Investigation of Pasture and Confinement Dairy Feeding Systems Using Jersey and Holstein Cattle.
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2000-04-27
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Today, dairy farmers in the U.S. are faced with the challenge of reducing the cost of producing milk. Milk prices have risen very little in the past decade, while the cost of producing milk has risen steadily. In North Carolina alone, dairy farm numbers have dropped more than 30% in the last ten years, and the trend is expected to continue. Dairy farmers have been forced to increase their profitability to stay in business. In addition, farmers have been forced to comply with stricter environmental regulations. Over the past few years, interest has been shown in intensive management rotational grazing systems. This four-year comparison trial was designed to compare the milk production, herd health, reproductive performance, and environmental impacts of pasture-based and confinement feeding systems using Holstein and Jersey cattle for the Mid-Atlantic region. The project had both Spring and Fall calving herds with breeding via artificial insemination in 75-day periods. Each seasonal herd replicate had 36 cows on pasture and 36 cows in the confinement group. Similar numbers of Holsteins and Jerseys were included in each year. Paddocks grazed comprised 29 ha of cool and warm season pasture species in 37 paddocks for year-round grazing. Pasture-fed cows received variable amounts of grain and baled silage as needed depending upon pasture availability. Confinement cows were housed in a covered freestall barn with access to an exercise lot and received a total mixed ration with corn silage as the primary forage. Confinement cows produced significantly more milk than pasture-fed cows, both for total lactation and average daily production. Reproductive performance of the two treatments did not differ with an overall 75-day pregnancy rate of 68%. Jerseys in both systems did have higher percentages of cows inseminated (96.5%), conception rate (59.6%), and 75-day pregnancy rate (78%) compared to Holsteins (86%, 49%, 57.9% respectively). The percentage of cows infected with at least one case of clinical mastitis was higher in the confinement herd than the pasture-fed herd (43% vs. 24%) with Holsteins higher than Jerseys (41% vs. 26%). Interactions of breed and feeding system and average somatic cell count scores were not significantly different. Pasture-fed cows had lower average body condition scores than confinement cows, ranging from 0.2 to 0.6 points lower on a 5-point scale.In a short-term trial, intake measurements were taken from pasture-fed Holsteins and Jerseys consuming a grain supplement. This supplement was similar to those that were fed to the pasture-fed cows during the four-year trial. It was determined that Jerseys could consume as much as Holsteins at three different feeding levels (6.8, 4.5, and 2.3 kg/cow per feeding). This experiment showed that in certain time frames, Jersey cattle can consume equal amounts of supplements compared to Holsteins. Therefore in mixed groups Jerseys can consume relatively more supplemental energy relative to body size and milk production compared the Holsteins. In another short-term trial using cows from a spring season replicate, milk samples were obtained from pasture-fed and confinement-fed cattle and analyzed for fatty acid composition. The pasture grazed was a warm-season pasture, while the confinement-fed cattle consumed a corn-silage based TMR. The major fatty acid of interest was conjugated linoleic acid (CLA), which has been shown to be a potent anticarcinogen. Concentrations of CLA were 80% higher in pasture-fed cattle compared to the confinement-fed cattle. In addition concentrations of CLA were higher in Holsteins compared to Jerseys. To study the distribution of manure in a pasture-based system, pastured cows were observed for several 24-h periods. Data included: (1) times and location of all feces and urine events from eight cows, observed while in the pasture, feed area, milking parlor or in transit; and (2) all urine and feces events on pasture for all 36 cows each grazing period. The locations of urine and feces events were surveyed, mapped and analyzed. Percentages of the manure events in each area were highly correlated with time spent in each area (r= .99). Feces and urine (estimated at .12 m2 and .36 m2, respectively) from six observational periods covered 10% of the total paddock. Within 30 m2 of the portable waterer and gate, concentrations of feces and urine from the warm season observations were significantly greater than concentrations during the cool season observations. Manure on pasture was relatively evenly distributed over multiple grazing periods with the exception of the area around the water tank during summer grazings. These experiments showed that when compared to confinement-fed cattle, pasture-fed cattle produced less milk, produced more conjugated linoleic acid, had less mastitis and had lower body condition scores, while reproductive performance did not differ between the two groups. Jerseys had less mastitis, produced less conjugated linoleic acid, and performed better reproductively when compared to Holstein cattle. In addition, pasture-fed Jersey cattle can consume as much supplemental grain in certain time frames as pasture-fed Holstein cattle. Manure distribution on a pasture-based system is highly correlated with time spent in an area and is fairly evenly distributed over the paddock area over multiple grazing periods except for the area around the water tank during heat stress temperatures.
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MS
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Animal Science
