. Grazing behaviour and weight change of cattle turned out to pasture in spring. Can. J. Anim. Sci. 83: 801-808. In the first of two trials, 20 Hereford steers were allocated to two adjacent 1.6-ha pastures on 29 May 1996. Steers in one pasture were given no supplement, while those in the other received supplemental silage each day. All steers on each treatment grazed their allocated paddock continuously for 28 d. Steers on pasture were weighed and their behaviour was monitored periodically throughout the 4 wk of grazing. The dry matter (DM) availability at turnout (651 kg hd -1 ) was considered in excess to requirement, since neither availability nor sward height declined over 28 d. In spite of this, steers lost 15 kg after turnout and took 12 d to regain their initial weight. There were no treatment effects. Nutrient composition of the sward changed in accordance with advancing maturity. Percent of time observed grazing (51%) did not change over the 28-d period; however, rumination time increased from around 10 to 30%. Grazing behaviour was similar for steers on both treatments. Silage intake averaged only 1.3 kg DM hd -1 d -1 . In 1997, 28 yearling steers were used in a 2 × 2 factorial design to study the effect of turnout date to pasture [21 May (E) vs. 4 June (L)] and supplemental silage feeding on weight change, grazing behaviour, pasture productivity and forage quality over 28 d. The DM availability at turnout was 391 kg hd -1 . Available DM and sward height declined in both early and late treatments after turnout. The early group had to be removed from the trial after 16 d when sward height dropped below 4 cm. Sward quality after turnout declined only for the late group. Loss of body weight (BW) and days to regain initial BW after turnout were greater for early versus late steers. Steers ate only 0.5 kg silage DM hd -1 d -1 , but this reduced weight loss in late steers. Cattle turned out later spent less time grazing (P < 0.001 at 5 and 14 d) but no less time ruminating. Transient weight loss associated with turnout to pasture cannot be wholly explained by behavioural patterns. Other factors, such as altered ruminal conditions, must also play an important role. Can. J. Anim. Sci. 83: 801-808. Dans le premier de deux essais, le 29 mai 1996, on a placé 20 bouvillons Hereford dans deux pâturages adjacents de 1,6 ha. Seul les animaux du second pâturage ont reçu quotidiennement un supplément d'ensilage. Dans les deux cas, on a laissé les animaux brouter à satiété l'herbe de leur enclos pendant 28 jours. On a pesé et surveillé le comportement des animaux périodiquement durant les quatre semaines de paissance. La quantité de matière sèche disponible à la mise à l'herbe (651 kg par tête) dépassait les besoins des animaux, puisqu'au terme des 28 jours, ni les stocks ni la hauteur des graminées n'avaient diminué. Malgré cela, les animaux ont perdu 15 kg à la mise à l'herbe et il leur a fallu 12 jours pour retrouver leur poids original. Le temps passé à paître (51 %) n'a pas varié au cours des 28 jours, mais celui ...

The feasibility and profitability of management-intensive grazing (MIG) in Atlantic Canada was studied. Productivity of MIG plus concentrate (1 kg:3 kg of milk) was compared with that of confinement feeding (Confined) using haylage (1996) or corn silage (1997) as 50% of dry matter (DM) in a total mixed ration (TMR). Each year, two groups of 10 Holsteins were used. In 1996, pasture CP content increased from 15.2 to 18.0% of DM, while those of acid detergent fiber (ADF) and neutral detergent fiber (NDF) decreased (33.6 to 23.8%, and 55.6 to 35.4%, respectively) between July 10 and August 28. In 1997, pasture crude protein (CP) content decreased from 30.0 to 15.7%, while ADF and NDF increased (24.9 to 35.8% and 53.5 to 67.4%, respectively) from June 16 to July 14. Because pasture biomass was reduced by winter-kill followed by drought in 1997, MIG cows were supplemented with TMR. Estimated pasture DM intakes ranged from 14.2 to 18.1 kg/d per cow. Milk yields averaged 29.5 and 30.4 +/- 0.43 kg/d in 1996 and 32.5 and 31.8 +/- 0.61 kg/d in 1997 for Confined and MIG cows, respectively. In 1996, the dietary treatment x time interaction was significant. Cows in MIG had higher yields than those in Confined later in the trial, while fat and CP concentrations were usually lower in milk from MIG cows. Lower body weights resulted with MIG. Few differences between production systems were significant in 1997. Milk revenue (Canadian $/d) from Confined cows was higher (14.03 vs. 13.77 in 1996 and 16.10 vs. 15.39 in 1997), but partial profitability of the MIG system was marginally greater in both years.

. 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...

No abstract

Minimizing nutrient surpluses and improving efficiency of nutrient use are key challenges for all dairy farming production systems, driven by economic, environmental and increasing regulatory constraints. Our study examined the efficiency of N, P and K use on a commercial dairy farm through an integrated approach that evaluated the nutrient status of all aspects of the production system of the case-study farm, a 75 lactating Holstein cow dairy in Kings County, Nova Scotia, Canada. During the decade after 1988, the farm owner implemented a series of changes in production practices, including diversification of the crop rotation, implementation of a management intensive grazing (MIG) regime and adoption of a systematic approach to soil and nutrient management. Milk production, and associated farm exports of N, P and K, increased by 666 kg cow' 1 between 1990 and 2000. Purchases of N-P-K fertilizers were eliminated in 1990 and feed nutrient imports were dramatically reduced. Feed costs per liter of milk declined from 14.3 cents (CDN) liter' 1 in 1990-92 to 11.6 cents liter' 1 in 1998-2000, even as feed prices increased regionally by 10-20% over the same period. Modeling of current whole farm mass N, P and K balance indicated that 25.0% of all N inputs are recovered inform products, milk and meat. Non-legume-derived field N input (67 kg Nha' 1 before losses) was close to optimum for the predominantly legume/grass-based forage cropping system. Model-determined annual farm nutrient surpluses (outputs-inputs) for P (9.0kgha~' yr~') and K (8.2 kg ha' 1 yr~') were significantly lower than those previously reported for regional confinement-based dairy farms, which were more reliant on corn production. However, data from 16 years of soil analysis (1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001) indicated an increase in soil-test P levels of approximately 2 mg kg~' yr~'. Recent refinements in dairy animal dietary P levels have further reduced the farm P surplus (2.6 kg ha' 1 in year 2001) and are shown as key to a strategy for reversal of the trend in soil-test P levels. In summary, the combined approach of wholefarm system nutrient management, crop diversification and MIG increased milk production and minimized costs while reducing farm nutrient inputs. The study demonstrates how an approach to dairy farm nutrient management which integrates livestock and crop nutrient requirements may reduce dairy farm nutrient loading while maintaining productivity.