ABSTRACT
Calf birth weights, weaning weights, and preweaning gain of Simmental-sired calves from Angus-Hereford (AH) and Brahman-Hereford (BH) F1 cows grazing native rangeland (NR) or native rangeland-complementary forage (NRCF) systems in the southern Great Plains mixed prairie were evaluated. Calves from AH dams were heavier (P < .001) at birth than calves from BH dams in both forage systems (40 and 37 kg, respectively). However, birth weights of calves from BH dams were 2 kg heavier (P < .001) in the NRCF fall-calving system. Calves in the NRCF system were 122 d older and heavier (P < .001) than the NR calves at weaning (343 and 256 kg, respectively). During the preweaning period, the NR calves gained faster (P < .001) than the NRCF calves. When calves from both systems were evaluated at 200 d of age, NR calves were heavier (P < .001) than NRCF calves. Calves from BH cows were 8 to 16 kg heavier (P < .001) that calves from AH cows at 200 d of age and at weaning. The increased age at weaning associated with the NRCF did not reduce reproductive efficiency. The NRCF system requires less land than a traditional NR system to support a cow-calf pair and seems to be more economically efficient.
Subject(s)
Animal Feed/standards , Breeding , Cattle/physiology , Pregnancy Rate , Animals , Birth Weight/physiology , Cattle/genetics , Female , Food, Fortified , Genotype , Male , Pregnancy , Reproduction/physiology , United States , Weight Gain/physiologyABSTRACT
Replicated cow herds of 15 Angus x Hereford (AH) and 15 Brahman x Hereford (BH) F1 cows each were placed on native rangeland (NR) or native rangeland-complementary forage (NRCF) systems. The NR was 8.1 ha of sagebrush-mixed prairie per cow-calf unit and the NRCF used the same mixed prairie complemented by .4 ha of double-cropped winter wheat and summer annual forage replacing about 30% of the mixed prairie for each cow unit. Calving seasons, spring for NR and fall for NRCF, were selected to complement the respective forage systems. Cow weights, reproductive performance, and population demographics were measured through seven calf crops to investigate their relationship to forage systems and cow breed types. Seasonal average cow weights increased from 484 +/- 7 (SE) kg during calf crop 1 to a peak weight of 568 +/- 8 kg at calf crop 5. Average weight of AH cows was 514 +/- 3 kg, compared with 539 +/- 3 kg for the BH cows (P < .01). Angus x Hereford and BH cows were 38 and 44 kg heavier, respectively, on the NRCF system than on the NR system. The average percentage of reproduction for AH cows was 90 +/- 2%, compared with 87 +/- 2% for the BH cows (P < .13). Both breeds had approximately 87 (AH) to 89% (BH) reproductive rate on the NR system. In contrast, AH cows had 94 +/- 2% reproduction on the NRCF system, compared with 84 +/- 2% for the BH cows.(ABSTRACT TRUNCATED AT 250 WORDS)
Subject(s)
Animal Feed , Animal Husbandry , Cattle/physiology , Reproduction , Weight Gain , Animals , Breeding , Cattle/genetics , Cattle/growth & development , Cattle Diseases/epidemiology , Crosses, Genetic , Dystocia/epidemiology , Dystocia/veterinary , Female , Lactation/physiology , Male , Pregnancy , Random Allocation , Reproduction/genetics , Seasons , Weaning , Weight Gain/geneticsABSTRACT
A replicated factorial experiment was designed to test the hypothesis that manipulating inputs of water and mineral nitrogen to a semiarid grassland would disrupt existing interactions resulting in alteration of the structure of the primary producer community. Alteration of community structure was measured as either changes in growing season average biomass of 6 functional groups of plants or their relative contribution to total biomass.Additions of water greatly increased total biomass and resulted in the replacement of one of the dominant functional groups by a subordinate group. The water plus nitrogen treatment resulted in large biomass increases in two of the dominant functional groups, elimination of succulents as an important component of community structure, and establishment of several introduced weedy species. Continuation of the experiment will likely result in complete dominance of the water plus nitrogen treatment by these introduced species.Despite the large changes in community structure observed as a result of water- and nitrogen-induced stresses we conclude that the shortgrass prairie in northcentral Colorado is asymptotically stable with respect to these influences.
