Stocks making the biggest moves midday: Berkshire Hathaway, Catalent, Tyson Foods, Zscaler and more

Check out the companies making headlines in midday trading.

Berkshire Hathaway — The conglomerate's A shares rose more than 1% as investors cheered a strong earnings report from Warren Buffett's company. On Saturday, Berkshire reported a 12.6% jump in operating earnings in the first quarter, driven by a rebound in the conglomerate's insurance business. The stock briefly topped $500,000 apiece Monday.

Catalent — Catalent shares plunged 25.9% after the company said it will delay the release of its fiscal third-quarter results and expects significant cuts to its 2023 guidance.

Tyson Foods — Shares plummeted 16.4% after the food production company posted an unexpected loss for the recent quarter and cut its revenue outlook for the year. Tyson Foods now said it anticipates between $53 billion and $54 billion in revenue for the year.

Zscaler — The cloud security stock rallied 20.6% on strong preliminary earnings and full-year guidance. Preliminary revenue, non-GAAP operating income and billings for the company's third quarter all came in above respective consensus estimates of analysts polled by FactSet. The company also raised its full-year guidance.

Occidental Petroleum — The energy stock fell nearly 3% after Warren Buffett knocked down speculation that Berkshire Hathaway would take full control of the oil giant. He said he doesn't know what Berkshire would do with it. The "Oracle of Omaha" has amassed a stake of 23.5%, while receiving approval to purchase up to 50% of the company.

PacWest - The regional bank stock held on to a gain of about 3.7% on Monday. Shares opened nearly 30% higher after PacWest slashed its dividend but said its business was still "fundamentally sound." Other regional bank stocks also gave up some early gains, with Western Alliance up less than 1% despite being reiterated as a buy at Janney.

Six Flags — Six Flags jumped 18.6% after the regional theme park company surpassed first-quarter analysts' expectations. Six Flags posted a narrower-than-expected loss of 84 cents per share, compared to expectations of a per-share loss of 89 cents, according to FactSet. Six Flags posted revenue of $142.2 million, greater than the expectation of $132.6 million, with CEO Selim Bassoul calling the results "proof points" that its new strategy is working.

American Airlines — Shares jumped 3.5% after JPMorgan upgraded the stock to overweight from neutral. The firm cited American's improving balance sheet and exposure to international travel as upsides, amid a long-term shift favoring "the Big 3" airlines — American, Delta and United — over discount carriers.

Viatris — Shares gained nearly 6% after the pharmaceutical company beat earnings expectations and reaffirmed full-year guidance, helping investors overlook underwhelming revenue. Viatris posted $932.9 million in adjusted net income for the first quarter, beating the consensus estimate of $835.8 million from analysts polled by FactSet. But revenue came in at $3.72 billion, falling short of the $3.8 billion forecast from Wall Street.

AMC Entertainment — The movie theater chain and meme stock favorite added 0.2%. The company announced over the weekend that it reached an agreement to settle a class-action lawsuit with shareholders over a proposed conversion of AMC Preferred Equity Units to common company shares.

Fortinet — Shares of the cybersecurity company gained 2.3% as Bank of America upgraded shares to buy. The bank cited the company's "strong fundamentals" following its latest quarterly report, in addition to a "substantial price advantage over competition." Fortinet's stock has soared almost 35% year to date.

Scotts Miracle-Gro — Shares popped more than 9% after JPMorgan upgraded the fertilizer company to overweight from neutral. The bank called the stocks a "very reasonable investments" at current levels.

— CNBC's Hakyung Kim, Alex Harring, Yun Li, Michelle Fox, Sarah Min, Brian Evans and Jesse Pound contributed reporting