Suplementação da dieta de novilhos de três grupos genéticos em pastagem de Brachiaria brizantha cv. Marandu

This trial was carried out to study the effects of supplementation level on performance of steers from different genetic groups (Nellore x Red Angus (NR), Nellore (NL) and Holstein crossbred (MH), and three experimental periods. The performance data for first period were analyzed according to randomized block (RB) design, with 3 treatments ((NR, NL and MH)) and 3 blocks. In second period, the RB design used with 3 x 3 factorial design, and 3 blocks. Factor A determined the group (NL and MH) and factor B the supplementation levels (0.2, 0.6 and 1% LW). In third period, the data were evaluated according to completely randomized design, with 2 x 3 factorial design. Factor A determined the group and factor B, three levels of supplementation. In the first, higher weight gain (p < 0.05) was observed for NR (0.79 kg day-1) compared to MH and NL (0.73 and 0.61 kg day-1). The concentrate intake varied for N. NR showed higher (p < 0.05) WG (0.91 kg day-1) compared to NL (0.75 kg day-1) and MH (0.76 kg day-1). The levels of supplements influenced (p < 0.05) WG (0.68, 0.81 and 0.92 referring to levels of 0.2, 0.6 and 1.0% LW). In third period, MH presented greater WG < 0.05) (0.895 kg day-1). No difference was verified on animals with 0.8 and 1.2% LW, with WG of 0.92 and 0.82 kg day-1.

Sources of omega-6 fatty acids do not alter the rumen degradation and transit of fibre from dairy cow diets

The objective of this study was to evaluate the behaviour of fibre in the digestive tract on the basis of the passage kinetics of forage and concentrate particles in cows fed different omega-6 fatty-acid sources. The scientific hypothesis of this study was that omega-6 fatty acids do not interfere with the digestion of fibre in the diets of dairy cows. Five primiparous lactating Holstein cows were used in the experiment. The experimental diets were: control (C), ground soyabean (GS), cottonseed (CS), soyabean oil (SO), calcium salts of fatty acids (CSFA). The global mean estimates for the parameters of passage rate (gamma) were 0.038 and 0.055 h(-1) for forage and concentrate, respectively. The only significant effect with respect to the passage rate was a high negative correlation between the concentrate passage rate and dry matter intake. There was less undegradable neutral detergent fibre (NDF) in treatments without added lipid. Dietary supplementation with lipid sources does not alter the kinetic parameters of roughage and concentrate particle passage or in vitro NDF degradation. Sources of omega-6 fatty acids do not alter the rumen degradation and transit of fibre.

Inducing ovulation early postpartum influences uterine health and fertility in dairy cows

The objective of the current study was to evaluate the effect of GnRH early postpartum on induction of ovulation, uterine health, and fertility in dairy cows. Holstein cows without a corpus luteum (CL) at 17 +/- 3 DIM were assigned randomly to receive i.m. GnRH (n = 245) at 17 +/- 3 and 20 +/- 3 DIM or remain as controls (n = 245). Ovaries were scanned by ultrasonography twice weekly totaling 4 examinations. Ovulation was characterized by the appearance of a CL >= 20 mm at any ultrasound or CL <20 mm in 2 consecutive examinations. Clinical and cytological endometritis were diagnosed at 35 DIM. Compared with control, GnRH increased ovulation up to 3.5 d after the last treatment (78.7 vs. 45.0%) and did not affect the prevalence of clinical endometritis (23.9 vs. 18.6%) or cytological endometritis (30.9 vs. 32.8%). Prevalence of clinical endometritis increased in cows that had calving problems (32.6 vs. 15.9%) and metritis (40.6 vs. 15.8%). Metritis increased prevalence of cytological endometritis (50.7 vs. 23.5%). Treatment with GnRH did not affect pregnancy per artificial insemination at 32 (37.6 vs. 38.6%) or 74 d after artificial insemination (35.0 vs. 31.5%), but reduced pregnancy loss (6.8 vs. 18.1%). No overall effect of GnRH treatment on hazard of pregnancy was observed; however, an interaction between GnRH treatment and ovulation showed that GnRH-treated cows that ovulated had increased hazard of pregnancy by 300 DIM compared with GnRH-treated and control cows that did not ovulate (hazard ratio = 2.0 and 1.3, respectively), but similar to control cows that ovulated (hazard ratio = 1.1). Gonadotropin-releasing hormone early postpartiim induced ovulation without affecting uterine health, but failed to improve pregnancy per artificial insemination or time to pregnancy, although it reduced pregnancy loss.