi determinada resposta curvilinear a aumentos na TN, atingindo uma produção máxima de 83,9 e 77,9 quilos de bezerro desmamado (BD)/ha com TN de 82,5 e 92,3%, respectivamente. No ST a resposta foi linear, com aumentos de 6,1 kg BD/ha a cada 10% de aumento na TN. O custo energético por quilo BD produzido diminuiu linearmente, na medida em que a TN aumentou.<br>A simulation model was used to evaluate productivity and efficiency of beef cow-calf systems in Rio Grande do Sul State with different heifers first calving age (CA, years) and calving rates (CR): "Traditional System" (TS) CA=4; "Improved System (IS)" CA=3; "One Year System (OYS)" CA=2. In each system it was studied the effect of CR varying from 50 to 90%. A statistic deterministic model was used. The effect of reducing CA on productivity and efficiency was dependent of CR. IS and OYS showed a quadratic response curve, with maximum production of 83,9 and 77,9 kg of weaned calf (WC)/ ha for CR of 82,5 and 92,3%, respectively. TS response was linear, with increments of 6,1 kg WC/ha for each 10% increase in CR. Energetic cost per quilogram of WC was reduced linearly with increments in CR