Forage Allowance and Cow Genotype, Tools to Increase Animal Production in Native Pastures

Forage Allowance and Cow Genotype, Tools to Increase Animal Production in Native Pastures

In eight plots (four per block) the effects of two FA per two cow genotypes were tested from August 2007 to March 2010, on a Campos grassland (major species were Axonopus affinis, Oxalis sp., Cyperus sp., Cynodon dactylon, Eryngium nudicaule, Gaudinia fragilis, Chevreulia sarmentosa, Stipa setigera, Paspalum notatum and Coelorhachis selloana) in Uruguay (32º 20` S, 54º 26` W). Forage allowance varied seasonally, in HIGH (5, 3, 4 and 4 kg DM/kg LW) and LOW (3, 3, 2 and 2 kg DM/kg LW) during autumn, winter, spring and summer; respectively. Continuous stocking method was applied throughout the year, with FA adjusted monthly, using the “put and take method” (Mott and Lucas 1952). Thirty PURE (Hereford and Aberdeen Angus) and thirty CROSS (F1 reciprocal Hereford and Angus crosses) multiparous cows, aged four to eight years with normal calving and pregnancies, were randomly assigned to the plots. Cow LW and BCS were measured monthly and in key moments such as calving and at the beginning of the breeding season. BCS was visually assigned on a scale ranking from 1 = very thin to 8 = very fat (Vizcarra et al. 1986). Cows did not breed during summer 2010. Data of cow LW and BCS and calf weight at weaning (94 ± 31 d) were analyzed using the MIXED procedure (SAS Institute, Cary, NC, USA, 2002). The model included FA, cow genotype, year and their interactions as fixed effects, block as random effect, and for cow BCS at the beginning of the breeding season, cow BCS at calving was used as covariate. Tukey–Kramer test were conducted for mean separation (α = 0.05).