Is it true that Minhag Chabad is to refrain from eating meat even after making a Siyum during the 9 days?
I have not heard of such a Minhag as an official Chabad Minhag.
In Sefer Haminhagim it relates:
כ”ק אדמו”ר (מהרש”ב) נ”ע הי’ נוהג לעשות סיומים בט’ ימים שבין ר”ח לט’ באב אף שלא היה סועד אח״כ בבשר ויין.
In the English translation:
The Rebbe Rashab used to time the festive conclusion of his study of various Talmudic tractates to coincide with the Nine Days from Rosh Chodesh Menachem Av until Tishah BeAv. The meal that honored each such Siyum, however, included neither wine nor meat.
It’s possible that people understand from the translation as to say that the Rebbe Rashab was makpid that although he made a siyum he nevertheless did not eat meat. However, from the simple understanding of the Hebrew text, it doesn’t seem to imply that. Rather he made a siyum even though he had no intention of eating meat.
Furthermore, there are numerous times the Rebbe quoted this custom and on (at least) one occasion explained the basis for the custom.
In שיחות קודש תש”מ ש”פ דברים סעי’ צג the Rebbe says that the Rebbe Rashab needed for health reasons to eat chicken once every few days (including at least once in the nine days) and in order to eat chicken, he made a siyum on all of the nine days. The Rebbe then goes on to ask if the Rebbe Rashab only needed to eat chicken one day why did he have to make a siyum every day? The Rebbe answers because he didn’t want to use the Torah as something to use for his own physical benefit. In other words, he didn’t want to make a siyum in order to eat chicken – even if needed for health reasons. This way since he made a siyum every day it’s not noticeable that it was so he can eat chicken on that one day.
Also interesting to note from תו”מ ש”פ פנחס תשמ”ה (page 2648) where the Rebbe mentions
ומכיון שעושים סיום מסכת – יכולים לעשות סעודת מצוה ולאכול בשר ולשתות יין. וכפי שכבר נהגו בכמה מקומות לעשות סיומים ולקשר זאת עם סעודת מצוה עד לאכילת בשר כו’.
Thus, there is no official minhag not to eat meat. At the same time, the purpose of the siyum is not in order to have meat. Nor was that the intention of the Rebbe’s horaah to make siyumim every day. Perhaps, that’s the reason why a custom developed not to serve meat at siyumim other than where necessary.
Additionally, when it comes to eating meat, there are certain restrictions as to what constitutes a siyum, and whether it’s permitted to schedule it deliberately for the nine days, as well as restrictions on who can attend a siyum with meat. For all these reasons, many are accustomed not to serve meat and such occasions.
בספר המנהגים מובא שעשה סיום אף שלא היה סועד בבשר. ולא שלא אכל בשר. ונתבאר בשיחת ש״פ דברים תש״מ הטעם. ועד״ז בכ״מ. וראה שיחת ש״פ פינחס תשמ״ה, ובנוגע לסיום ספר (אחד של ה)הרמב״ם. וראה שיחת ש״פ מטו״מ תש״מ. ש״פ מטו״מ תשמ״ג. לקו״ש כג ע׳ 223. כח ע׳ 287 הע׳ 69-72. יח ע׳ 316. כט ע׳ 250. סה״ש תנש״א ב ע׳ 708. ש״פ מטו״מ תשמ״ז בלתי מוגה. ועוד. וראה ההודעה לציבור מתשל״ה – התקשרות שסה. וראה תשורה רבינוביץ סיון תשס״ד ע׳ 17. וכן נהגו בתשל״ה ב770, בשתיית יין, ראה בית משיח דברים תשנ״ח. קובץ אהלי תורה דברים תשנ״ח.