Implications of growth rates and compensatory growth on puberty attainment in Nellore heifers.

This study investigated the effects of growth rates and compensatory growth on puberty attainment in Nellore heifers. Nellore heifers (n = 120), weaned at 8 ± 0.75 mo of age, were blocked by sire and BW (180 ± 8.6 kg) and assigned randomly to receive 1 of 4 treatments over a 10-mo period. Treatments included ad libitum feeding (high gain, HG), feed intake to gain 0.6 kg/d (medium gain, MG), restricted feeding (0.2 kg/d) for 4 mo followed by ad libitum feeding for 6 mo (compensatory gain, CG), and alternating periods of ad libitum and restricted feeding for 2 mo each throughout the trial (alternated CG, ACG). Puberty was assessed weekly by transrectal ultrasonography. Blood samples were collected at 8, 11, and 18 mo of age and at puberty to determine circulating concentrations of leptin. At 18 mo of age, nonpubertal heifers were treated with a puberty induction protocol using an intravaginal progestin device. There was no treatment effect (P = 0.17) on the percentage of heifers pubertal by 18 mo of age (HG: 66, MG: 40, CG: 58, and ACG: 52%), BW at puberty, and age at puberty. However, HG heifers had higher ADG (P < 0.01), dry matter intake (P < 0.01), and leptin concentrations (P = 0.03) than heifers from other groups. The response to the puberty induction protocol was similar (P = 0.90) among treatments. Regarding sire effects (genetic effects), there was an effect (P = 0.03) on the percentage of heifers pubertal by 18 mo of age and a tendency (P = 0.07) of sire effect in response to the puberty induction protocol. Compensatory growth appears to be an effective managerial approach to decrease feeding costs and stimulate puberty in Nellore heifers.

Thyme essential oil for sheep: effect on rumen fermentation, nutrient digestibility, nitrogen metabolism, and growth / Óleo essencial de tomilho para ovinos: efeito na fermentação ruminal, na digestibilidade dos nutrientes, no metabolismo de nitrogênio e no crescimento

Two experiments were conducted to evaluate the effect of thyme (Thymus vulgaris) essential oil (EO) doses on rumen fermentation, nutrient digestibility, and nitrogen metabolism, as well as performance and coccidia oocyst discharge. In experiment I, 20 rumen-cannulated wethers received the experimental diets containing 80% dry matter (DM) of haylage and 20% DM of concentrate. Treatments were 25mg of monensin/kg DM or doses of 1.25, 2.50, or 3.75g of thyme EO/kg DM. In experiment II, 50 ewe lambs received the same diets from experiment I, including a diet without feed additives. Wethers fed with diets containing 1.25g/kg DM of thyme EO had higher molar proportion of propionate (P= 0.03) and butyrate (P< 0.01), and lower (P= 0.04) acetate to propionate ratio than other treatments. Adding thyme EO to diets increased (P= 0.02) nitrogen retention compared to monensin. The performance of ewe lambs was not affected (P≥ 0.05) by treatments. However, lambs fed monensin had a lower (P= 0.04) number of coccidia oocyst discharge than others. Adding 1.25g/kg DM of thyme EO in high-forage diet improved ruminal fermentation. Thyme EO enhanced nitrogen metabolism, however, it did not improve performance.(AU)

Dois experimentos foram conduzidos para avaliar o efeito de doses de óleo essencial (OE) de tomilho (Thymus vulgaris) sobre a fermentação ruminal, a digestibilidade de nutrientes e o metabolismo de nitrogênio, bem como sobre o desempenho e a descarga de oocistos de coccídeos. No experimento I, 20 ovinos canulados receberam dietas experimentais contendo 80% de matéria seca (MS) de pré-secado e 20% de MS de concentrado. Os tratamentos foram 25mg de monensina/kg de MS ou doses de 1,25, 2,50 ou 3,75g de OE de tomilho/kg de MS. No experimento II, 50 borregas receberam as mesmas dietas do experimento I, incluindo uma dieta sem aditivos. Os animais alimentados com dietas contendo 1,25g de OE de tomilho apresentaram maior proporção molar de propionato (P=0,03) e de butirato (P<0,01) e menor (P=0,04) relação acetato/propionato do que outros tratamentos. A adição de OE de tomilho nas dietas aumentou (P=0,02) a retenção de nitrogênio em comparação com a monensina. O desempenho de cordeiros não foi afetado (P≥0,05) pelos tratamentos. No entanto, cordeiros alimentados com monensina apresentaram menor (P=0,04) número de oocistos de coccídeos. A adição de 1,25g/kg de MS de OE de tomilho na dieta forrageira melhorou o perfil da fermentação ruminal. O OE de tomilho aumentou a retenção de nitrogênio, no entanto não melhorou o desempenho.(AU)