Natural and improved pastures on growth and reproductive performance of Hereford heifers

Abstract

-This study evaluated yearling growth and reproductive performance of Hereford heifers at 24-26 months of age grazing on natural pastures at two stocking rates during winter and spring, associated or not to improved natural pastures.Heifers were classified according to three weight groups (Light, Medium and Heavy) and randomly distributed into four feeding management practices: 0.6 AU (1 animal unit = 450-kg body weight) -heifers on natural pastures at a stocking rate of 0.6 AU/ha; 0.8 AU -heifers on natural pastures at a stocking rate of 0.8 AU/ha; 0.6 AUI -heifers on natural pastures at a stocking rate of 0.6 AU/ha and on improved natural pastures between Sept 1 st and Nov 1 st ; 0.8 AUI -heifers on natural pasture at a stocking rate of 0.8 AU/ha and on improved natural pastures between Sept 1 st and Nov 1 st . The stocking rate of 0.8 AU resulted in significant weight loss during winter months (-0.138 and -0.356 kg for 0.6 and 0.8 AU, respectively). Heifers grazing during the spring on improved natural pastures presented higher weight gain before the breeding season and higher body weight and body condition score in the beginning and end of the breeding season in relation to those grazing only on natural pastures. Heifers kept at 0.6 AU/ha obtained 69.7% pregnancy rate, which was significantly higher than the 54.2% of those managed at 0.8 UA/ha.Heifers grazing on improved natural pastures during the spring achieved 83.8% pregnancy rate, whereas those maintained on natural pastures achieved only 40.2%. Light and medium heifers lost less weight during the winter as compared with the heavy ones, but weight differences between groups remained until the end of the breeding season. Heavy heifers have higher pregnancy rates. Heifers submitted to lower stocking rate and those grazing on improved natural pastures conceive earlier.

Performance of beef cows of different genetic groups in natural and cultivated pastures

“…This increased expression of estrus in the reproductive period is a consequence of the better nutritional conditions to which the cows were submitted, reflected in the higher weight and better body condition scores. Rosa et al (2012), working with heifers detected increased weight gains and improved reproductive performance when they were kept in improved natural pastures as compared with heifers maintained exclusively in natural pastures, linking these facts to the major input of nutrients supplied by pasture quality triggering secretion and the release of reproductive hormones.…”

“…The weight gain of cows is an indication of fertility in cattle (ROSA et al, 2012), and the concern over satisfactory food levels in pre and post calving is so that the subsequent reproductive performance is not impaired. The higher body condition in cows kept in cultivated pastures had positive effects on subsequent reproduction (Table 3).…”

Effect of live weight of beef cows on calf production efficiency

“…Reproductive indices of cow herds can be influenced by age (Bitencourt, et al, 2020;Fordyce et al 2103), the breed or genetic group of cows (Vaz, et al, 2016a), and especially by the nutritional level to which the herds are subjected to (Restle, et al, 2007, Rosa, et al, 2012. In the present study, none of the variables could affect reproductive performance influenced it, including the cow weight, whose major importance is in non ideal nutritional situations (Burns, et al, 2010;Scasta, et al, 2015).…”

“…Breeding herds in Brazil have their feed primarily based on the natural pastures or those introduced, all of which depend on climatic conditions (Rosa, et al, 2012). These pastures due to their quality limit the animals to express their genetic potential for weight gain and reproduction.…”

Productive efficiency of cows primiparous aberdeen angus of the body size and milk production levels

“…Despite the advance in technologies and their use, native grasslands remain the basic food for beef cattle, and, because of the climatic conditions and diversity of species in southern Brazil their quantity and quality oscillate throughout the production cycles; moreover, the poor management to which they are subjected (ROSA et al, 2012) limits animal production in certain periods.…”