Fabiana Kellermann de Freitas

Suplementação energética na recria de bezerras de corte mantidas em pastagem de inverno

This work was carried outo to evaluate the effect of levels of energetic supplementation in productive and reproductive performance of sixty-four Charolais heifers and their crosses with Nellore, mantained in cultivated pasture of black oat (Avena strigosa Schreb) plus Italian ryegrass (Lulium mulktiflorum Lam.). The treatments considered supplementation of 0; 0.7 and 1.4% of the live weight (LW)/day of rice bran associated with citric pulp, in the proportion of 1:1. A continuous grazing system with variable stocking rate was used, to maintain 1500 kg/ha of DM in herbage mass in all treatments. The following parameters were evaluated: average daily gain, stocking rate, live weight gain, body condition, pelvic area, weight at puberty and age at puberty, hip height and estimated intake of DM. The supplementation increased average daily gain, stocking rate and live weight gain. Heifers kept only on pasture had lower body conditions and showed lower heat percentage than heifers supplemented with 0.7 and 1.4% of LW/day with no differences (P>0.05) between the 0.7 and 1.4% levels. The percentage of heifers showing heat until 16 months of age was 9.1; 68.7 and 70.6%, respectively. The supplementations levels did not affect pelvic area, age at puberty and hip height. The estimated intake of DM was lower for the level of 1.4 % LW/day.

Efeito de níveis de suplementação sobre o comportamento ingestivo de bezerras em pastagem de aveia (Avena strigosa Schreb.) e azevém (Lolium multiflorum Lam.)

Foi avaliado o comportamento ingestivo de bezerras de corte submetidas a diferentes niveis de suplementacao energetica. Os niveis testados foram (0; 0,5; 1,0; 1,5% do peso vivo), em pastagem de aveia preta (Avena strigosa Schreb.) e azevem (Lolium multiflorum Lam.). O suplemento foi farelo de trigo, fornecido diariamente as 14h. Para registro das atividades de pastejo, ruminacao, ocio e permanencia no cocho, adotou-se a observacao visual, feita a cada dez minutos, durante 24 horas, em quatro datas. Para cada nivel de suplementacao, foram observados seis animais dos grupos geneticos Charoles, 3/4 Charoles/Nelore e 5/8 Nelore/Charoles, com aproximadamente oito meses de idade e peso inicial de 158 kg. Os animais que receberam suplementacao diminuiram o tempo de pastejo em relacao aos nao-suplementados, sem alteracao no consumo estimado de forragem. Os animais que receberam suplementacao a 1,5% do PV permaneceram mais tempo no cocho, aumentando a frequencia de retorno ao cocho nos maiores niveis de suplementacao. Os niveis de suplementacao nao interferiram nos tempos de ruminacao e ocio.

Desenvolvimento de novilhas de corte recebendo ou não suplementação energética em pastagem com diferentes disponibilidades de forragem

ABSTRACT - The effect of two herbage masses (HM) (1,200 or 1,500 kg/ha of dry matter - DM) and use of energy supplementationon performance of beef heifers grazing oat ( Avena strigosa Schreb) plus annual ryegrass ( Lolium multiflorum Lam) was evaluated. Theheifers were assigned to the following treatments: LHMNS - low herbage mass, no supplementation; HHMNS - high herbage mass, nosupplementation; LHMS - low herbage mass + supplementation; HHMS - high herbage mass + supplementation. The supplement utilizedwas ground sorghum grain, at the level of 0.7% of body weight (BW) per day. The grazing method was continuous with variable sto ckingrate; there were three replications per treatment combination. The variables evaluated were: forage allowance (FA), average dai ly weightgain (ADG), body condition (BC), body weight of animals at 12 months of age (BLW), crude protein and ´in vitro´ digestibility o f handplucked herbage samples. The FA in HHM was greater than in LHM treatment, with values of 11 and 8 kg of DM/100 kg of BW,respectively. Supplementation affected ADG and BC. The ADG were 0.778 and 0.559 kg/animal/day for supplemented and notsupplemented heifers, respectively. The BC increased linearly during the grazing period. Supplemented heifers body condition in creasedby 0.9 points (R2=96%) and those exclusively on pasture by 0.4 points (R2=74%), with LW gains of 115 and 187 kg for each additi onalpoint of BC. Decrease of forage mass from 1.500 to 1.200 kg/ha DM did not affect heifer performance. Supplemented animals had h igherbody weight gain and body condition than animals exclusively on pasture.Key Words:

