The effect of spring turnout date on weight gain by cattle on native pasture

Abstract

. 2002. The effect of spring turnout date on weight gain by cattle on native pasture. Can. J. Anim. Sci. 82: 575-585. The effect of early turnout on pasture quality and weight gain by beef cattle was assessed with 32 Hereford feeder cattle which were turned out on pasture on four separate dates in each of 2 yr in a randomized complete block design with two replications. In 1998, steers were allocated to four treatments numbered consecutively T1 to T4 according to turnout date: 6 May [110 growing degree days above 5°C (GDD)], 13 May (152 GDD), 20 May (195 GDD) and 27 May (255 GDD). Steers grazed separate 0.4-ha paddocks continuously for 28 d. In 1999, turnout dates were 11 May (124 GDD), 18 May (156 GDD), 26 May (226 GDD) and 2 June (304 GDD), with 0.6, 0.5, 0.4 and 0.3 ha of pasture allocated to each treatment (two steers, two heifers), respectively. Soil resistance to penetration, sward height, herbage mass and chemical composition, and animal liveweight gain were recorded. Early turnout did not increase soil compaction. Herbage mass at turnout for T1 to T4 was 532, 780, 1370 and 1299 kg dry matter (DM) ha -1 , respectively, in 1998, and 901, 983, 1324 and 1719 kg ha -1 , respectively, in 1999. Herbage mass increased by 273 kg ha -1 per week as turnout was delayed in 1998 and 256 kg ha -1 in 1999. Crude protein concentration declined from approximately 200 g kg -1 DM at T1 to less than 175 g kg -1 DM at T4 in both years. Fibre concentration, as indicated by ADF and NDF, increased 1 wk after turnout. Forage quality declined as turnout was delayed, but grazing did not improve forage quality relative to ungrazed swards. In 1998, cattle in T1 to T4 lost 4.7, 4.0, 1.2 and 4.2% of BW, respectively, in the week after turnout, whereas in 1999, T1 to T4 lost 1.2, 4, 0.5 and 1.5% of BW, respectively. In 1998 over the 28-d period, steers in T1 and T2 lost 0.52 and 0.21 kg d -1 , respectively, whereas steers in T3 and T4 gained 0.60 and 0.51 kg d -1 . In 1999, over the 28-d period, cattle in T1 to T4 gained 1.1, 0.64, 1.1 and 0.61 kg d -1 , respectively, with cattle in T1 gaining significantly more weight (P < 0.014) than those in T4. The results suggest a weight gain of 0.5 to 1.0 kg d -1 can be achieved in a 28 day grazing period with early turnout on native pasture provided herbage mass ranges between 900 and 1300 kg DM ha -1 and approximately 130 kg forage DM head -1 is initially on offer. Ces derniers ont été mis à l'herbe à quatre dates distinctes chaque année pendant deux ans, en blocs entièrement aléatoires répétés deux fois. En 1998, les bouvillons ont été divisés en quatre groupes numérotés T1 à T4 selon la date du lâcher à l'herbe, à savoir : le 6 mai [110 degrés-jour de croissance au-dessus de 5°C (DJC)], le 13 mai (152 DJC), le 20 mai (195 DJC) et le 27 mai (255 DJC). Les animaux ont pâturé dans des enclos distincts de 0,4 ha, sans interruption pendant 28 j. En 1999, le lâcher à l'herbe s'est effectué le 11 mai (124 DJC), le 18 mai (156 DJC), le 26 mai (226 DJC) et le 2 juin (304 DJC), chaque groupe (deux bouv...

Grazing behaviour and weight change of cattle turned out to pasture in spring

“…In year 1, even though pasture availability and quality were non-limiting and cattle had been backgrounded at 0.5 to 0.6 kg d -1 before turnout, they lost 16 kg BW and required almost 16 d to regain their turnout weight. These losses are similar to those reported in the literature for cattle previously gaining 0.5 to 1.0 kg d -1 (Nicholson 1980;Kyne et al 2001;Jannasch et al 2002). In year 2, cattle had been gaining up to 0.9 kg d -1 during confinement and this should have increased the extent of weight loss at turnout.…”

“…A possible negative impact of early turnout is increased poaching and soil compaction. In a related study, Jannasch et al (2002) found no effect of turnout date on soil compaction. In year 2, we tried to evaluate the effect of turning cattle out either just before or just after the anticipated "spring flush" of grass by having two turnout dates.…”

The effects of turnout date to pasture on cattle weight gain

“…Jannasch et al (2002) found that earlier turnout date had inconsistent results -one year showed no significant effects, and one year showed cattle weight actually decreasing with earlier turnout date. Similarly, Charmley et al (2003) found that earlier turnout date decreased weight gain.…”

“…For example, Charmley et al (2003) and Jannasch et al (2002) found that earlier turnout date decreased weight gain, while Steen (2002) found the opposite. In order to resolve these contradictions it is important to elucidate the mechanism of the effect of turnout date.…”

“…Consequently, forage production often exceeds cattle consumption in early spring. Earlier turnout to pasture may provide a partial solution to the problem (Jannasch et al 2002).…”