Proceedings, Western Section, American Society of Animal Science Vol. 56, 2005 USE OF GREEN FODDER PRODUCED IN HYDROPONICS SYSTEMS AS SUPPLEMENT FOR SALERS LACTATING COWS DURING THE DRY SEASON C. Rodriguez Muela*, H.E. Rodriguez, O. Ruiz, A. Flores, J.A. Grado, C. Arzola; Universidad Autónoma de Chihuahua, Chihuahua, Chihuahua, México 2 ABSTRACT: 12 In order to analyze the productive and reproductive behavior of lactating Salers cows with calf there was used hydroponics green fodder (HGF) as supplement from may 1st to July 2 of 2002. There were 35 cows used with 42±4.55 open days. They were paired according to the calving date and randomly assigned to one of two treatments: rangeland forage plus HGF as supplement plus green fodder (GF) and rangeland forage plus irrigated prairie forage (PF). The consumption of forage was 1.07 and 1.32 kg/DM/d of GF and 2.66 and 0.88 kg/DM/d of PF in may and june, respectively. Both groups were bred with fertility tested registered Salers bulls. The cows on PF lost weight (P<0.05) from day 28 (496.88±13.34 kg) to day 56 (459.99±13.34 kg) of the experiment, the GF cows maintained the live weight on the same period (506.13±13.73 and 497.60±13.73 kg, respectively). The cows showed daily live weight lost (P<0.05) on PF and daily weight gain on GF (-0.684±0.09 vs. 0.196±0.09 kg/d respectively). The calves showed differences (P<0.05) between treatments in live weight at day 56 (106.68±2.97 vs. 118.51±3.07 kg on PF and GF respectively). The daily average weight gain of calves from day 0 to 56 was 0.535±0.04 vs. 0.759±0.05 kg/d on PF and GF, respectively. There was an effect of treatment on cow body condition BC (P<0.10). The treatment means were 4.63±0.07 vs. 4.81±0.07 units of BC for PF and GF, respectively. The cycling cows were 17.65, 23.53 and 76.47% for GF and 11.11, 22.22 and 38.89% for PF on the first, second and third samplings, respectively. The estrous cycle was determined on the animal by the presence of more than 1 ng/ml of progesterone on blood serum. The treatments show difference (P<0.05) on the last sampling period being higher for GF. There were no differences (P>0.05) for pregnancy rates on November 2 of 2002 (88.24 vs. 70.59% for PF and GF, respectively). The HGF show being a viable supplement for the lactating cows to sustain weight on rangelands with an acceptable weight gain of calves. Key Words: Green fodder, Supplement, Dry season, Hydroponics. Introduction One problem on the north of Mexico’s beef cattle production is the long drought period, it’s necessary to supplement the animals according with their physiology status to sustain them in good body condition during that period (Gutierrez, 1969). The supplementation on grasslands is made to complement the protein (protein supplementation) and mineral (mineral supplementation) requirements, trying to maintain the animal required levels and complementing the energy requirement. The reproductive behavior on beef cows is close related with the body condition score and the weight change before the breeding period, the supplementary protein produce an positive effect and enhance the exit possibility on the breeding when the cows are in good condition, an unadecuated availability of protein before and after the calve depress the reproductive behavior (Charmley et al., 1999) although the body condition score (BCS) is an important weighting on cattle to estimate the energy reserves (Burke et al., 1998). The intensive production of aliments by hydroponics systems is an alternative on lands not adequate to the agriculture, with extreme ambient conditions and scarce water availability; the developed systems to obtain “hydroponics green fodder” are an viable alternative to the cattle feeding as cause for its nutritive value, digestibility and good consume by the animals on grasslands (Rodriguez y Morales, 2002), considering the arid and semiarid conditions on the regional extensive production systems, its supposed on this work that the supplementation with “hydroponics green fodder” for lactating cows on grasslands can have advantages. The objective of this work was to evaluate the productive behavior, the body condition score, the ciclicity percentage and pregnant percentage of lactating Salers cows supplemented with “hydroponics green fodder” during the drought period on grassland. Materials and Methods The job was carried out on "Nopales" ranch, Chihuahua, latitude of 28º 17', west longitude 106º 15', with an altitude of 1630 msnm. The ranch counts with 950 ha should rangeland, the rangeland coefficient is 15 ha per animal unit (COTECOCA, 1978). Animals description. 35 registered Salers breed lactating cows with calve were used (42±4.55 d open), assigned to two treatments in the following way, they were grouped by two in two for calve date and divided randomly after. Treatments. Control (PF): grassland plus 1 h daily of meadow (n=18), this was a mixture of oat, rye grass, centeno and triticalle; sown at end of October of 2001; it was sown again with sudan sorgum during april and may of 2002 to prolong its use; it was divided into