Suplementos energéticos para recria de novilhas de corte em pastagens anuais: análise econômica

An economic evaluation was accomplished of two experiments with intensive feeding systems for rearing of beef heifers weaned with 60-90 days. In experiment 1, the heifers reared in Pearl Millet pasture, exclusively under grazing (PAST1); supplemented with milled corn grain (PAST1/C) or supplemented with pellet citric pulp (PAST1/P). In experiment 2, the heifers were reared in Oat plus Italian Ryegrass pasture without supplementation to the animals (PAST2); supplemented with milled corn grain (PAST2/C) or supplemented with soy hull (PAST2/H). With the results of animal production per hectare and composition of the costs was realized an evaluation of the direct financial response of the studied feeding systems. Based on the live weight of the heifers at twelve months of age a bioeconomic analysis of the employed technologies was presented. In experiment 1, the milled corn grain supplemented presented financial loss, while other systems just only covered costs, without surplus gross margin. In experiment 2, the corn grain system covered only costs, and the exclusive use of the pasture and the soy hull supplementation provided satisfactory values of gross margin for hectare. The increase of birth rate from 50 to 80% or the reduction of the age at first mating of the heifers from three to two years could reduce, respectively, in 62 and 23% the number of unproductive females in the herd for each 100 pregnant cows. These practices present potentiality to reduce this number of animals in 74%, when accomplished jointly.

Características produtivas e estruturais do milheto e sua relação com o ganho de peso de bezerras sob suplementação alimentar

The productive and structural characteristics of Pearl millet (Pennisetum americanum (L.) Leeke) under continuous stocking rate and their relationship with beef heifers performance exclusively under grazing (PAST), supplemented with corn grain (PAST + C) or citric pulp (PAST + P) was evaluated. There was no difference among treatments for herbage mass, forage allowance, leaf lamina mass, leaf lamina allowance, daily accumulation rate of forage and herbage total production. Daily accumulation rate of forage, leaf lamina mass and leaf lamina allowance decreased linearly during the grazing period. The participation of Pearl millet components in the sward structure was similar among treatments and changed during the time. The energetic supplementation increased the stocking rate at beginning of grazing, with high leaf lamina participation in the canopy and increased the average daily gain in subsequent periods, with decreasing of the leaf lamina participation. The effect of energetic supplementation on Pearl millet pasture is linked with the amount and distribution of leaf lamina in the canopy structure. The energetic supplementation does not affect the structural and productive characteristics of pearl millet.

Produção de forragem e produção animal em pastagem com duas disponibilidades de forragem associadas ou não à suplementação energética

The trial was conducted to evaluate two forage availabilities (1.200 and 1.500 kg/ha of dry matter [DM]) and energy supplementation of winter pasture on herbage and animal yields. The pasture was a mixture of oat (Avena strigosa Schreb) + Italian ryegrass (Lolium multiflorum Lam). Ninety Charolais and Charolais crossbred Nellore heifers, with initial live weight of 164 kg, were submitted to the following treatments: LFA - low forage availability; HFA - high forage availability; LFAS - low forage availability + supplementation; HFAS - high forage availability + supplementation. The daily supplementation of ground sorghum corresponded to 0.7% body weight (BW). The variables studied were forage accumulation rate (FAR), stocking rate (SR) and live weight gain (LWG). Forage availability and supplementation did not affect FAR, which averaged 45.53 kg/ha DM. The average SR in DFA, 862 kg/ha of BW, was quite constant during pasture grazing cycle. The SR was extremely variable in LFAS, HFA and LFAS treatments, being greatest in LFAS treatment after 08/26. Body weight gain per hectare was not affected by forage availability but increased by 59.4% in response to pasture supplementation.